simple - it gets cooked over it's life, it and the protect board greatly benefit and protect the receiver's longevity when they are rebuilt (caps, transistors etc from the lists).
Pioneer SX-950 Power Up
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simple - it gets cooked over it's life, it and the protect board greatly benefit and protect the receiver's longevity when they are rebuilt (caps, transistors etc from the lists).
My gut feeling is that the serious issues have been corrected and the receiver would run ok after the recap of the amp board, BUT my gut has gotten me in trouble before and I can't risk having to go back and redo everything, so I'm digging into the Power Supply Board (AWR-101-C).
Questions:
1) Capacitor @ C12 is listed as 1000uF 35v, but is actually 2200uF 35v, is this a known change in design? The board is lettered AWR-101-C.
2) Some of the capacitors are 3 legged, with 1 leg appearing to be a support only, as they aren't connected to a trace. Is that a correct assumption?
3) Am considering leaving 2SD313D, 2SB507D, and 2SD313E alone, as my past experience tells me that they seem to be pretty hardy, and I can't remember ever finding a bad one. What's your experience suggest?
Questions:
1) Capacitor @ C12 is listed as 1000uF 35v, but is actually 2200uF 35v, is this a known change in design? The board is lettered AWR-101-C.
2) Some of the capacitors are 3 legged, with 1 leg appearing to be a support only, as they aren't connected to a trace. Is that a correct assumption?
3) Am considering leaving 2SD313D, 2SB507D, and 2SD313E alone, as my past experience tells me that they seem to be pretty hardy, and I can't remember ever finding a bad one. What's your experience suggest?
1. go with what you found
2. 1 is support, and there are caps called snap-in where there is a specific spacing and larger holes with a stronger mount. Which ones are they? do they have 10mm spacing between the holes?
3. these are the major focus of the replacements, having been the source of the heat cooking the board for years. mje15032, mje15033 (if listed, or not it's an old list) are more heat resistant - just something about the on-semi's - and in a power supply the slightly different operating voltages do not matter like they would in an amplifier driver circuit using stv type diodes.
2. 1 is support, and there are caps called snap-in where there is a specific spacing and larger holes with a stronger mount. Which ones are they? do they have 10mm spacing between the holes?
3. these are the major focus of the replacements, having been the source of the heat cooking the board for years. mje15032, mje15033 (if listed, or not it's an old list) are more heat resistant - just something about the on-semi's - and in a power supply the slightly different operating voltages do not matter like they would in an amplifier driver circuit using stv type diodes.
yes. use heat sink grease.
Making progress.
I think (hope) I'm done with the AWH-050 Amp Board. All transistors have been replaced, using heat sink grease where needed, all capacitors have been replaced, diodes as needed, resistors as needed, traces repaired.
Partially done with AWR-101 Power Supply Board. All transistors have been replaced, using heat sink grease where required, no transistors tested bad. Partially recapped with a few caps to go. Gonna replace the large SR3AM-8 Diodes D5-D8 with 10A04-T, even though they test good, as I understand they are somewhat under spec'd from factory. Other diodes tested OK. Replaced Resistor R3 (15K), it looked dark and as I was extracting it one lead broke off, was definitely weak, the resistor tested within spec but had most certainly been hot.
I took the cover off the relay to check the contacts. No signs of distress, but touched up the contacts with very fine sandpaper.
On the AWM-062 Protection Board I'm going to replace all the capacitors and leave the transistors as in for now.
Was hoping to get this completed before Christmas but with all the Holiday happenings, looks like it's going to go past that. Will update when I think I'm finished.
I think (hope) I'm done with the AWH-050 Amp Board. All transistors have been replaced, using heat sink grease where needed, all capacitors have been replaced, diodes as needed, resistors as needed, traces repaired.
Partially done with AWR-101 Power Supply Board. All transistors have been replaced, using heat sink grease where required, no transistors tested bad. Partially recapped with a few caps to go. Gonna replace the large SR3AM-8 Diodes D5-D8 with 10A04-T, even though they test good, as I understand they are somewhat under spec'd from factory. Other diodes tested OK. Replaced Resistor R3 (15K), it looked dark and as I was extracting it one lead broke off, was definitely weak, the resistor tested within spec but had most certainly been hot.
I took the cover off the relay to check the contacts. No signs of distress, but touched up the contacts with very fine sandpaper.
On the AWM-062 Protection Board I'm going to replace all the capacitors and leave the transistors as in for now.
Was hoping to get this completed before Christmas but with all the Holiday happenings, looks like it's going to go past that. Will update when I think I'm finished.
I think I'm ready to button everything down and power up for voltage checks.
