RSN3305 and Technics Receiver parts replacement

[percy]

Hi, I found this chip - RSN3305 - in my Technics SA-EX140 stereo receiver. Just wanted to find out more about it and see if anybody has had any experience with it. Is this a good chip ?

Secondly, I found two sets of four 1N5402 rectifier diodes. I am assuming these are two bridges (for the two rails since this is a Class H amp ? I dont have a schematic yet). And there are two 7500uf 75V and two 2200uf 50V caps and a host of 33uf, 16uf, 10uf electrolytic caps probably in the signal path.

The receiver is more than 5 years old. Would it be worth changing the rectifiers to fast and soft recovery diodes, replacing/upgrading the psu caps and the electrolyitc caps in the signal path ? Can you recommed any make and series (example Panasonic FC) for all of these things (diodes,psu caps, signal caps) ?

Thanks!

[ofb]

here's the "big chart of technics"
http://www.vintagetechnics.com/receivers.htm

i don't know the sa-ex140, but it looks like that was entry level. just a thought, why not leave the technics in one piece and put your time and money into a simple gc? then you've got plenty of online info and support, and people do seem pretty darn happy with them.

[sek]

The older SA-GX and -EX series receivers with the lower numbers are entry level, that's right. I know that, because I bought one when I was young.

I don't really think it makes sense to invest much into this unit. If you had spare parts at hand it would perhaps be worth a try, but other than that it's a very 'average' platform to start from (80's and 90's Japanese standard industry units).

Is the receiver 'broken'? If it works, cool...
The parts you mention don't sound that bad for an industry device. There are amplifiers with less capacitance and more generic rectifiers around, so to speak.

In class H amps, the regulation/switching between the two rails is the main concern. Replacing with 8 'better' diodes, 8 high-quality capacitors and such won't increase the sound quality too much above a certain limit, as the class H circuit probably poses the main factor of sound quality - if it is a class H unit. But the price for the quality components would already be significant.

OTOH, a new GC requires an enclosure, a transformer, the boards and chips, etc. - and it has no radio built in!

You could give a replacement of bad caps in the signal path a try. However, you shouldn't approach this without the schematic. MKP/Polypropylene caps come to mind (also not inexpensive). You don't neccessarily have to replace with the same amount of capacitance, though. E.g. a 33uF electrolytic in the signal path shouldn't be replaced with a 33uF film capacitor! It depends on the schematic in such cases, probably experimenting with opamps and their circuitry is worth a try, too. When you are at it, think about leaving the 'sound regulators' and stock 'loudness' circuit out, etc.

Hope this helps,
Sebastian.

[percy]

Well it all depends on the chip. Thats why I wanted to know how good of a chip the RSN3305 is. If its a nice chip I might go ahead with these tweaks as having a receiver has its own advantages which sek pointed out too.
Actually now that I looked closely, its a '91-'92 model, I bought it in '99 or 2000.