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Old 11th Oct 2020, 2:37 pm   #1
Heatercathodeshort
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Default Stella CT1100.-Philips 11TG190AT 1968

This Stella badged Philips CT1100/11TG190AT has been put away, wrapped in plastic since I brought it home from the rubbish tip over 20 years ago.

It was manufactured in January 1968 at the Philips Croydon factory that was based at Commerce Way Croydon. The factory code is BA with the date cod3 1/68 one of the very last produced.

It is a 405/625 transistor 11" mains battery portable first produced in 1966 and was an instant hit with caravan owners. It does contain just one valve, the EHT rectifier type DY51 the 1.4v version of the well known EY51.

Examination revealed that this particular example has had very little use. The chassis and components look as new including the EHT lead and connector as can be seen in the pictures. I don't think the attached aerials have ever been extended.

It required very little to return it to it's new condition. The AD149 regulator transistor had a dry joint at it's base connection and when tided up worked faultlessly on both mains and 12v battery.

It has incredible gain and must have pulled in a picture in many remote beauty spots where others had failed.

The chassis has an impressive number of semiconductors, 48 in all including a pair of L.T. metal rectifiers. It is very well constructed with a steel frame supporting the printed panels, tuners and CRT a Mullard A28-13W/14W It must have been expensive to produce and a credit to it's designers.

Back in the day I used to service a number of these receivers. The majority of the faults faults were on the I.F. panel, mainly the transistor types AF115 and AF181 in the sound and vision stages.

I did have one brought it in that had been plugged into the mains accidently via the battery input plug. The owner had connected up a 13amp socket in his caravan supplying 12v to the TV via the vehicle battery. The TV battery lead had a 13amp plug on it.. On arriving home his young Son had carried it into the house and plugged it into the mains....

I didn't hold out much help but on the bench I discovered that the CRT had an O/c heater and the regulator was blown up. The customer was more than willing to pay quite a large repair bill and picked the replacement tube up for me from CES at 604 Purley Way. The 11TG was quite an expensive receiver and if I remember the tube was around £15.00. A lesson learned.

The performance on both 405 and 625 is absolutely brilliant. I think it was one of the few dual standard mains battery portables produced sitting in line with the Sony 9-90 and the much lesser known Teleton TA12DU.

I also have the Philips version stacked away. I must give it some mains sometime and see how a heavily used one compares. John
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Old 11th Oct 2020, 2:39 pm   #2
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Another five pictures. The digital camera ruins the actual quality. J.
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Old 11th Oct 2020, 3:12 pm   #3
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

I fully agree with your comments on this set. They are very sensitive and produce a lovely crisp and detailed picture, especially on 625/UHF working.

I used mine in the last few years of VHF/405 transmissions to monitor the transmission quality, which was usually dire by then.

I have had a few of these with very leaky close tolerance ceramic capacitors inside some of the IF cans. They were made by Philips and have no protective coating, which might explain their poor long term reliability.

I was lucky enough to find a set fully populated and undamaged PCBs at Manor Supplies (many years ago!).

The later production sets had green solder resist on (at least) on the large PCB at the bottom. They also had the chassis punched to allow the fairly big “can” electrolytic (that was previously taped to the top RHS chassis angled section) to be properly mounted.
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Old 11th Oct 2020, 3:14 pm   #4
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

That's a great little set John and as you say looks in as new condition.

I have two of these sets, both Philips. One is fully working and the other in the to do pile. On my working set, there's a difference to the 405/625 standard switch buttons on the front of the set, the lower button is red in colour which I think denotes an early version. The other set, like your Stella has all cream colour buttons.

I remember having one in for repair back in the early 1980's and that particular set also suffered an o/c CRT heater. ISTR there could be a problem if the 11V rail shot up due to a fault in the regulator or an intermittent preset (set 11V). I wondered about adding a crowbar circuit to protect the heater in the event the 11V rail should rise excessively. Has anyone devised a simple circuit to protect the heater?

