Good Morning Mr. Barry Kassab! Many, many thanks! It's amazing how there are people who help like Mr.! I will do the procedure and I will report the result again! Congratulations on being such a wonderful person! a big hug!
Incredible your kindness Mr. Barry Kassab! I have an equal App with the same problem! And the key of the stand by, even in off, there is a high voltage in the plate of the tubes!
carl moren, the standby only changes the bias from putting the power tubes from a bias of -80 on standby mode and back to -24v on operation mode. The plate voltage is always on regardless. Unplugging the input or speaker will also put the amp into standby mode even if the switch is on.
Thank you so much. The problem was driving me nuts for months. Tried changing out my pedal board and connections and nothing worked and still had the unexplained cut- outs. Drilled the 2 holes and now the amp works perfectly . :))
helmut heer I’m glad you made use of this video, just a side question, was it hard to find this video on RUclips & google? I’m about to post an EL84 mod too to this amp.
@@BarryKassab No. just typed in the problem on u-tube and it came up. So happy. Our electronics guy first thought it was weird, but then all made sense and he drilled the holes--problem solved! thanks again--Helmut
OMG thank you!!! This worked! It took me less than an hour and $2.00 for two drill bits. I had literally just traded my backup amp yesterday for some pickups. The amp stopped pumping the first time I flipped the standby this morning. She's breathing fire again. Thank you so much!
@@niptodstan I honestly didn't bias the amp. I also never removed the valves/tubes from their sockets. I was super gentle and laid the board on pillows. It's my understanding that if I haven't removed them they shouldn't need biased. I could be very wrong. I'm not a professional amp repairman, just a musician. However, I'd argue that the way I did it wouldn't be any different than just unplugging the amp. That being said, I'm not for certain if it's worth doing the holes before the amp chokes or not. Yours may never choke out, or it may choke an hour from now. Lol just your preference I'd say. Good luck dude!
There is only 1 mains transformer, that is usually either 120v or 220/240v the other transformer is the output transformer that is linked to the tubes that is an impedance transformer. The 12BH7 is running on a voltage close to 400v DC. Hope that helps
Mr. Barry! You are the master! It worked! The bias is at -22V! The mosfet are working at a temperature of 100 °! it's normal? Well ... the ampi is talking a lot! However at 12bh7 it is 60%! But it's working!
Hello Mr. Kassab! First of all thank you for sharing your knowledge! I have some problems with my own HT-5, not the R version. Made in Korea with regular components, not SMD. I think it's the very first production line of HT-5s. I tried to measure what you said in the video but it seems that the schematic ia quite different. I have no TP-5, 6, 7 etc. I only found the r38 and r39 pair which measure around 16 volts on standby and around 80 in operating mode. I don't know if this is normal. My complaints are that I have to wait very long time after startup until i get any sound from the speaker. Maybe after 5 mins I get very weak and distorted signal even at full volume. Then it starts getting stronger but fluctuates like I am doing volume swells. It needs around ten minutes to get into normal condition. If I turn off and immediately turn back on again it sounds fine. So the problem is when the amp is cold, or at least wasn't operational for some time. Do you think it's the 12BH7 or the problem is more serious with some of the components? I don't see anything suspicious on the PCB. No burns, no darker stuff, no discoloration of components, no swollen condensers, nothing. Thank you very much!
Hi Barry, Thanks for the awesome video. I performed this fix on my amp about a month ago as I had some crackling and then everything returned to normal. Did not swap anything as it was all in good shape just had a little discoloration on the back of the board. Suddenly today i got some crackling when switching from standby to on and then after 10mins of playing the volume on the clean channel fluctuated and dropped but went on playing. Didn;t have a chance to open up again but any idea what it may be? Tubes maybe?
Thanks for the comment. When the symptoms are not completely gone it means that the drilled holes are not done properly. Make sure the holes are in an oval shape clearing as much as possible between the MOSFET pins. If the amp is over 2 years old then changing the 12BH7 power tube would be due especially if the amp is pushed more often.
@@BarryKassab Thank you for taking the time to reply, The holes were oval i took care of that and the symptoms were gone in the first place. Also on second inspection today i see that when the amp powers up the clean channel plays loud and clear. After about 20-30 minutes the volume drop occurs.
@@AgapiosTsakiris this seems like a sign of some conductive residue in the PCB, with heat the pcb starts leaking further more. One of the users had a similar issue here and he had a comment about the same challenge. After redoing the holes it ran perfectly. If the power tube was weak it will be obvious from the start of operation. Keep me posted
@@BarryKassab Hello mate thanks for the response. I took out the fets and the 2 electrolytics (c45, c46)and will widen the holes and cleanup all the area later today see how it goes. Two of the fet legs broke off so dont know if that could be the culprit. They tested fine though. resistors and caps were spot on but will swap the electrolytics just for peace of mind. Which of the fet legs arc usually? I was thinking of keeping the G of both fets on the top side of the board only. You think that might help?
