De Vere Voltage stabilizer repair

The De Vere branded 1.5 Kilowatt voltage stabilizer which accompanies my De Vere 108 Dichroic head

enlarger is not functioning. I am blowing a lot of enlarger bulbs(ELH 300 watt x 4), and the wise old owner

of my local lab has told me the bulbs are blowing as a direct consequence of the failure of the voltage

stabilizer. Given that I live on a small Island to the west of the UK, and that it's hard to get used darkroom

equipment, or to find anyone with specialist mechanical knowledge of enlargers in these parts, where

would one go to get a voltage stabilizer fixed? Some sort of electrical repair shop? An Electrician? I've no

idea where to start, but given that my local photo store is charging 20 euro per bulb, I think a little effort

to resolve the source of the problem might be worth the trouble.

Alternatively, is there some obvious things to check if I open it up myself? The stabilizer does relay current

through to the enlarger head which is connected to the power source via the stabilizer, although the little

needle meter indicator which used to be animated upon power up, now sits inert no matter whether

there's power or not.

A good electronics repairman should be able to make it well by checking it component by component. It probably isn't that complicated, at most it has a photo-sensor in the head and regulates light output, instead of just regulating voltage. If there is a photo sensor in the head, make sure it isn't obscured by dust...

If there's no photo-sensor, you just need a regulated DC power supply that puts out the 120 volts that the bulb expects, at the 3 amps of current that it needs.

Voltage stabilizer/regulator circuity is not that complicated. A good electronics repair person that services home entertainment electronics or radio communications equipement should be able to fix any problem except those which require non existant parts.<br>

With unit unpluged check for loose or corroded contacts at the bulb socket, worn or frayed power or connecting cords, or loose fitting connecting cords.

John, Charles,

Thanks for the advice. Somewhere to start at least.

Best,

Gerard

It could well be the transtab causing the problems, but in the past I have found that all bulbs are not made equal.

I have a De Vere 507, which uses the ELC bulbs, and I had been using the GEC manufactured bulbs, which come in about 12GBP each (around 20 Euro). Then I tried using a variety of other manufacturers products as they were 1/2 - 2/3 the price of the GEC (good manufacturers, not just generic style, unbranded goods), but never got more than a few minutes life from them (if they didn't blow immediately).

So if you have changed the source of bulbs recently, it would be worth checking out your original source of bulbs.

Cheers

Steve

Its worth noting that halogen bulbs are very sensitive to under and over voltage. I found that my 24v ELC bulbs last well when driven at around 23.5v. Too low a voltage and the glass goes black, to high and they just blow more often.

Devere TranStabs also provide a small leakage current to the bulb when the lamp is off. I assume this is to provide some pre-heating to conserve the bulb life? I measure around 1.2v across the bulb in this state.

If you have a digital voltmeter or can borrow one it might be worth checking its working voltage?

Barry

ps Some manufacturers produce 'long life' versions of these bulbs.

Stephan, Barry,

Thanks for the advice.

Stephen, the bulbs I've been using are GEC, model ELH. Should I be using ELC bulbs as

you both are, or is there any significant difference? The manual I have, from Feb. 1984,

lists part 2016 as Dichromat Lamp ELH Patt. which in my ignorance, I presume means I

should be using ELH bulbs, but I must confess I don't know the difference.

Barry, I presume you're measurements are based on current that's passing through a

working voltage stabilizer? I suppose they would be target measurements for me after I've

had the voltage stabilizer fixed?

Best,

Gerard

<p>Hi Gerard,</p>

<p>Yes you are using the correct lamps for your head, the ELC lamps are 24V 250W types. I have been using the GEC lamps apart from a few tests with other manufacturers ELC types, and have had no trouble with them. It does now sound to me as if there is a possible problem with the transtab.</p>

<p>It might be worth contacting <a href="http://www.odyssey-sales.com/">Odyssey Sales</a> in the UK (who are the manufacturers, and distributors of De Vere equipment), who might be able to recommend someone local who could check it out.</p>

<p>All the best,</p>

<p>Steve</p>