BlackStar HT5R Repair // How to debug, fix, mod and test this common issue with these amps!
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- Опубликовано: 26 июн 2020
- Blackstar HT5R tube amplifier repair.
The known and common issue with these amplifiers revolves around two transistors (TR2 & TR3) and the two resistor (R38 & R39)
Schematic: drive.google.com/file/d/1GkFa...
If there is not catastrophic failure, the easy repair is to:
- drill out the transistor traces,
- replace the 2 resistors,
- reflow all the solder joints around this area,
- add heat sinks,
- new power tube (12BH7)
- balance and bias the power tube.
If your PCB is toast, you could re-use the parts to make something like this: • Making a 1 WATT TUBE A...
Please check out my tube amp playlist on how to make and tube amp discharge tool and current sink.
Hakko Solder Station: amzn.to/3PvQaD7
Kester Solder: amzn.to/3aJKNBI
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Love the video. A bit over my head but your explanation gave me a good understanding of what you were saying. Keep up the good work.
thank you for sharing your story and your advice. I replaced the fet's, resistors and tubes. Cleaned the tube sockets with the original tubes and contact cleaner. Working now as good as new. My voltage metered at 22.9 and 23.0 volts on the test points. Thank goodness I didn't need to tweak my balance adjustment. I got some tiny clippers in there and carefully cut the leg off the resistor right where it meets the resistor body. The solder sucker pulled it from the PC board. The resistor and the other leg fell right out the other side. Worked so well I cut the legs one by one on the old fet's . Solder sucker removed those cut legs as well. BIG THANKS !!!
Thanks for commenting. Glad my video helped you out. Hopefully you installed the heat sinks as well to stop this issue from happening again. Cheers.
Hi Mike, thank you very much for this video - very informative! I have a new and only tested HT-5R and will now, as a precaution, make the modifications you have described. I will also at the same time replace the speaker in the cabinet with a much better sounding Celestion G12M Greenback, 16 Ohm. All of this will make this little buddy a real hit. Thanks so much for your advice and guidance, it's much appreciated - awesome! 🙏👍🤗🎸
Thanks for commenting. A speaker swap is a great idea for these little amps… however you want to make sure you get a low watt version. Since these are low watt amps, it would sounds better if you can push the speaker a bit.
This is a great video. Thanks for the help!
Had this exact problem, diagnosed thanks to this video. Was about to throw the amp out. Cut about a 4" diameter hole in the back and installed a small fan. Problem completely solved. Thanks!
Interesting. I wouldn’t think that would do the trick. I’d probably install a heat sink on the transistor as well just to be safe. Cheers.
Thought this was my issue because R10 was literally smoking, so I checked the same areas. All looked okay, transistors checked ok, so I looked a little deeper. D34 was shorted and slightly burned, it is a 1N4007. Goes from R10 to ground. Replaced that, R10/38/39 and the transistors (adding heat sinks) as I was worried about possible heat damage to the transistors and R38/39. While I’m in the amp might as well replace them in case they suffered some fatigue. Thanks for the heads up because it indirectly led me to the solution and also brought to light an issue I wasn’t aware of, which may have saved my buddy some additional work down the road.
Thanks man . I have a heat problem with my ht5r head .gives little smell as well
Great video! That's a fair amount of work to have to perform on a new amp. It's a reason I've stayed away from the HT5s (and Marshall DSLs).
Thank you. Yes, these amps have a lot of circuitry that can easily go bad and ruin an amp. Old school point to point seems to be the trick.
You are a blessing!
great video Mike, you make teaching a pleasure to listen to. But you've made me think twice about buying this backstar
Thank you for your comment. The amp itself sounds okay for what it is. The board issues are the inherent problem that once remedied makes it somewhat reliable. This led me to making a simplistic version (my one watt Princeton). Please have a look at my build video if you haven’t already.
Very useful to me!
I have this exact amp and it does everything that you say.
I was thinking about selling it or change the tubes but now I don't really know what to do, since I don't have the tools to fix it.
Thanks for the video, I'll never buy amps again, I'm sticking to studio monitors and software to play guitar.
Thanks for commenting. Sorry to hear that. All you really need is a soldering Iron and a cheap drill to fix it. I suspect for under $75 you can easily fix this amp. New power tube (12BH7) woudl be a good idea as well. I believe amps from are larger company (Like Marshall, Fender, VOX..etc..) tend to have a better life span. This Blackstar has an inherent flaw. Cheers
Thanks for the video.
You’re welcome. Thanks for commenting.
I haven’t had issues with my blackstars yet. I also have a 100 watt Marshall that sounds awesome .
I have often wondered if one could essentially get the main distortion tone from blackstar from a custom build .