@@AgapiosTsakiris usually the leaks are between the gate and source. You may buy replacements are they are not expensive at all. I’d upgrade them too to IRF840 which is a higher current so they would withstand the heat more then the IRF830.
I think I might have this problem, maybe the opposite, I'm not sure. Only had the amp a few weeks second hand. I set the amp then after playing for an hour or so the volume jumps up then after a few minutes drops back down, is that a tube change or is it time to get my drill out? I have the HT 5 head for the stack, not the combo like you but I assume it's the same circuit.
it shares the same circuit, best is to open it up and look for the discoloration of the area and resistors. then you may do the needful as per the video
Have a look at the pcb and if you see the same overheated resistors it would be the same, but the HT5 is quite old so you might just have to replace the 12BH7 power tube
@@thesojourner7722 well that’s good to know, this issue happens mostly with the HT5R so it’s good to know that this fix also helped resolving your amp. I’m about to post a video about a major mod to the power stage so stay tuned ;)
Hello there! Thanks so much for this video, I have replaced the 12BH7 tube in my amp but I am not 100% sure if I've done it correctly. The amp runs quite warm (control knobs and switches are quite warm to the touch) and I'm not sure if this is normal. I have set the bias with the volumes and gain at zero, but also I set it only on the clean channel. Right now I'm reading -27V on TP6 and TP7. Not sure what I've done wrong. They are not 22V but at least they are balanced? Must I select the distortion channel and perform measurements with that active? I set the bias using resistor R33 by the way (or pin 3 on the bh7) and I set it to 50mV based on the measured plate voltage of 470V. The amp is not behaving weirdly apart from getting a bit warm. It sounds quite good actually. I'm new to tube amps so I have no idea how warm it should get! Please let me know what you think! Oh by the way, I checked the voltages in standby mode and they are very different. Clean channel. TP6 and TP7 are reading -62V, I don't know if this is very high, or very low because it is negative?
floydthebarber71 well, starting for the last point which is the -67v that's how the amp runs in standby which means it biases the output tube to be completely off. Once you plug the speaker and input then switch to operation mode it lifts it up to about -25v. Tubes naturally warm up due to the filament heaters that heats the cathodes to create free electronics to be emitted to the anode through the grid, hence the minus biasing holds those free electrons from passing until a signal comes into the grid and attracts those free electrons to flow. That's the simplest way to explain how tubes work. Tubes were ditched to silicon transistors due to excessive power consumption and heat, so what you are experiencing is normal. Since the amp is working fine then that's a good sign already and I'm glad people are making use of this video!
Barry Kassab yes, thank you! I think the fact that you reply to all of us really helps too! Okay so my TP6 and TP7 voltages not being 22V is okay? It wasn't clear to me for whatever reason whether they had to be 22V or just equal :) Thanks Barry
floydthebarber71 the actual right way to bias the tube is by reading the cathode current. But that's going to be quite hard for most of the amp users. As long as bias voltage is within the range and equal on both tubes then you are fine.
Barry Kassab I did bias initially using the cathode method. It is actually not much more difficult than anything you've described in your vid. All you have to do is test Pin 1 on the BH7 to get the plate voltage, show some quick calculations for the cathode mV reading, then set that using Pin 3 on BH7 (which is identical reading to R33 resistor). Thanks again!
floydthebarber71 I agree to the above, I'd still prefer avoiding the explanation of ohms law and going to the straightforward readout on the voltmeter.
Hi! Can I just plug in my cabinet instead of the dummy jack? Also, when making voltage measurements should the standby switch be on or off? Sorry if my questions sound so newbie. :)
Van you can use the Cab, you may hear pops when you attach the meter probe. As for the standby it has to be on operation mode otherwise the voltage will be quite lower to the minus. Also make sure you have the dummy jack in the input or the instrument jack but the volume/ gain turned down to have no signal to distrust the biasing. Good luck!
@@BarryKassab Without a cab, doesn't this damage a tube amplifier? Amp manual suggests always connecting a speaker/cab. I ask this purely because i also have repaired my HT-5RH using the same method and wondered.
elandmancrs while biasing you’re not running the amp, it’s on active mode without running audio and that will not damage the amp. The damage is when you run the amp with full audio signal and no cab load then this is going to destroy the power tube. Moreover the amp put its self in standby mode if the Jack is not plugged in. As for the bias again this is totally fine.
