EMRFD Message Archive 1931

Message Date From Subject
1931 2008-08-12 22:03:27 wb7dmx I need help with this
I have a MA-D5 multimeter that is not working right and I really
would like to fix it.
I have the user manual and the service manual, but they are all in
the problem is in the power supply -15 volt circuit.
I am measureing only -6.2 volts at U4.

the regulator circuit uses the op-amp V38, and the npn xistor V39
which is a bc 237c, I pulled it out and it checks good.
that leaves the op-amp which is a ua308 tc,

I just don't understand how this circuit works.
all the other voltages are good

the voltage from V33 is -18 volts
I will post a image of the power supply circuit for referance.

any help would be appreaeated


PS/ I know this is off topic but I did not have any other ideas.