I never use my club 40s second distortion channel, I stay on the first , ideally I’d want that sound of the first gain circuit with the “isf” feature with the ability to keep it more open at certain settings , like a responsive marshall.
Blackstars can get a pretty nice sound for sure .
Thanks for your comment. I’m not sure this possible. There is so much circuitry in these amps that you would need to be a electrical engineer or technician to make it work.
You “could” gut the entire circuit board and redo the entire amp point-to-point following a proven layout and schematic. Big task though but at least you would have all the major components like the PT, OT, Tubes, chassis. I was actually thinking of getting a reissue of a deluxe reverb and rewire it to 60’s spec.
Excellent THANKS
You’re welcome. I hope it helps you out. Cheers.
Very good video, I have a HT 20 mk11 that turns on but the output sound has stopped working , however it does work in the emulated output with headphones, thought it might be a tube,this video was definitely helpful, but beyond my skill set, a little disappointed with Blackstar, because I like the amp but Im seeing a lot of problems with these amps in the forums too bad …
Thanks for your comment. Yes, they do sound okay but it is too bad they they have odd issues with the circuit.
Thanks for the video! Sorry to say, but i have a same problem. Sound disappeard and there is fuzzy burning_like sound. Called to repairman and he said -i can look it, 90 euros/hour. Hope it doesn't take too many hours :)
Sorry to hear that. It is a common issue with these amps. The amp can be saved if nothing catastrophic has happened to the board and components. Mention my video to the repairman. It may help him solve the issue. Good luck!
I had that problem with my blackstar I Sent it back ,and I had a bit of hassle getting a refund but I did .I then bought another HT5 and the same thing happened,this time I took it to a technician who fixed it and it has been fine since .
Thanks for commenting. Glad you got it sorted out. It is an inherent flaw with this amp. You are brave to get another one. I probably would have walked away and gone with something else. Cheers.
Excellent video for learning
i have a blackstar club 40 mkll, it has an issue whit one DPDT switch, Can i replace this type of switch whit a on/off mini switch?
Unfortunately I’m not familiar with that amp, however, I would try to determine why it doesn’t work. Is the switch itself faulty or is the circuit? I would try to inspect the switch ( cracked, broken...). Perhaps spray some contact spray into the switch itself. If it’s a multi position switch, it would require some effort to wire in a new switch that is stood-off from the circuit board. The circuit board itself may be difficult to solder and figure out the traces. Not sure I would attempt that myself. If the switch is faulty, I would try to replace that exact switch.
Great video. I was considering buying this amp since it is such a feature rich amp, but I think I'll just keep looking. No sense in buying a piece of crap.
Thanks. I believe the newer ones have less issues and behave better but its hard to know for sure what you are getting. It's not like the store will allow you to take the amp apart to look at the circuit board. lol Cheers!
Great video Mike, mate that amp has a major engineering flaw! To have to do what you did ( especially adding the heatsinks to the MOSFETS ) shouldn't have to be done if they designed it right. I've tested out blackstar amps in my local music shop but never sounded like Marshall like they say they do. O heard somewhere that the designer for blackstar use to work for Marshall! On a side note I hate PCBs 😂
Thank you. Once “fixed” it works okay.
even marshall have problems like the dsl2000 drifting bias will destroy the board they sell new boards for $200 with fixed bias drift lol
Brilliant english, pleasure to hear, where are u from?
Really helpful to know this. Apart from from solving the problem, it also leads me to a prevention strategy - I won't be buying a Blackstar.
Yes, unfortunately. I do like a few tones this amp can produce which led me to make a simplified version of this amp… my one watt Princeton. Please have a look at my build series.
Very helpful video, on mouser they have several different types of irf830 with different letters after the numbers. Which should I buy for the ht5r? I'll be replacing the resistors too and adding heatsinks. Any advice would be much appreciated.
Hard to say... the best thing to do is read what the numbers of your existing transistors, search for that spec sheet and compare what has similar specs.
Hi Mike, thanks for the video! This seems to describe the exact issue my amp has. I have made a few guitar pedals so I have the skills to make the changes you have described, however I am worried about the high voltages and don't know how to discharge the capacitors. If I leave the amp unplugged for an extended period of time, let's say one week, would it discharge itself and be safe to work on and touch anywhere on the circuit board?
Thanks for your comment. I would use a Multi-meter to confirm voltages. These circuits typically have a bleeder resistor but you should always confirm first. I have a playlist on making a drain tool and how to use it. Always measure and/or drain the capacitors before doing any work. Never assume. Cheers.
by listening really carefully you can balance it without measuring the test points when it's unbalanced you can hear a hum in the speaker
Hi, great video and explanation. Can I ask how did you removed the chassis (amp) from the cabinet? Is it possible to separate the two just by disconnecting some cables or you had to use the soldering iron?