Mr. Barry! Good Morning! Is working, but it has noises and failures in gain. Would it be 12bh7 for being bad? There seems to be a small hunnn when calling without standby! Forgive me or bother you! hugs!
first you need to check the sound from the emulated out, if the drops happen from the emulated out as well, then you need to check the preamp tubes, if not then the holes you made are not done well or the resistor which was overheated needs replacement, also you need to resolder the pins at this area depending on how bad the overheating was. send me a picture to my email on barry@barryworks.com
First of all, I want to thank you so much for answering Mr. Barry! I'll do all this ... as soon as I can send the photos! Incredible answer from Mr. Barry! thank you so much!
Great video and overview! In this case, if i have to change only the power tube with an other one different from stock one, where i have to control the mV values in order to bias it?? Only between cathode R33 and ground (Plate)?
roberto basp @2:10 you can see the two pots, one for bias and one for the balance. As long as the new tube got the biasing in the range of the original circuit it should work. Otherwise you need to modify the bias power supply which will be different
roberto basp all 12BH7 got the same bias voltage. EH repackages Sovtek tubes but all manufacturers need to adhere to the specs of the original serial of any tube they make which is in this case 12BH7 which got a general specs that all manufacturers got to follow.
Hey Barry, thanks for the awesome video. I sent you an email with a question. Basically I fixed this issue (2x resists, 2x mosfets, drilled holes, 1x 10k resistor) and still having volume issues.
By the way make sure the holes are not only drilled but widen them to be like an ellipse between the MOSFET pins. One viewer thought he did the holes properly and when I asked him to redo the holes he said it was working well again.
@@BarryKassab Thanks Barry! I havent gotten the chance to troubleshoot again after your last email, but I'm going to attempt new tubes -> balance/bias -> redrilling in that order. Taking the board out is the most arduous part. I'll try to get pics too.
Hi Barry Kassab, I have the 1w version and I was wondering if this would fix the interference noise that I hear in my amp. The main issue is that obviously the board layout is different... thanks in advance!
Barry Kassab thanks for your super fast reply... I have changed both valves for JJ and Groove and it was keeping doing same interferencial noise, I have sent to repair and they told me that was fixed and no problem for couple of weeks and later again same problem... they issue is that until does not warm up for approx 30 min no issue then start making noises... I have tried almost everything, different sockets, cables, Guitar, cleaning the Contacts, etc.. so I was hoping something like this video would fix it... or maybe you could have a closer idea about the problem... thanks once again!
Mr. Barry. Would you help me? I need the Black star ID260TVP amplifier scheme. Do you know how to meet? source problem. I do not know the voltages that work. If you can help me I'm very grateful! Happy Holidays and a Merry Christmas!
carl moren, I never got those on repair to be honest so don’t have the schematics. But you can share the pictures of the pcb and are you facing on my email. Barry@barryworks.com I’ll help you debug the issue as the circuit isn’t complicated.
Paul thanks for the comments, since it worked again you don’t really need to change the resistor. It might only be overheated. I remember it was 33K but let me confirm that when I land as I’m on a flight now and I can not access plenty of resources. Cheers
___d I've kept this one as it was still measuring the correct value, in some cases I had to change the resistors. So it's a case by case. Better to measure it with a multimeter and it should read 22k give or take. If you aren't sure about them then replace them they are cheap anyway. But to be honest if the resistors are gone I would suspect that the MOSFETs are still intact. Email me a picture of the board and I may assist you. Barry@barryworks.com
Wow. Thank you!! So glad I stumbled on this video. Until now, I thought it was my pedals cutting out. Gonna try this tomorrow. I also just bought a new 12BH7A tube replacement. Any tips for biasing HT5 tubes? Thanks again
Thanks again in advance Barry. I can see you've been very helpful to a lot of people in the comments section. So far, I've drilled the holes and am ready to bias. Stupid question: I'm guessing that the amp must be turned on to do the biasing, and that the black lead of my multimeter would need to be attached to a ground terminal somewhere on the pcb, yes/no? Also. I've also noticed a lot of yellow muck around the larger 22uf and 100uf capacitors. Could this be blown or leaky capacitors? Or is it just some sort of circuit board goop? It looks and feels rubbery, more like goop. Anyways, Thanks again for all your help, and a great video.
FandangleTechery thanks for the above, yes bias needs the unit ON, are for the goopy residue this might be a leaked capacitor especially if it bulged from the top. I'd change them to make sure they are not faulty.
Thanks again Barry. I got the amp working. It's definitely running and sounding better but still cuts out at higher volume. From what I gather, I might need to drill the holes a little bigger. As for the goopy capacitors, I think they're okay. I put a photo up on an amp builder page and am told it's just goop to keep the caps upright. Anyways. thanks again.
