Sony Trinitron CRT (early 80s) remote control comm. issue

[CkRtech]

Hey guys -

Should probably mention right off the bat - I've got a meter and a scope but no isolation transformer.

I've got an early 80s Sony Trinitron with the programmed channels/display. You can only add channels via the remote by pressing the desired channel on the remote and then pressing the add button on the TV/remote.

The problem is that none of the remotes I have can do anything with the TV except power it on. They can't power it off, and they certainly can't change channels/volume or anything else.

The model is a KV-1223R. I managed to find a schematic for a KV-1222R - something that came out around the same time. Link (pdf too large for forum) - https://www.electronica-pt.com/esquema/tv/sony-esquemas-tv/sony-kv-1221r-kv-1222r-24229/

I haven't opened the TV just yet, but I wanted to get a logic check from you guys (in relation to schematic):

1: (Block N) - I want to say this thing is working as I can send IR to the TV and turn it on. That said...
2: The Sig leaves block N and pins into block MU <4>.
3: From <4>, there are a few directions to take from test point 57. One appears to go back to the right and down to <34> (REQ) and travel to M1. From there it hits a transistor and pin 12 "PON" (Power on?) of M1 IC2001. (Front panel display, power button, channels, volume)
4: The other two places <4> goes are MU IC001 pin 38 "Refresh" and pin 34 "RM"

I am suspecting either something wrong with the path to IC001 from <4> "RMT IN" (using the test point name for it) to either pin 34 or pin 38 on IC001 or something wrong with IC001 itself... provided it is getting power. I suppose it has to be since IC001 looks to be needed for processing of the front panel.

There is a test point TP71 labeled "RMT 5V" for pin 20 "TEST" of IC001. I do not have a datasheet for this chip: uPD650C. I assume... it goes high (+5v) when a remote signal has been received by the IC?

What would you guys recommend I hit? Just coming up with a game plan before I have the opportunity to sit down with it and open the set. Watch it just need a reflow somewhere.

[tooki]

Just to go down your list:

1: (Block N) - I want to say this thing is working as I can send IR to the TV and turn it on.
— yes

2:  That said…The Sig leaves block N and pins into block MU <4>.
— yes

3: From <4>, there are a few directions to take from test point 57. One appears to go back to the right and down to <34> (REQ) and travel to M1
— no

From there it hits a transistor and pin 12 "PON" (Power on?) of M1 IC2001. (Front panel display, power button, channels, volume)
— no

4: The other two places <4> goes are MU IC001 pin 38 "Refresh"
— no

and pin 34 "RM"
— yes

I am suspecting either something wrong with the path to IC001 from <4> "RMT IN" (using the test point name for it) to either pin 34 or pin 38 on IC001 or something wrong with IC001 itself…
— no

provided it is getting power. I suppose it has to be since IC001 looks to be needed for processing of the front panel.
— …and for receiving the "Power On" command from the remote.

There is a test point TP71 labeled "RMT 5V" for pin 20 "TEST" of IC001. I do not have a datasheet for this chip: uPD650C. I assume... it goes high (+5v) when a remote signal has been received by the IC?
— no. RMT 5V is the 5V standby. Pin 21 is the 5V power input to the IC, and pin 20 is bridged to it. This should have 5V any time the TV is plugged in and the master power switch (S901) is turned on.



So here's what we know:
1. I think you misread the schematic: there's no connection from TP57 to R147 or Req (connector pin 34). That's just where two unrelated connections cross, but do not join. There's no dot there. Ergo, the signal from the IR receiver is going straight to IC001 pin 34 (via R003) and nowhere else (save for R002 and C036 to ground).

2. Because the MCU (IC001) is required to turn on the set (it controls the main power relay with a signal from pin 18 (POW) via Q010), we already know that the remote control circuitry (N), the MCU, standby power (TP72 REM 12V and TP71 RMT 5V), and everything connecting them is working. Because the set turns on fully, we know the rest is working, too.

3. Ergo, in all likelihood, the MCU is receiving the commands. It's just ignoring them all, other than "power on". Is it the correct remote?

