Traynor YBA-1A help

[jerkass9879]

So, my amp blew a fuse a couple months ago and i just got around to trying to fix it. after I pulled the back panel off i notice one of the tubes was bad. Replaced both tubes with a matched pair of SED-EL34's, they were part of a matched quad I bought 6 months ago. I always have the channels jumpered and I noticed channel one was not working right and there was no headroom left so while playing i looked at the tubes in the socket that had the blown tube was glowing a lot more than the other. all of the preamp tubes have been changed as well. What could be causing this?

[BogeyBass]

Lots of possibilitys......the amp needs a good run threw and clean up
I think the first yba used 7027a and the mk2 used 6ca7 power tubes.....so ewww yuck toss those el 34's...

Not the problem thou...did you bias the amp after replacing the tubes? The plate resistors might be going south in the preamp if the channel is going dead....but if its the power tubes most likely the 1 watt screen resistors are bad...replace with new 470ohm 2 watt.
if you didn't bias the amp the idle current might be too high and really starting to test old resistors that were one the way out anyways.

Bad solder joints, dirty sockets, or bias caps are getting a little old.... most likely all the caps are drying out...the traynors run really high plate voltage....with new caps and 7027A's that amp will sound much better...

get a schematic and start testing the values of your plate and screen resistors....Schematic Heaven has it in the Bargain Binsection....dont let it hurt your feelings thats their dumb opinion....

[jerkass9879]

It was biased last time I changed the tubes. But the new tubes were matche with the olds. I figured it would be more of a pain than I had hoped. Thought I might get luck with an answer. I like the EL34's. Considering this has become my main guitar head since I fixed the v4b. What tubes do you run in yours? And thanks for the help

[BogeyBass]

I have a Mk 2 so i ran 6CA7 after spending some time and money on fixing the amp...When i first bought mine many years ago the power tubes kraped out on me two....The local music store talked me into EL-34's as well....and it started blowing the circuit breaker the very next night. i shelved it and stored it for years

years later i decided to play around with it , and After checking the schematic i realized this is basically a poor mans 59 bassman or Marshall JTM 45 copy....beside a few different values and output tube...this amp is almost a exact copy.....and in my opinion has much better transformers than both.

it makes a very good guitar amp...and is worth the time and money
EL-34's will break up different and more fit for guitar....also on mine there was some diodes that took a dump in the output section..so i yanked em and wired it like the early 7027 version.
I changed the tone stack to fender bassman values.....the "low range expander"...would be the bass knob on a fender and marshall and the high range expander would be the presence
(edit) opps sorry the low range expander is the midrange.....and the high range will work as presence if you change the cap and pot to the fender bassman value and remove the extra resistor...look at a 5F6A bassman layout you will see that the Traynor is almost a exact copy

[BassmanPaul]

Just a point, 6CA7s and EL34s are NOT the same tubes and are not interchangable unless the wiring of the tube bases are changed. The 7027 has a different pin out from either. May I suggest that the OP take his amp to a tech and get it looked at. Doing what he is doing has the potential for damage.

[BogeyBass]

Originally Posted by BassmanPaul

Just a point, 6CA7s and EL34s are NOT the same tubes and are not interchangable unless the wiring of the tube bases are changed. The 7027 has a different pin out from either. May I suggest that the OP take his amp to a tech and get it looked at. Doing what he is doing has the potential for damage.

sorry paul 6CA7 and EL34's are pin to pin the same...and often included on the same data sheet

maybe your confusing 7027 and 6L6....which both use the same pins as well except the 7027 which has connections to the unused pins on a 6L6....so yes sometimes an amp with 6L6 will use the non connected pins as wiring points for other connections or their will be jumpers to the non connected pins...so yes at that point you would need to check the wiring and modify the socket wiring...but otherwise 7027 and 6L6 use the same pin outs for heaters, plates, and grids

[jerkass9879]

it's been rewired to use the el34's. I'll still haven't had time to figure out whats wrong but I'll let you know. Anywhere i should start looking? and thanks agian for all the help

[jerkass9879]

all fixed. all new tubes and sounds better than ever. The 1st power tube must have over heated causing the solder to melt and burning a cap on 2 of the connections to the socket