Clone of a Clone

[eric02]

Hello all, my first post here and of course it to ask for help.
I just completed my third amp project, a copy of the ceriaton AFD# 35. on my previous builds ( a 56fa bassman and a small 5 watt kit
that i got here in germany)I had no problems. the problem with this amp is it is not making any sound what so ever. tubes are glowing,
when i first started the amp without tubes (speaker cab was conected) i had voltage to the caps around 450v. right now i cant test anything
becouse my multimeter is not working now will buy a new one tomarrow Tubes are new JJ 12ax7s and in the power section i did not use the
6550s on the layout but went for kt88s from sovtek. the transformers are a set from IG Präzisions-Wickeltechnik that are exact copies of the
Drake 784-139 for the JMP50. even the channel switching relay is working. Does anyone know where i should start the search? here are a couple links to the layout and the transformers although he dosent have the data there for the transformers ido have the Datasheets and the tests that he did when Ing built them.

IGOT-JMP50 | Ausgangsübertrager | Transformatoren | IG Präzisions-Wickeltechnik

http://www.ceriatone.com/images/layo.../AFD35_50W.jpg

p.s. I have searched the internet for these symptoms but mostly i get the pre amp tubes as the culprit and i cant belive that i have 4 brand new tubes that dont work.

thanks for any help, Eric

[gtrplayr1976]

Welcome Eric ! Lots of good folk here to help. Can you get some good gut shots of the project ? It may help a lot.

[loudthud]

Lots of coax in that layout. Check for shorts on each piece. Posting the voltage on each tube pin will usually show any wiring errors.

[sgelectric]

Welcome Eric,

One question: On the layout diagram a note at the input to the first 12ax7 says "Shield = 2 inch (and glue wire)".
I am unclear as to what this means..... Glue the wire to what?..........the chassis?.....Just asking.
Any clarification by someone in the know appreciated.
Thanks, SG

[R.G.]

Hello all, my first post here and of course it to ask for help.
Does anyone know where i should start the search?

Old tube techs used to use the so-called "disturbance test". All this means was to hook up your meter common probe to ground, then touch the test lead to tube grids. They didn't often bother to look at the voltage. Touching the probe to the grid caused a small "tick" in the output. No tick = not amplifying between that grid and the output.

The general idea is to start at the output tubes, and verify that they both would cause a small tick. Moving back to the phase inverter, you should get a bigger tick. The further back, the louder the tick. When the ticks stop, something between that grid and the last one you got is busted.

Tells you nothing about what it wrong, but isolates the location of the bug quickly, and does not need a working DMM. If you don't want to use your non-functioning DMM, you could make up a "disturbance probe" with a 1nF cap to ground paralleled by a 2.2 to 4.7M resistor. The resistor discharges the cap between probes and the cap couples in a short pulse of ground.

[gtrplayr1976]

Thanks R.G. you just gave me another tool to help find why my vibrato channel doesn't work in my new build.