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Test Equipment Anonymous (TEA) group therapy thread
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med6753:
Next project. 465B PSU re-cap. Just like the 475A done a few weeks ago the Trigger board has to come out for access to the capacitors. And just like the 475A it's all modular except for two soldered wires so removal is easy and painless.



The capacitors exposed. Only 5 cans vs 6 cans in the 475A. Reference voltage is different too. +55V for the 465B vs +50V for the 475A.



I went back and looked at the repair history on this 465B and it has a checkered past. I replaced ALL the tants on the Vertical board as well as a few key ones on the main board. The CRT had to be replaced since it had poor focus.

Won't be able to pick up again on this project until early next week.
bd139:
Good write up as always  :-+

Might have to refurb this 465B yet. Still waiting for that IC to turn up.  Hopefully today. If it checks out I’ll do a full clean and cal on it and sorted.
Vince:

--- Quote from: Zoli on July 07, 2022, 06:06:33 am ---
--- Quote from: Vince on July 06, 2022, 05:58:52 pm ---...
As for DMM's, I don't have fancy modern ones that can test white LEDs.
...

--- End quote ---
You don't need a new and fancy DMM to test the LED's; as example, my DMM870(1998) gives 3.2v,  and the 8060A gives 8V in diode testing mode, both enough to light up any LED's.
That's why I've asked to check your multi-meters, so next time you will know which is suitable for LED testing(is part of "Know your tools" training)  >:D :-DD :-DD :-DD

--- End quote ---

Thanks, I do have a Fkuke 8060A !!!  :D

It's buried in storage currently, can't dig it out, too much work, but I will keep that in mind  8)
Vince:

--- Quote from: Robert763 on July 07, 2022, 06:56:09 am ---
--- Quote from: mnementh on July 06, 2022, 07:22:41 pm ---
--- Quote from: Vince on July 06, 2022, 06:48:13 pm ---
--- Quote from: Specmaster on July 06, 2022, 04:24:34 pm ---
--- Quote from: Vince on July 06, 2022, 04:04:32 pm ---TV REPAIR


--- End quote ---
Make sure if you are able to resurrect the other strings, that your friend is well aware that he might actually spot areas of his screen that are dimmer than others, in the areas with the dead LEDs, otherwise he might not be happy with you. Short of replacing all the strings, I can see no way around that problem. Great work so far, keep it coming.

--- End quote ---


Well yes if I manage to fix the thing I will see if the lighting is even enough to be acceptable, i fnot will tell him what he wants to do.

Hopefully there WILL be dark spots and he will tell me OK fuck you can keep it... more spare boards/parts for Vince !  >:D

We shall see.

I don't know where to buy the strings nor how much that costs. If it's available for this particular TV, and is ridiculously cheap including shipping... like 20 Euros shipped, and given the TV is recent, maybe he will want to pay for that. We are not there yet....
--- End quote ---

Why the eff would you trash an obviously repairable TV like that? Just put it away and wait for a paycheck so you can buy some LEDs for Ifni's sake. You really should replace those LEDs anyways, even if you are sending it back to the owner. Just jumpering them out is begging for all the others in the string to fail prematurely.

Correct repair, short of replacing them all, would be to measure voltage drop across every LED with them lit up and replace any that read appreciably lower or higher than the average. That would be your best chance to avoid recidivism. You already have a cheap hot-air rework station, right?

mnem
 :-/O

--- End quote ---

These LEDs are driven by an active constant current source. Shorting out one or two does not stress the other LEDs in the string. It does affect the CC driver but probably not enough to reduce it's reliability.

--- End quote ---

Yes and no. There are 4 strings but the driver has only two outputs, so they wired strings in 2 parallel pairs : string 1 and 2, and strings 3 and 4.  So the chip can only regulate the overall current in a pair but has no clue about how the current splits between the two strings in a given pair. So if you remove one LED then there is an imbalance that the chip can't know about nor act upon.
I assume that's what Dragon had in miind...

In my case I am "lucky" in that I have one failed/bridged LED in each string of a pair, so they still have the same number of LEDs each !!!  >:D

Specmaster:
Currently, sitting here waiting for the workmen to arrive. We are having the bathroom refitted and were told that they would be with us this morning at 8.00AM, now 8.54AM and still sign of them. The job is supposed to take upto 2 weeks, thinking of taking friendly bets on the completion date  :palm:
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