What actually keeps the chassis attached to the speaker and what do I have to do to divide the two
The Chassis just unblots from the Cabinet. To flip PCB over from the chassis, you need to unbolt all the potentiometer and unclip the cables and unscrew the PCB. To remove the PCB all together, that's a bigger job. Not sure on the amp revision you have, but you may need to unsolder a few wires.
@@MikeFreda thank you for your answer, that was really helpful. I was wondering if these blackstar combos had the capability to just umplug the speaker from the chassis. If not, what did you had to do in order to separate the speaker from the chassis?
Hi Mike! Thank's! I did this procedure and it really worked! I assembled an external PCB with a heatsink and a cooler, and moved the components to this PCB, it's very good now. But I have the other problem, when I'm on the clean channel and I play a little louder, it switches to the drive channel by itself. Do you know what it could be? Greetings from Brazil
Thanks for commenting. I have no clue why it would automatically switch other than a faulty switch and the vibration is making it switch. Very odd. Cheers.
@@MikeFreda Thanks!! To do a test here, I turned on the footswitch and the problem stopped. When I remove the footswitch it returns to the problem. It could be some component with current leakage and for some reason the footswitch circuit must be absorbing it.
Hi Mike, thanks for this very helpful video. I don't understand why you drilled out the traces to the transister to prevent current leakage and am afraid to do that step because I'm unsure how to do it correctly. Did you desolder the transister first? Do you resolder after the holes are there?
You're welcome. It's been discovered that at the base of the transistor the Circuit Board is able to conduct a small trace of voltage and/or current. This upsets the bias and the operating parameters of the transistors. Drilling small holes creates an "air gap" thus mitigating this issue. I did not de-solder the transistors. I just used a very small drill bit and went really slow.
@@MikeFreda Thanks! Super clear now.
Great Video! do you have the schematics for this exact amp? I can't find it online. The only on that pops up is the HT5 sheets, but they are a bit different.
I found the schematic in Amp forum. I’ll see if I can find it again. It’s a confusing schematic to follow.
Great video. I have an older Blackstar, the HT20 Mk.1 - I'm reluctant to run it often and am considering selling it as it has some of the same problems associated with the later HT series.
Have you ever checked out the HT20 Mk.1 (aka "HT20 Studio") head?
Nothing has gone wrong with the amp - yet.
No, I have not. To be honest, most of the music stores in my area don’t carry or stopped carrying them. Haven’t seem a lot of these amps.
Hey Mike. Great video. I'm doing this to my amp at this moment. I have to ask you what difference does it make if I use the same heatsinks or replace them with new ones?
Thank you! Sorry, I guess it wasn't too clear in the video. The amp never came with heat sinks on the transistors. I installed new ones on the transistors. If the transistors still function you may be able to get away with just drilling holes between the transistors, re-flowing the solder joints on everything, installing heat sinks and installing a new power tube. The heat sinks help dissipate the extreme heat the transistors generate. I had these ones in my parts bin. You may be able to install smaller ones if you want. I do believe theses transistors need something.
@@MikeFreda Thanks this helps a lot! I bought mine as used and turns out that the previous owner did install those heat sinks. So at some point they had same problems with this amp.. There was no holes drilled between, so this must be an older one right? I did every step you showed, but my amp is still acting funny. The sound does not go away or anything, but its distorted and buzzing, very flat sounding.. and it goes hand by hand with the volume/gain. Do you know if this might be capacitor related or something?
btw subbed!
@@PenZEdits Hard for me o say what it could be. As you can see, there are a lot of components on that board. You may want to check out the resistors values to see if they are still in spec. The ones around the two transistors. (You will need a ohm meter) If the resistors get too hot they go out of tolerance thus effecting the operating parameters of the transistors. Hopefully you put a new tube in!? I would also verify all the voltages from the test points. If that all checks out, your transistors (and possibly your resistors) may need to replaced.
Thanks , excellent detailing .
Regarding the high voltage capacitors, can you discharge radial caps on pcb without flipping them ?
If not , is it safe to touch the edges of the pcb ?
I'm asking because all demos on youtube are done on axial caps, which are easy to access .
Thank you :)
It does make it a bit harder. Sometimes there are resistors that are mounted on the top of the PCB right next to the cap that you can access an exposed lead. Depending which side of the resistor you touch, you may need to hold the prob longer. Always use a Multi-Meter to confirm voltage after. I'd recommend draining caps before removing/touching the board with two hands. Cheers
Mine melted the resistors and burned out the pcb board and one of the capacitors. I drilled out the pcb around the FETs and recreated the circuit on a small pcb, mounted it in a tiny free space on the chassis and jumpered it back onto the main board.
Thats an ingenious work around. Thanks for sharing. That must have been some effort figuring that all out!?
