I just recently decided to attempt a rebuild on a PS Audio Premier "Power Plant regenerator" based on the some what vague service information provided by PS Audio. The rebuild includes replacing multiple surface mount components on the regulator board and the four darlington power transistors. I decided to replace all the electrolytic capacitors as well just.
I am now at the "smoke testing" stages where I disconnected the regulator and ran the unit on a 250W dimbulb. Everything appeared okay and there was not much current draw from the unit.
Now this is where my concern is since I don't want to blow up $75 worth of transistors so I kept in on the dimbulb. When I hook up power to the large rectifier on the heatsink that drives the darlington regulators the dimbulb goes to full brightness and does not dim down.
What should I do now? I have no schematic to work with so I am hoping I can find some one who has experience working on these units and since I got this for "free" all I have to lose at this point are the parts I threw into it but would prefer not to blow up the new transistors if possible.
I am now at the "smoke testing" stages where I disconnected the regulator and ran the unit on a 250W dimbulb. Everything appeared okay and there was not much current draw from the unit.
Now this is where my concern is since I don't want to blow up $75 worth of transistors so I kept in on the dimbulb. When I hook up power to the large rectifier on the heatsink that drives the darlington regulators the dimbulb goes to full brightness and does not dim down.
What should I do now? I have no schematic to work with so I am hoping I can find some one who has experience working on these units and since I got this for "free" all I have to lose at this point are the parts I threw into it but would prefer not to blow up the new transistors if possible.
Damn... you are right... one section of the bridge turns out to be a complete short and the other reads low resistance. It honestly never crossed my mind to check it until you mentioned it.
Looks like the bridge rectifier is 35 amps at 600V and I think I found a good used one so I will give that a shot!
It appears that was the last failed component! On the dimbulb the unit draws down to 114 input but says 119 output which is a good sign.
Thanks for suggesting to check the rectifier as that would have been a rather abrupt ending if I decided to throw the unit on full power.
I'll be sure to share some pictures if anyone is interested but for anyone attempting this repair having some sort of current limiting device is a very good idea as I found out lol.
Time to put it back together and find out if this thing was even worth my time to use along side any of my gear. The grid in my area is over all very stable, not all that old and same with the house wiring... the other side of town on the other hand xD
Thanks for suggesting to check the rectifier as that would have been a rather abrupt ending if I decided to throw the unit on full power.
I'll be sure to share some pictures if anyone is interested but for anyone attempting this repair having some sort of current limiting device is a very good idea as I found out lol.
Time to put it back together and find out if this thing was even worth my time to use along side any of my gear. The grid in my area is over all very stable, not all that old and same with the house wiring... the other side of town on the other hand xD
Sorry this took a while to follow up on. Here is a picture of the main board to be concerned about, this is an after picture with all the bad components replaced.
Parts mostly sourced from digikey as a reference:
Transistors:
2x MJ11033GOS-ND TRANS PNP DARL 120V 50A TO3
2x MJ11032GOS-ND TRANS NPN DARL 120V 50A TO3
2x MMBTA56LT3GOSCT-ND TRANS PNP 80V 0.5A SOT-23 (Q11, Q14)
2x MMBTA06LT3GOSCT-ND TRANS NPN 80V 0.5A SOT-23 (Q12, Q13)
Diodes/rectifiers:
2x BAV99LT1GOSCT-ND DIODE ARRAY 100V 215MA SOT23-3 (D13, D14)
1x 641-1860-ND BRIDGE RECT 1PHASE 600V 50A KBPC (if old shorted)
Resistors:
2x 311-10.0CRCT-ND RES SMD 10 OHM 1% 1/8W 0805 (R43, R44)
2x 311-47.0CRCT-ND RES SMD 47 OHM 1% 1/8W 0805 (R39, R40)
4x 0.12 Ohm 5 Watt wire wound (replace if 0.05 ohm or if open)
Opamps(optional/precautionary):
1x 497-2200-1-ND TL072CDT IC OPAMP JFET 4MHZ 8SO
Capacitors(optional):
7x P19613CT-ND CAP ALUM 47UF 20% 50V RADIAL
2x 493-12020-1-ND CAP ALUM 390UF 20% 50V RADIAL (C7, C8)
4x 565-2878-ND CAP ALUM 15000UF 20% 35V SNAP
The capacitors are an optional improvement and don't cost much extra. In my unit I have burn't traces and had to clean up the board around the SMT parts and sort of make my own, which looks ugly but it worked out okay.
Before you apply full power to the unit disconnect the large bridge rectifier from the mains transformer and run the unit as is to make sure the display lights up okay and nothing "pops" on the regulator board. If you made a mistake or still have bad parts you won't destroy the expensive Darlington transistors.
In the case that you have a dimbulb (a series light bulb of minimum 100 watts) then use that when you apply full power, like in my case if you have a major problem the bulb will just light to near full brightness and the unit will not keep power "active". The unit may start to cycle the main relay and the bulb will flash.
If all is good the unit should start up with the bulb having a low level glow and you should be able to toggle through the "modes" and see the input/output voltages. If the unit is working right it will attempt to compensate and hold the output voltage at or near 120.
If you get this far it is pretty safe to say you have been successful as I didn't have much fuss after this point! The parts cost me about 120CAD in the end which is not bad at all considering. Hopefully I have answered any questions that the service manual might have missed.
An externally hosted image should be here but it was not working when we last tested it.
