On 20 mayo, 15:40, "William R. Walsh" wrote:
Hi!

It's looking as if the IC is shot, and it seesm to be NLA.....

It's a common problem. In a lot of these 80s Technics amplifiers, the
Sanyo power amplifier IC goes bad. I've come to believe that they are
somewhat "failure prone". Interestingly enough, it seems that other
designs using these modules were more reliable--I have some Aiwa "all
in one" stereo systems and a little Pioneer receiver that use the
Sanyo module. None of these run as hot as do the Technics
receivers...perhaps another data point?

Despite being played hard at times, these units have never caused any
trouble. Of course, most of the time I happened to come across such
older Technics gear, it had already been treated badly.

There is a more sinister problem--the Sanyo module integrates speaker
protection through electronic means. The idea is that if one of the
final transistors breaks, this electronic protection circuit will
break the path between module and speaker so that your speaker does
not become exposed to a power supply rail and burn out. Unfortunately,
the protection circuit is usually destroyed and the speaker burns out.

I thought all of the Technics amplifiers that used these hybrid
modules relied on the electronic protection. After searching for a
long time to find a nice one in working condition, I discovered an
SA-929 receiver (also based on a house numbered Sanyo integrated
amplifier module) that has an outboard DC protection relay. This
should save the speakers if anything goes wrong.


I think the reason could be the supply voltage. Seems they can take
anything from 27 to 40-odd volts, which might explain the varied
reliability.

I too was surprised at the lack of protection visbile in this amp.
there's only a resistor separating the o/p from the speakers!
ironiocally in this case, the protection seems to kick in far too
early - muting the o/p even when the sound is barely audible.

i just took a look in my spres box and found an STK 4121 II which,
according to a quick look at the dateasheet here :
http://www.datasheetcatalog.org/data...0/106635_1.pdf
has the same pinout as my 4152 ii

Might this work as a drop in replacement? the output would only be 15
watts, but better than nothing.....
-B