BA-3000 board vu meters

[Sargi]

Dear all,
I have a BA 3000 amplifier that works perfectly,
the left vu meter without signal moves randomly without input signal
the right vu meter is always at full scale
can you give me some help?
many thanks

 

[tarior]

I repaired one about 12 years ago for the late Nosirrah that had a similar problem. It was a noisy transistor in the buffer amp.

 

[Sargi]

My problem is without input signal.....

 

[tarior]

Yes. It doesn't need a signal to act up.

 

[Sargi]

Dear ,...do you mean you replaced a transistor on the meter amplifier board ?...

 

[tarior]

Dear ,...do you mean you replaced a transistor on the meter amplifier board ?...

No. The problem in the amp I was working was spurious noise being produced by a noisy transistor in the buffer amp. Which would of course show on the meter. It doesn't have to be audible noise. Not saying that this is necessarily the problem in your case, but in that case it was. Just an idea for a place to look. You'll have to apply your skills to narrow it down. It could be a noisy transistor in the meter drive, or the buffer, or in the amp itself. It could be a cracked resistor or cracked solder joint. There are a lot of things it could be.

 

[ivandezande]

Unplug the signal from the meter. If it's still pegged, start replacing transistors on the meter drive board. The IC can also die, I've seen it twice.

 

[sregor]

meter drive is AC coupled going into the last transistor - so pegged meter is most likely shorted last transistor or mechanical issue (meter stuck) Look for DC going into meter.
Noisy could be any one of the transistors or ICs (As @tarior pointed out).

 

[tarior]

meter drive is AC coupled going into the last transistor - so pegged meter is most likely shorted last transistor or mechanical issue (meter stuck) Look for DC going into meter.
Noisy could be any one of the transistors or ICs (As @tarior pointed out).

I always take for granted that they check for a stuck meter.

OP, if it is a stuck meter, it will be stuck with the power off.

 

[Sargi]

the vu-meter is not blocked...
the defect appears only when the power is turned on,
if I disconnect the input cable the defect remains,
I'll check the voltages on the board this evening.

 

[Lavane]

So, the one meter stays pegged when the amp is turned off?
I would think in that case the meter is either stuck, or failed.
Maybe someone at some point ran the amp loud enough to peg the meters and keep them pegged for a.lomg enough period to fry the meter.
I have an old Fisher receiver in my garage that has fried power meters.

 

[Sargi]

the vu-meter is not blocked.
only when I turn on the amplifier does it go full scale

 

[ivandezande]

the vu-meter is not blocked...
the defect appears only when the power is turned on,
if I disconnect the input cable the defect remains,
I'll check the voltages on the board this evening.

Means the IC or transistors died.

 

[Lavane]

Means the IC or transistors died.

Yup. It does sound like a chip or transistor shorted out then.

 

[tarior]

the vu-meter is not blocked...
the defect appears only when the power is turned on,
if I disconnect the input cable the defect remains,
I'll check the voltages on the board this evening.

Perfect. It's now narrowed down to the meter drive circuit.

 

[Sargi]

Dear all,
I replaced the two transistors TR03 now the vu-meters work perfectly.

 

[Lavane]