Traynor Signature YGA-1A

cancon

Member
2011-03-06 2:58 am
I have a cool rare-ish "Signature" Traynor head on the bench, same as the Bassmaster amps but with Trem instead of the Mid-range expander.
The tube chart lists 6CA4 (EL34) tubes and I believe this amp was built around 1968.

What's in front of me differs slightly from the schematic, namely a mystery component wired across the plates (GE, picture attached) which I assume is a high voltage capacitor, any takers? The two 470ohm screen resistors (R29, 30) are not present, instead a single 20W 1K resistor is wired in series with the screen supply voltage.

Also, the filter cap values on the schematic also don't match, I'm a little confused about how to approach a re-cap and could use advice.

The first 80uf cap is present (C21), internally. The two multi-cap units are both 80@450, 30@450, 20@450 and 40@150. On each can the 30uf tap is not connected. Next, where we see C22 and C23 on the schematic (40/450 ea) are actually 80uf/450, 20/450 and 40/150 wired together.
After the choke, C25 is 80uf/450, C26 is 20/450 and C27 is 40/150. Kind of strange including the 150V caps in these arrangements?

This seems like a run-around to try and re-produce exactly. If I can manage to get the cans out of this chassis and install some twist-lock brackets, a few available CE manufacturing options could available (at 525V instead, probably not a bad idea).

Any tips would be appreciated, thanks!
 

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turk 182

Member
2012-10-26 3:03 pm
sounds like your amp has had some work done to it to convert it from the original tubes which where 7027a's.
what's it currently running for output tubes?
the "mystery part" is supposedly a transient suppressor (a diac anti-parallel diodes or something along those lines) most consider it a tone killer.
i would (if your output tubes are 6L6) reference the bassmaster mkII schematic as a guide on sorting this one out.

if you look at early bassmaster schematics you'll see the "mystery part"
 
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cancon

Member
2011-03-06 2:58 am
Thanks for the reply,
I just spent the morning pouring over old YBA schematics.
I do believe now that this amp was factory serviced in the early 70's, since the amp is running 6CA7/EL34 tubes, and the two can capacitor date codes point to mid '71. Super strange. The YBA MkII power supply does more closely resemble this amp with that suppressor, but it lacks the choke transformer. Since none of the schematics resemble the filter cap arrangement I have on the bench, I'm thinking of just re-doing it closer to the drawings.

Also, whats the verdict on the suppressor, can it come out? Should I drop in a .005/1600V orange drop across the plates instead?
 

cancon

Member
2011-03-06 2:58 am
I don't presume that it will affect tone one way or another, I'd be surprised if I heard a bit difference but will try it out.

The point of this job isn't to fix the amp, (well, the preamp has issues, but the rest seems to be OK). I want to improve reliability, starting with the replacement of stressed components. I'm a bit green with respect to this component's function and modern replacement equivalent.
 
Hey

In the Bass master chapter of TUT3 we show how to wire this amp for lowest noise and best note articulation. We take the circuit to "super stock" with individual bias adjusts and meter jacks for each tube, which allows easy bias setting, the use of alternate tubes, and of mixing tubes. Individual screen-stops of 1k-5W are preferred for MI.

DO NOT replace the can caps. leave them in place but disconnect them internally and use modern caps and correct grounding. The original grounding in this amp is very compromised even though for its gain it will seem "quiet enough". Tube amps can be much quieter than this.

Pete followed hifi design examples with his amps. Only he and Gar Gillies used the biased suppressor, which we call the "Canadian Connection" in our books, even though Mullard suggested it in their original notes for the EL-34. You can easily tie pins 1&8 together and ease bias setting.

Have fun