Question about Toshiba TP50H95 50" Rear Projection Television

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Toshiba TP50H95 Convergency problem.

30 mons ago, one of the color was blend (non-linear) across the screen. I got it repaired for $200. The repairman just told out the PCB from the back to shop. I was supriced the PCB looked pretty simple and no where near as complex as an PC Motherboard, just with many cables. Today, I notice the whole red color is shifting up (horizonalty/ & evenly across the screen). The chip is trying to compensate so the red will move up slowly to like 2 inches higher and then pop down back to where it should be. It will keep doing a for a short while..ASo far, once it warm up (a fews minutes), the TV image will stable. I am very handy in electronics and have built my own CB in the past. Is this something obvious I can take care the repair myself after I told out PCB from the TV. Changing, QFP, SIP,...,etc is not a problem. Appreciate your experience. Just want to hold this nice TV (98 vintage) for a few more years before switching to HDTV. It is good for the earth !

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  • 2 more comments 
  • Victor William Sep 04, 2007

    I opened up the back cover and hestiate a little. There are many circuit board inside.
    I guess the convergency board was the one with the biggest heat sink and with the 3 "dist Caps" (it is kind of like car distirbutor cap).

    It can still adjust the red "cross" by using the remove control. Does it mean it is some of the cap/resistor go bad or it is still the SKT IC went bad. I read other post, that when the IC wnet bad, you cannot move the "red" at all.

  • Victor William Sep 05, 2007

    I found the PCB with two STK392-110 mounted to big heatsink.

    Do I unplug the convergence wires or remove the whole "scan yoles cap" from the PCB? Any specifcs items I should "discharge" with a screwdriver.

    My best practise is either discharge (a few times) and "insulated" those high voltage wires and keep them away from work area.

    On the last repair, I don't recall I saw "scan yoles cap" on the PCB when they took it out.

  • Victor William Sep 07, 2007

    Thanks for warm support. I ordered the STK -150, instead of 110 (a better spec part) The convergence seems to stablize after the TV warm up for short period. There is more air flow in the back where the TV sit right now. A weeks ago, it was unpredictable. Still something is not perfect and can go back anytime again. I attached a picture. The PCB in the middle is the STK Converg. board, the PCB on the right seems like the one with scan yole cap. This was connected to the another cap on the converg. PCB and with 3 others red wires (to the lens/gun).

    What is the best practice of removeing the red(HV) wires:
    1) Just disconnect single wire at the Converg. PCB first or at the scan yole frist. keep the wire out of the the way.
    2) After that remoove the set of 3 red wires.

    Also, the red wires should be that last set (or the 1st set) of wires I touch, besides AC power.

  • Victor William Oct 10, 2007

    Thank Chris...

    Finally decide to go through the work to  replace the STK-150.  I left the TV unplug for a few hours.  There is no discharge or spark when I shorted   the "high voltage" wire   as suggested - always good to be safe.    It seems there is internal discharge ckt buit-in.


    No bad cap or burned resistor.   Everything works great after changing both ICs.   It looks like I will be watching this old big TV for another 10 years... as long as long I  can keep fixing it every 3 or 4 years.  I really don't mind... Expect the IC would go bad in 3 or 4 years...


    Learned to get a better airflow to the back of the TV.......




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Hi. The covergence Ics are mounted on large heat sinks they usually start with STR**** You will need to replace both & check resistors electrolytic capcitors & any circuit protecters on the same pcb as the chips.

Posted on Sep 02, 2007

  • 2 more comments 
  • chris pursloe
    chris pursloe Sep 04, 2007


    Please stop dont do anything.
    DO NOT TOUCH THE ITEMS YOU SAY LOOK LIKE ENGINE PARTS these may hold large voltage even when switched off.
    The Ics are approx the size of a zippo lighter.
    There are only 2 of them they control red,green,& blue, The convergence pcb has 3 sets of plugs that have a group of 4 or 5 wires in each these wires go to the scan yolkes (transformer windings) of each of the crts find these plugs they will be close to the Ics.
    If you dont feel confident
    Probably best that you put the tv set back together & check with repair shop how much to repair for you.

  • chris pursloe
    chris pursloe Sep 05, 2007


    No do not remove scan yokes Or even attempt to.
    If you can get at the STK Ics desolder them & carefully lift them out once you have unscrewed them from the heat sink.
    If you do need to unplug any wires from the Pcb in order to desolder STK ics either lable the plugs & sockets so you know exactly where they go take digital photographs etc.
    If you are able to use a meter check resistors & any cps, Look for any bulging capacitors they will need replacing. All these components are very close to the STK ics.
    To be honest I am not 100 percent familiar with your tv set as it is US version I am in the UK
    but in saying that your Projection set will be very similar to what I normally work on.
    Let me know how you get on.

  • chris pursloe
    chris pursloe Sep 07, 2007

    Great picture.
    Ok The thick red HV wires which go up to the anode caps of the crts are the leads which may hold a charge try disharging using 2 screwdrivers slide 1 under aqua dag braid & slide second under anode cap bring both screwdriver shafts together to discharge.
    Now I normally remove all the grey & white plugs from convergence pcb, As is said earlier yours is a little different to what I work on the convergene pcb is smaller than yours so I normally remove the screws holding pcb in place
    remove all plugs from sockets & swing the board out I dont normally disconect the HV leads as there is enough room to work on the board stood up on its side.
    Looking at your picture the pcb is large & runs right down to the front so you may need to disconect HV leads from the rear of crts after you have discharged,
    You can take them directly off of the crt if you can get at them easily enough.
    Ot try to unplug them from focus/trippler unit this is the large transformer on the left of your picture.
    You will need to remove red HT lead from the loptx the one you have circled on picture tranformer on the right,
    You dont need to remove board completely from the set, Providing you can get at the print side of pcb with soldering iron to desolder both Ics you will be fine, remember to look for any bulging caps & any resistors that look like they have got hot.

  • chris pursloe
    chris pursloe Oct 10, 2007



    Im really pleased you managed to do the work.

    Thank you for leaving feedback.

    Other than the convergence problems the sets are pretty reliable & as you said you may only need to do it after 4 years or so.

    Air flow is very important it is the heat that takes the 2 ICS out.

    I fitted a small fan in the back of my projection set touch wood its been going for years.

    All the best Chris..



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It sounds like intermittent loss of convergence and you should be able to cure that by taking a look at the convergence amps and locating one or more ring-cracked solder connections. Resoldering them should fix the problem. The amps are two STK392-110 Sanyo Ic's mounted to an aluminum heat sink. Remove that board and visually inspect where they solder to the foil side of the board.
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PS I'll send the manual via Pando to your address. You'll need Pando to download it and a PDF reader to view it. Both are free downloads if you don't already have them....

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