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Re: Telestrat failure?

Posted: Wed Jun 19, 2019 11:55 pm
by RetroTechie
mikeb wrote:The same applies for OTP (One Time Programmable) chips where you program them, once, by blowing fuses away.
In the case of memory, such fuse-programmable chips are normally referred to as PROM. Such as the TBP24S10 used in the Oric's video circuit. PAL programmable logic is also fuse-based. Rarely seen these days, but quite reliable indeed. There even exist some FPGA's using a fuse-based technology :o for their (one-time!) configuration (Actel, Lattice or MicroSemi iirc).

What's normally referred to as One Time Programmable isn't fuse based but just 'UV' EPROMs in (cheaper!) plastic housing. So after programming you can't erase them since there's no window to shine UV light through. But same chip inside (same type # too), with all (dis)advantages that come with UV EPROMs. Still commonly found where programmed data isn't expected to be updated in the field. For example as video BIOS on older VGA cards.
27C256_OTP.jpg
27C256_OTP.jpg (8.33 KiB) Viewed 632 times
I still have an EPROM eraser, and a self-built EPROM programmer which I'm not sure if it still works (does/did 27(C)64 up to 27C040. 27C080 support would be easy to add). I intend to write a small program some time, that will read & count the # of 0's and 1's in an EPROM, put in one with all 0's programmed, put it under a hood together with an EPROM erase lamp, and then produce a nice graphical representation as you see the bits being erased (from 0 to 1). Should make for a nice live demo or YouTube video. 8)

Re: Telestrat failure?

Posted: Thu Jun 20, 2019 4:46 pm
by mikeb
Sounds like a cool project, but also -- I wonder if erasing these chips can be "optimized" using that technique, like the reverse of the programming strategy I mentioned:

Fast Erase: Put UVEPROM under UV light and read it continuously until it returns all 1's, time how long that takes, then give it X% extra time cooking, before declaring it done! :)

Your point on OTP EPROMS is noted (a UVEPROM in plastic clothing), I was indeed talking about PROMS when I mentioned fuse-blowing.

Re: Telestrat failure?

Posted: Mon Jun 24, 2019 6:08 pm
by Symoon
Just for the record, I have tested all my Hyper-Basic cartridges. Six of them: all are dead :shock: :shock: :shock: .
They were sotred in a (dark and dry) cupboard in my room.

I tested them on the Telestrat that was checked in detail by NightBird 10 days ago (power, motherboard and so on), and this machine worked fine when we ran it with a (recently made) cartridge that René lent us.

So I wonder: am I the only one experiencing heavy problems with original cartridges right now?

Re: Telestrat failure?

Posted: Mon Jun 24, 2019 7:24 pm
by Chema
That is indeed bad luck, Symoon. When was the last time you tested them? Maybe they reached the end of their probable lifetime in the last, say, 5 years...

Re: Telestrat failure?

Posted: Mon Jun 24, 2019 7:48 pm
by Symoon
Chema wrote:
Mon Jun 24, 2019 7:24 pm
That is indeed bad luck, Symoon. When was the last time you tested them? Maybe they reached the end of their probable lifetime in the last, say, 5 years...
That's possible. Last time I tested was around 2009 I think (spare time... :-/ )
Also, 2 or 3 of them might have been faulty before: they were given to me by the guy that sold the machines, and I think I had never tested them all.

but if they all failed in the past 5 years for instance, that means most of them anywhere might do as well... :shock:

Re: Telestrat failure?

Posted: Wed Jul 10, 2019 2:09 am
by NekoNoNiaow
mikeb wrote:
Wed Jun 19, 2019 5:04 pm
RetroTechie wrote:
Wed Jun 19, 2019 2:04 am
Depends. Mask ROMs are extremely reliable
Very true, and the clue is in the name.

Unlike UVEPROMS, Flash-ROMS (analogue storage, see above), Mask ROMS are not programmed as such, but the data is put there at time of manufacturer by including, or not including, metal/silicon bits of the chip design to encode the 0's and 1's, so they are very much binary/digital, and are reliable because of that.
Very true but that does not protect them from the case "my dog ate it while I was not looking and pooped it somewhere I never found". :D
Always dump ROMs before your dog does. :lol:

Re: Telestrat failure?

Posted: Wed Jul 10, 2019 5:03 pm
by mikeb
Yes, well, obviously the dog is going to come off worse for that encounter ... ever trod on a DIP IC? Barefoot? I can't see the dog enjoying it on the way in. On the way out will be worse ...

Meanwhile, another "risk" -- I found two spare Oric V1.1 Basic ROMs and ULAs, carefully preserved in antistatic foam.

For the first time ever, I discovered a brand of a/s foam that turned to mush with age. I don't know if it's still conductive, but it is black, sticky and an absolute mess to remove from the chip, fingers, everything it touches :(

I've known old (foamed rubber) foams to dry up and turn to dust, or go sticky, but never anti-static foam. Ugh. Watch out for that one -- I hope not to find any more :)

Re: Telestrat failure?

Posted: Mon Jul 29, 2019 10:52 pm
by RetroTechie
mikeb wrote:... ever trod on a DIP IC? Barefoot?
PROUD to say that once, I have, and barefoot indeed! :lol: Iirc a small DIP like TL072 opamp or such. Pins upwards ofcourse thx to Murphy.
I discovered a brand of a/s foam that turned to mush with age.
Learned that as well not too long ago. Not due to using such foam myself, but due to the effect it had on some IC's bought on eBay. Looked exactly like what you'd get from unsoldering an IC while adding some flux & burning that. Thus made "New Old Stock" IC's look like unsoldered ones. @ First I thought that seller's excuse was BS, but some research learned this is actually a thing.

Afaik the kind of antistatic foam susceptible to this, is the softer (more foam-like) type that looks similar to the self-adhesive foam used inside old radio's etc to stop wires, plastic sheets etc from hanging loose or vibrating. Dump that crap if you have any! :evil: The 'harder' type of antistatic foam just gets brittle & tends to crumble over time (+ repeated insertion/removal of IC's).