low volume from new build

[zimm]

I just finished (hopefully) Dumbleizing my hot rod deville. After checking voltages and going through start up tests, I put some tubes in and fired it up. So far so good. I plugged in a guitar and there is barely audible volume. Its there but something is not right. I think it may be the output tubes. Long story but they are the only set of 6l6's I have, and I put them into an old ampeg a few weeks back. The bias was screwed up on it and the tubes wound up with cherry red plates. Could this have toasted them? The deville was already apart and the Ampeg is still not fixed so I have no way of checking them. I was gonna buy new ones anyway but Im wondering if this is causing my low volume or if I need to be checking other stuff (bad connections, etc)?

[Bob-I]

You should step through all the stages, listening as you go.

Get a large cap, .047 or .1 at 600V can connect it to a test lead, the other end to a connector for a CD player. Use another test lead connected to ground. Connect up a CD player to this (the cap will prevent any DC voltage from frying your CD player).

Inject a signal at the grid of one of the power tubes, you should hear fairly loud output. If that works, go to the other power tube. Next go to the PI input, work your way back through the gain stages.

There's a good chance you have some connection miswired. This will help you locate it.

[jaysg]

The bias was screwed up on it and the tubes wound up with cherry red plates. Could this have toasted them?

It really depends on how long they were red. A minute for instance, isn't going to kill a tube that started off in good shape. It might be the death knell for one with 1000 hours on it.

[zimm]

Thanks for the tracing tip, I will try it this weekend. I have no idea how many hours were on the tubes, I bought the amp used. Im sure they had quite a few between me and the previous owner. I was more wondering if a VERY low output is an indicator of dead tubes or if there is just no output when they are dead? Never had a dead tube before. Thanks

[zimm]

double

[Bob-I]

I was more wondering if a VERY low output is an indicator of dead tubes or if there is just no output when they are dead? Never had a dead tube before. Thanks

All of the above. Tubes can die completley or fade away, there's no telling what will happen.

[zimm]

Got it. Some how I grounded out the master volume when I hooked up the pre amp jacks. I disconnected the jacks and now it is crankin. Ill figure out what I wired wrong and put them back in line. Now the real fun begins, Im sure Ill have more questions soon.