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 Post subject: Philips TF1705
PostPosted: Jul Wed 04, 2018 3:08 pm 
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Joined: Jun Sun 03, 2018 2:39 pm
Posts: 5
Hello everyone,

First, I would like to apologize for my far from perfect English.

I recently picked up a 1961 TF1705. I've been collecting and restoring radios for a few years now and can locate a problem in an AM tube radio fairly easily but when it comes to TVs I'm clueless. I started educating myself about them with "La télévision? Mais c'est très simple!" by E.Aisberg (also known as "TV? It's a cinch!" in the US) but it's still kind of a mystery for me and I have no idea where to start when it comes to troubleshooting the various issues I may encounter. I already posted about it on a French vintage radio forum (in fact it's the first result for this model) but I figured out there’s more people here with good knowledge of these early TV sets as these were quite rare here in France (high prices, rather poor coverage and only one channel, to put it into perspective only ~7% of the population owned a TV set in 1960).

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Now, onto the TV itself, it’s a VHF 819 line set with an additional UHF-625 transistorized tuner (Philips AT6370/30), probably added after 1964 for the second channel. You can easily switch between those two with a band selector on the side, which is really convenient as I don't have any VHF/819 sources.

The person I bought it from insisted on plugging it in, which makes me cringe in retrospective but at least I know the picture tube (which is marked as "renovated", rebuilt perhaps?) is good and the EHT works.
The first logical step was to clean the chassis and replace the bad caps while carefully checking if it matched the schematic. Thankfully, it’s mostly “mustards” and ceramics. I only had to change a few paper-in-tar capacitors, along with some dried out electrolytics. The set has been serviced: two new electrolytics dated 1975 were connected in parallel to the old, open ones.

Powered it up with a variac, connected a UHF RF source: nothing, no change in picture or sound. I’m pretty sure the tuner works because it manages to pick up some digital parasite sounds https://www.youtube.com/watch?v=XVcStnQhxRE which can also be heard on my only other TV with analog tuning, a crappy chinese one.

Out of curiosity I tested all the tubes I could test (the TV uses a combination of transformer + series string filaments with exotic voltages so I can't get a good reading with my tester):
PY82 (19Y3, half-wave rectifier): OK
EF80 (6BX6, RF pentode): OK
EBF80 (6N8, RF Double diode – Pentode): OK

While checking some components I noticed almost all the brown carbon composition resistors were out of specs so I changed them (except those in the RF and high voltage circuit, better safe than sorry), it will make it easier down the road: no improvements.

I also tried injecting a video signal on the grid of the video amplifier (EL183) but I later learned it wouldn’t work because the contrast is controlled by the tuner and my signal is too weak anyway.

My main issue right now is a worryingly loud flyback transformer: if I push some picture adjustments too far (increasing the luminosity or contrast) it gets really noisy, almost like it’s internally arcing (definitely not your typical flyback whine) and I start to momentarily loose vertical deflection. Could it be a worn out rectifier? (EY86 = 6AX2N = 6S2). You should be able to hear it in this video if you turn up the volume or use headphones https://www.youtube.com/watch?v=vVvkT9GlXzQ
At this point I’m quite hesitant to power up the TV, I really don’t want to let the magic smoke out of any unobtainable parts.

Could anyone point me in the right direction? I have an oscilloscope and a multimeter but so far, I have not poked around under the chassis.

https://i.imgur.com/5IqtwTY.jpg Schematic
https://i.imgur.com/9DQ0fFC.png Oscillograms
https://i.imgur.com/GbWpquB.jpg Wiring diagram


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 Post subject: Re: Philips TF1705
PostPosted: Jul Wed 04, 2018 7:22 pm 
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Joined: Apr Fri 28, 2006 12:46 pm
Posts: 1118
Location: Düsseldorf/Germany
Bonjour Monsieur!

I like to help you as I can.
First thing to say is that it is unusual that a set with a VHF/UHF switch from the 60s
still has a tube with ion trap!
You have a clean schematic, thats fine.
I have additional informations from Philips-France, just bought them in Riquewihr.
Until now I am not common with all the informations!
This will take a time, sometimes a long time.

Some clean pictures of the chassis will show me whether all bad caps are kicked out.

