Thread
Mac+ OS floppy request
i hated working on multisync monitors. things were a real PITA to troubleshoot, probably because i didnt understand how it worked too well, and still dont.
The interesting thing, was the viewsonics and the 2 separate horizontal paths, had an HV output, and horizontal output, on 2 separate circuits. not an all-in-one common circuit. It would run for awhile without an issue then one day, it would just take out the horiz transistor. replace it, it was fine again for another couple of weeks.
hated them. glad they are gone....
The interesting thing, was the viewsonics and the 2 separate horizontal paths, had an HV output, and horizontal output, on 2 separate circuits. not an all-in-one common circuit. It would run for awhile without an issue then one day, it would just take out the horiz transistor. replace it, it was fine again for another couple of weeks.
hated them. glad they are gone....
Multisyncs can be fun, I would give tutorials to the test guys (post manufacture) showing how they worked and what to look for if they don't work. I think it was a little easier for us tecknight as these were our designs so knew them inside out.
Design is fun too, two things stick in my mind. With the multisync concept be careful with a low line rate should the HT remain the same = very high voltages and usually something went boom. Well fizz boom actually.
A design engineer was measuring beam current using a rather crude but effective method (I'll spare you the full details) except his natural reaction was to grab hold of the ammeter to change the range - he forgot it was at 25kV - yes not a pretty sight, he survived but a really nasty experience.
Design is fun too, two things stick in my mind. With the multisync concept be careful with a low line rate should the HT remain the same = very high voltages and usually something went boom. Well fizz boom actually.
A design engineer was measuring beam current using a rather crude but effective method (I'll spare you the full details) except his natural reaction was to grab hold of the ammeter to change the range - he forgot it was at 25kV - yes not a pretty sight, he survived but a really nasty experience.
yeap, a rather shocking experience. I wasnt paying attention when i was a kid, i had a monitor apart tinkering with it, I had it working and on, i layed my arm right across the anode. WEEEEEEEEEEEEEEEEEE... lets see, i woke up laying in the floor. i dont remember what happened in between the time i layed my arm on the anode, and the time i woke up on the floor.
Nothing probably happened. You were most likely just unconscious on the floor. It's possible you had a self-correcting cardiac arrhythmia (if you were hit during the wrong part of the repolarization phase) or a petit mal seizure during that time (hard to say, postictal behavior probably looks quite similar to the state of consciousness following a high voltage shock) but obviously no serious neuro/cardiac damage, otherwise you probably wouldn't be here posting, unless your parents found you very shortly afterward.
no, i was perfectly fine.
But that was the first and the last time i messed with flyback voltages while ON.... Ive been zapped by charged CRTs on many occasions, but thats just a "tickle" compared to what happened when it was live. ive been zapped by electricity so many times growing up, now, when i come in contact with lines voltage, i hardly feel it. i just feel a tickle and go, oh crap. lol.
when I was probing voltages in a projector power supply, my pinky slipped while holding the probe and hit the 450V boost voltage. weee i felt that one, but it really wasnt too bad compared to that flyback event.
But that was the first and the last time i messed with flyback voltages while ON.... Ive been zapped by charged CRTs on many occasions, but thats just a "tickle" compared to what happened when it was live. ive been zapped by electricity so many times growing up, now, when i come in contact with lines voltage, i hardly feel it. i just feel a tickle and go, oh crap. lol.
when I was probing voltages in a projector power supply, my pinky slipped while holding the probe and hit the 450V boost voltage. weee i felt that one, but it really wasnt too bad compared to that flyback event.
It sounds like a good pair of thin, but sufficiently insulating, elbow-length rubber gloves would be a good investment 
and sexy
ROFL. that and one of those sticks linesman use on telephone polls. I forget the exact term for it though. slips my mind.
Actually this is an option, rubber gloves that is provided they are suitable. Many people might be home users who just need to make a few adjustments to the yoke, the rubber gloves do add a degree of protection.
I find as you concentrate on the screen (even with a mirror) and fiddling with the yoke it becomes all too easy to make contact with some HT. To make it more risky, these computers are getting old and the insulation is deterorating so making an unexpected flashover more likely. HT leakage from the flyback transformer, tripler or even anode lead can happen anytime. I'm pleased to say that the anode cap is a really good fit and only comes away of not installed correctly in the first place. And as you all know a CRT will recover a charge when left with no anode cap connected. }
The rubber glove technique does get used in industry, I have seen "professional" gloves, really thick certified gloves guarenteed up to a specified voltage. Somewhat distracting I must admit and to use a pair in a develoment lab would be.. well, get attention.
I find as you concentrate on the screen (even with a mirror) and fiddling with the yoke it becomes all too easy to make contact with some HT. To make it more risky, these computers are getting old and the insulation is deterorating so making an unexpected flashover more likely. HT leakage from the flyback transformer, tripler or even anode lead can happen anytime. I'm pleased to say that the anode cap is a really good fit and only comes away of not installed correctly in the first place. And as you all know a CRT will recover a charge when left with no anode cap connected. }
The rubber glove technique does get used in industry, I have seen "professional" gloves, really thick certified gloves guarenteed up to a specified voltage. Somewhat distracting I must admit and to use a pair in a develoment lab would be.. well, get attention.