@@MikeFreda I used a schematic floating around on the Internet. I actually had to do it twice. The first time I replaced components on the board and used some jumpers to get around burnt traces. However even with the holes between the FETs, the pcb still conducted and it failed again. I gave it one last chance by using a small pcb and standoffs off to the side. I added heat sinks too but don’t think they’re necessary when you move the location of the FETs as there are no longer any tiny components near them.
It was way more work to salvage it than the value of the amp, but it was a good skill building experience. I just didn’t want to throw away an otherwise fine combo. It works fine now except recently the reverb stopped working…. Ugh.
Hi Mike - great video - I wish I'd seen this sooner - I have a Blackstar HT5 with exactly the issue you described. I had already narrowed things down to the FET transistors and fitted new ones accordingly (Although I didn't fit heat syncs, drill out between the contacts or replace the resistors) - I also swapped out both valves for new ones. All seemed fine for about 5 minutes, and then the output valve (12BH7) lit up like a christmas tree and fizzled out, as did all sound. I now get power up only, but no output volume at all. Could my problem be related to your fix? If I swap out the FETs for more new ones and replace the resistors and drill out between the contacts do you think I'll get any joy, or has something more catastrophic happened do you think?
PS: I have fitted another 12BH7 valve, which seems to be operational, but nothing is happening-...
Thanks for the comments! It's really hard to say what else on the printed circuit board has been compromised. At this stage I would check voltages and resistances. See if the speaker is good, the output transformer are good. All the fuses are still intact...etc. Basic Tube amp trouble-shooting. Remember, there is high voltages in here. When checking resistances, drain the caps. Replacing components may work.. but you could also be chasing your tail if the circuit traces are baked. Hope you figure it out!
First, thanks for your video and taking the time to share and help. I have an HT CLUB40 combo that had similar symptoms with the difference that after a couple of times working 30 min before going dead (no sound at all) now it doesn't make any sound when turning it ON. The 2 preamp tubes glow but the 2 power EL34 tubes don't. I see a similar structure in the board regarding the 2 FETs and the resistors you changed in the HT5, probably different parameters but similar architecture. I already tried resoldering the tubes' contacts to assess for a cracked joint but didn't work. Do you think changing the 2 resistors and transistors and putting heat sinks could work here too?. You said at some point "You don't want them to fail completely" .....in my case I believe they did. Aside from having dead components that need to be replaced...is there any another concern I should be aware from these elements having failed completely? Thanks!
You're welcome. Unfortunately, I'm not familiar with that amplifier/circuit. Very hard for me to say what your issue could be. Tubes "glowing" is the function of the filament circuit. Pins 2&7 on the EL34's should read 6.3volts. Unless the bias circuit faulted and destroyed the tubes, the only way of knowing is by getting the schematic, new power tubes and testing voltages. At that point, I'd recommend taking it into a qualified Amp Tech.
@@MikeFreda Hi Mike!, yeah with the tubes glow I wanted to say "at least there is some current going thru those tubes". Well thanks anyway. If I manage to fix it and identify the issue I'll post it here as there are other HT owners that may be in the same situation. Take care!
Hello Mike, very interesting!! I have ht-1 that just replaced both the tubes, do i need to rebias the amp? If so how can i determine the correct value
Thanks
It is a good idea to check and/or re-bias a power tube whenever you install new power tubes. In these amps it’s not as critical however for max efficiency you should balance the triodes in the 12BH7. Just adjust the trim pot till they are the same voltage. For biasing, I would stay under (at least 80%) of what the tube manufacturers say the tube can be at. Check the spec sheet of the 12BH7.
Hi Mike, Thanks for your investigation and description of this problem and fix. Unfortunately, I don't have your skill set to care for a good-sounding but "needy" amp like this. The Bugera g5 infinium is considered a clone of some of the HT mkii series. I'm wondering if you have encountered this amp in your repair activity, and what you think of it as an alternative to the HT series? Bugera does not have a service centre in BC, and I live in a little northwest BC town- if I bought one and it needed repairs later on, would you consider working on it? Or have a recommendation for BC repairs? thanks, scott
Hello Scott, thanks for commenting. This Blackstar is a versatile amp and does sound okay. I do believe the new ones have been sorted out. I'm not familiar with this Bugera amp. The Fender Bassbreaker 15, Pro Jr and Blues Jr is something similar to these amps. They sound pretty good for what they are. Like anything, buying amps used is a bit of a crap shoot. Buying new from a shop may be your best interest for returns/repairs. Repairing Tube Amps is becoming a dying skill set. I only know 2 people in the lower mainland that do and they are very busy and charge a lot. This is part of the reason why I do my tube amp videos, to share my knowledge and to help people out in the future. Cheers.
