MS8 26SG focus issue

[mukurop]

I got this chassis on an aero city, the monitor have a great picture, the chassis was already recapped and after that have a perfect geometry but have a weird issue with focus: basically on first start up it takes 5 min to get a perfect sharp picture .
if the cabinet is turned off and on again it maintains the same level of focus but the problem recurs if turned off for a few hours. I'm sure this problem does not concern the tube because changing chassis I have no problem. I have already checked the neck board and at least on the pcb no problem but there may be something wrong with the socket ,possibly something inside oxidized that I can't see externally in any case I will try to change both the neck board and the Flyback, if you have further advice I would be grateful

[grantspain]

replace the socket

[mukurop]

Replacing the socket solved this issue, I have also carefully disassembled the socket with issue and cleaned with wd40 reinstalled and now is well working!

Before performing this I have swapped the flyback, and it was the same so the flyback was good, I remember that had s Flyback with focus pot issue on a sony trinitron kx 29 but in this case the focus was just drifting itself, this was sorted out by replacing the flyback.

[nem]

That's interesting. I have a tube that does this too. I guess I'll try cleaning the socket and see if it helps.

[mukurop]

May I Know ho ro wire a Degauss button? the SG is different frorm SU, Here I have two wires only wich are directly soldered on pcb under PTC,, autodegauss is not working and wiring the two Red wires to a switch button do not work.
I have opened the ptc it is in very good condition I'm 100% sure that it is ok, any advice?

[thegreathopper]

I am not sure of the model number but a couple of the MS8 26 monitors I have had you need to put power directly on to the degauass terminals on the chassis.

[thegreathopper]

What is PTC?

[mukurop]

Ptc=posistor, (Positive temperature coefficient) is the Little black plastic box with two or three pins, it control the degauss on every crt monitor/tv. On ms8 26sg it is directly connected to the ac line on ac line distributor inside the aero, on one wire is placed a switch button for manual degauss.
You can do the same on ms8 26su but on SU you can also directly wire a button to the connector on pcb (a jumper on same conn is needed) .

[PrincessPrinPrin]

May I Know ho ro wire a Degauss button? the SG is different frorm SU, Here I have two wires only wich are directly soldered on pcb under PTC,, autodegauss is not working and wiring the two Red wires to a switch button do not work.

If it's the version without the 5-pin header you need to cut traces and jumper points if you want a degauss button. If you post a pic I can show you.

[mukurop]

The MS8-26SG NOT have the 5 pin header like the SU.
On this board there are just the two Red wires directly soldered on pcb and coveed with rtv White silicon.

[PrincessPrinPrin]

As I said the only option is to hack the chassis.

[mukurop]

I want restore the original degauss, I have already tested every component on degauss circuit and all is fully ok, now I think that the two wires just need to be connected to AC 100v but still need to know where place the button for manual degaus

[thegreathopper]

I want restore the original degauss, I have already tested every component on degauss circuit and all is fully ok, now I think that the two wires just need to be connected to AC 100v but still need to know where place the button for manual degaus

Yes that’s correct and you can just put a switch in series with one of the red cables

[mukurop]

And yes you are right, it works! Maybe there are more revision but on this ms8-26sg there is only a manual degauss not auto...and must be wired just as your advice.

[copados33]

basically on first start up it takes 5 min to get a perfect sharp picture .
if the cabinet is turned off and on again it maintains the same level of focus but the problem recurs if turned off for a few hours.

And what if this same problem happens when trying with different chassis but same tube?? what could be causing this?

[mukurop]

Then should be a weak or tired out tube, usually also the contrast is not good on those tubes.

[copados33]

hmmm, contrast and brightness in this tube is very good, once it heats up I daresay its one the best MS8's I have ever seen..

[mukurop]

Desolder and Disassemble the socket and clean or better just replace the socket with a new one.

[copados33]

You talk about the socket on the neckboard? I don't think that is the problem because I have tried with 5 different chassis and it does the same with all them, x4 MS8-29 and a MS9, these chassis work fine on other tubes, picture is sharp right from the start.

As I said, the contrast and brightness in this tube is just fine, its just that it takes 2-3 minutes to show a sharp picture.

[mukurop]

You should not try a ms8 29 or ms9 chassis on a Mitsubishi 26" due to the yoke not match.. Any way if it is not the chassis then is the tube and on my experience a tube rejuve do not any reliable results on those tubes (Both 26" mitsu and toshiba 29") so you should replace the tube ..