# Traynor YBA-1 Tubes



## Bohdan (Jan 19, 2012)

Hello,
I recently bought a '69 YBA-1, no choke, amp. It came with 6550 tubes and sounds amazing with them, is this correct and what harm can it do? I stuck 6l6's in it, and it worked... I'm asking because my other '68 YBA-1 runs el34s. Can someone tell me what's correct for this era of amp? Thanks, B


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## Jeff B. (Feb 20, 2010)

The really early ones originally came with 7027A tubes before Pete changed to 6CA7 power tubes which was the North American counterpart to the EL-34.
Yours likely came with 6CA7's of which the EL-34 is a drop in replacement. I have 3 (one of which is a 68 I think) and they all came with 6CA7 tubes. 
I really like KT-66 tubes in my main one.

Some Trayor links:
http://www.lynx.bc.ca/~jc/traynorSchmArchive.html
http://www.0rigami.com/vb/index.html


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## Bohdan (Jan 19, 2012)

Hey Jeff, thanks for the info! I slipped in some EL-34s into, and no sound was heard... I'm assuming some modding was done to accommodate the 6550s...
BTW, I bought one of your Firing Line MKII pedals back in May or so. I toured it to the east coast and back. Great fuzz!!


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## Jeff B. (Feb 20, 2010)

Yup. Sounds like it was changed to accommodate the 6550's. Thanks for the nice words. I think yours was the last handwired version before I started using PCB's. If it's #007 I think that was the last HW one. 




Bohdan said:


> Hey Jeff, thanks for the info! I slipped in some EL-34s into, and no sound was heard... I'm assuming some modding was done to accommodate the 6550s...
> BTW, I bought one of your Firing Line MKII pedals back in May or so. I toured it to the east coast and back. Great fuzz!!


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## Scottone (Feb 10, 2006)

can you post a close-up of the wiring to the power tube sockets. Would probably be a quick wiring change to put it back to EL34's. 

Interesting to hear that a '69 doesn't have the choke. Was it stock, or does it look like somebody removed it later?

I actually have a YBA-1 choke kicking around if you need one.


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## Adicted to Tubes (Mar 5, 2006)

They sound fine with or without chokes.If you find it a bit barky a choke may smooth it out a bit but I rather like those big lugs without the chokes.


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## Bohdan (Jan 19, 2012)

*Jeff B.*, I can't recall what number it is, but it's definitely a handwired one. Beauty pedal.
*Scottone*, I'll take a photo of the circuit when i get back, I'll be away from it for a bit. I believe this amp is a later '69, right before the bumper version. The circuit looks mint. It sounds great with 6l6s right now, which I don't mind. The screen resistors look to be the original ones, 470ohm/10watt I believe. They got pretty hot with the 6550's, but no red plating or anything with the tube itself. I've read up on transition versions that don't have the choke, but still have the pre-bumper box. I kind of like have one YBA with a choke, and one without, gives me some variety amongst them. 
Thanks for the info guys.


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## Bohdan (Jan 19, 2012)

View attachment 625
Here is one picture that I took a few days ago. Can't really see too much detail in it, I have since the hack 3-prong job on it. Pins 1/8 are soldered together and to ground on pwr tubes.


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## Scottone (Feb 10, 2006)

yep, looks like the transition model alright. I'm guessing that a pretty high bias voltage was set to accommodate the 6550's, so the EL34's are effectively biased off when you plug them in. The bias resistor (between the two bias caps) looks new.

I always added a bias pot to the fixed bias Traynors that I owned in the past. That way, you can bias it to use EL34's or 6L6's


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## Jeff B. (Feb 20, 2010)

Bohdan, if you need any pics or info, my late 60's (1968?) YBA-1 is already somewhat apart and patiently waiting it's turn on my workbench.


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## Bohdan (Jan 19, 2012)

Awesome thanks for the info guys. Do you think the original screen resistors are sufficient enough for the 6550s? Jeff, I'd love to see some ref photos. I also have a 68 but is heavily modified.


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## Scottone (Feb 10, 2006)

I just went through my collection of Traynor schematics and found the one for your amp. Yorkville Sound sent me these back in the early 90's before everything was on the internet 

One of the 470 ohm 10 watt resistors replaces the choke in the power supply and the other is a shared screen resistor for the power tubes. IMO the shared resistor should be fine for the 6550's, but you could also upgrade to individual 1.5K 5 watt resistors if you like.

I could try and scan the schematic and send it to you if you need it.


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## Bohdan (Jan 19, 2012)

Hmm. Ok should be good then. I'll play those 6550s without worry then. I should be good schematic wise, they're pretty plentiful online I see. Thanks for all the circuitry knowledge!


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## Scottone (Feb 10, 2006)

Bohdan said:


> Hmm. Ok should be good then. I'll play those 6550s without worry then. I should be good schematic wise, they're pretty plentiful online I see. Thanks for all the circuitry knowledge!


That's what I would do....The only thing that I would change is the power cord installation. I don't like Mar connectors in an amp chassis 

Thanks for posting...the "transition" models are intersting


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## Bohdan (Jan 19, 2012)

Heh no problem Scottone. I soldered the cord in there and removed the ground switch completely. I'll post some more high def pics on here, just for reference.


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## Jeff B. (Feb 20, 2010)

Bohdan said:


> Awesome thanks for the info guys. Do you think the original screen resistors are sufficient enough for the 6550s? Jeff, I'd love to see some ref photos. I also have a 68 but is heavily modified.


 You can get by with the stock arrangement but I would change it to individual 1K 5W screen resistors next time you plan on working on it or upgrading it along with some other changes.

Pics of my 68 probably won't be as much help for you as I originally thought. I took a good look at it last night for the first time since getting it and it's been a bit hacked at by a previous owner.
The standby switch was destroyed and taken out of circuit, and a second "death cap" was added to the ground switch and who knows what else. I did find it in somebody's garbage pile so I shouldn't be surprised but it's nothing that can't be easily fixed when I get some extra time. I can email you the pics if you still want them. There is too many large pictures to post and I wouldn't want a casual lurker here to think that it's supposed to be wired like this and then do it to their amp without knowing any better.

Adding a .68uF cathode bypass capacitor to V2, lowering the second channels brightness cap value (or putting a couple of them on a switch) and adding push/pull switched pots to defeat the negative feedback and to lift the ground for the tone stack (extra gain) are good starting points for simple mods.


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## Bohdan (Jan 19, 2012)

I'll put those screen resistors in I think, but leave the rest of it stock. It's considerably brighter/less dark than my 68. Prob change out the volume pots too, 4 megs are still in there.


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