Pioneer SX-727 AWM-027 "D" Speaker Protection Board Partial Rehab

jc339

Active Member
After trying unsuccessfully to find out which specific component(s) might be bad by changing a few components and checking several voltages, with guidance from other active participants, the next step is to replace several components on the AWM-027 Speaker Protection board, including replacing the protection relay switch. I've ordered all the transistors, capacitors, diodes, and the "fly-back diode", also a new relay switch.

IMG_1489.JPG


AWM-027 Circuitry Board.jpg
 
The first thing as a start is always the power supply board. Only if you have every single voltage according to the schematic correct, you can jump/continue with the next board.
Hope you have and use a DBT as a helpful protection tool!!
 
I believe in the early beginning of my original thread for this problem, merlynski had me check some power board voltages and I think they checked out OK and that's when we started concentrating on the speaker protection board. I don't have a light bulb tool. Thanks.
 
I believe in the early beginning of my original thread for this problem, merlynski had me check some power board voltages and I think they checked out OK and that's when we started concentrating on the speaker protection board. I don't have a light bulb tool. Thanks.
You now have a new meter and better skills, and the old thread is gone, so lets verify them again:
Please post dc volts, black clipped to chassis, measure with red lead:

AWR-011, Power Supply
Pin 7, should be +36vdc:
Pin 6, sb +30vdc:
Pin 5, sb +30vdc:
Pin 1, sb 0v:
Pin 2, sb +12.5vdc:
Pin 11, sb 0vdc:

AWM-027 D, Protection
Pin 16, sb +35vdc:
Pin 6, sb -13vdc:
Pin 7, sb 0vdc:

Measure AC volts
Pin 17, sb 7.5vAC:

Further measurement will be needed after the parts come in and the board is rebuilt.
 
Will do...Thanks for saying VDC or VAC...that helps since it seems like the same pins can both AC and DC sometimes.
 
You now have a new meter and better skills, and the old thread is gone, so lets verify them again:
Please post dc volts, black clipped to chassis, measure with red lead:

AWR-011, Power Supply (meter selector set to 200 v dc)
Pin 7, should be +36vdc: (-)00.9 VDC
Pin 6, sb +30vdc: (-)00.84 VDC
Pin 5, sb +30vdc: (-)00.8 VDC
Pin 1, sb 0v: (-)00.0 VDC
Pin 2, sb +12.5vdc: (-)00.0 VDC
Pin 11, sb 0vdc: (-)00.0 VDC

AWM-027 D, Protection ( METERS SELECTOR SET TO 200 vac)
Pin 16, sb +35vdc: the(-)00.9 VDC
Pin 6, sb -13vdc: (-)12.5 vdc
Pin 7, sb 0vdc: (-)00.0 vdc

Measure AC volts
Pin 17, sb 7.5vAC: 07.5 VAC
 
this is the board I measured.
It looks problematic, eh?

upload_2020-6-1_16-9-42.jpeg

AWR-011, Power Supply (meter selector set to 200 v dc)

MINUS SIGN APPEARS TO BLINK EVERY FEW SECONDS OR SO
Pin 7, should be +36vdc: (-)00.9 VDC
Pin 6, sb +30vdc: (-)00.84 VDC
Pin 5, sb +30vdc: (-)00.8 VDC
Pin 1, sb 0v: (-)00.0 VDC
Pin 2, sb +12.5vdc: (-)00.0 VDC
Pin 11, sb 0vdc: (-)00.0 VDC

AWM-027 D, Protection
Pin 16, sb +35vdc: the(-)00.9 VDC
Pin 6, sb -13vdc: (-)12.5 vdc
Pin 7, sb 0vdc: (-)00.0 vdc

Measure AC volts( METERS SELECTOR SET TO 200 vac)
Pin 17, sb 7.5vAC: 07.5 VAC
 
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Check the battery in your meter. The minus sign should not be blinking. Look in the Meter Manual and see what a blinking minus sign means.

AWM-027 D, Protection ( METERS SELECTOR SET TO 200 vac)
Pin 16, sb +35vdc: the(-)00.9 VDC
Pin 6, sb -13vdc: (-)12.5 vdc
Pin 7, sb 0vdc: (-)00.0 vdc


These should be measured on the dcv scale not METERS SELECTOR SET TO 200 vac
 
Red wire pin 16 on AWM-027 was broken off. I saw that and resoldered it to pin 16. I looked at the photos of the board and it's got to be pin 16 red wire.