The Bugera G5 suffers from the same design flaw of the phase inverter. I just drilled out the 2 MOSFETs but it's much harder on the Bugera since there is almost no space between the pins. Afaik there are no test points because of the Infinium auto bias thing they have built into it.
Hi, the 2 transistors did you use STK830 or IRF830's there both the same but the IRF830 i cant seem to find 220 type with plastic casing witch did you use and where did you get yours ?
I’m not familiar with that mosfet. Mouser sells the IFR830. That being said, Whatever is in your amp is what I would replace with new (like for like) and add the heat sinks.
I have a ht5 head from 2012 that has no sound at all on the clean channel but when I engage the overdrive channel it plays like a clean channel with no distortion at all, can you recommend what it might be? I replaced both tubes so that’s not it
That’s unfortunate. I don’t think that’s a tube issues. Seem like something is wrong with that portion of the circuit board. Does is work okay using the headphones?
Thanks for this? What is the typical cost to do this type of repair? Not sure exactly what is wrong with my amp, but it makes crackle like noises.
For me, I just had to buy a new tube. I had the rest of the parts in my parts bin. If you needed to take it to a proper amp tech, I'm sure the minimum charge would be at least $100.00. As for crackling noises, that could be anything from a bad tube, bad solder joint, dirty pot, bad jacks, bad speaker, loose connections... etc. who really know over the internet. Good luck!
Hello Mike, I live in France, so excuse me if I make some mistakes in writing. Does the same problem exist on the HT-5RH?
When I last used my amp on the 'Clean' channel, it ran great for a minute, then the sound cut out and I only had a loud hum. Switching the amp on the "Overdrive" channel, the amp works perfectly. Is there a relation between what I explain and the problem you present in this excellent video?
Thank you in advance for your help.
Thanks for commenting and asking a question. The issue I fixed I based around the bias of the output tube. That tube feeds the output transformer and the speaker. I found that it didn’t matter what channel was being played through it still acted up.
I did find that the line out or headphone out was not effected. It’s hard to say what your issue is other than turning it on and testing voltages. Cheers.
Hi, thanks for making this video, very much appreciated. I'm wondering if my HT5R has the same problem, when the speaker cab is plugged in to the 16 ohm single speaker port there is an occasional very soft and faint random static noise. however if i plug in the headphones it seems to work fine perhaps the max volume isnt deafening but it's certainly loud, the tubes heat up and start glowing and if i try the speaker cab on the headphones outlet it works also at a low volume, perhaps to be expected? So the speaker out channel doesnt seem to be working is that what those MOSFETs control? if not would you have any idea where I should begin looking to find the fault? kind regards
Those Mosfets are on the output section of the amp. The emulator section of the amp seems to bypass that section. What you are describing sounds typical of what the issue is. The only way to know for sure is to open the amp and have, inspect and takes some voltage readings. The amp does have high voltage in it. You may want to have an amp tech look at it for you.
@@MikeFreda thanks, since I asked the question I have done a bit more investigating and inspected the output transformer, do you know what resistance values i should be getting across the coils (red to black wires)? I measured 1ohm on the input and 0.884KOhms on the output.
It’s are to measure the primary side of the OT is still wired up. From the CT to one leg you may see around 150ohms. Secondary seems right. Anywhere from 0.3ohms to 1.5ohms on the different taps is what you typically see. When a OT faults, it normally faults as a open circuit and you would get infinite reading. Since you are hearing a sound the OT appears to be functioning.
@@MikeFreda thanks, I desoldered the two identical MOSFETS from the circuitboard and tested them on a multimeter one of them charged up to about 2.2 v the other to 0.65v so they at least one of them is at least part of the problem.
Hello there great repair, I have the opposite problem, switch on the amp wait 30sec then switch on standby, I get no sound ( no hum buzz nothing).Plug in headphones everything is working fine and sounds great. I leave the amp with power on but standby off, wait about 10mins and try again. Start to hear some distorted sound on the clean channel. The long I leave it on the better and clearer the sound becomes until after a few minutes its sounding how it should. After playing for 20mins I switch it off and leave it for a few minutes and whole process starts again. won't come back on. Will this repair fix my problem too even though its the opposite? I have changed tubes also which makes no difference. Thanks
That is very odd issue. It would appear to me to be a heat related. Since most of these amps can have issues it may be a good idea to try my fix…. However, without seeing and testing the amp it really hard to say what your specific issue is. Cheers.
@@MikeFreda I will give it a go, first. Thank you
Hello, what a good video, I would like to ask what is the voltage of the transformers? Regards :)
Thanks for commenting. I can’t find my notes and I can’t recall off the top of my head. It was several years ago when I fixed that amp. This amp has a complicated PSU. 12BH7’s as power tubes typically want to see around 300vdc at the plates. Depending how it’s biased, this amp will draw under 40ma. Cheers.
