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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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14th Mar 2017, 5:19 pm | #1 |
Dekatron
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Ultra V1781 super slim TV set.
This Ultra V1781 has been brought in for repair because there is no line or frame hold. 150volt p - p sync pulses are present at the anode of V6A the sync separator valve. The curious thing is that the frame broad pulses seem to be absent which doesn't make sense. The waveform of the negative going video at the grid of V6A is a horrible mess and it is difficult to lock the scope on to the sync pulses.
About the set. Made in 1960 the Ultra V1781 was one of those sets designed to take full advantage of the recently introduced short neck 110 degree CRTs. It's a Mazda CME1705 in this set. Another interesting feature is the FM radio facility which done properly by employing a separate 10.7Mhz IF amplifier, demodulator and AF amplifier. When switched to FM operation the line timebase is switched off and the FM unit is switched in, even the 0.1amp series heater chain of the three FM valves is supplied from the HT line. The motorised turret tuner has three radio positions, H, T and L. The tuner is a huge old fashioned thing and resembles the Brayhead type of tuner that was used as a Band 3 converter. The chassis is a development of the one fitted in the Pilot "Spacemaker" set which is under discussion in this Forum. DFWB. |
14th Mar 2017, 5:26 pm | #2 |
Dekatron
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Re: Ultra V1781 super slim TV set.
I remember doing those as rental recons back in the day.
Lawrence. |
14th Mar 2017, 5:49 pm | #3 |
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Re: Ultra V1781 super slim TV set.
Hi Lawrence,
I remember these sets when they were new. Ultra were the first UK firm to make a 19" "square screen" TV. December 1960? DFWB. |
14th Mar 2017, 6:00 pm | #4 |
Dekatron
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Re: Ultra V1781 super slim TV set.
I don't remember them from new, I started in the trade in 1964, the firm I started with had lots of Ultra sets, I was on the recon section for a while then got shoved up to the paid service (chargeable) section, did lots of recons during my time in the trade, the most soul destroying was doing them when I once worked for Rumbelows, once done we had to put a label on the back saying which depot, the date of recon and the engineer who did the recon, a big wagon would come and collect them, a few weeks later a load of them would be delivered back to our depot again for supposedly for a recon, still with my name on them and fully working, I think it was the various depot managers on some kind of numbers/bonus scam, I couldn't wait to get out of that place.
Lawrence. |
14th Mar 2017, 6:36 pm | #5 |
Dekatron
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Re: Ultra V1781 super slim TV set.
These were almost new when I was first in the trade. They were very popular as was the entire Ultra Bermuda range.
I still have a little aluminium coupling that connected the motor gears to the tuner spindle. A few pages from the sales leaflet for 1960. Regards, John. |
14th Mar 2017, 6:45 pm | #6 |
Dekatron
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Re: Ultra V1781 super slim TV set.
Always liked the look of the Ultra sets from this era. Don't remember fixing them, but helped to install many and the aerial. The Ultra TV's i saw were from a couple of years later than this model.
They were expensive if compared with this Ekco T377 an excellent TV from 1961 at approx £50. Whether P/T was the culprit I forget. http://thevalvepage.com/tv/ekco/ekco_377/ekco_377.htm Frank |
14th Mar 2017, 6:50 pm | #7 |
Dekatron
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Re: Ultra V1781 super slim TV set.
The Ultra "Bermuda" range has a special place in TV history - it was a truly 'modern' set [in that it was solidly designed-for-ITV from the outset rather than having a BIII converter coerced into the signal-path of a BI set which was the case for a lot of similar-era products] and it fitted really well into the stylistic ~zeitgeist~ of the very-early-1960s so it sold well - however Ultra made a loss on every one they shipped and it contributed to the subsequent collapse of the company.
[See "The Setmakers" for more detail] |
14th Mar 2017, 7:24 pm | #8 |
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Re: Ultra V1781 super slim TV set.
The sync problems have turned out to be instability of the vision IF stages. This set needs realignment. I've tweeked up the IFs but I really need the manufactures alignment instructions to do the job properly.
Other problems: Bad frame linearity and the interlace could be better. It might be a good idea to add the interlace filter circuit as used in the 21" models. It is suggested that Ultra boss Teddy Rosen made a bad move when he acquired Pilot Radio from the US owners. DFWB. |
14th Mar 2017, 9:20 pm | #9 |
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Re: Ultra V1781 super slim TV set.
Results of todays work on the set.
Checked the FM radio. No stations coming through and no background hiss. DFWB. |
15th Mar 2017, 7:22 am | #10 |
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Re: Ultra V1781 super slim TV set.
Twiddled chassis! This was a continual problem with the 17-70 series but I don't think I encountered one of these that had been violated.
It drove me crazy! All the Philco chassis from the 'Slender Seventeener' to the Codenta were twiddled and I mean twiddled. Broken cores and rough handling. What did they think they would improve? My trusty signal generator [Advance E2] certainly did it's job back then. I think it was mostly the 'old timers' that carried out this evil task. Often the cure would have been a simple attenuator. John |
16th Mar 2017, 2:22 pm | #11 |
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Re: Ultra V1781 super slim TV set.
Bad frame linearity turned out be the thermistor in series with the scanning coils. See attached circuit diagram. The function of the NTC thermistor is to compensate for the increase of resistance in the scanning coils after warming up.
