TS808 clone pops when turned on

[yeeshkul]

I made TS808 (GGG board) time ago and i recently realised it pops when turned ON (turning OFF doesn't cause any pop). It is not the LED (i checked on that).
There is pull-down res. before the front cap so i have no clue what is going on . Would anyone have any idea?
thanks
Jan

[fifi]

hmm, i had once the same issues with my ts clone. in my case it only poppen when something was connected into input, if not everything was ok.
finaly i'd found a hairthin solder brigde to ground somewhere, which i made when i removed the iron from component.

maybe that helps you out, try going rough the layout with an ohmeter and check if connections are all ok and there's no short.

regards

[Paul Marossy]

I built the GGG TS-808. I had the same problem. A pulldown resistor on the input and output fixed that.

[yeeshkul]

Paul there already is the 10k resistor (R13) to the ground after the output cap though .....

[Auke Haarsma]

You may consider increasing R13 (Rb on tonepad's layout) to 1M for pulldown.

[yeeshkul]

You may consider increasing R13 (Rb on tonepad's layout) to 1M for pulldown.

Auke i will try it - but how can this help? do you mean that bigger resistance to ground can help to lead the leaky-cap voltage down better?

[Auke Haarsma]

What I understand is that e.g. if a 1M pulldown resistor on the input and output doesn't do the trick, it may help to use a bigger resistor, like 2M2. Since you use 'only' 10k, my first guess would be to increase the value of the output pulldownresistor. 1M for starters.

[yeeshkul]

i will try it although it makes me completely confused ...

[Paul Marossy]

I'm going off of memory here. That's what I seem to remember doing, but maybe I'm thinking of another project.

[yeeshkul]

So I tried this:
- changed the input pull-down from 1M5 to 2M2
- increased the output resistor that work like a "pull-down" from 100 to 2M2

and it still pops when turned on

also
- there is no DC on input or output
- it is not the LED (i disconnected it for testing)

does anyone have any idea what can cause the pop?

[yeeshkul]

hmmm ... now i changed the 3PDT switch to DPDT (no LED) and there is no pop ... 
strange

[yeeshkul]

actually can the position of the 4k7 LED resistor (ground leg / voltage leg) influence possible pop?

[yeeshkul]

all right, sorted.

I changed the wiring of 3PDT from the "difficult one" with the input grounding (when off) to the "simple one" (LED wires on the centre lugs) and there is NO POP any more. 

I have no clue why, but it works.

[Paul Marossy]

all right, sorted.

I changed the wiring of 3PDT from the "difficult one" with the input grounding (when off) to the "simple one" (LED wires on the centre lugs) and there is NO POP any more. 

I have no clue why, but it works.

In any case, I'm glad you got it figured out! I only use the grounded circuit input true bypass switching in certain specific cases. Weird that it is apparently the source of your popping problem...