20 Most Recent Pyramid - PS21KX 20 Amp Power Supply Car Audio Amplifier Questions & Answers

Most of Pyramid's supplies are based on the LM723 voltage regulator. The DATASHEET should tell you most of what you'll need to know to repair it. THIS is the schematic diagram.

If the output voltage drives the voltmeter to the end of the scale, it likely has one or more shorted power transistors.

You're getting 240 volts from a pyramid amp? Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx

Yes. Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx

Say that three times real fast. Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx

Yes. Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx

Cool. Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx

That is exactly what the protection light is for. Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx

I'm not sure what you mean by 'wide open voltage'. If it's over 17v, the supply may have multiple problems. I don't have the 52kx schematic but other Pyramid supplies have over-voltage protection. There is an SCR that is triggered when the voltage gets to ~17v. This should clamp the output and trigger a shutdown. You should check the 16v Zener diode and the SCR. If the SCR or the Zener is defective, that would prevent the over-voltage from clamping the voltage. Also confirm that the SCR has a solid connection to the ground terminal of the supply. If it's open, that could prevent the clamp from shutting down the supply.

If the voltage is going high, measure the DC voltage from pin 4 to pin 5 of the LM723. It should remain the same at all times. Also measure the voltage from pin 5 to the ground terminal of the supply. That should also remain constant at all times.

The problem I have had with a PS-20 is a blown capacitor. Hooked to a radio, would allow radio to receive fine, but when trying to transmit, amperage would bottom out. Behind the transformer is a large circuit board. UNPLUG POWER SUPPLY, remove cover, Undo the two nuts, flip board over, and gently rock the 4700uf capacitors side to side. If they move more than 1/16th of an inch, chances are they are blown. Remove/replace and should be good to go...

Make sure is grounded properly and check the wires, the positive is connected to + and negative to -
I hope this helps.

Bad amp.

Bad amp. Trash. Sorry sugar :(

protection light come on and bets

The out put transistor are cooked and will need to be repair.

thank you for your help . I have already fixed the power supply I double checked the transisters and found three bad so I replaced all the power transisters and it is fine . thanks again bob

Generally, the fuse only blows when the rectifiers fail. In other Pyramid supplies, they use a square, 4 terminal bridge rectifier. They probably use the same thing in your supply.

Let me know if you have any other questions.

I have used this tech for repairing some of my radio equipment and found him to be honest and dependable A rare thing now days. check with him at [email protected]. Unless you are wanting to take a shot at repairing it yourself if so I will do some searching myself to see if I can give you a hand on it.

Have you done any troubleshooting at this point?

Are you going to try to repair this yourself?

Have you tried to locate a schematic for the supply?

709EX https://www.google.com/search?q=PYRAMID+SE709-VL-LED+manual ..

"wirering"? Recommend contacting a local car audio professional or Pyramid customer support directly here: http://www.pyramidcaraudio.com/ContactUs.aspx