Ahhh could not wait for tomorrow so I went at it tonight and fixed it.Thanks again Terry. My speaker wires were nowhere near my 12ax7 but by looking closer I realized that the NFB wire was causing the problem so I cut it off and voilá whine gone, who needs NFB anyways. Awesome channel.
Hey Terry thanks for this info! I'm currently scratch building a 5F1 (not my first build) and I did buy a chassis from the company who makes the chassis in this video. Personally I thought the OT was too close to the 12ax7 so I had panned on moving it about an inch closer to the PT. Your vid is spot on, the speaker jack is right next to the 12AX7 I will move it between the 6v6 and the 5Y3, which also has the benefit of giving me enough room for a 2nd speaker jack for an 8ohm tap!
Another way it could oscillate is that if it's using negative feedback, the output transformer primary could be wired wrong. Flip the leads of the primary of the output transformer. If they're backwards, then instead of having negative feedback, you have positive feedback, and it will oscillate.
Man, you saved my built! I did the changes and took some precaution of the video but none quite work. As soon as i tested flipping the primary windings it became perfect! Thanks a lot!
I picked up a 3 tube 6bq5 amp recently and I didn't know the impedance varied on the output. I hooked up 8ohm to 16 and the old mullard 6bq5 scorched. I gutted the old enclosure to transplant into a dead Rage 158. That looks like the perfect amp to model it off of.
thanks for your helpful video! I just had a similar problem in my 5f1. I bought each part separately, not as a diy kit (because there is no such thing in Poland). I tried every way you talk about. However, it turned out that the output transformer wires were inverted... the transformer manufacturer either incorrectly described the colors of the wires or changed the colors during assembly. Now it all works and all I have to do is remove some noise from the signal but it still sounds beautiful. Best regards
Amazing🙂 Many thanks for this!!! I have the very same problem with my AC4 clone and always connected it with loose wires in output tranny. It sounds very much like this. Thanks again!
Ah Ha Another 5F1 lecture and repair, Wow i need to create a summary of your efforts as a 5F1 notebook. This is amazing. fortunately on my Eico 147 Conversion has a built in speaker up high and the Power Output Amp is located on the speaker frame. But i will be inspecting my point to point wiring for routing issues. Great video Excellent stuff. Again! Dennis
Hi if the 5y3 had intermittent heater maybe due poor tube pins soldering (& it looked like a JJ) are just junk seen very early failures in amps mainly microphonic , great fix
Great content as always. I have recently got interested in old tube radios. Have you ever, or would you consider, doing a general info video on tube radios. Something like basic component and functions, different circuits or zones so newbies like myself could at least be able to ask intelligent questions.
Great video. Low impedance output next to a high impedance input = feedback. I wonder what would happen if you reversed the leads inside the chassis that go to the speaker jack, not at the jack but at the source at the output transformer. Feedback requires a nonlinear device and a feedback path of 180 Degrees out of phase. So reversing the phase "may" help, but I dunno. It could fix it, move the squeal to a different frequency, or make it worse. I built a low noise preamp once. All the wiring was twisted pair or shielded. I went with 6.3 V DC heater voltage (not AC), twisted those wires 3 twists per inch and ran them along the corners of the chassis. The twists go right up to the socket (if there were more sockets, it would daisy chain to the next socket from there). There is a guy that has a great web site with all the tips to design a guitar amp, but I forgot his link. Every circuit: the Safety Ground from the plug, the transformer references, and each audio circuit (just one in this case) were all single point grounded (to the chassis as a ground plane) directly and very close nearby via a solder lug tightly screwed to the chassis. 3 circuits = 3 grounding points to the ground plane and no ground loop paths. I used thick film resistors and low ESR tantalum caps. The Preamp tube had a steel shield around it. I put a mu metal shield around the power transformer (no output transformer as it was just a Preamp), the components were mounded "radio days" style with the shortest leads possible under the ground plane (tube above, components below). Some amp designs like to mount the tube socket on the same side as the components, but then there is no shield between them and noise can get a bit more pronounced. My high voltage had a 3 stage RCL filter. The hum and hiss were, very, very low (I think -70 dB if I recall) even at max input level. For those of you thinking of using an aluminum chassis... DON'T. Aluminum is electrically conductive, but 60 Hz magnetic fields will pass right through it. The chassis must be made of steel with high ferrous properties... some stainless steels are somewhat ferrous but not enough. Ferrous metals will block AC interference from DC to light. And don't forget a bottom cover of steel as well.
