Wanted - TRS 80 Model 1 PSU

Hi guys

Dusty M in the UK has given me a beautiful Model 1 LII 16K machine with no PSU.

Does anyone have a spare they wouldnt mind parting with please.

I know I can build a suitable unit but I would like an original unit.

Using an 18V AC (Acorn Electron) supply and an 18V DC laptop supply i find the power LED is going from bright to very dim constantly.
Measuring voltages on the main board, the +12 is 11.9 and the -5 is bang on -5.
But the +5v is non existant but judging by my DVM it is oscillating on and off.

Any Suggestions please.

Thx

not enough juice

Have tried a 19V AC 1.8Amp supply, still the same effect.
The reservoir cap C9 is not even holding any voltage across itself.

mmm

I think I found something...

Looking at the official Tandy schematic of the psu and indeed ian's redesign, the centre tap of the 18v ac transformer is grounded common to the dc psu's negative....
now my electron psu has no centre tap for me to use, and I'm sure the reason for my unstable 5v supply is due to the fact that on my setup there is no common point between the AC and the DC supply..hence the 18v AC is floating.

But what do I do, I have no centre tap to join, do I common one side of the 18v ac supply to the dc supplies negative...

Anyone pls shed some advice as I dont want to blow anything up lol.

thx

Ooops speaking to myself again lol.

That got it working
Basically grounded 1 side of the transformer to the dc 0v and all is rosy.
Checked voltages were correct before plugging though to be sure....

Nice MEM SIZE promot on screen now and she works perfectly....Thanks Dusty.

Still looking for the real mcoy chaps.