Twin cracklin'

[nikgtrnik]

The following symptom occurs on my Twin Reverb every time.
Starts off quietly and after 5-10 minutes of playing, a crackling low-mid noise occurs. Turning all pots on 0 does not affect the noise at all. The tubes on the amp are fairly new and working fine-I checked them on a Super Rev. Any clues what's generating the crackle?

Thanx,
Nick

[Tberg]

Could be bad resistors, possibly the plateresistors, or soldering, since it happens when the amp has heaten up. Could also be small current traveling between the boards, common in old dirty amps that's been sucking up fluids for many years.

[Randy Magee]

If it's an older Twin the carbon comps used as plate load resistors, especially the one on the PI, are probably the cause...

[nikgtrnik]

It's the 65 Twin remake. Not that old and not that dusty either...

[rp]

Likely what the others said, but maybe retensioning tube sockets? DRAIN THE CAPS first, check that it's unplugged and check again. Slow and easy, you can ruin them. Pull out the pre tubes too and reseat 2-3 times to clean the contacts. Modern Chinese sockets have given me problems like this, from now on only Belton, QQQ, or NOS.

[selloutrr]

Replace the 100k resistors in the preamp

[butwhatif]

pull the ax7 tubes starting w/ v1 on down the line--to see where it is

[tubeswell]

Intermittent crackling like that can be a (sure) sign of output tubes on the way out. Did you try a fresh set of 6L6s? Tubes are always the first thing to check in troubleshooting.

[selloutrr]

It's the 65 Twin remake. Not that old and not that dusty either...

If it's pcb resolder ALL contacts you have a cold solder point.

[marshamps]

The reissue 65s are worse than the original 1965s for noisy, crackling, poping plate resistors! Replace them with modern production 1 watt 100K or metal film realtors.

[Structo]

Before you tear the amp apart or heat up the iron, try a few different preamp tubes.
Several times when I thought, oh no, somethings broke or fried, it was just a preamp tube on it's way out.
Although the times that was true it was generally crackling when the amp was first taken off standby.

What I'm getting at is, eliminate the simple stuff first.
Tubes should always be the first suspect.
Then sockets, then plate resistors, etc.

Good luck.

[nikgtrnik]

Thanx 4 the input.
Pulled out V1 and the crackling is now barely audible. Amp sounds sharper now too...

[Wiktor D]

Do the chopstick test on the wiring on the sockets, I just had one that had a PI whose cathode connection was never soldered