Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plumcrazyfx on July 22, 2018, 10:09:30 am

Title: 72/73 Traynor Bassmaster Questions
Post by: plumcrazyfx on July 22, 2018, 10:09:30 am

So I have a late 72/early 73 Traynor YBA-1 Bassmaster that I'm working on.  I am in the process of replacing the original Mallory 40/40uf cap cans with a pair of 50/50uf F&T cap cans and relocating the Pre/PI grounds to the input jack.  A previous tech replaced the bias caps, replaced the 39K to ground in the bias circuit with a 33K resistor in series with a 10K pot, defeated the ground switch, pulled out the accessory power jack, and put in a 3 prong cord.  This isn't totally original since he drilled the chassis for the bias pot and I drilled it to put in cap can holders so I'm not afraid to do little things that slightly change the originality.

This particular YBA-1 is late 72 or early 73 so it has a smaller output transformer (about the size of a Tweed Bandmaster transformer as far as I can tell - significantly smaller than the one in my early 72 or my 69 YBA-1s).  It also has no cathode caps on the first 12AX7 whereas the early 72  has the 250uf caps.  I think it is mostly original and since I have the others I'm interested in keeping the character of this circuit compared to the others.  However, I want to make sure to do anything I can to make the amp reliable, make it not eat tubes, or do anything that will be dangerous to me or the amp.  I know they are loud amps so I will be running it hard with an attenuator to get any breakup.  I know it originally had Mullards but I'll probably be using EH 6CA7s so I want it to be reliable with new tubes.  There is one thing that concerns me is the shared 470ohm 10 watt screen resistor.  Would it be better to also add a 2.2K resistor to each tube for additional dropping or is that being overly careful?

I'm looking for any suggestions to make the amp more reliable/make it play better while retaining the original character.  Thanks!

Title: Re: 72/73 Traynor Bassmaster Questions
Post by: sluckey on July 22, 2018, 11:34:02 am

Quote

I know they are loud amps so I will be running it hard with an attenuator to get any breakup.

This will certainly knock a few percentage points off the reliability.

Title: Re: 72/73 Traynor Bassmaster Questions
Post by: plumcrazyfx on July 22, 2018, 04:17:12 pm

If I play it on 6 with or without an attenuator- is one worse?  I know one is worst for the ears and wifey.