finally an electrostatic transportable

[Shawn]

4 hours ago, dingding123 said:

17k smd resistors are quite hard to find. Would you recommend 20k or 15k ohm resistors?

I didn`t check the schematic. However, the input resistors(Signal input) shouldn`t be a probably if you go with 15k or 20k.

[dingding123]

Has anyone tried building this? Not sure if it's just me - after power on, the board overheats within a minute and then comes the magic smoke. PSU voltages are correct but output balance (i.e. L+ vs L-) goes from -2 to -60v quite quickly then suddenly normalises to around 4v).

Pretty sure there are no shorts or issues with soldering on my board...

[kevin gilmore]

i am aware of the overheating issues.  i have an assembled board coming to me to look into this.  something clearly has changed from the original parts i used and there is some positive thermal runaway that did not happen with the prototype. there is a later version board now, 4 layers, still does not fix the problem.

putting 12v zeners in series with the 1.1meg resistors may introduce enough negative thermal compensation. otherwise the bias needs to be trimmed a lot.

hate the parts situation i do.

[kevin gilmore]

you are aware that you need a heatsink touching all the sot transistor.  still with heatsink it typically can take about 5 minutes to reach high temps.