FandangleTechery ah then that's the adhesive used on the capacitors, that's normal. As for the holes you need to make sure no brownish heated parts of the pcb is around the power MOSFETs, sometime earlier one of the viewers had the same issue and it was done by drilling in an oval shape. Also if your power tube is old it may give the same issues. Sadly TAD tubes aren't of a long life, I had few discussions with them in NAMM show and they admitted that some EL34s had some issues, but overall they didn't prove to me any durability in opposed to other tube like JJ's. Let me know how it goes
I had a similar problem...not sure if it's like this... But luckily... I just fixed it by replacing the Output transformer...maybe any one have to check it first.
Me4ever that does happen, the issue above can eventually cause the output transformer also to fail. I haven’t came across any blackstar with a bad output transformer yet. Thanks for sharing though!
Hi Barry, I have an early HT5 made in Korea, and it started to choke and cut out re your video - BUT my R38 and R39 aren't in the same place as the ones in your video. And mine are both RED/RED/Orange - whereas your R39 is clearly different (brown/brown/brown?). TR2 and TR3 are next to each other, but a good 7mm away. I could email/whatsapp some pictures if you give me an email. Any thoughts? Many Thanks
Scott Durfee make sure you have the input jacks and speaker jacks active and put out of the standby more to measure it. If it stays -40 it will mean you have another issue and it might be the MOSFETs.
Hi Barry! I have a the same problem with my Blackstar HT5-RH, that you describe in the video. The output doesn't work and emulated output work just fine. I look at the mosfets and the holes was already done as you can see (image.ibb.co/kWGxNG/IMG_20171227_140741.jpg) R38 & R39 are fine and TP7 & TP6 -22V.. Any Idea? Thank you very much!!
Boris Pugnaloni that’s a new version of the same Amp, measure the voltage on the middle pin of the MOSFETs it should be around 230v if that’s not there then the HV fuse is blown due to a bad output tube.
Just a moment ago on the BS forums I read that Korea productions are better, lol, that's why I say that doesn't matter where's the product made as long as it's properly made.
Paul Arias the first production phase of BS amps were in Korea, but later on they changed to China. The Korean version never got this issue which I explained here which is due to the PCB voltage rating.
Hi barry! I have an bugera g5 with problems. Eulated output works but the output sounds very bad. i have an link: ruclips.net/video/_PeSSabutVg/видео.html Maybee its the same problem of blackstar ht5
Years ago I bought a broken ht5r with this problem for € 85,- and revived with this relatively easy fix. Great amp! Great video, self explanatory 👍
Thanks for the feedback! Hope to be able to make more videos like this
Good Morning Mr. Barry Kassab! Many, many thanks! It's amazing how there are people who help like Mr.! I will do the procedure and I will report the result again! Congratulations on being such a wonderful person! a big hug!
Incredible your kindness Mr. Barry Kassab! I have an equal App with the same problem! And the key of the stand by, even in off, there is a high voltage in the plate of the tubes!
carl moren, the standby only changes the bias from putting the power tubes from a bias of -80 on standby mode and back to -24v on operation mode. The plate voltage is always on regardless. Unplugging the input or speaker will also put the amp into standby mode even if the switch is on.
Thank you so much. The problem was driving me nuts for months. Tried changing out my pedal board and connections and nothing worked and still had the unexplained cut- outs. Drilled the 2 holes and now the amp works perfectly . :))
helmut heer I’m glad you made use of this video, just a side question, was it hard to find this video on RUclips & google? I’m about to post an EL84 mod too to this amp.
@@BarryKassab No. just typed in the problem on u-tube and it came up. So happy. Our electronics guy first thought it was weird, but then all made sense and he drilled the holes--problem solved! thanks again--Helmut
helmut heer thanks for sharing the information, enjoy playing the amp, please share the video :)
OMG thank you!!!
This worked! It took me less than an hour and $2.00 for two drill bits.
I had literally just traded my backup amp yesterday for some pickups. The amp stopped pumping the first time I flipped the standby this morning. She's breathing fire again. Thank you so much!
Alex Shuck glad you made use of this, like & share 🙂
So did you just drill the holes or bias the tubes too? I’ve got two HT5’s that work fine. Would it be worth me drilling the holes in both of them?
@@niptodstan I honestly didn't bias the amp. I also never removed the valves/tubes from their sockets. I was super gentle and laid the board on pillows. It's my understanding that if I haven't removed them they shouldn't need biased. I could be very wrong. I'm not a professional amp repairman, just a musician. However, I'd argue that the way I did it wouldn't be any different than just unplugging the amp.
