Phoenix Gold Phorum

ok, i have a PG zx250 2ch given to me a while ago, goes into ovrload/protection mode without RCA/Speaker hooked up other than power, when power is supplied i see a voltage drop on my power supply as the amp is trying to turn on, then the flashing lights Green/Red.
ive checked for any blown part, cant see one track or burnt out part at all, obviously something not visable/internal short
i've done some pg phorum reading about psc riser cards, output transistors, thermistors and so on..

im just gonna spend my money $$$ on replacing most parts at once and hope for the best.....
I've pulled amp apart ready to replace parts

I need help locating in Australia/eBay U.S. = 2 x IC's on PSC riser card KA339, KA3525a
2 x D1975 transistors (Does this have to be a darlington?) - Equiv/Replacement
2 x B1317 transistors (Does this have to be a darlington?) - Equiv/Replacement

Is this the switch mode Transistors 1 x SP163,1 x SP163A and what are a complementry/equivelant?

4 x NDP7060 - Equiv/Replacement ?!
2 x D1763A - " " "
2 x B1186A - " " "
2 x C1567R - " " "
If anyone could help me of where to purchase this online, would be much appreciative.

Check the output transistors for shorts with a DMM first. That might be your problem.

done that, getting .6 on dmm on most of them, the only one i havnt measured is the sp163,163a cause the switch mode circuit there looked parrelled. the only funny one i saw which was still in circuit while measuring c1567r, showed me .3 on one pin and .7 on the other

i dont no if this will help or not but i have a zx350 that a friend of mine gave to me it has the same problem and what he did to get it to work again was he took a piece of wire and ran it from the ground terminal to the mounting screws. i have no idea why it does this but it seems to be the same problem kind of weird if its not the same problem anyone got any ideas on why mine is like that lol?

Ok, just before i replace every single transistor component (Power Supply/Outputs etc) on the zx250, ive disconnected the X-OVER (Crossover Board) away totally from the amp with the Input and Output RCA's and lots of 8pin IC's.
i did a DMM check and there is a short on the Input RCA's which is probably causing my Overload Shutdown to come on.

So first thing i did was unsoldered the black plastic Input RCA Connector plug away from the x-over board.
i ran another check with my DMM and still shows a short between the outside ground and input pin on one channel.

No suspect parts i can see are blown, burnt up.
Will post pics in the next following few days if anyone can help on this subject.

Are you reading a direct short in both channels, or just one? You may have a shorted cap right after the input. If memory serves, there is a mylar cap from signal to ground on both channels. I have to say, that it is highly unlikely that anything in the preamp section is tripping the OL. If it is similar to the later Ti amps, then the OL circuit is basically based on voltage drop across an output transistor's emitter resistor. Pretty much everything in the preamp section is going to be on the +/- 15V supply, and if they used 3 terminal voltage regulators, then the regulators themselves handle the OC shutdown for that portion of the supply.

You really need to find the problems, and not just throw parts at it. For starters, you say the amp causes a voltage drop on your supply when it tries to power on. Some in rush current is normal, as the rail capacitance has to charge. You need to measure the actual current draw of the amp-- saying the supply has a voltage drop is virtually meaningless. If it has sustained high current draw, then see if it will idle with the main rectifiers for the PS removed. This effectively breaks the link between the rails and the power amp. If it powers up and idles fine, then your problem is in the power amp. If it still shuts down, it might be an issue with the protection circuit itself.

I can't recall if the ZX amps had under voltage protection or not, but if so, that may also be responsible for your OL light and the power cycling. If your supply simply can't supply the inrush current needed, it may never power up on it. I had a Ti amp I was working on that was missing most of it's PS input capacitors, and it would not power up until I got a reasonable amount of capacitance on board. That one would power on and off repeatedly though, and it sound like your OL condition is staying latched, so that is probably not the answer. The point is that you need to know-- if you are using a computer power supply good for 5amps trying to test the amp, then it might be your test rig, not the amp.

I agree with Eric though, it is likely going to be one of the outputs. If you you don't have a lot of experience and you checked them in circuit, you may have missed something. It is best to pull them to test them. If they are really good, move backwards through the amplifier. It is possible that a driver or pre-driver transistor may have failed and is causing the output to conduct when power is turned on. Another thought is maybe the bias transistor has failed and is significantly overbiasing the outputs.

That said, at least a few of your part numbers that you asked for:
KA3525a = LM3525an, SG3525an (just search for SG3525 and you will find what you want. Don't buy semiconductors on Ebay!)
KA339 = LM339

The transistor part numbers you list likely start with the prefix 2S, and that is why you are not finding them. As far as I can tell, some of the transistors in PG amps, especially driver and pre-driver parts, are long obsolete, and in at least one case I can think of, were virtually unavailable to the public from the very beginning.

Good Luck,
Jason

ok these are the parts which i intend on replacing and wouldnt have a clue what manufacture / who made it and what i need to replace them with.