Anyone recognise this homebrew 'scope? - UK Vintage Radio Repair and Restoration Discussion Forum

Rubberfingers · 18th Nov 2016, 11:06 am

Does anyone recognise this oscilloscope, (assuming it was built to a published design) that I bought from the Merley Hamfest for £1 back in August?. It is single channel using a DG7-32 CRT, and has an HF HT inverter, built on what looks like a line output transformer core.

MrBungle · 18th Nov 2016, 11:18 am

Interesting item. I'd love to reverse engineer that.

What transistors does it have in it (I can't see from the photos)? They're usually easy enough to text search for in any articles. Could be a custom design looking at the breadboarding.

Rubberfingers · 18th Nov 2016, 11:34 am

The inverter uses an oc35 and an oc29, I suspect that the oc29 is a substitute,and that the design oiginally used 2 oc35's. The TO39 transistors in the signals side are BSW68's which are 150v devices and probably drive the deflection plates. Not all of the transistors a retain their markings due to corrosion. I suspect I will end up reverse engineering it, although I only originally bought it for the crt!.

MrBungle · 18th Nov 2016, 11:43 am

Royer converter from DC. Certainly doesn't look like mains in.

Had a quick scan through all my articles on homebrew scopes and I can't find any reference to these in any design. BSW68's might be subsitutes as well; fT is a bit low at 30MHz for this task.

If you do reverse engineer it, or bring it to life I'm interested to see any results.

Radio Wrangler · 18th Nov 2016, 12:40 pm

The choice of tube and inverter eht make me think of practical electronics and 1970-ish

David

Rubberfingers · 19th Nov 2016, 2:15 pm

Quote:

Originally Posted by MrBungle

If you do reverse engineer it, or bring it to life I'm interested to see any results.

Well I powered it up, guesstimating 12vdc input, as there is a diode in series with one of the input leads and a 25v electrolytic to ground after this. It runs, the Y gain falls off as I wind the input signal up over 50Khz, so it was probably intended for audio. The Royer converter supplies all of the supplies, including the CRT heater, and makes a painful 1-2KHz whistle. The triggering is very poor to non existant.! One electrolytic in particular looks to have popped its seal, which might explain the slight ripple on the display. The flyback is visible.

Cobaltblue · 19th Nov 2016, 2:56 pm

Its possible that it's based on the Transistorised oscilloscope from Practical Wireless Feb 1972 March 1972.

http://www.americanradiohistory.com/...PW-1972-02.pdf

there are several similarities.

Cheers

Mike T

19th Nov 2016, 2:58 pm

Quite an amazing performance considering the low number of parts, as good as a bought one in the 30's. I love it! Someone spent ages making it, well worth a scrub up and keeping. A bit of Letraset or Dymo tape marking the knobs would be 'period' and make it more useable. Dymo, proper home build of the 60's, Letraset for your posh builder.

MrBungle · 19th Nov 2016, 5:48 pm

Indeed. I wouldn't eviscerate it for parts. Nursing it back to life and cleaning it up would be great.

Quote:

Originally Posted by Rubberfingers

Well I powered it up, guesstimating 12vdc input, as there is a diode in series with one of the input leads and a 25v electrolytic to ground after this. It runs, the Y gain falls off as I wind the input signal up over 50Khz, so it was probably intended for audio. The Royer converter supplies all of the supplies, including the CRT heater, and makes a painful 1-2KHz whistle. The triggering is very poor to non existant.! One electrolytic in particular looks to have popped its seal, which might explain the slight ripple on the display. The flyback is visible.

Excellent! Great news considering the state of it!

MrBungle · 19th Nov 2016, 6:19 pm

Quote:

Originally Posted by Cobaltblue

Its possible that it's based on the Transistorised oscilloscope from Practical Wireless Feb 1972 March 1972.

I think you nailed it. That's a homebrew scope design I haven't got archived yet. Thanks for the pointer as well.

