Peavey Mace prob!!

[lp79deluxe]

First of all I'm new to the site and am really enjoying it thus far!! My question if any of you guys have had the same problem is I have a Peavey VT Mace that I LOVE!!! but is has gotten where when i turn it on to play it and the 1st 3 tubes start glowing red after about 2 mins of play,, I can turn it on standby and they cool down and do it all over again, Do I maybe have a bad cap or 2, can anyone steer me in the right direction for me to tackle this myself cus I really enjoy the technical part as well as the playing. Any help would be greatly appriciated,, Thanks guys!!

[Enzo]

It appears that side has lost its bias. Pull the power tubes out of their sockets and fire up the amp. measure DC voltage on pin 5 of the sockets that held the red hot tubes. it ought to be about -50 volts or so. COmpare it to the pin 5 voltage in the sockets that were not meelting their tubes.

Two common reasons to lose bias are a failed coupling cap to the grid, or a bad tube shorting internally to the grid. One tube can indeed kill the bias to its two neighbors.

So if that -50v is missing, then we have to find out why before we burn up more tubes. If it is there, then one of those powr tubes was bad.

[lp79deluxe]

Thanks for the advice, I'll be sure to try that out first thing in the morning, cus i tell ya I can't wait to get this thing goin again..

[lp79deluxe]

I measured the #5 pins this mornin and I'm getting an average of -61.5 all the way across. When I first checked I was getting an avg. of -59.2 on the 4,5,6, tubes (the good ones) and the same avg. of -61.5 on the 1,2,3, (hot tubes) What do you think should be my next step? I aquired a schematic of the amp yesterday.

[Steve Conner]

We need to find out if the problem is in the amp, or in the tubes. So take the 3 tubes that were previously overheating, and swap them with the 3 good ones. If the problem goes with the tubes, then they're tired out and need replaced: you probably want to replace all 6.

If the problem stays with the sockets, then it's a faulty component in the amp.

[Enzo]

If the bias is there and stays there, and -60 is just fine, then the tubes are more likely the problem.

I'd offer a slightly different method than Steve offered. You know which three tubes were melting, right? Plug them into a socket just one at a time and fire up the amp. If it gets red hot, it is probably bad, if it works OK, and does not get red hot, it may well be healthy. In that case, remove it and try the next suspect.

Chances are only one of those three tubes was shorted. SO we test them in the amp individually.

[lp79deluxe]

I swaped out the tubes like Steve said, and when I did I played the thing for like half an hour and all the tubes look normal and appear to be doing good, the amp sounds great and every thing, darned if I know, its weird but the thing seems to be workin for the time being anyway,, I'm gonna try that route you suggested to though

[Amp Kat]

Sounds like you have some weak tubes there and after awhile they give it up and start redplating. One side may still be pulling more current than the other and the MACE uses two different bias leads. A brown wire goes to one side and a blue goes to the other but it sounds like you're tubes are nearing the end and if you get volume loss and treble loss it's a good idea to get them outta there because sometimes when they go , they go hard. An amp like the MACE with that kind of power can take out part of your power board and do some serious damage so it may be a good idea to get a new Sixtet matched pair of 6V6's to keep you in check.

[lp79deluxe]

you may in fact be right, being that now i see that there not gonna blow as soon as i change them I'll probably go ahead and get a new set of tubes, these didn't have that many hours on them though and were never played that hard or gigged with so my concerns are still a little high, i'll just have to try it and see though i suppose, i had the amp worked on about a yr ago, and the guy took out a gaggle of parts that he said was where someone has tried to hot-rod the amp, and he took it back to its stock form which was what I preferred, or at least he said he did..

[sinise]

Mace output traf.

Does anybody know a specification for Mace output transformer which is driven by 6 x 6L6 tubes?
I got Mace amp. but no output traf. so I'm trying to make one,Thank you,Sinise!