RE: Repairing a SFD-1001 (8250/LP, 8050, 4040, 3040, 2040)

As far as I can remember there were (at least to problems to replace a rom
by an eprom)

- some eproms where a little bit slower than eprom (worked by choosing the
right one)
- the programmation pin (normally used as chip select was not correctly
working
  When driven by a chip and had to be use with a fixed value 0 or 1  (I
don’t remember)
  [I just remember having had the problem]

Ever tried to replace an eprom by an emulation with a pic or avr ?
I'm thinking to try :)

--
Didier


-----Message d'origine-----
De : owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] De la part de Jim Brain
Envoyé : mercredi 10 août 2011 14:31
À : cbm-hackers@musoftware.de
Cc : Anders Carlsson
Objet : Re: Repairing a SFD-1001 (8250/LP, 8050, 4040, 3040, 2040)

On 8/10/2011 2:27 AM, Anders Carlsson wrote:
> Jim Brain wrote:
>
>> I'm now less concerned about demand for such an adapter,
>
> Very nice!
>
> As well as replacing broken chips, an adapter with programmable ROM 
> part would be useful for anyone who has a working drive with an early 
> DOS version. I had 2-3 drives of the 3040/4040 variety which were 
> equipped with DOS 1, how odd it might sound. I found in order to 
> upgrade, one needed to replace both the ROM chips and the RRIOT. We 
> discussed this at the Vintage Computer Forum and came to the 
> conclusion some adapter boards were needed, where I could plug in the 
> old 6530 and a small EPROM just like it is done on the 8250LP.
>
> Also it appeared 2532 EPROM's are not suitable replacements for the 
> 2332 (?) ROM's in the drive. They work fine in a PET computer though, 
> just not in the drive? We checked the pinout and saw some references 
> on pinball repair sites about them having the same problems replacing 
> ROM with EPROM, so perhaps this is a real problem and not just me 
> failing to program them properly.
>
> Most of this however are moot points now as I have traded away the 
> drives to other people. Of course they might want to make the DOS 
> upgrade later on, but then there needs to be a solution to the ROM 
> replacement. Would Jim's ROM-el work or is that only for 8K chips and 
> upwards?
>
> Best regards
>
I *think* the 2332 and 2364 pinout is similar, so a 2364 ROM-el could be 
used as a test.  I'm happy to wire one up and send it somewhere, if 
someone can test it.  My concern is that ROM-el looks like an EPROM 
electrically, so it could have the same issues.

Jim

-- 
Jim Brain
brain@jbrain.com
www.jbrain.com


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