lordhailsham
Member
- Joined
- Apr 18, 2018
- Messages
- 30
So you will have seen the 'Capacitor C1' section of [here].... on minuszerodegrees.net
Hi Chuck - I don't actually possess a CGA monitor - I was thinking of getting a CGA-to-HDMI adapter kit on the ebays... but now I see there's a composite video, that might be the way to go. Not sure if I have a newer or older video card, elt me checkThe capacitor matters if you have an older CGA card and you feed your monitor from the composite video output of the card. If you're using the RGBI output, it has no effect.
You can ignore the damage if the capacitor is electrically sound.So given the cautions about soldering directly onto the motherboard, would it be something I could safely <COUGH> ignore ...
Note that the capacitor is a necessary component in the circuity that generates various clocks. See the adjustable capacitor at the far left of the diagram at [here]. Without the capacitor, there will be no clocks.... or remove for now?
I pulled out an IBM 5150 motherboard and an IBM 5160 one. I see that for the adjustable (variable) capacitor, the inter-hole spacing is slightly different between the two motherboards. Important information for those who are seeking an exact fit.Just covered this last summer : https://forum.vcfed.org/index.php?t...t1-trimmer-pot-for-5150.1239183/#post-1279850
That capacitor i used and refer to in the thread is NOT AND EXACT fit.. But it installed fine and works fine. Thats all I cared about.I pulled out an IBM 5150 motherboard and an IBM 5160 one. I see that for the adjustable (variable) capacitor, the inter-hole spacing is slightly different between the two motherboards. Important information for those who are seeking an exact fit.
Yeah mine looks like to got whacked, and is a bit smashed up... I am not sure I can assume it is sound .You can ignore the damage if the capacitor is electrically sound.
I can picture in my mind that is exactly how it went!All I can guess is that there was some stage in the QA testing where there was a worker with a frequency meter and an alignment tool tweaking things.
Probably nothing I would imagine. It is part of the oscillator circuit that eventually provides the CPU clock among other things (more critically things to do with video). Its not really something the user should go messing with, unless they know what they are doing and have the tools to dial it in correctly.Exactly what did the geniuses at Boca Raton expect the average user to do with the cap? It's deep inside the machine and not addressed at all in the Guide To Operations and its purpose is rather narrow. All I can guess is that there was some stage in the QA testing where there was a worker with a frequency meter and an alignment tool tweaking things.
My only guess would be "to save $0.5", or whatever was the cost of the oscillator circuit. It is likely that 14.31818 MHz crystals were cheap, being a popular frequency used for NTSC colorburst.So why didn't the geniuses at Boca simply place a tweakable oscillator on the CGA card? It's not as if they were trying to save money; witness the dead ends on the MDA card.
Has anyone run into a situation where dinking with the trimmer has been necessary?
I guess it depends on how it is broken. Not adjustable is probably fine. But the cap is in series with the crystal so if it is non conductive the oscillator may not work at all.To answer the OP question, it is likely that the motherboard will work just fine with the broken trim cap.