Sol-20 Video Cable?

[Jeff Robison]

Greetings all -

I posted for the first time about a year ago looking for input on an entry point into S100.

Today I have a couple of Sol-20's on the way and I am looking for info on the video connector. Would I be able to get away with any old F-connector coax cable with an PL-259 adapter on the computer end? Or is RG59/U a requirement?

Is there a source for these types of cables or are you guys just rolling your own?

Thanks,

Jeff

[Randy McLaughlin]

Why would you want an F connector - the sol puts out NTSC - you should need an RCA for most TV's or monitors.

https://www.ebay.com/itm/164180912951?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=164180912951&targetid=4580771609030758&device=c&mktype=&googleloc=&poi=&campaignid=410490118&mkgroupid=1234751784804585&rlsatarget=pla-4580771609030758&abcId=9300491&merchantid=51291&msclkid=7e3077a4ad211b98dfb317cbc61c851b


Randy

[Jeff Robison]

I was hoping to use a contemporary TV set. I've got an adapter I use for other composite devices, so this will work.

Thanks for the link.

Jeff

Either connector would be fine I guess.

[Randy McLaughlin]

F connectors are for RF, the Sol puts out NTSC - the RCA is the one you need.

I know of no use where NTSC uses an F connector.


Randy

[Dennis Boone]

> https://www.ebay.com/itm/164180912951

Note that this patch cable is a 50 ohm assembly. Is the Sol a 50
ohm or a 75 ohm device? A mismatch won't prevent it from working,
but will presumably have some effect on picture quality.

De

[Randy McLaughlin]

You are over thinking it.

The cable may say 50 ohm or 75 ohm but that has nothing to do with anything. If you measure the resistance of a cable marked 75 ohms and a cable marked 50 ohms you should find the resistance of both to be near 0 ohms.

You can use an rg-175 or RG-6 equally over a short distance unless the frequency is especially high (not the case for NTSC).

The ohms are in fact the resistance on the monitor side not the cable.

You want a coax cable to keep the signal clear but you could use two wire coat hangers or lamp cords and it would work.

Most NTSC monitors just use audio quality RCA cables.



Randy

[Udo Munk]

Uhm, the electrical resistance of a coax cable is almost 0, the 50 or 75 Ohm is the impedance for
high frequency waves. Of course you need to use cable with the correct impedance, or the signal
will be weakened, in worse case the transmitter gets destroyed. That won't happen with the low
power used for such video output, dependent on the length of the mismatched cable the video
circuit in the receiver might not be able to sync correctly.

[Randy McLaughlin]

That would be true at either higher frequencies, higher power, or possibly longer cables none of which applies. The monitor should have a 50 ohm resister to terminate it (some professional monitors have a pass-through and the 50 ohm resistor can be removed if external or bypassed with a switch). At the frequencies we are talking about the worst case scenario would be a fuzzy display caused by slight distortion.

As I stated and have seen many NTSC monitors connected with audio cables, RG-6, RG-59, RG-175, and other cables. older security video systems used NTSC and used terrible cables and generally worked just fine as long as they were kept away from florescent lights or motors.


Randy

[Jeff Robison]

Insightful comments, everyone. Thank you.

I have sourced a cable that meets the manual’s specifications, but I have another question regarding the video output from the Sol.

There’s a statement in the user manual that should the user need to connect the Sol to a TV, they should see their dealer for the proper solution. Also, on page 6-6 of this manual (
https://www.sol20.org/manuals/img/SolTerminalComputerUsersManual.12-78-img.pdf) there’s a reference to a toggle switch on the PT-872 display. This reads as if the monitor had a built-in RF modulator. Was this the case? That seems like a big deal for the time if true.

I see a lot of recent setups that use period correct TVs, can we surmise how they are likely to be hooked up to the Sol? The implication I am picking up is that there’s no RF modulation happening within the Sol. If that’s the case, then I think any old RF modulator would work?

Also, it looks like the thread got removed from the S100 group. Not sure why, the Sol-20 definitely fits the description :).

Thanks for your help on this. I am coming into the Sol from the Apple II world, and I am having to rethink a lot of assumptions I have about the hardware.

Jeff

[Randy McLaughlin]

Back when the sol-20 was designed people often used modified TV's to bypass the tune and use NTSC. I had a friend that did that to connect to an Imsai using a dazzler. It was an ungrounded hot chassis he used and put 110vac on the video out of the dazzler. He spent moths working on it and never got the front panel to work right.

Ignore the references and just use any TV with composite video. It is simple straight cable from sol to TV.

Don't over think it. TV's now are safe and uses exactly the signals needed.

As I said TV's didn't have video inputs back then. You either modified a TV or bought a monitor. Now TV's are equivalent to monitors back then.

People may argue about cable impedance that doesn't affect a sol but everyone would agree you just go from 259 to RCA and plug it straight into a modern TV.



Randy

[Jeff Robison]

Thanks, Randy.

