Build coming together nicely

[jrobson]

Tried new mosfets, no change. Css doesn't seem to be warming up... If I put the 300b tubes in they are dead even though I have proper voltages over the socket, -85v, 452v, 4.85v.

[jrobson]

Can someone please check this for me?
Measured on the board I get:
R1=168r
R2=496r
R10=2.5r
R21=2.5r

These are all from the damme supplier, all say 510r on them... I didn't measure them before installing.

[jrobson]

Sorted the problem with the socket, but still nothing on the 5842 plate Not sure if i should try the 300b's again.

[jrenkin]

I am hoping that I have mine up an running in about a week, or even this weekend, so then I can compare notes. Not that mine is likely to be better in any way...

[jrobson]

Good luck sir, hope you don't have any issues... it's a real problem if you do.
It's my own fault I'll accept that, I only had about 90% of the components at first assembly, I was focused then and installed all correctly, when the rest came I was rushing and doing it late at night because I was very busy, I made some mistakes, it's all been fixed just wish I could figure out what else needs replacement.

Next stop is to start from scratch

[Ian444]

Originally Posted by jrobson

Can someone please check this for me?
Measured on the board I get:
R1=168r
R2=496r
R10=2.5r
R21=2.5r

These are all from the damme supplier, all say 510r on them... I didn't measure them before installing.

R10 and R21 appear to have a trimpot in parallel with them, I would read the setup instructions to adjust the trimpots as required. At the moment it looks like the trimpots are adjusted for minimum resistance which means max current through the tubes which won't be doing them any good. I don't have experience with the SSE/TSE so can't give more detailed explanation. Hope this helps. BTW, I love your chassis, looks fantastic.

[jrobson]

Thank you Ian, I wound them up all the way to check that I installed the correct trim pots in the correct locations, they are 1K and I verified, I didn't adjust them back again when I made the measurement.

[jrobson]

After reading some more posts on here, the problem appears to be around the mosfets or CCS's.

the measurement I am getting off the mosfets are(Pin to ground):
-6x(can't remember the exact number, then B+ 450v, then -86v
On the CCS's
0, 450v, 0

One more thing CSS and Mosfets are now mounted off board because I am destroying the PCB with all the removing and reinstalling the components, can this be a factor?

[jrobson]

Okay

I've narrowed it down to the CCS's or the 5842 tubes, can anyone tell me how to test them(Without a tube tester), it's strange since the CCS's are brand new, problem is they are also $30 a set since it's a difficult part to source locally and I have to bring it in from the UK. I get +-16mV at the side legs...

I'm guessing that a positive voltage from the 5842 is required to switch on the CCS's??????? It is not clear from the data if the CCS's work with nothing applied to the gate.

Good new is that the on the output tubes everything is fine, B+ drops to a nice 374V but obviously no audio since 5842's are down.

Does ANYONE want to give a stab at some advice?

[jrobson]

Checked the tubes, problem found, tubes faulty....
I studied the schematic a little bit too, with my very very very limited knowledge of electronic circuits it appears that the CCS passes the negative B+ as the amp warms up, however once B+ goes positive the CCS no longer passes it, is this correct?
Since the tube is not working it isn't providing a positive signal the the CCS gate, hence the CCS doesn't switch on and stays cold. It isn't clear to me why the -60v on the other side of the coupling cap isn't coming through to the plate, but I assume possible that is what the coupling cap does?

So if the 5842's are in and provide the positive signal the CCS will start functioning and warming up and all should be well?

Can I bias the 300b's without the 5842's in?