peavey duel 212 no output

[52 Bill]

Just got the socket desoldered gonna try heating it tomorrow in an old toaster oven to see if goop will come out.

I first test stuff like that by touching the tip of a hot soldering iron to it. If it's wax, it will melt very quickly. If it's some sort of glue, it may or not melt, but it might give off some sort of odor that will suggest what it is made of.

[nosaj]

I first test stuff like that by touching the tip of a hot soldering iron to it. If it's wax, it will melt very quickly. If it's some sort of glue, it may or not melt, but it might give off some sort of odor that will suggest what it is made of.

I soacked the socket in Goo gone. used a small drill bit with my fingers to clean them rinse it in naptha let it dry then held a lighter flame to it for a short bit. looks better and passes continuity not intermittantly. No continuity between any separate pins. Now gotta pop rivet and solder the socket back in.
And jumper the filament wires past the molex(?) plug.

nosaj

[nosaj]

I soacked the socket in Goo gone. used a small drill bit with my fingers to clean them rinse it in naptha let it dry then held a lighter flame to it for a short bit. looks better and passes continuity not intermittantly. No continuity between any separate pins. Now gotta pop rivet and solder the socket back in.
And jumper the filament wires past the molex(?) plug.

nosaj

All back together now 6.2 on the filaments. Put the 3 jjs back in and one sylvania I had just for testing purposes. Everything sounds good little extra hum I m guessing from mismatched tube. Order a new set and check it out.

Thanks all
nosaj

[nosaj]

All back together now 6.2 on the filaments. Put the 3 jjs back in and one sylvania I had just for testing purposes. Everything sounds good little extra hum I m guessing from mismatched tube. Order a new set and check it out.

Thanks all
nosaj

I know that some Peaveys were auto biasing. I do not see a pot on this one. By looking at the schematic it looks as this is a fixed bias at -50vdc. When I get the new power tubes the -50 is what I should shoot for?

Thanks,
nosaj

[The Dude]

The DC voltage on the grids tells you almost nothing except that you have bias voltage. Measure the current for an actual bias reading. That said, it probably worked for years like that and will probably work for many more as is.

[Enzo]

PV amps were never "auto-biasing", what they were was a fixed and non-adjustable bias that was by design cool enough that almost any tube would work in it. That -50v won't give you the magic 70% that everyone just HAS to set it to, but the amp will be strong and clean with good tube life.

[nosaj]

PV amps were never "auto-biasing", what they were was a fixed and non-adjustable bias that was by design cool enough that almost any tube would work in it. That -50v won't give you the magic 70% that everyone just HAS to set it to, but the amp will be strong and clean with good tube life.

So a new matched quartet should be just fine. then. when they come in I'll post the bias current.

Thanks,
nosaj

[nosaj]

All back together now 6.2 on the filaments. Put the 3 jjs back in and one sylvania I had just for testing purposes. Everything sounds good little extra hum I m guessing from mismatched tube. Order a new set and check it out.

Thanks all
nosaj

I'll tell you what i think happened. The adhesive on the tube and socket is not the same as the the stuff on the circuit board.

The bear trap clamp was not holding the tube and needed retensioning. There was no way something could have gottin to the socket the way i found it. I really think someone glued the tube in which in turn went conductive and caused the issue.

Not that the offender will cop to it, but thats what I think.

So if I want to check the amp for quietness before I get a new quartet of tubes. The amp is set on 16ohm(which is what the speakers are( it was on 8ohm when I aquired it)

I believe I can just leave 2 power tubes in (2 outside or 2 inside tubes ) and put a 8ohm speaker to see how quiet it really is.

Am I correct in this belief?

Thanks,
nosaj

[Randall]

I believe I can just leave 2 power tubes in (2 outside or 2 inside tubes ) and put a 8ohm speaker to see how quiet it really is.

Am I correct in this belief?

Set the impedance switch to whatever the speaker load is, this is independent of whether you have 2 or 4 tubes running. However, how quiet it idles may be effected by matching of the tubes, so running 2 of the tubes you have now may not tell you how it will perform with a new matched quad set.

[nosaj]

Set the impedance switch to whatever the speaker load is, this is independent of whether you have 2 or 4 tubes running. However, how quiet it idles may be effected by matching of the tubes, so running 2 of the tubes you have now may not tell you how it will perform with a new matched quad set.

But when you pull 2 tubes you are changing what should be seen on the speaker side, no?

nosaj

[g1]

Yes you are. It shouldn't matter much for test purposes.
Ideally, if you want to remain impedance matching, with 2 tubes pulled you set the switch to be double whatever the cab impedance is.

[Enzo]

Yes^^^^^

IMpedance mismatch might affect tone in a subtle way,and it might affect efficiency of power transfer from amp to speaker. But what it won't do is create noise. An unbalanced power stage can have more hum than we like, but that isn't impedance, that is 2 or 4 tubes instead of 3 or 1. For testing this it really doesn't matter wha tyou set impedance to.

[gene]

Just a note from a guy that bought a non-functioning Duel 212 about 6 weeks ago.

Got it cheap at the local swap meet, and of course even though all the tubes were present, it didn't work. (What a suprise, it also took me some time to figure out where the 12AX7's were.)

I started looking things over before I tore into it, and noticed the 4 6L6's were not lighting.

Took the amp out of the cab, and noticed the ribbon cable Molex plug end that plugs into the 6L6 board had overheated and had burn marks. I quickly figured out it was the heater voltage pins. I cut the Molex off, removed the pins at the 6L6 board, then soldered the ribbon directly in. Later, after talking to Peavey customer service, they admitted that that was a problem they were aware of, their fix was to change the pins in the Molex connector to a design that had 4 contact faces, not two like mine did.

As for your problem with the "glue" that you've seen on the PCB, if yours was built like mine, it is glue, and mostly on the large radial electrolytics to keep them from moving around too much in rough service. I haven't found a way to remove it (yet) but perhaps I'll try the heat gun.

My next project is to install a 120 vac fan to remove some of the heat that 6L6 area gets, that can't be good in the long run.

[Leo_Gnardo]

As for your problem with the "glue"? that you've seen on the PCB, if yours was built like mine, it is glue, and mostly on the large radial electrolytics to keep them from moving around too much in rough service. I haven't found a way to remove it (yet) but perhaps I'll try the heat gun.

Peavey used "hot glue", so your heat gun will make it soft then runny whilst roasting those old 'lytics. I just pry the stuff off at room temp with the handy sharpened bent screw driver. Some hose it with chill spray then it cracks off easily whilst frozen. Wouldn't be such a bad idea to replace those old electrolytics while you're at it. I use RTV silicone to hold such things in place, if I'm ever going to remove 'em again. There are more aggressive glues like 3M weatherstrip glue or Seal-All you could use instead, as long as you're sure you don't want to pry 'em off again.

Yes it was best to direct solder those filament leads to the circus board.

[Enzo]

The secret to hot melt is freeze spray. Hose the blob of glue down, with freezit, and it gets real brittle. You can then easily shatter it and brush it away.