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Old 11th Oct 2020, 4:10 pm   #5
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

This one has the usual brown P/C board not the easiest to gain access to. How you discovered those faulty caps in those printed circuit cans is incredible. I never had that one but did have a couple of O/C tube heaters not caused by the regulator. They must have been quite delicate. Maybe just the addition of a 12v zener across the tube heater may prevent a disaster.

One thing you have to watch when servicing any Philips TV from the mid 60's to the G8 are these nasty plastic anchor clips.

They are fitted between the Dag earthing springs and the chassis or cabinet. When they snap the earthing spring/braid flies across the chassis and often shorts something out with the usual disaster. It used to pop the field output transistors in the G8. The 210/300 series were prone to this but being hybrid, damage was less likely.

One had fractured in the 11TG and I think I just caught the remaining three in time. John.
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Old 11th Oct 2020, 5:09 pm   #6
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Quote:
Originally Posted by Heatercathodeshort View Post
T

One thing you have to watch when servicing any Philips TV from the mid 60's to the G8 are these nasty plastic anchor clips.

They are fitted between the Dag earthing springs and the chassis or cabinet. When they snap the earthing spring/braid flies across the chassis and often shorts something out with the usual disaster. It used to pop the field output transistors in the G8. The 210/300 series were prone to this but being hybrid, damage was less likely.

One had fractured in the 11TG and I think I just caught the remaining three in time. John.
That had happened to the one I have. I can't remember how I overcame the problem now but it might have involved the creative use of plastic curtain clips....!
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Old 11th Oct 2020, 5:57 pm   #7
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Thin cable ties or nylon cord works a treat. If you encounter the white clips, replace on sight! J.
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Old 11th Oct 2020, 7:52 pm   #8
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Interesting to hear your comments about the performance on 625, mine is superb on 405 but 625 is not good. Having never seen one of these working in it's heyday I wondered if it was typical. There is a vast difference in the amount of contrast between the two standards (contrast pot is common to both standards), on 625 together with intercarrier buzz there is a tendency for verticals to be S shaped, it's not smoothing. The line scan switch over contacts feeding the scan coils have been badly heat damaged and carbonised due to arcing but thankfully I do have a replacement switch courtesy of Malc Scott. The pics apart from the first are shown with it hardwired.

Construction of a new workshop is well underway so aim to get it on the bench soon and hopefully sort it.

John.
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Old 11th Oct 2020, 9:00 pm   #9
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

I agree. I was quite surprised at the contrast range on UHF with this particular model. I remember that most if not all appeared to have lower contrast on UHF but as very few customers actually viewed BBC2 it was never referred back to Philips for a possible modification.

The Philips version I have does suffer from a lower contrast range when it was last powered up around 1985! I will bring it out of retirement and compare.

I will post a picture of UHF operation ASAP. John.
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Old 12th Oct 2020, 11:26 am   #10
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

A couple of UHF pictures taken this morning. Contrast set about 3/4 advanced. Normal exposure on Samsung camera phone. The pictures represent very closely to the results on the screen. This is a good one! I will get the Philips version out of storage this afternoon. John.
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Old 12th Oct 2020, 4:38 pm   #11
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

This afternoon I uncovered the Philips version. This has been stored away uncovered for very many years.

It has had quite a hard life. It is very grubby with both aerials broken off. The slide on cabinet feet have been removed presumably to allow it to fit into some kind of kitchen [?] cabinet.

Amazingly it worked straight off! The picture was small all round but checking the supply rail showed it was spot on at 11v.

To cut it short we had two faults. The 6.8K resistor in series with the height control had risen to 9K and for some reason the line linearity coil/magnet was hopelessly out of adjustment causing the lack of width! It had me thinking for a while.

With this sorted and the cabinet given a wash and brush up the results are very good. The tube has lost a bit of the sparkle that the Stella has but it's still a very good picture on 405 and 625.

The pictures show before I sorted out the picture size [405] on first switch on and the UHF picture showing a box format film! It looks at first sight that the picture has shrunk again.

The date code is 4/67 midway through production.

