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iulianv
June 7th, 2012, 02:31 AM
Apparently at some point I'll have to deal with handling UV-EPROMs if I'm to stick to this hobby (old computers), so it's time to get informed before investing in some proper tools for that...

I've read that, under constant solar exposure, an EPROM might take a few weeks to get erased - this brings up dumb question #1: will a lens focus UV rays as well, and thus shorten this time? Or will it melt the EPROM die long before erasing it?

The only source of UV-EPROM erasers I've found locally so far has some Chinese devices for the equivalent of ~40 dollars each (room for eight EPROMs in the drawer, advertised erasing time of 10 to 60 minutes, ON/OFF + switch for six intermediary steps (of what?), no manual); since I don't usually trust Chinese electronics in terms of reliability, more questions follow: how to I test that an EPROM has been fully erased? just dump its contents into a file and see that it's all ones? what can go wrong if the eraser malfunctions? no erasure at all or some sort of "over-burning"?

After erasing, can the chip be programmed like a flash / EEPROM memory (place it in a mainboard and UNIFLASH it, for example), or do you absolutely need a programmer?

Thanks in advance for taking the time to answer these (potentially answered before) questions... unfortunately I cannot guarantee that these are all the questions I have on the subject, so more may come in the future :).

modem7
June 7th, 2012, 04:04 AM
+ switch for six intermediary steps (of what?),
It may be a crude timer (turn off UV lamp after X minutes).


since I don't usually trust Chinese electronics in terms of reliability,
My cheap Chinese eraser survived the overseas trip and apart from an unreliable timer, has worked great.


how to I test that an EPROM has been fully erased? just dump its contents into a file and see that it's all zeroes?
You'll see all FF's. Software supplied with an EPROM programmer usually have a 'see if EPROM is blank/erased' check that you can perform.


After erasing, can the chip be programmed like a flash / EEPROM memory (place it in a mainboard and UNIFLASH it, for example), or do you absolutely need a programmer?
You need a programmer.

modem7
June 7th, 2012, 04:08 AM
what can go wrong if the eraser malfunctions? no erasure at all or some sort of "over-burning"?
Some good information about EPROM erasure, including the effects of overexposure, is at http://wiki.xtronics.com/index.php/How_EPROMS_Work

kyeakel
June 7th, 2012, 04:09 AM
It usually takes quite some time to erase a uveprom via sunlight. In any case it probably won't erase all locations. The cheap Chinese erasers work, I have one. There is little electronics in them, mine is just a mechanical timer/switch wired to a uv bulb. The programmer that you would use to program the chip would have a blank check button. I have several programmers as some will do chips that others will not. If you wanted to program the old 2704, 2708 type EPROMs I look on eBay for an old standalone programmer. If your doing newer stuff there are many Chinese choices that work. The Willem programmers work as well. The only boards I am aware of that allow programming in the computer are S100 boards that use the older EPROMs, for instance Cromemco Bytesaver boards.
Good luck,
Kipp

carlsson
June 7th, 2012, 04:15 AM
+1 on the cheap Chinese eraser. The only thing that worries me is the rather slender power cable that is good for up to 240V, but then again all Chinese stuff comes with those power cables and so far I didn't see any fire from overheating.

Also it should be said that for old EPROMs, they might not be reliably programmable even after a full cycle of erasing. Recently I've found a handful of my chips won't take programming anymore, even tried two different programmers while other, identical chips still work in the same setup.

Stone
June 7th, 2012, 05:00 AM
I've got 15 or 20 2732s with a few 2764s mixed in if you're interested in them.

Old Thrashbarg
June 7th, 2012, 05:33 AM
The only thing that worries me is the rather slender power cable that is good for up to 240V, but then again all Chinese stuff comes with those power cables and so far I didn't see any fire from overheating.

That's nothing to worry about, it's the current that causes overheating in wires... and there's very little current being passed in one of those things, it's just a <10W bulb with a timer switch. Even 30 or 32 gauge wire would be more than plenty for that, and those cheap power cords are usually somewhere around 22 gauge.

Before buying one of those Chinese erasers, though, it may be a good idea to look through the eBay listings for old units... I have a mid-late '70s Logical Devices eraser that I snagged for about the same price as one of the cheapy units, but it's all metal and will do a couple dozen chips at a shot, plus it takes a standard 6W T5 germicidal fluorescent tube. Such things seem to come up for sale semi-frequently.

iulianv
June 7th, 2012, 05:42 AM
My "short-term" interest is testing this TD60C board that I received without the BIOS chip and for which I found a couple of BIOS images on some Russian sites:

http://oldcomputers.livejournal.com/1151.html

So far the only re-programmable 512K DIP-28 chip I know of that doesn't involve UV-erasing (but still requires a programmer I think, it's not flash) is Winbond W27C512, therefore it seems that I have no choice but to chase an EPROM chip, an UV-eraser and a programmer, or someone to do all that for me (locally if possible, half-planet distances seem too much of a trouble for such a small task, especially if the board eventually turns out to be defective)...

Neon_WA
June 7th, 2012, 05:59 AM
Before buying one of those Chinese erasers, though, it may be a good idea to look through the eBay listings for old units...
Biggest issue I found there was most of them were only 110V units... very few were dual voltage 110/240V
not sure what voltage is in Romania

as for eProm erasing time... most eprom datasheet lists what period to use

Chuck(G)
June 7th, 2012, 07:33 AM
If Romania is 220V (I believe it is), a simple travel adapter will work just fine.