@@MikeFreda thx :)
Hi Mike. Do you have the electronic schematic to share, or a link to download it? Thank you
I downloaded from the net. Shoot me an email and I can send it to you. It is a complicated schematic due to all the solid state components in this amp.
Do you know if this is similar with the OG non-Reverb HT-5? Mine loses volume ( I have not tried to check the emulated output though) completely after a while and switching tubes did not seem to work. This video makes this seem do-able for me but I was just wondering if the old ones are kind of the same :)
Thanks for commenting. I do believe that amp had the same issue. Cheers.
I have a HT-5 that also loses volume after a while, I changed various things but not fixed it yet, did you find a fix for this?
Hi Mike, I have the HT5 Metal head and yesterday on the gain channel it sounded as if my highs and mids had disappeared, similar to someone putting a duvet or two over the cabinet. I cranked them up, and then they still faded.
I switched the Pre amp tube, and it now sounds fine, however someone on a forum said it is unlikely to be the tube and it could possibly be this.
The amp sounds fine now with the new pre amp tube, so could it really be this issue or was it just a failed tube? I have owned and used the amp since the HT5 metal was released, so I would say 8 years of use?
Thanks for commenting. Very interesting issue you have. The issue in this video typically effects the bias of the power tube (12BH7). Without testing voltages it’s hard to say what is going on in your amp. 12AX7 tubes last a very long time. Unless your amp was left on for weeks/months at a time it should last many years before it will fail. These amps run the power tube a lot harder so you may want to replace that tune as well. That being said, could be a bad tube as well. I’d date it and keep track of run time. Cheers.
I have an older version of the HT5 and just did this repair. The board does not have dedicated Test Points for balance and bias The schematic doesn’t show any either. I see the pots with adjustable screws for adjustment. What do I need to measure across for the balance operation, and bias? Thanks
I'm not familiar with that particular model but you basically want to measure the Plate, Cathode and the grid voltages on each half of the 12BH7. On the first triode, pin 1 is the plate and pin 3 is the cathode. On the second half, pin 6 is the plate and pin 8 is the cathode. The cathodes are joined together with one bias resistor so their voltages should be the same. You can measure the plate voltages to see if they are similar. The Test Points are actually measuring the grids, Pins 2 & 7. You adjust the balance pot until the Grid voltages and plate voltages are the close to each other. I doubt you can get them exactly the same since each triode are typically not 100% identical. I hope that helps? Cheers
@@MikeFreda Thanks a lot for the explanation! Much appreciated.
Hi, I have a Blackstar HT1h that powers on but when you plug guitar cable or headphones you get no output, any common fault with this type of amplifier head.
Hello, hearing nothing is typically not a good sign. If you are not into electronics or worked on amps before probably not a good idea to poke around in there. These amps have lethal voltages. That being said, I'd first see if the amp actually turns on and the fuses are all good. I think there was a fuse inside these amps as well. I would reset the tubes by pulling them out and resetting them in the sockets a few times. Look at the tube are they clear? are they white? (If they are white, they are bad) if not, turn the amp on and look to see if the tubes light up.
Other than pulling the chassis and looking for loose wires and any burnt components it's really hard to say what could be wrong. There is a lot of circuitry in these amps. Best to take it in.
im getting the feeling i shouldnt buy this amp..is the mark2 improved or does it still shit the bed like this model..what amp should i get for home use..but low low low volume with good quality sound..im looking at the mark 2 because it has 0.5w mode
I’m not sure if the Mk2 has dealt with these issues. Best to check the BlackStar amp forum. The small fenders seem to be reliable. Blues JR and Pro JR have a lot of tonal variety.
I make my own amps from scratch so I’m not really up on what is currently available for lower power practice amps.
Is this also a recurring problem on the mk2?
Sorry, I'm not aware if they corrected all the issues. I do know that did eventually drill holes between the transistor traces to help cure some of the leakage issues.
@UCrbD5DfW1Nimq13LLbdL_EA Sorry, I'm not 100% sure. The Mk2 came out in 2019. The amp I worked on was several years older than that so I suspect it was a Mk1. From what I gathered, they made minor circuit board changes throughout the production runs. That being said, I have no idea if all these issues have been corrected on the Mk2. Best to check the Blackstar forum.
hi Mike, thank you for the video :) do you happen to know if the MKii revision has this issue?
having tried a number of amps before the pandemic, I'm thinking of maybe buying one soon. I don't need it, but it has a lot of handy features, and I know I really like the clean and distortion channels from having played the original version a number of times in shops. tempted by that sweet, warm, lovely distortion sound!