I would have liked to see the grounding corrections. I just bought a kit and need to better understand grounding. Terry has several amp build videos. Maybe I can figure out how he grounds his wiring.
Super helpful...just about to start my build so this is really timely! Any ideas about how that old hole next to the V1 could be used for an interesting mod? What about running the neg feedback through a variable resistor pot there? Does that just re-create the problem by putting that output signal back in close proximity to V1? Thanks!
Terry-I'm planning to build an 5F1 kit, and I saw one of your videos where you moved the fuse from the front, and placed it in the back of the chassis, and then put an on/off switch in place of the fuse. I've been searching to find that video again, but can't find it. I think it was in the 2nd part of a 2 part video repair. Can you lead me to the correct video? Thanks.
I’ve got a Silverface Vibro Champ that’s doing almost the same thing. It will whistle like that with the volume anywhere outside of the 3-7 range. I’ve placed a scope on the output and found no ultrasonic oscillations when the audible one isn’t present. I’ve checked internal lead dress, replaced all the usual suspects for a recap except for the filter can cap as it tested good and subbing in a new cap for each section didn’t change anything. Also, the grounding is all factory. Would following these same steps be feasible, or would you look at something else?
Why does everyone say tubes clip “softly”? Every time you put a vacuum tube amp on the bench and turn up the volume, the wave forms clip pretty hard in the same fashion they say transistors clip.
I know this video was 5 years ago, but I am hoping you answer this question. I am thinking of building a couple of these amps. My experience with DIY electronics kits is that the builder of the kit thinks he needs to you the cheapest crap available to build their kit. Personally, I am in the opposite camp. If I am going to build a kit, I want to build it better than original. How do I put to together a kit that fixes the problems and uses all the best components. FYI I am a mechanical guy not an electrical one. How do I build this into a Head? Can I replace the power cord with an IEC power connector? Who makes the best components? I would rather piece this thing together from parts then buy a kit, where I need to replace 90% of the parts. Can you help me out?
I could do with your experience as I am troubleshooting a 5E3 with odd voltages the cathode reading its 36v as to recommend 22v and b+ is down from the 6v6s. If you do Skype session then it would be appreciated.
That's odd about the feedback. I've seen a ton of 5F1 builds and almost all of them have the output jack located between the 12AX7 and the power tube without squealing like this one.
See, I was 95% sure it was the NFL problem. Hooking the OT up the wrong way round turns it into a positive feedback loop and causes just that problem. Still kinda think that's what it was and during the process of moving the speaker jack to a different location that wiring error was corrected. Never heard of the speaker leads being close to the 12ax7 on a 5f1 cause it to feedback. In fact, I've just wrapped them around the 12ax7 in my 5f1 and there were no issues. Not trying to be smart or anything, 5f1s are wild beasts and each one is different :P
Roger that. The low side lead was soldered directly to the transformer frame, so no way to reverse the windings. Never heard or experienced polarity to Class A output transformers.
If you run across this problem and you triple checked your wiring, component values, solder joint inspections (especially the grounds-then try swapping the output transformer (OT) leads. In other words, swap the red and blue OT wires. I occasionally run into this issue on all types of builds and OT replacement jobs. This is a great little amp for anyone 8 to 80 and the absolute best amp for a person wanting to build there own amp. Here's another tip: Don't cut those OT wires too short until you've got a functioning amp. Good luck ya'll!
