power bd1000a issues

[86boy]

I think so... I could have wrote them down incorrectly.

Here's where they are currently:

Q20 and Q21 has the MPSA06
Q17 and Q19 has the MPSA56

 

[Perry Babin]

That's correct. Post the DC voltage on all legs of one pair of driver transistors (the ones with the lowest base voltage).

 

[86boy]

while looking at these again I realized I put Q17 in backwards *facepalm* I thought those voltages looked a bit weird, and here they are:

Q17
1 - 0
2 - 3.19
3 - 3.35

Q20
1 - 3.35
2 - 3.24
3 - 12.5

 

[Perry Babin]

Q17 is backwards now, from the numbers. The collector of the PNP drivers goes to ground (0v).

 

[86boy]

yes I physically installed it incorrectly those were the numbers from when it was backwards. Here's the updated numbers with a new MPSA56 installed correctly now of all driver transistors:

Q19
1 - 3.4
2 - 3.6
3 - 0

Q21
1 - 3.35
2 - 3.6
3 - 12.5

Q17
1 - 3.4
2 - 3.65
3 - 0

Q20
1 - 3.1
2 - 3.4
3 - 12.5

 

[Perry Babin]

What's the DC voltage on pins 14 and 17 of the SG3526?

 

[86boy]

u14 SG3526
pin 14 - 12.65v
pin 17 - 12.82v

 

[Perry Babin]

Are the drivers still getting hot?

Have you ever used your meter to measure the DC on a drive circuit?

What meter do you have (link to owner's manual).

 

[86boy]

drivers are not getting hot anymore now that Q17 is installed correct.

I have not used it to measure DC on a drive circuit. is this where the meter would have be in line with the circuit like measure amperage?

https://www.vellemanusa.com/downloads/1/dvm850blgbnlfresdpl.pdf

 

[Perry Babin]

You have been measuring DC on the drive circuit.

Do you have another amp that you could check your meter on?

 

[86boy]

ohhh i see.

yes I have another amplifier that seems to be the same era as this one, and was working the last time I powered it up.

 

[86boy]

oh dang they are way low on voltage compared to this other amp.

Q19
1 - 5.75
2 - 5.5
3 - 0

Q21
1 - 5.75
2 - 5.5
3 - 12.9

Q17
1 - 5.5
2 - 5.5
3 - 0

Q20
1 - 5.75
2 - 5.5
3 - 12.5

 

[Perry Babin]

At least we know it's not the meter.

Post the DC voltage on all pins of the SG3526. Copy and paste the following into your reply.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 17:
Pin 18:

 

[86boy]

SG3526

Pin 1: 4.93
Pin 2: 0.9
Pin 3: 2.75
Pin 4: 4.63
Pin 5: 4.25
Pin 6: 0
Pin 7: 0
Pin 8: 4.36
Pin 9: 3.2
Pin 10: 1.93
Pin 11: 0
Pin 12: 4.78
Pin 13: 3.55
Pin 14: 12.65
Pin 15: 0
Pin 16: 3.63
Pin 17: 12.8
Pin 18:4.99

 

[Perry Babin]

Connect a jumper from pin 18 to pin 3.

Does the voltage on pin 18 remain unchanged?

Does the gate voltage increase to about 5v?

 

[86boy]

pin 18 dropped in voltage to ~4.15

gate voltage was at 5.50v initially, but slowly dropped off to 3.5v after 20 seconds. I'm at a loss with this one. Could this be a damaged part from my mistake with installing Q17 backwards by chance? I ordered an extra set of IRF3205s just in case I did something dumb. Doesn't seem like they are bad, but I'm unsure how it would respond if it was just partially damaged.

 

[Perry Babin]

The problem appears to be with the IC. How are your soldering skils? I'd like you to desolder the IC so you could lift pin 3 and reinstall the IC (pin 3 not soldered back into the board).

 

[86boy]

ok done.

 

[Perry Babin]

Has the voltage on the lifted pin 3 gone higher and allowed the gate voltage to go to about 5v?

 

[86boy]

Pin 3 had 4.22v and stayed there. Gate voltage started at 5.6v and then dropped to 2.5v slowly. Then it started bouncing around from 0.5v to 4.5v randomly.