Mr. SPC700
Beginner
Hi everyone.
A couple of years ago I bought a Sega Astro City and it came with a Toshiba monitor and a Nanao chassis. The monitor has a label that identifies it as a MS8-29FSG and the chassis has a number: 05A00362G1.
Anyway, it was working OK but I noticed some issues with the convergence and some bowing. Sometime later it began to produce a really annoying high pitched noise (not the normal CRT noise, this was a loud -everyone can hear it, even old people with hearing deterioration- noise).
I then decided to recap it, which I did and when I was done, the noise was gone and it looked OK.
Then, the noise returned and it began to have this issue of turning on (I could hear the monitor "turning on") but without producing an image. I noticed that if I waited and turned it off and on again, it worked. Then that didn't work, I had no image, no static, nothing.
I know the safety basics like discharging the tube or big caps, things like that. But I'm somewhat of a noob when it comes to testing "complicated parts" like IC's, transistors, etc, and knowing what to look for in order to troubleshoot.
So... right now, the monitor is not working. There's no neck glow, no static noise, no static feeling when I touch the front glass.
I took out Q533 (2SC4288A) and tested it, I got a .3something voltage drop in one of the readings so I considered it defective and changed it for a new one that read OK.
I read somewhere that sometimes IC401 (LA7832) can be faulty so I replaced it.
I took out Q901 (C4157, which is the voltage regulator, if I'm not mistaken) and it tested OK with the voltage drops in diode mode with my multimeter. This one was the part that I thought was bad but apparently it's fine.
My board has the same issue I've seen in many other boards which is the burnt area where Q532 (C2611), R542, R541, R540, R539 and C536 reside. I took out all of those parts and put them on a piece of perf board with three cables soldered to where they needed to go. I rechecked my work multiple times, everything is connected correctly. I don't think I made a mistake here, still a possibility though. I tested Q532 out of circuit and had correct voltage drops, I didn't replace it but I bought a supposed replacement. It's labelled C2611T; it has that extra "T" at the end. I didn't find a datasheet corresponding to that exact model so I'm not sure if it's a correct replacement.
I took out Q408 (C3621) and it tested OK. Again, I didn't replace it but I bought a supposed replacement, in this case it has a "Y" at the end: C3621-Y. And again, I couldn't find the datasheet for that.
After all that, I connected everything and nothing. Like I said, no neck glow, no static, nothing.
With everything connected I did a lightbulb test I put one lead of the lightbulb in the fuse and the other lead in the negative leg of the big filter cap (C905). It turned on without an issue. I measured the voltage in the same place as the lightbulb (in fuse and - leg of cap) and got 93.4V. I read that you need +- 94V so I thought that was OK. The B+ adjustment pot was fixed in place with some white silicone or similar, I removed it and carefully turned it up so I could get 94V. Still dead.
It seems weird to me that the lightbulb test works fine. I have the correct B+ voltage but it's dead. I would assume that it should turn on and maybe have no picture, which then I could try to fix but no, it's completely dead.
What else?... The fuses are OK.
Oh! I also took out and tested D530 (C021M-15). This one is a little weird, I don't know if you can test it like a normal transistor. I suppose this is two diodes in one. One reading was .3somethingV. If I follow the testing parameters, should I consider this part faulty? And if so, how can I replace it? I can't find the exact same model to buy.
I reflowed some points on the neckboard, the connectors, the extra boards that stand up.
I really don't know where to go next with this.
What else can I test?
Any advice is greatly appreciated.
Thanks!
A couple of years ago I bought a Sega Astro City and it came with a Toshiba monitor and a Nanao chassis. The monitor has a label that identifies it as a MS8-29FSG and the chassis has a number: 05A00362G1.
Anyway, it was working OK but I noticed some issues with the convergence and some bowing. Sometime later it began to produce a really annoying high pitched noise (not the normal CRT noise, this was a loud -everyone can hear it, even old people with hearing deterioration- noise).
I then decided to recap it, which I did and when I was done, the noise was gone and it looked OK.
Then, the noise returned and it began to have this issue of turning on (I could hear the monitor "turning on") but without producing an image. I noticed that if I waited and turned it off and on again, it worked. Then that didn't work, I had no image, no static, nothing.
I know the safety basics like discharging the tube or big caps, things like that. But I'm somewhat of a noob when it comes to testing "complicated parts" like IC's, transistors, etc, and knowing what to look for in order to troubleshoot.
So... right now, the monitor is not working. There's no neck glow, no static noise, no static feeling when I touch the front glass.
I took out Q533 (2SC4288A) and tested it, I got a .3something voltage drop in one of the readings so I considered it defective and changed it for a new one that read OK.
I read somewhere that sometimes IC401 (LA7832) can be faulty so I replaced it.
I took out Q901 (C4157, which is the voltage regulator, if I'm not mistaken) and it tested OK with the voltage drops in diode mode with my multimeter. This one was the part that I thought was bad but apparently it's fine.
My board has the same issue I've seen in many other boards which is the burnt area where Q532 (C2611), R542, R541, R540, R539 and C536 reside. I took out all of those parts and put them on a piece of perf board with three cables soldered to where they needed to go. I rechecked my work multiple times, everything is connected correctly. I don't think I made a mistake here, still a possibility though. I tested Q532 out of circuit and had correct voltage drops, I didn't replace it but I bought a supposed replacement. It's labelled C2611T; it has that extra "T" at the end. I didn't find a datasheet corresponding to that exact model so I'm not sure if it's a correct replacement.
I took out Q408 (C3621) and it tested OK. Again, I didn't replace it but I bought a supposed replacement, in this case it has a "Y" at the end: C3621-Y. And again, I couldn't find the datasheet for that.
After all that, I connected everything and nothing. Like I said, no neck glow, no static, nothing.
With everything connected I did a lightbulb test I put one lead of the lightbulb in the fuse and the other lead in the negative leg of the big filter cap (C905). It turned on without an issue. I measured the voltage in the same place as the lightbulb (in fuse and - leg of cap) and got 93.4V. I read that you need +- 94V so I thought that was OK. The B+ adjustment pot was fixed in place with some white silicone or similar, I removed it and carefully turned it up so I could get 94V. Still dead.
It seems weird to me that the lightbulb test works fine. I have the correct B+ voltage but it's dead. I would assume that it should turn on and maybe have no picture, which then I could try to fix but no, it's completely dead.
What else?... The fuses are OK.
Oh! I also took out and tested D530 (C021M-15). This one is a little weird, I don't know if you can test it like a normal transistor. I suppose this is two diodes in one. One reading was .3somethingV. If I follow the testing parameters, should I consider this part faulty? And if so, how can I replace it? I can't find the exact same model to buy.
I reflowed some points on the neckboard, the connectors, the extra boards that stand up.
I really don't know where to go next with this.
What else can I test?
Any advice is greatly appreciated.
Thanks!
