EMT 244 PSU replacement

I just received an EMT 244 from a good friend as a gift...nice right?

The original regulator board had burned up beyond repair, and so he had rigged up an external switchmode supply.. sadly the shippers he gave it to to pack and ship to me said that they couldn't box up the supply, so they SNIPPED it out.. pure genius. The previous owner said that the unit worked when he powered it up, so I am excited to get a new supply in there to get it running. Looking over the schematics (see below), I would like to determine the 5V supply rating.. it's got two 3055s paralleled, (wasn't 15A enough?) and the fuse on the 5vac winding is 8A .

I have been looking at this: (+5VDC/5A, +15V/2A and -15VDC/0.5A) supply as a possible drop in replacement though the -15v leg may be a bit current shy..

Any suggestions?

zmix said:

wasn't 15A enough?

Click to expand...

due to larger voltage drop across 3055 it heats up much more than 3055 on 15V regulator (it has bigger dissipation), there is pretty common thing to use two transistors in paralel, so there is less stress on christal in transistor, and it heats up much less, so temperature drift in milder.

unfortunetly, I can't help You with current otput. it is obvious that circuit incorpoates rather complex folback current limiting scheme. I can tell you that there is measuring shunt for 8A, but, that value of output current s decreased with some factor determined by folback network.

regards, Ivica

Hi Chuck,
If I were in your situation I would not buy the power supply you suggest.
For the digital section I would buy a SMPS of 5V/15 amps, with S/C and overvoltage protection, and a low output noise (RF) level.
For the analog section I would buy a good quality linear power supply of +/- 15V and 1,5 amp minimum, i.e a Power-One module.
I have some experience with this EMT series of 244, 245, 246, (even 250!) and they can be tricky to fix...
Cheers,
Guy

Thanks for the input...  I've been thinking more about a switchmode / Linear combo for this thing, or even just rebiulding the existing supply, after all I have he transformer, 3055s and heatsink already mounted...

Hello,anyone has any schematics of this beast?!

Best,
Mattia.