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| Old screen's worn out ? |
Posted by: falen6 on 2023-05-30 11:23:15
Hi folks.
Working on an old SE.
Got the machine working but the display is sooooo bright.
Tried turning down the brightness with the knob under the front panel. At lowest setting the display is still too bright.
So opened it and tried adjusting down the brightness on the analog board. This had zero effect in that it is not working
So I just recapped the analog board and tried again. No change at all. The brightness pot on the analog board has zero effect.
I checked all the solder joints on the pot and most of the rest of the analog board , cant see any problem.
Can these pots break , die
There is a fair amount of screen burn on the display as well so i am wondering do these screens just wear out !!!
anyone ever had this problem ?
cheers people |
Posted by: Phipli on 2023-05-30 11:31:45
I'm not sure if it is your issue, but I'd be interested to know what your PSU voltages are from what you're saying.
If you grab the pinout of the external floppy port, it has 5V, 12V and -12V on some pins. If I remember right, 5V is 5th from the left on the top row, and 12 and -12 are either side of it. Take care not to short anything. You can get ground from the screw lugs on the connector. |
Posted by: falen6 on 2023-05-30 11:40:52
they are a bit off all right but i didnt think they would lead to a very bright screen
-11.56
+12.21
+4.92
+5.05
Stripping it again - im gonna take out the brightness pot and see if the dam thing is broken |
Posted by: s_pupp on 2023-05-30 11:59:58
Related question, and relevant if OP’s pot is bad: Does anyone know of a currently available perfectly sized replacement for the analog board brightness pot? |
Posted by: ObeyDaleks on 2023-05-30 12:21:59
If the cutoff adjustment had no effect, I would suspect some component on the analog board, like cutoff pot, or maybe some resistor etc.
Edit: I didn’t realize the pot has been mentioned multiple times here. Reading is hard. |
Posted by: falen6 on 2023-05-30 12:44:30
have the pot out - seems to be fine - i have no electronics training but with the multi meter on 200m im getting a reading of 3 .... is that a 3 mega ohm pot ? .... when adjusting it reads .9 to 3( guess its output is between 1 and 3 mohm ) ........ pot is fine....... checked traces to next solder joints and they are all good...... i already resoldered the flyback along with all the other big connectors and have gone over all the soldering i can see........ when i recapped it i started with all the small caps around the brightness pot ...... i checked all the old caps values and they were all fine........ infact none of the caps i replaced were out of spec........Im gonna have a look at the soldering on the board at the back of the tube |
Posted by: falen6 on 2023-05-30 13:51:25
checked the board on the back of the tube - no dry solder joints
No idea whats going on with this
The brightness control on the front panel works , but the one on the analog board has no effect. Those 2 are the only adjustments for brightness ? - there are no adjustments on the tube itself ? |
Posted by: Retro_GamerC64 on 2023-07-18 16:02:59
checked the board on the back of the tube - no dry solder joints
No idea whats going on with this
The brightness control on the front panel works , but the one on the analog board has no effect. Those 2 are the only adjustments for brightness ? - there are no adjustments on the tube itself ? I had this issue on a plus, and it was caused by a bad resistor. I don’t know what is is on the SE, but I saw the fix in the dead Mac scrolls. |
Posted by: joshc on 2023-07-18 22:44:57
What tool are you using to adjust the pot? Are you sure its actually moving it? Have you tried the other pots, do they work with the same tool are you are using? |
Posted by: Retro_GamerC64 on 2023-07-19 03:41:50
What tool are you using to adjust the pot? Are you sure its actually moving it? Have you tried the other pots, do they work with the same tool are you are using? It wasn’t a pot, it was a normal resistor. |
Posted by: Retro_GamerC64 on 2023-07-19 05:45:20
Here is a page from the dead Mac scrolls, does this match the issue? |
Posted by: joshc on 2023-07-19 06:05:40
It wasn’t a pot, it was a normal resistor. Try adjusting the cut-off pot on the AB first, this is different to the brightness knob that you adjust when the machine is closed up. |
Posted by: Retro_GamerC64 on 2023-07-19 06:10:17
Try adjusting the cut-off pot on the AB first, this is different to the brightness knob that you adjust when the machine is closed up. I was talking about a plus, trying to help the person with the SE. |
Posted by: joshc on 2023-07-19 07:25:04
I see. My question was for the OP. I got confused as your post followed my question so I thought you were the OP for a moment there. I'll wait for OP to respond about how they're adjusting the pot. |
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