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IIe power

Cinan

Well-known member
Hi,

I have experience with the Compact Mac range so IIe's are a new venture for me. I have two both enhanced, I have had one for a years and it works fine, I have just acquired another which has been in a cupboard for about 30 years.

I decided to recap the power supply before turning on. Following the recap when I turned it on it powered on for a few seconds (led lit) and the floppy made a noise and then nothing, led went out.

Upon further troubleshooting I have found the following and would appreciate any thoughts re where to look next :

1. Power coming out of power plug is 12.2 and 5.3v.
2. I have checked continuity between J20 and J14 for the power rails - all have continuity.
3. The motherboard looks perfect.
4. When I have the motherboard out of the case and apply the power source, the readings on the back of J14 and J20 only read 0.6v for the 12v rail and 0.05v for the 5v rail.
5. I have tried the motherboard with 2 power supplies with the same result.

What would be causing the power drain on the motherboard like this compared to the 12.2 and 5.3 on the power plug when not connected to the motherboard.

Any help greatly appreciated.
 

bibilit

Well-known member
Probably a shorted capacitor in the psu connector area.

The psu should have more than those two voltages
 

Cinan

Well-known member
It has the -ve equivalents also. interesting though that it gives the voltages with no load and the same motherboard has the same result with a known working PSU. According to the schematic for J14 it should have

Pin 1 - GND
Pin 2 - GND
Pin 3 - +5VDC
Pin 4 - +12VDC
Pin 5 - -12VDC
Pin 6 - -5VDC

it has all those when measuring the disconnected plug with the power turned on.
 

bibilit

Well-known member
Again pretty sure is one of the capacitors nearby causing the issue (Logic board side)

Above the connector (20 uf 16v)

Using a multimeter, in continuity mode, check all of them.
 

Cinan

Well-known member
Do you mean (C9, C12, C7, C15) and/or (C10,C13, C18, C16) on the motherboard ? I can't see these referenced on the IIe Schematic but can see them on the board ? Interestingly on the IIe Schematics son page 2 it refers to the Power on LED being connected directly to the power source via a Resistor not via a Capacitor, this LED doesn't light up on board inferring it isn't getting direct feed of Power.
 
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