I agree, swapping the wires to the output jack at the transformer output can reduce internal feedback. An oscillator (feedback) requires a nonlinear device, a feedback loop 180 Degrees out of phase, and sufficient gain to sustain the oscillaton. I learned this from my vintage 1976 Radio Shack 150-in-1 electronics kit and in high school electronics. When I design amps, my inputs/circuits are on one side of the chassis and the outputs/circuits on the other side going left to right. He you ever noticed why Fender amps put the tone controls in reverse order: Treble, Middle, Bass from left to right? That is that is how the circuitry is laid out and routes to the controls with the shortest path (no crossing over each other). It just a sound (no pun intended) method to reduce noise, not just be different. Ideally, the controls should be right next to the circuitry, but it is not practical to open up the amp to make a tone change, so the potentiometers are mounted away from the circuitry and on the front chassis for obvious reasons (albeit a bit more noisy).
I leave my OT leads on the output side as long as they come. I twist them 3 twists per inch and then extend them to the Output jack using twisted wire of the same guage with heat shrink over the splices. Then I route that 'orthogonally" along the chassis (which is my ground plane) to the Output jack. As long as I keep the wires well twisted and not running nearby or parallel to any other circuits/wires, and it being near the ground plane, all work together to prevent coupling into other circuits.
I also use Teflon jacketed wire like what is used in military system. The Teflon is difficult to strip, but it does not met until about 900 degrees F, so if you touch it with your 750 degree F soldering iron it will not melt or shrink. Of course I use all white wire because Taflon wire is expensive and keeping the rainbow decade of colors is very expensive.
Something tells me I'm not going to figure out my whistling tubes (which sound identical to these). Since the amp is a proven design, I doubt that moving things around will help.
Hey man I'm totally stumped I've built this kit and I'm not getting any secondary voltage from the power transformer to the 12ax7 or 6v6. Could anybody help me out? I've double checked the wiring, solder joints, continuity and ground.
Man, that's a strange problem. I'd like to know how the terminals are labeled on the primary and secondary side. It seems like little can go wrong with these transformers, right?
The tweed amps had both RCA and 1/4" phono terminals throughout the 50's and 1960. Most famous would be the 5F6-A 4X10 Bassman. It uses four RCA terminals, instead of parallel wiring and a single phono jack.
DeadKoby Everyone else is made in the same factory as the Sovtek. It’s possible a more recent Sino 5Y3 is okay but I cannot confirm. The JJ reads the exact same unloaded voltage as my JAN GE 6087. Loaded voltage is within 5% in a 5E3 clone.
Its either a crappy kit design or crappy directions ? These kits are costing the owners a lot more money ,because they need a expert like D labs to fix it.
Ahhh could not wait for tomorrow so I went at it tonight and fixed it.Thanks again Terry.
My speaker wires were nowhere near my 12ax7 but by looking closer I realized that the NFB wire was causing the problem so I cut it off and voilá whine gone, who needs NFB anyways. Awesome channel.
Hey Terry thanks for this info! I'm currently scratch building a 5F1 (not my first build) and I did buy a chassis from the company who makes the chassis in this video. Personally I thought the OT was too close to the 12ax7 so I had panned on moving it about an inch closer to the PT. Your vid is spot on, the speaker jack is right next to the 12AX7 I will move it between the 6v6 and the 5Y3, which also has the benefit of giving me enough room for a 2nd speaker jack for an 8ohm tap!
Thanks Terry for making me aware of potential pitfalls on my first build
Another way it could oscillate is that if it's using negative feedback, the output transformer primary could be wired wrong. Flip the leads of the primary of the output transformer. If they're backwards, then instead of having negative feedback, you have positive feedback, and it will oscillate.
Man, you saved my built! I did the changes and took some precaution of the video but none quite work. As soon as i tested flipping the primary windings it became perfect! Thanks a lot!
Terry, your sharing of your experience is highly appreciated as always. Nice job ; lesson : Go for the easy stuff first.. - Ron
Yes Sir, need to spread the knowledge/tricks!
