Repairing a CRT PC monitor HP D2846 (Trinitron).

[GeorgeF]

Hi,
I have an old 21" CRT PC Monitor (HP D2846). It's a rebranded Sony Trinitron in a N3 chassis.

Ten years ago when I stopped using it, I stored it in a bedroom in my house.
It was working without any issue.

Last month I tried to turn it on again. Now it has few issues.

First the vertical synchronization doesn't work. The full image is displayed but moving from the top to 1/3 of the screen then goes back to the top. This cycle repeats maybe 2 or 3 times per second.
After 20 minutes turned on, it manages to lock the image in place but only for the 1280x1024 resolution at 75Hz.
The second issue is that the bottom of the image doesn't take the full width.

I want to fix it, I was planning to use it to play retro-games.

I downloaded the service manual (search HP D2846 Service Manual in google), read a lot of websites and watched a lot of YouTube videos about CRT repairs.

Since it manages to synchronize on a resolution once it's hot, I think the most likely is that some electrolytic capacitors went bad.
So I planned to change the electrolytic capacitors of the deflection board (D board).

This is were I need your help.

In the schematic some capacitors are noted HR and/or HT (see image below), I couldn't find out what this means. Do you know?



In the BOM, most (all?) electrolytic capacitor have a tolerance of 20%.
All but C529, which has a tolerance of 0 (see image below). I can't find this capacitor with a 0 tolerance at Farnell nor Mouser.



Is it really a capacitor with a 0 tolerance? Can I replace it with a capacitor with a 20% tolerance?
As I understand, this capacitor is used in parallel with other capacitors that can be "added" or "removed" by the CPU (see image below).
It's related to the horizontal deflection.




Thanks for your help.

Sorry for my bad English.
Best regards.
George.

[inse]

Don’t worry about the tolerance, select one with the correct ratings and size, low ESR favorable.
You can try to localize the culprit capacitor with a hair dryer blowing into the cold unit.
When the behaviour improves, you’re in the right spot.
Just be careful about the voltages that are present!

[T3sl4co1l]

Yeah, don't worry about electrolytic tolerance, they're never very good to begin with.  It is weird that they don't show it on some.

In any case, if it's not utterly obliterated anyway, you can read the type, look up an equivalent, and put in something with comparable or greater temp and lifetime ratings, and similar C and ESR.

At this point, electrolytics are probably the most likely suspects.  Sadly there are a LOT of them in there...

I had one of these, as the HP A4576 (N3 chassis).  Different issues though; one was a cracked solder joint or chip component (intermittent loss of horizontal deflection); the other was generally failing horizontal deflection (reduced or inconsistent width when cold; eventually failing outright, taking out the HOT and a few other things; tried replacing them, only lasted two weeks).

One thing I noticed, at least on mine, not sure it happened every time I guess -- or if yours is a variant with different components -- but the potting in some of the inductors turned to goo over the years, like it was maybe a vulcanized rubber sort of material that devulcanized over the years, turning into a gooey-waxy substance that kind of dripped out and ran down the deflection board.  Very soluble in acetone/IPA, easily cleaned up.  Doubt that contributed to any failures (maybe higher internal operating temp of the inductors?), but just kinda weird.

Tim

[GeorgeF]

Thanks for your help.

I ordered new capacitors and changed them all. I did it in 4 parts.

First I changed the four capacitors that had a very bad ESR. It didn't change anything.
So I decided to change every capacitor that was not a decoupling capacitor on the low voltage side (signal processing), no change.
Then I changed the decoupling capacitors, still the same issue.
At the end I replaced all the remaining capacitors. The problem is still present.

All the caps I bought are 105°C rated. There were 85°C and 105°C capacitors on the board.
I chose Wurth capacitors because they include gummy bears when they send you samples, because they are red and it's easier to see the ones that have been replaced.



It's been a fun week-end replacing the 59 electrolytic capacitors on the board. Too bad it didn't fix the issue.

I did more research on my monitor issue, it seems that the SONY chip CXA2043Q that controls the horizontal and vertical deflection is a common failure on this N3 chassis.
After studying the schematic again, it seems very likely that it's indeed this component that's going bad on my board.

It's hard to find a seller for this chip.

I found two dodgy sites that were listing it. One is a pure scam, the other one seems legit, but with mixed reviews. I'm not even sure they really have it in stock.

There is a seller from the USA on ebay.com. It seems legit, good reviews, but the chip is around 50€ (with $1 = 1€) plus 25€ to ship to the EU. That's 75€ without the import tax.

I don't know yet if I will try to replace it.
I will let you know if I do.

George.

[T3sl4co1l]

Dang, that's a lot of work sort-of wasted.

Have you tried hot or cold, does the behavior vary with temperature of the chip -- or anything else for that matter?

Tim

[GeorgeF]

Have you tried hot or cold, does the behavior vary with temperature of the chip -- or anything else for that matter?

I didn't try, I didn't want to work with live current.


I have changed the CXA2043Q this week-end.

First I bought the chip on aliexpress for 25€. The seller never sent the order, and it cancelled itself after 30 days. So I decided to buy it from eBay US for 75€, and I received it around 20 days later.

To replace the chip I had to desolder 9 capacitors around it. Then I used my hot air station to remove it, and I solder the new one in place.
To be sure I won't mess it up, I had bought a practice board to train to desolder and to solder back.

Now the problem is fixed, and I can use my monitor for retro-gaming, as I intended to do.


The chip removed:


The chip changed:


The issue before:


Monitor fixed:


Training board:

[SeanB]

Would suggest then getting a stick on heatsink for that new to you chip, as it likely fails because it runs hot, so a stick on heatsink will probably help improve the lifetime of it in future.