In general here is what I have done:
1) AWH-050 Amp Board: Replaced Transistors Q1-Q12, Capacitors C1-C6, C11, C12, Diodes D7-D10, Resistors R51, R53, R55, R57, R58, R37, R39, R67, Trimpots VR3, VR4.
2)AWR-101 Power Supply Board:Replaced Transistors Q1-Q10, Capaciors C10-C16, C18-C21, C23, Diodes D1-D4, Resistor R3, Checked Fuses.
3) AWM-062 Protection Board:Replaced Capacitors C1-C6.
Tested a boat load of resistors.
All controls cleaned.
Relay contacts touched up.
What else should I do before powering up?
In general here is what I have done:
1) AWH-050 Amp Board: Replaced Transistors Q1-Q12, Capacitors C1-C6, C11, C12, Diodes D7-D10, Resistors R51, R53, R55, R57, R58, R37, R39, R67, Trimpots VR3, VR4.
2)AWR-101 Power Supply Board:Replaced Transistors Q1-Q10, Capaciors C10-C16, C18-C21, C23, Diodes D1-D4, Resistor R3, Checked Fuses.
3) AWM-062 Protection Board:Replaced Capacitors C1-C6.
Tested a boat load of resistors.
All controls cleaned.
Relay contacts touched up.
What else should I do before powering up?
tsd71
RIP Tom Petty
Check everything before powering up, look for broken wire connections, transistor leg placements, capacitor placement....Make sure you power up on the dim bulb, I start with 75 watt then go to 100, also make sure you twist the idle current trimpots VR3 & VR4 all the way counterclockwise before any power. If she fires up on the 75 watter and the relay clicks and the bulb dims, go to the 100 watter, then if that goes ok then stick the plug in the wall and you should be good.
Thanks. If you noticed early in this post, that I am going to power up without the TO-3 outputs installed, considering the state the receiver was in when I got it. No need to fry new outputs. I do think I have the situation corrected, but was going to take voltage readings before installing the new TO-3's and also see if other issues arise. I don't believe the relay will be in play at that point since it is dependant upon the outputs. Am I thinking correctly?
I do see the SM says to adjust VR3, VR4 fully counterclockwise, but doesn't address the power up setting for VR1, VR2, but from what I've read fully counterclockwise is the setting for VR1, VR2 also.
I'm thinking I will start with a 60 watt bulb initially and then a 100 watt if all goes well.
I do see the SM says to adjust VR3, VR4 fully counterclockwise, but doesn't address the power up setting for VR1, VR2, but from what I've read fully counterclockwise is the setting for VR1, VR2 also.
I'm thinking I will start with a 60 watt bulb initially and then a 100 watt if all goes well.
Dim Bulb Power Up Good.
Full Power Good.
Shows how little I know, relay does trigger without TO-3 Outputs.
Relay triggers in about 4 seconds.
AWR-101 Power Supply Voltage Measurements:
Pin 2/3 = 6.2v DC (5.4v)
Pin 4/5 = 13.3v DC (13.9v)
Pin 6/7 = 49.3v DC (51.5v)
Pin 8/9/10 = 35.4v DC (36.5v)
Pin 11 = 27.3v DC (28.0v)
Pin 13 = -13.7v DC (-13.5v)
Pin 14 = -52.5v DC (-51.5v)
Pin 15 = -19.4v DC (-19.0v)
AWH-050 Power Amp Board Voltage Measurements:
Pin 2 = -52.6v DC (-51.5v)
Pin 4 = 35.4v DC (36.5v)
Pin 7 = 49.3v DC (51.5v)
Pin 14 = 51.0v DC (49.5v)
Pin 15 = -51.3v DC (-49.5v)
Pin 17 = -52.6v DC (-51.5v)
Pin 19 = 35.4v DC (36.5v)
Pin 22 = 49.3v DC (51.5v)
Pin 29 = 51.1v DC (49.5v)
Pin 30 = -51.2v DC (-49.5)
**Parentheses = SM Spec.
What other voltages should I check?
Set VR1, VR2 to 0v +-
VR3, VR4 do not seem to have any adjustment at this point. Would that be the case without the outputs installed? I didn't turn them very far at this point.
Full Power Good.
Shows how little I know, relay does trigger without TO-3 Outputs.
Relay triggers in about 4 seconds.
