1973 50 Watt Lead - Japan??

[Cameron]

Nope, definitely 1M+. Just checked again and measures 1.15M.

Why?

Thanks

Take out the tube ...if you haven't... Also to get a accurate reading you may have to unsolder the b+ (blue wire) from the socket ...you may be getting a bit of voltage from the cap ...that will give you a false reading ...you could also ...with a clip lead ...ground the b+ side ..with the tube pulled out...and measure it that way .....

[Deric]

Tubes are pulled, caps are drained and shorted to ground.

[Deric]

B+ 423vdc All other voltages in spec but V2a. Pin 1 50vdc, pin 3 0.1vdc. Pulled the plate resistor of the socket and still = 1M+. Appears to be cracked - can't see it but if I wiggle it around it varies form 1.15M to 1.55M.

Replaced bias caps and diode, 68k input resistors, V2a plate resistor.... Waiting for cap cans and a couple of other parts...

[oj]

Any reason to keep the carbon comp 68k resistors on the inputs as opposed to swapping them out for metal film?

or do as I always do, only use one input and use a shielded cable with a 33K in the end and parallel pin 2 and 7.

Benefit little more gain and less hiss and noise

[Structo]

That is a cool amp.

Looks well made.

Anxious to hear a tone report when you get it fixed.

[Structo]

I see the owner posted about it at TGP.

http://www.thegearpage.net/board/index. ... p.1641789/

[Deric]

Different amp Tom. Thanks for the link though.

[Deric]

Just finished this up.

New F&T filters, bias caps and diode, V2a plate resistor, 5k6 grid resistors on the output tubes, 220k grid leaks, 68k metal film input resistors, 220u V1a cathode cap and 820r resistor, 2k7 V1b cathode resistor. New power cord.

Crazy hiss is gone. All voltages in spec. Very quiet (noise wise) when cranked.

Sometimes I forget just how good these things can sound. I'm pretty sure the neighbors liked it too.

Thanks for all the input!!

[Deric]

Last ones...

Thanks again!

[Smokebreak]

Good work. Man I love the color of those boards.

[Medronio]

Sorry to revive a dead thread but i got a question regarding the diode change:

Why change it? Can you measure if it is wrong/failed? If so, how?

Well, seem to be 3 questions ...

Thank you in advance

[martin manning]

Deric may respond, but I'm going to suggest that it was changed along with the bias caps as a preventive measure because bias voltage is critical, and the cost of the part is almost nothing.