Riddled TV Repair Forum

r0ck · Joined: 18 Sep 2008 Posts: 5

I have a Toshiba 50A60 projection set. When the unit is plugged in, I can hear the relay click and the set start to power on. Then the relay clicks off and the red power light on the front flashes over and over.

Researched here, and figured the convergence chips were fried. I've searched every square inch of the board for any burnt components with no luck. The six resistors below each convergence chip passed visual and ohms tests. I changed both convergence chips but the same problem happens. Now I'm not sure what to look for. Something in the power supply section maybe?

I have a copy of the schematic but troubleshooting televisions is not something I've tried before. Any help would be appreciated.

Thanks in advance!

Google

r0ck · Joined: 18 Sep 2008 Posts: 5

Well, after letting this TV collect enough dust, I've decided to try again. I've read a couple other posts regarding Toshiba sets with identical problems, and I'm hoping this may fix it.

The repair in question is replacing Q306 and adding countermeasure diode D310. Instructions are based on info discussed in the following post:
http://www.riddledtv.com/forums/toshiba-51h84-wont-power-up-t1175.html

So, anyone have anything to add to this? I realize my TV and the one discussed in the link are two completely different models, but according to my schematic, I do have a q306 and the part is the same as discussed above.

Hopefully someone more knowledgeable will chime in. Thanks!

r0ck · Joined: 18 Sep 2008 Posts: 5

For reference only: No dice.

Even though the service manual parts list shows this model as having Q306, it does not exist on any of the boards. This part (Toshiba TA75902) isn't present on the 50A60.

Back to the drawing board.

curt wolfe · Joined: 24 Feb 2009 Posts: 51

q306 is a ic ta75902 and toshiba # a6335470.

r0ck · Joined: 18 Sep 2008 Posts: 5

I realized that just after placing the order for the part. :oops:

The 14-pin IC TA75902 is listed in the service manual as being used at Q304 and Q306. However, after ordering the replacement, I decided to actually try to locate it on the power/deflection PCB. It wasn't there. It wasn't on any of the other boards either.

The only 14-pin IC used on this model appears to be TA75339 at Q481. Oddly enough, this IC already has a zener attached on the underside. Yep, the diode checks OK, but not sure about testing the IC.

You stated that q306 is a TA75902, but the part # you gave is for a transistor 2SC2712-Y, used at Q303, Q308, and Q310. Are you suggesting that these transistors may be the cause of my problems?

Thanks for taking the time to respond. I really appreciate it!

Google

r0ck · Joined: 18 Sep 2008 Posts: 5

Ok, here's an update. Turns out there IS a Q306 used on this chassis. It's on the board with the convergence chips, not the power board. . I missed it because I was looking for a 14-pin DIP IC, not a 14-pin surface mount IC.

So, I ended up ordering the wrong part. It is a TA75902PG that is referenced in the other post. I actually needed a TA75902FD, which is the surface mount package. Andrews Electronics carries these as part #70129117.

I will try the repair with this part once it arrives. Will update afterwards. Again, if anyone can offer help or suggestions, it would be greatly appreciated.

Thanks!