TRAYNOR YBA 1A issues

[Turbocharbo]

Hey guys!

My Traynor YBA 1A MK2 has been acting funny as of late. It seems to have lost quite a bit of headroom making the low end distort. I play bass guitar through this amp and most notes on my E string sound overdriven. There is still headroom (not as much as before) but tonally it's sounding distorted. I had it looked over by a tech and it did make it sound better. The underlying issue is still there though. Here's what he did:

-new tubes
-checked pre-amp tubes
-re-biased
-caps changed (not the cap cans)

I've tried this amp with different cabs (both 4 and 8ohms), different basses, different speaker cables, different power and preamp tubes and it still sounds the same... I don't know much about amp repairs so I'm kind of at a lost here, do you folks have any ideas on what the issue could be? The cap cans maybe?

Turbo

[M Fowler]

Output transformer maybe has gone bad.

[xtian]

He did not replace the main filter caps? That's next!

[gui_tarzan]

Agreed. Which caps did he change? I have one of those too and after 40+ years those filter caps should be changed.

Did he happen to check voltages on the tubes and power transformer? Plate and screen resistors on the power tubes?

[martin manning]

Any known reason why the cap cans weren't changed? Not that they aren't due, and it would probably improve the sound if they were, but I'm thinking like Mark and suspecting the OT.

[Stevem]

I kind if hate to say this, but the 1972 Traynor that I have been working on with a tremolo issue has its original 1st and 2nd power supply filters and they test fine for ESR so the owner wanted me to leave them in, so there they stay!
That being said it does not mean that if your filters are not the issue that replacing them, or at least the first one with a larger, doing that will help keep the bottom end nice and tight!

[C Moore]

Here's what he did:

-checked pre-amp tubes

-caps changed (not the cap cans)

I am NOT saying this is your cure, but anytime I see the word "checked", I always wonder the same thing.....how did he check them.?
Others have said, but if the can caps are original, or 20 years old.......
good luck