-Jeff

[Randy McLaughlin]

Sorry back to modulation if you get a period correct TV a $15.00 modulator from Walmart etc would work.

The problem being the old TV's will strain your eyes and be harder to read. Also the old crt's would burn the screen because the sol would keep the same basic image that would cause the electrons to hit the same pixels over and over damaging the screen. Led TV's use such a lower energy that's not a problem generally. But I do have a client that has lots of cash and decided to use a 70" TV for his camera system and burned the image he hated the burned image and bought another TV but leaves it off when not being used.


Randy

[dxforth]

On 11/04/2021 14:24, Randy McLaughlin wrote:
> Sorry back to modulation if you get a period correct TV a $15.00 modulator from Walmart etc would work.
>
> The problem being the old TV's will strain your eyes and be harder to read. Also the old crt's would burn the screen because the sol would keep the same basic image that would cause the electrons to hit the same pixels over and over damaging the screen. Led TV's use such a lower energy that's not a problem generally. But I do have a client that has lots of cash and decided to use a 70" TV for his camera system and burned the image he hated the burned image and bought another TV but leaves it off when not being used.
>

Now we're talking serious 'old-school' :)

https://en.wikipedia.org/wiki/Screen_burn-in

Under normal conditions of use (personal computer user) I wouldn't expect a
computer monitor to exhibit the problem.

[Jeff Robison]

Good points. If you'll pardon the tangent, I want to ask about fuses.
I think I have purchased 3 fuses in the last 20 years, so I don't have
much experience beyond going off what is specifically written in the
manual or silkscreened on the PCB. For the PSU user serviceable fuse,
the Sol manual states 3A and 3.2A (I assume 3A will suffice) but what
about physical size? I am not clear on how to determine this.

Thanks

[Randy McLaughlin]

On Sunday, April 11, 2021 at 8:01:40 AM UTC-5, bush...@gmail.com wrote:
> Good points. If you'll pardon the tangent, I want to ask about fuses.
> I think I have purchased 3 fuses in the last 20 years, so I don't have
> much experience beyond going off what is specifically written in the
> manual or silkscreened on the PCB. For the PSU user serviceable fuse,
> the Sol manual states 3A and 3.2A (I assume 3A will suffice) but what
> about physical size? I am not clear on how to determine this.
>
> Thanks
>

"3AG glass fast blow", any hardware store should have them.


Randy

[Randy McLaughlin]

Screen burn was common for old school CRTs where the pattern gets burned into the phosphor on the front of the screen. If you try to use an old school TV based on CRTs expect it, not on led monitors.

Screen burn in is/was reduced by screen saver software on PCs and up and by turning screen off when not in use.


Randy

[dxforth]

Schools are a great place for equipment abuse. A relative was in the TV repair business
in the 60/70's. He frequently bought up B/W TV's donated to op-shops for refurbishing.
If there was a fault with CRT's it was typically weakness. 'Burn-in' was rare to the
point of non-existent.

Regarding 'PC screen savers' I suspect it had more to do with - it could be done,
rather than it was necessary. If burn-in has become an issue again today, it's thanks
to OLED screens (more power), the practice of stations using fixed logos and content,
and users being discouraged from altering factory-preset brightness/contrast levels.

[Randy McLaughlin]

Trust me I have seen hundreds of monitors that were burned so bad the software main menus was clearly legible with the monitors disconnected.


Randy

[dxforth]

After what amount of commercial use? Were CRT's prone to burn-in, I'd expect to
see it a regular topic of discussion on forums such as this over the decades the
devices were in vogue. If so, it's news to me and not my experience.

[Steven Hirsch]

I've seen this type of burn-in many times on CRT monitors used in POS systems.

[Dennis Boone]

> After what amount of commercial use? Were CRT's prone to burn-in, I'd
> expect to see it a regular topic of discussion on forums such as this
> over the decades the devices were in vogue. If so, it's news to me and
> not my experience.

Er, come out from under that rock. You need sun.

De

[Jeff Jonas]

>>> Trust me I have seen hundreds of monitors that were burned so bad the
>>> software main menus was clearly legible with the monitors disconnected.

>I've seen this type of burn-in many times on CRT monitors used in POS systems.

Me too, particularly login screens
and anything with text in the same place for a long time
such as airport and train displays.

VFD (Vacuum Fluorescent Displays) suffer burn-in too.
I took some photos: ferretronix.com/tech/vfd

--

[Jeff Jonas]

I've seen severe CRT burn-in where text was in the same spot for prolonged times
- login screens to mainframes
- airport and train displays

VFD (Vacuum Fluorescent Displays) are also prone to burn-in.

[dxforth]

I still use one of these (albeit different button placement):

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=274571165300

I estimate 35 years old. Is it less bright? Hard to say - I'm
that that much older and still looks fine to me.

Can't say the same for a Panasonic microwave fluorescent display
which is maybe 10 years old.