# '76 Traynor YBA-4 problem diagnosis!



## the-patient (May 19, 2009)

Feb 24 EDIT: 

So I'm just now coming back to this amp after a while working out of town. I can safely say the speaker is fine, as the sound is related to rattling and any movement by the tubes. I'm gonna retension the tube sockets tomorrow, but I've (poorly) recorded a bit of audio, to see if anyone can help me diagnose the problem more easily.

These sounds occur when you tap any of the tubes, or bang on top of the amp. Any thoughts on what could cause this? They also happen whenever a low note is played on the guitar (excessive vibrations, i guess.

[SOUNDCLOUD]https://soundcloud.com/kuru-1/amp-noise[/SOUNDCLOUD]



Hey guys,

I have an old YBA-4 combo, with a 15 inch speaker, but it's making a pretty terrifying sound lately!

It's what I'd describe as tearing... It really sounds horrible, like an extended crackle, that happens over 500ms or so, specifically around Eb on the freeboard of both bass and guitar.

I feel like it isn't the speaker, since it happens at low volume as well. It reacts to the output of the guitar - that is, with the volume rolled back a little bit it doesn't seem to happen as much, but when I'm dimed, it seems more apt to happen.

Any thoughts on what could be the root cause of this? Anything I can do to help better describe it?

I'm comfortable around an iron, high voltage circuits, and schematics, but I don't know a thing about diagnosing these kind of issues!

Thanks in advance for your time!

Dylan


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## keto (May 23, 2006)

Capacitors aging/drying out/dying would be my first guess, tubes my second. Lastly, given you state it's at full out, could be the speaker dying.


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## bolero (Oct 11, 2006)

maybe a dumb question, but did you try using a different patch cord? and a different guitar?


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## the-patient (May 19, 2009)

Sorry, I misspoke! 

I would never have a reason to put the amp full out, it's effin loud! I mean with the guitar's pickup output full out. 

The tearing happens down at 10% volume on the amp. 

Would it specifically be electrolytics and or filter caps that would prone to drying out? 

I've replaced everything in the chain other than the amp, tubes, and speaker.

Sent from my SAMSUNG-SGH-I747 using Tapatalk


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## loudtubeamps (Feb 2, 2012)

After elimating the obvious as mentioned earlier I would (only if you are comfortable doing so,) suggest re-tensioning the tube socket clips.
If the problem remains then replace the tubes and if the problem still persists,having a look at the components inside initially for signs of bad solder joints or damaged/cracked resistors (plate and O/P screen).Look for a component that is sensitive to mechanical vibration.
Cheers, d


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## the-patient (May 19, 2009)

Good thought!

She needs some TLC, so I'm gonna source out some filter caps regardless, but I'll definitely look into the tube sockets. 

As always, I'll be safe when going in!

I'm thinking about getting this baby converted into a head one of these days, and possibly installing a MV.


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## bcmatt (Aug 25, 2007)

I would really want to eliminate the speaker as the possible cause. I messed around with a combo I had built forever, assuming i had wired badly until I finally found a tiny rip in the speaker cone causing all the "staticky fizz". i'mnot saying that it has to be your speaker, but it is an easy thing to test if you can find another can around to borrow.


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## the-patient (May 19, 2009)

Fair enough. No harm in eliminating all of the possibilities right from the get-go before getting down and dirty.


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## the-patient (May 19, 2009)

So I'm just now coming back to this amp after a while working out of town. I can safely say the speaker is fine, as the sound is related to rattling and any movement by the tubes. I'm gonna retension the tube sockets tomorrow, but I've (poorly) recorded a bit of audio, to see if anyone can help me diagnose the problem more easily.

These sounds occur when you tap any of the tubes, or bang on top of the amp. Any thoughts on what could cause this? They also happen whenever a low note is played on the guitar (excessive vibrations, i guess.

[SOUNDCLOUD]https://soundcloud.com/kuru-1/amp-noise[/SOUNDCLOUD]


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## Wild Bill (May 3, 2006)

Reading the thread again, I don't see any mention of microphonic tubes. Frankly, that would have been my first suspicion!