These Vitrohm resistors are a mess, you can interchange them in most sections, BUT
they (metal film resistors) only stand their voltage under 400 V DC!
Of course you have to check the resistors in the THT sections, too. If they are bad interchange
them with standard types.

It is not O.K. to bridge the old caps!!!!!!! Kick them out, once they burn the power supply
(alimentation) down.

To save you from X-rays of the THT redresseur construct a cage around the unit. Just get
some ideas from other TV sets.

You can buy here from a forum member a converter, this is a good investment:
http://www.tech-retro.com/Aurora_Design ... erter.html
Please ask him for details.
It really makes fun to see the old videos from Francoise Hardy, Sheila, Sylvie Vartan, Mireille
Darc, France Gall or newer good stuff like Mylène Farmer Corynne Charby or Nolwenn Leroy
on that old screen!

DON`T FORGET, this set will have a life chassis, use a transformer to be earth-free.
Anyway, there is no reason to touch something.

Please control the vertical oscillator, could be a bad control. If that case is cleared check
the line frequency, You will have two controls, one for 819 lines and one for 625 lines!

Bonne chance!
Monsieur Télévision 8)

_________________
From all the things I ever lost I miss my mind the most
ScottyBeamMeUpThereIsNo 4/3-TV/AM OnEarth


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 Post subject: Re: Philips TF1705
PostPosted: Jul Thu 05, 2018 1:11 am 
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Joined: Aug Thu 20, 2015 3:09 pm
Posts: 904
Location: Albion, CA, USA, 95410
I can't help with your questions but I do want to say that you have great English and your tv set is beautiful!


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 Post subject: Re: Philips TF1705
PostPosted: Jul Thu 05, 2018 4:10 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5336
Location: Woodinville, WA USA
That's a beautiful set, and an interesting project.

I'm not familiar with this type of European TV, but I would like to stress SIXMILLION DOLLARMAN's good advice about the newer electrolytic capacitors wired in parallel with the old ones. That is a bad service technique. I would disconnect the original caps (and replacements) completely and install new electrolytic capacitors with the correct values.

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html


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 Post subject: Re: Philips TF1705
PostPosted: Jul Thu 05, 2018 6:53 pm 
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Joined: Jun Sun 03, 2018 2:39 pm
Posts: 5
Hello,
Danke für Ihre Hilfe! :)

Unfortunately I lost the pictures of the chassis before I started replacing components
Here it is before replacing all the out of tolerance brown carbon resistors (which are, I suppose, those you call Vitrohms) with standard 2w ones: https://i.imgur.com/uJ965Mu.jpg
And after: https://i.imgur.com/Yuo2J56.jpg
The three film capacitors (circled) I left were tested for capacitance and for leakage at 400v, not sure about the mustards though.
From experience 50s/60s Philips higher end radio and TV sets are usully over-engineered.

I'm aware of what happens when you leave a dead capacitor in parallel with the new one and I didn't want to risk it, it's a no brainer for me. In fact I replaced all the filter caps even though one of them had acceptable leakage. The old cylinder ones were emptied and their base used as a terminal strip or socket for the new capacitors

Is the lack of shielding around the flyback transformer an issue? Seems like it was designed that way (same thing in this 1958 TF1795A which has an almost identical chassis) so I'm quite hesistant to change that, for now. However I'm still worried about that loud flyback. The fact that I loose vertical deflection when I increase the brightness means "something" is being overloaded in the circuit and that ain't good, if it's a tube I can always buy a new one or find a replacement, if it involves any coils and transformers I'm screwed! I really want to fix that or understand what's causing it before moving on to other stuff.

Regarding the converter, I'm not a TV collector so it's a little bit over my budget. Someone else created a 819 line modulator which may worth a try http://819lignes.free.fr/Realisation_d_ ... F_F8A.html but for now I will stick to the 625 UHF mode.

Sorry for the dumb question but where do I check the line frequency in my TV? (which should be 20475hz and 15625 hz if I'm not mistaken)

Using this TV to watch 1960s yéyé artists once it's fixed is definitely on top of my list. Besides, its appearance is definitely something I enjoy about it, it has a modern look you may find in later TVs while still retaining some 1950s elements. Unfortunately mine is missing its legs and the white border inside the frame but you don't notice it and as for the legs it shouldn't be too hard to find.