I picked up a 3 tube 6bq5 amp recently and I didn't know the impedance varied on the output. I hooked up 8ohm to 16 and the old mullard 6bq5 scorched. I gutted the old enclosure to transplant into a dead Rage 158. That looks like the perfect amp to model it off of.
thanks for your helpful video! I just had a similar problem in my 5f1. I bought each part separately, not as a diy kit (because there is no such thing in Poland). I tried every way you talk about. However, it turned out that the output transformer wires were inverted... the transformer manufacturer either incorrectly described the colors of the wires or changed the colors during assembly.
Now it all works and all I have to do is remove some noise from the signal but it still sounds beautiful. Best regards
Amazing🙂 Many thanks for this!!! I have the very same problem with my AC4 clone and always connected it with loose wires in output tranny. It sounds very much like this. Thanks again!
You deserve an extra glass of Mad Dog 20/20 tonight for this repair Terry ? Thanks !
Ah Ha Another 5F1 lecture and repair, Wow i need to create a summary of your efforts as a 5F1 notebook. This is amazing. fortunately on my Eico 147 Conversion has a built in speaker up high and the Power Output Amp is located on the speaker frame. But i will be inspecting my point to point wiring for routing issues. Great video Excellent stuff. Again! Dennis
Always enjoy learning from your videos! Thanks D-Lab!
I added a tone circuit to my build. What a nice addition.
Thank you ,I just had the same problem with a tweed princeton( basically a champ) I have to re-route some wires tomorrow.
Hi if the 5y3 had intermittent heater maybe due poor tube pins soldering (& it looked like a JJ) are just junk seen very early failures in amps mainly microphonic , great fix
Nice intuition on finding that. 👌 I'll file that in the memory bank!
Damn your good! It’s great to see a pro fix the grip but to see a tech go above and beyond is out-a-sight. Nice job well done!!! Sincerely, Pops
Looks like you are the 5 F1 fix it guy. Nice work. This is the 3rd one I’ve seen you work on.
Great content as always. I have recently got interested in old tube radios. Have you ever, or would you consider, doing a general info video on tube radios. Something like basic component and functions, different circuits or zones so newbies like myself could at least be able to ask intelligent questions.
Great video. Low impedance output next to a high impedance input = feedback. I wonder what would happen if you reversed the leads inside the chassis that go to the speaker jack, not at the jack but at the source at the output transformer. Feedback requires a nonlinear device and a feedback path of 180 Degrees out of phase. So reversing the phase "may" help, but I dunno. It could fix it, move the squeal to a different frequency, or make it worse. I built a low noise preamp once. All the wiring was twisted pair or shielded. I went with 6.3 V DC heater voltage (not AC), twisted those wires 3 twists per inch and ran them along the corners of the chassis. The twists go right up to the socket (if there were more sockets, it would daisy chain to the next socket from there). There is a guy that has a great web site with all the tips to design a guitar amp, but I forgot his link. Every circuit: the Safety Ground from the plug, the transformer references, and each audio circuit (just one in this case) were all single point grounded (to the chassis as a ground plane) directly and very close nearby via a solder lug tightly screwed to the chassis. 3 circuits = 3 grounding points to the ground plane and no ground loop paths. I used thick film resistors and low ESR tantalum caps. The Preamp tube had a steel shield around it. I put a mu metal shield around the power transformer (no output transformer as it was just a Preamp), the components were mounded "radio days" style with the shortest leads possible under the ground plane (tube above, components below). Some amp designs like to mount the tube socket on the same side as the components, but then there is no shield between them and noise can get a bit more pronounced. My high voltage had a 3 stage RCL filter. The hum and hiss were, very, very low (I think -70 dB if I recall) even at max input level.
For those of you thinking of using an aluminum chassis... DON'T. Aluminum is electrically conductive, but 60 Hz magnetic fields will pass right through it. The chassis must be made of steel with high ferrous properties... some stainless steels are somewhat ferrous but not enough. Ferrous metals will block AC interference from DC to light. And don't forget a bottom cover of steel as well.
If you used shielded speaker cable would that also make a difference? thank you Love the content.
A great video! Thanks! I wanna hear you play the amp!
Thanks for sharing!!! A masterclass on every video. 73’s!
I wish you would have told and shown us how you rewired the grounds. Did they all go to one ground or three?
