electronics Australia 1963 make an oscilloscope

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electronics Australia 1963 make an oscilloscope

Postby Harry Dalek » Mon Mar 21, 2011 9:34 pm

Hi Been looking at some old magazines here's a nice one on a scope project
from 1963.
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TV.jpg
First page
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TV 001.jpg
The schematic
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TV 002.jpg
Insides look
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TV 003.jpg
insides look part 2
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TV 004.jpg
last page
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Postby AncientBrit » Tue Mar 22, 2011 6:39 pm

Not a bad circuit.

3 inch tube, Y is direct coupled too.

Regards,

Graham
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Postby Harry Dalek » Tue Mar 22, 2011 9:24 pm

Hi Graham

i have been looking at my magazine collection any thing of interest i am going to scan ...I just found a very simple scope project from 1950 i will post this soon as i scan it.
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Postby Steve Anderson » Tue Mar 22, 2011 10:32 pm

Graham,

It is an unusual arrangement in the vertical channel, I've not seen it done quite like that for a scope before. My only point of concern is does it 'run out of steam', is there enough voltage on the triodes that feed the plates? Those cathode-follower triodes are hung effectively between the +270V HT feed and the +150V feed for the preceding 6BL8s (ECF80s). Just 120V.

However the CRT is being run at its very lowest voltage, approximately -200V on the cathode (via the Focus & Brightness pots) and around +200V on the final anode (pin 8 ) which should be the same as the average voltage of the deflection plates. From the triodes mentioned above this will be roughly half-way between +270 and +150V, around +210V, a total of approx. 410V.

The datasheet limits are 400V min., 800V max. for the DG7-32 or DG7-32/01. From experience with this CRT (it's the same type going into the current monitor and I've used these CRTs before) at less than 500V they are quite dim for a scope really, and useless for displaying a raster. At least 600V is needed and this current version will be somewhere around 700-730V which also reduces the spot size.

Returning to the EA article, I guess it performed as advertised, I just wonder why they used such a low voltage? The transformer is only 110V, rather odd.

Harry, if there's any more like that I would like a copy, but don't go out of your way to scan them.

As for a re-born "Brute", yes there is a vague plan to do that, a lot smaller (within the confines allowed by a 5" electrostatic CRT), I'm thinking of calling it "The Amazon".

One of the reasons the "Brute" was abandoned was simply the daft amount of hardware logic that was going into it. With a micro it's so simple. But a year ago I hadn't programmed anything since the early 80s which were MC6809s.

Long story short time...with Grahams advice I've picked up the baton (the pun wasn't intentional) and I have conceptually distilled all those 16-pin chips into a single 28-pin one, perhaps even smaller. But as I said, it's some way off in the future.

Steve A.
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Postby Harry Dalek » Tue Mar 22, 2011 10:45 pm

No worries Steve
I love seeing them as well once i put the mag away i forget i had them ,,,this time i scanning them and sharing i hope every one finds them interesting ...i have a few on part tv projects but missing the other mags sort of a tease these ones ! i don't know if others have Slow scan tv circuits you know p7 type projects i love those i find those more interesting than doing it all on computer ...theres no pride in letting these things do all the work .
But what i am getting at please any one reading this that has something of interest get it out and share .
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Postby Steve Anderson » Tue Mar 22, 2011 11:42 pm

It was an item in Electronics Australia that first got me interested in SSTV, sometime in the early 70s. All P7 stuff, the only memories most people used were those between their ears, the largest section of mine is a WOM, (Write-Only-Memory).

A semiconductor version from Signetics (remember them) is attached.

One of the objective was/is that with a tube (CRT) swap the display could change from a NBTV version (P1 phosphor) to a SSTV version (P7 phosphor). I chose the 5ADP1 as I also have the P7 version (5ADP7) and it has a truly flat faceplate.

I agree, with SSTV do it the old way, a la Copthorne McDonald. 102/128 lines, around 7-8 seconds per frame, no colour. That's it!

I do agree though that SSTV (Slow-Scan TeleVision) is a misnomer as it is really a series of stills, not television as we conventionally think of it, yet it's not quite FAX either.

Steve A.
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Postby gary » Wed Mar 23, 2011 9:54 am

Steve Anderson wrote:It was an item in Electronics Australia that first got me interested in SSTV, sometime in the early 70s.


The one in May 1974? I bought that when it came out and have it here now in front of me and I keep it because I still dream of building it 37 years later, dream on...
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Postby Steve Anderson » Wed Mar 23, 2011 12:14 pm

gary wrote:....The one in May 1974?...


Gary, I'm not really sure when, I would have thought it were earlier as in '74 I was at RMIT in Melbourne. As I recall I was still at Technical School when the item I'm thinking of came out...but memories such as mine are not infallible.

If you feel so inclined and have the facilities to do so, I would love to see a scan of it whether it's the item I'm thinking of or not.

