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New Sol-20 Owner

Glad you're going. I used an eraser for good measure whenever I take those Keytronic keyboards apart whether it's needed or not. .

I played around with a few more of Nama's WAV files and most worked. I tried the RAM checks and they were either taking forever with no screen output or those didn't work but I didn't get any errors. Maybe I didn't wait long enough?

It's an impressive machine for the era it came from.
 
One tip to everyone with a sol-20. Impressive machine yes, but think about this. There is a fan but no "exhaust" area for the air so you will have moisture accumulate because of the heat cycling.

Get some of those moisture absorbing packs that you get in vitamin bottles and put them under your keyboard and replace them about once or twice a year.

So there was a bit of an over site. BTW. PT's solution was to go aluminum for the covers and coat the chassis on later units. Not as easy or as cheap as creating exhaust ports at the front underneath the machine, which they should have.

But for a 1976 designed machine... Yes impressive for an all-in-one.

Cheers,
Corey
 
I've recently gotten CP/M 2.2 up and running on the Sol-20 using a Micropolis FDC and Micropolis Mod-II drives. This could easily be extended to Mod-I drives if anyone needs it. It shouldn't be too hard to get Micropolis MDOS up and running on this platform as well if someone is looking is looking for that.

Mike
 
deramp5113 said:
....... I found and ordered a power switch......

Mike
Click to expand...

Would you happen to have a part number handy (after 7 years!) for the switch? :D I've looked at the Oslo Switch ones and the Q-Series looks promising, but I haven't yet had time to narrow down the choices that look like they will fit. I'm looking at Mouser at the moment.. Haven't yet checked Digikey.

Thx,
Rick
 
Jaycar sells a line power rocker switch that pushes and clicks in perfectly to the existing rectangular panel hole. It is probably available elsewhere:

https://www.jaycar.com.au/dpdt-large...witch/p/SK0981

My original Sol power switch had also malfunctioned, however I was able to open it up and repair it, oddly it was missing a small spring (one of two in there). It also had a translucent white button (with a chrome surround) with a neon bulb in there, that was not connected, very nice really.

I'm a bit of a fan for old switches and indicator lamps, especially with glass covers, like many made by Dialco. Recently I found some large neon indicator lamps that are the same as the ones used on the power panels at Alcatraz. When I went there and saw them I thought, Oh, have to get some of those.

While you are at it I would recommend stocking up on a replacement Fan too.
 
Thanks guys for the links and and other information about the switches and available options. I don't need it at the moment, but would like to have a replacement on hand should it decide to up and die. Good idea on the fan too Hugo. I've got numerous old PC case and PSU fans around, but I suspect the one in the Sol is better, if not for the construction aspects of it. (metal, weight, etc.). I'll check out these parts and decide.
 
redjr said:
Thanks guys for the links and and other information about the switches and available options. I don't need it at the moment, but would like to have a replacement on hand should it decide to up and die. Good idea on the fan too Hugo. I've got numerous old PC case and PSU fans around, but I suspect the one in the Sol is better, if not for the construction aspects of it. (metal, weight, etc.). I'll check out these parts and decide.
Click to expand...

Yes the SOL-20's fan is not like most modern computer fans at all. It is quite a piece of solid engineering. They are still available, I found some a while back on the bay.
 
Corey986 said:
One tip to everyone with a sol-20. Impressive machine yes, but think about this. There is a fan but no "exhaust" area for the air so you will have moisture accumulate because of the heat cycling.

Get some of those moisture absorbing packs that you get in vitamin bottles and put them under your keyboard and replace them about once or twice a year.

So there was a bit of an over site. BTW. PT's solution was to go aluminum for the covers and coat the chassis on later units. Not as easy or as cheap as creating exhaust ports at the front underneath the machine, which they should have.

But for a 1976 designed machine... Yes impressive for an all-in-one.

Cheers,
Corey
Click to expand...

The fan is the exhaust! Last time I checked it blew out - about an 1 hr ago. Is yours blowing in?
 
Yes the fan blows outwards. Have a look at this article pages 23 on. It explains the thermal management problems in the SOL. In mine I added an auxiliary fan (without drilling any extra holes) that blows inwards to increase the air flow across the S-100 boards. It was not a wonderful idea to have the boards stacked horizontally as they did, because it traps the hot air between them, still, it made for a much more compact computer.

One other thing that helps is to run the SOL from a Variac. I use an automatic one I designed. But for a manual one, you just keep lowing the line voltage until ripple appears in the video signal, then just increase the line voltage a tad until the ripple vanishes. This results in the lowest possible thermal dissipation in all the regulator devices and the lowest possible temperature in the computer.

