Something is dramatically wrong, but because it is so dramatic, it ought to be straightforward to find.
Most stark is that there's 0V on pins 5, 6 and the relay coil terminals. The routing of ground is a real maze, but try to sort through it with your meter and the schematic as a guide. Is all cabling connected? (Some circuit paths seem to daisy chain through modules.)
Use both techniques of continuity testing with your meter and active tracing of active supply voltages to follow where voltage is/should be flowing. For example, there should be continuity from the 9V regulator ground terminal to IC6401 pin/pad 5, but I'm not confident the path is intact. Alternately, why isn't +9 appearing at the relay at relay coil?
Earlier, you reported +11V at the IC1503 regulator site. I suggest keeping the black meter probe tied to the regulator "ground" and follow the regulator output toward the relay coil. It should show +11(+9 proxy) at the coil terminals. There will be an open somewhere, or +11 should appear at pin 6 of IC6401; if it's +11 at pin 6, what shows at pin 5? Jumpering to pin 5, should close the relay, but may not if there's a faulty ground path. Reconciling these mysteries is key to getting the protection working; the authenticity/health of uPC1237 is a separate issue.
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I found a burnt trace which was causing the lack of voltage at the relay coil..I have repaired it and now have 11v at the coil..If I shunt the voltage to ground on the relay board the switch closes. but I still dont have voltage at the ic pin 6 for the relay and if I short to ground at the ic pins it does not close relay switch.
Try following the coil voltage towards the anode of D6401, through cable towards R6402 and on to pin 6. Be alert to increased resistance preventing relay activation. Allso, try a jumper from either side of the resistor back to regulator ground.
Some progress, but not solved yet. I am now getting 11v at pin 6 . Ive installed a replacement upc1237 and voltages read as pin 1 0v, pin 2 .7v, pin 3 0v, pin 4 1.9v, pin 5 0v, pin 6 11.3v, pin 7 0v (however it initially rises slowly to 2v then drops to 0v and stays there), pin 8 3v. Also, if I jumper pin 6 to ground on 5 the relay switch activates. Ideas?
Thank you for all the suggestions.
Thank you for all the suggestions.
According to uPC1237 data sheet, 2.7V at pin 2 is more than enough to trigger protection, so that will need to be explored. Pin 1 is the only other sense "input" and looks OK. As an experiment, I suggest shorting pin 2 to ground; with luck, the relay will close. Of course, this experiment should be without any load on output terminals.
I'm going to be optimistic and assume the relay closes, so remove the pin 2 short. Then we'll explore why pin 2 is too high.
Pin 2 is intended to monitor the amp outputs for excessive DC (via R6301, R6302). The implication is that there's trouble in one or both of the Power Amps. My bad for neglecting to ask about DC on each output as a first question. So would you report DCV at "SP OUT, L CH" and
"SP OUT, R CH" with respect to ground.
Thanks!
I'm going to be optimistic and assume the relay closes, so remove the pin 2 short. Then we'll explore why pin 2 is too high.
Pin 2 is intended to monitor the amp outputs for excessive DC (via R6301, R6302). The implication is that there's trouble in one or both of the Power Amps. My bad for neglecting to ask about DC on each output as a first question. So would you report DCV at "SP OUT, L CH" and
"SP OUT, R CH" with respect to ground.
Thanks!
Alternatively you can measure Vdc at the bias test point TP1 (left) to GND, repeat for TP3(right) to GND, both should be less than 100mV.
If problem is left channel, measure Vdc at connector CB7501 pin 7 to GND. Repeat for pin 8 to GND.
For the right channel, connector CB7502 pin 2 then pin 3.
Expect about +/-1.3V the faulty channel may have about 4V.
If problem is left channel, measure Vdc at connector CB7501 pin 7 to GND. Repeat for pin 8 to GND.
For the right channel, connector CB7502 pin 2 then pin 3.
Expect about +/-1.3V the faulty channel may have about 4V.
No Vdc detected on speaker outputs.
