European version Philco predicta siesta

[Hugo barbedo]

Hi
good news and not so good news

the first powerup was somewhat sucessfull
the crt looks very strong, i have the brightness in the middle and contrast at 3/4.
the IF section seems to be working fine, although its strange that i have my modulator on channel 3 and can only tune it in on channel 5 on the tv...
sound is good even when there is lots of white content
the horizontal locks very well with the welding machine double diode
the vertical is not so great
i am having this foldover problem where the bottom part of the picture is missing and its appearing on the top of the raster. the raster is not centered on the screen and its not a problem of messing with the centering rings. i can fill up the screen by turning up the height control but the scanlines become huge and i loose vertical lock. also if i dont have a picture tuned in the raster fills up the screen
the video amp/sync separator tube is new and with the old one its the same
voltage checks on the vertical output/oscillator dont reveal any problem. all the voltages are preety much spot on
WP_20190331_00_08_20_Pro.jpg
on the yoke there is a black wire going to a metal wire that touches the screen aquadag...that is broken and makes the picture completely jumpy like when we loose vertical lock...bridging it with the black jumper wire seems to cure the problem but if i try to ground it to chassis the left side of the image collapses making a triangular shaped raster, very cool...i wonder if i have other broken connection or wire on the yoke causing the foldover...would it be possible? if so it would prevent me from chasing ghosts around the sync and vertical sections
there is an adjustable magnet on the left side of the yoke that has signs of abuse and the tube socket of the 6aw8a is also very abused, so it appears to me that someone ditched the tv because they could not fix this very problem...looks like i have a tough dog here, with me ususally its never the capacitors
WP_20190331_00_08_32_Pro.jpg
any ideas will be greatly appreciated


edit:
this is my scope on the pin 6 of the 6dr7
that is the plate of the vert oscillator
by looking at this i see the patient is suffering from serious heart disease...the drive is not linear, a wide pulse then a short one, then a wide one and so on, looks like it skips a beat every 2 cycles
the amplitude of the pulses looks ok , i am on 10x probe with 5v per division and the scope is not well calibrated so it seems decent to me. (maybe 120v PP)
what the hell can cause this???
WP_20190331_19_09_29_Pro.jpg

[Hugo barbedo]

ok so i am getting there slowly i think


c15.jpg
my tv has an additional panel on the right of the chassis with 2 additional linearity pots for the vertical that are not present on the american sets and consequently not listed on the schematics that i have
capacitor c15 is absent on my tv and on its place there is a capacitor connecting to that said panel
removing that capacitor and putting a 4n7 capacitor on the position of c15 makes the foldover go away and the pulses for the vertical drive are looking very good now
now i just have a totally squished top on the picture

i am at the point where i am thinking of removing the two linearity pots and recreate the "american"style circuit, that has to work but i consider it cheating.
WP_20190331_20_05_30_Pro.jpg
here each cycle is completed in 20miliseconds and that is equal to 50hz so we are good. the sawtooth looks preety also with a very short fall time (perfectly vertical slope)
WP_20190331_20_05_51_Pro.jpg

[Hugo barbedo]

I am almost done
just need to find were i put my test pattern dvd and play a little with the value of r27...on 17 inch sets philco seems to use a 100k, on 23 inch sets (11n56) they use a 68k, i will put a 82k
i am taking notes of all the changes i made until i find the proper italian schematic, if i do find it one day i can reverse all the mods and be able to use the extra 2 linearity pots.
i dont think it was me recapping the set that created this problem because i took pictures before the work and i have been comparing them and i did everything as it was...this tv had lots of repairs done and non original components. i think i am being lucky so far.

WP_20190331_21_04_24_Pro.jpg

[Electronic M]

Looks good!

[Crist Rigott]

Ditto!