An interesting adventure into a couple of British manufactured all transistor portables.
John.
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Old 12th Oct 2020, 7:47 pm   #12
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Hi John,
The Philips version of your Stella set was introduced in 1966. The Stella brand was distributed through wholesalers. I don't think there is such a thing as wholesaler to the retail trade that sells TV sets.
My set is the Philips "TVette" 11TG190A.

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Old 12th Oct 2020, 9:42 pm   #13
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Hi John.
I've a couple of these and they work superbly. I added a 100ma time lag fuse in series with the CRT heater supply feed and a 12v zener across the heaters. I can confirm it blows the fuse above 13v thus saving the CRT if the PSU does a wobbly, simple quick mod.
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Old 12th Oct 2020, 10:44 pm   #14
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Your little Stella looks rather nice! I’ve got the Philips version here, got it for £10 at Newark antiques fair many years ago, complete with the correct mains lead. Sadly the CRT heater was O/C but I managed to get it to work again by using the heater welding trick, using the power supply for a CCFL on it! It worked very well for a good few years after that, but recently it died again, and I’ve been unable to repeat the earlier success on the tube heater, so now the set is merely for display only. I have wondered about replacing the tube with a slightly smaller one and making up some sort of mask for it, but I guess it would look daft!

Regards
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Old 13th Oct 2020, 9:44 am   #15
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Quote:
Originally Posted by murphyv310 View Post
Hi John.
I've a couple of these and they work superbly. I added a 100ma time lag fuse in series with the CRT heater supply feed and a 12v zener across the heaters. I can confirm it blows the fuse above 13v thus saving the CRT if the PSU does a wobbly, simple quick mod.
That sounds a really good idea and something that could be added to the BRC 1590 tube heater supply.

Great job John that's a two good examples you have got there. I have a Philips version gathering dust which I have not switched on yet.

I think most dual standard sets produced a different looking picture on 625 always looking more grey and flat compared to 405.
There were only a couple of dual standard black and white TV's, that I know of, that gave good pictures on both systems.
A lot of this was down to using Mean Level AGC plus AC coupling of the video output to the cathode of the CRT which was ok on 405 but not so good on 625.
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Old 13th Oct 2020, 12:46 pm   #16
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Quote:
Originally Posted by murphyv310 View Post
Hi John.
I've a couple of these and they work superbly. I added a 100ma time lag fuse in series with the CRT heater supply feed and a 12v zener across the heaters. I can confirm it blows the fuse above 13v thus saving the CRT if the PSU does a wobbly, simple quick mod.
Thanks for that tip Trevor. That's a very worthwhile mod to save the tube with minimal disruption the the set. I suppose a BZX61C12V (1.3W) would be suitable as I have a few of these to hand. I had originally thought about a crowbar circuit but is not really necessary in this case.
As Hybrid tellies mentions it would be equally useful to employ the same mod to other sets . I also have a BRC 1590 that would be well worth adding the zener and fuse to protect the CRT heater.

It's a wonder why the manufacturer didn't incorporate such a modification, cost no doubt.

Regards,
Symon
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Old 13th Oct 2020, 12:55 pm   #17
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Hi.
I believe the heater current is just 80ma on these tubes so a time lag or slow blow 100 ma fuse takes care of the initial inrush current of the cold heaters, a 1.2 watt 12v zener is fine in this application as it will clamp the voltage to just below 13v and the fuse will pop.
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Old 13th Oct 2020, 1:12 pm   #18
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

Certainly a worthwhile addition Trevor especially the Thorn 1590 chassis.

I have mentioned before how important it is to check the L.T. adjust pot on the 1590 series. It rises in value and as it does so the LT increases until a hum bar becomes apparent on the picture.

Too late! The CRT will be over run and will have been for a long period.
The addition of the diode and fuse would certainly prevent this disaster. John.
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Old 14th Oct 2020, 11:15 am   #19
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Default Re: Stella CT1100.-Philips 11TG190AT 1968

The Philips and Stella on the bench together. The Philips is supplied with 405 and the Stella 625 other than the test card shot to compare the two. The Philips has a slightly tired tube but still gives a good picture.

I had to make up some cabinet feet for the Philips. It takes longer than you think! Regards, John.
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