SS Output

C Moore · Post by **C Moore** » Fri Jan 01, 2010 8:00 pm

Can somebody give me direction with this Stereo Receiver. I got it for free, and it works. It was made in 1990. I have the E-caps for the power supply, so I will just go ahead and replace those. But what about the Power Transistors? Do they go bad over time, or do they just fail? Is it a good/inexpensive idea to just replace them? I have never dealt with SS power, heat sinks, paste, etc. Is there any advice, link, tutorial you guys can give to me? I do not know/cannot read the number for that small transistor.
Thank You

David Root · Post by **David Root** » Sat Jan 02, 2010 12:26 am

Sorry no-one here is into SS power section. I wouldn't worry about them, when they go bad you'll know it!

markr14850 · Post by **markr14850** » Sat Jan 02, 2010 1:20 am

Maybe ask around at diyaudio.com?

Aurora · Post by **Aurora** » Sat Jan 02, 2010 10:27 am

Since I'm certainly more of a SS guy, I'll bite..

Transistors don't have a "lifetime" as such, - it's more of a statistical question. While heavy abuse - running constantly close to max working temp, - is often concidered as lowering life time, this is ususally far from the fact with an amp like this, which is usually operated well within safe limits. THus there is no point in changing transistors, just to be " on the safe side". Changing filter caps, may be an idea, as you already have them, but otherwise, just inspect solderings, particularly around power resistors, clean up and maybe give switches a good clean, and just leave the rest as is, and enjoy.....

fperron_kt88 · Post by **fperron_kt88** » Sat Jan 02, 2010 2:28 pm

Agree with Aurora: if it works as you expect, no real gain possible just by swapping the transistors.

One thing funny though: what looks like fingerprints on the heatsink and the general looks of the thermal grease tells that the transistors have probably been replaced already...

fperron_kt88 · Post by **fperron_kt88** » Sat Jan 02, 2010 2:54 pm

As for links or info, google sent me to ESP with "thermal grease how to transistor".

Chapter 9, 12 and 13 seem like an appropriate read for the amp you have.

If you don't have the schematics for your amp or if you want to learn more about SS amps, I found this place: http://www.ssguitar.com/. They have a newcomer section.

C Moore · Post by **C Moore** » Sat Jan 02, 2010 3:23 pm

Thank you, I forgot about ssguitar.com I think you guys have me going in the right direction now. Thanks for the info.

Structo · Post by **Structo** » Sat Jan 02, 2010 7:12 pm

Did this amp work when you got it?

There is no need to replace any of those transistors if it works.

What brand amp is it?

selloutrr · Post by **selloutrr** » Sat Jan 02, 2010 8:46 pm

if you do any work on SS heat is your enemy!!! get on and get off us a heat sink to tranfer the heat away from the component. ideally you would want a reflow, rework, station. the sensitivity of solid state is why they created wave solder so it would be as quick as possible.
WATCH YOUR SOLDERING IRON TEMPERATURE!!! best of luck!!!

C Moore · Post by **C Moore** » Sat Jan 02, 2010 9:07 pm

Structo wrote:Did this amp work when you got it?

There is no need to replace any of those transistors if it works.

What brand amp is it?

Yes it does work. It is a Scott; 25 watts per side I believe. I was with my brother when he bought it in 1990 at Montgomery Ward.
My wife has a pair of Klipsch kg1 speakers, and this little receiver seemed a good match. I just happened to have a pair of 3300/50 e-caps, so I am installing those before the get any older.
Like I said, don't know anything about transistors so I thought I would ask.
Thanks Again

Aurora · Post by **Aurora** » Sat Jan 02, 2010 9:49 pm

Heat is usually not so much of a problem as you might think. I've also been teaching electronics, and I usually say that you shoud be able to complete a solder joint in less than 3 sec - preferrably two! Good soldering techniques are one of the basic knowledges in electronics. Proper equipment and a good hand is also preferred....

Reflow ovens and stuff like that is really most usefull for surface mount components, although you should be able to hand solder quarter pitch IC's ( 25 mils pin pitch) fairly easily with some training, but of course that requires the proper equipment for the job.

30 years ago, static discharge was a conciderably larger problem with some types of semiconductors, particularly MOS IC's and some types of RF semis, - not really a problem today.......

Raja · Post by **Raja** » Fri Jan 08, 2010 7:35 pm

I've been helping a friend with SS amp and I ran across this book on Solid State guitar amps. It's pretty all inclusive.
It was written by the host Teemuk @ SSguitar site.

http://www.thatraymond.com/downloads/so ... a_v1.0.pdf

Andy Le Blanc · Post by **Andy Le Blanc** » Fri Jan 08, 2010 8:29 pm

I had to recap the PS of a gibson G-20 last night. CHEESE....

Find some IC and transistor sockets, swap components around real easy.
This morning was a epi 5-string with an active pre, amazing what one bad
diode can do..... CHEESE....

On the other hand, there are some very simple zen approaches to SS you can try.
Tube cad journal has some neat things to check out.

The Amp Garage

SS Output

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