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Philips TVette (11TG190AT)
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July 16, 2017
9:54 pm
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Jayceebee
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Just as well it low as going it high would be pretty scary with respect to the fragile CRT heater, wonder if it might be a good idea to fit a simple crowbar circuit for protection.

The aquadag earth strap on mine is held by plastic hooks, two with springs and the sleeving at the midpoint is simply held by a metal hook pressed out of the chassis frame.

John.

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July 16, 2017
10:13 pm
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sideband
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Thanks John.

I spent a little time this evening and worked out the top plastic hooks but it was the one at the bottom underneath the tube that had broken. What I did in the end was to use one of the top plastic hooks for the bottom anchorage and then replace the 're-purposed' top hook with a piece of wire. It involved removing the tube (well loosening it so that I could get to the metal hook underneath it). Fiddly but at least now we have an earthed tube again and it's all working now having resoldered the dry joints in the power supply. The main remaining fault is the crackly sound (which can be temporarily cured by tapping one of the AF115 sound IF transistors) so I'll probably replace that with an AF125 and then just tweak the width and line linearity.  That should just about be it.

July 17, 2017
11:39 pm
acj1980
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Nice little Telley,

is it All-transistor, and what year is it from, it seems to be a little bit similar to the Philips 11lx522 from 1965.tele07_gif

 

Alex 😉 

July 18, 2017
8:26 am
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sideband
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Hi Alex. Welcome to the forums! 

The TVette is all transistor apart from the EHT rectifier which is a valve (DY51). It dates from around 1967-69. I'm not sure exactly when they first appeared on the market but there were plenty around in the early 1970's when I started in the Trade. There is a serial number on mine but I'm not familiar with the early date coding. Mine uses AF11x series transistors so probably dates it mid to late 60's.

In UK, we started using UHF (625 lines) in 1964 when BBC2 started. As this set is dual-standard it ties in with the mid-late 60's date. 

July 18, 2017
2:24 pm
acj1980
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sideband said
Hi Alex. Welcome to the forums! 

The TVette is all transistor apart from the EHT rectifier which is a valve (DY51). It dates from around 1967-69. I'm not sure exactly when they first appeared on the market but there were plenty around in the early 1970's when I started in the Trade. There is a serial number on mine but I'm not familiar with the early date coding. Mine uses AF11x series transistors so probably dates it mid to late 60's.

In UK, we started using UHF (625 lines) in 1964 when BBC2 started. As this set is dual-standard it ties in with the mid-late 60's date.   

Thanks  "Sideband ;-), okay i think you´re right about the years, it is around late 60ies, the EHT rectifer came on the market around 1970.

Woow that´s was very early BBC2 started, Denmark was the first Country in Scandinavian who get TV station, but the last who gets a second station, first i 1988, the gouverment talks and talks but nothing happens until late 1980ies :-/, the second Tv station transmit on the UHF band

 

Alex 😉 

July 18, 2017
2:37 pm
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Chris
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Hi Alex, here are some of the UK TV milestones you might not be aware of https://www.radios-tv.co.uk/a-brief-history-of-analogue-tv-milestones-in-the-uk/

July 18, 2017
2:39 pm
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nuvistor
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We had two 405 VHF stations, Independent TV (ITV) with commercials started in London in 1955 and then expanded around the country, the main transmitters were soon built but it took many years for around 95% coverage. ITV started in my region in 1956.

BBC2 started as stated on 625 UHF in 1964, again the main transmitters quickly came online but it took a while longer for nearly full coverage. BBC2 started in my region in 1965.

Single station colour with BBC2 in 1967 with 3 station colour in 1969.

Edit

There you are, Chris has posted  much better information.

Frank

July 18, 2017
2:57 pm
acj1980
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thanks to both of you for updates, it is very interesting to read, i really wonder why Denmark was so D*mn slow :-O commercials on nation wide television startede here, when our second tv station started in 1988, 

How about the old 405 line system, and the newer 625, why do the britains keep the 405 system in so many years?

i know we in 1948 have a British group in Denmark and introduce the 405 line, in same tine we get introduces for the 625 system, and the decision was locked on the 625 

 

Alex 😉

PS. sorry for this off-topic 

July 18, 2017
3:13 pm
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sideband
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Just for your interest Alex, I still have the TV my mother bought new back in 1964 so that we could watch the start of the UHF BBC service. The TV is now 53 years old, still going strong since I restored it about 10 years ago.

July 18, 2017
3:21 pm
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sideband
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acj1980 said

i know we in 1948 have a British group in Denmark and introduce the 405 line, in same tine we get introduces for the 625 system, and the decision was locked on the 625 

 

Alex 😉

PS. sorry for this off-topic   

Probably 625 was decided because the rest of Europe also adopted 625. 405 was, as far as I know, uniquely British and it was kept on for so long simply because (a) it was a good system and (b) to make sure that 95% of the country was able to receive UHF 625 by the time it was decided to turn the old 405 system off.

 

We don't mind slightly wandering topics here! We can always start a new thread from this one if necessary. 

July 18, 2017
3:22 pm
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nuvistor
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Lots of information on this archived data, thanks to a Chris for saving it.

http://radios-tv.co.uk/Pembers.....index.html

Frank

July 18, 2017
11:32 pm
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ntscuser
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acj1980 said
Nice little Telley,

is it All-transistor, and what year is it from, it seems to be a little bit similar to the Philips 11lx522 from 1965.

Both sets date from 1965 I believe but whereas the T-Vette was almost all transistor the 11LX522 'Philetta' was a hybrid valve-transistor design. I think the only thing they shared were the picture tube and the HT rectifier.

acj1980 said
How about the old 405 line system, and the newer 625, why do the britains keep the 405 system in so many years?

