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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 16th Nov 2020, 5:10 pm   #1
Richardgr
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Default Philips GM2891

I have this bit of kit that I picked up cheap, packed chockablock with ECL80's.

My original plan was to convert it into a guitar amplifier, salvaging the case, chassis and possibly transformer (if it is powerful enough).

That was before I discovered this site, and now I realise that there are people out there looking after old tellies.

I expect that every service shop used to have one of these once upon a time, so there should be no shortage of them out there.

Is this a sought after piece of test equipment, or can I try and repurpose it with a clear conscience?
Philips GM2891
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Old 16th Nov 2020, 8:25 pm   #2
Maarten
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Default Re: Philips GM2891

How rare it is ight be determined by the factory of origin and the exact signal specs. Do you have a picture of the type plate?
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Old 16th Nov 2020, 10:50 pm   #3
Richardgr
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Default Re: Philips GM2891

Quote:
Originally Posted by Maarten View Post
How rare it is ight be determined by the factory of origin and the exact signal specs. Do you have a picture of the type plate?
Yer'tis ...
It is made by Philips, and looks like it is designed for 625 lines.
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Old 17th Nov 2020, 1:02 am   #4
Maarten
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Default Re: Philips GM2891

The factory of origin is Philips Netherlands, as is most common. There was a small possibility that sets like this were also made in other Philips factories (amongst others, Philips Sweden, Denmark, Germany produced various measuring instruments as well), hence my question. I don't think this variant is particularly rare, but a TV collector of 1950's sets might be happy with it as it looks in quite a good condition.

When I build something out of existing equipment, I mostly use incomplete or not really worthwhile to repair equipment. I'm not sure what to advise in this case, really. On the one hand, if you don't have local TV collectors or find someone who will take it via ebay, it isn't worth that much for you to keep it as is. On the other hand, someone might turn up the day after you repurposed it who would have gladly taken it.

Last edited by Maarten; 17th Nov 2020 at 1:10 am.
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Old 17th Nov 2020, 7:53 am   #5
Richardgr
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Default Re: Philips GM2891

Hi Maarten,
Thanks for the reply. It was bought in Sweden, and all electrical equipment of that age would have had to have been S-markt (like the BSI kite mark) to have been connected to the mains, so probably assembled in Sweden from imported parts.

It is solid, with a quality feel, and must have cost a few bob when it was a necessary addition to the workshop.

It is well down the project list, so I can always be contacted if it has some significance.

Cheers! Richard
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Old 18th Nov 2020, 2:43 am   #6
rambo1152
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Default Re: Philips GM2891

This instrument falls loosely into the category of test equipment known in the TV repair trade as "crosshatch generators".
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Old 19th Nov 2020, 8:21 pm   #7
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Default Re: Philips GM2891

I have the 819 line version, GM2891-13.
A beautifully made piece of equipment.

DFWB.
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Old 19th Nov 2020, 10:47 pm   #8
gingpeakin
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Default Re: Philips GM2891

Please can we see inside this lovely beast?

Ta

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Old 20th Nov 2020, 12:30 am   #9
Richardgr
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Default Re: Philips GM2891

Hi Ging, there were some decent pics on the radiomuseum site, linked to in the first post.
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Old 21st Nov 2020, 10:52 am   #10
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Default Re: Philips GM2891

Pictures of the internals of the 819 line GM2891-13.
Nine ECL80 triode-pentodes are employed in this instrument.
Modulator employs an EC80, a high slope UHF triode. Four grid pins so it was designed for grounded grid operation. Wil check this later today.

https://www.radiomuseum.org/tubes/tube_ec80.html

DFWB.
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Old 21st Nov 2020, 11:53 am   #11
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Default Re: Philips GM2891

I note that it uses the mainland Europe intercarrier sound frequency of 5.5MHz (ours was 6MHz.) I have recollections of swapping out ceramic filters in sets brought home by expats only to find the sound didn't work.
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Old 22nd Nov 2020, 12:33 am   #12
Richardgr
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Default Re: Philips GM2891

The interior view is much the same as mine. Those big black capacitors - how reliable are they? I have a similar age Philips amp with loads of those, and am wondering if they should just be replaced.
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Old 22nd Nov 2020, 1:11 am   #13
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Default Re: Philips GM2891

The black ones are paper, and considered replace on sight these days.
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