Yamaha T50 'production notes'?

[DonMoose]

This T50 I picked up over the weekend was modded by ... somebody, and I think they left something out.

There's a mixer stage that brings the loop back in on V4A and the reverb on V4B. The schematic (see Weird Voltages thread) shows these two triodes sharing a common plate and common cathode resistor.

There are two PCB trace cuts that separate the 2 plates and 2 cathodes. There is a second Rk tacked in (nicely done), but no second Rp - the loop return triode plate is just floating.

The schematic says something about Production Notes, page 14, and I'm hoping the answer I need is there. Anybody got a copy?

Thanks!

[DonMoose]

Went ahead and jumpered the two plates - now have HUGE clean volume in both channels, but the OD channel won't OD. With the preamp all the way up and the master on 0-1, it's crystalline. Above 1 on the master, it's LOUD but still clean.

Suspecting V2 or the OD half of V5.

[DonMoose]

Found another mod that took the reverb recovery triode straight to the PI (AC coupled, of course), which explains why the reverb controls acted more like volume knobs.

Now have a nice big clean and a very weak OD. Still looking for other mods.

[Wayne]

I haven't dealt with Yamaha re amp support, but I did contact them one time about a POS Yamaha guitar that I bought second hand in the 80s and am quite fond of. I sent an e-mail to their site's support link with a couple of pix attached, and before long I got a very detailed reply that included everything there was to know about the guitars specs. They guy who replied really went, or at least sounded like he went the extra mile to find out.

If that is any indication of their performance on customer service issues, drop them a line and ask about the production notes - you may luck out and get a service manual with mods, or at least some guidance.

Tried to find you a link, but could only find the Canadian one - I'm sure there's a corresponding US link you can use.

W

[JerryFJA]

Those were mods done by Yamaha to the original Soldano design. They moved the reverb return to come in after the EQ circuit. The later T amps had this done.
Jerry