Author Topic: How Do I test....  (Read 2052 times)

Canucker

How Do I test....
« on: May 15, 2014, 01:41:09 PM »
...ok this is an amp question but it is pedal related in the fact that a couple years ago I killed an amp with a botched pedal build and a huge lack of common sense....
I built a pedal and it was working fine....then the next time I went to use it did nothing....amp plugged in, not on standby....I visually inspect the pedal and I see a disconnected wire...I take the wire and touch it to the spot I thought it went and ZAPPPP the amp goes out....so I basically zapped my amp with a 9volt battery.... this was when pedal building was new to me but I clearly should have known better.....

So my question is how do I go about properly testing that the transformers are still properly working....I figure that would be the place to start....the amp hasn't been plugged in for well over a year so it won't be holding a charge anymore (I have discharged caps before as well as replaced them so I do have some tube amp experience/knowledge....this whole story proves that I use to be stupid but I'm not anymore).

http://www.lynx.bc.ca/~jc/690131_Ygm3.gif That's the amp...a 20ish watt Tube amp with 2 6BQ5 Power tubes and 4 12AX7 tubes.

I'm up at the cottage and the amp isn't with me but I figured you guys always have such great advice that if there was any for this I'd read it a few times over before getting back home to work on it! Thanks guys!

wavley

Re: How Do I test....
« Reply #1 on: May 15, 2014, 02:18:29 PM »
...ok this is an amp question but it is pedal related in the fact that a couple years ago I killed an amp with a botched pedal build and a huge lack of common sense....
I built a pedal and it was working fine....then the next time I went to use it did nothing....amp plugged in, not on standby....I visually inspect the pedal and I see a disconnected wire...I take the wire and touch it to the spot I thought it went and ZAPPPP the amp goes out....so I basically zapped my amp with a 9volt battery.... this was when pedal building was new to me but I clearly should have known better.....

So my question is how do I go about properly testing that the transformers are still properly working....I figure that would be the place to start....the amp hasn't been plugged in for well over a year so it won't be holding a charge anymore (I have discharged caps before as well as replaced them so I do have some tube amp experience/knowledge....this whole story proves that I use to be stupid but I'm not anymore).

http://www.lynx.bc.ca/~jc/690131_Ygm3.gif That's the amp...a 20ish watt Tube amp with 2 6BQ5 Power tubes and 4 12AX7 tubes.

I'm up at the cottage and the amp isn't with me but I figured you guys always have such great advice that if there was any for this I'd read it a few times over before getting back home to work on it! Thanks guys!

Pete Traynor hated replacing transformers on rental amps, it's one of the reasons that he started building amps.  The iron in these amps is pretty bulletproof, it would have to be something really catastrophic to take out a power transformer in one and unless you left the speaker unplugged while it was on, I kinda doubt that you have a problem with the output transformer.  Traynor heads all have a resistor on the output to keep the tranny from blowing up, the combos don't.  I recommend putting one in, if I remember correctly it's a 180 ohm 5 or 10 watt he used, look up the YBA-1 or YSR-1 schematic and it's connected to the output jack.

Is there something that is making you suspect the iron?

 RG has a nice paper on output transformers http://www.geofex.com/ampdbug/outtrans.htm and he also has one for power trannies http://www.geofex.com/ampdbug/pwrtrans.htm

The good news is that Hammond makes perfect replacements.  I had to replace the output on one of my YSR-1's because before I knew a lot about fixing amps I took it in for a re-cap and somehow he blew my transformer (which somehow he blamed on me, even though the amp worked fine and I was taking it in for preventative maintenance), he sold me on replacing it (which he never did) and 8 months later I finally picked up my non-working amp.  So I learned how to work on amps and started a career in electronics, with my first job being working for his competition.  The irony is that while fixing that amp I discovered that he never even replaced the big filter caps that were the whole reason I took it in, he just did all the little cathode bypass caps.

