e-licktronic Forum

Hi e-licktronic / Vincent,

My Hi Tom seems to be coming and going!

The fault is the Hi Tom is intermittently only getting the White Noise component (Hi Conga seems fine).

Historically when I first powered up the Yocto the Hi Tom was fine, then it went wrong. I reflowed all the solder joints and it came back.
It was OK through my final tests and tweaks, prior to putting the boards in the case.
Once I had put the boards in the enclosure it went wrong again, so I thought it might be a faulty jumper or that I had stressed a solder joint.
However it came back of its own accord and seemed fine for a session.
Next time I turned on the Yocto it was gone again.

Where should I put my Multimeter to check the trigger?
What components could be the culprits and can I check them prior to replacement?

Thanks in advance for your assistance, otherwise I am having a great time with the Yocto

Dear vco2lfo,

lfo2vco wrote:Where should I put my Multimeter to check the trigger?

It will be hard with a multimeter to check trig signal, better with a scope at Q57 emitter.

lfo2vco wrote:What components could be the culprits and can I check them prior to replacement?

I think the slide switch is the problem. Have a look on slide switch solder

Best regards,
e-licktronic

e-licktronic wrote:

lfo2vco wrote:Where should I put my Multimeter to check the trigger?

It will be hard with a multimeter to check trig signal, better with a scope at Q57 emitter.

OK, I don’t want to muck anything up and as I’m an electronics novice I wish to check exactly what I am doing...

So I will connect the red lead of my sound card scope to the emitter of Q57, and the black lead to the base of Q57. Then I will play a High Tom pattern and record the resulting output to the scope.
Looking at Q57 from above with the flat side facing away from me the legs are E C B, is that correct?

Thanks again for your assistance.

P.S. Oddly the High Tom has come back, so I will have to wait till it goes again before I can test anyway!!

Dear Lfo2vco,

lfo2vco wrote:So I will connect the red lead of my sound card scope to the emitter of Q57, and the black lead to the base of Q57. Then I will play a High Tom pattern and record the resulting output to the scope.

Red to Q57 emitter, black to GROUND.

Here is the correct pin number of 2sa733:


Best regards,
e-licktronic