AWR-101 Power Supply Voltage Measurements:
Pin 2/3 = 6.2v DC (5.4v)
Pin 4/5 = 13.3v DC (13.9v)
Pin 6/7 = 49.3v DC (51.5v)
Pin 8/9/10 = 35.4v DC (36.5v)
Pin 11 = 27.3v DC (28.0v)
Pin 13 = -13.7v DC (-13.5v)
Pin 14 = -52.5v DC (-51.5v)
Pin 15 = -19.4v DC (-19.0v)
AWH-050 Power Amp Board Voltage Measurements:
Pin 2 = -52.6v DC (-51.5v)
Pin 4 = 35.4v DC (36.5v)
Pin 7 = 49.3v DC (51.5v)
Pin 14 = 51.0v DC (49.5v)
Pin 15 = -51.3v DC (-49.5v)
Pin 17 = -52.6v DC (-51.5v)
Pin 19 = 35.4v DC (36.5v)
Pin 22 = 49.3v DC (51.5v)
Pin 29 = 51.1v DC (49.5v)
Pin 30 = -51.2v DC (-49.5)
**Parentheses = SM Spec.
What other voltages should I check?
Set VR1, VR2 to 0v +-
VR3, VR4 do not seem to have any adjustment at this point. Would that be the case without the outputs installed? I didn't turn them very far at this point.
Question:
Just trying to make sure everything is good to go.
I replaced the 100 ohm Trimpots VR3, VR4 with some 100 ohm trimpots out of a donar unit. Connecting an Ohm Meter to the center leg and right leg and turning the pot clockwise, the resistance starts at 0 ohms and steadily increases to 100 ohms. But when I test from center leg to left leg I get a .2 ohm reading and turning the pot clockwise produces no change at all. Both VR3 and VR4 test the same. Preforming the same test on the 10k pots, as the pot is turned clockwise the ohms increase when connected center leg and right leg, but decrease when connected to center leg and left leg. In other words the 10k pots start at 0 ohms and increase with one pair of legs, and start at 10k ohms and decrease when connected to the other pair of legs. Do I have a problem with the VR3, VR4 100 ohm trimpots? As they do not seem to function the same as the 10k trimpots.
Just trying to make sure everything is good to go.
I replaced the 100 ohm Trimpots VR3, VR4 with some 100 ohm trimpots out of a donar unit. Connecting an Ohm Meter to the center leg and right leg and turning the pot clockwise, the resistance starts at 0 ohms and steadily increases to 100 ohms. But when I test from center leg to left leg I get a .2 ohm reading and turning the pot clockwise produces no change at all. Both VR3 and VR4 test the same. Preforming the same test on the 10k pots, as the pot is turned clockwise the ohms increase when connected center leg and right leg, but decrease when connected to center leg and left leg. In other words the 10k pots start at 0 ohms and increase with one pair of legs, and start at 10k ohms and decrease when connected to the other pair of legs. Do I have a problem with the VR3, VR4 100 ohm trimpots? As they do not seem to function the same as the 10k trimpots.
TO-3 Outputs installed.
DBT Power Up Good 60 & 100 Watt.
Full Power Good.
Set VR1, VR2 to 0mV +-
Set VR3, VR4 to 20mV
Everything holding good, no smoke.
Let it run all last night, still good today.
This thing will rock the block.
Will recheck settings again today or tomorrow.
One bummer: the FM is distorted, I was wondering why the tuner cover was removed and missing, that jack leg tech must have screwed with the tuner and got it whacked out. I don't know diddly about aligning a tuner, looks like brain surgery.
Thanks to markthefixer, zebulon1, and tsd71.
DBT Power Up Good 60 & 100 Watt.
Full Power Good.
Set VR1, VR2 to 0mV +-
Set VR3, VR4 to 20mV
Everything holding good, no smoke.
Let it run all last night, still good today.
This thing will rock the block.
Will recheck settings again today or tomorrow.
One bummer: the FM is distorted, I was wondering why the tuner cover was removed and missing, that jack leg tech must have screwed with the tuner and got it whacked out. I don't know diddly about aligning a tuner, looks like brain surgery.
Thanks to markthefixer, zebulon1, and tsd71.
Just a few questions and reminders about the distorted FM signal:
Before getting too carried away with any cleaning or tweaking of the tuner board, document it's current settings by notes and/or good resolution photos of the trimmers, chokes, and transformers' adjustments. If you inadvertently move something you will at least have a baseline.
- Make sure a reasonable antenna is installed;
- Verify the function switches are clean;
- Do the MPX noise filter and/or FM Mute off switches have any effect?
- Is the FM de-emphasis switch clean and set at 75µS?
- Is the distortion present in both channels?
- Is the distortion changed in MONO mode?
- Is the distortion approximately equal on both strong local stations and weaker stations?
Before getting too carried away with any cleaning or tweaking of the tuner board, document it's current settings by notes and/or good resolution photos of the trimmers, chokes, and transformers' adjustments. If you inadvertently move something you will at least have a baseline.