Baldwin Poweramp

[nosaj]

I'm working on this Baldwin poweramp for a GPS2500 http://www.shema.ru/cd/us/2/data/ps2500.pdf
Believe I have the rails correct now.
But here is the deal I only have the poweramp board. Where could I input signal at to follow it through?

Also on the IC's Ic8 has -8.66 on pin1 Does this seem correct?

Thanks,
nosaj

[nosaj]

In the muting circuit TR1 C is -.001 B is .792 E is .007
TR2 c is 12 B is .006 and E is -.001
TR3 C is 5.53 B is 11.68 E is 11.83
TR4 C is 11.80 B is 11.06 E is 11.83v
TR5 C is .023 B is .763 E is -.001
tr15 c is .016 B is .737 E is 0
R2 has 11.8 volts at pin1

Something is pulling down the +12 regulator and not allowing the R2 to latch. Still being very Green my eyes say something is wrong with tr3 and tr4
I did pull them and they tested ok on a bk520 buuut. IDK.
nosaj

[Sowhat]

Where could I input signal at to follow it through?

At connector CN10, pins IN1 and IN2. At least that's what page 7 of the service manual shows.

IC8 are the peak detectors so pin 1 would be for peak 1 and pin 7 would be for peak 2. A TL072 dual op amp is powered by in this case +-12VDC so the voltage on pin 1 as well as pin 7 can be anywhere within that range depending on what is present on the input pins from other sources for that pair of op amps.

[nosaj]

At connector CN10, pins IN1 and IN2. At least that's what page 7 of the service manual shows.

IC8 are the peak detectors so pin 1 would be for peak 1 and pin 7 would be for peak 2. A TL072 dual op amp is powered by in this case +-12VDC so the voltage on pin 1 as well as pin 7 can be anywhere within that range depending on what is present on the input pins from other sources for that pair of op amps.

Will the peak detectors shutdown signal if there's issues?

Thanks,
nosaj

[Sowhat]

In the muting circuit TR1 C is -.001 B is .792 E is .007
TR2 c is 12 B is .006 and E is -.001
TR3 C is 5.53 B is 11.68 E is 11.83
TR4 C is 11.80 B is 11.06 E is 11.83v
TR5 C is .023 B is .763 E is -.001
tr15 c is .016 B is .737 E is 0
R2 has 11.8 volts at pin1

Something is pulling down the +12 regulator and not allowing the R2 to latch. Still being very Green my eyes say something is wrong with tr3 and tr4
I did pull them and they tested ok on a bk520 buuut. IDK.
nosaj

I have not checked if all those transistors are PNP or NPN but basically you should have .7 volts base to emitter if they are silicon crystal. Either positive or negative depending on the polarity of the transistors. I was just looking at the board layout and if you have CN11 VIDEO BOARD disconnected detaching jumpers J29 and J47 will completely isolate your +-12 volt supplies from the rest of the board. You then might trace through +-12volt board rails for shorts if your +12V is getting pulled down. Resistance reading alone on the rails can lead to the short or point of excessive current draw, maybe in an IC... like an op amp for example.

[Sowhat]

Will the peak detectors shutdown signal if there's issues?

Thanks,
nosaj

Well, maybe if I understood what the peak detectors were responsible for in the instrument. I might have an answer... they may only flash an indicator light that a peak state exists... I dunno... that's a big schematic to wade through!

[Sowhat]

detaching jumpers J29 and J47

Oops!!! I mean J38 and J40 or... J33 and J36, detaching jumpers J29 and J47 disconnects the rectifier from the regulators, that would be pointless, right?

[nosaj]

I have not checked if all those transistors are PNP or NPN but basically you should have .7 volts base to emitter if they are silicon crystal. Either positive or negative depending on the polarity of the transistors. I was just looking at the board layout and if you have CN11 VIDEO BOARD disconnected detaching jumpers J29 and J47 will completely isolate your +-12 volt supplies from the rest of the board. You then might trace through +-12volt board rails for shorts if your +12V is getting pulled down. Resistance reading alone on the rails can lead to the short or point of excessive current draw, maybe in an IC... like an op amp for example.

Ok will recheck those Transistors and disconnect j38,j40 to isolate. To be sure I'd just connect black probe to ground then starting where j38,j40 were disconnected checking points looking for contiuity? If you can give one example or explain it different once started I can probably go through the rest of it.

Thanks so much for our help,
nosaj

[nosaj]

Ok will recheck those Transistors and disconnect j38,j40 to isolate. To be sure I'd just connect black probe to ground then starting where j38,j40 were disconnected checking points looking for contiuity? If you can give one example or explain it different once started I can probably go through the rest of it.

Thanks so much for our help,
nosaj

I rechecked the voltages on the transistors they are still the same. I replaced IC8 with a new tl072 no voltage on pin1 now. i also replaced IC6 and IC9 the voltage regulators -12 is spot on. The Positive 12 volt rail is still reading low.
Still unsure of how to do the following

completely isolate your +-12 volt supplies from the rest of the board. You then might trace through +-12volt board rails for shorts if your +12V is getting pulled down. Resistance reading alone on the rails can lead to the short or point of excessive current draw, maybe in an IC... like an op amp for example.

Thanks so much,
nosaj