Ibanez TS10 Switching Transistors

[3124+]

Hi,

I have a TS10 with a faulty 2SK118 switching transistor. Can I use a 2SK30A as a direct replacement?

Thanks!

[R.G.]

Yes.

[3124+]

Thanks R.G. This TS10 is driving me crazy!

It works fine in bypass. When switched on, the sound is barely audible. I can hear a very faint overdriven signal, the knobs seem to function properly, and the LED works. I can pull the main circuit board out, move it around, reinstall, and the pedal works properly. I let it sit for an hour two, the overdrive mode is again nearly silent.

With the pedal switched on, I have measured unusually high resistance across Q8 corresponding with the faded signal. I have replaced the original 2SK118 with a 2SK30A but the problem persists. I suspect there is an intermittent connection related to the Q8 gate, but I am not familiar with flip-flop circuits and I'm nearly ready to give up.

http://www.schematicheaven.com/effec...bescreamer.pdf

[52 Bill]

I suspect there is an intermittent connection related to the Q8 gate, but I am not familiar with flip-flop circuits and I'm nearly ready to give up.

Monitor the voltage at Q8's gate. When it goes into fault mode does the voltage here change? Does the voltage on the other end of the diode that feeds the gate change as well?

[R.G.]

That's the place to look, 52Bill. But the gate is such a high impedance point that it's hard to measure there. Instead, measure at the junction of the diode/cap/1M resistor just across the diode from the gate. That point should go down to a few tenths of a volt above ground and then up to nearly nine volts. The low voltage corresponds to Q8 not passing signal, the high to Q8 passing signal. If the LED is working properly, the flipflop is working properly. I would suspect the gate diode, the cap to ground and the 1M resistors because of the intermittent nature of it working when taken out of the box. The other thing suspicious is that the box itself may be shorting something if it quits when in the box.

[3124+]

Thanks for the tips guys!

I may have found the problem. The pedal has a piece foam designed to keep the battery snug. I think the foam was touching some of the components on the circuit board, possibly shorting out part of the switching circuit. After removing the foam, the pedal seems to be operating reliably...