5w Screen Grid Resistors solder melt

[Pryde]

Here are a couple photos of the caps. recent F&T can caps 50/50.

No resistors anywhere.

The left cap is tied to rectifier and red/yellow from choke (I believe)
Right cap is tied to those screen resistors and a black wire from choke.

happy to post more photos if needed to help me sort this

If I am doing it right it looks like I am getting 1.94v DC.

[Chuck H]

I think you need to stop powering up the amp now. It looks like the OT secondary and primary CT are on the filter caps and a host of other mistakes. That amp needs to be torn down and rebuilt IMHO.

[Tom Phillips]

Your photos are very clear.
It would help if you posted one showing a complete gut shot.

[g1]

I think you need to stop powering up the amp now. It looks like the OT secondary and primary CT are on the filter caps and a host of other mistakes. That amp needs to be torn down and rebuilt IMHO.

Chuck: The blue and brown where you have labelled "primary" are going to pin3 of the power tube sockets, the screen resistors are going to pin4.
The wires you have labelled as "secondary" (black and yellow) are what I believe to be the choke.
The complete gut shot Tom requested will help to see where the output jack wires are going (OT secondary).

Edit: A resistance reading of the choke would also help.

[Chuck H]

Yes on the pins. I edited my post before yours landed . But look at the bolt pattern for the OT! That Bassmaster has a single 8R secondary. Where is it if that's not IT going to the filters? And look at that other cement resistor wired in series to the screen resistors. That, I believe, is the resistor everyone's been looking for.

[g1]

That 5K is to the next filter node, feeding the phase splitter.
A top side picture will show if there's a choke or not, along with a full gut shot.

[g1]

But look at the bolt pattern for the OT!

I think it's much bigger than that! Four of those bolts should be for the choke, I think we can see 2 of the OT bolts and the other 2 are off to the right of what is pictured.

[Pryde]

Sorry guys, back at this morning. Yes the amp does have a choke so its likely the schematic on page 6. I know the amp has worked without issues for the past year according to the owner so I don't think it would need torn down completely. The only outstanding issue right now appears to be the screen voltage is 13v higher than the plate voltage. Here are some more pics as requested.

[Chuck H]

I think it's much bigger than that! Four of those bolts should be for the choke, I think we can see 2 of the OT bolts and the other 2 are off to the right of what is pictured.

Looks like you got that one Which is good news. Glad to be wrong on this. Sorry for the distraction from the issue.

[Chuck H]

It looks like everything is wired correctly Bias seems correct. Voltages look like I would expect except for the choke and the drop across it. Discharge the filter caps, lift the black choke lead (looks like the easier one to lift) and measure the DCR for the choke coil.

[Pryde]

It looks like everything is wired correctly Bias seems correct. Voltages look like I would expect except for the choke and the drop across it. Discharge the filter caps, lift the black choke lead (looks like the easier one to lift) and measure the DCR for the choke coil.

OK I lifted the choke black lead from the filter cap and took a resistance reading between it and the red/yellow leads (connected to the other filter cap and its settling on 95 Ohms

Is this correct procedure?

[Chuck H]

I know some chokes are as low as 100 ohms. I don't think that would be one of them. Excessive screen dissipation under load could result. The resistors would have gotten very hot and that could explain the brown spot on that PI coupling cap. Try subbing a 470 ohm/10W resistor for the choke and recheck voltages.

[Pryde]

So you think the choke is bad and this is why there is more grid voltage than plate? Just want to understand a bit better.

Of course I have no 10w 470 ohm resistors, only a 250 in 10w. Going to have to order some more I guess.

[Chuck H]

I think the choke MAY be bad. If you have more than one 250 ohm you can put them in series. Or a pair of 1k/5W in parallel. It's OK to get creative. You just need to find out if isolation is the problem.

[Pryde]

So you think the choke is bad and this is why there is more grid voltage than plate? Just want to understand a bit better.

Of course I have no 10w 470 ohm resistors, only a 250 in 10w. Going to have to order some more I guess.

I am going to need to order some more 5 and 10w resistor stock

Just to clarify at this point after soldering everything back up and reflowing a couple suspect areas on the board I am getting:

plate voltage: 413vDC
screen voltage: 415vDC

So it appears the screens are at plus 2 volts vs the plates so pretty even really. When you say the screen voltage has to be lower, how much lower are we talking? I have read that some EL34 amps run pretty even voltages (although not necessarily trusting the sources). Also the choke on this is a monster piece of iron. Can it be capable of 100 ohms?

Thanks for the education!