I have a monochrome monitor

[Daniel Santos]

Hi Atari fans,

 

I have a working Atari 520STFM machine that I can connect to an HDMI monitor through a monitor cable that has the atari connector on one end and a SCART connector on the other, The SCART connector connects to a black box that outputs HDMI and then goes to the HDMI monitor.

A while ago I bought a monochrome SC1224 monitor from the USA. (I'm in Europe) I had to also get a step-down transformer to convert the 220V from Europe to 110V of USA to power the monitor. Its rated at 300W.

I connected all the cables, and the computer boots, the green led on the monitor lights up, If I crank up the sound volume on the monitor I can hear a Hum. If I press the keys I can hear the clicking sound coming out of the monitor, but there is no picture. There are some controls in the back to use with a screw driver. I fiddled a bit with them but nothing happened.

Did I get the wrong monitor ?

Thanks,

Regards

[bfollowell]

1 hour ago, Daniel Santos said:

Hi Atari fans,

 

I have a working Atari 520STFM machine that I can connect to an HDMI monitor through a monitor cable that has the atari connector on one end and a SCART connector on the other, The SCART connector connects to a black box that outputs HDMI and then goes to the HDMI monitor.

A while ago I bought a monochrome SC1224 monitor from the USA. (I'm in Europe) I had to also get a step-down transformer to convert the 220V from Europe to 110V of USA to power the monitor. Its rated at 300W.

I connected all the cables, and the computer boots, the green led on the monitor lights up, If I crank up the sound volume on the monitor I can hear a Hum. If I press the keys I can hear the clicking sound coming out of the monitor, but there is no picture. There are some controls in the back to use with a screw driver. I fiddled a bit with them but nothing happened.

Did I get the wrong monitor ?

Thanks,

Regards

 

Well, first of all, the SC1224 is a color monitor, not a monochrome monitor. Are you certain on the model number?

 

For an Atari monochrome monitor, you need to look for one of these:

 

SM-124
SM-125
SM-144
SM-146
SM-147
SM-144
SM-194
SM-195

 

I'm not certain that they all work with the ST/STe line, but I know that the first two do. The key is SM, monochrome, SC, color.

 

Now, as far as why you don't have a color image, I can't explain, but hopefully someone more knowledgeable will pipe in.

 

Edited May 10, 2021 by bfollowell

[Daniel Santos]

Then I don't have a monochrome monitor. I have a color one.

[Atari8guy]

Maybe a PAL vs NTSC issue? I don’t know enough to say but hopefully someone who knows more can elaborate


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[Chri O.]

13 minutes ago, 8bitguy1 said:

Maybe a PAL vs NTSC issue?

Definitely not that's only for the Atari with RF TV modulator output issue.

[bfollowell]

14 minutes ago, Chri O. said:

Definitely not that's only for the Atari with RF TV modulator output issue.

 

Yeah, like @Chri O. said. I'm fairly certain that's only for the modulator, which doesn't come into play if you're using the monitor port. If using your ST to SCART cable works with your converter box, then it sounds like your STFM is putting out a decent signal. It's sounding like the monitor is bad or there's some sort of issue with the step-down transformer.

 

[TGB1718]

I had similar issues with a Phllips Colour monitor, turned out to be the SCART connection, repeated 

removal and insertion had caused the solder joints in the monitor to crack, simply re-flowed with

fresh solder and it's working fine again .

 

Sort of rule of thumb, before diving into faulty electronics, check the physical things first, knobs, switches, connectors,

these thing are very old and have had a lot of use.

[Daniel Santos]

I checked the output of my step down transformer, and its giving 120V (correct) at 50HZ (WRONG!!).

The monitor needs 60HZ because that is the mains AC frequency in the USA.

Any one know of a step down transformer that can do 120V 60HZ 0.83Amps, I searched amazon but could not find one (yet).

[Daniel Santos]

I guess I am stuck with 50Hz. Only if the monitor could do 50Hz also. But I don´t know if it does.

