CTV New Workshop. First Up ITT FT110

Superb news John, glad you're on the home stretch with the build. You've done a superb job building all that on your own, especially as you get so little time due to the day job. Even more impressive this being the very first time you've built anything on this scale, you must be very pleased. On top of all that now you've got a place to relax and enjoy your passion for TV repairs. A bonus for us too, we get to enjoy and follow "Tales from The Jaycee-bench", really looking forward to following your exploits and the journey of this rare ITT.

Aye, that old shed did look a bit jaded, didn't it? - I'll tell you what though, some of those boards/planks would done nicely to rebuild the tiny trailer that goes behind my ride-on lawnmower! Or made a good dog kennel, cat shelter, parcel drop-box. The list is endless.

That looks like a very professionally built workshop you have there now, and has given me ideas do freshen up my sad looking cabin.

Thanks for the comments, it'll be great to have somewhere where I don't have to tidy up after a repair session as I had to when using the bedroom or dining room table.

The build might look professional but I can assure you many mistakes were made along the way, close scrutiny would bring a few tut tuts from someone who does these for a living. The design changed many times along the way causing issues later, and why does timber come in metric and sheet material in ft and ins? Didn't know that when I started 😱

Posted by: @jayceebee

and why does timber come in metric and sheet material in ft and ins? Didn't know that when I started 😱

I blame the Americans! - I guess you're referring to 8' x 4' sheets of ply and Sterling boards? being imperial, and then the timbers for joists and studding etc being metric?

Your new workshop looks really nice! I bet it’s lovely in there 🙂

I built mine back in 2016, like you I had never built anything like it before, I definitely made several mistakes! Some which I need to rectify sometime this year, but it’s still standing, and it’s dry and warm too, so I must have done something right!

 Regards,

 Lloyd

Well, after several hours at a fairly low voltage C731 is drawing about 10mA and is warm to the touch, with my 1400 I got it down to uA in a very short while. I'll give it a bit longer and report back.

On the other FT110 the BY133 mains rectifier has previously been removed, I wonder if it was damaged by the C731 also?

I have encountered varied reforming times on the many sets I've done, some quick some hours. One example that always sticks out was a 400+200+100 NOS from Malc, it took over 8 hours. The G6 ones I did just recently 4 x 4 section multi-cans, took just about an hour in total.

@crustytv

And then, you find one that seems to reform OK, then a few hours later, goes short circuit, or at least, extremely leaky!

After 8 hours this can shows no signs of being able to hold any sort of a charge. Upping the voltage just made the can get warmer and with nothing connected other than a DMM any charge disappears in just seconds. A rummage around turned up a new 180uF at 400v which I've fitted as the reservoir, my Covid self isolation ends tomorrow so after work I'll head to the lockup. I've got some NOS plasma TV boards which should yield some suitable high quality capacitors for the smoother section rather than some of the very dubious types used with LCD.

In Dr Leonard McCoy's famous southern drawl......."It's dead Jim!" 😉

Just noted November 1974, is that true? forty-seven years of service not bad.

I hadn't spotted that, my birthday is in November. There's another story to this, in fact I've always wanted an FT110 and these two are the first I've ever seen in the flesh.

It goes back to my college days when I was on the C & G course 222, apprentices like myself but from another local company used to really rail against Thorn, it's chopper PSU used in the 3000 and it's complexity. They were very comfortable with their PYE/Ekco, GEC hybrids and thyristor based G8s, to them there was absolutely no need for such a complex thing to be in a domestic telly. Then their owner bought in the FT110, they didn't know what had hit them. I'm led to believe they were reasonably reliable but it took the some time for them to get to grips with them with many tales of woe.

And that's the reason why I snapped these up when they surfaced, I wanted to see what all the fuss was about. Actually I was surprised to find the basic concept was used in the later Thorn 9600 series, it's a SYCLOPS type. The chopper or converter stage is synced and driven by the line osc with a PWM stage, the line output transistor base being directly driven from a winding on the converter transformer.

I seem to remember we only sold a couple, I think but not sure now that they were expensive sets perhaps that’s was the reason. Most customers were happy with the other ITT sets that were available. 
I remember nothing of the circuitry, so they mustn’t have give much trouble. It will be good to see one work again, I liked the ITT range of sets.

The ITT FT110 was available to me when I was a dealer for the make but never bought any in for sale or rental some reason or other.  Heard no horror tales about the set. However, I did buy the Digivision models which were possibly the most technically advanced sets on sale in the mid 1980s. Did have the occasional chip failure. I think there still is a few Digivision ICs somewhere in the shop. Kinda remember the TPU2722 text processor needed replacement quite often.  Logic levels were different to TTL.

Till Eulenspiegel.

Had some time with this this afternoon and pleased to report progress, a couple of suitable caps have been found to replace the main can and were fitted. At switch on there was the reassuring hum of the auto-degauss and a very faint ticking from the PSU, no more fuse blowing. To my astonishment all the HT rails from the chopper were present and correct but the line stage was dead.
Shifting attention here revealed HT present at the transistor collector and as drive comes straight from a winding on the chopper transformer it had to be there so why no EHT? A prod at one of the earth eyelets from the heatsink produced a quick burst of EHT giving me quite a surprise, there are two earth eyelets on the heatsink and both weren't making contact. A cleanup produced EHT and audio but the set would trip every second or so.

Quite by accident I had been playing with the service switch and inadvertently left it in the service position, switching on the welcome rustle of EHT was heard and a few seconds later frame collapse obviously but no tripping. Suspecting a short in the field output stage didn’t reveal anything as all the all service switch does is to short out the field drive, not disconnect the supply as I was expecting.

While carrying out voltage measurements I became aware of a strange sort of bubbling noise, switching off quickly in case an electrolytic was about to let go I started to look for the cause and my eyes alighted on the cause. Not an electrolytic but one of those unreliable green Philips tuning caps, red hot to the touch and oozing it’s innards. I think I was rather lucky it didn’t fail o/c. Nothing to hand for this one, 10nF 5% at 1500v so rain stopped play for now.

Posted by: @jayceebee

Nothing to hand for this one, 10nF 5% at 1500v so rain stopped play for now.

Ready and waiting for you, an ERO .01uF 5% 1.5kV

Cheers Chris, many thanks.

With the showers we've had today I managed to get some bench time. The hot, gurgling and oozing tuning cap was replaced with the one kindly supplied by Chris. The set was powered on and the previous fault of tripping unless the service switch was set to kill the field output was still there as expected. I eventually traced this to a pot with a broken track in the N/S raster correction circuit, with nothing suitable to hand a couple of fixed resistors were fitted. This sorted the tripping and a raster of blue noise appeared, unfortunately this was short lived. After a few seconds running I saw out of the corner of my eye the raster suddenly fade along with the CRT heaters, the LOPT bobbin was also very warm.

After a break it was back to the job in hand, disconnecting the tripler I was now able to draw a decent arc from the output of the LOPT, phew! Borrowing the one from a donor FT110 and touch tune module which was missing managed to get something on the screen but it's not great. The colour is a bit strange, the convergence controls don't seem to have much effect and there is horrible screeching and tearing at high brightness. Still lots to do.

Phew indeed! When we spoke this afternoon about the symptoms, it was rather worrying LOPT-wise, glad to see it was not as feared. Now you've got something on screen to work with, the fun can begin. Love the look on the blue faced chap, Its almost as if the TV is saying "WHAT! You've woken me up from my long slumber, WHAT DO YOU WANT DAM-IT!" 😋