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Apple IIe power supply voltages

T

Traindriver69

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Joined
Nov 2, 2015
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14
Hi all
I have just got hold of a Apple iie computer that is working but on checking the power supply voltage at the connector to the board on the +12v I am getting 13.7v on switch on which then settles down to 13v is this too high.the other voltages are not too far out +5v is 5.45v -5v is 5.15v and -12v 11.96v.
I have been after one for ages so don't won't to damage something on the board.
Many thanks
 
The +5V @ +5.45V seems way too high. TTL usually is rated 5V +/- 0.25V (4.75V - 5.25V). I just got a IIe Platinum that I have to troubleshoot. The power supply is going into shutdown. The voltages are ok when the supply isn't plugged into the motherboard.
 
I have today swapped the capacitors on the power supply to see if that would make a difference.
But no change anyone any idea what to try next.
 
Yep, +5.25V is the recommended upper level for TTL devices.

I suppose the first question is "are you using a calibrated multimeter to read the voltage or not" i.e. how do you know that what you are reading is what the voltage actually is?

Under what load conditions are you testing the PSU?

I would go for +/- 5% of the nominal voltage on all of the power rails myself.

Dave
 
Hi
I am using a bog standard digital multimeter and no load just taking the readings straight from the power plug connector that goes into the motherboard.
 
Is the PSU actually plugged into the motherboard or not?

I assume "no load" means it is not plugged into the motherboard?

If this is the case, switch-mode power supplies generally do not like a no load condition. You would need to give the PSU a dummy load on each of the supply rails and remeasure.

Dave
 
Last edited:
Hi all
I found a interesting video on YouTube by adrians digital basement where he was trying a power supply in a Apple IIe and took readings from capacitors on the board to check the voltages.
I have done the same today and On C9 he got 5.09v I got 5.07v on C12 he got 12.069v I got 12.70v on C17 he got -5.09v I got -5.22v and On C15 he got 12.022v I got -12.47v.
Does this look ok.
Many thanks
 
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