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| SE adopt non-original CRT? |
Posted by: 3edd on 2025-07-03 02:10:04
Hello everyone. Some time ago i`ve bought a SE Mac which, unfortunatelly, was broken in transition (the end of the tube snapped off). I can`t find a replacement CRT from where I live so I decided to try to install a tube that *kinda* looks compatible (heater voltage, dimesions, etc) In fact, I`ve tried 2 different tubes: one from an old TV set and one from CCTV monitor. The results were the same in both cases: the tubes somewhat work but the picture is very dim, it barely visible and very washed out. I`ve tried regulating brightness and cutoff on the analog board but it wasn`t helpful, just added a retrace lines to the picture but not made it more bright or contrast. My question is, maybe there is something I have to change or tinker with on the analog board to fix the picture on new CRT? Both CRS`s work well from where they came from. |
Posted by: Callan on 2025-07-03 08:07:19
When you say your doner tubes are kinda compatible how far off is your heater voltage? I believe the se heater voltage is 12v (which threw me at first since most run around 6.3v). If your heater voltages dont match, you oght be having issues with the gun emmisions.. Also, just to confirm,.. Are you using the yoke from the Se? (You moved it from the bad tube to your don't tube). |
Posted by: 3edd on 2025-07-03 23:21:06
Thanks for reply. Yeah, I`ve tried old Russian 23ЛК13Б tube with the 12V heater voltage and, of course, with the original mac yoke.
Here is some pics I made on reddit (the image is not centered there, I`ve made it a bit better afterwards):
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Posted by: Arbee on 2025-07-04 06:30:40
Low brightness I'd suspect the replacement tubes want a different voltage range on the main video grid, although if you can adjust it to get retrace lines it might be that the second anode voltage is too low. |
Posted by: Callan on 2025-07-04 07:04:10
Yeah... I was just about to say the same.
Se tubes run at a super low bias on g1 from what I've seen in the past (-36, I believe). I was using a sencore cr3000 to check out a bunch of tubes and had lots of fun figuring out their settings / pinouts (the pinouts I found in references were incorrect). If you have the data for your transplant tube i'd verify what it's grid voltages are and modify the se chassis to match. If your tube looked good before you started, it should look fine once you match its requirements. |
Posted by: Chuckdubuque on 2025-07-07 05:29:13
The tubes used in the Macs had better specs than TV tubes so the result you have using a b&w tv tube is probably the best you will get.
IIRC Adrian’s Digital Basement did a segment on replacing a Mac tube with a green phosphor monitor tube. Looked pretty cool, and the tube has the characteristics needed for a shape image. |
Posted by: jasonfortheworld on 2025-07-07 06:53:55
The tubes used in the Macs had better specs than TV tubes so the result you have using a b&w tv tube is probably the best you will get.
IIRC Adrian’s Digital Basement did a segment on replacing a Mac tube with a green phosphor monitor tube. Looked pretty cool, and the tube has the characteristics needed for a shape image. I know that the 9 inch green Apple "Monitor" Model G090H is pretty much a drop in replacement for a compact mac CRT. It's something I've been meaning to do myself. |
Posted by: 3edd on 2025-07-07 23:27:30
Thanks everyone for replys, guys, I really appreciate!
Yeah, looks like, this tube is no-go. Yesterday I`ve disassembled the mac again and tried to play with g1 values a bit, hoping, it will brighten a picture a little. I`ve tried to change R22 from 470K to 1K to pull the g1 down more, but, strangely, it made no difference at all. Here is a part of the schematics. |
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