CB7501 1 is 0v, 2 is 0v ,3 is 60v, 4 is 60v, 5 is -60v, 6 is 0v , 7 is -2.5v, 8 is -2.5v, 9 is -39
For CB7502 1 is 0v, 2 is 29v , 3 is -60v,4 is 60v, 5 is -60v, 6 is 0v, 7 is -.4v, 8 is -.4v, 9 is -30v
CB7501 1 is 0v, 2 is 0v ,3 is 60v, 4 is 60v, 5 is -60v, 6 is 0v , 7 is -2.5v, 8 is -2.5v, 9 is -39
For CB7502 1 is 0v, 2 is 29v , 3 is -60v,4 is 60v, 5 is -60v, 6 is 0v, 7 is -.4v, 8 is -.4v, 9 is -30v
The protection relay is not closing so the power amp is not connected to the speaker connectors
so expect 0Vdc at speaker connectors. What BSST requested was VDC at "SP OUT L CH" and "SP OUT R CH"
these are pins/wire wrap posts #1 and #3 on the power amp board.
CB7501 1 is 0v, 2 is 0v ,3 is 60v, 4 is 60v, 5 is -60v, 6 is 0v , 7 is -2.5v, 8 is -2.5v, 9 is -39
CB7501
1 is 0v GND ok
2 is 0v Expect +30V <<<< recheck
3 is 60v Expect -30 <<<< recheck
4 is 60v ok
5 is -60v ok
6 is 0v GND ok
7 is -2.5v should be +ve
8 is -2.5v
9 is -39 (feedback from SP OUT L CH)
CB7502
Think you got the pinout wrong,
For CB7502 1 is 0v, 2 is 29v , 3 is -60v,4 is 60v, 5 is -60v, 6 is 0v, 7 is -.4v, 8 is -.4v, 9 is -30v
1 is 0v, Actual Pin 9 GND, ok
2 is 29v Actual Pin 8 -30
3 is -60v Actual Pin 7 +30, <<<< recheck
4 is 60v Actual Pin 6 -61
5 is -60v Actual Pin 5 +61
6 is 0v Actual Pin 4 is GND, ok
7 is -.4v Actual Pin 3
8 is -.4v Actual Pin 2
9 is -30v Actual Pin 1 (feedback from SP OUT R CH)
Give BSST a chance to digest results, plz recheck items as indicated, need to sort out the power supply
so expect 0Vdc at speaker connectors. What BSST requested was VDC at "SP OUT L CH" and "SP OUT R CH"
these are pins/wire wrap posts #1 and #3 on the power amp board.
CB7501 1 is 0v, 2 is 0v ,3 is 60v, 4 is 60v, 5 is -60v, 6 is 0v , 7 is -2.5v, 8 is -2.5v, 9 is -39
CB7501
1 is 0v GND ok
2 is 0v Expect +30V <<<< recheck
3 is 60v Expect -30 <<<< recheck
4 is 60v ok
5 is -60v ok
6 is 0v GND ok
7 is -2.5v should be +ve
8 is -2.5v
9 is -39 (feedback from SP OUT L CH)
CB7502
Think you got the pinout wrong,
For CB7502 1 is 0v, 2 is 29v , 3 is -60v,4 is 60v, 5 is -60v, 6 is 0v, 7 is -.4v, 8 is -.4v, 9 is -30v
1 is 0v, Actual Pin 9 GND, ok
2 is 29v Actual Pin 8 -30
3 is -60v Actual Pin 7 +30, <<<< recheck
4 is 60v Actual Pin 6 -61
5 is -60v Actual Pin 5 +61
6 is 0v Actual Pin 4 is GND, ok
7 is -.4v Actual Pin 3
8 is -.4v Actual Pin 2
9 is -30v Actual Pin 1 (feedback from SP OUT R CH)
Give BSST a chance to digest results, plz recheck items as indicated, need to sort out the power supply
Happy New Year!
@mbz
Thank you for helping sort this out and making data easier to understand. Very much appreciated!
@Vmazzoneclementi
Would you perform followup rechecks of the voltages that mbz indicated? And do a general inspection of the the power supply supplies and grounds. I suggest connecting the voltmeter's black lead to a speaker binding post so that you maintain a consistent reference point. Make sure your red probe lead is covered with heat shrink tubing to reduce the chance of accidental contacts.
All the supply voltages (and grounds) must be behaving properly before tackling the power amp sections. It appears mbz has already observed a problem on CB7501 ("9 is -39 (feedback from SP OUT L CH"). I foresee a challenging repair ahead.
@mbz
Thank you for helping sort this out and making data easier to understand. Very much appreciated!
@Vmazzoneclementi
Would you perform followup rechecks of the voltages that mbz indicated? And do a general inspection of the the power supply supplies and grounds. I suggest connecting the voltmeter's black lead to a speaker binding post so that you maintain a consistent reference point. Make sure your red probe lead is covered with heat shrink tubing to reduce the chance of accidental contacts.
