17-03-2024, 12:58 PM
At the NVCF in May 2022 I picked one of these monitors from Jeffrey with the intentions of converting it to 405 lines. Jeffrey supplied me with step by step instructions on how to do the conversion and also a setup procedure. It went straight to the top of the high priority pile but it is only now I am getting round to it.
Before I did any modifications I thought it best to check that it was still working OK on 625 lines. After switching on and waiting for sometime a dim unlocked picture appeared it was only one third of its height and width. So it obviously didn't enjoy the sheep it had for the last two years.
The 30V rail was down to 12V. Z1 a 4.7V Zener diode that provides a reference voltage for the power supply had just 1.8 V across it. C2 470uF which is in parallel Z1 was gone very leaky. Replacing it brought back normal operation.
I had to remove the main PCB to replace it. While I had it out I spot checked some of the other electrolytic capacitors. Some were OK, some were high ESR, and I found another low capacitance/leaky. So for reliability I decided to change all the original blue philips electrolytics. Some had been replaced already.
I followed Jeffrey's instructions to convert it to 405 and now I have a working 405 line monitor.
Everything went to plan. After doing the mod I couldn't set the 27V supply with P1 . I could only get to 25V with P1 at one end of its travel. R27 which is across P1 and is a AOT part was 6k8. It was marked as 15K in the diagram. I replaced it with 12K and this gave good range to P1.
As a final step I did fit a buck transformer as in the instructions to reduce the mains voltage.
The picture it displays is really superb. I have nothing that comes anywhere near it.
It is a great addition to the workshop and I am sure it will get plenty of use.
The photo does not do it justice.
One thing I am curious about is the red lamp on the front panel. What is it for? The wires from it goes to the rear panel. Possibly to a 3 pin connector.
A big thank you to Jeffrey for the monitor and also for sharing how to convert it.
Frank
Before I did any modifications I thought it best to check that it was still working OK on 625 lines. After switching on and waiting for sometime a dim unlocked picture appeared it was only one third of its height and width. So it obviously didn't enjoy the sheep it had for the last two years.
The 30V rail was down to 12V. Z1 a 4.7V Zener diode that provides a reference voltage for the power supply had just 1.8 V across it. C2 470uF which is in parallel Z1 was gone very leaky. Replacing it brought back normal operation.
I had to remove the main PCB to replace it. While I had it out I spot checked some of the other electrolytic capacitors. Some were OK, some were high ESR, and I found another low capacitance/leaky. So for reliability I decided to change all the original blue philips electrolytics. Some had been replaced already.
I followed Jeffrey's instructions to convert it to 405 and now I have a working 405 line monitor.
Everything went to plan. After doing the mod I couldn't set the 27V supply with P1 . I could only get to 25V with P1 at one end of its travel. R27 which is across P1 and is a AOT part was 6k8. It was marked as 15K in the diagram. I replaced it with 12K and this gave good range to P1.
As a final step I did fit a buck transformer as in the instructions to reduce the mains voltage.
The picture it displays is really superb. I have nothing that comes anywhere near it.
It is a great addition to the workshop and I am sure it will get plenty of use.
The photo does not do it justice.
One thing I am curious about is the red lamp on the front panel. What is it for? The wires from it goes to the rear panel. Possibly to a 3 pin connector.
A big thank you to Jeffrey for the monitor and also for sharing how to convert it.
Frank
