Tom DORSEY
Active Member
Thanks so much for the illustration. If resistor R66 and R68 are open would that cause low voltage at pin 23 or is the flow in the other direction?
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KENWOOD KR 7050 (NO SOUND)
- Thread starter Tom DORSEY
- Start date
Other direction. Pin 23 (B+) is on the power supply and it supplies power to the amp. I think you were seeing B+ in other places it goes to, so it makes me think there's a high resistance connection somewhere on the way to those resistors. Pretty unlikely that all 3 of the resistors are bad and supplying about the same voltage. There's also a chance you have something still partially shorted that's dragging the voltage down. Those shorted transistors were a good find. Keep checking in that area for more damage. You're doing good.
Tom DORSEY
Active Member
I have been woring on this thing like a all day sucker! I did find a broken trace close to the filter capacitors on RT channel. So remeasured and listed below.
pin 23 = +52.95 vdc
pin 24 = -53.10 vdc
pin 29 = +39.13 AC
Q2
base -51.4 vdc
collector +53.14
emitter -51.9
Q4
base -52.2 vdc
collector -53.30
emitter -52.3
Q3
base -52.48
collector -53.39
emitter -53.14
Q1
base -50.8
collector +53.16
emitter -51.72
Q12
emitter +38.64
collector -37.69
base +39.15
Q11
emitter +38.42
collector -37.42
base +39.05
Q13
emitter +38.23
collector +38.03
base +37.37
Q14
emitter +38.50
collector +31.02
base + 37.91
Q15
emitter -38.31
collector -38.30
base -37.52
Q16
emitter -38.35
collector -38.35
base 37.60
please look @ these measurements ... still relay in protection mode
pin 23 = +52.95 vdc
pin 24 = -53.10 vdc
pin 29 = +39.13 AC
Q2
base -51.4 vdc
collector +53.14
emitter -51.9
Q4
base -52.2 vdc
collector -53.30
emitter -52.3
Q3
base -52.48
collector -53.39
emitter -53.14
Q1
base -50.8
collector +53.16
emitter -51.72
Q12
emitter +38.64
collector -37.69
base +39.15
Q11
emitter +38.42
collector -37.42
base +39.05
Q13
emitter +38.23
collector +38.03
base +37.37
Q14
emitter +38.50
collector +31.02
base + 37.91
Q15
emitter -38.31
collector -38.30
base -37.52
Q16
emitter -38.35
collector -38.35
base 37.60
please look @ these measurements ... still relay in protection mode
No surprise that the relay doesn't click. The voltages on the speaker terminals look really bad so not too worried about the relay yet.
Since you're seeing bad voltages on both channels, the place to check is usually the power supply. Pin 23/24 look good. I notice now that you're getting full B+/B- at those pins and the drivers but less than 40V on the amp board so something is probably shorted and pulling those voltages down on their way there. I think the place to verify all the voltages now is this Voltage Controller section (looks like it's on the amp board). Check the voltages on all the pins and everywhere there's a voltage noted on the schematic. Follow the power through each component and when you find something that doesn't match, pull that component and test it.
Since you're seeing bad voltages on both channels, the place to check is usually the power supply. Pin 23/24 look good. I notice now that you're getting full B+/B- at those pins and the drivers but less than 40V on the amp board so something is probably shorted and pulling those voltages down on their way there. I think the place to verify all the voltages now is this Voltage Controller section (looks like it's on the amp board). Check the voltages on all the pins and everywhere there's a voltage noted on the schematic. Follow the power through each component and when you find something that doesn't match, pull that component and test it.