 

[ParanoidLittleMan]

Exact frequency of power for monitors is not relevant. It works fine with 50 Hz too, especially if voltage is little more than 110 V . I mean it works if is not broken.  Simple transformers do not change frequency, only voltage. I guess that today is possible to buy converter what can give sinus output at desired freq. voltage. And what is sure is that it costs much more than new TV, monitor.

So, that monitor needs experienced repair man - like TV repair man.  Assuming that cable is really OK. So, best to check all lines with ohm meter.

And that would be: R, G, B , H sync, V sync, GND . And maybe composite sync too, although I'm pretty sure that it does not use it.

Then, is it possible that SC1224 sold in USA works not with 50 Hz video signal (not electric power !) ?  Someone pls. say his experiences.

 

[bfollowell]

5 hours ago, ParanoidLittleMan said:

Exact frequency of power for monitors is not relevant. It works fine with 50 Hz too, especially if voltage is little more than 110 V . I mean it works if is not broken.  Simple transformers do not change frequency, only voltage. I guess that today is possible to buy converter what can give sinus output at desired freq. voltage. And what is sure is that it costs much more than new TV, monitor.

So, that monitor needs experienced repair man - like TV repair man.  Assuming that cable is really OK. So, best to check all lines with ohm meter.

And that would be: R, G, B , H sync, V sync, GND . And maybe composite sync too, although I'm pretty sure that it does not use it.

Then, is it possible that SC1224 sold in USA works not with 50 Hz video signal (not electric power !) ?  Someone pls. say his experiences.

 

 

When you say it isn't relative, I'm assuming you're meaning to the video signal, but it would be very relevant to powering the monitor. He needs 110-120VAC, 60Hz to power the monitor properly. 120VAV, 50Hz will not work.

 

I just want to make certain that is clear to @Daniel Santos

 

Edited May 12, 2021 by bfollowell

[ParanoidLittleMan]

I did not use word "relative" . And I powered monitor from USA with 220/110 V transformer in Eu, and it worked.

Sorry Daniel Santos, you getting false 'advices'  .

Why it works not ? Because is old - over 30 years.  People who talking about power freq. must be at 60 Hz have no clue how PSU in some TV, monitor, computer is built. Even if it is not with switching PSU, 18% lower freq will not make problem.

The real problem is that fixing of it may cost more than new TV with Scart input . What is ideal for old computers.

I had SM124 - yeah, that's the monochrome one. Btw. smaller than SC...  . It started to have narrow and narrower pic some 15 years ago already. And I was just not interested in fixing it - because had LCD with much better monochrome pic. So, I gave it away.

Fixing ? I worked in that over 25 years.

Ah, bfollowell, explain me what is 120VAV - 120 Volts, Audio-Video ?

 

Edited May 12, 2021 by ParanoidLittleMan

[TGB1718]

40 minutes ago, ParanoidLittleMan said:

I did not use word "relative" . And I powered monitor from USA with 220/110 V transformer in Eu, and it worked.

Agreed, the mains frequency will have no effect on powering the monitor, it doesn't use the mains frequency for

anything, all that's required is the correct voltage.

 

[bfollowell]

3 hours ago, ParanoidLittleMan said:

I did not use word "relative" . And I powered monitor from USA with 220/110 V transformer in Eu, and it worked.

 

 

Obviously, if you guys have used U.S. devices with 120VAC, 50Hz and say it works, then you know more than me. If the frequency is unimportant, then why do we have different frequencies at all?

 

[Daniel Santos]

There is the refresh frequency of the video signal that comes from the computer, and theres the frequency of the power supply. It's the latter that I am talking about.

As I said, I can hear sound coming out of the monitor when I press the computer keys, and I can change the volume of that sound in the monitor.

I just don't get a picture.

[ParanoidLittleMan]

9 hours ago, Daniel Santos said:

I just don't get a picture.

Very true. In both senses.

[TGB1718]

2 hours ago, bfollowell said:

Obviously, if you guys have used U.S. devices with 120VAC, 50Hz and say it works, then you know more than me. If the frequency is unimportant, then why do we have different frequencies at all?

