My Broke SX-1980 isn’t as scary as I first thought.

I checked the outputs and Amp boards visually and did a quick check on the Drivers and transistors. Every thing checked good on both Amplifier boards and heatsinks.

Checking all the fuses; all checked good.

No blow-outs on any boards.

Pluged it in, Had the High Res print of the Power Supply schematic in front of me. DMM set to DC volts. Grounded to chassis. Flipped the power switch on. And:

Pins: (Should be)
13 = zero volts (13.5v)
14 = zero volts (13.5v)
16 = zero volts (8v)
15 = zero volts (5v)

17 = -3.4 (80v)
9 = -8.5 (34v)
12 = -8.5 (30v)

8 = -30 (-30v)
9 = -35.2 (-34v)
12 = -0 (-80v)

The set is original except for some work on the Power Supply board. New paste, looks like older parts and original caps are still installed.

Happy troubleshooting
Good luck!!

The set is original except for some work on the Power Supply board. New paste, looks like older parts and original caps are still installed.

Click to expand...

Looks like its time.... For a PS total rebuild.

Man , I sold these in the 80s .....wanna sell it ? Mine got jacked by movers when i came home from Germany ..

Roverich said:

Man , I sold these in the 80s .....wanna sell it ? Mine got jacked by movers when i came home from Germany ..

Click to expand...

About how long did you sell them? 1980 was the last year Pioneer made the SX-1980.

Just plain rebuild the power supply. Period.

Plenty of parts lists floating around.

This is the list I plan to use:
Mattsd's 4-30-2012 post

Power Supply Board (AWR-154)

AWR-154: C203: 3300uF 35v CEB: 647-TVX1H332MDD 3300uF 50v
AWR-154: C204: 220uF 160v CEB: 647-TVX2C221MDD 220uF 160v
AWR-154: C205: 220uF 160v CEB: 647-TVX2C221MDD 220uF 160v
AWR-154: C210: 100uF 10v CEA: 647-UPW1E101MED 100uF 25v
AWR-154: C211: 100uF 16v CEA: 647-UPW1E101MED 100uF 25v
AWR-154: C212: 100uF 10v CEA: 647-UPW1E101MED 100uF 25v
AWR-154: C213: 100uF 6.3v CEA: 647-UPW1E101MED 100uF 25v
AWR-154: C216: 100uF 50v CEA: 647-UPW1J101MPD 100uF 63v
AWR-154: C217: 100uF 50v CEA: 647-UPW1J101MPD 100uF 63v
AWR-154: C218: 10uF 50v CEA: 647-UPW1J100MDD 10uF 63v
AWR-154: C219: 10uF 50v CEA: 647-UPW1J100MDD 10uF 63v
AWR-154: C220: 100uF 100v CEA: 647-UPW2A101MHD 100uF 100v
AWR-154: C221: 100uF 100v CEA: 647-UPW2A101MHD 100uF 100v
AWR-154: C222: 100uF 50v CEA: 647-UPW1J101MPD 100uF 63v
AWR-154: C223: 100uF 50v CEA: 647-UPW1J101MPD 100uF 63v
AWR-154: C224: 100uF 50v CEA: 647-UPW1J101MPD 100uF 63v
AWR-154: C225: 100uF 50v CEA: 647-UPW1J101MPD 100uF 63v
AWR-154: C301: 100uF 16v CEA: 647-UPW1E101MED 100uF 25v
AWR-154: C302: 100uF 16v CEA: 647-UPW1E101MED 100uF 25v
AWR-154: C303: 47uF 16v CEA: 647-UPW1E470MDD 47uF 25v
AWR-154: C305: 10uF 16v CEA: 647-UPW1E100MDD 10uF 25v

Q201: 2SC945: 512-KSC2383YTA
Q202: 2SC945: 512-KSC2383YTA
Q203: 2SD712: 863-MJE15032G
Q204: 2SC945: 512-KSC2383YTA
Q205: 2SD325: 863-MJE15032G
Q208: 2SC945: 512-KSC2383YTA
Q209: 2SA628: 512-KSA1013YBU
Q210: 2SD712: 863-MJE15032G
Q211: 2SB682: 863-MJE15033G
Q212: 2SC1318: 512-KSC2690AYS
Q213: 2SA720: 512-KSA1013YBU
Q214: 2SC869: 512-KSC2383YTA
Q215: 2SA628: 512-KSA1013YBU
Q216: 2SD325: 863-MJE15032G
Q217: 2SB536: 863-MJE15033G
Q301: 2SA872: 512-KSA992FBU
Q302: 2SC1438: 512-KSC2690AYS

D212: EQA01-35R 35V 1/2W zener: 512-1N5248B and 512-1N5247B in series
D213: EQA01-35R 35V 1/2W zener: 512-1N5248B and 512-1N5247B in series

S1: Relay (Soft Start) ASR-046: 653-LY1-0-DC24 (Achtung! Using this relay requires you to remove R102 and run a jumper wire from the + terminal of the 3300uF 35v axial cap over to the pad of R102 that connects to pin 2. Be very careful, if you put it to the wrong side of the R102, you will short the 24v supply to the 100v supply. Not good. To be extra safe, you can just remove R102 and connect the jumper wire straight to pin 2)

S2: Relay (Protection) ASR-048: 653-MY2-02-DC48

+80v and -80v regulator mod, this replaces the 2SK34 and several other parts. Refer to this post here for instructions on how to assemble it and here on how to put it in.

