JCM 800 2204 NO SOUND
Moderators: pompeiisneaks, Colossal
JCM 800 2204 NO SOUND
Hi Guys,
I hoping someone can give insight as to whats wrong. i had my JCM800 clone working nice and wanted to try a different opt over my hammond.
The wiring was different between them and I some how wired it wrong.
When i turned the amp on there was a loud pop than silence! NOT GOOD.
I checked fuses and nothing blew. So i pulled out thr OPT and re-installed the old hammond again (correctly). However i still have NO SOUND. something let go? ideas..
there is no burnt parts, or traces, tubes are good & light up. Any suggestion on where to look. maybe my choke is gone.
I hoping someone can give insight as to whats wrong. i had my JCM800 clone working nice and wanted to try a different opt over my hammond.
The wiring was different between them and I some how wired it wrong.
When i turned the amp on there was a loud pop than silence! NOT GOOD.
I checked fuses and nothing blew. So i pulled out thr OPT and re-installed the old hammond again (correctly). However i still have NO SOUND. something let go? ideas..
there is no burnt parts, or traces, tubes are good & light up. Any suggestion on where to look. maybe my choke is gone.
Re: JCM 800 2204 NO SOUND
Got a mutimeter? I'd check al the high voltages ect.
Stew
Stew
Re: JCM 800 2204 NO SOUND
Pull the tubes and make sure you're getting high voltage to everywhere you should. Make sure also that you're seeing it at the output tube sockets on the plate and screen grid pins (3 and 4) so you know it's passing through the OT primary and the screen resistors.
If you have 1ohm bias resistors tied between pins 1 and 8 and the chassis then check that these are intact too, as an overload situation could have taken them out.
If you have 1ohm bias resistors tied between pins 1 and 8 and the chassis then check that these are intact too, as an overload situation could have taken them out.
Re: JCM 800 2204 NO SOUND
check the speaker first..maybe it was the thing that popped. If speaker is ok.. need to do as others posted. maybe blew a rectifier or cap..When i turned the amp on there was a loud pop than silence! NOT GOOD
Re: JCM 800 2204 NO SOUND
Good point! if the tranny was miswired there might have been a good chunk of DC going to the speakersRichie wrote:check the speaker first..maybe it was the thing that popped. If speaker is ok.. need to do as others posted. maybe blew a rectifier or cap..When i turned the amp on there was a loud pop than silence! NOT GOOD
Stew
Re: JCM 800 2204 NO SOUND
Could also have been a filter cap go if you had the polarities wrong.
Lots of possibilities, but most of them should be pretty obvious by the look of them.
Lots of possibilities, but most of them should be pretty obvious by the look of them.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: JCM 800 2204 NO SOUND
Great replies everyone and thank you!
The first thing I did was check speakers, thier good. Phew!
I do have the 1 ohm to ground and they looked ok., but I will re-check.
I'm going to open it up tonight and take some readings.
I will look at the pins closer on the tube sockets.
cheers.
The first thing I did was check speakers, thier good. Phew!
I do have the 1 ohm to ground and they looked ok., but I will re-check.
I'm going to open it up tonight and take some readings.
I will look at the pins closer on the tube sockets.
cheers.
Re: JCM 800 2204 NO SOUND
Be sure to discharge the filter caps before going inside the chassis.
Was this OT the type with the funky secondary wiring?
Was this OT the type with the funky secondary wiring?
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: JCM 800 2204 NO SOUND
it looks like the powert trans let go. no secodary voltage.
I have orderd a new one. wait and see.
I have orderd a new one. wait and see.
Re: JCM 800 2204 NO SOUND
Does this amp have an HT fuse?
Be sure to correct whatever was wrong that blew it up if it is indeed dead.
Be sure to correct whatever was wrong that blew it up if it is indeed dead.
Tom
Don't let that smoke out!
Don't let that smoke out!
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Re: JCM 800 2204 NO SOUND
It seems odd you tubes light up but no Hv output. Just an observation.
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Re: JCM 800 2204 NO SOUND
If tubes light up seems your filament windings good and HV windings gone? Just an observation.wawa wrote:Hi Guys,
I hoping someone can give insight as to whats wrong. i had my JCM800 clone working nice and wanted to try a different opt over my hammond.
The wiring was different between them and I some how wired it wrong.
When i turned the amp on there was a loud pop than silence! NOT GOOD.
I checked fuses and nothing blew. So i pulled out thr OPT and re-installed the old hammond again (correctly). However i still have NO SOUND. something let go? ideas..
there is no burnt parts, or traces, tubes are good & light up. Any suggestion on where to look. maybe my choke is gone.
Re: JCM 800 2204 NO SOUND
I agree its strange to loose the hv and still have filaments.
I tested the choke and it ok.
I have corrected the HT fuse.
I will keep you posted.
I tested the choke and it ok.
I have corrected the HT fuse.
I will keep you posted.
Re: JCM 800 2204 NO SOUND
Its not strange to loose high voltage and have the filaments working. This is what happens when the HT fuse is shorted. This fuse will usually short if you blow a power tube.wawa wrote:I agree its strange to loose the hv and still have filaments.
I tested the choke and it ok.
I have corrected the HT fuse.
I will keep you posted.
So you have replaced the HT fuse with a fast acting fuse correct? (not a slo blo). If so, have you taken a high voltage reading to see where the high voltage stops?
Forgive me if I over looked it but did you reinstall the original known-to-be-good OT?
Re: JCM 800 2204 NO SOUND
Hi Trace,
Thats correct i installed old O.T. which was good.
The Power trans is ordered 2 weeks away at least.
proper fuses installed.
I will advise when I install new power trans. Thx
Thats correct i installed old O.T. which was good.
The Power trans is ordered 2 weeks away at least.
proper fuses installed.
I will advise when I install new power trans. Thx