4th Jul 2010, 6:20 pm | #21 |
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Re: VCR97 Project
Hi Trev
I have half-built a Simplex TV receiver from Practical Television March '54. I have scanned the relevant articles and can e-mail a file to you. It uses a multiplier from the HT winding of the mains xfmr, 6SN7s, EF50s and SP61s. Are you interested in the info for reference? Cheers Brian |
4th Jul 2010, 6:37 pm | #22 |
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Re: VCR97 Project
Hi Brian
I have indeed the diagram for the Simplex and as far as I can see is a very nice design. I am going to loosly base the set on the Simplex but I see there can be improvements with modern components and some alteration to the circuitary. How far are you on with the project Brian, have you had any results? Bob, your set looks really professional, I doubt I can replicate the quality of yours, I would never have the time to do it that way, I am trying to build a set that is of entertainment value within a reasonable time, although I dont want to make a cod of it.
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4th Jul 2010, 6:43 pm | #23 |
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Re: VCR97 Project
Hi Trevor,
The Cossor model 54 employs an electrostatic CRT type 3444 which was made by the same firm. Some sets have been fitted with the VCR97 as a service replacement. In this receiver the y plates are employed for the horizontal scanning. A single Cossor MS/PEN is used as the line blocking oscillator and output. Somehow the set designer has got away with driving the y plates without a push-pull sawtooth waveform. One y plate is supplied with the 750V p-p sawtooth waveform which comes from the MS/pen anode.. The other y plate is DC balanced with the other. The frame time supplies both x plates. The EHT voltage is 4000V. Considerably higher than that required by the VCR97. These simple timebases could be considered for a VCR97 TV construction project. Many post-war and perhaps some pre-war American 7" CRT TV receivers employed the 6SN7GT and 6SL7GT twin triodes to drive the deflector plates. The SP61 RF pentode is up to the job, check out the Argus circuits. I don't know if the EF50 is any good for timebase work. DFWB. |
4th Jul 2010, 6:44 pm | #24 | |
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Re: VCR97 Project
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4th Jul 2010, 7:09 pm | #25 |
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Re: VCR97 Project
Here's another electostatic CRT TV construction project. It appeared in the November 1952 PTV magazine. It uses a 3" 3BP1 CRT but it should be possible to adapt it for the VCR97. The timebase valves are EF91s. The RF stage uses two EF95/6AK5 pentodes in a cascode arrangement.
The sound receiver employs an ECC91/6J6 in a super regenerative circuit. An EF91/6AM6 is the sound output valve. DFWB. |
4th Jul 2010, 8:27 pm | #26 |
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Re: VCR97 Project
Hi Trevor. Your thread tweaked my recollection of a cutting I have which shows the owner of a "self build" set standing alongside it, a "VCR97" I thought. Just looked him up and google took me to your mention of him at the start of your thread. Mr Urban was featured in the Guardian "Collectors and Their Hobbies" series on August 14th 1989 with his set titled "The First VDU" an "experimental video unit made in 1948 from former RAF radar compnents". He's coy about the insurance value of his exhibition in 89 but estimates £4k saying that he would be tempted take lump sum for the lot and go touring Europe. You may know if he ever managed that.
I can do you a photocopy if required. Cheers, Dave PS. I notice that his comment [then] about "the need for today's young to know where their personal stereos, ghetto blasters and CD's come from" chimes very well with the recent "We are not alone" thread started by Jeffrey [and the Astronomer Royal]. Last edited by dave walsh; 4th Jul 2010 at 8:35 pm. Reason: more |
4th Jul 2010, 9:31 pm | #27 | |
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Re: VCR97 Project
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4th Jul 2010, 9:41 pm | #28 |
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Re: VCR97 Project
Hi Dave.
Indeed Joe is a legend up here, Myself and Bob Baird spent over £2000 buying a huge quanity of spares and assorted vintage stuff in 2004. He is very much a poor soul now he is in his 80's and has not been well with a stint in hospital and is not was he was even a few years ago. He did get his European trip but he's just not fit enough now to do any more travelling in his camper van. He still has the set he made and as an old man believes its worth a fortune, so many have made these sets but I for one would never want to upset him, he won't be here forever.