I am getting ready to assemble the “Echowars current source mods” while I wait for the caps and transistors from Mouser. I plan to assemble them to MTF’s instructions and I have been pouring over the posts regarding this mod. I think I understand it and how it’s is intergraded on to the board. The pictures MTF has posted on Mattsd’s thread show two positive and two negative leads from the Current source boards.

http://www.audiokarma.org/forums/showthread.php?t=440844&page=5

Is this for support and current flow? So I can connect them to any coinciding PCB holes labeled yellow or green?

I remember reading about testing the source’s with a 9 volt battery before installing them.

All the diodes and transistors are in house to restore the PS and I want to plow ahead and get this monster up and running. But I will show some self-control and wait for the caps to show up.

The Mouser order is still in work.

Sure you can and should test the constant current source separately. All you need is a supply and a load for it, not certain what the CC rating is, something like 2mA, so use a load resistor that is dependent on the supply voltage.
With a 2mA I source and a 9V supply, you need a max load of 4500 ohm, but you have to factor in the insertion losses, vce of the bjts, sense R, so suggest use 1/2 of 4500 ohms or 2k2 for load, voltage impressed on the load is 2mA*2200= 4.4V, leaves 4.6V for the CC comps.
The rep CC source connects up the raw un-regulated DCV and imposed the CC into the summing node of the series pass regulators error amp collector, IIRC.
Give it a try, a quick sanity test

Good luck
Rick

Good luck zebulon1. Us 1980 owners have to watch out for each other or the little guys will gang up on us. :thmbsp:
-John

glen65 said:

About how long did you sell them? 1980 was the last year Pioneer made the SX-1980.

Click to expand...

I've seen them sold new well into the 80's:thmbsp:

Getting ready to rebuild the Power Supply.
First phase:
I just completed and tested the E.W.C.C.S component(s).
Using the 9v battery and Rick's instructions; the first test of the broke 1980 passes, hoping that this is a good sign of things to come!

I promise not to nickel and dime this repair on the forum but this was a milestone and will allow me to sleep well tonight.

Nice
The purists may scoff but I am now in the habit of red dot marking the + side of the board since putting them in backwards is not very helpful
One good thing about working on the big'un is nothing else even attempts to sneak up on the bench for mutual time.
-Lee

Overundr1 said:

Nice
The purists may scoff but I am now in the habit of red dot marking the + side of the board since putting them in backwards is not very helpful
One good thing about working on the big'un is nothing else even attempts to sneak up on the bench for mutual time.
-Lee

Click to expand...

Not around here.

PLENTY of sneaking up around here...

I completed the install of the PS components including the mod for the 24v softstart relay. I still need to go over the board an inspect for self destruct errors.

Posted below are the pictures of the board parts that could use another set of eyes. The E.W.C.C.S's have a black (-) mark signifying the negative side. I did learn from Overundr1.

Thanks for any input!!









Jumper wire for the 24 volt softstart relay mod.

One other thing! :sigh:

What is the best procedure to start up this beast after rebuilding the PS and never hearing this set work?
I checked the outputs and amplifier boards with the components on (visually and with the DMM). No issues.

My plan is to disconnect the Amp boards like we do on the 1250's and then check the power supply voltages before preceding.

Don't forget to look at the images at the end of page one of this thread.

Some how some of my images are not loading to the thread. I will try to correct this tomorrow.

zebulon1 said:

I promise not to nickel and dime this repair on the forum but this was a milestone and will allow me to sleep well tonight.

Click to expand...

I'm not quite sure what you mean by that; but if it means fewer posts...NO! How else are us "little guys"* going to learn?


*Maybe I should put a bumper sticker on my SX-850: "When I grow up I want to be an SX-1250!"

Echowars

I like to replace those two axial caps at the left with radial caps to get them out from under the heatsink. And the 35V zener should be replaced with a series pair of 18V and 17V zeners (suggested by Pioneer in one of their service bulletins). Then you experiment with large value resistors in parallel with R222 and R223 to tweak in the voltage to the desired 80V.

Click to expand...

I plan on adding these suggestions. So, the best way to determine the proper parallel resistor values on R222 and R223 would be get the set operational and then do a voltage drop across the two resistors to find the current? They are rated at a 1/2 watt. Is that to much for a Bourns trimmer attached in parallel?

Edit: On the sx-1250, Pioneer puts the trimmer in series with a 22K resistor to make the 65v. Could a guy come up with a mod to accomplish this for the 80v required?

This is where you say "Someone should go a get that set from his hands"

The 35v zener's are replaced and in this shot the three resistors for the trimmer idea are in view. R221 @ 53k, R223 @ 51K and R218 @ 1K. This is the -80v regulated side. The +80 side, the resistors are spread out. Either way a guy would probably have to build a remote board.

To much work for little benefit?