Pioneer SX 828 Power supply help and ideas needed!

[pa_200]

Hello friends of the good old Pioneer receivers,

I’m writing you from Germany and hope for some help and ideas for my rebuild of my first SX-828.

Actually I have cleaned the interior and want to start with the work on the power supply board, followed by the protection and the head amp unit.

As a first thing I measured the voltage on all pins of the Power supply unit AWR-010 and was wondering which AC-voltage will come out of the Transformer ATT-059.

The Voltage from the wallsocket is 238V here in Germany, the selector on the SX-828 is set to 240V.

I got the following AC-Values.
PIN 8 = 29 VAC,
PIN 9 = 35 VAC
PIN 10 = 30 VAC
PIN 12 and 13 = 24 VAC
PIN 18 = 28.8 VAC
Are these OK??

On the DC site, I had some strange values.

PIN 2 = 12 VDC, that seems OK
PIN 4 = 4.4
PIN 5 = 31.7
PIN 6 = 29.9
PIN 7 = 31.7

PIN 9 = 35V should be 49V
PIN 14 = 30.4 V should be 44V
PIN 15 = -30.4 V should be -44V
PIN 17 = -29.9 V should be -45V


I will change all caps, the 3 transistors with new ones and change the R12 (330 Ohm 2W) with a 330 Ohm 3W to reduce the heat in that area.


BUT what can be the cause for the low voltages on the pins 9 – 14 – 15 and 17?

Any idea where else I should look at to get the correct voltage on that pins?

 

[grindfix]

I could be wrong but I think European voltage is 220v nominal, and can vary depending on area and time of the day +/- up-to 10%. 238v is within its upper limit. Does your SX-828 have a 220v setting? If you have a variac (variable autotransformer), you could set receiver to 220v jumper position and power it up through variac while watching your DC measurements until you get in 220v range and see where you are.

 

[pa_200]

The 220 V with 10% tolerance was the original value until 1987, but with European power grid and England with 240v the voltage was raised to 230 v ±10 %. On new gear you will always find a label with 220/240V.
I had the SX 828 set to 220V bat the DC was still way out.

 

[Skywatcher]

Hello friends of the good old Pioneer receivers,

I’m writing you from Germany and hope for some help and ideas for my rebuild of my first SX-828.

Actually I have cleaned the interior and want to start with the work on the power supply board, followed by the protection and the head amp unit.

As a first thing I measured the voltage on all pins of the Power supply unit AWR-010 and was wondering which AC-voltage will come out of the Transformer ATT-059.

The Voltage from the wallsocket is 238V here in Germany, the selector on the SX-828 is set to 240V.

I got the following AC-Values.
PIN 8 = 29 VAC,
PIN 9 = 35 VAC
PIN 10 = 30 VAC
PIN 12 and 13 = 24 VAC
PIN 18 = 28.8 VAC
Are these OK??

On the DC site, I had some strange values.

PIN 2 = 12 VDC, that seems OK
PIN 4 = 4.4
PIN 5 = 31.7
PIN 6 = 29.9
PIN 7 = 31.7

PIN 9 = 35V should be 49V
PIN 14 = 30.4 V should be 44V
PIN 15 = -30.4 V should be -44V
PIN 17 = -29.9 V should be -45V


I will change all caps, the 3 transistors with new ones and change the R12 (330 Ohm 2W) with a 330 Ohm 3W to reduce the heat in that area.


BUT what can be the cause for the low voltages on the pins 9 – 14 – 15 and 17?

Any idea where else I should look at to get the correct voltage on that pins?

Make sure you are looking at the correct service manual (or section of) for that particular model. Make sure the model number *and* the suffix matches. There are some variations and there will be notations for them.

 

[pa_200]

Skywatcher your reminder is absolutely right, I have the AWR-010A as you can see in the picture. If there are other sm or parts of it is available, where can I find it? My sm is a download from here

http://www.kallhovde.com/pioneer/Pioneer/Main scan page.html

 

[merlynski]

 

[merlynski]

You listed Pin 9 twice, once in AC list, once in DC list. That pin goes only to a filter cap (C8, 1000µF, 63V) and should not have 35Vac on it unless the cap is bad or the wire is broken (hard to tell in the picture, but maybe, red with white stripe). That DC supply source feeds all the regulated DC supplies, so if it has big AC ripple on it all the regulated supplies will be out of line. Also check the voltage of D7, the 13V zener diode reference for all the regulated supplies.

 

[grindfix]

It looks like one of the transistors is attached to heatsink with metal screw. Unless proper mounting kit was used, heatsink has voltage potential on it. It's least likely to have anything to do with your situation but is worth checking to make sure heatsink is not touching anything.

Were your DC voltages higher when receiver was switched to 220v jumper?