If you aren't already a member of the yahoo traynor amp group, I highly recommend it, if not just to see the schematics of all the stuff John Jasilli did to his YGM-3.
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Canucker

Re: How Do I test....
« Reply #2 on: May 15, 2014, 03:42:44 PM »
Thanks for the feedback!
I'm not really suspecting one thing over another...I just figured start with the expensive parts and work my way down to the cheapies. I think I may have used the same amp repair guy you did actually.... I took in a bassmate that I now know needed a cap job (this was ten years ago) and he told me it needed a new output transformer...which I contacted Yorkville about and they said that such and such part number from the new line of traynors would be a suitable replacement and I went into the local music store and ordered it for $27 which was much cheaper then I expected...the same repair guy was also to Bias a Traynor BassMaster for me at the same time....he had me return two sets of tubes to the shop I picked them up at claiming they were defective....then he realized and admitted he was doing something wrong...and got the job done with the third set of power tubes... I didn't return to him with the output transformer once it had come into the shop....two years later I installed it myself only to have the amp behave no differently....eat power tubes......last year I dug up that amp from storage and did a cap job on it....sadly it didn't solve the problem...that amp is second on my list of traynors to fix... guitarmate first, bassmate second. Thanks for recommending the Traynor newsgroup. I'll check it out...I own enough of the dam things!  :icon_lol:

wavley

Re: How Do I test....
« Reply #3 on: May 15, 2014, 04:04:33 PM »
Thanks for the feedback!
I'm not really suspecting one thing over another...I just figured start with the expensive parts and work my way down to the cheapies. I think I may have used the same amp repair guy you did actually.... I took in a bassmate that I now know needed a cap job (this was ten years ago) and he told me it needed a new output transformer...which I contacted Yorkville about and they said that such and such part number from the new line of traynors would be a suitable replacement and I went into the local music store and ordered it for $27 which was much cheaper then I expected...the same repair guy was also to Bias a Traynor BassMaster for me at the same time....he had me return two sets of tubes to the shop I picked them up at claiming they were defective....then he realized and admitted he was doing something wrong...and got the job done with the third set of power tubes... I didn't return to him with the output transformer once it had come into the shop....two years later I installed it myself only to have the amp behave no differently....eat power tubes......last year I dug up that amp from storage and did a cap job on it....sadly it didn't solve the problem...that amp is second on my list of traynors to fix... guitarmate first, bassmate second. Thanks for recommending the Traynor newsgroup. I'll check it out...I own enough of the dam things!  :icon_lol:

Yikes!!

I have two YSR-1s and a YBA-2ab and until recently my bass player had a YBA-1.

Eats tubes huh, how quickly is it eating tubes?  These things really push the limits of what a EL84/6BQ5 should be dealing with, but I've never really had any problems, two or three years ago I finally replaced the Mullards that were in it because they were sounding dull but still working fine, I got the amp around 2000 so I don't know when they were put in, but they were certainly not the new ones.  I've been running JJ's in mine ever since and I run that amp hard.  I did go by John's schem and change it over to cathode bias (the power section of our amps should be the same without the tremolo bias wiggle)  I just looked at my copy of one of his revisions and it looks like he added separate 100 ohm screen grid resistors to pin 9 of the tubes, somewhere around there is where I would be looking at for a problem.  Either screen grids or bias, if you add 1% 1 ohm resistors to pin 3 then it's easy to calculate your bias current by reading the voltage across them.
New and exciting innovations in current technology!

Bone is in the fingers.

EccoHollow Art & Sound

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Canucker

Re: How Do I test....
« Reply #4 on: May 15, 2014, 09:29:50 PM »
ok I think I'm trying to remember to many things at once since I started to mention the Bassmate....the bassmate was eating a power tube the second you turn it on...under one second.....the reverbmate killed fuses the second it was turned on......so tracing the problem of the bassmate would be easier since you can see burn marks on specific pins of one of the power tubes....as I said I don't have the amps with me so I can't just take a peek and say which ones....I'll have to wait until next week to get specific....sounds like your able to point me in the right direction once I've got my hands on them! Thanks for your assistance and patience! I also have a pair of YRS-1's...... gotta love that reverb tank when your driving in the car! My main amp that I play is the ReverbMaster SC (4x10 combo)...other then recapping (before it was a must) and replacing speakers it hasn't needed anything to be done with it...love that amp! Should probably look into the trem though since the volume drops by 80% when its engaged....but I don't make use of it anyways....loving the KayTremolo I built way to much!