Debugging help, please - 6V6 ODS 102 (not a new amp)

[mlp-mx6]

This is an amp that has been working fine for several years. It's a 102-circuit with 6V6s and a built-in D'lator.

Suddenly it has developed a strange crackling/popping sound that I cannot trace. Audio file is the clean channel, up pretty loud. There's nothing obvious in looking at the amp - no burnt parts or anything like that. Also the other extra sounds you hear are cone cry, which is why this speaker cab stays home.

Anyway, if anyone has heard this kind of thing before and can offer guidance, or you're just smart and know where I should look, I'll be most grateful for the help.

Take care,
Michael

[jelle]

Pics? Lemme see what you did....

[dorrisant]

I have had plate resistors do that before... Vibrato channel on a Deluxe reverb. They were CC. Changed them out, problem gone... Same area of the fretboard too.

[martin manning]

Try swapping tubes first. Any time a disturbance depends upon signal frequency some kind of resonance is likely. It could be mechanical or electrical or both.

[mlp-mx6]

I should've said - I've replaced each preamp tube individually, and the power tubes as a pair. It doesn't seem to be the tubes.

Here's pics. It's crowded in there, I know.

[martin manning]

Since it was working previously, it wouldn't be a lead dress issue. More likely a failed component. A scope would be the tool of choice for isolating it.

[67plexi]

I have had a rash of bad china tube sockets make sure the pins are tight.
You don't have them Belton have to be the worst arcing inside the socket.

[mlp-mx6]

I'll keep you posted as I continue (sporadically) to research this. Thanks, folks.

[jelle]

Many people have reported issues with the RV4 large sealed pots. Are they intermittent? You can take the covers off easily if you take them out, then Deoxit.

Other than that, no idea, soldering looks good, you are not afraid to heat the joint up enough.

Otherwise a electrolytic cap?

[mlp-mx6]

Jelle,

Thanks. Yeah, that's what I think I may be down to. I'll try to use my scope to locate the failure.

Regards,
Michael

[glasman]

Since it was working previously, it wouldn't be a lead dress issue. More likely a failed component. A scope would be the tool of choice for isolating it.

I agree, hook a scope to the send jack of the loop to determine if the noise is before or after the loop.

You can also plug your guitar straight into the return jack of the amp and use the return control as a volume, one again to determine if the issue is before or after the loop.

Gary

[glasman]

To my ears it sounds more vibration induced. But that is just me, not sure how you are testing it.

Also check your send and return jacks, if they are switchcraft, make sure the switched connections are truly O ohms. Been bit more times than I would like to admit.

Gary

[David Root]

+1 on that! I had that problem more than once a few years ago with Switchcraft send & return jacks.
I changed to the Mil-Spec Switchcraft jacks, cost twice as much but have solid silverplated contacts on the shorting pin--no more problems. Also I think the steel is stiffer too.
I now use them exclusively on input jacks and OT output jacks as well.

[glasman]

+1 on that! I had that problem more than once a few years ago with Switchcraft send & return jacks.
I changed to the Mil-Spec Switchcraft jacks, cost twice as much but have solid silverplated contacts on the shorting pin--no more problems. Also I think the steel is stiffer too.
I now use them exclusively on input jacks and OT output jacks as well.

Do you know the switchcraft number for the mil spec parts?

Thanks,
Gary

[martin manning]

This: http://www.switchcraft.com/productsumma ... Parent=399