1971 Sony Trinitron KV 1201
 

I picked this up tonight, it worked when initially plugged in. After the ride home, I suddenly have no picture, not even static. The sound is still fine, though the crt isn't lit up. When I shut it off I get a momentary red, green and blue bar flash horizontally across the screen, then a green dot in the center for a minute.

What should I look for when I open this up tomorrow?

https://i.ibb.co/b1SQ6hB/20201220-212720.jpg

So... I can't open the case. The screws and knobs came off, yet the plug is stuck. I've laid the tv on its face and dropped a bit of gun oil into the plugs socket, hopefully it will help.

https://i.ibb.co/86PKF8t/20201221-201903.jpg

The plug will stay attached to the back, it is a safety interlock. Just pull the whole back off.

Thanks :)

The case was just stuck with grime.

I'll clean up the chassis and start an inspection tomorrow. Though I still need to find a schematic for this.

https://i.ibb.co/wpNtwJV/20201221-212622.jpg

https://i.ibb.co/g6Vj48p/20201221-212423.jpg

https://i.ibb.co/RpYYTjF/20201221-212310.jpg

https://i.ibb.co/zmjK4nS/20201221-224033.jpg

For a manual go by the chassis number ( SCC-### ). In the
early Sony days the same model number can have a totally different
chassis in it. Sears & Magnavox did it too.

73 Zeno:smoke:
LFOD !

What's going on here?

http://www.videokarma.org/attachment...1&d=1608651909

.

The first thing these Sony sets needed is a cleaning of all pots and any switches.

The original operation should return but until that's done, nothing will seem right.

Capacitors are usually OK or totally shot, look for bulges and excreta. Good luck.

Thats the main filter can on the small PS board. Looks like candle
wax to me. Not an uncommon thing to find.

73 Zeno:smoke:
LFOD !

Funny thing about '70s electros is that they often go inert with no telltale signs like venting or spooze out of the bottom.

We had a Sony come in from another shop with all sorts of vertical issues. Working through it, I found almost every capacitor bad. The shop owner said it wasn't possible a bad electrolytic was the problem because he jumped every cap in the vertical one by one (insert loud gasp that he didn't blow this Sony up by hot jumping the caps...).

Every cap that was changed either improved or changed the vertical scan until the last one or two fixed it.

None of those caps had any outward signs of problems.

John

Well I can't find anything denoting a chassis number, inside or out.

The wax that is on top of the electrolytic can seems to have dripped off of the circuit board that is above it. I've given a visual inspection of the other caps, no leaking or swollen ones to be found.

Rather than testing each cap I'll just take notes of their values and do a total recapping, I could use the soldering experience.

I've never owned a Trinitron, let alone a vintage one. I saw this set working before I brought it home, the picture was a bit blurry. Though when I got home.. the screen didn't come on, not even static, just sound.
https://i.ibb.co/cy1MfnP/20201222-183408.jpg

https://i.ibb.co/hgpDt7Q/20201222-183309.jpg

Look for a blown pigtail fuse. Check electrolytic caps I power supply for short or high ESR.

Looks like the chassis tag is on the metal above the HV
area.
Before you spend money on caps get the pix back ! Be sure the
CRT sockets on all the way 1st.
If you do a recap only do the electrolytics. Do them a few at a time
then recheck the set as you go.

73 Zeno:smoke:
LFOD !

Bingo.

John

Found the chassis number, 330ab22.

The fuse tests fine.

Made certain that the crt socket was firmly in place.

No change.

Okay, I'll order the electrolytics this weekend and go from there. I COULD just desolder the caps in the power supply and test those but.. I might as well replace those 49 year old caps, I just don't trust them.

That sounds like the picture tube number. Sony chassis numbers start with SCC.

EDIT: I found some notes at work. I'm 99.9% sure it's a SCC17. There are a few suffixes, but they're mostly identical chassis. The notes I have on that chassis (other than routine problems like blown horiz outputs, regulators, vertical problems, etc. which I never mark down) are:


Dead - bad C513 (4.7uf/250v).
Dead - R566, Q504
No picture but *has* High Voltage - Q402 Open (2SC1364)
Weak or no horiz lock - bad C504 (1uf/50v)

All those were marked as multiple failures (I saw those specific problems 2 or more times)


John

Well I can't find a chassis code on this. I've looked at it a half dozen times, even had a friend go over it too, there is nothing. Every label has been read, nothing is stamped on the metal. Perhaps it HAD a label and its missing.

KV1201
Different Sams manuals are
#1309-2
#1389-3
#1493-3
#1698- SED

Those tags do get lost. Good chance it fell down between the CRT
& the shield. The 330 number you found is the CRT number.
If the serial number is still on the back post that & I can try
that. In any case all are SCC-17 but with different letters at the
end. They may be all very close BUT sometimes they are totally
different.

those are nice sets, I have one as a daily watcher. sounds like the CRT is being biased off, turning the set off releases the bias as the residual HV pulls the electrons thru.

check HV anode voltage 19kv

check the voltages at the 3 cathodes of the CRT IIRC should be around 100v-110v. These are driving by the collectors of the 3 video out transistors.

The grids all get voltages from boost voltage, so if you lost that, then you will have cut off the tube. boost is about 500v check pin 5 (common screen grid) on the crt should be upper 400's the common control grid also from the boost is upper 90's (pin 7)

My guess is you lost the boost.

Thanks for the help. I'll pick up a HV probe and look into acquiring a manual.

This is a cute set, I'd love to add it to my living room for occasional watching.

I have the same set with " wood" cabinet , KV1212 ( the one in my avatar pic ). It works like a champ but has pincushion issues ( any ideas? -- thanks !) This set was the one in the Sony print advertisement where it was set up in a bank branch and left running for a year and a half with no servicing needed :)

Mine had a problem with the pin cushion corrector circuit. IIRC, it was on a small board near the flyback.
The set was about six years old at the time. That's all that went wrong in the time I had it. I sold it cheap when the CRT was starting to look tired.
Too many years ago. :sigh:

I meant to state that it was a small electrolytic on the board.

Thanks dieseljeep , I kinda knew there was no actual adjustment for pincusion but couldn't for the life of me remember how it was done on this set ! i picked up this set from a second hand store for a song and was a daily use set for about ten years, it had this issue for all that time but never seemed to get any worse. Iv'e had it for about 22 years now and run it every now and then, still works the same!