Looks like this might be a good kit to learn troubleshooting on !
I would have liked to see the grounding corrections. I just bought a kit and need to better understand grounding. Terry has several amp build videos. Maybe I can figure out how he grounds his wiring.
Ray Voorhies look up rob robinettes 5f1 layout.
Much better grounding scheme.
Did you use sheet stock on the grounding fix? I've seen you do that in other vids
so helpful!
Thanks for the tips, Terry.
That was a good one! Thanks Terry!
Super helpful...just about to start my build so this is really timely! Any ideas about how that old hole next to the V1 could be used for an interesting mod? What about running the neg feedback through a variable resistor pot there? Does that just re-create the problem by putting that output signal back in close proximity to V1? Thanks!
That damn kit has foiled so many people!
Maybe ol Terry dog should make a kit schematic, project amp........Jus thinking'!!!!
Thanks for the info Terry.
Terry-I'm planning to build an 5F1 kit, and I saw one of your videos where you moved the fuse from the front, and placed it in the back of the chassis, and then put an on/off switch in place of the fuse. I've been searching to find that video again, but can't find it. I think it was in the 2nd part of a 2 part video repair. Can you lead me to the correct video? Thanks.
ruclips.net/video/bqajFiV8wfc/видео.html It's at about 8:30 in.
I’ve got a Silverface Vibro Champ that’s doing almost the same thing. It will whistle like that with the volume anywhere outside of the 3-7 range. I’ve placed a scope on the output and found no ultrasonic oscillations when the audible one isn’t present. I’ve checked internal lead dress, replaced all the usual suspects for a recap except for the filter can cap as it tested good and subbing in a new cap for each section didn’t change anything. Also, the grounding is all factory. Would following these same steps be feasible, or would you look at something else?
Numerous grounds for divorce but Judge T Dayton ruled guilty to the noisy plaintiff. :-)
I like you Man, U funny!
@@d-labelectronics Thanks Terry, You're the reason I subscribed.
Why does everyone say tubes clip “softly”? Every time you put a vacuum tube amp on the bench and turn up the volume, the wave forms clip pretty hard in the same fashion they say transistors clip.
Thanks for the video.
I know this video was 5 years ago, but I am hoping you answer this question. I am thinking of building a couple of these amps. My experience with DIY electronics kits is that the builder of the kit thinks he needs to you the cheapest crap available to build their kit. Personally, I am in the opposite camp. If I am going to build a kit, I want to build it better than original. How do I put to together a kit that fixes the problems and uses all the best components. FYI I am a mechanical guy not an electrical one. How do I build this into a Head? Can I replace the power cord with an IEC power connector? Who makes the best components? I would rather piece this thing together from parts then buy a kit, where I need to replace 90% of the parts. Can you help me out?
Thanks for the tips! Appreciate it.
How much to build one for me, please?
Respectfully-
Max
I could do with your experience as I am troubleshooting a 5E3 with odd voltages the cathode reading its 36v as to recommend 22v and b+ is down from the 6v6s. If you do Skype session then it would be appreciated.
This is a kit ? Where do u get one and about how much?
That's odd about the feedback. I've seen a ton of 5F1 builds and almost all of them have the output jack located between the 12AX7 and the power tube without squealing like this one.
See, I was 95% sure it was the NFL problem. Hooking the OT up the wrong way round turns it into a positive feedback loop and causes just that problem. Still kinda think that's what it was and during the process of moving the speaker jack to a different location that wiring error was corrected. Never heard of the speaker leads being close to the 12ax7 on a 5f1 cause it to feedback. In fact, I've just wrapped them around the 12ax7 in my 5f1 and there were no issues. Not trying to be smart or anything, 5f1s are wild beasts and each one is different :P
Roger that. The low side lead was soldered directly to the transformer frame, so no way to reverse the windings. Never heard or experienced polarity to Class A output transformers.
great !!!!!!!!!!!!!!!
Who makes a good amp kit for a beginner?
