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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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27th Aug 2014, 4:45 pm | #1 |
Dekatron
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Dynatron TV32
Just received today a big bumper bundle of Dynatron service manuals.
All useful of course because they can be used for many Ekco and Pye TVs. There is one set that is particularly interesting, a model TV32. I've never seen like of this one. The circuit diagram is dated 2-10-57 so it's possible the set was made at the time of the takeover of the company by Ekco. It's a beautifully over-engineered receiver, everything is properly done. The set has an isolated power supply using a mains transformer, also full wave HT rectification employing two PY82s. The two HT rectifiers, the PL36 line output, PY81 boost diode, the tuner valves and the CRT are in a series heater chain. All the rest of the valves including the ECL82 frame output are parallel supply 6.3 volt types. Some of the design elements are pure Ekco, for example the flywheel sync system and the frame timebase. The sound has two ECL82 valves in a push-pull arrangement. Other parts of the set are definitely not Ekco, the three stage vision and sound IF amplifiers foe example. I guess that the other unEkco thing about the set is all the valves are Mullard, so is the AW53-80 CRT. It's possible that the set is a fusion of Dynatron and Ekco design work. DFWB. Last edited by FERNSEH; 27th Aug 2014 at 4:53 pm. |
28th Aug 2014, 12:28 pm | #2 |
Dekatron
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Re: Dynatron TV32
The power supply and sound circuits of the Dynatron TV32. I'd reckon this set is the ultimate 405 line receiver.
DFWB. |
28th Aug 2014, 12:49 pm | #3 |
Dekatron
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Re: Dynatron TV32
Would 1957 be one of the first uses of the PL36?
Lovely circuit, I wonder what the price tag would have been and the purchase tax must have as been as much as some TV's. Frank |
28th Aug 2014, 1:13 pm | #5 |
Dekatron
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Re: Dynatron TV32
I believe the PL36 was introduced in 1954 to provide the extra scanning power for the forthcoming 90 degree CRTs.
From the Radiomuseum: http://www.radiomuseum.org/tubes/tube_pl36.html It's likely the developer was Philips. There was some discussion some time ago about the valve. Mullard tell us that it is a pentode, that is a valve with a suppressor grid but when one was dissected we discovered that it is in fact a beam tetrode. https://www.vintage-radio.net/forum/...6+beam+tetrode Hi Frank. I can't speculate what the price of such a set was. Three figures is likely? According to the circuit diagram the TV32G had also a record player. It begs the question how many TV32s did Dynatron make? DFWB. |
28th Aug 2014, 1:29 pm | #6 |
Dekatron
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Re: Dynatron TV32
The line timebase circuit: The flywheel sync discriminator and oscillator is pure Ekco but the output stage isn't.
Note the switch to select flywheel or direct sync. You don't see that often. DFWB. |
28th Aug 2014, 2:14 pm | #7 |
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Re: Dynatron TV32
Hi David, hope I have your name correct.
I have just had a look on the Yahoo Hacker group and there is a photo of the TV32and TV32G with prices from a 1958 leaflet. TV32 175gns TV32G 190gns On the front of the leaflet are "New prices to reflect the new tax" they are reduced by about 9gns. They are also available with a suffix M, a few gns more expensive, cannot see what the M is for unless it is Mahogany, there is a photo of both models. Frank |
28th Aug 2014, 5:55 pm | #8 |
Pentode
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Re: Dynatron TV32
Thank you for the circuits David, the audio amp circuit will make a nice little unit using a 6SN7 type DT & a couple of 6V6s, most useful!
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28th Aug 2014, 6:28 pm | #9 |
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Re: Dynatron TV32
It's one of the best push-pull audio amplifiers I've ever seen in a TV receiver.
Ferguson once used ECL80s in some of their hi-spec sets. A much later Dynatron TV which employed the Group 67 chassis also used a pair of ECL80s. Nothing wrong with that except there is that problem with the the ECL80 having a common cathode pin for the triode and pentode sections. DFWB. |
28th Aug 2014, 7:34 pm | #10 |
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Re: Dynatron TV32
Hi Robin,
That's a lot more than I thought those cars were. The TV32G: The set with gram was 190 guineas so the actual price was 199 pounds 10 shillings. Dynatron couldn't have sold many. DFWB. |
28th Aug 2014, 8:14 pm | #11 | |
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Re: Dynatron TV32
Quote:
No wonder they are a rare set, if indeed any still exist? Mark |
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29th Aug 2014, 9:56 pm | #12 |
Nonode
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Re: Dynatron TV32
One entirely car related post deleted. Please keep to the television discussion!
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4th Sep 2014, 9:54 pm | #13 |
Nonode
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Re: Dynatron TV32
I’d guess that given its apparent high overall performance level the Dynatron TV32 would also have had gated black level agc and black level restoration. Odd though is the mix of “E” and “P’ valves; why not all “E”?
Cheers, |
5th Sep 2014, 12:12 am | #14 |
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Re: Dynatron TV32
Further examination of the circuit diagram reveals that the set does have a gated vision AGC system, and the circuit is again pure Ekco and is similar to many other other sets made by that company.
