ah.. the joys of fixing switching power supplies.
I just repaired four MM700 Mighty Mites this weekend. All filter caps on the main 5v supply
read <100uF on a capacitance meter when they should have been 19000. They are very old units, a little
older than the one in the KS10. It is also common for the high voltage caps to fail. The first thing
I would check with a dead switcher are the caps. An ESR meter is extremely handy for doing this in circuit.
All four squeel at different current levels on an active load, but they quiet down at >10A. You can see the
noise level on the main output vary as you apply load.
The squeel seems to be coming from the step down transformer. I'm guessing resonance between the sheets
in the core. You can get the level to vary applying pressure to the transformer core.
Schematics are pretty much impossible to find. I spotted a manual that Tucker had listed on eBay, and that
will be scanned and up on bitsavers when it comes in. If you dig around, people have identified the pinouts
on the DB connector, but the information isn't in a single place.
I just repaired four MM700 Mighty Mites this weekend. All filter caps on the main 5v supply
read <100uF on a capacitance meter when they should have been 19000. They are very old units, a little
older than the one in the KS10. It is also common for the high voltage caps to fail. The first thing
I would check with a dead switcher are the caps. An ESR meter is extremely handy for doing this in circuit.
All four squeel at different current levels on an active load, but they quiet down at >10A. You can see the
noise level on the main output vary as you apply load.
The squeel seems to be coming from the step down transformer. I'm guessing resonance between the sheets
in the core. You can get the level to vary applying pressure to the transformer core.
Schematics are pretty much impossible to find. I spotted a manual that Tucker had listed on eBay, and that
will be scanned and up on bitsavers when it comes in. If you dig around, people have identified the pinouts
on the DB connector, but the information isn't in a single place.