The 60Hz for NTSC and 50Hz for PAL are chosen to match the mains frequency to avoid noise in the electronics, this usually

results in "rolling bars" if they don't match, so the monitor should work, but there may be some unwanted effects on screen.

[bfollowell]

17 minutes ago, TGB1718 said:

if they don't match, so the monitor should work, but there may be some unwanted effects on screen.

Well, personally, I definitely wouldn't call that "working", but you guys were the ones that were saying a 60Hz U.S. monitor would work with 50Hz power. Either way, from what you said, I gather he's should have something more than a black screen, even if the screen were a little distorted or had unwanted effects.

 

[Daniel Santos]

What about changing the VHOLD and HOLD controls in the back of the monitor ? Would that help ?

[ParanoidLittleMan]

That 50 Hz in Eu and 60 Hz in US for TV half picture scan freq. is certainly because of frequencies of electric power, which are established much earlier.

And the reason was, as is said here too to avoid some rolling bars, rolling edges left and right. It was in time of early tube based TV-s, before transistor is invented. Those TVs just did not have so good voltage filtering, and no internal voltage stabilizer. It was common practice to use external voltage "stabilizators" - as it was called here - box with some special transformers, larger condenzator (capacitor) what gave stable 220V voltage to TV while input voltage was in range of some 180-240 V.  

Later TVs, which were manufactured in 70-es were in big part transistor and even IC based. And there were voltage stabilizers too. Which gave pretty stable and wave less output voltage. So, whole thing with matching freq. of power and video was not interesting anymore. Especially when people started to watch satellite TV - in 80-es. And same is with computers, monitors.  How on Earth SM124 with it's 71 Hz video freq has no 'rolling bars' in America ?

 

Now, back to topic. That SC1224 monitor was for longer time out of usage, as is told in first post here. That self is bad thing. And it is over 30 years old now. So, expecting it to work well is too optimistic.  I had cases when TV what was not so young, but not older than 30 years was out of usage over years.

They turned it off and saw unstable picture, waving. Typical case of bad voltage filtering - classic electrolyte capacitor weakening. So, brought to my service, and I told them that needs some repair, and little more test time - like 5 days. And with reason - some components broke during test time. Once even one larger electrolyte capacitor exploded near to my head, and aluminium case hit my ceiling. And some transistors, diodes, and probably worst thing: high voltage transformers broke. Latest was hard to find even when TVs, monitors were not so old - now impossible. And even if find, that will cost plenty.

That was something like worst case, as example.  And please stop with ideas like "What about changing the VHOLD and HOLD controls in the back of the monitor" .  There are hundreds of components inside monitor/TV, and any of it can broke. Older one - any of it certainly breaks. Or more of them.

As much time was spent with this thread, I think that is worth to remind: "time is money" . And new TVs are cheap now.

[ijor]

I have personally used a SC1124 monitor, as many other electronic equipment, with a step down converter (that provides 110V 50Hz) for years without any problem whatsoever. There were some electronic devices that were sensitive to the power frequency. I remember table clocks that used the power frequency to actually measure the time. Probably this design is not used anymore. But other than, there shouldn't be any problem mixing the power frequency, at least for consumer devices.

 

It is difficult to know what the problem exactly is in this case. But I would bet is not the power frequency.

 

[TGB1718]

9 minutes ago, ijor said:

I remember table clocks that used the power frequency to actually measure the time

Yes, they used synchronous motors that only ran at the main frequency of the country they were manufactured for.

[Daniel Santos]

Hey I know nothing about old monitors other than switching them on and off. Hoped someone here could help me understand if I have a faulty monitor, or the monitor is in the wrong country.

Anyway thanks for you time

[JuanIgnacio]

I bought a SM 124 , maybe 30 years old also. I thought it was faulty. Until moving the knobs I moved the brightness up and voilá, it worked!


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[ParanoidLittleMan]

Hard to believe that OP did not adjust those regulators when tried monitor.