It's very simple gated AGC system consisting of one EB91 double-diode. One diode section serves as the back porch sampler and the other is the AGC supply rectiifer. There is another circuit feature which again is Ekco, the white spot inverter. The CRT heater is in the series chain along with the timebase valves which is logical because those valves are switched off when the set is tuned to VHF-FM. There is no black level clamps or video DC restorer circuits in this set. The CRT cathode receives negative going video from a cathode follower via parallel resistor-capacitor coupling. Sometimes called an aircraft anti flutter circuit. It can also function as a simple beam current limiter. The IF amplifiers are not of Ekco design. The three stage vision amplifier has more rejector traps than is customary in a 405 line receiver. There's four! The sound IF amplifier operates at the then industry standard 38.15Mc/s, including the FM radio. So to sum up, it seems the Dynatron designers did the RF/IF circuits and the Ekco team did the timebases. DFWB. |
13th Sep 2014, 1:36 am | #15 |
Nonode
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Re: Dynatron TV32
Thanks for the additional information. I wonder if the more elaborate vision IF strip was an effort to get the video bandwidth out to or close to 3 MHz, as might have been seen as appropriate for a “luxury” class TV receiver. With a wider “native” bandwidth, better trapping could have been required to obtain the required sound carrier and adjacent channel nulls. And maybe a mild trap was used to set the Nyquist slope rather than relying on the natural bandpass curve.
An interesting perspective on the setmaker view when it came to video bandwidth is provided in the attached items from Wireless World 1952. The use of the 38.15 MHz IF for both TV sound and FM was I think early TV-FM receiver practice, but abandoned because of the difficulty – although not impossibility - of obtaining adequate FM selectivity. One suspects though that Dynatron would have designed for adequate FM selectivity. I guess that one potential advantage of the same IF for both TV sound and FM, at least if the AM and FM demodulators were separate and could operate simultaneously, is that the DC output from the FM demodulator could be used to provide AFC for both TV and FM. According to the Wireless World 1960 excerpt attached, later on Dynatron did adopt the dual-frequency, 38.15/10.7 MHz IF for TV-FM combinations, although by then it might not have been designing its own IF strips. Interestingly it included a separate 38.15 MHz discriminator for TV AFC. Cheers, |
13th Sep 2014, 11:07 am | #16 |
Dekatron
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Re: Dynatron TV32
I recently bought a book by Steve Kosareff title " Window to the future", bargain basement 99p, it's a fascinating book about the adverts TV makers in the USA used to sell their TV's in the 1950's/60's.
One advert for Westinghouse TV's was " New Westinghouse BROAD BAND TV gives 22% MORE DETAIL" It then goes on to explain how the it works, well sort of, this was 1957. Seems like others were narrowing the IF passband to keep the gain up and valve count down. I cannot post a photo of the page, the book is quite new and probably still in print. Frank |
13th Sep 2014, 12:14 pm | #17 |
Dekatron
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Re: Dynatron TV32
The Dynatron TV model TV50 featured "Autotune". A system employing a motorised turret tuner. TV and FM channels can be selected by a row of push-buttons on the set's front panel or by a cable remote control.
This Ekco designed set does it properly in having the standard 38.15Mhz TV sound IF and 10.7Mhz for the FM radio. An interesting refinement is the automatic frequency control of the tuner which is active on both TV and FM. On TV a 6D2/EB91 double-diode (V7) acts as the AFC discriminator and on FM the control voltage is derived from the FM ratio detector. The AFC control vari-cap diode is CD1 and is a type XD901. The set has the Ekco vision AGC system employing true back sync porch black level sensing. Unfortunately the rest of the set is nothing special in having simple direct line sync instead of flywheel sync. The timebases are similar to the Ekco T344. DFWB. |
13th Sep 2014, 12:29 pm | #18 |
Dekatron
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Re: Dynatron TV32
A follow up to my last post. The text in the third attachment posted by Syncrodyne on #15 could well apply to the Dynatron TV50.
It would seem evident that a considerable amount of design to TV receivers was still going on at the Dynatron works at Maidenhead. It is well known that in 1960 Dynatron made an ultrasonic remote control system for certain TV sets. The RC1 system permited control of volume up and down as well as channel stepping. The remote handset was transistorised, or so I'm led to believe. DFWB. |
13th Sep 2014, 1:06 pm | #19 |
Dekatron
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Re: Dynatron TV32
The circuit diagram of the three stage vision IF amplifier of the Dynatron TV32.
DFWB. |
13th Sep 2014, 5:35 pm | #20 |
Octode
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Re: Dynatron TV32
Hi David.
The AFC system on the motorised tuner of the TV50 works amazingly well - almost unbelievably well. The huge amount of swing on the AFC line seems to be able to drag the set on to perfect tune from one end of the channel to the other with no fuss at all. And, as you say, the Ekco designed chassis is brilliant and does provide a first-class picture. Alas I do not have the remote control for this set. Kind regards. From Mike.
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