I would need the MKii revision. I've never owned a tube amp due to my living situation, where I am going to be practicing relatively quietly in my bedroom. if I were to get one, which is absolutely not a need, and more of a want... it needs to have that power reduction feature to ~0.5W, plus they seem to have added other cool stuff to the revision. :)
Thanks. I believe the newer ones have less issues and behave better than the older models... but I'm not really sure if they sorted it out 100%. I do believe they are aware of the issues. Yes, this amp is a "tube" amp but I would use that term loosely. There is so much solid state in this amp that I'm not sure if the brand of tube makes that much a difference in this amp. Yes, a lot of versatility in this amp, it does sound good at low volume but a far cry from a 50-60's tube amp. As for bedroom listening, you could just get an attenuator (or make one) and use any lower power tube amp you want. I've done this and it works pretty good. I hope that helps!?
@@MikeFreda that does help :) thanks for the info! I never thought of trying to make an attenuator, as I assumed those were fairly complicated devices?
never had a separate head and cab combo either, and while I have read a little and know some basics (like matching the impedance of the speaker cab with the output appropriately). beyond that, I mostly scratch my head in confusion, not having the requisite experience.
I enjoy tinkering with the various inexpensive guitars I have, so I could see wiring up some more basic circuits for some pedals or simpler tube circuits could be fun.
debating in my head if I should just go with something that "just works" so I focus more on practicing, or if I'll go down the rabbit hole of tinkering and fiddling. there's so much out there, and it's pretty fascinating stuff!
My headphones won’t work in my ht5, the sound comes out of the speakers instead of the phones, I’ve tried three sets and they work in other amps , any ideas ?
Interesting. I have not heard that before. All I can recommend is seeing if the headphones actually work. See if the Jack is not broken or the board is cracked. That can be an issue. They are inexpensive and can fail. Other than that, I have no idea what it could be. Cheers.
@@MikeFreda cheers for your reply,headphones work fine in my other amp , I’ve tried three sets , none work properly
i do have exactly same problem. so i can find 2w 22k resistance but i can not find 2w 22k so is there any other alternatif for this aplication?
Not really. Try Mouser: www.mouser.com/
While you are at it, get some heatsinks.
@@MikeFreda what abouth mosfet. orginal mosfets are auk stk830. but i see that you have used irf 830. so i found stk 830 mosfest your set up shoul be used with irf 830. or can i still use stk 830 with your residnece set up?
@@MikeFreda by the way i do live in Turkey so most probably i ll buy those residance over aliexpress
I stick what came with your board. I'm assuming different production runs use substitutes. You should be able to find a X-Ref for your STK830
Sad to hear that this is a known problem. I’ve had this amp on my want list. Is this a problem with the entire HT lineup?
I'm not aware if this is an issue on the entire HT lineup. This is the one and only BlackStar I have opened up and repaired. From what I gather, the "head" version and the "combo" version share the same board. Probably best to contact them directly.
My Ht1r mkii had the same issue out of the box :(
My 5ht r is sounding super muddy Even with a clean tone. Can't even play a chord.
Gonna replace the tubes and hope for the best.
Hi dude, have u replaced the tubes anytime?
What brand do u recommend? I got one HT5!
Tks and very good video! Piece
Unfortunately, there isn't a lot of selection of 12BH7. ELECTRO-HARMONIX and JJ's seem to be the most popular. You may be able to find some NOS treasures... but I think that would be a waste of money. Honestly, this amp has so much solid state components in it you would be very hard press to hear the difference between tubes. The 12BH7 is a robust tube and if the surrounding circuit stays within operating parameters you should be able to get years (8,000+hrs) of run time on them.
Thank you for ur inputs! Cya
I wonder if this issue was addressed on the MkII?
I'm not sure. I do know that some of the later boards they separated the traces between the transistors with larger holes but they did not add heat sinks or larger resistors.
I'm wondering the same, hopefully someone knows or can take a look inside the mark2
My Ht1r mkii had the same issue out of the box :(
Yes, same issue on the later boards, buy something else!
Anyone know if the mkii is the same design? I just bought a used one and 30 min into playing I had loss in gain. The OD channel sounded “clean” and muffled and clean channel was almost silent. I’m thinking I should return it rather than spend lord know how much money trying to figure this out
If you are able to return it, I would. They tried to “fix” other versions but for whatever reason they still have issues. That being said, if you can’t return it you may be able to just install the heat sink in the transistor. Cheers.
@@MikeFreda thanks for you input. I went ahead and put in refund request. Luckily seller is responsive and I hope believe all will turn out ok. It’s a real shame because I really enjoyed the low volume sound and simplicity of the amp. I did learn that I likely won’t buy another used tube amp as I’ll feel more comfortable with some warranty support. I got my eye on a Rocker 15 but wow it’s a price jump. Cheers and great video!
Hope it works out for you. I would use the term “tube amps” very loosely with these amps. There is so much solid state in these amps that they can easily replace the tubes with solid state devices that you probably would not notice the difference.
