Ampeg BA115HP Output and crackling/static

[ca7922303]

all further measurements at this point:

At (102.1vac)R31 is @ (-50.0vdc).

and measure the DC voltages again: b-e Q4, b-e Q1, TP10, TP11

@(101.5vac)R31(-50vdc)
Q1-B-E(0.5vdc)
Q4-B-E(0.7vdc)
TP10(-11vdc)
TP12(0.0mvdc)
Q1-B(-12vdc)C(-50vdc)E(-12vdc)
Q4-B(-6vdc)C(-7vdc)E(-7vdc)

[x-pro]

R34 is not 270 ohms?

[ca7922303]

R34 is not 270 ohms?

R34(268ohms)

[g1]

What is DC volts at each end of R34?

[ca7922303]

What is DC volts at each end of R34?

R34(+50/+50vdc)@(101.5vac Variac)

[g1]

R34 is not 270 ohms?

x-pro wanted to know why there is not approx. 50V at Q4 collector. If R34 is good, and you have 50VDC at both ends, there must be a broken or burnt connection between R34 and Q4.

[ca7922303]

x-pro wanted to know why there is not approx. 50V at Q4 collector. If R34 is good, and you have 50VDC at both ends, there must be a broken or burnt connection between R34 and Q4.

Yeah, I'm getting (33m/33m ohms) from Q4-Collector to both sides of R134. I'll have to pull board again to check. Will get to it tomorrow. Thanks.

[ca7922303]

x-pro wanted to know why there is not approx. 50V at Q4 collector. If R34 is good, and you have 50VDC at both ends, there must be a broken or burnt connection between R34 and Q4.

Reflowed Q4 collector:
Q4-B (+3vdc)C(+50vdc)E(+2.4vdc)@(107vac Variac)
Q1-B (-3vdc)C(-50vdc)E(-2.6vdc)
TP10(-70mvdc)
TP12(0.4mvdc)
Q1-B-E(-0.5vdc)
Q4-B-E(-0.5vdc)
U5-Pin 5(-0.7mvdc)
Have normal headphone output, but no speaker output.

[x-pro]

That's good. That's better.
Now we're going to look for what we've lost

[ca7922303]

That's good. That's better.
Now we're going to look for what we've lost

✓✓

[x-pro]

you need to reconnect everything as follows

[x-pro]

While I'm gone, do the following:
additionally desolder OC1 and C12.
And at 1kHz input sine 250mV, measure the AC at TP12

[ca7922303]

While I'm gone, do the following:
additionally desolder OC1 and C12.
And at 1kHz input sine 250mV, measure the AC at TP12

Signal thru input?

[x-pro]

on +C11

[ca7922303]

you need to reconnect everything as follows

Not able to read the photo. Can you upload a better copy? Thanks.