That being said, I'm not for certain if it's worth doing the holes before the amp chokes or not. Yours may never choke out, or it may choke an hour from now. Lol just your preference I'd say. Good luck dude!
Biasing the amp always depends on the life span of the tube, it’s good to check the bias and the bias balance pots since it’s opened up.
LarryUK yes better you drill in both Mosfets as you never know when the pcb will fail again and cause the same damage to the other parts
hello, thank you very much for the video, ask what voltage are the 2 transformers?
Thanks for the comment, not sure which transformer you’re referring to? Is it the DC voltage post the mains transformer? Or something else?
@@BarryKassab i mean the 2 mains tranformer, are they 220/24 VAC? :)
There is only 1 mains transformer, that is usually either 120v or 220/240v the other transformer is the output transformer that is linked to the tubes that is an impedance transformer. The 12BH7 is running on a voltage close to 400v DC. Hope that helps
Mr. Barry! You are the master! It worked! The bias is at -22V! The mosfet are working at a temperature of 100 °! it's normal? Well ... the ampi is talking a lot! However at 12bh7 it is 60%! But it's working!
carl moren congratulations! Get some Mullard tubes and you will get better results too
no doubt! thank you so much ! You got a friend here, Mr. Barry!
Have a happy mother's day with your family, master!
carl moren thank you!
Hello Mr. Kassab!
First of all thank you for sharing your knowledge! I have some problems with my own HT-5, not the R version. Made in Korea with regular components, not SMD. I think it's the very first production line of HT-5s.
I tried to measure what you said in the video but it seems that the schematic ia quite different. I have no TP-5, 6, 7 etc. I only found the r38 and r39 pair which measure around 16 volts on standby and around 80 in operating mode. I don't know if this is normal.
My complaints are that I have to wait very long time after startup until i get any sound from the speaker. Maybe after 5 mins I get very weak and distorted signal even at full volume. Then it starts getting stronger but fluctuates like I am doing volume swells. It needs around ten minutes to get into normal condition. If I turn off and immediately turn back on again it sounds fine. So the problem is when the amp is cold, or at least wasn't operational for some time.
Do you think it's the 12BH7 or the problem is more serious with some of the components?
I don't see anything suspicious on the PCB. No burns, no darker stuff, no discoloration of components, no swollen condensers, nothing.
Thank you very much!
I think I missed seeing this comment, your issue is a typical symptom of the repair above.
great Video and thank you! i'll be opening up my amp later today.
Hi Barry,
Thanks for the awesome video. I performed this fix on my amp about a month ago as I had some crackling and then everything returned to normal. Did not swap anything as it was all in good shape just had a little discoloration on the back of the board.
Suddenly today i got some crackling when switching from standby to on and then after 10mins of playing the volume on the clean channel fluctuated and dropped but went on playing.
Didn;t have a chance to open up again but any idea what it may be?
Tubes maybe?
Thanks for the comment. When the symptoms are not completely gone it means that the drilled holes are not done properly. Make sure the holes are in an oval shape clearing as much as possible between the MOSFET pins. If the amp is over 2 years old then changing the 12BH7 power tube would be due especially if the amp is pushed more often.
@@BarryKassab Thank you for taking the time to reply,
The holes were oval i took care of that and the symptoms were gone in the first place.
Also on second inspection today i see that when the amp powers up the clean channel plays loud and clear. After about 20-30 minutes the volume drop occurs.
@@AgapiosTsakiris this seems like a sign of some conductive residue in the PCB, with heat the pcb starts leaking further more. One of the users had a similar issue here and he had a comment about the same challenge. After redoing the holes it ran perfectly. If the power tube was weak it will be obvious from the start of operation. Keep me posted
@@BarryKassab Hello mate thanks for the response.
I took out the fets and the 2 electrolytics (c45, c46)and will widen the holes and cleanup all the area later today see how it goes. Two of the fet legs broke off so dont know if that could be the culprit.
They tested fine though.
resistors and caps were spot on but will swap the electrolytics just for peace of mind.
Which of the fet legs arc usually? I was thinking of keeping the G of both fets on the top side of the board only. You think that might help?
@@AgapiosTsakiris usually the leaks are between the gate and source. You may buy replacements are they are not expensive at all. I’d upgrade them too to IRF840 which is a higher current so they would withstand the heat more then the IRF830.
I think I might have this problem, maybe the opposite, I'm not sure. Only had the amp a few weeks second hand. I set the amp then after playing for an hour or so the volume jumps up then after a few minutes drops back down, is that a tube change or is it time to get my drill out? I have the HT 5 head for the stack, not the combo like you but I assume it's the same circuit.
it shares the same circuit, best is to open it up and look for the discoloration of the area and resistors. then you may do the needful as per the video
Brilliant, cheers for the quick reply mate, appreciate it.
