QWERTZ-tek = Sony BE-1 chassis

$C:\>QWERTZ-tek_$

- ! Safety warning ! -

This device uses several thousands of volts to operate, enough to cause electric shocks even if unplugged.
Do not perform any kind maintenance or repairs if you aren't experienced or trained to work with high voltage.
Do not open devices with high voltage warnings if you don't know any safety precautions.
The picture tube contains a vacuum that could implode if abused and mistreated, the flying glass shards can cause serious injuries.
Nobody here is responsible for any damage caused by unprofessional actions.

- Sony KV-M16D -

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This model was introduced in February 1989 and is build upon the BE-1 chassis which was the beginning of Sony's new technology for the small European mono-sound TVs with the newly introduced Black Trinitron tube and used the newest state-of-the-art Integrated Video Circuits for unmatched reliability and performance.

The incorporated parts are:

I've gotten this specimen at the beginning of 2020 , the frontdoor had the usual snapped off hook and someone in the past cut out R602 560K 1/2W and replaced it with a 100K 3W resistor and soldered that onto the underside. I left that crappy repair as is because it didn't caused any problems (yet).

I fixed the frontdoor by replicating the missing hook with a small piece of plastic (leftover stem from 6mm potentiometer) and grinded that into the right shape and then carefully superglued it together.

I went through the trouble of doing it all over again as the purity became so problematic that I've sticked some magnets on the outside cabinet to get rid of the color splotches.

In the end I also added two additional convergence strips.
I followed this *guide* but used some solid thick paper from one of these dumb ads that so many online shops throw into the parcel before shipping.

The purity adjustment on the upper right corner is a little too strong as the geometry is noticeably distorted there but at least the colors are spot on.
I rather leave it like that as I can't really notice it during regular use.

Getting the dynamic horizontal convergence on the left side perfect seems to be impossible.
I tried my best. This time the whole attempt only took me 2,5 hours.

A small amount of hotglue was used to fixate the convergence rings. And 4 magnets were added to the back of the CRT and one in the corner of the case to improve the purity.

The STR54041 runs pretty hot and the heatsink is ridiculously undersized. On the newer BE-2A chassis reuses the exact same regulator circuit but has a heatsink twice as big.

Never the less, I've made some attempts to improve it but there's not much room for safe extensions. There's not much space above due to the CRT and sideways is already the "cold" side. That heatsink is connected to the negative of the rectified mains capacitor and is live/hot and MUST NOT COME INTO CONTACT WITH THE COMMON GROUND or else things could blow up before the breaker pops.

What unfortunately happened between 2021-2022 were 5 failures.
The only working fix was to replace the regulator and I used whatever I could get my hands on, so some pulled STR58041 and STR59041 from unknown sources were substituted.
But I couldn't believe that these new replacements just went bad after 2 months, so I looked at everything else and I even swapped the flyback over from an other Sony TV, just to make sure . R602 was also replaced with the correct part.

All the bad regulators failed in weird ways ranging from totally dead, producing overvoltage (destroys D611 or PS802) and getting unstable after warm-up.
It was after the 4th replacement that I discovered that the insulator foil was cracked and I've previously covered that with thermal compound for maximum cooling that's why I couldn't see it.
So a gray rubbery replacement along with a new part was installed, and some 5 months later it failed again and burned the huge R601 3.3ohms 10W power resistor out before the 3,15A glassfuse could blow.

At that point I was starting to lose my fucking mind over this as my other Sony TVs with the BE-2A chassis never ever exhibited this behavior.

So, I've said to myself "fuck that shit" (out loud) and attached a motherfucking fan to the groundwire around the CRT soldered it directly to 12V powerrail with a resistor to make run quieter.

No more failures occurred after I've kludged that fan in. Unfortunately the stupid fan causes interference inside the ultrasonic delayline messing composite signals up, but that's not a problem for me as I use the RGB input all the time.

Also R610 can be changed to alter the +B voltage, I recall that I've lowered that from 119V down to 117V.
These failures often happened after a runtime of 5-10 minutes.

This is the 2nd time that I did this mod.
The Trinitron tube has no true limitation on the vertical resolution due the aperture grille. So I thought it would be silly to waste so much bandwidth on leaving 25% of the screen black to letterbox 16:9 content.

These chassis from the early 90s have all their geometry set with variable resistors, often with enough range to squeeze the entire picture down to a 16:9 aspect. So changing this with a switch or relays should be more than trivial.

With this using a 90° tube means that only RV552 100k "V. Size" needs to be altered, which is wired as a rheostat to ground and the picture gets bigger with smaller resistance.

My implementation uses a PIC12F629 to actuate the relay, running code I wrote back in around 2012 and never updated it since then as it just works. This little microcontroller behaves as an flip-flop that can be triggered from a simple button or a specific Sony IR code.
That IR code can be easily changed by pressing the learn-mode button which lights up the learn-mode LED, both are installed next to the SCART connector and can be accessed through the vents on the backcase.
If the MCU receives a valid IR code then this will be written to the internal EEPROM and LED shuts off, all codes should be supported as 192 bits of space are allocated (I don't think that Sony used more than 40 bits).
The MCU also waits and does nothing for one second after changing the relay, I literally named that function "savetherelay" to avoid damage just in case my program somehow goes nuts and tries to toggle that output at several kHz.

Sony for some reason included a useless button on this chassis.
On the manual they state: "The TV button does not function on this set", so thank you Sony for the free button. I isolated that one from the circuit board and rewired it to the PIC.
The original remote control RM-658 has the same oddities of having useless buttons, so it made perfect sense to program one of these as the 16:9 mode button.

The TDA2579A generates all the deflection signals and synchronizes that to it's video input.

The big M50436 microcontroller controls the TV and generates the On-Screen-Display (OSD) but Sony cheaped out on a tiny detail and that's the dedicated 50/60 pin 17.
This is permanently tied to ground enforcing the OSD logic to draw on a 312,5 lines 50hz videomode, thus the indicators for volume, contrast, saturation and audio-mute are cutoff and invisible on a 262,5 lines 60hz videomode.

Now the TDA2579A has a special output signifying the current state of the video input, like if there's a valid video signal and if it's 50 or 60hz. This is done by sinking current on no signal, on 50hz there won't be any current at all so it will be pulled up to 12V and on 60hz it will be partially sinked to output around 7V.

Sony never put any effort into making full use of this pin 13 and only wired it up to detect if there's video signal at all.
If there no video then the MCU always draws the selected input on upper right corner of the screen.

I thought how much effort it would take to fix that.
Turns out that only two comperators, a couple of resistors and a single diode were enough to implement the missing support.


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