Especially when you say the noise comes from hitting the top of the amp or any vibration.

Preamp tubes often go microphonic all the time. The problem is worse with some of the modern manufacturers that may not tie elements down as well as they should inside the tube. All the heating and cooling makes things expand and contract and elements can develop a little "wiggle room".

At that point, the tube can act like a microphone! It will make all kinds of noises as it picks up vibrations. In extreme cases, you can shout at the tube and actually hear your voice coming out of the speaker!

The test is easy - just take a pencil or a plastic pen and gently tap each preamp tube. If one has gone bad, you will immediately notice a loud "ping" sound. Sometimes a tube can be so sensitive that it can be hard to isolate the one with the problem, since tapping ANY tube will generate enough vibration through the chassis to "ring" the bad one. Also, you can also of course have more than one microphonic tube!

When you find a microphonic tube, simply replace it with a good one! That should solve the problem.

It is possible for parts to become microphonic as well, but this is much more rare. Troubleshooting is done the same way, only with the amp opened up so you can gently tap the parts. It goes without saying that you should be using something insulated, like a plastic pen. I wouldn't use a pencil - high voltage will easily travel up the lead in the centre. I guarantee that might HURT!

If you have already tried this and my post is all "old hat", please consider the immortal words of Gilda Radnor in her character of Emily Litella - "Never mind!" :banana:

Wild Bill/Busen Amps


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## WCGill (Mar 27, 2009)

You need to remove the chassis and check for damaged, bad components or wires and/or cracked solder joints as per Loudtubeamps. Definitely not a microphonic tube.


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## the-patient (May 19, 2009)

I figured it wasn't a microphonic tube my first time hearing that sound. It's a bit too intense to be a symptom of that problem. 

I'm going to trying snugging up the tube sockets, looking for oxidation on solder joints, and trying to clean some oxidation out of the sockets as well.

Multimeter needs new batteries so I'll have to resume my search tomorrow. I'll keep you guys updated!


Sent from my iPad using Tapatalk HD


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## Wild Bill (May 3, 2006)

the-patient said:


> I figured it wasn't a microphonic tube my first time hearing that sound. It's a bit too intense to be a symptom of that problem.
> 
> I'm going to trying snugging up the tube sockets, looking for oxidation on solder joints, and trying to clean some oxidation out of the sockets as well.
> 
> ...


Well, I've heard microphonic tube problems that were VERY intense! Perhaps your assumption that it can't possibly be a tube is right.

Still, when it is so easy to check by simple substitution if it were my amp I would do it just to put my mind at rest. 

If I had a dollar for everytime I made that kind of assumption, only to find after wasting hours that it was a tube all along...

I've always believed that the Murphy who wrote Murphy's Law was an optimist.

Wild Bill/Busen Amps


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## the-patient (May 19, 2009)

Wild Bill said:


> Well, I've heard microphonic tube problems that were VERY intense! Perhaps your assumption that it can't possibly be a tube is right.
> 
> Still, when it is so easy to check by simple substitution if it were my amp I would do it just to put my mind at rest.
> 
> ...


You make a GREAT point... I don't know how many times I've thought my guitar wasn't working, and checked my cable, even though I just habitually turn my guitar down - always start at the closest link in the chain!

Thanks for your input.


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## the-patient (May 19, 2009)

Another update! So I replaced the tubes, and they were definitely not the problem. I have a cell phone recording of the same noise again, but it seems worse!

This i'm I'm actually playing rather than banging on the amp. It almost sounds like something is arc'ing. Next step, I'll drain the filter caps, check with my multimeter for safety, and then try to tighten up the tube sockets and look for oxidized points. It seems to be worse on the "high" inputs.

[SOUNDCLOUD]https://soundcloud.com/kuru-1/new-noise[/SOUNDCLOUD]


Also note: i get the same noise when tapping on the pins for the power tubes


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## the-patient (May 19, 2009)

In case anyone's interested, I've solved the horrible arc'ing sound problem!

