Help with piccolo j-310 pincushion
 

Hello, i bought this nice little 6 inch portable color television from japan (it was unconfirmed operation). Tv came wrapped in news paper and tape but it was in one piece :) i then went on and tryed it out and it worked normally except it had little bit of pincushion problems..

Tv model is piccolo j-310 and its made in taiwan, board says emperor PWB CTV 004D. I cant find schematics or any data on it.

I changed all electrolytic caps as google suggests + all film caps near flyback transformer but it didnt help.

Board has only pots for vertical position and size and b+ adjustment and AGC adjustment + some color pots at neckboard and un named adjustable coils i believe. I tryed the redneck method of messing with the screw driver but didnt help.

I got some scope pictures of signals but im not smart and experienced enough to do accurate diagnosis.

While doing measuring one of the caps blew up. I replaced it with old one and picture got narrower. I learned that it was bi polar cap that is one side to horizontal deflection coil and other leg goes to inductor who then passes the signal to ground. I looked in to it with scope and indeed voltage is spikeing just over 25v witch is capacitor rating. The old bipolar cap is very big in size compared to new one (same values 3,3uf and 25v) old cap dosent get very hot. I tryed shorting inductor to ground and picture got almost good, just little too wide and and still very little pincushioning. This made me to believe that it must be horizontal deflection yoke coil partially shorted becouse it isnt producing enough magnetism to image but still passes too much voltage to ground side(this is my theory but im basically guessing here)

I made some bipolar caps of regular caps to try different values but 3,3 - 5uf range seems optimal for picture widht but these caps go hot.
Old 3,3uf cap gives different widht then the one that blew up or 5uf that i made of 2 10uf caps

I then started to looking at horizontal output transistor (HOT) vaweforms and I also took amperage measurement from horizontal deflection circuit to see if its shorted or something i try puting up some photos.

Is here any experienced tech who can lead me to right way?


Horizontal output transistor voltage:blue and yellow is current of same circuit

https://i.ibb.co/gyS2TBV/IMG-20230925-151603.jpg




Blue: voltage coming out of HOT
Yellow: voltage that is driving HOT

https://i.ibb.co/xfVcJvw/IMG-20230925-132103.jpg




Voltage coming out of horizontal yoke coil. Is this normal looking? Seems odd to me and i cant find any reference vaweforms for this side of yoke.

https://i.ibb.co/xJ0hnFf/IMG-20230922-125454.jpg




Symptom

https://i.ibb.co/r6zG5Nd/IMG-20230922-130756.jpg

Bipolar caps comes with categories/types; rarer ones are for high ripple content. These are special ones, sometimes also found in tweeters in intermediate quality coaxial speakers.
If space allows you can use a film cap; heat problem solved.
But about the function of this cap... this serves for the H. linearity at one side; this don't affects pincushion, at least directly.
You mentioned about this cap being connected directly to ground, so I suppose this model not having any pincushion correction (special inductors or dedicated circuit. Some TV's really don't have any; they rely only on the CRT quality/design. And this can varies...
I've seen some pincushioning present on some 5" color CRT, but I cannot assume all need being the same.

Thank you for your valuable info, i was thinking if i could replace it with film cap and i even asked local tv repair shop guy but he didnt know if it would work.

The horisontal yoke coil ground side is connected to bipolar capacitor and goes through it (connected in series) and it then travels through inductor to ground (also in series). Sorry for my poor explanation im still learning electronics and english :)

I tryed connecting it directly to ground (bypassing the inductor) and it streightened image a bit but image was little bit too wide this way. you said it was "special" kind of inductor, i was thinking if i could get some general choke coils to try out if i could get it better?? Do you know if they could work?

About the cap, you can use "generic" polyester cap with proper capacitance; basically any will handle the required current (exception is the very small ones for signal).
The generic bipolar cap can be upsetting the horizontal linearity due to ESR. If this is the case, the poly cap will restore correct operation.
The series inductor probably is a premagnetized inductor for correcting the linearity at opposite side that the cap corrects. So, is a special kind of inductor, also. By the way, a pincushion one will resemble a mini transformator, with at least 4 terminals.

