Indesit T12"SGB off-station shadow

[newlite4]

I have owned a number of these mid '70s monochrome sets over the years and have not known them to be particularly reliable. I have recently corrected a fault on one where there was a black shadow covering the top left of the screen when the set was displaying an unmodulated raster, the shadow was absent once the set was tuned to a station.
I replaced the chassis and the fault remained, I then replaced the yoke assembly and the fault was cleared.
I am unsure as to what caused the fault, I can only assume some kind of short/resonance within the yoke in the absence of sync pulses was the cause, any theories?
Neil

[beery]

Hi Neil,
this was probably due to the scan coils having slipped back along the tube neck. It could also be due to some unwanted magnetism such as a magnetised scan coil clamp. The symptom is due to the electrons being deflected beyond the edge of the tube neck (often hitting the anode directly), so they miss the screen.

Cheers
Andy

[gec2110]

i remember these sets they were not very reliable and always had line sync
and tuner problems there were two versions
one with the awful dial channel selector which had a clickety click operation
and then it was changed to four push button tuner
these sets looked good they came in orange and white
were very brittle cabinet and chassis wise the back cover was always a
pain to put back on after servicing

[Steve_P]

These things - either love or hate. If the fault recurs, take a pic or two and put them up.

Cheers,

Steve P.

[newlite4]

Thanks for your replies everyone. I think that perhaps it must have been some sort of stray magnetic field effect. Anyway, it is running fine with its replacement yoke. Just have to bag it up now and put it back in the loft .
Neil

[Jimmyhaflinger]

We still have loads of them around here in Italy (they were actually made here) and yes, they were cheap and nasty, but many of them managed to keep going for decades anyway.

early ones made from 1973 to 1975 had the rotary dial selector, the 4 pushbutton tuner was made in 1975-77 and was then replaced by an 8 pushbutton tuner, these sets were made until about 1981.

a far cry from the quality of Indesit's late 60s hybrid wood-cased portables...

[Nickthedentist]

Originally Posted by Jimmyhaflinger

a far cry from the quality of Indesit's late 60s hybrid wood-cased portables...

...but very similar to the flimsy full-sized Indesit hybrid models that were around in the 70s here

[Jimmyhaflinger]

Most 70s plastic cased portables were flimsy junk... but the first prize would have to go to that mid 70s Crezar thing... they managed to make an almost working TV out of a couple of primitive ICs and a few transistors... actually, it's simpler than many am-fm radios... complete with a desperately poor tuner, 0,1 watts of audio power and floating black level due to no DC restoration

[Heatercathodeshort]

Yes agree Steve! A love hate relationship. I don't remember them being all that bad and were sold in huge quantities as was its big brother 24" version model E24GB.
One word of warning when servicing one of these with the chasis removed. It is very easy to allow the front half of the cabinet complete with tube to unbalance when the chassis is removed resulting in the tube base connector being yanked violently. Ssssssss
Yes it happened to me...That tube evacuating pip is very easily broken..J.

[Zelandeth]

I seem also recall hearing stories of the tube neck being broken when the back of the cabinet was screwed back into place - you need to be very careful to ensure that it slots back into the correct place first, otherwise you'll be looking for a new CRT.

[Welsh Anorak]

Hi
That's me holding up my hand! Yes, one of my first repairs in the seventies - got the orange box going, back on, tightening the screws then click-ssssssss!! And it belonged to a customer - almost twenty pounds for a new CRT was a lot to a schoolboy then.....

Glyn

[newlite4]

Funnily enough, I had to do just that with the duff tube yesterday prior to disposal. It was quite a stubborn pip to break requiring several goes with the pliers
Neil

[Brian R Pateman]

Of the past 12 posts, 7 have been dealing with how nasty these Indesit sets were and not with the original subject!

Let's drag this back to the point please!

Regards,

[Zelandeth]

I get the impression that these are one of those sets which come in two flavours, those which are absolutely unwaveringly reliable, and those that aren't! I've still got mine, which has never had the back off despte having a busy life. The only thing that's really marring its condition now is that its tube is quite low - and it's missing half the slats in the back.

Regarding your off-station shadow, I think mine may actually do a similar thing, I definitely remember its off-station behaviour as being a bit odd - though it behaves just fine once it's tuned in, so I'd never really thought about it. I wonder if this might be a common fault?

[newlite4]

Sorry for the wait everyone, here is the off-screen image showing the shadow before yoke replacement, (ignore curving/non-linearity,this is just camera shake).
Neil

[Hybrid tellies]

Thats a definate scanning coil problem. If it was the yoke sliding back along the tube neck you would see shadowing on each of the corners. I remember seeing a few of these for repair back in the late 70's. They were far from the worst that we saw, they gave good pictures and were noticably lighter in weight than all other batt mains portable tv's from that era due to the use of a Pump start power supply or in other words an early version of the switch mode power supply. This meant that they could dispense with the bulky mains transformer.
I thought this was a rather clever little design by Indesit which proved to be reliable as well.