Hello everyone,

I'm working on a small black and white TV set. It's a small chinese thing, probably 9 inches. Not new not old. I'd say maybe late 90s or so. Not really a collectors item or anything but since I've started really getting into and learning about TV circuits I've been repairing them left and right because I really find it enjoyable. It's also for my uncle who needs it in his store.

My problem is the following.

The TV originally did not have any sound, that issue was fixed with some re soldering.

Next the issue was that this thing will not shut off and the image looks a bit squiggly. I noticed the flyback transformer warms up as well.

I have found two bad transistors. One is the horizontal output transistor which is leaky between two pins. At first I considered that this "leak" could be a built in damper diode but I highly doubt it as the voltage drop reading on my meter read above 1.8 which is unusually high for a damper diode. The set not shutting off seems to be due to a bad power transistor. This transistor's emitter is directly connected to the B+ line. Trust me, it's not the switch or anything like that. I even completely took it out of circuit and the TV still will not shut off. What the switch "switches" is an "A+" line which I assume works as a wake up line for the power circuit. This transistor is completely shorted.

My problem is these are some weird numbers on these transistors. Probably just cheap Chinese branding.

The power transistor is "CD834". I do not know if this is a PNP or NPN but since the B+ attached to the emitter I assume it has to be PNP. Would this transistor be the same as B834? B834 is a power transistor and is also PNP. Keep in mind that this is a small 12VDC set that runs off a wall-wart. Even if it's not the same I assume it would work correctly.

The horizontal deflection transistor is a D949. This one is a bit trickier. I can't find info on it either. I thought it could be 2SD949 but that seems to be a much bigger transistor than this one. It's in a TO-3 case and this is a TO-220. However this is all probably very generic type circuitry and probably any common small horizontal output transistor will do. I would appreciate any good numbers.

Thanks for your patience and attention. Any and all help is highly appreciated as always.
-Carlos

Hey fifties, I gave it a shot but it says searched failed.

Thanks.
-Carlos

Went with the B834 and a 2D1159 horizontal transistor from a slightly larger, much older, yet pretty similar in circuitry television that I had lying around. Unfortunately that one has a broken neck.

Television works great! Audio cut out again soon after I got the image going correctly and it turns out I have a bad volume pot. I replaced it with a temporary one with a different physical build. Will be getting the proper replacement tomorrow at the local electronics shops.

I had an image with a terrible ripple across it, the squiggly image as I referred to it in my first post. The ripple was horizontal and distorted the image like corn rows. The problem turned out to be a small 1uf @ 16V electrolytic capacitor related to the video IC. After replacing that the image is crystal clear!

I will be going over the circuitry one more time tomorrow, with special attention to the voltage regulation where I placed that B834 to see if it's regulating correctly. I assume it is. Oh and it now shuts off properly too!

Thanks again and I hope this info helps someone out there.

Ahh I love fixing stuff!

Probably the first Chinese TV that has been repaired, instead of heading to the landfill.

Haha Yeah not to mention it's black and white!

Around here people still like and need to get stuff repaired. In fact judging by the looks of the solder joints on some of the transistors I replaced, this thing may have already been repaired once before!

Check it out!



Really for me it's not about what the item is worth or anything like that for the most part. I just thoroughly enjoy the process of trouble shooting something and most importantly the rewarding feel of fixing it! Every repair is a great learning experience!

Next is a nice vintage Philips danubio television. Also black and white and made in Mexico. I think I'd say circa 1970.

Glad to hear that you got it fixed!

I too will sometimes spend hours working on a radio or whatever that ain't worth ten bucks, just for the satisfaction of getting it working again.