There is one item I have been trying to get hold of for decades, ever since it was printed. It appeared in Wireless World in the summer of 1969 (Northern Hemisphere that is), maybe June or July.

It was an item whereby the author had updated a scope to have enough bandwidth to work with colour TVs. The scope used a 5CP1 CRT and he extended the bandwidth to 5MHz...yes, 5MHz.

It was, like the EA SSTV item, the thing that first got me interested in scopes, CRTs and the like. I read and re-read it so many times. I would know instantly the moment I saw a copy of it. I live in hope.

Steve A.
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Postby gary » Wed Mar 23, 2011 1:08 pm

Yeah, the article does say it is a "new design" implying there was a predecessor, none-the-less I submit the first 2 pages, if it is of interest to anyone I can scan and post the rest of the article.

(can't help with the WW edition I'm afraid).

Image
Image
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sstvmonitor1.jpg
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sstvmonitor2.jpg
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the rest.zip
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Last edited by gary on Wed Mar 23, 2011 2:19 pm, edited 1 time in total.
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Postby Steve Anderson » Wed Mar 23, 2011 1:32 pm

Gary, thanks for that. The EA article I'm thinking of 'possibly' isn't this one, but this is a good find for me. If you could add whatever follows on I would be grateful.

I don't expect many will have that WW article, but if you don't ask, you don't get.

Thanks again,

Steve A.

Interesting to note that a long persistence version of the common DG7-32 is used, the DP7-32, a rare beast today. As I mentioned elsewhere, here the CRT has more typical voltages applied to it, close on 800V total.
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Postby gary » Wed Mar 23, 2011 2:20 pm

Ok, added to the original post. Cheers.
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Postby Steve Anderson » Wed Mar 23, 2011 2:40 pm

Gary, thanks, excellent!

Steve A.

A bit later...Unless my peanut brain has failed me I think there's an error in the +/-15V voltage doubling power supply. One of the 1000uF/16V caps is in the wrong place, the most right-hand one. Am I correct?
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Postby Harry Dalek » Wed Mar 23, 2011 4:37 pm

Steve Anderson wrote:It was an item in Electronics Australia that first got me interested in SSTV, sometime in the early 70s. All P7 stuff, the only memories most people used were those between their ears, the largest section of mine is a WOM, (Write-Only-Memory).

A semiconductor version from Signetics (remember them) is attached.

One of the objective was/is that with a tube (CRT) swap the display could change from a NBTV version (P1 phosphor) to a SSTV version (P7 phosphor). I chose the 5ADP1 as I also have the P7 version (5ADP7) and it has a truly flat faceplate.

I agree, with SSTV do it the old way, a la Copthorne McDonald. 102/128 lines, around 7-8 seconds per frame, no colour. That's it!

I do agree though that SSTV (Slow-Scan TeleVision) is a misnomer as it is really a series of stills, not television as we conventionally think of it, yet it's not quite FAX either.

Steve A.


Hi steve

First up Gary Thanks so much for posting the SSTV scans.
i am very interested in those
i love sstv but really only the old way as you say B/w or green and white as mine was and 7 sec p7 display ...it was the first tv i ever made and the frill of see it it work for the first time i will never forget .

If i could go back i would stop my self from scrapping that one ...wish i still had the tube i only have the 88mH inductors i know i used init for the filter and the 741 ics .

Thinking of trying it on the new old scope as it has a rather slow phosphor. not p7 but might see some of the photos as it scans down .

Using a monitor for nbtv and slow scan thats new to me sounds like a good idea !

Yes its a pity computers killed the p7 crt I still like it and i think its the only way to do it or your cheating.

I found some more goodies to scan i will post soon.
Last edited by Harry Dalek on Wed Mar 23, 2011 11:21 pm, edited 1 time in total.
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Postby Steve Anderson » Wed Mar 23, 2011 5:16 pm

Harry, I look forward to whatever you can put up here if it relates to still pictures (SSTV) or moving pictures (NBTV). the origin being mechanical, electronic, or more often than not, a blend of both.

To that end some time ago I pondered on mechanical SSTV...I've not seen a reference to this as yet.

In June 2006 I started to rough-out an item potentially for the newsletter, but with everything else going on it hasn't gone any further. Re-reading what I wrote at that time it's the reverse of what is apparent in NBTV. That is the camera is much easier than the monitor/display. I wonder if a mechanical SSTV display could be done at all? Think of NBTV, then slow it down by a factor of anything from 50 to 100. Ideas welcome, but no prizes!

Some form of printing is an obvious solution, but that's permanent, not transient like a disc, drum or even a P7 CRT. No electronic memories, Silicon, magnetic-core or tape. Slugged or latching relays...OK....did someone say Uni-selectors?

Steve A.
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Postby gary » Wed Mar 23, 2011 5:29 pm

A matrix of lamps (leds) with mechanical commutation - i.e. Bairds cinema solution - count as mechanical? Perhaps capacitors across each led to hold charge until next refresh. A bit too expensive for me to have a go at I think.
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