[Hugo barbedo]

thanks!
installing the 82k resistor on place of r27 brought the linearity to a very watchable level with very minor distortion
i will keep it like this and use it until i find the exact schematic
i have it running right now as i write

i spent some hours watching it today letting it run for half hour runs and checking the temperature of the flyback etc and i ran into a weird problem that i fixed by accident:
when dead cold, the tv would turn on and high voltage would kick in very fast, the raster would come on along with the sound etc.. but the horizontal would take about one minute to lock...before that you could play with the hold control and bring in a very faint picture with lack of contrast indication of low AGC or a weak tube in the IF...but after a minute or so the perfect picture would just pop in with good lock and good contrast...i repeated the test several times with different modulators both on UHF and VHF etc and the result was always the same...it took too long to get a good strong picture and as a consequence the picture would not sync, after a minute it would just pop in...

i was about to remove the IF tubes to test them when i remembered i was using the old gassy horizontal output that came with the tv...i installed it but was not expecting any improvement of course....installing the new one cured the problem...how weird is that??? now i turn it on and it takes 10 seconds to lock by itself after the raster appears...

the only thing i want to tweak before putting on the back cover is the slight buzz when subtitles or text appears on screen...since i watch a lot of movies and they are all in English i like the subtitles turned on and that bothers me a little..i dont have any buzz on my other sets.. i dont have the equipment to do an alignment , so is there a coil around the audio detector that i can tweak sligtly to try and remove some of the buzz? i dont want to play with all of them...
detuning the fine tuning gets rid of the buzz but i loose definition of the picture..on my German sets i fix that by lowering the AGC just a bit but this set doesnt have an agc adjustment

cheers to all

[Robert Grant]

It can work because the line rate is almost exactly the same for NTSC and CCIR (15734 and 15625Hz). It's the vertical frequency that is quite different (59.94 and 50.00Hz).

I've read that the CCIR standards were purposefully chosen such that Europe's TV manufacturing industry could use USA-made flybacks off-the-shelf (flybacks have a resonant frequency - using an American or Continental European flyback in a UK 405-line set could burn the flyback).

I have a digital tuner box (ATSC 1.0) that offers 576i PAL CVBS video out. Every US set I've tried it on has no problem with horizontal sync. Some sets can be adjusted for vertical sync (usually with vertical distortions), while others won't sync at all.
50Hz flowing through the yoke when there is a transformer near it with a 60Hz field can cause the picture to shimmy as though the picture were formed on the surface of wobbling jelly!

[Hugo barbedo]

[QUOTE=Robert Grant;3209895]It can work because the line rate is almost exactly the same for NTSC and CCIR (15734 and 15625Hz). It's the vertical frequency that is quite different (59.94 and 50.00Hz).

i guess i could turn on the set without a picture and see what the "free running" speed of the vertical is, just for fun...i will do that if i have to remove the chassis again.

do you have any clue as to why i put the modulator on channel 3 and can only tune in on channel 5? also if i put the modulator on channel 4 i can tune in on channel 6 and so on. this set uses a turret tuner and its different from the wafer tuner used in the American sets

[Electronic M]

[QUOTE=Hugo barbedo;3209896]

Originally Posted by Robert Grant

It can work because the line rate is almost exactly the same for NTSC and CCIR (15734 and 15625Hz). It's the vertical frequency that is quite different (59.94 and 50.00Hz).

i guess i could turn on the set without a picture and see what the "free running" speed of the vertical is, just for fun...i will do that if i have to remove the chassis again.

do you have any clue as to why i put the modulator on channel 3 and can only tune in on channel 5? also if i put the modulator on channel 4 i can tune in on channel 6 and so on. this set uses a turret tuner and its different from the wafer tuner used in the American sets

IIRC different regions of the word that used CCIR/PAL (and for that matter different NTSC regions as well) used different channel frequenies from other regions. Some countries had FM in different places and planned TV arround it different, and places like the UK had competing TV standards like 405 squatting on some bands.
Your tuner probably comes from a different region from your source....That or your tuning knob is in properly indexed.