4. If it is the correct remote, then what you'd need to check is whether the IR receiver (N) is producing an output signal once the set is turned on, which you'd do by probing TP57 (RMT IN) and then seeing if you get the pulse train as shown in the schematic when pressing a button on the remote. 

5. The only thing I could think of, if the remote signal is present but ignored when the set is on, is if something's gone wrong somewhere else in the set, causing noise that interferes with the remote signal so much that the MCU can't decode it. Failed filter caps come to mind.

(Warning: This set is directly powered from mains: the standby 12V and 5V appear to be from a capacitive dropper only. This makes probing it dangerous and difficult if you don't know what you're doing. I don't know how to do that safely, though I suspect an isolation transformer is needed. I'll let others explain how to do it properly.)


Hope this helps!!!

[andy2000]

I'd start with the basics like looking it over for bad caps, bad soldering, and cracks in the PCB.  Carefully check the power supply voltages at the various test points with the set off and on.  I see that the M1 board gets it's power from the flyback.  Bad filtering on that supply could be corrupting one of the data lines.

After that, you won't be able to do much without an isolation transformer.  You'll need to look at the remote data lines with the set off and on. 

[tooki]

One more thought: Maybe the standby power rails are being disabled once main power goes on. But as far as I can tell, the remote receiver (N) is powered only by the 12V standby. So checking the standby rails while it’s turned on is something you could do with just a multimeter.

Maybe someone else who understands the circuit better can see the relationship between the standby rails and the “regular” power rails.

[CkRtech]

Thanks to both of you. I examined and typed that up at 2 a.m. my time, and my brain was asking for a bit more obvious of a hopscotch on the schematic lines. Now that I zoom in, I can just barely see it - but more importantly, I can see the now-obvious bold connection DOTS on the lines. <sigh> Sorry about that.

The lack of isolation transformer is a big wince for me. Kinda hoping just opening it and doing a visual inspection will provide some eureka moments.

As for proper remote - Also no... but I have tried several Sony remotes (their signals haven't really changed) as well as a programmable Harmony remote and custom PSP IR Blast software that lets you drop in HEX values to customize IR signals. As for the original remote, well... I made a video about it.
https://youtu.be/IM4bSuuju2Q

The battery corrosion was so bad, it destroyed the entire remote. I wonder if whoever had this before me kept that remote on top of the TV while in storage and some of it leaked into the TV. Now I am even more anxious to finally get inside the TV.

Bad filtering on that supply could be corrupting one of the data lines.

So checking the standby rails while it’s turned on is something you could do with just a multimeter.

I have a cheap multimeter that would be a better demolition candidate when probing inside this thing, but it doesn't have the safety of my other (Fluke 87 V) - Although I would prefer not to blow anything.

The ultimate goal is to just get Channel 3 (and maybe 4) on the set - but I know of no "reset button combination" to get default channels up (clear volatile memory) if that is even a thing.

[tooki]

Thanks to both of you. I examined and typed that up at 2 a.m. my time, and my brain was asking for a bit more obvious of a hopscotch on the schematic lines. Now that I zoom in, I can just barely see it - but more importantly, I can see the now-obvious bold connection DOTS on the lines. <sigh> Sorry about that.

No need to apologize, just didn’t want you chasing down connections that don’t exist!

The lack of isolation transformer is a big wince for me. Kinda hoping just opening it and doing a visual inspection will provide some eureka moments.

It might. For sure, you can spot bad caps or burnt components. (In looking for a full service manual, I found a Sony bulletin from 2010 saying to simply not use Trinitrons from before 1990, because an unspecified component could become a fire hazard with age! I assume it’s a cap...)

As for proper remote - Also no... but I have tried several Sony remotes (their signals haven't really changed) as well as a programmable Harmony remote and custom PSP IR Blast software that lets you drop in HEX values to customize IR signals. As for the original remote, well... I made a video about it.
https://youtu.be/IM4bSuuju2Q

The battery corrosion was so bad, it destroyed the entire remote. I wonder if whoever had this before me kept that remote on top of the TV while in storage and some of it leaked into the TV. Now I am even more anxious to finally get inside the TV.

