Monday, March 26, 2012
Reviving a Traynor YGM3 Guitarmate
While I was scrounging through Craigslist the other day looking for bargains and oddities I saw a listing for a non operational Traynor YGM3 Guitarmate and made arrangements to snag it, as I'd never owned one before. Plus, it was cheap.
It's a 15-20w single channel amp with reverb, tube modulated tremelo ala Princeton Reverb, and a single 12" Marsland speaker in a closed back cabinet. The circuit is straightforward with no magic tricks or secret sauce, either.
On getting it home I found out that it actually did sort of work but it needed some serious attention. After installing the mandatory grounded power cord, replacing the broasted power tubes, and tidying up some bodged 'repairs' I set about measuring the operating parameters of the amp.
As it's a fixed bias number I patched in some 1 ohm cathode resistors and measured cathode current-I was stunned to find the power tubes were running at about 38 ma each-about double the safe limit of 70 per cent dissipation for EL84 power tubes.
I installed an adjustable bias pot inside the amp that replaced R39 with a 25 k pot and an 18k resistor to ground. Measuring plate voltage at around 400v told me that the safe number was about 20 ma or thereabouts, plenty for the JJ EL84s that went in. I'd consider this more or less mandatory. I'd heard these amps fry power tubes and now I believe it.
Looking at the FP type Mallory filter capacitor cans I decided on a pair of JJ LCR style cans and clamps that had the benefit of being about eight bucks a copy rather than the thirty five dollars apiece that FP cans would cost me. Removal of the Mallorys required large quantities of heat from my old Weller ray gun and lots of scraping with acid brushes. I got most of the old solder off.
Installation of the clamps is straight forward, requiring only some 1/8 holes and self tapping sheet metal screws. I did get the clamps a little off center but as only the ground lug of the new cans intruded I left it alone and ran a separate ground wire for good measure
Last, I cracked open the sealed cabinet and dumped in a 70w Fane from out of the carcass of Larry, my old Weber amp cabinet-which now, because he has a new tweed cabinet from John Hinsdale, is in the trash bin in pieces.
The results were good. It's loud and clean, almost Voxy, and the tremelo and reverb make you think somebody at Yorkville was thinking of the sun drenched surf beaches of California when they cooked this amp up.
The proof of its enduring popularity is that it's been reissued. And, it has been ass tested and found good by my resident amp qa technician, Madam Zelda.