Solartron AS1164.2 Power Supply

[Dylan85]

This is going to be a bit of a long shot but here goes:-

Having recently overhauled a vintage Solartron AS1164.2 power supply, I have been very pleased with its performance and have been making good use of it for various projects. What a great old workhorse it is despite its age.

However, yesterday whilst using it to power a fluctuating load, the left hand ammeter stuck at around the 200mA mark. Now this particular ammeter hasn't been mechanically zeroing of late and I don't know if that may be a clue. Despite gentle knocks / taps to the front panel or ammeter bezel, the pointer refuses to budge and seems well stuck.

There is a possibility that some dust or crud has got inside and jammed the suspension and it may be possible to carefully dismantle and clean it out. I have to say though that my record as an instrument mechanic is not entirely unblemished.

However, as this ammeter has never (since I've owned it) given a very accurate reading or zeroed correctly, I suspect it may be more serious and possibly terminal.

So, now to the big ask - Does anyone have a scrap Solartron AS1164.2 that could be a donor for a working ammeter? I know it is a big ask but it would be a great shame not to get this power supply back to full working order.
Obviously, all costs of packing / postage will be paid.

Picture of the power supply below.

Ever hopeful,

Dylan

[cmjones01]

I've got an AS1164.2 as well and the meters seem to be, frankly, a bit rubbish. The 'glass' is loose on both of mine, but even when I shuffle it clear of the pointer, they're prone to sticking and giving rather random readings. They're more of a qualitative indicator of current flow than a measuring instrument! The dodgy contacts on the 'external meter' sockets on the back of the unit don't help either.

I know this probably doesn't help much, but at least you're not the only one...

Chris

[Dylan85]

Hi Chris, yes, mine had the loose glasses as well but that was easily fixed with a thin bead of silicon. I'm not sure I'd call the meters rubbish exactly but having said that I wouldn't use them for definitive current measurements either.

Anyway, last night I thought I've got nothing to lose, so removed the dodgy meter, removed the front bezel and scale and put it under the magnifier for a good look.
Imagine my surprise when I spotted what looked like a small offcut of thin wire in the airgap that the meter coil swings through. Luckily it was just about in reach for a pair of thin tweezers to grasp and once removed it seemed to be a piece of broken hairspring. It was definately flat and roughly the same width as those used in the meter itself. I gave the insides a good visual going over but as far as I could tell the two hairsprings at the top and bottom of the meter movement appeared to be ok, so where this odd piece had come from I've no idea. Maybe when I had the meter apart to secure the glass, something got in?
Once I'd got the meter back together I fired up the power supply with both meters in series and lo and behold both meters read the same within a small margin and what had been the faulty meter was no longer sticking - result.

What a stroke of luck, if that piece of broken wire / spring had been at the bottom of the meter cavity, access would not have been possible without further dismantling. Looking at the meter internal construction it is possible to remove the moving coil assembly from the meter casing (if the varnish locked screws can be released) but the delicate mechanism is then wide open to accidental damage and the chances of making a successful repair would have been somewhat lower - for me anyway.

So, a successful nights work and the old Solartron power supply looks much better without a 'stuck' meter spoiling its looks.

Dylan