Fucking Duracell... I swear, I think 95% of the leaked alkalines I’ve seen have been Duracells. I refuse to buy them any more.

Bad filtering on that supply could be corrupting one of the data lines.

So checking the standby rails while it’s turned on is something you could do with just a multimeter.

I have a cheap multimeter that would be a better demolition candidate when probing inside this thing, but it doesn't have the safety of my other (Fluke 87 V) - Although I would prefer not to blow anything.

Your Fluke 87V can take anything this TV can throw at it, other than the high-voltage circuitry, which isn’t the issue here. It’s the ideal tool for measuring the handful of voltages you need to measure.

The ultimate goal is to just get Channel 3 (and maybe 4) on the set - but I know of no "reset button combination" to get default channels up (clear volatile memory) if that is even a thing.

I don’t think you need the remote to do that!! According to the schematic, there are channel up/down buttons as well as programming buttons on the TV itself (blocks H and M3). Isn’t that a hatch on the top of the unit? (From the pix I’ve been able to find of the KV-1222R and KV-1223R, it looks like there is.)

[james_s]

Wow, that remote is really bad!

Give it a soak in some white vinegar though, followed by a good scrub with warm soapy water. You might be surprised at just how much improvement that gives. I've recovered some really bad battery leakage that way.

As for Duracell, I've seen quite a few of them leak too. I've had virtually all brands of alkaline batteries leak at one point or another but in recent years they are MUCH worse than they used to be. Duracell used to be one of the best and now I won't buy them anymore either. I've thrown away leaky batteries that were still sealed in the package. Now with few exceptions I only buy NiMH rechargeable batteries.

[CkRtech]

The lack of isolation transformer is a big wince for me. Kinda hoping just opening it and doing a visual inspection will provide some eureka moments.

It might. For sure, you can spot bad caps or burnt components. (In looking for a full service manual, I found a Sony bulletin from 2010 saying to simply not use Trinitrons from before 1990, because an unspecified component could become a fire hazard with age! I assume it’s a cap...)

lol. Lovely! I mean I suppose I could up and do a full recap, but man - Talk about a time sink!

Your Fluke 87V can take anything this TV can throw at it, other than the high-voltage circuitry, which isn’t the issue here. It’s the ideal tool for measuring the handful of voltages you need to measure.

I'll stay huddled near those low voltage ICs and test points. Ha.

I don’t think you need the remote to do that!! According to the schematic, there are channel up/down buttons as well as programming buttons on the TV itself (blocks H and M3). Isn’t that a hatch on the top of the unit? (From the pix I’ve been able to find of the KV-1222R and KV-1223R, it looks like there is.)

Yes. There is a hatch. The only controls available are Picture, Channel Up/Down, and Add/Erase. The channel buttons only cycle the channels stored in memory. So my set cycles 2, 8, 11, etc... In order to add a channel, I have to use the remote to key the channel number and then can use the "add" button to add it to memory.

[james_s]

Sony made some fantastic CRTs, but they sure made some irritating design decisions for the user interface. I have a lovely 90s XBR Trinitron downstairs that I *finally* found an original remote for a few years ago. For some dumb reason there's a "Menu Off" key on the remote that is not on most universal remotes and IIRC the stupid onscreen menu never times out and goes away without that key. One of my pet peeves is when equipment has features that *cannot* be accessed without the remote. It seems like such basic common sense that the remote should be an optional way to control the device, not the only way.

[coromonadalix]

Sony 8mm cameras had an remote specially used for programming all the options, rgb, sync. signals, etc etc ... and we could tweak an normal user one into an "technician one" with a few jumpers in it.

We had around 12 pages of pure programming fun, noting all the values before changing any of them.

