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Traynor YBA-1 Failure - Please Help

egardner6291

Member
Messages
3
Got a pretty solid deal on an old Traynor Bassmaster, knowing it would probably need some work. What the guy didn't tell me was that it starts smoking as soon as you hit the standby switch. I popped it open and found a resistor smoking. I changed out the tubes, and the resistor still smoked when the amp came on. Swapped out the resistor (installed a 3-prong while I was in there) and the new one failed immediately.
Is there some other component that would cause the resistor to burn out? Am I reading the schematic incorrectly (replaced the resistor with a 4.7k 1 watt)? If anyone's got any info, I'd greatly appreciate it. Just want to get this thing up and running. Thanks.





 
Last edited:

xtian

Gold Supporting Member
Messages
2,497
Needs to be modernized: replace all electrolytic caps, power string resistors, diodes and screen resistors. Then follow first-time start-up routine (use bulb limiter and start with no tubes, etc.).
 

AL30

Member
Messages
3,001
One of your big 470 ohm resistors appears to have a hole in it and heat damage. That's not uncommon.

It's an old amp - it needs maintenance. Give it a cap job (all electrolytics). Replace the 2 prong power cable with a modern 3 prong.. Check the voltages from there and replace anything out of spec.

AL
 

egardner6291

Member
Messages
3
Thanks guys. I was going to do a complete cap job eventually, but had some studio time coming up and didn't know if there might be a temporary fix to the resistor problem to at least have it in working condition for a while
 

axpro

Member
Messages
628
temporary fix would be to change JUST the resistor! It's a 40 year old (or older) amp. It has a few issues stone stock and working properly, but at it's age, it needs some love. The schematic you show is definitelt NOT the one for that amp. it's the current schematic for one of the reissues. So first, find the correct version of the schematic you have. It could be in the amp cabinet (that is common) It looks like you have an older version, perhaps early 70's, it looks like the original chassis not the later "baby bumper" chassis. This would most likely mean that it is going to be pretty rough on power tubes, as the B+ on those amps is very high. I am halfway through modding a later model into a more marshall terrirtory, but even the later ones ran pretty crazy high on the voltage. Don't skimp on tubes for this thing!

Other than that, enjoy your piece of Canadian History! And you posted on Canada Day no less!
 

egardner6291

Member
Messages
3
temporary fix would be to change JUST the resistor! It's a 40 year old (or older) amp. It has a few issues stone stock and working properly, but at it's age, it needs some love. The schematic you show is definitelt NOT the one for that amp. it's the current schematic for one of the reissues. So first, find the correct version of the schematic you have. It could be in the amp cabinet (that is common) It looks like you have an older version, perhaps early 70's, it looks like the original chassis not the later "baby bumper" chassis. This would most likely mean that it is going to be pretty rough on power tubes, as the B+ on those amps is very high. I am halfway through modding a later model into a more marshall terrirtory, but even the later ones ran pretty crazy high on the voltage. Don't skimp on tubes for this thing!

Other than that, enjoy your piece of Canadian History! And you posted on Canada Day no less!
Thanks. I posted the wrong file when I posted the schematic, just edited it now.

Tried replacing the resistor, and it burned up as soon as I powered up. At this point, a cap job seems like a must, and I'll probably replace the screen grid resistor (if that's indeed what the 470ohm 10W brown log is) and go from there.
 

axpro

Member
Messages
628
Time to test! As much as i love Traynor gear, the fact that it ran high B+ back in the day, and even HIGHER now, does cause a few headaches. On my YBA-1 i've added a Big Ass Zener diode to drop some voltage, also added an extra filter stage, with a pair of 100uf 350v caps in series with balancing resistors. both mods helped to bring the B+ down to a more sane level. Now i am tweaking components and getting it as close to JTM50 territory as i can. It's getting there.

If your wall voltage is on the high side, you could be really slamming those caps in the power supply section.
 




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