Realistic STA-2000 repair

[muskgrave]

hello,

My Father in law gave me their old Realistic STA-2000 stereo amp to see if perhaps it could be repaired. He bought them with a pair of realistic mach one speakers many years ago. He still has the mach one's, but no other amp he has ever bought pushed the speakers as well as the original amp (75 watts of clean power across the whole freq. spectrum)

As far as he knows, the power amps were damaged when the unit experienced a power surge. I was wondering if I can get any information on this unit. Would they perhaps have fuses inside or some other parts that could be easily replaced?

[lineup]

It can have several fuses.
First check if they are okay.
It is easy using an Ohm meter.

[muskgrave]

doh!

ok i'm an idiot...right by the power plug there is a screw-off peice that houses a fuse..i popped it out and it is blown.

So if this outer fuse blew when they got the power surge, technically the amp itself should be fine correct? Is it possible for that nanosecond between when the surge comes into the amp and the fuse actually breaks it can damage other parts inside the amp?

Also, the fuse says 7A, 250V but on the outside of the receiver it says that 7A, 125V should be used. I've heard before that the amperage is what you really need to worry about, but just wanted to see if the 250V on the amp would give it more of a chance to harm the receiver before the amp blew.

i'm sure you have already come to the correct assumption that I don't know a whole lot about circuits ..i understand the fundamentals of a fuse, but don't know some of the variables like "could the fuse blow and the stuff still be damaged...etc.."

so obviously the first thing to do is replace this fuse and plug it in. Should Radio shack have a 7A, 125V glass fuse?

[muskgrave]

ok, so i went to radio shack and bought some fast 7A, 250V fuses. I put the first fuse in, plugged the unit up and turned it on. The lights came on at first and then almost immediately turned back off. I pulled the fuse out and it had blown already?

Does this give any indication of where I should look next? Could the power cord itself be bad? It doesn't look bad anywhere...any assistance would be greatly appreciated.


..well! i just noticed something else about the unit. The plug is a standard 2 prong (no ground) power plug, but on the back of the unit there is a thumb screw terminal that says "ground" on it. I'm assuming I should hook a copper wire into this, but where should it go?

thanks again...

[anatech]

Hi muskgrave,
A fuse can take a while to blow on an overload. 2 min. even depending on the percent over current.

Your set may have damaged rectifiers or a damaged output section. Do not instal any more fuses or you may kill the power transformer, not to mention extending any other damage.

If you don't know much about electronics, take it into a good shop. Do not take it to a friend or inexpensive repair guy! Almost for sure that will either cost you more $$$ or kill the set forever. I don't have very much confidence in the Radio Shack service centers either.

If the repair person is going to use ECG or NTE replacement parts, take your set and run out of there! Originals or good subs are not hard to come by. Actually, if you even see an NTE or ECG replacement manual in the shop, you are in trouble.

-Chris

[anatech]

Hi muskgrave,
To answer your other question, that ground screw is for a turntable. It is normal for that earlier equipment to have a two wire AC plug.

-Chris

[muskgrave]

thanks for the quick reply..it might be better for me to just try and find a used stereo power amp. Supposedly this pushed 75watts x 2 but apparently the newer receivers that say they push 110w only do so at certain "easy" frequencies...his mach one's sound pitiful with this 110W surround sound receiver

[anatech]

Hi muskgrave,
You know, they weren't bad at all as a receiver. I used to (gasp!) sell those. I forget which company made them for Radio Shack. Yes, I sold them with the Mach 1's. No comment.

It's probably better than the amps found in most new sets. The power rating was real in those days. Power rating now is like horsepower (yah, right, you got 300 HP?). So don't get discouraged and don't throw it out. I think it would surprise you with it's sound quality compared to today's stuff.

-Chris

[muskgrave]

I'm sure it would..and i'd love to get it working again but I can't afford what a shop would want to charge me to fix it...

[anatech]

I understand. You also can't afford to have it "hacked" either. Save it until you have the knowledge or the money to do it right.

I don't think there is anything else you can do yourself. Sorry.

-Chris