[CkRtech]

Results -

TP72 ("REM 12"): 8.10V (off), 6.14V (on), 6.20V (while using remote)
TP71 (5V): 4.729V (off), 5.123V (on)
TP74 (12V rail): 0.002V (Off), 12.24V (on)

I couldn't find TP57 for some reason. I hooked on to R003 (33k) closer to the MU-2 connection side (although there wasn't much change in the reading at all depending on the side I hooked into.) This one is a bit strange as it looks like it sits at 2.064V and then drops to 1.5V when I hold down a button the remote.

Ideally...I hook my scope up to that point to see the pulses - but 2.064V when doing nothing and then holding around 1.5V while holding down the button. Shouldn't I see a greater range even with the multimeter?


The TP72 results are....weird.

EDIT: I unplugged MU-2 to remove the load of the IR board and measured TP72 (this time was technically at the right side of 7w resistor R065). This raised the off voltage into the 10v range and raised it to 8v when turned on (vs 8.1 and 6.14 with the IR board load). The datasheet for the remote amplifier (https://pdf1.alldatasheet.com/datasheet-pdf/view/128744/NEC/UPC1373H.html) says that it can run at a minimum of 6v. So I imagine the 6.14v is OK for the power? It just seems weird that the schematic straight up says "12V." Also note that the 6.14V at TP72 does go through one more series resistor (R001 - 100) prior to heading out to the IR amp board.

[andy2000]

Results -

TP72 ("REM 12"): 8.10V (off), 6.14V (on), 6.20V (while using remote)

That looks very suspicious.  The schematic shows 11.4v on pin 8 of IC1 on the N board, so your readings are a lot lower.  Either something is wrong with the 12v supply, or something is loading it down.

[CkRtech]

I've attached a photo with a few readings and some notes.

Could someone explain how we are electrically trying to achieve 12V? (Full wave rect = S3WB?)

It is also possible C023 is leaking. I can't actually get to it without some pretty good teardown. It wiggles a bit too much for my liking, and I *think* I see a "black orb" on one of the legs between the cap body and the board. What is the function of C023, and what effect (keystone?? Half power??) would a bad one have on the circuit?

EDIT: Removed AC measurements from attached image because I forgot to move the "ground" probe after measuring DC. 

[stj]

do you have a frequency counter btw?
if the cpu clock has drifted too far then it wont sync with the remote.
same issue if the resonator in the remote is messed up.

[andy2000]

I would start by looking at C023, R065, C025, and D010.  This type of power supply is very susceptible to damage from power line spikes.  If D010 took a hit, it could be leaky.

If you don't find anything there, you could connect a 12v power supply to TP72 to see how much current it's drawing.  Obviously, do this with the TV unplugged!  If it's drawing excessive current, see if anything is getting hot. 

[tooki]

do you have a frequency counter btw?
if the cpu clock has drifted too far then it wont sync with the remote.
same issue if the resonator in the remote is messed up.

But it’s able to respond to a “power on” by remote, so we can already rule out a ton of things, including those.

[stj]

some tv's will come out of standby with any button though.

[james_s]

I don't think a Sony will. Actually I don't recall ever seeing any CRT TV that would turn on from any button other than the power button.

[CkRtech]

I don't think a Sony will. Actually I don't recall ever seeing any CRT TV that would turn on from any button other than the power button.

I had a Philips Magnavox that would set off a "remote finder" if you pressed the power button on the front of the TV. If you pressed one of the other TV buttons (Channel Up/Down, Volume, Menu, etc..) it would just turn on the set without the remote finder. This would have been circa 1998.

Meanwhile! C023 has been removed and well... I definitely feel like I should replace this little guy. (attached)

edit: Hmm. This cap doesn't seem to have a series marking form nippon chemi-con.

[stj]

I don't think a Sony will. Actually I don't recall ever seeing any CRT TV that would turn on from any button other than the power button.

i had several philips models you could wake up with the numeric keys.
one of them couldnt decode teletext - that's when i learned to check the clock frequencys!

[CkRtech]

I would start by looking at C023, R065, C025, and D010.  This type of power supply is very susceptible to damage from power line spikes.  If D010 took a hit, it could be leaky.

