Stk3082

if i remember

well this should be a driver stk ic mostly used as a driver for a couple of transitors for sansui amplifiers .....

nice circuit ...produces a lot of power but SOA of the all device is way overestimated resulting this b1000 amps to fail quiet easy .....

i have a broken one ,,,,,, never bother to fix it ....if i ever do i will replace trafo to something lower for more safety ....

regards sakis
 

Kaplaars

Member
2010-07-19 12:48 am
Arnhem
Received your PM, thanks :) But, aye, I unfortunatelly need the STK3082 (I). The latter versions lack internal compensation caps and resistors. Chances of oscillation arise when using a newer version, than the original one which your amplifier once had. So they are not fully backwards compatible.

It is possible to add the compensation caps and resistors externally. I already am using a STK3082 III this way, but it is not ideal, so I was searching for a previous version instead :).

Here is some more info about the different versions:

http://www.diyaudio.com/forums/chip-amps/170525-sanyo-chip-amps-v-ii-xi-differences.html
 

djk

R.I.P
2001-02-04 4:23 am
USA
The 3082 has four internal compensation caps in the module, between pins 3-4 (12-13) and between pins 4-6 (10-12).

The 3082 II has only two internal compensation caps between pins 4-6 (10-12).

The 3082 III has no compensation.

The 3-4 (12-13 cap is about 68pF with 470Ω in series with it, the 4-6 (10-12) cap is about 15pF.

It's not that hard to add the compensation your circuit needs.
 

Kaplaars

Member
2010-07-19 12:48 am
Arnhem
Yup, it is pretty common that STK's will fail. They cause a lot of trouble in many amplifiers after a few years. It is not that the STK's are bad by design, but unfortunatelly many STK's are pushed to their limits which will cause them to fail after a while. More cooling is for most of them necessairy. Additionally here in Holland mains voltage has been raised from 220VAC to 230 / 240VAC. This will cause a STK to degrade even earlier due to an higher applied voltage and thus higher dissipation.

I've added extra cooling and changed the transformer to 240V setting, so I hope the new STK will last longer. But for me adding the compensation circuits externally is not a very professional solution (messy setup, I am a bit of a perfectionist about layout :) ), although it seems to work fine right now. Also leads in the compensation circuits for version one are much shorter (because this circuit is mounted inside), which will result in less chance of oscillation. Although I think this chance will be negligible, since some amplifier use version III with the compensation circuits mounted on PCB.
 
Just a quiet warning.... lots of the recently available STK-s are fakes. Had a bad experience with the 3082-II, the original one in the amp worked until warmed up, then started to make terrible cracking noise (specially when gently knocking on them) activating the protection. The new ones I purchased from a local store (2 of them) refused to work, protection remained on, no sound, no bias voltage for the output stage, nothing... Finally I glued a large heatsink on the original, now it seems to work well. So be careful....
 

djk

R.I.P
2001-02-04 4:23 am
USA
218798d1302941303-crest-audio-v1500-hybrid_board.jpg


The Crest solution to NLA STK voltage amplifiers.
 
Ai dragonsweed, that does not sound pretty. Do you have a picture of your fake STK's? Maybe there are some differences from the original ones to spot? I was able to obtain one original STK3082 from the USA. Well, it seems original, because the amp rocks again without any flaws and I can't spot differences from the original :)
 
Unfortunately I threw the "fake" ones out, so I cannot post pictures of them. But as far as I remember, the bogus ones have a 3 letter/number code printed on the lower right corner, something like P3T, while the originals have either a four number, or three number/one letter code printed (like 8719, or 1H30). Also the
bad ones have no printing on the metal back plate, while the originals do have a rather long code printed on them.