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 Post subject: Re: Philips TF1705
PostPosted: Jul Thu 05, 2018 7:34 pm 
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Joined: Apr Fri 28, 2006 12:46 pm
Posts: 1118
Location: Düsseldorf/Germany
Bonsoir!

In real you have a dual standard set ( bi-standard )!
When switching from VHF to UHF you change the line oscillator.
There has to be some cables to 2 coils and 2 controls.
You will see that on the schematic.

Do you have a tested and working source for a clean picture?
The minimum is a "mire".

The VHF modulator doesn`t help you much, with this device you are on the
right channel frequency but you still have no 819 lines image!
That is the major point for the price of the aurora!
You can connect your vcr, dvd or satellite system with the AURORA and
the exit gives you a clean picture with the right sized voltages like it was yesterday.
I am sure your next TV set is one without UHF, so you can`t get around an AURORA.

Vitrohm sold lousy resistors. They are common in german Philips sets, not so much
in french sets.

A dead cap is not a part of a TV set, out with them! Your TV is not a cap museum!
Did you check the line transformer for a broken brass bracket?
In rare cases they brake, then they get loud.
Loosen screws?

Regards,
SIXMILLION DOLLARMAN

_________________
From all the things I ever lost I miss my mind the most
ScottyBeamMeUpThereIsNo 4/3-TV/AM OnEarth


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 Post subject: Re: Philips TF1705
PostPosted: Aug Thu 23, 2018 11:31 pm 
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Joined: Jun Sun 03, 2018 2:39 pm
Posts: 5
Hello there,

I'm back! Sorry for not providing any updates on the repair but between work, holidays and the slow progress I was making by myself I’m not sure it would’ve been relevant.

Thank you for your input, it really helped me familiarize with these old TVs.


Regarding my concerns with the sudden losses of vertical deflection, I noticed what seems to be arcs inside the DY86 EHT rectifier. Replaced it with a DY87 (dirt cheap on eBay) and it fixed the problem!
While taking a look at the UHF tuner I noticed the tuning knob had some kind of fine tuning feature (or was simply stuck due to aging rubber parts). Basically it has a limited "range" in which you can turn it freely but if you want to go further you have to put some force to get to the desired frequency. Once I figured this out I was finally able to hear the sound I was feeding into my UHF modulator! Success!

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As for the picture, it still had some issues: the lines were going crazy and the flyback was not too happy about it. I suspected a bad horizontal output tube (PL36) and after replacing it (mainly because I broke the original one by pulling it by the glass, don't do that). Bingo! I have perfect sound and a picture, what more could I ask for?

Image

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Well, a better picture of course. I need some advice on a few problems:

- There’s a brighter area at the top of the screen (you can see it above) and it stretches/distorts the picture. I’ve read somewhere it could be a bad vertical oscillator and sure enough, both the triode and pentode of the PCL82 tested under minimum value (in fact both PCL82 tested low but the other one is the sound output so I won’t bother for now). Should I invest in a new one?

- The gap between each line is excessively big. It’s hard to see on the photo but it’s there.

Image

- The picture adjustments knobs don’t do much, especially picture height. It just kind of “bounces” up or down and then slowly go back to its original size.

I still can’t get hold of an isolation transformer so for now I can’t check anything with my scope, which would make everything way easier.

I also got myself a pattern generator: Centrad Mire Electronique 783 https://www.radiomuseum.org/r/centrad_m ... e_783.html which is still on the bench as it contains tons of paper-in-bakelite caps which are all leaky and drifted really badly. It supports both 819 and 625 line so once it is running properly I will be able to make the final adjustments.


I have a final question for SIXMILLION DOLLARMAN about the AW43-80 picture tube: according to the schematic, this tube requires an ion trap and on the DocTSF page of the set you can see what seems to be one https://www.doctsf.com/grandlivre/fiche.php?ref=12090
However mine doesn't have any ion traps on it and on the radiomuseum page for the tube https://www.radiomuseum.org/tubes/tube_aw43-80.html someone says he had a similar tube which clearly said you shouldn't put an ion trap on it. Also, my tube was rebuilt with a newer socket (picture) so maybe this doesn't require an ion trap? How do I know if it needs one or not? Honestly I'm really confused about it :?


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 Post subject: Re: Philips TF1705
PostPosted: Aug Fri 24, 2018 1:13 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 437
If the tube was rebuilt it almost certainly will not need an ion trap because a newer type gun was fitted and the screen is aluminized anyway.
Hey, if it works without it, it does not need it. Simple!!