C023 is an obvious replacement (which is great news, hopefully)
R065 had expected resistance
I pulled C025 because I have to order a cap for C023 anyway

C025 = Nippon-chemi SM, so I will go SMG
C023 = Nippon-chemi... something. I don't see a series. 250V 10uf. Any recommendations for a replacement for this guy?


As for Zener D010 - If the 0.715v (and 480 kohm) one way and OL the other (for both) is OK (I pulled it out of circuit), I can put this guy back. But perhaps a battery + resistor is needed to do a proper test? I do not have a bench power supply. And if this guy needs 12+ V for a proper test, I will probably need quite the frankenstein battery setup.

D010 markings are N3 and 12. I could also just order a couple of replacements if the values can be properly assumed. Suggestions?

Thanks!

[Ian.M]

Sony TVs of that vintage with control buttons on top under an access hatch were prone to the tactile switches used for the buttons failing shorted.   Check each button carefully to be certain it isn't shorted + has normal click action as IIRC multiple shorted buttons could make the CPU unresponsive to any commands.

Even back 20 years ago one typically had to replace all the top button switches if the TV came in for anything else to prevent the repair 'bouncing'.   Unfortunately the switches were something fairly proprietary, not normal tactile switches with four pins on 0.3" x 0.2" grid.

[helius]

(In looking for a full service manual, I found a Sony bulletin from 2010 saying to simply not use Trinitrons from before 1990, because an unspecified component could become a fire hazard with age! I assume it’s a cap...)

This warning is for "Overseas Models" whatever that means. Maybe it is a problem that they designed circuits for 220V but most of the world now uses 240V.

C023 = Nippon-chemi... something. I don't see a series. 250V 10uf. Any recommendations for a replacement for this guy?

It is across the standby supply, so I don't think ESR, life, or loss is that critical. You can use any "standard miniature electrolytic" like KMG, SMG, but it does help to use the same lead spacing. Looks like maybe 5mm LS?

What is the function of C023, and what effect (keystone?? Half power??) would a bad one have on the circuit?

Its function is to stabilize the standby power voltage. If it is bad, the standby power will oscillate.
See a simulation. You can change the value of C023 to "1n" and observe how it changes.

As for Zener D010 - If the 0.715v (and 480 kohm) one way and OL the other (for both) is OK (I pulled it out of circuit), I can put this guy back. But perhaps a battery + resistor is needed to do a proper test? I do not have a bench power supply. And if this guy needs 12+ V for a proper test, I will probably need quite the frankenstein battery setup.

You can only test the Zener breakdown at the specified voltage. Remember not to put 12V directly across the Zener without limiting the current.

[tooki]

(In looking for a full service manual, I found a Sony bulletin from 2010 saying to simply not use Trinitrons from before 1990, because an unspecified component could become a fire hazard with age! I assume it’s a cap...)

This warning is for "Overseas Models" whatever that means. Maybe it is a problem that they designed circuits for 220V but most of the world now uses 240V.

1. No, the world mostly standardized on 230V, which is well within the voltage tolerances for both 220V and 240V devices, the voltages that had been in use prior. No more countries use 240V than in the past, if anything it’s fewer. (Meanwhile 110 became 115 and then ultimately 120V.)

2. What’s overseas from Japan? Go due east and THAT is the voltage in question. (Remember, since voltage and video standard tend to go hand in hand, and Sony’s model numbers are different for NTSC and PAL CRT TVs, not to mention differences in tuners and regulatory compliance,  model numbers necessarily tend to be market-specific. So you won’t find overlap between 120V and 230V model numbers.)

[CkRtech]

What is the function of C023, and what effect (keystone?? Half power??) would a bad one have on the circuit?

Its function is to stabilize the standby power voltage. If it is bad, the standby power will oscillate.
See a simulation. You can change the value of C023 to "1n" and observe how it changes.

Hmm. I saw a change with C023 set to 1nf, but it was rather small. It didn't seem to change the 12vdc at C025 at all.

Is it likely that this capacitor being bad would cause the voltage to drop to nearly half what is expected at TP72 (6.14v when powered up), or is it just a small part of a larger problem?