A vintage Spectroline EPROM eraser

Prologue

In a previous post, I took apart and inspected a “Kalea Informatique” UV EPROM eraser that I’d purchased through Amazon. Long story short, the unit in question was discarded as completely unsafe.

Which meant that I was still in the market for an EPROM eraser.

Through eBay, I found a local seller of a Spectroline PE-14T/F “EPROM erasing ultraviolet lamp”. The unit looked comfortingly outmoded and sturdy so I went for it, and ended up striking a deal on a lot with another industrial grade (Siemens branded) EPROM eraser, plus a stash of Simatic S5 EPROM modules. (I have no real use for those PLC modules but thought they were interesting enough and I might always strip the EPROMs or other parts from them.)

In this post, we’ll have a look at what’s inside this Spectroline eraser and make sure it is not as hazardous as my previous purchase. (And in a later post, of course, we’ll look at the Siemens eraser as well.)

Inspection

Here’s a first look at the unit. It consists of two interlocking pieces of extruded aluminium; the upper one being the main housing and the lower one housing the drawer into which EPROMs are placed.

I don’t know exactly when it was manufactured, but I found a mention of what sounds like maybe a later model (PE-24T) in a 1979 issue of Hobby Computer Handbook. (Spectroline is still in business, it seems.)

There’s a facility management label on it, however, indicating it was put in use 1983 in a company in this region. Venerable.

If anyone knows more about the history of this particular model, do share.

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In one end, there’s a drawer with a little window in it (a nice and simple mechanism for giving visual feedback that the UV lamp is, in fact, on).

And the main power switch as well. (White ON, Red OFF - somehow opposite of what I expected.)

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In the other end, a (loud! :D) mechanical timer sets the exposure time. You need to have both the main power switch on and turn the timer for the UV tube to light up.

There’s a little bit of lash in the mechanism and the markings are very faded, so precision intervals can hardly be set. But is hardly needed either. A quick (well, OK, slow) test confirmed that a full 360° turn ticks away for an hour, to within a couple of minutes precision. Plenty fine for my intended usage.

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Apparently, “Re-lamp” is a word. But literally, here is an invitation to take the unit apart, so let’s obligue. :)

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Opening up one end of the unit, where the mains power enters. The mechanical timer takes up most of the space here.

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Removing the EPROM drawer.

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Opening up the other end of the unit, where the power switch sits.

I believe the blocky thing behind the power switch is an inductive ballast and/or starter, but laziness got the better of me and I didn’t actually dig it out for further inspection.

Also visible is one end of the socket for the UV tube, rated for 250V and 75W.

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Inside the drawer housing a safety feature is revealed: a switch that cuts out the UV lamp if the drawer is opened.

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Unlike the highly questionable EPROM eraser product I described in that previous post, this product has a reflector behind the UV tube, directing all the emitted UV energy down towards the EPROMs exposed below the tube.

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A closer look at that safely switch preventing the UV tube to light when the drawer is open.

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For all you tube afficionados out there. The Spectronics BLE-2537S UV tube. These still regularly appear on the evil bay and compatible tubes (such as this) are also still produced.

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Below the knob, the shaft of the mechanical timer.

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Another angle on the switch, ballast, tube section.

The cabling inside the unit is strong and sturdy; no visible wear, nicks, exposed threads or anything like that.

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A slide-on lid closes off the space above the mechanical timer. It slides out easily, giving access to the terminals on the timer.

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Here’s one small issue that needs fixing - the mains cable has slid out of the strain relief where it enters the casing.

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The crimps on these cable shoe are still strong and good. Likewise, the screws holding the cable shoe to the timer terminals did not need any additional tightening.

This is an area of the unit to keep an eye on; were those cables to somehow come loose and touch the case, the whole case could be live!

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A close up of the under side of the timer. It’s rated for 240V and 15 (!) amps.

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Most probably, this unit would originally have had a polarized/earthed mains power connector on it; at least it should have, given the metal case and mains carrying cable shoe that if they were to come loose and might in an unlucky scenario really ruin your day.

But that has been defeated at some point. In these parts, most older buildings (including where I live) don’t route protective earth to the mains sockets and sockets are unpolarized - however, all mains panels are required by law to have a central RCD/GFCI breaker, so that is not as insane as it might sound.

Still, the RCD should be a last ditch life saving measure and since I have had PE routed specifically to the main sockets in my little lab, I am going to revert this to a polarized and earthed plug for sure.

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Cleaning off the reflector and tube. Not really needing it badly, but for good measure now that I’m in here.

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Fixing the strain relief.

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There, much better.

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Removing the old unpolarized plug.

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Huh, haven’t seen something like this before. Apart from the live, neutral and protective earth leads, the cable has 3 thick (!) strings of some fibrous natural material intertwined. Must be give the cable some specific physical properties or somehow strengthen it.

The cable itself is fine and healthy, no need to replace that.

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There. Live, Protective Earth and Neutral.

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And a sanity check that PE on the new plug actually connects to the metal case.

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Done!

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Well, that was it. I am now satisfied that the device is in good order electrically and safe to use.

And it still works as well. :)

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(Now, where did I put those EPROMs…)