Know a barber who uses a germicidal lamp? Those will erase EPROMs just fine.

iulianv
June 7th, 2012, 08:40 AM
Yes, it's 220V here; the UV-eraser I found is this one - in case the photos ring any bells, I'm happy to hear about other people's experiences with the device:

http://www.okazii.ro/electronice-altele/stergator-eprom-cu-uv-a111978319

Very useful that xtronics.com page, answered most of my questions...

kyeakel
June 7th, 2012, 10:12 AM
Yes, it's 220V here; the UV-eraser I found is this one - in case the photos ring any bells, I'm happy to hear about other people's experiences with the device:

http://www.okazii.ro/electronice-altele/stergator-eprom-cu-uv-a111978319

Very useful that xtronics.com page, answered most of my questions...

It's the same one I have, works fine.
Kipp

MikeS
June 7th, 2012, 11:50 AM
Don't forget about non-volatile SRAM like the Dallas and Ramtron parts; a little more expensive and unfortunately the larger sizes aren't available in pin-compatible DIP packages, but for the <128kB sizes they can be convenient; no erasing necessary, no special programmers or software, just lift a pin and add a jumper to allow writing in a ROM socket (if necessary) and read and write just like a regular static RAM chip.

SpidersWeb
June 7th, 2012, 12:19 PM
I use an ultra cheap chinese UV eraser as well. Mine took longer than advertised to clear the chips but it still works well. I can throw 5 or so in, go do something else for 20 or so minutes, come back and they're all cleared.

I also use one of those cheap Willem style chinese EPROM writers. First thing I noticed is they said the default Vpp (programming voltage) was 12V - it wasn't - it was set to something like 5.6V - and there is a small screw (jewellers screwdriver stuff) you have to rotate until Vpp comes up to an appropriate value - once set it writes perfectly.

I found with older chips, e.g. used 2764's that despite the programming voltage being correct they still wouldn't write completely - they'd undershoot. So if FF is blank, and I'm writing A1 I'd end up with a value between A1 and FF. Good thing about undershooting is you can write again without clearing (provided it's the exact same code). The fix was to keep raising Vpp (some of my chips needed 13-14V, including an Intel with '12.5 PGM' written on it. I also had to increase the timing periods but that's to be expected.

Using that higher Vpp setting on a 27C512 would overshoot, so each time I write I restore to 12.5 then increase as necessary.

I have no idea if that was the old chips, or if it's because my board can't maintain voltage very well. Just wanted to throw that in in case someone has similar issues. I've written to quite a few 2764/27128/27256 and 27C256/27C512 now - never actually found a dead chip. Also protip - the write protect stickers for 5.25" floppies make great window covers ;)

Chuck(G)
June 7th, 2012, 12:44 PM
Some cheap programmers omit consideration of the programming current. For example, the datasheet for that 2764A says that Vpp is indeed 12.5V, but a max of 30 ma.. That's quite a bit of current--newer chips require less, of course, but if you observe Vpp during a programming pulse, odds are that it's sagging.

SpidersWeb
June 7th, 2012, 02:00 PM
Cheers for that, I had a feeling that might be the case. Get what you pay for I guess :)

iulianv
June 7th, 2012, 09:59 PM
Would the lamp in an UV-eraser "wear out" at some point, so that you have to replace it? Or does it theoretically last "forever" (or at least for an occasional hobbyist's lifetime :))?

modem7
June 7th, 2012, 10:48 PM
Would the lamp in an UV-eraser "wear out" at some point, so that you have to replace it? Or does it theoretically last "forever" (or at least for an occasional hobbyist's lifetime :))?
When I looked inside my cheap Chinese unit years ago, I saw a tube that looked like the ones shown at
http://www.oklahomaselltoday.com/Sapulpa-/New-541002-5PCS-uv-ultra-violet-fluorescent-tube-lamp.do

I remember seeing a filament, and thinking to myself, one day that filament might break when I switch the unit on (just like what happens to incandescent light globes).

k2x4b524[
June 7th, 2012, 11:08 PM
I use a Jelight CHIPhERASER Model 10, holds 12 IC's, uses a germicidal bulb. Advertised as needing 10 minutes to erase chips, i let it run for an hour though, to make sure.
110-220VAC
50/60 Hz
0.158 A

Bought it ar Fry's electronics about 2 years ago.

This is the model 20, mine is similar, no dial, and half the size

http://www.ebay.com/itm/JELITE-CHIPhERASER-MODEL-20-ULTRAVIOLET-EPROM-ERASER-GOOD-CONDITION-/360453145167?pt=LH_DefaultDomain_0&hash=item53ecae824f

Ole Juul
June 7th, 2012, 11:16 PM
When I looked inside my cheap Chinese unit years ago, I saw a tube that looked like the ones shown at
http://www.oklahomaselltoday.com/Sapulpa-/New-541002-5PCS-uv-ultra-violet-fluorescent-tube-lamp.do

I remember seeing a filament, and thinking to myself, one day that filament might break when I switch the unit on (just like what happens to incandescent light globes).
That looks like a pretty standard germicidal, (like G4T5) which are essentially fluorescent except without the coating. The filament is only for heating so I bet it will outlast the rest of the tube. They are generally advertised as 6,000 average rated hours, but you should be able to use it much longer than that in actual practice.

Chuck(G)
June 8th, 2012, 12:18 AM
Those lamps also have a quartz/silica envelope. Ordinary lime glass doesn't do very well for passing UVA. After over 20 years, I'm still on my first one.

That's why, in a pinch, if you know a barber with a germicidal cabinet for keeping combs, etc. you can ask to stash a couple of UVEPROMs in it for erasing.

Old clothes dryer "ozone lamps" also used to be popular for DIY erasers, but they haven't been seen in many years on new appliances.