Eramco MLDL schematics?

[MeindertKuipers]

Hi all,
I have an original Eramco MLDL with 2* 4K SRAM and 6 EPROM banks. This is the 3 PCB version. I am trying to get it back in shape again as it behaves a bit erratic.
Does anyone have the schematics available? A long long time ago I started to reverse engineer it and have the EPROM board schematics sorted out, but I do not have schematics of the SRAM board and main controller PCB.
Although these boards are not very complex, schematics would help to find out what exactly needs to be fixed.
Some of the EPROMs work, some unreliable, and the SRAM does not work at all. I intend to replace all cabling and possible faulty components, and then probably offer the restored unit for sale.

[MeindertKuipers]

So nobody seems to have it ...

I have started to reverse engineer it myself. Luckily I made photographs of the PCB's before assembly back in the old days, so this makes the task a bit easier. I will publish the schematics when it is finished. What I can say now is that it closely follows the MLDL schematics published in the PPC Journal V9N3. I have copies of that issues printed om my desk now. This is probably the issue that I have read most!
I have seen a few flaws in the Eramco MLDL already: there are no decoupling caps, and no buffer caps on input power.

[hth]

Could you also publish some comments of it compared to the original design and the comment on the flaws in either of the designs? It would be of interest to me at least to read about it.

I built my own MLDL back in the days based on that one in the PPC journal, with a couple of modifications.

Håkan

[Dan Grelinger]

(05-01-2018 03:28 PM)MeindertKuipers Wrote:  I have seen a few flaws in the Eramco MLDL already: there are no decoupling caps, and no buffer caps on input power.

Interesting. It is amazing how so many (supposedly) professionally designed and commercially produced electronic products have these kind of flaws. I reverse engineered the ZEPPROM ZVC programming fixture several years ago and found a fundamental flaw in how the voltage converter chip was wired. It likely lead to the over-current failure of a discreet component on the board, and rather than correct the fundamental problem (perhaps the circuit boards had already been printed?) a higher capacity discreet component was used to prevent failure.