Reception of 405-lines on VHF was much better than 625-lines on UHF, especially on portable sets with their rudimentary aerials and in areas with a weak UHF signal.

July 19, 2017
10:36 am
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sideband
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ntscuser said

Reception of 405-lines on VHF was much better than 625-lines on UHF, especially on portable sets with their rudimentary aerials and in areas with a weak UHF signal.  

Also the early tuners using germanium transistors were not so good on UHF in weak signal areas where noise on the picture was a problem. 405 VHF on the other hand wasn't a problem and was usually receivable almost anywhere.

July 23, 2017
11:12 pm
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sideband
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I've been plagued with intermittent problems on this set due mainly to dry joints but I'm getting there and I've just replaced the AF117 audio amp/AGC transistor with an AF127. That has cured the annoying intermittent crackle on sound. I'm left with an intermittent power supply problem which only shows up when the PCB's are fitted back in the frame......

 

The 11V supply is dropping down to around 6V and at the moment, has defied all attempts to trace the problem. I've put it to one side for a few days.

 

One thing I would like to confirm with anyone who has one of these. On mine, there is a 2000uF capacitor strapped to the metal framework at the top, secured by an adjustable plastic strap. Philips may have had some odd quirks and done some unconventional things but they were not in the habit of strapping capacitors in with plastic straps! It's connected to the collector of the AD149 in the power supply and I think it might be in parallel with the other one mounted on the chassis. If it is, then was it a later mod or was it a lazy engineer who couldn't be bothered to remove the other one....?

It's not shown on the wiring diagram.

 

js640_SAM_1353.jpgImage Enlarger

This doesn't look right.

 

js640_SAM_1355.jpgImage Enlarger

When the power supply is behaving

it's looking good.

July 24, 2017
11:04 pm
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sideband
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I've answered my own question....the additional 2000uF is a 'circuit change' according to the Trader sheet.....only just noticed the comment.

 

Had a quick play tonight and put a meter in series with the 11V supply from the AD149. Current starts off at around 720mA which seems ok. Over the next 15 minutes, it gradually creeps up and when it gets to around 1.1A, the power supply folds and the 11V supply starts to drop rapidly. This leads me to conclude that the power supply is in fact OK and the fault lies elsewhere. I can't help thinking that it's not the line output stage simply because there is absolutely no change in width or height until the moment the power supply folds and the supply drops rapidly. Now when I remove the PCB's and run them on the bench, the set seems to run OK....an hour yesterday. The only difference is that the line stage is then in free air rather than in a screened compartment and obviously runs cooler. Next session, I will connect a meter in series with the LOP transistor and measure the current that it draws during normal operation and fault mode. I'll do this with the PCB's fitted to the chassis so that the line stage is running in its screened enclosure. 

July 25, 2017
5:59 pm
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PYE625
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It sounds almost like poor thermal compensation of bias conditions drifting somewhere, as the set warms. 

Perhaps a careful squirt of freezer spray in likely areas may help to narrow it down.

I'm thinking thermistor's in power amplifier stages.... audio or frame for instance.

Andrew.                                                                                   

                         

July 25, 2017
6:25 pm
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Jayceebee
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So that electrolytic is an official mod, not fitted to mine so it does look as though yours is an early production model. That tie wrap material looks identical to the stuff Thorn used to secure the EHT tray to the jelleypots.

For the excess PSU current, if it was the line stage like you, I would have some signs such as foldover occurring after a few minutes at the one edge or centre. My next check would be a finger on the audio output transistors, AC127/128 output stages of the time were prone to thermal runaway.

John.

July 25, 2017
6:35 pm
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sideband
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These sorts of problems can be challenging to trace. My plan is to hook a meter to measure current on the main 11V rail (from the collector of the AD149) and then use another meter to measure current in strategic places like the line stage. That way I hope to be able to narrow the problem down. The meter in the 11V rail will warn me when the current is rising and then I can watch the other meter to see if that is measuring a current rise as well.

 

The puzzle is that there is no change at all in the width or height suggesting that line and field are running fine. The picture only collapses when the power supply throws in the towel after trying to supply excess current. If you switch off and on again, the set will immediately work for some seconds before it all collapses again. 

 

I would have thought that if either field or line were starting to draw excess current, the effect would be seen on screen.

 

It has to be heat related.

July 26, 2017
1:52 pm
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sideband
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Jayceebee said
So that electrolytic is an official mod, not fitted to mine so it does look as though yours is an early production model. That tie wrap material looks identical to the stuff Thorn used to secure the EHT tray to the jelleypots.

For the excess PSU current, if it was the line stage like you, I would have some signs such as foldover occurring after a few minutes at the one edge or centre. My next check would be a finger on the audio output transistors, AC127/128 output stages of the time were prone to thermal runaway.

John.  

Crossed with your reply John! Yes agree width and height would probably change if the fault was in those areas. The sound seems to be OK but maybe I can detect a slight amount of distortion in the lower frequency sounds, some male voices sound decidedly 'grating'.....not sure but certainly will be one of the areas of investigation. I've had AC12x transistors in radios fail with thermal runaway before and drawing something over an amp from a PP9.........!

 

Actually you've just given me an idea....I noticed the possible distortion after removing the PCB's for the first time....a bit like a rubbing speaker but not quite. It might be worth checking the bias pot....the bottom PCB is a bit of a job to remove and it's possible it got moved while fighting to get the PCB out. When I replaced the AF117 AF amp/AGC transistor I was going to check the bias afterwards and never did......

July 26, 2017
2:07 pm
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Focusdiode
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Worth mentioning a bizarre fault I had on one of these sets. All seemed well on normal viewing but tuning between the channels resulted in the frame collapsing to a white line then opening out when tuned in

The cause was simply due to a dry joint in the frame output stage.

Brian

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