Tecnics SU-Z1 to refurbish

[effebi]

I have an old Technics SU-Z1 stereo integrated amplifier that is (again) blown. For precedent experience, I know that one channel of the STK amplifier chip inside is short. Also one Re is gone, and the PSU needs repair. Nothing really difficult, but... I do not want to repair it as is, because it is a very silly weak system, prone to get hot and fail.
But, since the aestethics is still very nice (lovely analog VU-meters..), I would like to:
1)Rebuild /recap the PSU
2)Bring out the preamplified signals, to use it as a pre-only.
3)Build in a rugged SS OP, with proper H/S .

For this I would need the SCHEMATICS/SERVICE MANUAL. Anyone can help?

BTW I remember that one eminent member here (I beleieve Wahab) had it in the past and found some design problems. I will be grateful if he can share... In the worst case I'll keep the box and the trafo and throw the rest.
Thanks in advance
effebi

[sakis]

i have various SU schematics but not the SUZ 1 may 2 is close .... by the way this is a drama amplifier i think way to many ic to unable to control the obvious ...

i see a pair of neat p3A boards installed inside pretty fast ha ha ha

[jaycee]

STK2038 output IC? They were crap, forever blowing up. You'll probably find it's connected to an AN7602 IC for the frontend. If that's the case, look at what's connected to pin 2 and 17 of the AN7602

[effebi]

Originally Posted by sakis

i have various SU schematics but not the SUZ 1 may 2 is close .... by the way this is a drama amplifier i think way to many ic to unable to control the obvious ...

i see a pair of neat p3A boards installed inside pretty fast ha ha ha

Yes, spot on. I'm going to order a couple of PCBs from ESP...
but I'll want to save the pre-ampli, volume,selectors, etc. and a schematic would cut down the times to 1/10... So if you can send me the SU-Z2 it may help anyway.
Thank you
effebi

[effebi]

Originally Posted by jaycee

STK2038 output IC? They were crap, forever blowing up. You'll probably find it's connected to an AN7602 IC for the frontend. If that's the case, look at what's connected to pin 2 and 17 of the AN7602

They are crap, defenetly they are. I was repairing it around 1984 (got original spare part from a friend working for Panasonic). I also redid the PSU putting serious diodes in place of the toys that where burnt.
Then it went to my bro that had blown it right away in a couple of years. Now it is sitting sadly in a rack from more tha 10 years, and I want to do something. Only the case is too nice to be trashed. I found the STK on ebay, but I do not want that s***t again. The only problem is that I would have to find out the connections using only the STK schematic.
Thanks a lot for the infos on the AN 7602, I'll have a look.
Does it act as a VAS stage as well or only a pre-amplifier? It would be too nice to slam there only a CFP pair wired on the H/S!

effebi

[jaycee]

It's inputstage and VAS. I dont know if the 7062 is any good by itself. I'd build a total replacement amplifier TBH.

[sakis]

of course no prob schematic is available email me .

kind regards sakis

[effebi]

Originally Posted by sakis

of course no prob schematic is available email me .

kind regards sakis

Thank you very much, Sakis, it was very kind of you.

[effebi]

BTW, I discovered that the output chip is a STK2028 (probably a reduced power version of the 2038) and that the Input/VAS stage is done by 2X AN7060 chips, that are mono (and SIL )versions of the 7062
The bad news is that the tone controls go through the 7060 as well, so it has to be kept if this function has to be preserved. I believe that was the problem found by Wahab (sorry if i do not remeber well) as well.
Considering that at the end this would be something like a 25+25 W amplifier, I am not so sure it is worth the effort.
effebi

[Tekko]

I cant see how you can be blowing stk modules like this. I've built amps with these a couple of times and literally abused the **** outta them and never had one blow.

I even removed the heatsink once, took 30 minutes of overheating before the thing finally died.

I'd say these modules are pretty darn rugged and reliable. Though i've only dealt with the low power ones below 45 watts.

However i don't see why these would be any less reliable than any discrete design, since they after all are little discretely built amplifiers inside the plastic.

Heres my latest play with these modules: http://www.youtube.com/watch?v=yAMbthSlQOA