madlabs
12-11-2016, 02:17 PM
HI All,
Well, I finally got around to hooking up the 21FAP4 to my Predicta Holiday, chassis G4242L. I got it a few months ago from the ETF and is supposed to be NOS. No sign of wear on the anode or pins, so I think it is. The only change I made was that I swapped G1 and G2, which are pins 2&3 of the connector that plugs into the chassis. It works but...
First, an embarassing admition: I connected the video output wire to connection point 19 instead of 20. Ooops! I had no brightness control. All the other controls worked. It was like that for a few minutes. Once corrected the brightness does function but...
The picture is dim and blurry. Constant retrace lines. Contrast and brightness do work but not much range and it doesn't get very bright. The yoke I am using is a little damaged but it worked a week ago just fine, at least in terms of brightness etc. Hard for me to test the pins on the CRT directly as it is face up on the bench. I decided to check the video output voltage as it is directly involved with the brightness circuit, but I can only check it on the board at point 20 and I see 300ish volts! Now, it is supposed to be measured after L14 and be 35V. I've never checked it before but this chassis was playing Honey West last night on a different CRT.
So, is it possible that the tube just needs some time to wake up? Or am I not meeting some electrical criteria? Or is this tube a bust?
Well, I finally got around to hooking up the 21FAP4 to my Predicta Holiday, chassis G4242L. I got it a few months ago from the ETF and is supposed to be NOS. No sign of wear on the anode or pins, so I think it is. The only change I made was that I swapped G1 and G2, which are pins 2&3 of the connector that plugs into the chassis. It works but...
First, an embarassing admition: I connected the video output wire to connection point 19 instead of 20. Ooops! I had no brightness control. All the other controls worked. It was like that for a few minutes. Once corrected the brightness does function but...
The picture is dim and blurry. Constant retrace lines. Contrast and brightness do work but not much range and it doesn't get very bright. The yoke I am using is a little damaged but it worked a week ago just fine, at least in terms of brightness etc. Hard for me to test the pins on the CRT directly as it is face up on the bench. I decided to check the video output voltage as it is directly involved with the brightness circuit, but I can only check it on the board at point 20 and I see 300ish volts! Now, it is supposed to be measured after L14 and be 35V. I've never checked it before but this chassis was playing Honey West last night on a different CRT.
So, is it possible that the tube just needs some time to wake up? Or am I not meeting some electrical criteria? Or is this tube a bust?