LC PSU Board inside an Apple IIe PSU (Power Supply)

[uniserver]

Retrofited an LC-PSU Board into an Apple IIe Power Supply

the only catch is no -12 vdc, LC PSU does not provide it.

Well it works, the color of wires already matched up, kind of apple to keep standards across the products.

As you can see from the picture, the LC-Board is much smaller then oem board.

Glue'd the " N " key back on, and found a "zero" key on a junk adb keyboard.

looks like this beater IIe might be back in service,

I just hope the LC-PSU board doesn't make more heat then what the current enclosure is designed to naturally disperse.

 

[techknight]

Whats wrong with the original PSU? those things appear fully serviceable.

 

[uniserver]

I could not get the switching transistor to fire.

I tried everything.

The only thing i can think of is the Step down Transformer is bad some how.

I even changed the the switching transistor, and the caps that give it a Kick start.

Started racking up the hours on it and said the heck with it...

and those god dam HV Caps do not have a discharge resistor, so I had to keep discharging them by hand.

pain in the butt.

Works now.

Charles

 

[uniserver]

for reverence here is where the power wires hook to on a stock IIe PSU board.

 

[techknight]

I could not get the switching transistor to fire.
I tried everything.

The only thing i can think of is the Step down Transformer is bad some how.

I even changed the the switching transistor, and the caps that give it a Kick start.

Started racking up the hours on it and said the heck with it...

and those god dam HV Caps do not have a discharge resistor, so I had to keep discharging them by hand.

pain in the butt.

Works now.

Charles

I doubt the transformer is bad. Possible, but i doubt it. Did you check the film caps? ive seen those fail and cause that exact thing. Also you check the soft-start resistor? because a feedback oscillated flyback power supply requires a few things to be right before it will oscillate.

 

[James1095]

I've never seen a bad transformer in a switchmode power supply, ever. I also find that usually when I start to suspect a hard to find/exotic/expensive component, the actual fault turns out to be something simple.

IIRC the IIe supplies are self-oscillating converters where a resistor provides bias to turn on the transistor, which is then turned back off by a pulse from a feedback winding. If the resistor is bad or out of spec, the transistor won't turn on and the thing won't start oscillating. If you have voltage on the bulk filter capacitors (large electrolytics on the input) look around for a resistor that has ~320V across it and test that out of circuit.

I think the LC PSU is a bit under spec for a IIe. It may work fine with an empty machine but stick a few cards in there and it'll really be straining. IIRC the original IIe supply is close to 70W and the LC supply is about half that.

 

[uniserver]

yeah the bigger resister right near the transistor was the first thing I changed,

the old one had a slight smoky look about it, as with the film caps.

You are right i'v also never seen a transformer like that go bad.

also you are correct it probably is something simple.

some little thing i may have over looked.

Ok ( not that it matters ) because the LC PSU Board was not made for this wattage / voltage application.

/w 80 column card installed, Super Serial, Disk drive card and one disk drive... it work's, I'v not ran it through and amp meter to see what the actual draw is, but the power supply is driving the cards so far, and does not seem to be making an extra ordinary amount of heat.

the super serial card is just installed, I did not hook anything up to it, my concern is that, its not going to work with out the -12v rail.

 

[James1095]

You'll probably be fine as long as you stick to simpler/newer peripherals. Some of the old RAM cards were real power hogs, particularly those that used a big pile of early generation low capacity power hungry chips.

 

[LCGuy]

My Platinum IIe runs an external AT PSU from an old PC. Uglier than sin, yes, but I never have to worry about it not having enough oomph to run the machine.