If you run across this problem and you triple checked your wiring, component values, solder joint inspections (especially the grounds-then try swapping the output transformer (OT) leads. In other words, swap the red and blue OT wires. I occasionally run into this issue on all types of builds and OT replacement jobs. This is a great little amp for anyone 8 to 80 and the absolute best amp for a person wanting to build there own amp. Here's another tip:
Don't cut those OT wires too short until you've got a functioning amp. Good luck ya'll!
I agree, swapping the wires to the output jack at the transformer output can reduce internal feedback. An oscillator (feedback) requires a nonlinear device, a feedback loop 180 Degrees out of phase, and sufficient gain to sustain the oscillaton. I learned this from my vintage 1976 Radio Shack 150-in-1 electronics kit and in high school electronics. When I design amps, my inputs/circuits are on one side of the chassis and the outputs/circuits on the other side going left to right. He you ever noticed why Fender amps put the tone controls in reverse order: Treble, Middle, Bass from left to right? That is that is how the circuitry is laid out and routes to the controls with the shortest path (no crossing over each other). It just a sound (no pun intended) method to reduce noise, not just be different.
Ideally, the controls should be right next to the circuitry, but it is not practical to open up the amp to make a tone change, so the potentiometers are mounted away from the circuitry and on the front chassis for obvious reasons (albeit a bit more noisy).
I leave my OT leads on the output side as long as they come. I twist them 3 twists per inch and then extend them to the Output jack using twisted wire of the same guage with heat shrink over the splices. Then I route that 'orthogonally" along the chassis (which is my ground plane) to the Output jack. As long as I keep the wires well twisted and not running nearby or parallel to any other circuits/wires, and it being near the ground plane, all work together to prevent coupling into other circuits.
I also use Teflon jacketed wire like what is used in military system. The Teflon is difficult to strip, but it does not met until about 900 degrees F, so if you touch it with your 750 degree F soldering iron it will not melt or shrink. Of course I use all white wire because Taflon wire is expensive and keeping the rainbow decade of colors is very expensive.
Genius!!! 👍
Something tells me I'm not going to figure out my whistling tubes (which sound identical to these). Since the amp is a proven design, I doubt that moving things around will help.
The first thing to do is put the tube shelf on !
Nice!!
Hey man I'm totally stumped I've built this kit and I'm not getting any secondary voltage from the power transformer to the 12ax7 or 6v6. Could anybody help me out? I've double checked the wiring, solder joints, continuity and ground.
Did you ever figure out why?
@@almonzowilder4091 nope. And mojotones amp tech customer service is worthless. Currently have a $600 paper weight lol
@@justinprince222 UH oh. So far I have a paperweight too. I guess I'll try to rearrange stuff. So disappointing.
Man, that's a strange problem. I'd like to know how the terminals are labeled on the primary and secondary side. It seems like little can go wrong with these transformers, right?
👍👍
Where was this vid a month ago when i had this verry problem lol
Hello, did you get yours running?
Ain't gonna tell us what you did to fix it?
Another great video Terry!! I have not seen the speaker output from an RCA jack?
The tweed amps had both RCA and 1/4" phono terminals throughout the 50's and 1960. Most famous would be the 5F6-A 4X10 Bassman. It uses four RCA terminals, instead of parallel wiring and a single phono jack.
Stinking nuts, is that a technical term?
I really don't like the way those tubes stick out of the back of the chassis like that. Makes it very awkward to build this thing into a cabinet.
It all makes sense, but not sense as we know it, Captain...
JJ is the only new 5Y3 that won't deliver 5AR4 voltage. Thankfully they're cheap!
I know the Sovtek's 5Y3 over-voltaged, but everyone else's?
DeadKoby Everyone else is made in the same factory as the Sovtek. It’s possible a more recent Sino 5Y3 is okay but I cannot confirm.
The JJ reads the exact same unloaded voltage as my JAN GE 6087. Loaded voltage is within 5% in a 5E3 clone.
Its either a crappy kit design or crappy directions ? These kits are costing the owners a lot more money ,because they need a expert like D labs to fix it.
Great info. Thanks Terry .
It all makes sense, but not sense as we know it, Captain...