You can’t go wrong with a small tube amp like a Champ or Princeton. You can pick these up for people who made them from a kit. All the parts are readily available and lots of resources to help you out it you have an issue. Cheers.
@@MikeFreda Great info which I’ll keep in mind, thank you again 👍🏻
Is the Ht5 Metal the same ???
I’m not sure. You may want to download both schematics and check to see if they are similar. If it has a 12AX7 and 12BH7 tunes it may be. Cheers.
Yes it does have the same Tubes !!!
Are these amps a combination of tube and mosfet?
Yes/no. It uses a proper preamp tube and a 12BH7 as a power tube with a proper output transformer. The mosfets are part of circuit that biases/applies voltage to the tube and the emulation section. Technically you could rewire this amp to point to point removing all the solid state components but it would be a lot of work and would sound different.
So the post amp section is Solid State? I like this amp, I’m just unclear why... It’s weird to me
Not really. It goes Power tube, output transformer to speaker. The power mosfets set the operation the tube. The emulation section seem to be mostly solid state. Probably best if you found the schematic online and followed the signal chain. No clue why they do this. Easier to make for the multitude of tones and options you can get.
Hi, mosfet transistors are overheating. What is the reason?
Yes, the appear to be. When transistors overheat they are typically running to much current and can’t dissipate the heat effectively. One of the reason in this amp is how they are biased and it would appear that the how they are mounted in the circuit board the traces are too close to each other. Stray voltage is effecting the bias. I also think that they may be undersized for this task. Clearancing then traces and installing a heat sink seem to be a cure. Cheers.
Thanks
Didn't the designers think about this?
That's a great question. I suspect that a prototype is designed and made with certain parameters and variables and that passes. When they finally go to full production things are done to save money, steam line or parts are substituted and this is where the troubles arise. One would think that most components would be designed to handle 2-3x the dissipation required. Apparently not.
Mine just suddenly stopped emitting any sound whilst I was playing through it on the clean channel. Nothing. There's a very low level low pitched hum when on standby and/or on.
That sucks. Hard to say what the issue could be. If you can hear a hum, then the speaker and output transformer appears to be working. I’d try plugging into the headphones and see if that works. If that works then it may be the issue I discovered. Not sure the amp is worth taking to a amp tech. They will probably charge you more than it’s actually worth the fix. Good luck.
@Mike Freda thanks for the advice mate. Will give it a look but in all liklihood I'm gonna buy another amp. The amp was great but it doesn't suit my taste anymore anyways.
Did they fix this issue with the MKII?
I’m not 100% sure. I know on some later models they drilled holes between the mosfet traces but that alone is not enough. Your best bet is to look/search on a couple amp forums like ampage, Music Electronics forum or the gear page.. They are a pretty good resource.
No, I have the later version (with the slots already in the board) and it still has issues, buy something else!
@@pcb1962 What kind of issues? i'm on the brink of buying this amp, but this video make me think twice.
Where are you located
Near Vancouver, British Columbia, Canada.
Is this amp a mki or a mkii?
Unfortunately, I do not recall. The board itself seemed to be revised from the factory but I’m not sure what version it was.
Going by the control knobs and panel it looks like it's a MKI. The MarkII has beige/yellowish chicken knobs not chrome buttons
@@LiesThatBind Do you recon the mk2 would be prone to the same problem? I'm on the brink of buying one, but this video stalled me in my decision. Thanks!
@@ChristiaanBurgel not an expert in electronics and amps, but I own a Blackstar Ht5 MkII and after over a year of use (I practice between 30-60 minutes a day) I've had zero issues.
Nice video .What a crappy amp design !
Thanks. I guess when they are trying to give you all the options and hit a certain price point things “may” get overlooked. It’s a shame, the amp does sound okay for what it is.
Hello. My HT5R amp has started making low, contionous crackling noises, and a very distorted guitar sound. Only when when volume turned to max i can get some guitar sound out of it, though very distorted.
My tubes are perfectly fine, and i even tried replacing them with new ones.
I made a little video : ruclips.net/video/6hRHwseQZgo/видео.html
Would be very grateful if you have an idea of what it can be, and/or if it can be repaired
Without testing voltages and resistances, it’s hard to say what the issue is. Could be a speaker, dirty potentiometer or the common issue as described in my video. I suspect it’s the latter. If you are not handy or are familiar with electronics, you will have to take the amp to a tech…. But I’m not sure it is worth it.
@@MikeFreda Thanks. After another chat with my niece, she admitted that it had been gradually declining, so it seems to be the common issue that you describe here. I will hopefully be able to use your video and go ahead and make the repairs. so thanks for making this video for the rest of us, so that we can get our amps back working ✌
Blackstar did terribly with this amp.