Then, is interesting to play with proper cap first, to see the result, with the linearity inductor in place.

I will order the right cap and report back. There is 4 legged mini transformer that is connected to drive the horizontal output transistor, is it the one responsible of pincushion?

No, this is the horizontal output driver transformer, to better couple the pulses (it have a choosen turns ratio for adequately driving the base of H.out. transistor).

Hello, i have not ordered the cap yet but i did try to "reverse engineer" the circuit and heres the result:

https://i.ibb.co/vVTNCtt/IMG-20230929-WA0000.jpg

I also looked in to jungle ic datasheet but i cant understand what to check out and if there is anything that i can adjust to make the picture more barrel shape.

I think where it said on datasheet 110v +b there is not voltages that high on that pin. And other parts of suggested circuits do not match 100% with actual circuits (i have done some schematics of those too but they are not ready yet).
Also when i was fooling around with settings i think it once got really good picture shape when i turned down g2 alot and picture was kind of dim, but when i switched to other game the geometry got really wobly...

This cap had a pretty high failure rate in older sets. I think it was ready to go
& blew on power up. The replacements wont work, they are the wrong type.
We used the OEM replacements as NP caps were hard to find.
Keep in mind the hoz out spikes can be quite high & lots of current.
Example is on a 25" TV the hoz out B+ is @120 volts but the spikes are
@ 1 KV
So I think the right type of cap will fix it maybe the PIN problem also.

73 Zeno:smoke:
LFOD !

Consumer level TVs of this size never had any sort of geometry circuitry on board. Any distortion would be a function of the yoke design.

I have a feeling your original capacitor is fine as is and the pincushion error you're seeing is normal (remember that flat displays have spoiled us with their perfect geometry, perfect purity, perfect convergence, etc.).

Since the cap is old anyway, replace it with a good plastic one. Old scrapped plasma sustain boards are a good source of quality plastic caps in those value ranges.

John

EDIT: I have some caps in that size from a plasma. The brown one is 250V and the larger blue one is 315V. If you'd like one, I can stuff it in an envelope for you.

https://i.imgur.com/7t14PnU.jpg

I will try to ask on monday if anyone local has the right cap. i tryed looking at my scrap philips chassis but it had no right value caps. It sucks paying 7€ shipping for 0,3€ part :(
That is really nice of you john but i wonder how long it would take to reach finland?
I also think that the cap will probably not fix the pin cushion tho.
How can i attach images to post like you did?... Never mind I figured it out!

This forum is very helpful and friendly place :thmbsp:

I don't know how long it would take to get there, but I bought an oddball vacuum tube off ebay years ago from somewhere near you and it took about three weeks if I recall correctly.

I got my collection of high value/high voltage plastic capacitors from the sustain boards of plasma TVs I scrapped out - very handy in rebuilding bypass filters in old tube radios and such - once done they will last forever. If you can ask a local repair shop if they have any scrap sustain boards they're willing to give you, that's a good place to start.

In any case, if you'd like either or several of those caps I have I'd be happy to put them in a padded envelope and mail them to you.

I also don't have a lot of faith that a new cap will correct your pincussion error. Can you post a picture of it running?

John

Here it is running, i think it looks worse in person. S/N looks good to me but E/W is bowed inward.

https://i.ibb.co/hWt2Rhb/IMG-20230930-093340.jpg

https://i.ibb.co/v4QP3nn/IMG-20230930-093229.jpg

It is bowed so much that i dont think it left factory this way..

I will ask monday if anyone has caps or scrap boards so i would not have to wait 3 weeks

Honestly, if I repaired that TV I wouldn't have given the bow a second glance. It looks within the expected geometry of a TV that has no active pincussion circuitry. Only a change in the deflection yoke design would change the geometry.

At the time that TV was made, all the images viewed on it would have been full screen and that hard border would have been overscanned out of view. Only a TV program that showed a (for instance) doorway on one side or the other would have been noticed (and how long would that door have been in the shot?) or if it was connected to a video game with fixed sides.

