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SOL-20 UVEPROM module - help.

Hugo Holden

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I have attached a photo of the personality module I found in the SOL-20 I am restoring.

I have found all kinds of issues on the motherboard so far such as IC's with missing pins(including the CPU) and corrosion and socket issues, so I think the computer was not working recently and various IC's were pulled and re-fitted poorly. I'm working through all this before I'm game to power it.

In the meantime I am concerned about the ROM module:

One of the IC pins on U2 wasn't in the socket hole it was bent over so not connected! Also I am wondering if the IC array has been plugged in out of order,or not.

The ROMs had a small paper sticker on the window, except one sticker was totally missing on U2. This worried me so I put light occlusive foil over all of them to help reduce the total light exposure from now at least, and transferred the label markings that were on the original paper stickers onto these new aluminium stickers. But the labels look out of order with respect to the U1 to U-4 socket labels.

So the first question is, does this look right or not or is it likely the roms are in the wrong sockets ?

Secondly, does anybody know how I can contact Mr. Martin Eberhard ? I want to buy his MM5204Q programmer kit, it is looking like I might need one.
 

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ldkraemer

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Hugo Holden

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Hugo,
The order of the EPROMS does look suspicious. Maybe if you can read them it will help.

I found this site with information on the 5204 and programmer. Just need to download the Kilobaud issue for Sept 77.

http://deramp.com/downloads/mfe_arc...Semiconductor/Memory Components/MM5204 EPROM/
https://www.google.com/url?sa=t&rct...zine-1977-09&usg=AOvVaw28Y5HbCFvqOVY_C2ARnAwB

Maybe that will get you going for less than $20 like the article says.

Larry

Thanks, but unfortunately it is not that simple. I have already looked at the Kilobaud article, the design was made to work with a KIM computer. Also with the asm program on the deramp.com link, I have no way to assemble it and execute it currently. This is why ideally I need the programmer made by Mr Eberhard.

Also, as yet I cannot find Processor Technologies diagram of this board with the four UV eproms on it. Perhaps if someone has one, the labels could be checked to see if they are similar. The fact that one IC had a disconnected pin, makes me think it could never have worked like that, so the IC's must have been plugged in and out at some point.
 

deramp5113

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Looking at the schematic, U1 to U4 are in consecutive ascending address order as expected. I’d take a first guess and assume the S1 to S4 labels correspond to U1 to U4.

Hugo - you have my email, so send me an email and I’ll send you Martin’s.

Mike
 
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Al Kossow

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pcb.jpg

given the board is so small, you may be better off just making a new one with a 2816 on it.
 
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Hugo Holden

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Here are ICs reproduced and labelled if it helps. I don't have a programmer that can do 5204s unfortunately.

View attachment 48192

Snuci,

That is great thanks. It looks probably like what was written in pen on the original faded paper label S-"4", was most likely S-0 with unclear writing making me think it was a 4 and not an 0 (as there is no S-4) and the one where the paper label was missing, was probably S-1, and S-2 and S-3 are in the correct places (as probably are the other two).
 

Hugo Holden

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To check the theory of what I suggested above, that I mistook a 0 for a 4, I removed the aluminium sticker to look at the original paper sticker (photo attached). A closer look at it , it is a 0 with a sloping line through it, but because part of it was faded out on first glance it looked like a 4. So it looks like all the ROMs are in the correct order, and the one missing the sticker will have been the one with an S-1 label.Thanks also to Al Kossow for posting the image of his board too.
 

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ef1j95

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Another 5204 board here. I was worried about the state of the ROMs, too, but didn't have a problem. Keep posting as you restore. I had a few head-scratchers with my Sol.

IMG_0118.jpg
 

Hugo Holden

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Hi efj91,

Thanks for posting that image which also confirms the labeling and the correct ROM positions.

I have worked through the entire main board cleaning & lubricating IC pins and sockets. The pins on the Signetics IC's do well with age, but the silver plated ones on the TI IC's get heavily oxidised. The worst examples includes a few IC's where the pins had rusted off, but in every case I was able to save the original IC by soldering new donor pins to the remaining stumps. It is important to use only IC pins with the exact geometry so that the sockets are not damaged. I could have replaced some of the 74LS IC's but, it is nice to have all the originals with the '70's date codes. I'm still not game to power the main board until I have completed restoring and testing the power supply with dummy loads, and there is the keyboard yet to be done, I'm awaiting the new pads. Then I'm going to have a go at repairing/testing some 16k memory cards then getting the Northstar controller board to work with two 360kB disk drives and Mike's VSG.
 

ef1j95

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Yes! TI ICs from that era seem to be the worst offenders. I did the same cleaning and pin repair during my restoration.

I have some notes on mine at https://sites.google.com/site/retroborkenwerk/sol-20

including the power supply repair and keyboard refurbishment (I punched my own pads - quite easy.) Mike's site is very helpful and I followed much of what he did (although I didn't make his mod to the PSU.) The check-out procedures are reasonable in the manual, so be sure to take it slow and steady. My machine was super-glitchy and I traced this back to bad contacts in the sockets for U65, U66 - the data bus multiplexers, if I recall. I have the Sol running on a N*S controller and Shugart mini floppy with the VSG.

Good luck! Keep posting!

-eric
 

Hugo Holden

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Yes! TI ICs from that era seem to be the worst offenders. I did the same cleaning and pin repair during my restoration.

I have some notes on mine at https://sites.google.com/site/retroborkenwerk/sol-20

-eric

Eric,

I must say that I like both your writing style and your restoration philosophies.

I have only recently started restoring vintage computers. I started with an IBM-5155 and now the SOL-20. I am actually a vintage television restorer, specializing in pre-WW2 TV sets, here is a typical one I have restored, as you can see it is a major undertaking to do it properly:

http://worldphaco.com/uploads/HMV__904_ARTICLE.pdf

In the same way that vintage computers with large whirring hard drives stirs up notions of the way the computer industry was in the early days, the same applies to television. One reason I wanted to restore a pre WW2 TV set is that I wanted to experience the result first hand, to understand what it would have been like back then. A bit of time travel into the past if you like. It is the same with vintage computers. It is a great feeling to get them up and running and feel & see just what they could do in those times. Computers are a different level again though, what you can do with them, even the early models, is only limited by your own imagination.

One other area I'm interested in is early TTL based video games, my favorite is Atari's arcade Pong. I designed a pcb for one with the 6 original hardware bugs removed and combined it with an Apple II monitor:

http://worldphaco.com/uploads/ARCADE_MINI-PONG.pdf

Hugo.
 

Hugo Holden

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These write-ups are great and now I want to build a TTL arcade Pong!

Eric,

Thank you for those remarks.

Before I made the mini pong (and figured out how to eliminate the six bugs which I have noted elsewhere are no distraction from the genius of the original design) I noticed that there had never been a detailed circuit analysis published on it. So I set about doing that and created a very long and detailed article on it:

http://worldphaco.com/uploads/LAWN_TENNIS.pdf

It turned out that the design gave the ball 42 states of motion.

The game's designer Mr. Allan Alcorn, contacted me after I published it and I was able to interview him and ask questions about the design and the decision making at the time that resulted in its final form.

I had also heard there was a fellow in Germany who had attempted to implement the entire game with an FPGA, though I have not seen the result of that or if it got finished.

Hugo.
 
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