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Old 22nd Jun 2024, 6:52 pm   #1
high_vacuum_house
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Default Ultra VR17-52 table television with VHF radio

This is an Ultra VR17-52 combined table television and VHF radio. The unusual feature is an EM81 mounted in a bezel below the CRT. This was one of the main reasons for deciding to get this particular set. It came from this years retrotech event and was acquired for £5 as the event was closing having spent the day on the B&B stall looking rather unloved. There is some interesting switching going on between television and VHF.

The rotary tuner knob has 3 positions for VHF reception (Home Light and Third) There is a cam which extends from the back of the rotary tuner which operates a slide switch. On television channels all of the valve heaters are in operation and the HT for the EM81 is cut off. This magic eye looked in good condition as I expect the set wasn't really used as a radio receiver for long periods of time. In the radio position, 3 of the valve heaters (the timebase ones) and the CRT heater are bypassed and a big wirewound resistor is switched in to drop the gain in heater current back to 0.3A

On removing the back, the set was full of dust with not much evidence of any previous work other than the metal rectifier has been replaced and the mains voltage dropper has been repaired following a burn up. Underside is clean with the usual sprinkling of wax and Hunts capacitors to deal with, Although the main electrolytic has a massive bulge on its rubber plug.... Not one to give it the mains and see what happens!!

The chassis comes out with the CRT once the side knobs and speaker are disconnected. In this case it didn't come out easily as the cabinet has distorted and bowed in from the sides at the rear (think of pincushion distortion but in wood!!) meaning the tuner knob shaft would not clear the side. A bit of careful prying with a couple of wooden paintbrush handles as to not scratch anything soon got the chassis free from the cabinet.

With most of the dust vacuumed out, I had to remove the CRT to gain access to most of the chassis top and valves. The CRT in this is a big beast for 17" as it is a 90 degree tube and weighs a ton as well.

Removal was a bit heart-stopping as it is only held in by the front rim and an odd arrangement of screwed hooks to hold the scan coils tightly on to the CRT cone. This became particularly stressful as the scan coils got stuck on some sticky gunge on the neck part way off after removing all of the clamps with the tube rim balanced on its cradle, then I found one of the scan coil wires was a bit short to allow the coils to clear the base of the tube. Finally I was able to release the CRT from the coils without dropping it and it is now in a safe place after having the sticky gunk removed from the neck. Hopefully refitting it should be easier. I now had to replace about 6 wax capacitors on top the chassis and clean everything on top before the CRT can go back in as I don't really want to go through the process of removal again!!
I replaced half a dozen wax capacitors which were on top of the chassis and would be inaccessible once the tube was in place. The tube and scan coil assembly was fitted back onto the chassis. It is not an easy task as there is an aluminium screening can around the scan coils along with various card washers and a spring clamp that all have to be fitted on the neck at the same time inside this screening can.

I decided to see what would happen if I warmed it up with a few volts before doing anything else. This showed promising results and I gradually wound the variac up and could hear the line whistle faintly. I was surprised as I could draw nearly a 1" spark from the top cap of the EY81 even with the variac not fully up. Turning the workshop light off revealed a squashed and dim raster of sorts off the top of the screen.

There was no sound at all but on radio the EM81 lit up nice and bright as well!!

I then started tackling the capacitors underneath the chassis. Half a dozen wax capacitors were replaced, All very leaky. I ran out of 0.1uF capacitors during the restoration. I should have checked what I had before going to Retrotech!!

With some of the wax capacitors replaced, I have slowly wound it up on the variac again, During this time Radio 3 were playing Dvorak new world symphony which was a nice touch (Whenever I hear it, it reminds me of a chap blowing glass flasks making Emitron tubes and building the mast!!) This was on a late 50's Ekco VHF only valve radio which I restored last year and gives excellent results even with LED lighting ECT.

The main electrolytic which needs replacing didn't explode which was nice and I have a much improved raster. This time I was confident to give it over 200V on the variac and have time to readjust the ion trap magnet, shuffle magnet plate and the height, line and frame hold controls. This has given me a very good near full raster which needs a little more work but is nice and stable.

