STK3042 STK3044 STK3062 STK3082 STK3102 STK3122 STK3152 II III IV V looking for reliable Substitute

[Depaj]

I think I just found the problem, I grounded the back of the STK board and all oscillations are gone, even with the extra capacitance on C305 and 355 removed. hat just leaves me with the question, how do I solder to the aluminum plate, any suggestions ?

 

[anatech]

Not surprising at all. Make sure the heatsink is also grounded.

It should have been made to provide a ground. You could remove it and put in a tapped hole, drill a hole behind if mounted to a heat sink. Then screw a ground wire to that screw (use a tab) and your circuit common.

 

[NareshBrd]

Beware of galvanic corrosion, use mechanical fastening to aluminum, which needs high temperature and acid etching to solder....so use a brass or steel tab to bond to aluminum, and use copper or stainless steel wire for connecting to Earth.

I would not try to solder a thick wire to a populated aluminum back PCB.

 

[as_audio]

I think that the drawing in post 14 is wrong re the transistors to pin 6 and pin 10 of IC 301. These must be PNP devices.

 

[tiefbassuebertr]

What about the idea to create a more easy STK replacement based on the el cheapo ? - go to
https://sound-au.com/project12a.htm
some modifications on the genuine circuit topology are necessary:

1) modification for symmetric voltage supply without capacitor in series to the speakers
2) because absence of a differential input stage the use of an offset servo is necessary.

Due the lower open loop gain factor there is much more lower risk of oscillation.

 

[as_audio]

No. The way to go is with a simple driver stage as in post 14 or in other words a contemporary replica of the original circuit.
By the way I was able to stabilise operation of these modules with additional heat sinks and never had any complaints.