All the supply voltages (and grounds) must be behaving properly before tackling the power amp sections. It appears mbz has already observed a problem on CB7501 ("9 is -39 (feedback from SP OUT L CH"). I foresee a challenging repair ahead.
I will recheck. But I think I have shorts now in q1107 and q1109. I have the amp on the current limiter now and it is showing a short. I will follow the recomendation for covering the probe. I likely made some unwanted contact when checking voltages. I cant check proper voltages until im off the current limiter. I saw some smoke around the q1107 q1108 pair and the q1109 andq1110 pair and shut it down. I will report back when I get those replaced.
Ok. So I have replaced q1107 q1108 and q1109 q1110 with equivalent npn pnp transistors. No shorts with current limiter showing. I have taken voltages at CB7501 not sure if i have them reveresed in order but starting from the NF labeled side
CB7501
1. 56v
2. 55v
3. .5v
4. 0v
5. -61
6. 60v
7. 0v
8. 0v
9. 0v
CB7502
1. .2v
2. -1.5v
3. 2v
4. 0v
5. -61v
6. 60v
7. -59v
8. 29v
9. 0v
.
CB7501
1. 56v
2. 55v
3. .5v
4. 0v
5. -61
6. 60v
7. 0v
8. 0v
9. 0v
CB7502
1. .2v
2. -1.5v
3. 2v
4. 0v
5. -61v
6. 60v
7. -59v
8. 29v
9. 0v
.
Appears CB7501 wrong pinout
CB7501 Reverse Pinout
1. 56v 0V GND
2. 55v 0V +30V rail
3. .5v 0V -30V rail
4. 0v 60V +51V rail
5. -61 -61V -51V rail
6. 60v 0V GND
7. 0v 0.5V base npn driver, expect about +1.3V
8. 0v 55V base pnp driver<<<<<<
9. 0v 56V SP OUT L CH<<<<<<<
Pinout appears OK
CB7502
1. .2v SP OUT R CH, a little high
2. -1.5v approx pnp driver base, ok
3. 2v approx npn driver base, expect about +1.3V
4. 0v GND
5. -61v +61V rail
6. 60v -61V rail
7. -59v +30V rail
8. 29v -30V rail
9. 0v GND
Left channel look sickest. Either outputs Q7509 or Q7513 or driver Q7505(c-e) has failed short.
Possibly consider pulling the left channel outputs and replace one npn/pnp pair with 1N4148 (or whatever handy) between output b-e
then sort out any other (bias?) issues then reinstall outputs...
CB7501 Reverse Pinout
1. 56v 0V GND
2. 55v 0V +30V rail
3. .5v 0V -30V rail
4. 0v 60V +51V rail
5. -61 -61V -51V rail
6. 60v 0V GND
7. 0v 0.5V base npn driver, expect about +1.3V
8. 0v 55V base pnp driver<<<<<<
9. 0v 56V SP OUT L CH<<<<<<<
Pinout appears OK
CB7502
1. .2v SP OUT R CH, a little high
2. -1.5v approx pnp driver base, ok
3. 2v approx npn driver base, expect about +1.3V
4. 0v GND
5. -61v +61V rail
6. 60v -61V rail
7. -59v +30V rail
8. 29v -30V rail
9. 0v GND
Left channel look sickest. Either outputs Q7509 or Q7513 or driver Q7505(c-e) has failed short.
Possibly consider pulling the left channel outputs and replace one npn/pnp pair with 1N4148 (or whatever handy) between output b-e
then sort out any other (bias?) issues then reinstall outputs...
That +/-30V rail on the left channel also looks sick, noted Q1107, Q1108 already replaced.
b/c/e voltages to GND for both Q's may show something, possibly a burnt trace?
Update. SO yes their was issues at q1107,q1108 , it was the zener diodes, one blown completely. Replaced both with 30v zeners. I now have same voltage readings at cb7501 as cb7502 and after replacing the thermal protector q7601 I have the relay switching for speaker connectivity.
I did pull q7509 and q7513 and installed a 1n4148 diode with anode to base on both. Voltages seem good. Should I reinstall q7509 - q7513?
I did pull q7509 and q7513 and installed a 1n4148 diode with anode to base on both. Voltages seem good. Should I reinstall q7509 - q7513?
Yeah, I think so. Certainly use a DBT/current limiter on first power up after installing Q7509, Q7513.