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General Category => Technical support - Hardware related => Topic started by: Audronic on 22:49, 20 November 16

Title: Faulty GT64 Monitor
Post by: Audronic on 22:49, 20 November 16
Hi All


I have a GT64 Monitor (Green Screen) that won't Power the 464 that it comes with.
The Monitor Works well if I power the 464 from an external Power supply.
Are there any component that regularly go faulty for me to look at as a starting point.
Or any hints or Tests to cary out.
Thanks     Ray

Title: Re: Faulty GT64 Monitor
Post by: Audronic on 23:24, 20 November 16
Hi All
The fault has been resolved.


It turned out to be a "Dirty" Potentiometer R501 which gave me about 2.7 Volts initially.
After cleaning the pot it is now set to 5.01 Volts.
Ray
Photos below
Title: Re: Faulty GT64 Monitor
Post by: Audronic on 02:40, 21 November 16
Hi All

Arggggggg  I thought it was to easy ??

The + 5 Volt line sagged to about 2.74 Volts ( More Hair removed ).

BUT i remembered Bryce's comments a while ago about The Dreaded "" DRY  JOINTS "" .
So an inspection of the Board indicated that 7 of the Diodes had " Annular " rings around the Pins.
So Soldered them back with " FRESH " Solder, also some of the Heavy interconnecting leads also had suspect solder joints.
I hope that this is the end of this Project.
If anybody can find where R511 120 Ohm 2 Watt is located on the mother board as i cannot find it ??


Ray



Title: Re: Faulty GT64 Monitor
Post by: Bryce on 09:45, 21 November 16
R511 is beside the fuses and the plug from the transformer, between the row of rectifier diodes and capacitors. It's not hard to miss, it's a pretty big resistor.

Bryce.
Title: Re: Faulty GT64 Monitor
Post by: Audronic on 10:29, 21 November 16
Hi Bryce


Thanks i will have an other look it appears to be not where the layout diagram indicates.
Oh well another look.
Thanks    Ray
Title: Re: Faulty GT64 Monitor
Post by: ||C|-|E|| on 10:39, 21 November 16
Now that you have the board out you can replace the caps and the thermal paste as well  :)
Title: Re: Faulty GT64 Monitor
Post by: Audronic on 10:47, 21 November 16
@||C|-|E|| (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1447)


Thanks I will have a look.


Ray
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