There is still no sound at all though the output stage appears to work. There is also no change when the contrast control is adjusted. Also no clicks or spots on the screen when the wavechange switch is rotated, so it looks as if the next stage is to have a look through the tuner and common IF amplifier stage.
A few more wax and Hunts capacitors were replaced. There is now sound coming through, the 3 position FM radio section is working quietly and the Heghog test tone comes through clearly on channel 1. On the television side of the tuner, there is only 2 biscuits, channel 1 and 9. The rest are vacant.
After more capacitors were replaced, I had better results and there was some video getting through. I tried on channel 9 and the results were much better although the video was extremely poor. I swapped over the common IF and vision IF 30F5 valves with the sound IF one as the sound seems ok with absolutely no change. I also swapped over the video amplifier and sync separator 30FL1's with no change leading me to believe that the problem is possibly deaf tuner valves, PCC84 and a PCF80. These were replaced but still no change.

Switching to the 3 VHF radio positions showed that the tuner and audio sections were working well, though they were all tuned into rather ghastly radio stations!
I next tried checking and swapping the vision detector crystal diode but this was also innocent! I had a look at the video waveform on an oscilloscope and this looked good and so this ruled out most of the receiver from the common IF amplifier valve all the way to the CRT cathode. The voltages around the CRT base seemed not too far out and the EHT was up at just over 14KV. The picture was still completely washed out.

Asking for some help on the forum suggested that it could be a O/C cathode connection inside the CRT. I decided to run it directly off the mains and give the neck of the CRT increasingly heavier taps from the handle of a tack hammer. There was almost no change whatsoever so I raised the front up about 2" and gave the neck slightly heavier blows.

I was thinking that I was soon going snap the neck off the CRT, when there was a bright flash from the screen. Another hard whack must have made the cathode connection as I instantly had a near perfect test card C appear! The brightness is also massively improved.

I have watched it for around an hour and the picture has improved a bit. The camera doesn't do the picture much justice. There are a few things still to adjust such as the scan coil rotation is a bit off and the main electrolytic could do with replacement plus the refitting of the EM91 and loudspeaker to the cabinet.

When switching off, the raster disappears almost instantly unlike before. This must be down to significantly higher cathode current collapsing the stored EHT charge between the anode and graphite coating.
I carefully removed the CRT mask and plate glass implosion screen from the cabinet and gave them a good clean as they were filthy and had the remains of a sponge sealing strip which had crumbled to dust and got between the two.
This was refitted along with the loudspeaker and magic eye back in its bezel. The chassis was then eased back in and its mounting screws and bottom cover refitted. The knobs and tuning knob escutcheon were cleaned and refitted. I was then able to finish off setting up the television picture by realigning the scan coils as the picture was a bit skewy, focus as well as height and linearity. This gave a really good 405 line picture.
The cabinet is a bit scratched. Some cleaning and polish helped a bit. Maybe when I get some more time, I will try and refinish the cabinet to make it look a bit more presentable but at least the television works.
The camera doesn’t do much justice to the picture. The horrible looking lines below the test card circle is actually a reflection of my T shirt!! Maybe I should have turned the light off!!

Christopher Capener
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Old 22nd Jun 2024, 7:35 pm   #2
Reelman
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Default Re: Ultra VR17-52 table television with VHF radio

Great job Chris, you have a good picture there.
Nice to know that a “Brummy Screwdriver” can still work its magic and fix things.

Peter
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Old 22nd Jun 2024, 8:24 pm   #3
thermionic
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Default Re: Ultra VR17-52 table television with VHF radio

Great result Christopher!

You’ve been exceptionally patient with this set, but this has paid off. Fingers crossed the CRT holds up!


All the best.


Simon./
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Old 24th Jun 2024, 8:13 pm   #4
newlite4
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Default Re: Ultra VR17-52 table television with VHF radio

Nice one Chris, I bet you were sweating a bit when you were tapping the tube neck, I wouldn't have gone near it at that point! Quite a decent set with the added attraction of FM radio.
Well Done,
Neil
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