Tube amp static sound and cutting out

cvogue

cvogue

Yes, that's Oolong. :)
Haven't played my Splawn Streetrod in a few weeks but at band practice tonight I was getting some static sound through it and it would cut out now and then... sometimes not completely but would sound really low in volume and "oomph" and then come back with a vengeance.

When it got good and warmed up it seemed fine, sounded great.

Ideas of what it could be? Preamp or power tube(s)? I've had it for about two and a half years and swapped some preamp tubes but the power tubes are original stock. Four preamp tubes and two EL34 power tubes.

Thanks for any insight!
 
1. Cables
2. Jacks
3. Sockets
4. Tubes
5. Circuit - not user serviceable

1. Try new cables, speaker and instrument. One at a time, so you isolate the problem

2. Make sure it’s not the speaker jack. The worst thing is if the output transformer is being disconnected from a proper load. Make sure the nut on the jack is tight, a loose jack means a bad ground connection. Remove and insert the plug to remove corrosion and maybe spray with some contact cleaner (a little goes a long way), check that the jack proper grips the plug, and , once on, check and seeif you apply some pressure and wiggle the plug, it doesn’t duplicate the issue. Also try different speakers cables and cabs (and the cab’s jack)

After that, check the guitar input jack(s) and the FX loop jacks. Oh, and the guitar’s jack.

3. Then try removing and re-seating every tube a few times (while amp is off) to clean corrosion off the pins. You can also spray the sockets with contact cleaner, but a little goes a long way.

Chances are the above two will fix your noise. It’s very rare a bad tube cause the signal to cut out/in completely.

4. Take a known good preamp tube and substitute it for each preamp tube, one at a time, to try and isolate a bad preamp tube.

After that, the next step is new power tubes and bias. But by this time, you may want to take it to a qualified tech.

5. Circuit...bad competent, cold solder joint, broken solder joint, etc. A tech would have to trace trough the circuit to find it.
 
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Make sure all the tubes are fully seated in their sockets...

Turn it on and get it up to temp...look at all the tubes...are they all glowing around the same brightness? Are they all about the same color? If any of them are notably brighter or dimmer than the others, or glowing hot red or blue, it's probably the issue...
 
Wyatt said:
1. Cables
2. Jacks
3. Sockets
4. Tubes
5. Circuit - not user serviceable

1. Try new cables, speaker and instrument. One at a time, so you isolate the problem

2. Make sure it’s not the speaker jack. The worst thing is if the output transformer is being disconnected from a proper load. Make sure the nut on the jack is tight, a loose jack means a bad ground connection. Remove and insert the plug to remove corrosion and maybe spray with some contact cleaner (a little goes a long way), check that the jack proper grips the plug, and , once on, check and seeif you apply some pressure and wiggle the plug, it doesn’t duplicate the issue. Also try different speakers cables and cabs (and the cab’s jack)

After that, check the guitar input jack(s) and the FX loop jacks. Oh, and the guitar’s jack.

3. Then try removing and re-seating every tube a few times (while amp is off) to clean corrosion off the pins. You can also spray the sockets with contact cleaner, but a little goes a long way.

Chances are the above two will fix your noise. It’s very rare a bad tube cause the signal to cut out/in completely.

4. Take a known good preamp tube and substitute it for each preamp tube, one at a time, to try and isolate a bad preamp tube.

After that, the next step is new power tubes and bias. But by this time, you may want to take it to a qualified tech.

5. Circuit...bad competent, cold solder joint, broken solder joint, etc. A tech would have to trace trough the circuit to find it.
Click to expand...


#1 and done!

Picked up my amp this morning because this was bothering me. Took it home and went bare bones, straight into the front and just a cable in the loop. Rock solid, no scratchiness, no static, volume consistent, all good.

Brought in the pedalboard but only used the stuff in front of the amp, still cable in the loop. Static galore! It settled down but it turns out there was a dodgy patch cable early in the chain. Replaced it, all good. Brought in the stuff in the loop, more static! Isolated it to a longer patch cable I was using, replaced it, all good! Jammed for a while (had to, the rig was all set up!) and no problems.

The one thing I noticed was a bit of hum that is very likely coming from my cheap power supply. Got a Donner knockoff of a Voodo Labs PS and it works but isn't perfect. Will get a VL one some day but can deal with this for now.

Thanks guys!
 
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