Simple SE - one channel intermittent problem

[astrodog]

I have recently completed a Simple SE, and am very happy with it - I think I may have a problem though.

Intermittently one channel - always the same channel, will get quite distorted, and even almost completely so silent. This has happened every time the amp has run for more an hour or so.
Just now it was doing it (one channel extremely distorted), I turned the power switch off and back on, and all was fine (was off for barely enough time for the heaters to go out), and still is now......

Source is an iPod (headphone socket) as I haven't done a volume pot yet - I was hoping it was the iPod with a problem, but this latest occurrence makes me wonder..... all speaker connections are tight.

am using EL34, B+ 440V (Hammond 374BX), Rk 770ohm

any thoughts?????

TIA, Lee

[Frank Berry]

Swap the EL34 tubes between channels. Does the problem follow the tube?

[oldmanStrat]

trace the signal path from the bad channel - starting at the input. (swap L&R from the ipod)

Check cables, components (bad solder on the PCB?) - loose connections on the OPT's... It could also be a bad gain tube if everything else is fine.

[n_maher]

Originally posted by astrodog
I turned the power switch off and back on, and all was fine (was off for barely enough time for the heaters to go out), and still is now......

Just an FYI, that is a horrible idea with tube amps, especially if your SimpleSE is tube rectified.

[whitelabrat]

What's the mileage on your tubes? I'd also suggest swapping out the 12AT7 to see if that changes anything.

[dubdub]

I had the same problem and it turned out to be my ipod dying in one channel however the following possibilities should be considered:


1/bad tube
2/tighten up any conncectors/wires that are loose
3/tidy up internal wiring as best as possible
3/test the coupling caps, one might be bad


however, I find the problem is often the most obvious (bad tube is always 1 suspect)

[astrodog]

Thanks for the tips - will start switching the input connectors today, although it hasn't played up since the on/off switching??
Is it usual/common for problems to occur intermittently like this??

[astrodog]

Originally posted by whitelabrat
What's the mileage on your tubes? I'd also suggest swapping out the 12AT7 to see if that changes anything.

Mileage - 3 weeks.....

[rknize]

Could also be a defective cathode resistor that opens when sufficiently heated.

[tubelab.com]

Likely causes are:

Bad tube:
Swap the EL34's and see if the problem migrates to the other channel. Try another 12AT7.

Loose socket pin:
After the amp dies, CAREFULLY lightly wiggle each tube. If moving a tube fixes it, check the soldering where the socket meets the board, if OK, GENTLY squeeze each pin in the socket with a pair of tweezers so it grips the tube pins tighter. Some JJ EL34's had undersized pins.

intermittent solder connection:
Go over the board carefully.

Screw not tight on wiring terminal:
They have a way of losening in the first month after construction.