I've the same symptoms but with the HT5 no reverb head maybe the first version of this amp... Is this fix the same for it?
Have a look at the pcb and if you see the same overheated resistors it would be the same, but the HT5 is quite old so you might just have to replace the 12BH7 power tube
@@BarryKassab Good news, I drilled the holes between the mosfet legs and it works great, changed no components at all... very happy
@@thesojourner7722 well that’s good to know, this issue happens mostly with the HT5R so it’s good to know that this fix also helped resolving your amp. I’m about to post a video about a major mod to the power stage so stay tuned ;)
Hi Mr. Kassab,
I try to buy the R38 and R39, but the seller needs more details, could you pleas help me with that.
THX
Thomas
emollme they are 22K Ohms 2 Watts should be easy to find
Hello there! Thanks so much for this video, I have replaced the 12BH7 tube in my amp but I am not 100% sure if I've done it correctly. The amp runs quite warm (control knobs and switches are quite warm to the touch) and I'm not sure if this is normal.
I have set the bias with the volumes and gain at zero, but also I set it only on the clean channel. Right now I'm reading -27V on TP6 and TP7. Not sure what I've done wrong. They are not 22V but at least they are balanced? Must I select the distortion channel and perform measurements with that active?
I set the bias using resistor R33 by the way (or pin 3 on the bh7) and I set it to 50mV based on the measured plate voltage of 470V.
The amp is not behaving weirdly apart from getting a bit warm. It sounds quite good actually. I'm new to tube amps so I have no idea how warm it should get! Please let me know what you think!
Oh by the way, I checked the voltages in standby mode and they are very different. Clean channel. TP6 and TP7 are reading -62V, I don't know if this is very high, or very low because it is negative?
floydthebarber71 well, starting for the last point which is the -67v that's how the amp runs in standby which means it biases the output tube to be completely off. Once you plug the speaker and input then switch to operation mode it lifts it up to about -25v. Tubes naturally warm up due to the filament heaters that heats the cathodes to create free electronics to be emitted to the anode through the grid, hence the minus biasing holds those free electrons from passing until a signal comes into the grid and attracts those free electrons to flow. That's the simplest way to explain how tubes work. Tubes were ditched to silicon transistors due to excessive power consumption and heat, so what you are experiencing is normal. Since the amp is working fine then that's a good sign already and I'm glad people are making use of this video!
Barry Kassab yes, thank you! I think the fact that you reply to all of us really helps too! Okay so my TP6 and TP7 voltages not being 22V is okay? It wasn't clear to me for whatever reason whether they had to be 22V or just equal :) Thanks Barry
floydthebarber71 the actual right way to bias the tube is by reading the cathode current. But that's going to be quite hard for most of the amp users. As long as bias voltage is within the range and equal on both tubes then you are fine.
Barry Kassab I did bias initially using the cathode method. It is actually not much more difficult than anything you've described in your vid. All you have to do is test Pin 1 on the BH7 to get the plate voltage, show some quick calculations for the cathode mV reading, then set that using Pin 3 on BH7 (which is identical reading to R33 resistor). Thanks again!
floydthebarber71 I agree to the above, I'd still prefer avoiding the explanation of ohms law and going to the straightforward readout on the voltmeter.
Hi! Can I just plug in my cabinet instead of the dummy jack? Also, when making voltage measurements should the standby switch be on or off? Sorry if my questions sound so newbie. :)
Van you can use the Cab, you may hear pops when you attach the meter probe. As for the standby it has to be on operation mode otherwise the voltage will be quite lower to the minus. Also make sure you have the dummy jack in the input or the instrument jack but the volume/ gain turned down to have no signal to distrust the biasing. Good luck!
@@BarryKassab Without a cab, doesn't this damage a tube amplifier? Amp manual suggests always connecting a speaker/cab. I ask this purely because i also have repaired my HT-5RH using the same method and wondered.
elandmancrs while biasing you’re not running the amp, it’s on active mode without running audio and that will not damage the amp. The damage is when you run the amp with full audio signal and no cab load then this is going to destroy the power tube. Moreover the amp put its self in standby mode if the Jack is not plugged in. As for the bias again this is totally fine.
Mr. Barry! Good Morning! Is working, but it has noises and failures in gain. Would it be 12bh7 for being bad? There seems to be a small hunnn when calling without standby! Forgive me or bother you! hugs!
first you need to check the sound from the emulated out, if the drops happen from the emulated out as well, then you need to check the preamp tubes, if not then the holes you made are not done well or the resistor which was overheated needs replacement, also you need to resolder the pins at this area depending on how bad the overheating was. send me a picture to my email on barry@barryworks.com
First of all, I want to thank you so much for answering Mr. Barry! I'll do all this ... as soon as I can send the photos! Incredible answer from Mr. Barry! thank you so much!
