mesa triple no output also rapid popping/puttering noise even while disconnected

[nickelus]

Hi guys,

I have a mesa triple rectifier, had it for about 5 years and definitely enjoy it (regardless of the higher than usual maintenance). Today I went to plug in and had no output, nothing at all. So, i checked the usual: cable connections, volume levels, even started testing tubes (about 3 months old was worth a try). That's when i noticed a rapid puttering, so i disconnected everything even the speakers and input, now the bare amp was still making this noise. I shut it off, scratched my head, and did some reading. What i know so far is: the foot switch is working to change channels, channel 1 is the only one making noise, all others are dead, and loop on/off doesn't appear to make any difference. Leading up to this the only things i can remember that i found relevant were the channel switching via foot switch was getting loud, and ground hum was starting to become annoying and channel 1 specifically was getting weak and slightly distorted. Well, after reading up using what keywords i could think of, I've come to understand the muting channel / relays maybe at fault. If anyone has knowledge of this amp or this type of issue please let me know of any troubleshooting i can try to pinpoint the issue. Thanks in advance!

Ok, today I tested the J175s.. lots of them. I noticed all read OL in both directions except the two that show 48 -50k readings and those were labelled J175M. I'm guessing those are part of the muting circuit everyone else is talking about. Waiting for a callback from Mesa we'll see and i'll be sure to post results.

[Chuck H]

All I can tell you is that the put put noise is most likely an oscillation caused by positive feedback. That could well happen if some of the internal switching (or LDR's) are failing to do their job. It may also happen due to oxidized contacts (the amp HAS been sitting). I'll assume the amp was working the last time you used it. So, what happens to an amp that can make it fail while it's not in use???

I say clean all the tube sockets, tube pins, jacks, jack switches (jack plug triggered switches) and other switches as can be cleaned with contact cleaner. If it's still not working you'll probably want to take it to a shop. At that point it would be very hard to diagnose remotely (as in asking us) or even communicate the issue effectively to facilitate the repair.

[nickelus]

All better now. Well the amp was sitting, but by sitting we're talking 10-14 days. What ended up being the cause was V1 & V5 preamp tubes as suggested in an uncannily instant reply from the kind folks over at Mesa (i usually test individual tubes however it was the combo, and now i know better). I'm still very interested in those transistor readings and how they may be the cause of the humming and loud switching clicks/pops that still occur but that can be a new thread sometime. Well thanks everyone for looking and Chuck H for the reply, and since I've always overlooked the importance of clean contacts I'll be using your advice as well to keep things tight. Have a great day!

[jmaf]

What ended up being the cause was V1 & V5 preamp tubes as suggested in an uncannily instant reply from the kind folks over at Mesa

What was it with the tubes? How did Mesa know they were it instantly? As Chuck said it'd be practically impossible to determine what exactly it was just by the symptoms.

Ok, today I tested the J175s.. lots of them. I noticed all read OL in both directions except the two that show 48 -50k readings and those were labelled J175M. I'm guessing those are part of the muting circuit everyone else is talking about.

Did you try shorting the gate to source before taking readings on the channel on the ones which show resistance?

[nickelus]

that's what spooked me about it jmaf. i had already tried replacing those one at a time and it did nothing except maybe made it a little quieter.maybe it was because they an entirely new set all 14 tubes? but that's what Marcus said to do so i did them both and voila. those are new tubes too used like once a week. so i guess i'm still on the search for a good place to buy the perfect tubes for this beast.

[jmaf]

that's what spooked me about it jmaf. i had already tried replacing those one at a time and it did nothing except maybe made it a little quieter.maybe it was because they an entirely new set all 14 tubes? but that's what Marcus said to do so i did them both and voila. those are new tubes too used like once a week. so i guess i'm still on the search for a good place to buy the perfect tubes for this beast.

Look for Groove Tubes in your area. A GT dealer or your tech will tell you how to match for Mesa Boogie amps.