Troubleshooting.

[moamps]

Hi Steve:

Voltage above the nominal level is quite expected when the power supply isn't loaded. Try the amp with one channel first (one output tube) and then check HV voltage. Bleeding resistors are used to discharge HV caps, for safety reasons. They are connected in parallel to HV caps and have a value of around 100k/2W or more.

Regards,
Milan

 

[ethermion]

I don't do bleeders with oilers. Don't know if that is right or not...

Steve,
Where in NoVa are you? I'm in ffx station, near burke lake - a bit south of Mason.

 

[castlesteve]

Hi. I`m in Sterling where rt 28 and rt 7 meet. I`ve got to get this new amp working now as my old backup receiver has decided to drop the right channel. So now i`m out of music except for my headphones. Steve.

 

[ethermion]

Not too far. Email me at eric_e at mail dot ru sometime.

Any luck ohming out B+?

 

[castlesteve]

I`ve got to cook dinner now. I`ll be back in a couple of hours.
steve.

 

[castlesteve]

very bizarre! Amp now appears to work.i`ve not plugged in the pre and speakers yet but all tubes lit and B+ at 400v. What do you reckon. Plug in a couple of cheap drivers and see? Everything is well grounded and all connection appear good and tight.
Steve.

 

[ethermion]

Dunno. For me, problems do not fix themselves, the just hide until I am not looking. Maybe you are more lucky in this regard.

If your problem is hiding for the time being, wire it up and let her rip. With this monsoon we are having, a glass of wine and some glowing tubes is a treat.

 

[poobah]

I agree... never let a mystery go unresolved... it will return.

 

[ethermion]

Maybe he fixed something disabling/enabling the B+ line. I recently found a problem where I failed to solder a heater wire... intermittant, if you could believe.

Or, he could be back out buying more fuses and beer.

 

[Sherman]

very bizarre! Amp now appears to work.i`ve not plugged in the pre and speakers yet but all tubes lit and B+ at 400v. What do you reckon. Plug in a couple of cheap drivers and see? Everything is well grounded and all connection appear good and tight.
Steve.

Steve,

I built that same circuit as a pair of monoblocks and had that exact issue (blowing fuses). I'm with Poobah on checking the heater wires. My problem was the heater wiring on the 9 pin tube (darn pins too close and a stray strand of copper shorted them). I found the problem with a magnifying glass and patience.

It didn't happen every time so I suspect as the tube socket heated up a bit and the wiring also got warm it moved the copper strand just enough. Anyway, re-soldering the heaters and using heat shrink over each fixed it permanently.

Once it is up and running you will absolutely love it! It really is a very nice sounding amp.

BTW I also used 5U4G, 40uF, 8H, 100uF PS, also ASC oil caps. My mains is a bit high and I get 424V B+, works great at that voltage.

 

[castlesteve]

Thanks to all for responding to my posts. My amp is now up and running and sounding really fine. Thanks to Sherman also for all his posts in the past which were my inpiration for building this amp. I`ll post some pictures later when i`ve got time but now i`m going back for another listen. Amazing how much better this sounds compared to my old pioneer receiver. Now all i`ve got to do is build my new speakers and i`ll be set.
Thanks again, Steve.