Schematic for Pyle PTA 1000

[DrGonz78]

This thing sure is a pyle!! Anyone out there have the schematic so I pyle drive it a bit more!!??!! lol

[Jazz P Bass]

That you will not find.
You could try contacting Pyle direct.
I waited a week for an answer on the internal fuse value of one of there amps.
What is wrong with the amp?
Blown channel?
250 watts @8 ohms per channel.
Replace what's blown.
Keep in mind you could buy another one for $100.00.Pyle Pro PTA1000 Professional Stereo Power Amplifier PTA1000 B&H

[DrGonz78]

Hey Jazz! The problem is with channel B. Turn on amp ch.B plays fine for about two minutes then cuts out. Turn amp off then back on and signal comes back on but drops out quickly, as it has already heated up. So, I did some soldering on the preamp boards and the power amp board. After soldering those boards the ch.B will play for about 5 minutes and cuts out. Also, now turning it off and on, signal recovers for much longer too. I also replaced a bad cap on the power board(leaking out electrolyte & tested bad). So it is improving a tad. All the transistors test good on the meter and I am leaning towards a bad solder joint on channel B's output board. Got to get more solder and will re-flow the board tomorrow. The solder on these amps is just nasty stuff!!

Channel A is working so I am slowly analyzing the working channel in contrast to the intermittent channel B. This amp is from a friend of mine and I look at this as just a learning experience. He knows I might be able to fix it, but would love to fix another amp for this friend of mine. Always feels good huh?

[Jazz P Bass]

It appears, as of yet, you have not found out where it is failing.
I would start by identifying what topology the output section is.
Common collector or common emitter?
Is there rail switching being used? (look for multiple power rail values. ie: + - 35Vdc & 70Vdc)
Does the whole amp shut off or is it the signal that drops out?
Does it act up without a load?
At what power level & load are you testing the amp?
You are assuming that heat has something to do with it.
Prove what is wrong.
Power supply. Power amp. Preamp, .
The power supply is easy enough to monitor.
Lucky for you () the symptom happens fairly rapidly.
Check the main + & - rails & the opamp supplies for a change when the amp malfunctions.
If it is not the power supplies, then it may be a signal problem.
If you get on any of the output transistor bases, you can see if the signal is dropping out, power amp wise.
If it is a preamp problem your on your own without a schematic.

[Enzo]

What kind of bill is this friend expecting to get? If it is going to top $100, that amp Jazz found looks real attractive. Just hand it to buddy and tell him his amp had a defective serial number, we had to change it.

[Jazz P Bass]

Defective Serial Number.
I like that.

[Enzo]

Feel free to use it then...



Not sure where we got that, seems to me a couple times we'd send some product to the OEM because we couldn't find the problem. It would come back "fixed" but with a different serial number, so we knew they just swapped us out. Someone quipped "Aha! Defective serial number." And it became a part of us. I must admit, that someone was not me, much as I'd like to take credit.

[DrGonz78]

Yup Jazz I have not located the fault yet and I have some good research to go... The amp powers on and does not blow fuses. Nor does the amp go into protection mode. When the amp fails it is simply the signal that fails and Ch A keeps on working, the amp does not power off. I will start to investigate more on this amp as I go. My friend is giving me "as long as I want" to work on it, no rush. Indeed the serial number might be defective but still I am gonna figure out a way around that!! I am doing this as a labor of love to learn how to fix something and not about the money. Sure he will pay for parts and give me a little something, but yeah we won't be putting any real monetary value back in this thing! lol

I will figure out more to your questions Jazz, as you are pointing me in the right direction. There are no op amps on this thing either. It is filled with what I think are FET's or is that an op amp? Basically there is a chip on the input board(I will give more info later) that I believe is some sort of buffer for the input it is a long chip... Maybe a TL074?? I forget now... Like I said>>> I will follow up on this later and start taking some voltages and scope it too. Thanks you guys... Will be back soon!

[Jazz P Bass]

The TL074 is probably used as a buffer & a driver for the output stage.
As I said, get on a base leg of any of the output transistors & see if the signal drops out.
If it does, then move back to the IC.
Divide to conquer.
There very well may be separate power supplies for cnA & chB, so don't rule out the power supply.
Test it.

[DrGonz78]

I would start by identifying what topology the output section is.
Common collector or common emitter?

This appears to be a common collector.

Is there rail switching being used? (look for multiple power rail values. ie: + - 35Vdc & 70Vdc)

No there is no switching being used here going to the output board. I guess there is the 15vDC rails going to the preamp chip, but there are no other voltages going into the output board besides the -/+49vDC.

Does it act up without a load?
At what power level & load are you testing the amp?

I will test this with out a load tomorrow to check that too. I am testing under full mains power with an 8 ohm load.

Check the main + & - rails & the opamp supplies for a change when the amp malfunctions.
If it is not the power supplies, then it may be a signal problem.