With regard to the function of the resistors R132 and R133. The resistors are there to induce a degree of picture shift. The resistors are easily accessible and it was found that when the resistors are shorted out the picture will be moved down by 10mm. Because the CRT has a 5:4 aspect ratio it is necessary to overscan the picture width by 10%. The absence of FM radio has been traced to zero volts on the anode of the first 10F18 IF amplifier valve. DFWB. Last edited by FERNSEH; 16th Mar 2017 at 2:30 pm. |
16th Mar 2017, 2:31 pm | #12 |
Banned
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Re: Ultra V1781 super slim TV set.
IF amp 10F18 no anode volts, that will be an O/C IF coil then? Not got a diagram, just a wild guess whilst I have nothing else to do.
Sam. |
16th Mar 2017, 4:02 pm | #13 |
Octode
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Re: Ultra V1781 super slim TV set.
So it does use the same frame circuitry as my Pilot although the rest of the chassis doesn't look very similar. They obviously liked the idea of connecting the HT to the frame coils as this model still uses it. Presumably, the two resistors on their own would not cause any picture shift without the HT connection? I am still puzzled as to why they needed this as I assume there is physical shift provided by adjustable magnets on the scan coils?
Cheers Nick |
16th Mar 2017, 4:56 pm | #14 | |
Dekatron
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Re: Ultra V1781 super slim TV set.
Quote:
Hi Nick. Except for a few minor changes the circuits of all the 1959 to 1962 Ultra TV sets are very similar. The later sets dispense with the reflexed sound IF amplifier. Instead in models like the Pilot PT650 where a 6F23 pentode performs the dual role as an IF amplifier and audio amplifier, in the V1780 series a high slope EF184 pentode is employed as the 38.15Mc/s amplifier only. However, because the later sets including the V1781 do not have the reflex sound IF amplifier valve the FM radio unit employs a 10LD12/UABC80 triode amplifier stage. Earlier sets including the Pilot PT651 have a 10D2/UB91 double-diode FM ratio detector from which the audio is fed to the reflex TV sound amplifier. The very last "real" Ultra TVs had facilities for easy conversion to switchable 405 and 625 operation. Models 200C and V1984. Also 23" models 2380 and 2384. DFWB. DFWB. Last edited by FERNSEH; 16th Mar 2017 at 5:04 pm. |
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17th Mar 2017, 11:31 am | #15 |
Dekatron
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Re: Ultra V1781 super slim TV set.
The FM If transformer was indeed damaged. After repairing it I'm getting results on FM now but more work needs to be done to the FM receiver unit to bring it up to a reasonable standard of reception.
The attachment shows the complex mechanics of the motor tuned tuner. The turret tuner is in fact the old Cyldon type C. DFWB. |
18th Mar 2017, 12:01 pm | #16 |
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Re: Ultra V1781 super slim TV set.
Tweeking up the 10.7Mhz IF transformers has improved the FM radio but the long term reliability cannot be guaranteed until the 10LD12 valve socket has been replaced.
It wasn't an easy job to remove the faulty valveholder. I didn't relish the idea of removing the FM amplifier unit in order that the valveholder rivets could be drilled out. Instead the valveholder was crunched up and the soft aluminum rivet heads were filed off in situ. A new B9A valveholder will be fitted today. DFWB. |
18th Mar 2017, 4:56 pm | #17 |
Dekatron
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Re: Ultra V1781 super slim TV set.
This takes me back 50 years! Oh dear, was it really that long ago?
That Cyldon took some killing off. It was designed correctly in the first place so no point in changing it other than the modifications needed to employ the later excellent Mazda tuner valves. J. |
19th Mar 2017, 12:14 pm | #18 |
Hexode
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Re: Ultra V1781 super slim TV set.
I am inclined to think that the reason for the H.T. being fed in part through the scan coils was to buck vertical disturbances when the set was operated from asynchronus mains supplies as was sometimes found even in the early 60s. The set from memory did have shift rings on the deflection coil assembly.
Victor |
19th Mar 2017, 5:16 pm | #19 |
Dekatron
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Re: Ultra V1781 super slim TV set.
I remember this model, as I was given one in the 1960s by a (secondary) schoolfriend's parents who knew of my interest in electronics. It worked very well and did look rather modern, albeit with the "goldfish bowl" 17" CRT.
The VHF/FM radio performance was very good, due to using a separate 10.7MHz IF amp and FM detector. As has been said, the motorised tuner was a complicated beast and I never had to do any work on it. None of these Bermuda range models used flywheel line sync. I also had a 19" model 1984c, which had provision for fitting a 405/625 conversion kit (I still have a kit, obtained from Manor Supplies). Sadly, for reasons I have forgotten, I scrapped the set. However, I was later given a non-convertible model 1984, which I still have (but have yet to restore). The model 1984c had a printed circuit edge connector type of connector strip, ready to plug in the converter unit, but with a dummy connector fitted, with wire links, to bridge the necessary contacts to maintain correct 405 operation until a kit was fitted. The UHF/625 converter chassis was fitted in the space behind the two loudspeakers to the right of the main chassis, when viewed from the rear. The 625 converter employed three vision IF stages (6F23's, if my memory is correct) and so was quite sensitive, which was necessary given the low gain of valve UHF tuners. I hope to obtain a 1984c at some point, in order to fit the conversion kit. |