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4th Jul 2010, 11:40 pm | #29 | |
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Re: VCR97 Project
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I saw the "Personal" details Dave, and it was a toss-up between that and the Simplex. The Simplex won because I found a VCR97! |
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8th Jul 2010, 10:55 pm | #30 |
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Re: VCR97 Project
Hi i have also played with the simplex curcuit but i cheated with the rf section i used EF85s for the time beses and ECC83 for the push pull on the line scan and another for the sync seperator . The EHT is about 1500 so its a drawn curtains to view. Danny
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9th Jul 2010, 1:12 pm | #31 |
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Re: VCR97 Project
Hi Danny
I cheated with the RF stages when I built my first VCR97 TV back in the late 1950s. I took our first TV, an Ekco TC162, apart and used the RF chassis. This time, I decided to build the whole lot but I built the RF section on copper-clad laminate as it was easy to make screens etc. Bob, your TV looks fantastic. The care you have taken deserves a big round of applause. As an aside, I have not seen a rubber mask for the 6" tubes for years - anyone got a spare? Last edited by brianc; 9th Jul 2010 at 1:28 pm. Reason: typo |
9th Jul 2010, 10:31 pm | #32 |
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Re: VCR97 Project
Hi Danny, that looks a really good job. I have had a busy week at work, the other engineer is on holiday and I have been at Glasgow, Edinburgh, Dundee and all places between so I have been too tired to spend any time on it this week.
I am going to crack on with it though over the weekend so long as I don't get too many interuptions, so watch this space.
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9th Jul 2010, 11:32 pm | #33 |
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Re: VCR97 Project
Hi brian i have a mask for my set but it has gone at the back i have grafted it to a dammaged indicator mask i shall eventually take a mould off it and recast it in silicone rubber. I have managed to do a 9" mask for my phillips set so this should be easyer to remould. the only down side is the cost of the materials. but this will be discussed later in another thread. I am planning to build another set using a clear crt from a cossor scope this gives a blueish picture. Danny
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10th Jul 2010, 5:28 pm | #34 |
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Re: VCR97 Project
Hi.
As it's been chucking it down with rain today, I have done some work on the project. Now I have seen all the cracking jobs some of you guys have done, in this case although I want to do a reasonably neat job I also want to use materials to hand and stuff out of the junk box! I am using modern parts but sticking to the old circuitary. I am using hot melt to fix wires and cable ties where necessary but in a neat way. If the set was to be built now and used for entertainment it would be made in a reasonable time, who would want to wait two or three years to watch the telly. I have started on the power supply doing the mains side, CRT heaters and I have made a start on the EHT supply, I may though have made an error I fitted 2 IN5408's for the doubler but I thought they were 1500v piv but they are only 1000v so these may have to come out.
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10th Jul 2010, 6:25 pm | #35 | |
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Re: VCR97 Project
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I have the tube, any chance of the construction info? Cheers Sean
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10th Jul 2010, 9:22 pm | #36 |
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Re: VCR97 Project
Hi Sean
I have a scan of the article. I can email it to you if you want it but I need your email address (I think). Cheers Brian |
10th Jul 2010, 9:30 pm | #37 |
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Re: VCR97 Project
ooh can i be cheeky and ask for a copy too, i have a 3B1P i would like to have a play with.
Jay
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10th Jul 2010, 10:15 pm | #38 |
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Re: VCR97 Project
No problem Jay.
I think I need your email address or can I attach files to a PM? |
10th Jul 2010, 10:16 pm | #39 |
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Re: VCR97 Project
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11th Jul 2010, 1:07 am | #40 |
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Re: VCR97 Project
I have now completed the potential divider chain for the the EHT and completed the doubler, this has allowed me to test the CRT and focus.
The scanning plates are not connected yet, here are the results with the spot purposely out of focus for the camera.
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