Parts mostly sourced from digikey as a reference:
Transistors:
2x MJ11033GOS-ND TRANS PNP DARL 120V 50A TO3
2x MJ11032GOS-ND TRANS NPN DARL 120V 50A TO3
2x MMBTA56LT3GOSCT-ND TRANS PNP 80V 0.5A SOT-23 (Q11, Q14)
2x MMBTA06LT3GOSCT-ND TRANS NPN 80V 0.5A SOT-23 (Q12, Q13)
Diodes/rectifiers:
2x BAV99LT1GOSCT-ND DIODE ARRAY 100V 215MA SOT23-3 (D13, D14)
1x 641-1860-ND BRIDGE RECT 1PHASE 600V 50A KBPC (if old shorted)
Resistors:
2x 311-10.0CRCT-ND RES SMD 10 OHM 1% 1/8W 0805 (R43, R44)
2x 311-47.0CRCT-ND RES SMD 47 OHM 1% 1/8W 0805 (R39, R40)
4x 0.12 Ohm 5 Watt wire wound (replace if 0.05 ohm or if open)
Opamps(optional/precautionary):
1x 497-2200-1-ND TL072CDT IC OPAMP JFET 4MHZ 8SO
Capacitors(optional):
7x P19613CT-ND CAP ALUM 47UF 20% 50V RADIAL
2x 493-12020-1-ND CAP ALUM 390UF 20% 50V RADIAL (C7, C8)
4x 565-2878-ND CAP ALUM 15000UF 20% 35V SNAP
The capacitors are an optional improvement and don't cost much extra. In my unit I have burn't traces and had to clean up the board around the SMT parts and sort of make my own, which looks ugly but it worked out okay.
Before you apply full power to the unit disconnect the large bridge rectifier from the mains transformer and run the unit as is to make sure the display lights up okay and nothing "pops" on the regulator board. If you made a mistake or still have bad parts you won't destroy the expensive Darlington transistors.
In the case that you have a dimbulb (a series light bulb of minimum 100 watts) then use that when you apply full power, like in my case if you have a major problem the bulb will just light to near full brightness and the unit will not keep power "active". The unit may start to cycle the main relay and the bulb will flash.
If all is good the unit should start up with the bulb having a low level glow and you should be able to toggle through the "modes" and see the input/output voltages. If the unit is working right it will attempt to compensate and hold the output voltage at or near 120.
If you get this far it is pretty safe to say you have been successful as I didn't have much fuss after this point! The parts cost me about 120CAD in the end which is not bad at all considering. Hopefully I have answered any questions that the service manual might have missed.
buzzb87 said:
Sorry about the wait, I don't check back here often. I believe that what I have listed is correct to assume, at least with the unit I have since those caps were used mainly for post filtering of low voltage regulators. As stated they are optional to replace and likely will not impede performance if left alone. I would leave the small one on the bottom of the board alone if it is too much trouble to replace.
The 12,000MFD ones are good to replace though if your unit has had lots of runtime hours. But once again there probably won't be any significant performance change unless these are on their way out (measure poorly). I replaced all the caps in mine as a precautionary measure in case I decide to sell my unit in the future.
My unit has held up fine so far although I have not had it in the set up for many months because some stuff got moved around (renovations). How ever one day I thought I killed it again as it would not come on. I found out that the tube amp I was using it with did not get along as it has a very high inrush current on turn on of the HV. The PS Audio unit did not like this and would go into a protect mode once in a while. So this particular unit I would advise caution when using high current equipment like tube 50watt/ch+ tube amps or larger receivers/amplifiers that draw in excess of 600 watts especially if you have other equipment hooked up to it. I have a suspicion this is a likely cause of failure to the regulation circuit when they get near to its load capacity (inrush current wise).
Regards
CrazzyAbtTubes, thanks for the reply and again for the information. I ended up replacing all of the the tech. manual items and the items you recommended, and was still having the same relay switching issue, always staying in protection mode. I ended up doing some troubleshooting, and was able to determine that the DAC filter IC (U1) had gone bad, and replaced that, and now it's working great! I think you are correct in that it doesn't like too much of a load on it, and that may have contributed to the demise of mine as well. I'm going to try running less than 500W through it, and see how it does. Thanks again!
What a great information! Thanks a lot @CrazyAbtTuubes ! I am currently working on PPP since PS Audio only offers a trade program instead of repairing this unit. The problem I am facing right now is:
1) the output voltage is always 5v higher than the input voltage.
2) The output THD is only 0.2% lower than the input THD. My input THD is around 2.1% and the output is around 1.9%. I contacted a PS Audio person and he said my unit is not working properly.
My question for you is:
1) How did you remove all the cables from the Regulator PCB? Some connectors are glued to prevent them from disconnecting accidentally but they are very stubborn to disconnect. The other cables which come from a torodial transformer are also not easy to remove from the PCB.
2) In the previous post, it is said, "Before you apply full power to the unit disconnect the large bridge rectifier from the mains transformer and run the unit as is to make sure the display lights up okay and nothing "pops" on the regulator board." Could you tell me what /where the large bridge rectifier is?
Any help would be greatly appreciated!
Thank you in advance.
1) the output voltage is always 5v higher than the input voltage.
2) The output THD is only 0.2% lower than the input THD. My input THD is around 2.1% and the output is around 1.9%. I contacted a PS Audio person and he said my unit is not working properly.
My question for you is:
1) How did you remove all the cables from the Regulator PCB? Some connectors are glued to prevent them from disconnecting accidentally but they are very stubborn to disconnect. The other cables which come from a torodial transformer are also not easy to remove from the PCB.
2) In the previous post, it is said, "Before you apply full power to the unit disconnect the large bridge rectifier from the mains transformer and run the unit as is to make sure the display lights up okay and nothing "pops" on the regulator board." Could you tell me what /where the large bridge rectifier is?
Any help would be greatly appreciated!
Thank you in advance.