There were three things wrong that I found when poking around with the ol' chopsticks. First, a loose connection from the big 10w resistors to a filter cap. Second, an oxidized connection on pin3 of the v1 12AX7 - just a quick reflow of the solder to fix that. Lastly, and I think this was the source of the big problem, a loose ground connection on the volume pot in channel 2. When I was poking around it got knocked right off, and hot damn the sound coming out of the big 15" speaker just about blew my head off. 

There's still some pretty brutal 60 cycle hum, and I think it's from old input jacks. I don't think they're shorting out properly when they're unplugged. Thanks for the help everybody! Much appreciated.


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## greco (Jul 15, 2007)

Congrats!! Thank you for the update. 

Those VERY loud and totally unexpected noises scare the $HIT out of you, don't they.
I did a similar thing with a frequency generator into an amp....LOL

Please let us know if the adjusting the input jacks results in lower 60 cycle hum.

Cheers

Dave


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## the-patient (May 19, 2009)

So, 

Swapped out the jacks, and no luck. I've actually realized that it's 120hz hum, more so than 60. If I remember correctly, that indicates that my filter caps need replacing, right?

Anyone know of a supplier in the London area? Or anyone in London have some parts? 4x 40uf/450v electrolytic caps.


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## Wild Bill (May 3, 2006)

the-patient said:


> So,
> 
> Swapped out the jacks, and no luck. I've actually realized that it's 120hz hum, more so than 60. If I remember correctly, that indicates that my filter caps need replacing, right?
> 
> Anyone know of a supplier in the London area? Or anyone in London have some parts? 4x 40uf/450v electrolytic caps.


Oh dear! We really should have checked that out first and not wasted your time! 120 hz indicating filter caps is pretty basic.

You can always call up www.thetubestore.com - Your online source for audio tubes. in Hamilton. Great guys! Canadian!

Electronic stores that still have counters are scarce as hen's teeth these days. Stores that carry parts useful in tube amps at tube voltages are even rarer.

I'm not saying you won't find one in London but I'm sure glad it's you looking and not me! I spent my career selling industrial electronic parts and I know that world quite well.

thetubestore.com will ship same day and you will have them tomorrow. I would buy Illinois 47 mfd @ 500 vdc. They are modern design, which means they tend to last longer and are smaller than the old caps. This can be a blessing inside a cramped and crowded chassis!

Wild Bill/Busen Amps


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## loudtubeamps (Feb 2, 2012)

I would double check the connection on the filter caps in the bias section .If they are solid then I would replace these first and see if your 120 cps hum drops.
d


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## the-patient (May 19, 2009)

Wild Bill said:


> Oh dear! We really should have checked that out first and not wasted your time! 120 hz indicating filter caps is pretty basic.
> 
> You can always call up www.thetubestore.com - Your online source for audio tubes. in Hamilton. Great guys! Canadian!
> 
> Wild Bill/Busen Amps


Ahh well! Live and learn. This is more of a learning project for me, and the jacks did reduce the low hum, but the higher hum remained. I don't mind flopping around like a fish out of water on this, it's a fantastic way for me to begin to learn and understand the whole process.




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## the-patient (May 19, 2009)

Also I checked the connections LoudTubeAmps and they seem fine. I figure at 6 bucks a piece I may as well replace all 4. 

Ordered my caps! Can't wait to swap them out.

Again thanks for all the suggestion guys, this is just a project for me and I'm not under time constraints so I'm having fun fucking around and just making the old beast better.


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## the-patient (May 19, 2009)

So, 

New filter caps installed - 120hz hum mostly gone, but now I can *really* hear the 60hz hum... kqoct

On to the next thing.

Here are the voltages I measured:

preamp tubes:

V1a 223.5 (schematic says 225)
V1b 224 (schem says 255) (loud crackle when I test this one.)


V3a 261.3 (schem says 265)
v3b 264.8 (schem sys 245)

Power tubes:
V4 441 (schem says 433)
v5 439 (schem says 433)


Does this give anyone any hints? Could it simply be bad tubes? I've tried swapping them out one by one to no avail, but should I try popping them all out? Ask me if there's any other info I can/should provide.


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