Hi everyone,
I'm trying to get a Traynor YBA-1 bass head going again. Everything looks untouched inside, but the output oscillates in the audio frequency. This oscillation changes pitch depending on the settings of the volume knobs and the sound is affected by the tone controls.
Schematic can be found here: http://www.lynx.bc.ca/~jc/YBA1Schems.pdf (specifically page 6 of that PDF)
The first thing I always do is clean the pots, test that they work, clean and tension all of the tube sockets and test that the tubes work.
I tried to isolate the oscillation by removing tubes, and noticed that the oscillations stop with V2 removed. V2 seems to be just straight-up two stages of amplification after the volume control, but before the tone stack. I also tried moving around all of the lead dress around V2 but it didn't affect the oscillation at all.
So yeah, I'm pretty stumped on this one. Can anybody suggest anything else I can try?
Traynor YBA-1 oscillating!
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gui_tarzan
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Re: Traynor YBA-1 oscillating!
Did you swap V2 with another one? Also, check for poor solder joints on the tube sockets, bad caps, grid resistors, etc.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
"He's like a new set of strings, he just needs to be stretched a bit."
Re: Traynor YBA-1 oscillating!
I did swap V2 out with a new tube, with the same problem. Thanks for the advice on checking for poor solder joints, caps and grid resistors. I will do that tonight and report back.gui_tarzan wrote:Did you swap V2 with another one? Also, check for poor solder joints on the tube sockets, bad caps, grid resistors, etc.
Re: Traynor YBA-1 oscillating!
Failing filter caps can cause this too. Just solved on an HRD. Clip in a new 22uF cap across the existing filter caps, starting with the last one in the string. Remember to discharge your test cap after use!
I build and repair tube amps. http://amps.monkeymatic.com
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Leo_Gnardo
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Re: Traynor YBA-1 oscillating!
What xtian said ^^^. If the filter caps in that Traynor haven't been replaced since 40 more or less years ago, it's high time to do it anyway. Don't forget to put in fresh bias supply filters too. They may be small but if they go bad, kaboomski !!!
down technical blind alleys . . .
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gui_tarzan
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Re: Traynor YBA-1 oscillating!
Yep, that's what I meant when I added that about the caps, not just to check the solder joints.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
"He's like a new set of strings, he just needs to be stretched a bit."
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Stevem
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Re: Traynor YBA-1 oscillating!
Yup, X3 on the filter caps not uncoupling that gain stage as needed!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Traynor YBA-1 oscillating!
Hey guys, I had a can capacitor with a 10uF section so I jumpered that in as recommended and all the oscillation on the amp stopped!Stevem wrote:Yup, X3 on the filter caps not uncoupling that gain stage as needed!
I never thought of the filter caps, because I was under the impression that the only thing they did was reduce the ripple from the rectified AC. I didn't realize that they also decouple each stage, but of course that makes sense. Lesson learned for sure now.
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Stevem
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Re: Traynor YBA-1 oscillating!
There ya go, now replace very darn electrolytic in the amp and you might take a listen to placing a .22 uf and a .022 uf at 600 volt cap across the filter that deals with the first gain stage in the amp!
I would strongly suggest to you to up those first two power supply filters from 40 uf to 80 or 100 uf even if you have to use Marshall type can caps and silicone them down in the chassis some where away from the first half of the preamp section!
I would strongly suggest to you to up those first two power supply filters from 40 uf to 80 or 100 uf even if you have to use Marshall type can caps and silicone them down in the chassis some where away from the first half of the preamp section!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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gui_tarzan
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- Joined: Thu Jan 16, 2014 3:10 am
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Re: Traynor YBA-1 oscillating!
Why so high Steve?My YBA-1A has a set of dual 40 cans in parallel (80mfd) and then in series with an 80 to give it 40 mfd on each of the first two stages but a lot of reserve capacity. My understanding is the YBA-1 is a lower power version of the 1A, no?
Here's a picture of my cans mounted in the bases of the originals.
Here's a picture of my cans mounted in the bases of the originals.
You do not have the required permissions to view the files attached to this post.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
"He's like a new set of strings, he just needs to be stretched a bit."
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Stevem
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- Joined: Fri Jan 24, 2014 3:01 pm
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Re: Traynor YBA-1 oscillating!
You have stock a total of 80uf on the plates of the output tubes, is this amp converted over from the 5ar4 recto tube to SS diodes , if not than slip the added size caps I posted about.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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gui_tarzan
- Posts: 607
- Joined: Thu Jan 16, 2014 3:10 am
- Location: The 26th State
Re: Traynor YBA-1 oscillating!
On mine there is a can of dual 40s in parallel for 80, then that goes directly to a single 80 in series to make 40. That goes to the OT.
Then there is another dual 40 can wired parallel for 80 that is also wired in series to a single 80 to make 40. That one goes to the power tubes.
In doing research on mine I found a lot of various schematics, Traynor made a lot of adjustments over a few years on this amp so there are at least a half dozen different schematics for the YBA-1 and the YBA-1A like mine.
Then there is another dual 40 can wired parallel for 80 that is also wired in series to a single 80 to make 40. That one goes to the power tubes.
In doing research on mine I found a lot of various schematics, Traynor made a lot of adjustments over a few years on this amp so there are at least a half dozen different schematics for the YBA-1 and the YBA-1A like mine.
You do not have the required permissions to view the files attached to this post.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
"He's like a new set of strings, he just needs to be stretched a bit."
Re: Traynor YBA-1 oscillating!
Thanks for the advice guys, I think I'm going to leave the filter cap values as stock. From there, I'll take a listen to it and clip in some additional filtering and see if I prefer the sound.