I do remember getting some complaints on geometry when Pong first started selling. On typical live video that most people would be using the TV for, most people simply didn't notice.

For capacitors approaching .5uf (500nf) that are not electrolytics, plasma sustain boards are a gold mine. I have several poly types that are over 5uf at 200V or so. Sustain boards need higher value capacitors that have the low ESR of plastic caps, so they don't use electrolytics for coupling.

If you run into a dead end, let me know.

John

You might be right.. As it is now there is not enough overscan to hide the bowing(black bar is visible next to "sandstorm") but when it had the new cap that blew up image was little bit wider (more over scan) maybe the cap has dropped out of spec and it was like that.

If this the case then my next queston will be is there a way to hack this circuit (tweak component values or add/remove components) or would it be possible to add magnets to the sides or some other way to get it even a little better? It really looks annoying when playing games becouse they have lots of straight lines everywhere and i keep staring the geometry and not focusing on the game :scratch2:

It's possible a little more width might cause a slight change/improvement in the pin distortion...

Replace the BP cap and reaccess.

The problem with adding magnets is that it will affect the purity and convergence, and make the TV more sensitive (purity wise) to compass rotation. If you want to try, use the soft "refrigerator" advertising magnets like you get from a car dealer (for instance). Cut it into small squares and try moving around the yoke to see if it helps your pin distortion, but be aware of purity and convergence changes at the same time

John

Hi to all,
Hi Pjaska,

I agree with JohnCT's comments, these 5" color TVs with in-line tubes have no barrel or pincushion adjustments.

I have a personal fondness for tiny Color sets & collect many.

Due to extreme forum file size limitations, i unfortunately cannot post any of the service manuals i archived (pdf) but if you send me a PM with a mail address, i can send you some & you can see for yourself the "fiddling" procedures to obtain a visually acceptable result; usually a mix of centering tabs, wedges under the yoke & more rarely, weak plastic/ferrite magnets.

I have several Goodmans, Roadstar SM's, note that these TVs are pretty generic varying mainly with which high pin-count "do it all" IC the manufacturer selected.

They were also sold under a bewildering number of brands, i've created a txt text file i update on a regular basis to keep track of who did what/when, etc. just for the fun of it.

Just a last minute thought, don't discount possible magnetization during shipping, presence of a metal mass near the TV, external speakers with a leaking magnetic field.
The automatic Power-on degaussing is often quite weak in these small sets. Some have a manual "Degauss" push button.

I have a 2 ft diameter AC powered degaussing loop, very useful for large vintage color sets.

Best Regards
jhalphen
Paris/France

Thank you hjalpen, i would definetly like to get my hands on to those manuals!
Do you mean that degaussing could help geometry issues? I didnt know that i thought it just had to do with colors going messed up.
This tv dosnt have a degaussing coil at all. Lucky me, i have degaussing coil in the works at garage, just need a lightbulb holder/socket for the series light bulb (and maybe a power switch would be good idea) so i can finish it.

I pm my email for you hjalpen, thank you for helpin! :thmbsp:

Hi to all,
Hi Pjaska,

I sent the following set of files (SM's, schematics, photos) to your Mail address.
see list in snapshot below.
All concern 5" micro color TVs, all are PAL B/G Euro models, some with SECAM.

Hope this helps,

Best Regards
jhalphen
Paris/France

Hello and thank you all my friends!
I got the capacitor for horizontal deflection. Image got little bit wider then with original capacitor and its not heating up like the electrolytic ones. Pincushion is still there but its much more tolerable now with proper overscan:

https://i.ibb.co/zxcpF8n/IMG-20231002-103848.jpg


https://i.ibb.co/LpDkvHg/IMG-20231002-104104.jpg


https://i.ibb.co/PQ3Q88B/IMG-20231002-144021.jpg


I tryed using gluable little magnets to it but i didnt get it any better. Maybe i try that in later episodes.. It is now having some interfierence lines on the picture after turning the tv on. They are usually black and may have some rainbow color parts too... They go away after some time or if i turn brightness and contrast down a little. They like appearing on bright light screens. I noticed this first time when i was messing with the capacitors, i dont know if they where there before me or not. I used to have it low on brightness becouse the black looks so gray, now after recapping and adjusting it i can have black look better in brighter settings. Do you guys think this is dangerous or bad for my tv? I havent build the degaussing tool yet..
Edit: interfierence looks like went gone when i reassembled the plastics. Maybe something was too close for wrong wire who knows time will tell...


