'71 Traynor YBA-1 - Plexified this past Saturday ** CLIP **

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Riffraff

Riffraff

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I snagged this a few weeks ago. I've got parts on the way to do some Plexi mods. Should be a ton of fun.
This thing is brutally loud. :lol: :LOL:

Here's a pre-mod clip. Les Paul straight into the bright channel, volume maxed.

 
I had one of these too! Much messier than yours where the guts were considered. Needed a few new filter caps and I installed a three prong grounded power chord as I got a shock when I tried mine for the first time. I did some Plexi-ish mods to mine as well... I can't remember what I messed with but I did them a few at a time because some sounded horrible. Anyway, in the end it was clear, crunchy, thumpy and articulate. I wish I still had it some days. Kind of felt like it was between Plexi and Hiwaat crunch. Took pedals like a champ. Was very loud. ..VERY loud. :thumbsup:
 
Cool amp. Interested to hear what the mods do. It sounds good , but could use some more "crunch" imo.
 
This is the plan:



Service related

Addition of variable bias if it hasn’t already been done.

A) Filter cap replacement, two 2 x 50uf /500V cans to replace those 2 x 40uf dynamite sticks

Plexi mods

B) Replace 4meg volume controls with 1meg volume controls
C) Replace 100k mixing resistors with 270k
D) Tone stack shift – replace .01 & .1 caps with .022 caps
E) Tone stack shift – replace slope resistor with 33K & replace 320pf cap with 500pf silver mica cap
F) Replace 100K feedback resistor with 47K – 27k for gain bump

It looks like the parts are out for delivery today so I'll be messing with this over the weekend. :D
 
f) Shouldn't increase gain.. it will increase sag for more squish and shave some of the grittiness off the amp in my experience doing it with this amp and my JCM800's. Good mod though.
 
I'm going to do the filter caps and the volume controls first and then do the rest one at a time tone testing after each one so see if I like the effect or not. The amp re too dark with humbuckers. I made the clip with the treble and High range controls all the way up and the bass and low range controls all the way down. Making them a little more usable would be a good thing. I'm not really too motivated to increase the gain too much, may be a bit more Marshally but still in the Plexi range. I don't want to bastardize this too much because I like it for what it is. A nice smooth bluesy overdrive would be perfect. I can always boost it for more grind and I've got other options for heavier stuff.
 
sounds great! I'd grab an attenuator and an SD-1 and call it a day with that thing! Well I'd probably try the mods too... :lol: :LOL:
 
I've got both. The parts came yesterday, now the fun begins. :thumbsup:
 
I got my parts delivery the end of last week and couldn’t wait to get into it. I went out in my barn at 5 am Saturday morning to do the mods to my YBA-1. It was 25 deg and I froze my ass off but it was worth it.

Here is the before picture:



And the after (picture taken before I added the cathode bypass cap and changed the feedback resistor):



The work done:

I installed long overdue new filter caps.

I removed the 470k linear volume controls and put new 1 meg logarithmic volume pots in their place. I used a switching pull pot for the bright channel to control some preamp changes.

I swapped the 100k mixing resistors replaced with 220k. Antique Electronic Supply was out of 270k and naturally the local Radio Shack didn’t have them either so I used the closest value I had.

I replaced a .1 cap in the tone stack with a Mallory .022, replaced the slope resistor with a 33k and swapped out the 320pf cap with 500pf silver mica. That makes the tone controls a lot more useful.


I connected a 2.2k resistor and a 22uf cap to the switch on the pull pot which connects parallel to V1B's 1.5k cathode resistor when pulled. That provides a nice gain bump when engaged and is at stock value when off.

Lastly I replaced the 100K feedback resistor changed to 47k.
Everything is working perfectly. The volume controls are no longer on/off controls and the amp has definitely shifted to the Marshall camp in the tone department.

Here’s my frozen fingers the test clip through a V30 loaded 212 cab. :lol: :LOL:
Les Paul straight in, no pedals at all.

 
Dig it.. has the edge of blowing up sound and def has some bass thump. I think I had tuned mine for a little more slice and less gain because as I am sure you have noticed, it can get pretty crazy out of hand fuzz/distortion if you try to squeeze too much gain. At one point I think i had some very bad blocking distortion and it just screamed and hissed. Cool amp for what it is though. I think it would benefit with a choke for sure too.
 
The early versions had a choke. I'm not sure what year they took them out but it was probably not long before my '71 because the '68 & '69 models had them. I've seen a lot of guys adding them. I didn't make mine super gainy either because I still want to be able to push it with clean set OD pedals like I used to do with my 1959SLP.
 
It's doing that Plexi thing with a clean set SD-1 smashing the front end.

 
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