Great video!!!!!!!!!!!!
Great video and overview! In this case, if i have to change only the power tube with an other one different from stock one, where i have to control the mV values in order to bias it?? Only between cathode R33 and ground (Plate)?
roberto basp @2:10 you can see the two pots, one for bias and one for the balance. As long as the new tube got the biasing in the range of the original circuit it should work. Otherwise you need to modify the bias power supply which will be different
So can i apply the same mV values to the other Power tube NOS? I thought it has different value from the original stock one.
roberto basp tell me which tube you intend to use and I’ll let you know if you can use the same bias voltage.
I have to decide between a Nos 12BH7A or Electro Harmonix 12BH7A....
roberto basp all 12BH7 got the same bias voltage. EH repackages Sovtek tubes but all manufacturers need to adhere to the specs of the original serial of any tube they make which is in this case 12BH7 which got a general specs that all manufacturers got to follow.
Hi Barry so did u drill 4 holes in total two on the 3 and two on the 2???
That’s correct, 4 holes, 2 for each MOSFET
Hey Barry, thanks for the awesome video. I sent you an email with a question. Basically I fixed this issue (2x resists, 2x mosfets, drilled holes, 1x 10k resistor) and still having volume issues.
Frederick Weissbach I’ve responded to your email with full details, hope it helps you up! Thanks for watching pls like & share :)
By the way make sure the holes are not only drilled but widen them to be like an ellipse between the MOSFET pins. One viewer thought he did the holes properly and when I asked him to redo the holes he said it was working well again.
@@BarryKassab Thanks Barry! I havent gotten the chance to troubleshoot again after your last email, but I'm going to attempt new tubes -> balance/bias -> redrilling in that order. Taking the board out is the most arduous part. I'll try to get pics too.
Hi! I have a HT5 combo, where are you checking voltages to adjust bias?
Franck Garcia look at the TP6 and TP7
Hi Barry Kassab, I have the 1w version and I was wondering if this would fix the interference noise that I hear in my amp. The main issue is that obviously the board layout is different... thanks in advance!
Jesus Juste Lucero they are quite different the ht1 consumes the output tube quite fast, change the 12AU7 and the sound will be restored
Barry Kassab thanks for your super fast reply... I have changed both valves for JJ and Groove and it was keeping doing same interferencial noise, I have sent to repair and they told me that was fixed and no problem for couple of weeks and later again same problem... they issue is that until does not warm up for approx 30 min no issue then start making noises... I have tried almost everything, different sockets, cables, Guitar, cleaning the Contacts, etc.. so I was hoping something like this video would fix it... or maybe you could have a closer idea about the problem... thanks once again!
Jesus Juste Lucero record it from the emulated put and from a mic and email it to me on barry@barryworks.com
To regulate the bias, is not a load of 8 holms on the output? And at the entrance uses a jack? I'm sorry, I'm bad in English!
carl moren, any jack inserted in the amp is required just to put the amp in operation mode. Keep the channel on clean and volume down
Awesome man! Thanks so much!
Mr. Barry. Would you help me? I need the Black star ID260TVP amplifier scheme. Do you know how to meet? source problem. I do not know the voltages that work. If you can help me I'm very grateful! Happy Holidays and a Merry Christmas!
carl moren, I never got those on repair to be honest so don’t have the schematics. But you can share the pictures of the pcb and are you facing on my email. Barry@barryworks.com I’ll help you debug the issue as the circuit isn’t complicated.
Many thanks for answering Mr. Barry !! I sent the photos in your email! thank you so much!!!
Thanks a lot ! It worked!
I assume I need to change my R39 resistor but I don’t know the specifications!
Paul thanks for the comments, since it worked again you don’t really need to change the resistor. It might only be overheated. I remember it was 33K but let me confirm that when I land as I’m on a flight now and I can not access plenty of resources. Cheers
Barry Kassab No problem, thanks ;)!
Paul it’s 22K 2W
Did you leave the burnt resistor in there or did you replace it?
___d I've kept this one as it was still measuring the correct value, in some cases I had to change the resistors. So it's a case by case. Better to measure it with a multimeter and it should read 22k give or take. If you aren't sure about them then replace them they are cheap anyway.
But to be honest if the resistors are gone I would suspect that the MOSFETs are still intact. Email me a picture of the board and I may assist you. Barry@barryworks.com
Wow. Thank you!! So glad I stumbled on this video. Until now, I thought it was my pedals cutting out.