 

[Skywatcher]

Skywatcher your reminder is absolutely right, I have the AWR-010A as you can see in the picture. If there are other sm or parts of it is available, where can I find it? My sm is a download from here

http://www.kallhovde.com/pioneer/Pioneer/Main scan page.html

View attachment 1457653

It's more about the model/revision of the receiver itself and not so much about the individual boards except in the case of a certain revision model *may* use the same board but with differing components and/or (possible) voltages. Yours is either the FVZW (Germany) or FW (General Export) revision(s) since they have voltage selectors. The U.S. model KUW is only 120v. There should be a round label on the rear of the receiver. The original SM/schematics won't have any in-production revisions so there *may* have been some changes to your particular model. The serial number will tell you the date it was made. Perhaps somebody has some (if any) service bulletins that may have been published for your particular unit. I don't know how similar an 838 is to the 828, but this 838 I have here has a selection for 240v in addition to a 220v selection. The only 828 SM I have at this time is a pretty poor scan and it is hard to read some things.

As to your question, I really don't know if another SM is available. That source seems to have a lot of Pioneer information.

 

[Watthour]

Hopefully, this is clearer:

 

[Skywatcher]

Hopefully, this is clearer:

That's much better, Thank You! I didn't notice any "special notations" for the different revisions here so it appears all board level voltages/values should be the same. Any "exception" would be any possible later in-production component or board revisions not shown here.

 

[Watthour]

That diagram is for a multi-voltage unit, and employs the AWR-010 supply. Further, although the diagrams rarely show the sub-revision levels of boards such as the AWR-010, you apparently have the "A" revision which is likely represented on the schematic.

 

[Skywatcher]

That diagram is for a multi-voltage unit, and employs the AWR-010 supply. Further, although the diagrams rarely show the sub-revision levels of boards such as the AWR-010, you apparently have the "A" revision which is likely represented on the schematic.

I stand corrected, I did notice one notation where it was noted that "C13 is replaced by C12 in the 120v model" in the tuner section. By that I would assume it covers all 3 voltage models. I was thinking the same with the "A" PS board.

 

[Watthour]

You may have been correct in the first place. Modifications and updates were not always documented, and the original design drawings are sometimes all that were made available. The factory bulletins didn't always make it into the books. I'd refer to what was installed in the working unit unless there is compelling evidence of some previous replacement.

 

[Skywatcher]

You may have been correct in the first place. Modifications and updates were not always documented, and the original design drawings are sometimes all that were made available. The factory bulletins didn't always make it into the books. I'd refer to what was installed in the working unit unless there is compelling evidence of some previous replacement.

That is what I normally do if what is in there looks original. Solder joints can sometimes reveal if a component has been changed even if it "looks" original on the surface. But even if there were or are updates, the unit did work even with the components in the original SM/parts list. Some updates are somewhat minor, though some are more on the critical side.

 

[pa_200]

No change so far on the power supply, but I will give you the results after the new parts are installed. But still I have no clue for the low DC voltage.

Today I checked the 3 bigger caps and got these readings.

C8 1000 µf/63v was 1195µf with ESR 0,12 Ohm an VLOSS 1,1%

C6 8000 µf/50v was 9866µf with ESR 0,1 Ohm an VLOSS 1,6%
C7 8000 µf/50v was 9366µf with ESR 0,1 Ohm an VLOSS 1,9%

Question to the experts. Would you change these caps or not? If YES, which one would you recommend!

 

[merlynski]

Did you have continuity from pin 9 to the + side of C8, and from the - side of C8 to ground? 35Vdc is what your meter would read if the filter cap was not connected and charging to the peak of 49Vdc. The regulators would not have enough headroom to provide properly regulated voltages. If you have an O'scope look at pin 9.

 

[pa_200]

Merlynski I will check it tomorrow with good light and replay, it‘s 23:00 now here in Germany.

All caps are out, all 4 100µf/50v are in limit, only the 1000µf/10 is way off at 460µf and one of the 220µf is at 260µf.

 

[Watthour]

I'm not any component design expert, but considering that the filter caps you tested are going to operate at 100 or 120 Hz (bridge rectifier) and they ESR is that low for such a large cap, I would leave them alone. New replacements might not even test that well.

 

[Skywatcher]

I'm not any component design expert, but considering that the filter caps you tested are going to operate at 100 or 120 Hz (bridge rectifier) and they ESR is that low for such a large cap, I would leave them alone. New replacements might not even test that well.

For caps as old as these, there is sure to be (electrical) leakage, and have dried out. A capacitance check only tests for capacitance. And ESR meter tests for ESR *out of circuit*. Under a load and at operating voltage they behave differently. Small capacitors are inexpensive and it is well worth replacing them. I would personally replace all the ones pa_200 mentioned above with known good quality fresh caps. But that's his decision to make.