#1
Hello

So about a month ago my Traynor YCV50 started making this crackling noise, independent of volume or if guitar was plugged in. After googling around a bit and by poking around the amplifier with a stick, I isolated the problem to be one of the two power tubes. When poked, it would cause a burst of noise and the crackling disappears. I read that it might help to pull it out and clean the socket/pins to remove any oxidization, so I did and it helped. But now it's back. At one time when i poked the tube, a spark occured in the tube, probably not a good sign?

Any ideas? I guess I have to buy a new tube, in that case I should replace all the power tubes and not just the 1 right? I would like to avoid hassling too much with it, but as far as I know, if i replace the tubes the amp has to be re-biased right? Or am I able to get a near-identical pair to the ones I have and avoid it?

Thanks
#2
Yeah, buy a matched set and replace both of them.
The manual explains how to bias them. It's pretty easy on those. You have to pull the chassis and work on a live amp though, so if you aren't comfortable working with high voltages don't do it. There's like 400Vdc in there and it's powered up, it can kill you.
Inside find R91 and R92 and measure the voltage across them. They are near the power tubes. Then adjust the bias pot (P12, it's between the power tubes and the two 3 pin regulators) until you read 350mV across each resistor. If the tubes are balanced they should be the same. It can be out by a little but try to get it as close as you can.
You have to do this with the amp on and off standby. Don't forget to plug in the speaker. And turn down the volume.

That's how it's done. I am not going to tell you to do it because I don't know how capable you are, but that's how it's done.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Apr 15, 2014,
#3
Thank you! I think I'll give it a go, trust me I'm an engineer !

EDIT: After doing some research before i venture into tube biasing, the amps manual states:
This amplifier features Yorkville’s auto-balancing / auto-matching tube biasing technology. As a result, when the time comes to replace the tubes in your Yorkville amplifier, there is no need to pay a premium for a matched set – nor does the bias need to be adjusted when you use a different brand. We make no claims as to which brands of tubes might sound best, but with auto-balancing / auto-matching, you are free to experiment without any need for concern that the amplifier or tubes will be distressed. Please note that auto-balancing / auto matching cannot fully compensate for different types of tubes - 6L6/5881s versus 6CA7/EL34s, for example.


Soooooo I might get off easy ?
Last edited by FullHorizon at Apr 15, 2014,
#4
Yeah. The schematic I looked at was a simple fixed biased system (ie, dc bias offset applied to the grid), adjusted like I said. If yours is different then, sure, sounds like it's just plug and play.
R91 and R92 on the one I looked at were 2 ohm resistors between the cathode and ground, there purely to give a probe point for measuring the quiescent current. Check the schematic and see for yourself, if you're an engineer it should be pretty obvious to you what's going on.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Apr 15, 2014,