The main rails sit at -/+ 49vDC and do not fail at any time. The TL074CN (14 legged critter) does not drop voltage at any time before or after failure, -/+ 14.95vDC. Is there anything here on the opamp that I should test further?

If you get on any of the output transistor bases, you can see if the signal is dropping out, power amp wise.
If it is a preamp problem your on your own without a schematic.

I tested with the meter on AC setting to look at the signal. I am measuring variable 150-450mv fluctuating upon signal/amplitude, talk radio and rock music from my stereo. A four wire plug connects from the power board to the output board. It runs two wires -/+ 49vDC supplies, one wire ground, and last wire is the signal. Signal never drops out here. I tested the signal on the Base of one of the transistors on the output board and it still shows consistent AC signal even after volume cuts out on the speaker. Should I also be testing the vDC on any legs of the output transistors too?

So I am really starting to wonder where to look next... I will try looking at the working side of the amp to analyze and compare the meter readings tomorrow. Looks like a needle in the haystack so far...

[Jazz P Bass]

It's not a needle in a haystack.
You have successfully narrowed the problem to the output section.
It struck me as odd that the signal at the output transistor is not failing.
Are you getting a signal on the emitters?
Is there an output relay on this amp?

[DrGonz78]

Well I tested both transistors on their bases and emitters. It's the same story either way, AC signal is coming through the transistors. Neither Emitter or Base drop out the signal and the transistors are Toshiba A1941 and Toshiba C5198. I see about 4.7vdc on the bases and they don't drop out when speaker stops outputting the signal.

I did notice the relay on the power board and when you turn on the amp I hear it click to engage. My original thought was that it must have something to do with the protection circuit on the amplifier and it still may. However, looking at the picture I have attached you will notice that the signal outputs for ChA & ChB are right next to this device. Maybe that is where the problem lies? Any ideas? Thanks again for sticking with me on this one!!

[Jazz P Bass]

Keep going.
The relay board soldering has been gone over?
You know that the relay circuit (and the relay coil) functions, because Ch A does not fail.
The Ch A & Ch B speaker signals come in where?
The Yellow/ Black connectors?
I would verify that the signal is reaching the connector.
If you have signal before the relay & no signal after the relay, then the relay or it's connection is no good.
JZC-7F pdf, JZC-7F description, JZC-7F datasheets, JZC-7F view ::: ALLDATASHEET :::
Ch A & Ch B have there own separate contacts in the relay.
So, internally, the Ch B contacts may be bad.

[DrGonz78]

Well Jazz thank you very much for all your help. I had a gut feeling that the solder on the power board really needed to be removed and fresh solder applied. In fact back when I re-flowed the power board originally is when the amp started working for 10 mins opposed to 2 mins. With that in mind I went at the power board with my soldering iron. Concentrating of course on the the connections for the relay. I even took the relay off the board and got down to the pads. Cleaned off the legs of the relay too for good measure. I needed to rule out any bad solder joints on the power board, even if I re-flowed it before.

So the amp is playing after 30 mins. of testing and I am pretty sure this was the trouble all along. I am really glad though that I did not fix it when I re-flowed the power board the first time. I am much happier to know the *exact* cause of the failure. It was a bit more work than maybe this amp is worth but it was a great learning lesson. Thanks again!!

[DrGonz78]

Just for more clarity on the power board and this amp, I am attaching this pic. I have noted as much as I can about the connections on this board, just in case this comes in handy for anyone else. I have a pretty good idea that the input board also sends the signal to the output boards and the two 4-pin molex connections (Red & Black on the power board) return signal after it is amplified. Those 4-pin connectors carry<<< signal-ground-(+49vDC)-(-49vDC). The (To speakers) ChA&B connection 3-pin Red-Black-Blue molex cable is where the signal is carried to the output jacks.

I am pretty sure that the TL074 chip buffers the input and sends it to the volume connection board. Signal is then returned to the TL074 (input board) where it is sent to each output board for amplification. The 4-pin connectors (Red & Black) carry power to the output board and receive the amplified signal back into the the power board. Signal then passes through the relay onward to the 3-pin Red-Black-Blue molex cable which sends it to the speaker outs.

I am not 100% on this analysis on this amp, but it is my best understanding. It would be nice to have a schematic to check this out, but that will probably not happen easily. Either way my assumptions here cannot be that far off either. Hope this helps someone out there, since there is very little info out there in regards to this power amp.

P.S. Just to note I might have the signal flow incorrect too. It might actually be sent from the 4-pin connectors on the power board to the output boards then carried to the input board. Then signal goes through the the TL074 for output stage to the volume control board again. On the pic where is says "Voltages for LED's etc" might be actually where the signal ends up before hitting the relay and final output to speakers. I would fully trace this out on the boards but I spent too much time on it already. Anybody who might want to clarify signal path better then please feel free to post.