IBM 5110 transformer?

Paul Berger phb.hfx at
Mon Sep 30 09:46:17 CDT 2019

On 2019-09-30 3:44 a.m., Mattis Lind via cctalk wrote:
> A friend of mine is trying to repair a IBM 5110. He is convinced that the
> transformer is bad.
> Anyone knows the spec of the transformer?
> Someone that has a spare?
> Looking into the tech documentation tell me that the machine requires +/-
> 5V and +/- 12 V and also +8.5V
> A very rough guesstimate based on the number of wires from the PSU to the
> backplane would give 20A 5V, 4A +12V, 4A +8.5V, 1A -5V and 1A -12V.
> Anyone with a better guess?
> /Mattis

Does this transformer has a resonant capacitor on it?  They where very 
common on IBM power supplies from that time period and if the capacitor 
goes short you will not get any output from the transformer.  This is a 
lesson I learned as a green service rep 40 years ago after lugging in a 
very heavy transformer for a machine.


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