Rubberfingers · 22nd Nov 2016, 7:31 pm

Thanks for the responses, its not quite the same as the Practical Wireless 1972 design, as this uses a multivibrator to generate the HT, whereas "my" oscilloscope uses a Royer oscillator which generates multiple supply lines including the CRT heater. Thinking about it, the power supply in my oscilloscope is possibly a bit too complex for a magazine constructional article, unless the transformer could have been bought, as it has multiple windings. Having now seen a trace on it I will retain it intact, and when I get around to it, have a look at the signals side and see whether I can sort the triggering out.

dseymo1 · 22nd Nov 2016, 7:59 pm

I do like the spirit of that design - no specially-selected or unusual components required.

18th Nov 2016, 11:06 am	#1
Rubberfingers Pentode Join Date: Oct 2012 Location: Dorset, UK. Posts: 240	Anyone recognise this homebrew 'scope? Does anyone recognise this oscilloscope, (assuming it was built to a published design) that I bought from the Merley Hamfest for £1 back in August?. It is single channel using a DG7-32 CRT, and has an HF HT inverter, built on what looks like a line output transformer core. Attached Thumbnails

18th Nov 2016, 11:18 am	#2
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Anyone recognise this homebrew 'scope? Interesting item. I'd love to reverse engineer that. What transistors does it have in it (I can't see from the photos)? They're usually easy enough to text search for in any articles. Could be a custom design looking at the breadboarding.

18th Nov 2016, 11:34 am	#3
Rubberfingers Pentode Join Date: Oct 2012 Location: Dorset, UK. Posts: 240	Re: Anyone recognise this homebrew 'scope? The inverter uses an oc35 and an oc29, I suspect that the oc29 is a substitute,and that the design oiginally used 2 oc35's. The TO39 transistors in the signals side are BSW68's which are 150v devices and probably drive the deflection plates. Not all of the transistors a retain their markings due to corrosion. I suspect I will end up reverse engineering it, although I only originally bought it for the crt!.

18th Nov 2016, 11:43 am	#4
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Anyone recognise this homebrew 'scope? Royer converter from DC. Certainly doesn't look like mains in. Had a quick scan through all my articles on homebrew scopes and I can't find any reference to these in any design. BSW68's might be subsitutes as well; fT is a bit low at 30MHz for this task. If you do reverse engineer it, or bring it to life I'm interested to see any results.

18th Nov 2016, 12:40 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Anyone recognise this homebrew 'scope? The choice of tube and inverter eht make me think of practical electronics and 1970-ish David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

19th Nov 2016, 2:56 pm	#7
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,878	Re: Anyone recognise this homebrew 'scope? Its possible that it's based on the Transistorised oscilloscope from Practical Wireless Feb 1972 March 1972. http://www.americanradiohistory.com/...PW-1972-02.pdf there are several similarities. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

19th Nov 2016, 2:58 pm	#8
Guest Guest Posts: n/a	Re: Anyone recognise this homebrew 'scope? Quite an amazing performance considering the low number of parts, as good as a bought one in the 30's. I love it! Someone spent ages making it, well worth a scrub up and keeping. A bit of Letraset or Dymo tape marking the knobs would be 'period' and make it more useable. Dymo, proper home build of the 60's, Letraset for your posh builder.

22nd Nov 2016, 7:31 pm	#11
Rubberfingers Pentode Join Date: Oct 2012 Location: Dorset, UK. Posts: 240	Re: Anyone recognise this homebrew 'scope? Thanks for the responses, its not quite the same as the Practical Wireless 1972 design, as this uses a multivibrator to generate the HT, whereas "my" oscilloscope uses a Royer oscillator which generates multiple supply lines including the CRT heater. Thinking about it, the power supply in my oscilloscope is possibly a bit too complex for a magazine constructional article, unless the transformer could have been bought, as it has multiple windings. Having now seen a trace on it I will retain it intact, and when I get around to it, have a look at the signals side and see whether I can sort the triggering out.

22nd Nov 2016, 7:59 pm	#12
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Anyone recognise this homebrew 'scope? I do like the spirit of that design - no specially-selected or unusual components required.