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EPROM burning for beginners

tezza

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When I first started to explore EPROMS to replaced failed ROMS I found it hard to get practical information that told me the basics. Hence I decided to write an article on it to help other collectors (like me) who don't have the electronics background. I've deliberately avoided being too technical. The text is for primarily for those who want to fix their computers by replacing a failed ROM. The assumption is that if people want more depth, they can Google around.

Most of the regulars here are old hands at EPROM programming. Anyway, if you spot any glaring errors, let me know.

http://www.classic-computers.org.nz/blog/2012-10-21-eproms.htm

Tez
 

RickNel

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Useful guide, Tez - thanks for posting it.

I have a USB-powered model that looks exactly like yours (different brand) but found that it was not reliable for the higher voltage burn Vccs (above 20v). Could be some issue to do with the ability of the PC to deliver enough current through its USB port within the timing requirements of the upconverter/burning circuit. Maybe not maintaining the pulse long enough? Just guessing.

Anyway I bought a Willem like the one illustrated, with external 12v supply, and it works reliably for all vcc up to 25. I looked at DIY burner schematics, but the Willem clones are available online for a lot less than the components would cost separately.

Rick
 

tezza

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Useful guide, Tez - thanks for posting it.


I have a USB-powered model that looks exactly like yours (different brand) but found that it was not reliable for the higher voltage burn Vccs (above 20v). Could be some issue to do with the ability of the PC to deliver enough current through its USB port within the timing requirements of the upconverter/burning circuit. Maybe not maintaining the pulse long enough? Just guessing.

Thanks

Rick did you try altering that pulse rate? My initial TOPS853 tryouts with +25vpp 2716 and 2732 EPROMS were not so hot either. Programming would start, but the system couldn't seem to progress past the first 250 bytes or so...and on ICs from at two different manufacturers! Having just bought the unit this was as discouraging as it was alarming. I set the pulse rate from 5ms to 1ms and all those problems disappeared. As I said in the article, 5ms was the default.

I bought the TOP when the Wellim developed a fault. For some reason 25Vpp was always active no matter what the settings! The fault was accompanied with smoke and heat. I replaced the obviously burnt out components but it didn't fix the problem. Something else was obviously zapped.

One of the problems I had with my Wellim is that it refused to burn 27C16 ICs. I never got to the bottom of that. Mind you, I haven't tried 27C16 EPROMS in this TOPS unit yet either. :)

Tez
 

Chuck(G)

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If I remember correctly, the TOP853 board does have pads on the PCB for an external power supply jack. I don't recall the details, but I briefly played with the idea of adding a jack and wall-wart.
 

RJBJR

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Good information. My Top853 came with a wrong version of the software and refused to write because Vpp wouldn't get higher than 5v. It took a week of back&forth emailing the supplier before I finally received the correct version and had success.
The link to the software is http://www.topwin6.com/Soft.html , the version 6.3 resolved my issues. There is now a version 6.34 available but I havn't tried it.

Something not mentioned in your article, an EPROM can get "cooked" and not program if you leave it under the UV light too long. Also, the UV light from the eraser can damage your eyes, so don't look directly at it when the door is open.
 

tezza

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Something not mentioned in your article, an EPROM can get "cooked" and not program if you leave it under the UV light too long. Also, the UV light from the eraser can damage your eyes, so don't look directly at it when the door is open.

Those are useful points for newbies. I'll include them. Thanks.

Tez
 

Marty

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Hi All;
I have a Needham Emp-11 programmer, and it works fine for 2732's and up.. But what I would like is something for 2708's and 2716's.. As my 2708 and 2716 (S-100 SSM PB1) works but for how much longer, as sockets are failing and I can no longer use it to Read from another area that is set up on the Board for reading Eproms.. So what would Everyone suggest for a good Eprom Programmer for 2708's and 2716's ??
THANK YOU Marty
 

Chuck(G)

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That's a tough one Marty. Back in the day I used an Intel MDS with its EPROM burner to do the job, but that's like taking a sledghammer to drive a push-pin.

The very expensive EPROM programmers (e.g. Dataman) will do the 3-rail supply EPROMs; there are some adapters available that supply the needed power for a couple of other vendors, but none is very cheap--and you still have to buy the basic programmer.

You might want to locate or fab up your own version of the Aries 18061 adapter instead.
 

tezza

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.. So what would Everyone suggest for a good Eprom Programmer for 2708's and 2716's ??
THANK YOU Marty

Marty,

I can only go from my experience in using the Willem and TOP853 as mentioned in the article, and I haven't tried either with 2708s.

Both units could read 2716s and 27C16s just fine. Both units had manuals that were hard to follow. The Willem manual didn't directly relate to the actual board layout of what I had.

I could never get my Willem to burn 27C16s. Standard 2716s were fine although it was during the burning of a 2716 that smoke erupted from a few of the components. And that was that.

The TOP853 initially had difficulty burning 2716s until I lowered the pulse rate from the default. Now it seems fine. I haven't tried 27C16s with this unit yet. The TOP853 (at least mine) seems to be able to handle 25Vpp from a USB source. The Willem needs a Wall Wart for this.

In summary they seem to cope with 2716s but (given my experiences) some "issues" may manifest themselves.

