[sdiy] seek help on Jupiter 6 repair

[Rainer Buchty]

> Greetings ESQ. Rainer,

:)

> Those voice card 2732s were clean as a whistle, all 0xffs.  Seems strange to
> me for a decaying effect, shouldn't there be some distribution in there?

Depends... Robert Rottmerhusen did some tests how EPROMs behave during
erasure and how erasing physically looks like. His results are on

	http://www.rottmerhusen.com/test/epromerase.html

The animated GIFs he generated are quite impressive.

> They both have smooth silver Roland stickers over the windows.  The pins on
> one of the chips looks kinda bent which made me a little suspicious but the
> other one has nice straight leads.  I've  disassembled the controller file.

Then my assumption is that the EPROMs were indeed programmed with one of
those "fast" algorithms. (Makes me wonder if my old C=64 would come up
since I programmed a custom Kernal EPROM back then using fast
programming.)

In one of my boxes I found an old 2716 which behaves just the opposite way
- I'm not able to erase it, no matter how many hours it spends under the
UV eraser.

Rainer

-- 

Rainer Buchty, LRR, Technical University of Munich @ Garching
Phone: +49 89 289-18477, Fax +49 89 289-17662, Room 01.06.061