Tubes that require ion traps have what is called a bent gun. You can recognise this inside the neck, some of the metal cylinders are cut at an angle of about 15 or 20 degrees.


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 Post subject: Re: Philips TF1705
PostPosted: Sep Sun 02, 2018 1:13 am 
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Joined: Jun Sun 03, 2018 2:39 pm
Posts: 5
It's almost done. I replaced the PCL82 vertical oscillator/output tube and I get correct space between each lines. I also had issues with the adjustments pots not doing anything: turns out they drifted really really bad. I have 63k, 620k and 598k for what was supposed to be 50k, 350k and 350k. I fixed it with parallel resistors to bring their value down. It's not perfect but since I can't find any suitable replacements for now (it's quite unusual both in value and shape) it will do the job. However the picture is still stretched near the top and changing the picture height kind of fixes that but at the expense of having some black lines at the bottom. In fact I encounter the same as issue as johnfin in his post. I will try to figure this out. edit: ok, the exact term is vertical linearity, that should make this easier
I also need to build a cage around the EHT power supply. A spark coming from the exposed back of the socket of the EHT rectifier zapped me while I was changing a tube (set turned off) and I did not enjoy that.

Image

On the topic of EHT, I get a really bright dot when I turn off the TV. Not immediately though, it’s not the your regular vertical and horizontal collapse. When turned off, the picture simply disappears and after about 2 seconds, a really bright dot appears and stays for about 2 or 3 seconds before starting to fade in about 10 seconds. It also appears when I slowly decrease the voltage with my variac down to zero and interestingly enough, it does not appear before. If keep the set at, let’s say 10v it will not manifest itself. However if I quickly go from 10v to 0v and then back to 10v it disappears almost instantly.

I’ve heard about suppression circuits getting rid of that, can someone tell me from the schematic if my TV have this and what it looks like? I have absolutely no idea what to look for. I know these circuits can fail to work properly if the tube is weak and do not solicit B+ enough but in my case it was rebuilt around 1976 and looks really bright and sharp so it can't be that.

@irob2345 Thanks for the tip, I wasn’t able to find much documentation about ion traps so my knowledge on these is quite limited. I thought it was like one of those leaky grid coupling capacitor, not noticeable by the end user until it kills the tube.


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 Post subject: Re: Philips TF1705
PostPosted: Sep Fri 14, 2018 8:00 am 
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Joined: Jun Thu 25, 2015 3:21 am
Posts: 1257
baguette an ion trap was used to prevent ion burn on the crt before they had an aluminized crt. the electron gun on the crt was cut on an angle so the ions and electrons would hit the crt neck. the ion trap would bend the electrons back so they hit the phosphor on the crt face but not the ions. without this over time you would get a dark circular spot in the center of the crt called an ion burn.

if memory serves if the crt needs an ion trap you would not get any light on the crt if the ion trap is off.

it looks like your vertical linearity is off. im not familiar with european test patterns or televisions but i think the egg shaped thing in the center of the test pattern around the square should be a circle. does adjusting the vertical linearity control change this?

i wouldnt worry about the dot after you turn off the tv. if what u are experiencing is what i think it is then its normal.

the suppression circuit modification i am familiar with would be to suppress retrace lines and you dont have them. by the 1960s the tv has that built in.


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 Post subject: Re: Philips TF1705
PostPosted: Sep Sat 15, 2018 6:01 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 437
Regarding "spot suppressor" circuit, the most common arrangement is to have the CRT biassed to maximum brightness as the HT fails on turn off. This results in a white flash that discharges the EHT.

If the EHT is not discharged, the bright dot will appear after the scan stops.

Reasons for no discharge include low emission CRT (yours is OK) and an open circuit aquadag earth on the CRT. The aquadag is the graphite coating around the bulb. There should be some means in place (e.g. a spring loaded braided wire) to ground it to the chassis of the TV.

Some TVs rely on a large capacitor on the B+Boost line to hold a charge long enough to ensure that the CRT has enough gun voltage to conduct in the half-second or so after switch-off, while the scan is collapsing. Most Philips TVs I've seen have been designed to flash a white rectangle after switch-off - the effect is quite pleasing!


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