Gonna try this tomorrow. I also just bought a new 12BH7A tube replacement. Any tips for biasing HT5 tubes?
Thanks again
FandangleTechery thanks for the compliments, you have everything you need in this video. Feel free to ask anytime!
Thanks again in advance Barry. I can see you've been very helpful to a lot of people in the comments section.
So far, I've drilled the holes and am ready to bias. Stupid question: I'm guessing that the amp must be turned on to do the biasing, and that the black lead of my multimeter would need to be attached to a ground terminal somewhere on the pcb, yes/no?
Also. I've also noticed a lot of yellow muck around the larger 22uf and 100uf capacitors. Could this be blown or leaky capacitors? Or is it just some sort of circuit board goop? It looks and feels rubbery, more like goop.
Anyways, Thanks again for all your help, and a great video.
FandangleTechery thanks for the above, yes bias needs the unit ON, are for the goopy residue this might be a leaked capacitor especially if it bulged from the top. I'd change them to make sure they are not faulty.
Thanks again Barry. I got the amp working. It's definitely running and sounding better but still cuts out at higher volume. From what I gather, I might need to drill the holes a little bigger. As for the goopy capacitors, I think they're okay. I put a photo up on an amp builder page and am told it's just goop to keep the caps upright. Anyways. thanks again.
FandangleTechery ah then that's the adhesive used on the capacitors, that's normal. As for the holes you need to make sure no brownish heated parts of the pcb is around the power MOSFETs, sometime earlier one of the viewers had the same issue and it was done by drilling in an oval shape. Also if your power tube is old it may give the same issues. Sadly TAD tubes aren't of a long life, I had few discussions with them in NAMM show and they admitted that some EL34s had some issues, but overall they didn't prove to me any durability in opposed to other tube like JJ's. Let me know how it goes
I'm getting -40V at TP6 and TP7...any thoughts?
This is when the amp doesn’t have any jacks plugged in so the amp will remain in standby mode by forcing a turn-off bias voltage
Thank you very much Barry!! I did it as you explain in the video ad it worked!! Thanks for sharing!!
Manuel Lozano glad you made use of it!
thanks for the video great work
I had a similar problem...not sure if it's like this... But luckily... I just fixed it by replacing the Output transformer...maybe any one have to check it first.
Me4ever that does happen, the issue above can eventually cause the output transformer also to fail. I haven’t came across any blackstar with a bad output transformer yet. Thanks for sharing though!
Hi Barry, I have an early HT5 made in Korea, and it started to choke and cut out re your video - BUT my R38 and R39 aren't in the same place as the ones in your video. And mine are both RED/RED/Orange - whereas your R39 is clearly different (brown/brown/brown?). TR2 and TR3 are next to each other, but a good 7mm away. I could email/whatsapp some pictures if you give me an email. Any thoughts? Many Thanks
Sim Jones you can email me on barry@barryworks.com
Hi, I have the ht-5 head as well like you have ( not the ht-5rh). I am having the same problem. Did you manage to fix yours?
I'm getting -40V at TP6 and TP7...why?
Scott Durfee make sure you have the input jacks and speaker jacks active and put out of the standby more to measure it. If it stays -40 it will mean you have another issue and it might be the MOSFETs.
Hi Barry! I have a the same problem with my Blackstar HT5-RH, that you describe in the video. The output doesn't work and emulated output work just fine. I look at the mosfets and the holes was already done as you can see (image.ibb.co/kWGxNG/IMG_20171227_140741.jpg)
R38 & R39 are fine and TP7 & TP6 -22V.. Any Idea? Thank you very much!!
Boris Pugnaloni that’s a new version of the same Amp, measure the voltage on the middle pin of the MOSFETs it should be around 230v if that’s not there then the HV fuse is blown due to a bad output tube.
Just a moment ago on the BS forums I read that Korea productions are better, lol, that's why I say that doesn't matter where's the product made as long as it's properly made.
Paul Arias the first production phase of BS amps were in Korea, but later on they changed to China. The Korean version never got this issue which I explained here which is due to the PCB voltage rating.
Barry Kassab is not Korean made? in your video reads on the rear of the head: Made under license in Korea.
Paul Arias I didn't notice, but I know that those are the second version, the earlier version had the standard component and not the SMD components.
Barry Kassab how can you tell the stardard component from the SMD?
Paul Arias those tiny component that looks like it's just stamped on top of the pcb are SMD. Surface mounted is what it stands for.
Hi barry! I have an bugera g5 with problems. Eulated output works but the output sounds very bad. i have an link: ruclips.net/video/_PeSSabutVg/видео.html
Maybee its the same problem of blackstar ht5