Pioneer SX-1980, AWR-154/155 power supply re-design
Its alive
Running for a few days now. I did some measurements, where I have determined that one can distribute the load(heat) sharing a bit better between the series V drop R's and the linear regs to reduce their op temps.
Couple of more pics of the new PS in the unit.
In the past the fuse holder must have been damaged beyond repair. This is a international unit (S/G model), with the primary voltage tap transformer option thus the selector on the back.
Some idiot decided it was okay to insert a metal slug in the fuse position to defeat the AC line fuse function. The metal slug was live and exposed, a real safety issue. I installed a fuse holder in the unit as you can see on the back panel. I also put some glue over top of the metal slug to make it safe.
Thanks guys
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restorer-john
Addicted Member
It's a gorgeous looking PCB. Beautifully done. 
Very impressive! Well done.
Watching the progress and now knowing the option of a 1980 PS board, I've grown sad wondering if I'll see another 1980. Heck, I had three at one time in the shop. Hadn't seen any since the last one left more than a year ago. I want another one so I can tryout the new board.
Watching the progress and now knowing the option of a 1980 PS board, I've grown sad wondering if I'll see another 1980. Heck, I had three at one time in the shop. Hadn't seen any since the last one left more than a year ago. I want another one so I can tryout the new board.
kevzep
Its all about the Music
Exactly, I know what you mean!!
A member PM'ed me asking if they should use a new PS in a 1980 that was in rough shape, I responded
It is hard for me to say if you require this new pcb or not. It has to be determined if the existing PS is working correctly to start with. Usually a new pcb is required if the existing pcb is badly damaged, sometimes beyond repair or you specifically want to do the upgrade for improved reliability. Putting in a new PS still may not make the unit operational or could even damage a new PS. I can not tell if you are in that situation unless further diagnosis/testing is performed.
There are threads discussing testing and modifications to the exiting PS pcb that improves its operation, such as the EW LED constant current mod and moving some of the hot regulating transistor(bjt) to the power amp heatsinks, upgrading of parts etc. These evaluations have to be done first. I can suggest that you start a thread and the AK members can help you in determining the op status of your unit. We need to know what works and what does not. The DBT is fine for determining hard faults such as shorts but once you have the unit running off the DBT, then the unit has to be tested to determine what is or is not working.
It is hard for me to say if you require this new pcb or not. It has to be determined if the existing PS is working correctly to start with. Usually a new pcb is required if the existing pcb is badly damaged, sometimes beyond repair or you specifically want to do the upgrade for improved reliability. Putting in a new PS still may not make the unit operational or could even damage a new PS. I can not tell if you are in that situation unless further diagnosis/testing is performed.
There are threads discussing testing and modifications to the exiting PS pcb that improves its operation, such as the EW LED constant current mod and moving some of the hot regulating transistor(bjt) to the power amp heatsinks, upgrading of parts etc. These evaluations have to be done first. I can suggest that you start a thread and the AK members can help you in determining the op status of your unit. We need to know what works and what does not. The DBT is fine for determining hard faults such as shorts but once you have the unit running off the DBT, then the unit has to be tested to determine what is or is not working.
In all, throwing out the old and installing the new, is a major task. Skills are needed to dissemble the original components with success, then reassembling using learned electronic interpretation. At first it looks like an easy endeavor. There are lots of "Kit's" similar to the STK module out there for the DIY. They all need some underlying knowledge. A vintage audio owner needs guidance. If there's a least bit of questioning, a experienced tech should be consulted. Replacing the power supply, (If that's truly the issue), has the potential to cause more trouble with the rest of the set over another circuit.
The members here have the ability to complete these kits. Maybe not all the electronic skills but a background that gives a sense of confidence, or they wouldn't be involved in this forum. Still; new power supply options and even repairing the original PS on the SX-1980, will require some needed guidance to complete the repair successfully.
If the receiver is operating without issues and an owner now has anxiety over what was read regarding the failures and repairs, this forum is where that discussion should be heard.
The members here have the ability to complete these kits. Maybe not all the electronic skills but a background that gives a sense of confidence, or they wouldn't be involved in this forum. Still; new power supply options and even repairing the original PS on the SX-1980, will require some needed guidance to complete the repair successfully.
If the receiver is operating without issues and an owner now has anxiety over what was read regarding the failures and repairs, this forum is where that discussion should be heard.
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Sure a fan can be installed, it is a mechanical challenge, I have seen one pic of someone doing so, what does the fan use for a supply, AC or unregulated DC?
I have even suggested to drill an bunch of holes in the back panel to let the heat out and allow for more air to circulate. If it was my 1980 that is what I'd do to start with, to cool the Japanese cooker.
I have even suggested to drill an bunch of holes in the back panel to let the heat out and allow for more air to circulate. If it was my 1980 that is what I'd do to start with, to cool the Japanese cooker.
BobbyN
Well-Known Member
Many fan options. Maybe right off the power switch with a rectifier, dropping resistor, and fuse. Some small fans have extremely low current draw. I think a small rectifier circuit could be built on a 1" x 1" board. Also some of these small fans are extremely quiet.
Not sure if I would choose this fan or not...
https://www.adafruit.com/product/3368?gclid=EAIaIQobChMIk9vB-KeJ3wIVSZR-Ch1yyQSoEAQYASABEgLrFPD_BwE
...but that's an example.
Bob
Sorry...I did not check it, but if you click on "Watch this video on YouTube." on the screen that does come up it will redirect you to YouTube to watch it
Just watched the video. He makes a couple of points that should be placed in the instructions.
1.) When bench testing, run a jumper from pin 21 to Pin 10 (Grounds). Otherwise votlages on the 80v and -80v are all over, and the CCS LED's flicker out of phase with each other(no ground reference.). Once ground established @ pin 10, everything copasthetic.
2.) When finished with installing, you will have pins 1 & 2 (old board) left over. No pin 1 & 2 on new board as the voltage pick off's are internal to the board now. You can either heatshrink the ends and mark them for later use if you decide to Re-install the original board or remove them completely.
The board looks fantastic, Rick. Great job on R & D.
1.) When bench testing, run a jumper from pin 21 to Pin 10 (Grounds). Otherwise votlages on the 80v and -80v are all over, and the CCS LED's flicker out of phase with each other(no ground reference.). Once ground established @ pin 10, everything copasthetic.
2.) When finished with installing, you will have pins 1 & 2 (old board) left over. No pin 1 & 2 on new board as the voltage pick off's are internal to the board now. You can either heatshrink the ends and mark them for later use if you decide to Re-install the original board or remove them completely.
The board looks fantastic, Rick. Great job on R & D.
sendust
Music feeds the soul
I also watched the video and it just happens it was my SX 1980 that Rick repaired, i am blown away with the skill it would take to redesign the power supply and happy to say my unit works amazing. thanks again Rick and if anyone was still on the fence with purchasing this power supply, i can tell you my unit runs cooler than any other Pioneer i own. pete
Awesomeaudio
Super Member
I just finished watching the video and I am very impressed.
Rick, you are an amazing Engineer.
Your board is all Class !
Well done.
Rick, you are an amazing Engineer.
Your board is all Class !
Well done.
