Author Topic: CPC Monitors  (Read 740 times)

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Offline ComSoft6128

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CPC Monitors
« on: 13:24, 08 February 18 »
While looking at the July 88 issue of ACU, I ran across this letter regarding monitor problems, is the information correct?

"Lost Emission

ALEX McClure (May 1988) may be able to solve the problem with his monitor more cheaply than he thinks. The usual problem with ageing, fading televisions and monitors is that the electron guns in the tube have "lost emission", which is to say their cathodes don't produce enough electrons. Emission can often be restored by overunning the heater filaments for a short period. As this can also result in blown filaments and a useless tube it is best left to someone who knows what they are doing. I suggest Mr McClure asks at his local TV repair shops. From the sound of it, he has little to lose."
« Last Edit: 13:27, 08 February 18 by ComSoft6128 »

Offline Bryce

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Re: CPC Monitors
« Reply #1 on: 14:05, 08 February 18 »
Yes. Rejuvenating tubes was a common practice back then. Here's the type of device you'd need to do it:

https://www.radiolaguy.com/images/equipment/B&K_467-e.jpg

https://www.radiomuseum.org/images/radio/promax_barcelona/crt_analyzer_rejuvenator_rt_501b_859820.jpg

A LOT of experience is also needed to use these correctly. So don't go buying one of these and connecting it to a CRT, you'll most likely destroy the tube and maybe even yourself.

Bryce.

Offline Vyper68

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Re: CPC Monitors
« Reply #2 on: 08:43, 09 February 18 »
On the subject of monitors i was messing about with my CTM-644 ( the one with the melted case ) and my 6128 last night and i had my M4 and a 3.5 Drive attatched to it.
I think i have killed to the 5V supply as it just went off, it worked for a little bit then packed up altogether. The 12V is OK as when i plugged my new 5V PSU into the 6128 it worked fine and the 3" Drive was still powered.
Any suggestions as to what i have blown is it easy to fix???
Hopefully :picard:
Paul Woakes - Genius & Programmer

Thank you for Mercenary Paul

Offline robcfg

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Re: CPC Monitors
« Reply #3 on: 10:00, 09 February 18 »
I'd check the 5V cable for continuity.


It wouldn't be the first time I see one broken monitor cable.

Offline Bryce

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Re: CPC Monitors
« Reply #4 on: 10:08, 09 February 18 »
On the subject of monitors i was messing about with my CTM-644 ( the one with the melted case ) and my 6128 last night and i had my M4 and a 3.5 Drive attatched to it.
I think i have killed to the 5V supply as it just went off, it worked for a little bit then packed up altogether. The 12V is OK as when i plugged my new 5V PSU into the 6128 it worked fine and the 3" Drive was still powered.
Any suggestions as to what i have blown is it easy to fix???
Hopefully :picard:

There's a thermal overload in the monitor. You may have just been pulling too much current. It may be working again now if you try it.

Bryce.

Offline Vyper68

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Re: CPC Monitors
« Reply #5 on: 11:51, 09 February 18 »
There's a thermal overload in the monitor. You may have just been pulling too much current. It may be working again now if you try it.

Bryce.

Yep - it's working this morning Phew!!! i thought i had knackered it last night overloading it. Lesson learned for the future. :-[
Paul Woakes - Genius & Programmer

Thank you for Mercenary Paul

Offline Gryzor

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Re: CPC Monitors
« Reply #6 on: 20:15, 11 February 18 »
But what do these rejuvenators do? Inject new electrons?

Offline Bryce

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Re: CPC Monitors
« Reply #7 on: 10:06, 12 February 18 »
No, they overheat the Cathode coil which knocks the oxide coating off it, so that it emits more electrons. That's why you need to know what you are doing to use this type of equipment. A bit too much voltage or for too long and you burn the coil through and then it emits nothing.

Bryce.

Offline ComSoft6128

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Re: CPC Monitors
« Reply #8 on: 16:05, 12 February 18 »
Would this return the CRT to it's original lifespan or would it be a short term (a few months) effect?

Offline Bryce

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Re: CPC Monitors
« Reply #9 on: 16:33, 12 February 18 »
What's the expected lifespan of a tube? It depends on many factors, especially how bright you are running it and how clean the supply is. A tube can last many years or in the wrong conditions, half of that time. If done properly rejuvenation could get a significant additional time from the tube. It could also only be done one or twice before the guns were completely used up. After that there was another very complicated process available in which the guns were replaced!

Bryce.

Offline rpalmer

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Re: CPC Monitors
« Reply #10 on: 12:20, 13 February 18 »
all TV's and Monitors eventually give up the ghost.

You can be sure you are left with just two choices when it happens.

1. Find a replacement which can work with the computer (more difficult as time goes by).

2. Modify the computer to use newer technology (AKA us the V9990 card and connect a modern monitor it can support). Or maybe use a scart converter to TV's which have this support (I would note that scart here in Australia is not often seen on modern TVs like LCD/LED).

rpalmer

Offline Bryce

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Re: CPC Monitors
« Reply #11 on: 13:16, 13 February 18 »
It all depends how much you are willing to invest to fix the old tube. Everything is repairable.
Expanding on my answer to @ComSoft6128, here's a video of how the guns are replaced in expensive or rare crt tubes:


https://www.youtube.com/watch?v=W3G7b-DcOO4

Not a simple process!

Bryce.

Offline pelrun

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Re: CPC Monitors
« Reply #12 on: 16:41, 13 February 18 »
It was stressful watching that - I was waiting for him to not lift a tube high enough and whack the neck on the rings he was using to hold them...

Offline khaz

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Re: CPC Monitors
« Reply #13 on: 01:49, 14 February 18 »
On that subject, I have a PC monitor that give a greenish picture at boot, but the colours gradually come back after 20 minutes or so warming up. Would a rejuvenation help me with that problem?

Offline Bryce

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Re: CPC Monitors
« Reply #14 on: 09:30, 14 February 18 »
On that subject, I have a PC monitor that give a greenish picture at boot, but the colours gradually come back after 20 minutes or so warming up. Would a rejuvenation help me with that problem?

No, but a complete electrolytic capacitor replacement would.

Bryce.