Help, SMPS Question

[Alembic]

Re: Help, SMPS Question

Hi All.

Using a standard brushless 12v/0.12amp as a load
(not ideal I know) I register the following readings:

On load +ve output of between 19v - 22v
Off load -ve output of around 35v
On load -ve output of between 19v - 22v
Off load +ve output of around 33.9v
These readings rise and fall between those points.

I rigged a LED across the outputs to get
some kind of visual feedback and it`s pulsating.
Some components get a little warm but nowhere
near as before. Rechecked component readings,
these appear ok.

I connected it to the mixer and powered up
(very briefly) and the power and ladder leds
are "blinking". Possibly could have an issue with the
mixer but will deal with that later.
Feel I`m getting close but no coconut yet :o(

Anyone make sense of the above points?

Thank you.

[stj]

Re: Help, SMPS Question

did you replace C1 and C8 with low-esr parts and check D1 ?

[rievax_60]

Re: Help, SMPS Question

There must be something wrong between pin 1 on the transformer and pin 2 on the UC3842. check for broken tracks at the transformer pins as well as the parts mentioned above. Also measure the voltage across C8.
Check R16 and R11.

[Alembic]

Re: Help, SMPS Question

Hi.

I replaced C1-C8 (original caps Jamicon 85deg with
Chong 105deg 50v. Not sure if any of these are low-esr.

rievax_60: will recheck points you mentioned later.

Thanks.