Problem with my Darling!

[jeff mai]

The coupling caps would be the 27uF films connecting the 6J4 plate to the 1626 grid I assume?

Yes those are the coupling caps, but I hope the value was a typo. 27uf is probably 100 times too big! It could also play havoc with clipping input signals because grid current would want to charge the cap.

Maybe try a smaller cap (much smaller - like less than 0.5uf - I'd shoot for 0.1uf) *and* testing with a smaller signal.

 

[John Fader]

Uh-OH, Philip,

those should be 0.22 uF, not 27 uF.

That is not likely your problem, but it *could* be depending upon the leakage of the large caps you chose, esp. if they're electrolytic.

Cheers/Fader

 

[philipbarrett]

sorry 0.27uF, it's early! Now those have ".27K" printed on them, that is correct?

P

 

[John Fader]

yup!!!

 

[noisenyc]

hey phil

this might sound silly but...it happenns. check all your output wiring, esp the tube pinouts.

double check ground path as well.

 

[l_paitoon]

My Darling

 

[MelB]

Philip, have you checked the value of the grid resistor on the 1626's?

 

[philipbarrett]

Been through the whole thing with 3 fine tooth combs! Then I got a technician friend (who builds balls-to-the-walls tube guitar amps) to go through it with a 4th! He has all the test gear, dual-trace scopes & the like. Gotta suspect the tubes here at this point.

The up-side of all this is that I've learned a lot. If I'd plugged the thing in & it had worked first time I'd have been thrilled but I wouldn't have got the tube trouble shooting experience. I've had to pore over data sheets, brush up my basic electrical theory, figure out how to test various areas, so it's really been a positive experience.

P

 

[noisenyc]

Philip, have you checked the value of the grid resistor on the 1626's?

good point...grid leak resistors...also what kind of OT iron?

 

[philipbarrett]

Hammond 125 ESE's, all hooked up correctly (believe me I checked)

 

[noisenyc]

Hammond 125 ESE's, all hooked up correctly (believe me I checked)

dang, too bad you don't have a tube tester laying around...what value grid leaks on the output tubes?

 

[noisenyc]

haha this thread just brought back a fun memory.

the first time i heard this tube making audiop was in bob d.'s fiat at nyNOISE.

the next year he showed the darling.

fun fun.

 

[philipbarrett]

what value grid leaks on the output tubes?

As Manuel would say, que?

P

 

[noisenyc]

resistors running from grids to ground on the output tubes...

this is cathode bias, no?

 

[philipbarrett]

274K, BTW, why am I sitting at my computer today? Because Chevrolet cannot design an interior lighting system that actually stays off once you've left the car. Try cranking a 350 with one of those Pep Boys dollar-three-eighty chargers, as my teen daughter would say "sad!"

P

 

[noisenyc]

274K, BTW, why am I sitting at my computer today? Because Chevrolet cannot design an interior lighting system that actually stays off once you've left the car. Try cranking a 350 with one of those Pep Boys dollar-three-eighty chargers, as my teen daughter would say "sad!"

P

hehe count your blessing...now you get to obsess about your non working amp.

and so do i hahah.

274k sounds all good and i'll take your word they are hooked up correctly :0

 

[philipbarrett]

i'll take your word they are hooked up correctly :0

I thought directional resistors were only for the copper-free oxygen cable crowd?

P

 

[noisenyc]

I thought directional resistors were only for the copper-free oxygen cable crowd?

P

P your own self. i bet you a pair of .25 old stock paper in oil caps there's a wiring error.

it would be so very rare, a matched tube failure :0

you pay shipping if i lose though.

 

[philipbarrett]

"P" is just my fast signature, since I get about work 100 e-mails a day, short for Philip, y'know.

You're on for the bet tho'

P

 

[noisenyc]

"P" is just my fast signature, since I get about work 100 e-mails a day, short for Philip, y'know.

You're on for the bet tho'

P

heheh p is usually IM for a tongue sticking out.

and yes, i got your caps right here.