https://i.ibb.co/xj5QvtF/IMG-20231002-151352.jpg


I have spend so much time with this little tv now that my wife says i can sleep on the couch with convergence and geometry if i dont come back to real life now :twak: so i think i will have a little break with the project for now





:worthless

https://i.ibb.co/7Cgf8h0/IMG-20231002-163557.jpg

https://i.ibb.co/nLd8vpG/IMG-20231002-163648.jpg

https://i.ibb.co/RgWvjqM/IMG-20231002-163703.jpg

Its cool how it is so close with the footprint of famicom. Now i can take it with me and my AV and USB modded famicom and we can all play outside (or next to a car at least) to the sunset

https://i.ibb.co/TqW20Sz/IMG-20231002-163854.jpg

Family Game? I believed they had only been sold in the third world. I had one.

Yes, i imported from japan. Here we had toaster NES but if you look closely you see that the "european versio" is scratch off with a pen becouse its really usa ntsc model that had no lid. Tv is also ntsc and imported from japan. I live in Finland (europe) our old game system have the "pal curse" the games are slowed down from ntsc 60hz to work with pal 50hz so they are like slow motion movie scene.

I can imagine that. Here in Uruguay since the late 80s, almost all televisions were three systems, PAL N, M and NTSC due to games and camcorders of American origin. Congratulations, you have put a lot of love into that little TV.

I think it displays much better on that mini TV than on my mini TVs. What CRT does it uses? Shadow masks are all of the same "pixel" size? Maybe ist a monitor CRT?

+1, I'm also pretty sure to have seen one of these color 5" with larger phosphour size (I can assum not all being equal).

https://i.ibb.co/vBtSBb8/IMG-20231004-192557.jpg

I think it was labeled as 6" somewhere.



Here is update on where we are today: i see that the old photos are not available, shame. The tv is now having new shiny plastic for the screen and i also had made a new sticker for it. Tv also at one point started again making noise and black horizontal lines would come back again when cranking up the brightness or contrast knob. I wiggled all the connections and some times this seemed to effect. Then i took my soldering iron and re soldered the ground wire for tube, didnt help, then i re soldered every big connection at the neck board and after that i could again go high with brightness and contrast and no problems!

https://imagizer.imageshack.com/v2/1...924/OBkmVT.jpg



https://imagizer.imageshack.com/v2/1...924/gYzwtG.jpg



<a target="_blankj" href="https://imageshack.com/i/pogYzwtGj"><img src="https://imagizer.imageshack.com/v2/150x100q70/924/gYzwtG.jpg" border="0"></a>



<a target="_blank" href="https://imageshack.com/i/poOBkmVTj"><img src="https://imagizer.imageshack.com/v2/150x100q70/924/OBkmVT.jpg" border="0"></a>

My little tv went viral: https://www.songbirdfx.com/how-to-po...oles-anywhere/

Hi to all,
Hi @pjaska,

Congratulations! on going viral with your "play anywhere" video games.

Small color CRT resolution:
in my opinion, the 140BYB22 (5") used in JVC's CX-500 color combo units has the best resolution. Why? because although being an in-line CRT, the phosphors are fine dots instead of the elongated vertical slit shape seen in many others such as the JVC CX-610 series.
Two screenshots below. Forum size limitations reduce the true sharpness of the images

https://i.postimg.cc/hG76NQYR/JVC-CX-500-ME-BG-30.jpg

Best Regards
jhalphen
Paris/France