Sony KV-34HS420, blinking standby light

[Freezer]

I have a Sony KV-34HS420 with blinking standby light. This TV is a widescreen CRT with full 1080 resolution and HDMI input. I personally think the image is as good as any LCD or plasma. The problem is the set won't turn on. When you apply power the standby light on the front starts flashing. Most of the time it flashes 6 times, but sometimes it flashes 7, and one time it flashed 4.

I know this era Sony TVs has a systemic problem with two ICs on the DZ board. The replacement part is the MCZ3001DB, easy to find on eBay. These chips are marked "A" in the attached picture. Sony recommends replacing two fusible resistors (B) and two capacitors (C) at the same time. I have an ESR meter and my caps tested fine, so I did not replace them. But I did replace the fusible resistors (part number 120293361 - .1ohm 1/2watt fusible resistor). The final part I replaced is IC5004, a STV9379A. The service manual recommends replacing this part for 4 blink codes. And since I got a 4 blink code once I figured might as well do the work while I'm in there.

I'm by no means an expert when it comes to working on CRT TVs. I know they can have very high voltage with the real potential to injure or kill. The tube is supposed to self discharge when turned off and unplugged. I left the TV in this state for days to ensure it's discharged - but even still I was very careful. To remove the DZ board, first remove all the screws. The tricky one is located near the front of the TV. It's hard to see and access, so be patient. Next, the clips connecting the DZ and A boards need to be removed. They swing up like a draw bridge (hinged on the A board side) and require a decent amount of force. Finally, remove the wires from the DZ board. This will ALMOST free the SZ board. The problem is the FBT wire to the anode cup on the tube itself. Some people disconnect this, but I've heard you're just as likely to damage it, so I left it connected and worked on the board while it's still connected to the TV. Just kind of prop the board up against the TV.

Replacing all the parts was relatively straight forward, at least if you have a lot of experience with a soldering iron. I'm convinced one or both of the MCZ3001DBs were bad but there's no way to test. My guess is the STV9379A was good and didn't need to be replaced, but the part was only $2. As for the fusible resistors, one of them was definitely bad. I don't know the official way to test a fusible resistor, but I just used the resistance setting on my multimeter. The two new ones measured about .3 ohms. One of the old ones measured at .3 ohms, but the other measured at something like 10 Mohms. So I'm assuming that means it was bad.

I got all five components replaced, put the board back in, and (with fingers crossed) turned it on. Success! It's alive again.

I wish I could say that was the end of the store, but alas there is a minor problem with the image. About 1/3 of the way down the screen there is a single horizontal green line, red line, and blue line (each about 1/4" apart). These lines run the full width of the screen regardless of input of video settings. The service manual has several pages with instructions on how to properly dress the cables to prevent image distortion. It also has a section on calibrating the TV. I need to go through both of these. But first I wanted to post the problem here and see if anyone else has run into an image problem like this. Any ideas what could be causing these lines?

[Freezer]

Re: Sony KV-34HS420, blinking standby light

I think I can answer my own question here. If you read the service manual for this (or other similar Sony CRT TVs) they have 3 areas to check; cable dressing, physical calibration, and electrical calibration.

1. Cable Dressing
Since CRTs generate magnetic fields and have really high voltages in them, the placement of certain wires inside the set can negatively impact the image. To remove the board and solder in the new parts you have to disconnect some wires and move others. So make sure to follow the cable dressing section to get all the wires back into place.

2. Physical Calibration
This step involves a lot of tweaking of the "gun" alignment. I think these steps must be followed if you replace the tube itself, or any of the boards on the back of the tube that control the "guns." Since I didn't do this, I think it's safe to skip this.

3. Electrical Calibration
This final step is done with the TV turned on and using the remote control to navigate the hidden service menu. There are easily 100 or more settings than can be controlled in here, everything from pincushion to colors levels to HDMI version.

The electrical calibration is where you need to go to fine tune the TV after replacing the chips. Figuring out how to navigate using the remote, change values, and SAVING the new values takes time. I only wish I knew what I was doing first. My first idea was to completely wipe the flash RAM in the TV thus restoring factory defaults. Big mistake, the factory defaults don't even know what model of TV this is. Fortunately the service manual includes the defaults for this model TV. So now it's a question of can I successfully program these 100 or more settings and restore them to what they should be. Then change the one or two values that move the position of those lines? By clearing the memory first instead of RTFM I created a ton of work for myself.