I'd be interested in what others might recommend.

Tez
 

Chuck(G)

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Careful, Tez--there are 2716s and then there are 2716s. One of the industry's major blunders with a part name.

The Intel 2716 (I2716) is a 5-volt single-rail part; the TI 2716 (TMS2716) is a 3-rail part (-5,+5 and +12 supplies). They don't even program the same way.
 

tezza

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Careful, Tez--there are 2716s and then there are 2716s. One of the industry's major blunders with a part name.

The Intel 2716 (I2716) is a 5-volt single-rail part; the TI 2716 (TMS2716) is a 3-rail part (-5,+5 and +12 supplies). They don't even program the same way.

Really? Thanks Chuck, good to know as it's an EPROM size that relates to many of these late-70s/early 80s micros. Alongside programming, these differences would need to be considered when selecting a 2716 to replace mask ROM too then. Was it just 2716s, or do 2732s have this variability also?

This just reinforces how important it is to get the specific datasheet for these chips (Assuming one can UNDERSTAND the datasheet of course).

Tez
 

Marty

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Hi All;
THANK YOU for the information.. Right now, since that is all I have, I will continue to use the SSM PB1, for now it works with both the 2708 and the 2716, three rail type.. I have worked out a system, that I have in Eprom and can serially down load from my PC to my Altair.. Chuck, You have cleared up, why I have had problems with some Intel 2716's.. I didn't know some were single voltage and some were not.. Tezza, I would suggest that be included, as well..
THANK YOU Marty
 

tezza

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I've added a paragraph to the article under the section "Programming an EPROM, (i) Some basics" which alerts readers to the Intel (and others) 2716 vrs TMS2716 differences. A good thing for people to know.

Tez
 

Chuck(G)

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Just an addendum to the google groups post you noted, Tez--TI did indeed make a TMS2732--and it was compatible (pinout and power-supply-wse) with the Intel part. All of which is something to be careful of if you're buying old parts.
 

tezza

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Just an addendum to the google groups post you noted, Tez--TI did indeed make a TMS2732--and it was compatible (pinout and power-supply-wse) with the Intel part. All of which is something to be careful of if you're buying old parts.

I've now mentioned this in the article. I've also added an acknowledgement at the end of the article to you and RJBJR for your contribution.

I can't help but wonder now whether I unwittingly burnt one of those incompatible TMS2716s in my Willem and that's what caused it to go up in smoke? It happened during a 2716 burn. I can't check right now but I'm pretty sure I have a few of those TMS2716s in the stash.

Tez
 

MikeS

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Hi All;
I have a Needham Emp-11 programmer, and it works fine for 2732's and up.. But what I would like is something for 2708's and 2716's.. As my 2708 and 2716 (S-100 SSM PB1) works but for how much longer, as sockets are failing and I can no longer use it to Read from another area that is set up on the Board for reading Eproms.. So what would Everyone suggest for a good Eprom Programmer for 2708's and 2716's ??
THANK YOU Marty
You can always insert a machined pin socket (with its slightly thicker pins) into a failing socket and use that.

Also, in most cases you can use a 2732 or 2532 instead of a 2716.
 

MikeS

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I've now mentioned this in the article. I've also added an acknowledgement at the end of the article to you and RJBJR for your contribution.

I can't help but wonder now whether I unwittingly burnt one of those incompatible TMS2716s in my Willem and that's what caused it to go up in smoke? It happened during a 2716 burn. I can't check right now but I'm pretty sure I have a few of those TMS2716s in the stash.

Tez
Excellent article as usual, Tez!

Yes, those oddball TI 2716s have bitten a few people, as well as the 2532s...

Another 'non-standard' EPROM worth mentioning is the Motorola 68764/68766, which is a 24-pin direct replacement for many 8kB ROMs as used in old IBM PCs, Commodore, etc., while the JEDEC 'standard' 8kB/64kb EPROM is a 28-pin chip with similar pinouts etc. as the larger ones.

As well as the manufacturer you should also check the suffix, and not just for the speed; there are 'OTP' (One Time Programmable) EPROMs without a window that are not in fact eraseable even though they have the same part number as the eraseable version, with only a different package code. Something to beware of when ordering EPROMs.
 

tezza

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Another 'non-standard' EPROM worth mentioning is the Motorola 68764/68766, which is a 24-pin direct replacement for many 8kB ROMs as used in old IBM PCs, Commodore, etc., while the JEDEC 'standard' 8kB/64kb EPROM is a 28-pin chip with similar pinouts etc. as the larger ones.

As well as the manufacturer you should also check the suffix, and not just for the speed; there are 'OTP' (One Time Programmable) EPROMs without a window that are not in fact eraseable even though they have the same part number as the eraseable version, with only a different package code. Something to beware of when ordering EPROMs.

Thanks Mike, this is another bit of vintage "wisdom" which the new EPROM user would benefit from knowing. I'll work it into the article somehow when I get a chance (plus correct those spelling mistakes (-: ).

Tez
 

tezza

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Thanks Mike, this is another bit of vintage "wisdom" which the new EPROM user would benefit from knowing. I'll work it into the article somehow when I get a chance (plus correct those spelling mistakes (-: ).

Tez

Article updated. The additions strengthened the content.

Tez
 
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