I'm remeasuring the voltages again...I've been moving the board around to get better access to it and that's when the wire may have broken. Those look like steel wires that wrap around the pins like a tight circular wrap.

AWR-011, Power Supply
Pin 7, should be +36vdc: -00.9 not blinking nb goes to pin 16 on AWR-027 and has continuity after I resoldered
Pin 6, sb +30vdc: -00.8 nb
Pin 5, sb +30vdc: -00.8 nb
Pin 1, sb 0v: -00.0 blinking bl after 4 sec
Pin 2, sb +12.5vdc: -00.0 bl
Pin 11, sb 0vdc: 00.0 bl

AWM-027 D, Protection
Pin 16, sb +35vdc: -00.9 nb
Pin 6, sb -13vdc: -12.5
Pin 7, sb 0vdc: -00.0 bl after 3 sec

Measure AC volts
Pin 17, sb 7.5vAC: 7.5 ac

checked and rechecked Meter is OK Used both meters I have same results
Pin 17, sb 7.5vAC:
 
Put your meter on AC volts, with power on,
On the AWR-011 Power Supply board measure with one lead on pin 9 and one lead on pin 10. You should have about 30 volts AC.
 
Measured ac volts one lead on pin 9 and one lead on pin 10 with setting on ACV meter and got 0.00 Power turned ON
 
Could I have a blown fuse(s) at F3 and or F4? Looks like AWR-011 pin 9 and 10 go to those fuses. For paul_ral "Ma intreb daca sunt corect" means: I wonder if I'm correct...Well my Romanian isn't that good but I tried...:)
 
I placed my meter across Fuse F3 and F4 (not removed or unsoldered) and was unable to get continuity across those 2 each 0.5Amp fuses. Do I have to unsolder the fuses to properly test for continuity or is there a better way to test to see if they are blown?

The fuse F1 still checks out good and all the lights on the front panel light up, so it looks like that fuse is good...

Luckily when we set up my Mouser's order for all the parts for the AWM-027 I ordered about 10 each of the 3A and 0.5A fuses during that order. I think that's correct. I'll go back and double check that...Confirmed I ordered 10 of each 3A and 0.5A to arrive in a few days or so.

Blown fuses.jpg
 
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Well JC my english isn't that good too. Some people find Romanian language to be a romantic language It's easy to learn it. Luckily for us, electronic has a single language.
Down to the business now. You have a short somewhere, maybe that desoldered red wire has done that. Replace 0.5 fuses and start your SX on DBT. One short happened in my SX too and the fuses blows, because a pin from control amp touch the under cover.
 
Thanks. That makes sense. I lifted the awr-011 board off the tabs to see if there were any broken wires and if the red wire to pin 16 on the Awm-027 Was broken. But it looked ok. My new parts for the speaker protection board along with several fuses I ordered should be here in a few days.
 
I placed my meter across Fuse F3 and F4 (not removed or unsoldered) and was unable to get continuity across those 2 each 0.5Amp fuses. Do I have to unsolder the fuses to properly test for continuity or is there a better way to test to see if they are blown?

The fuse F1 still checks out good and all the lights on the front panel light up, so it looks like that fuse is good...

Luckily when we set up my Mouser's order for all the parts for the AWM-027 I ordered about 10 each of the 3A and 0.5A fuses during that order. I think that's correct. I'll go back and double check that...Confirmed I ordered 10 of each 3A and 0.5A to arrive in a few days or so.

I concur with blown fuses. You will have to unsolder them to test for certain.
I note on the picture in post 14 you say "Zero vdc". That measurement will never have a DC voltage present measured across those pins, AC only.
The wire to pin 16 on the AWM-027 comes from pin 7 on the AWR-011 Power Supply, +36vdc line fed by those fuses. You may have damaged Q1 (2SD313) and/or R1 (10Ω) on the AWR-011 pcb. Test them if you can.
 
One lesson I learned is that the steel wires that curl tightly around the boards are evidently very brittle and don't allow much manipulation before they snap off.

My order for all the transistors, capacitors, diodes, and extra fuses says it will arrive here by tomorrow night.
 
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