Don't be tempted to think you can replace the 7805 regulators with high efficiency switching types, in my experience these are hopeless and problematic and not a patch on the original 7805's,especially in terms of failure modes and over temperature and current overload shut-down properties, well thought out by the designers of the 7805, even though they are less efficient and generate more heat than a switching modules that some recommend without thinking through the failure modes and protective function in the original 7805.


https://www.worldphaco.com/uploads/PROCESSOR_TECHNOLOGY_16kRA_RAM_CARD.pdf
 
Apparently, back in the late 70s, early 80s when I used it quite a lot, I never experienced any over heating issues (or that I was aware of). I even recall, there was a period of time in there where I had all the S-100 slots filled. And, in my particular case, I had two additional largish PCBs attached to the Sol mobo as well (video and Z80cpu upgrades). Maybe I was just lucky. ;) Now, that I'm getting it back up and running, I haven't noticed any indications or behavior with regard to heat. Now admittedly I have not been doing any type of heavy processing either. I haven't been tempted to replace anything unless something fails. I ran it for 5yrs between 78-83 daily without issue, so I guess that's a testament to the original design and performance by Bob Marsh and others created. Of course some minor things were improved over the Sol's short production lifetime.
 
redjr said:
Apparently, back in the late 70s, early 80s when I used it quite a lot, I never experienced any over heating issues (or that I was aware of). I even recall, there was a period of time in there where I had all the S-100 slots filled. And, in my particular case, I had two additional largish PCBs attached to the Sol mobo as well (video and Z80cpu upgrades). Maybe I was just lucky. ;) Now, that I'm getting it back up and running, I haven't noticed any indications or behavior with regard to heat. Now admittedly I have not been doing any type of heavy processing either. I haven't been tempted to replace anything unless something fails. I ran it for 5yrs between 78-83 daily without issue, so I guess that's a testament to the original design and performance by Bob Marsh and others created. Of course some minor things were improved over the Sol's short production lifetime
Click to expand...

Actually I did not have any heat related "failures" in the SOL either, even when I had nearly all the board slots filled with various boards. It just it got too hot in there for my liking and I have seen the effects of this on shortening the life on various components. So I wanted it cooler. But it may well have been inside design parameters. Although I remember a post of some memory cards in a SOL failing when the temp came up. In any case IC's and electrolytic capacitors "love cool". This notion has applied in modern times, we have a server room at work, the units kept failing with monotonous regularity until we installed a high power air con system and dropped the temp to 16 deg C. now they practically never fail.
 
Maybe different memory cards (were designed), or didn't require the level of cooling you desired. I never owned any of PTs memory boards IIRC. I do like the idea of a fan like you installed, but it seems like such a 'brute force' approach to cooling. But if there's no other way..(Sol's design). I've always cooled things by simply pulling in cooler air through whatever vents you have and exhausting the warmer air. I agree that in most cases, heat is the enemy of electronic parts, and should be spec'ed according to the constraints of their design.
 
redjr said:
Maybe different memory cards (were designed), or didn't require the level of cooling you desired. I never owned any of PTs memory boards IIRC. I do like the idea of a fan like you installed, but it seems like such a 'brute force' approach to cooling. But if there's no other way..(Sol's design). I've always cooled things by simply pulling in cooler air through whatever vents you have and exhausting the warmer air. I agree that in most cases, heat is the enemy of electronic parts, and should be spec'ed according to the constraints of their design.
Click to expand...

The thing is with the SOL, with the fan blowing outwards, it generates a negative pressure in the case, air gets drawn in around the keyboard, and though the slot in the back as there is a gap where the top cover fits, Only a small proportion of the air flow goes over the s-100 cards because the card carrier only has some small slots down the side facing the PSU unit . So the card cooling is pretty poor. But the power supply cooling is very good. This is why the S-100 cards get very hot without the added fan. A soon as the top cover is removed the airflow drops because the original fan takes in air from immediately above it, then there is negligible air flow across the cards, so when the cover is off it pays to place a book over the power supply section which then allows more air flow via the side slots in the power supply cage adjacent to the s-100 cards.

There are some fan cooled instruments that protest when their outer covers are removed. One classic case is the Tek 2465B scope. Without the cover on, the H deflection IC's cooling drops off and it overheats. But some service technicians don't know, so they leave it running out of the case for some hours while fixing other issues and the IC, now getting harder to get, a Tek IC (though Maxim made a clone) fails. The solution is either to blow a fan on it, or add a heatsink to it, which is what I did in all my scopes of this type.
 
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