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Title: No OD - UPDATED Post by: bobgoblin on August 22, 2010, 05:22:37 AM So, at rehearsal today my 50w OTS just cut out. After troubleshooting tubes, speakers, etc, I switched the OD off at the pedal. To my surprise, I had sound again, just no OD. The PAB still works, but even with the pedal disconnected I cannot manually switch to OD-I get no OD sound at all, just silence. OD off, even with PAB, sound. Anyone care to help me out, suggestions or whatever. Thanks!
Title: Re: No OD Post by: boldaslove6789 on August 22, 2010, 05:35:59 AM Have you tried replacing the OD tube ? I would try that........
Title: Re: No OD Post by: bobgoblin on August 22, 2010, 06:08:27 AM Yeah, I've replaced v1 & v2 & replaced he PI with a known good tube. Thanks, tho!
Title: Re: No OD Post by: bluesfendermanblues on August 22, 2010, 08:11:16 AM Check the wires to/from the OD relay.
Title: Re: No OD Post by: bobgoblin on August 22, 2010, 10:03:42 AM Thanks! I'll do that later today.
Title: Re: No OD Post by: bobgoblin on August 23, 2010, 02:10:30 AM Update:
Every tube I've tried produces the same results. Pin voltages are off, though, so other than touching up some solder joints on V2, I'm at a loss... Any other suggestions? Title: Re: No OD Post by: bluesfendermanblues on August 23, 2010, 05:21:35 AM Update: Every tube I've tried produces the same results. Pin voltages are off, though, so other than touching up some solder joints on V2, I'm at a loss... Any other suggestions? Check the power supply to V2, is it broken of somewhere? Title: Re: No OD Post by: bobgoblin on August 23, 2010, 06:51:50 AM Thanks, Blues, I appreciate all your help. I'm new to all this stuff, so tracing connections is very frustrating. A member of the Amp Garage & TGP known to most D-style players has advised that perhaps the 4.7uf cathode bypass cap has shorted...now to find that & trace the power to V2.
FWIW, Here are my pin voltages on V2: Pin 1: 185v Pin 3: 1.645v Pin 6: 4.29v Pin 8: 4.28v Argh!!! Title: Re: No OD - UPDATED Post by: bobgoblin on August 23, 2010, 09:21:38 AM After chasing the power supply to V2 down, I tested the 150k resistor that feeds the 5uf/180k...measurements are out of range, badly. So, tomorrow, off to the electronics store for a new resistor & then back to rocking! (Hopefully...)
Title: Re: No OD Post by: bluesfendermanblues on August 23, 2010, 09:52:44 AM Thanks, Blues, I appreciate all your help. I'm new to all this stuff, so tracing connections is very frustrating. A member of the Amp Garage & TGP known to most D-style players has advised that perhaps the 4.7uf cathode bypass cap has shorted...now to find that & trace the power to V2. FWIW, Here are my pin voltages on V2: Pin 1: 185v Pin 3: 1.645v Pin 6: 4.29v Pin 8: 4.28v Argh!!! Pin6 & 8 are way out of range....so your problem is V2b Title: Re: No OD - UPDATED Post by: bluesfendermanblues on August 23, 2010, 09:53:43 AM After chasing the power supply to V2 down, I tested the 150k resistor that feeds the 5uf/180k...measurements are out of range, badly. So, tomorrow, off to the electronics store for a new resistor & then back to rocking! (Hopefully...) 5uf/180k ?????????? you need 5uf/2.2k Title: Re: No OD - UPDATED Post by: bobgoblin on August 23, 2010, 10:48:19 AM Yes, sorry, I meant to type the 5uf cap and the 180k resistor that follows it (precedes the 100kL pot).
Title: Re: No OD - UPDATED Post by: bobgoblin on August 23, 2010, 10:07:29 PM Well, I replaced the resistor, but it was a bust, the problem remained. Nik advised I should remove the snubbers, so off they came & now I'm back in action. Only question is, is there any harm in running the amp at gig volumes for a while until I receive some new parts in the mail?
Title: Re: No OD - UPDATED Post by: bluesfendermanblues on August 23, 2010, 10:57:40 PM Ok, so the snubbers was the problem ?
You can easily run the amp without snubbers, although it will be pretty harsh in OD mode. Title: Re: No OD - UPDATED Post by: bobgoblin on August 23, 2010, 11:32:12 PM Thanks, Blues, was just informed 250pf - 270pf is good (RF's values). I have a 390pf on v2a & a 330pf on v2b for now...we'll see how it works out.
Thanks for all the help! Title: Re: No OD - UPDATED Post by: JD0x0 on August 23, 2010, 11:54:08 PM Thanks, Blues, was just informed 250pf - 270pf is good (RF's values). I have a 390pf on v2a & a 330pf on v2b for now...we'll see how it works out. Thanks for all the help! Im running no snubber on V2a and 830pf on V2b gives nice character IMO Title: Re: No OD - UPDATED Post by: bobgoblin on August 24, 2010, 12:26:47 AM Thanks, JD, I'm gonna leave it as-is for now & maybe experiment once I have a viable back-up amp.
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