Early Air Ministry oscilloscope type 11.

[M0FYA Andy]

Back then there is every chance it was soldered using a copper soldering iron heated in a gas flame, so soldering with finesse wasn't easy!

Andy

[David Simpson]

Yes Andy, it might well have been the old copper bitted soldering iron they used. If they were daubing the joint with Bakers Flux, then the joints were probably leaded as opposed to soldered ( good old 60/40 flux-cored solder).
I have a set of those old copper irons & tried the old -fashioned way. Keeping the bit clean & un-pitted, & maintaining a cherry coloured hotness with the gas torch, results in a jolly slow procedure. There is a school of thought which reckons that the multi-wrapping of wiring on tags was to maintain mechanical security of the joint, should good old Pb crack or fail.
Back to the Type 11.As we're getting off-topic.
To recap - Is there just 4 of us who have one ? VT FUSE, Brased, M0FY Andy, & myself? Plus one at the ADR Museum at Neatishead.
Have you other guys observed the same circuitry conditions as myself ? What faults & component breakdowns have you experienced ?

Regards, David

[M0FYA Andy]

Mine is well down a very deep restoration pile, so I can't answer your question. It's very dirty and needs a good clean inside and out before going any further.
Andy

[Sean Williams]

I've got one lurking in the to do pile as well now......

[VT FUSE]

my Scope came via a 3rd party who had woken it slowly on a Variac whilst carefully monitoring conditions.

There is no real sign that it was poorly assembled/soldered or modified,it was stored in dry heated conditions for decades however and is thus in true Museum condition.

When I first mentioned possible associations with "ELSIE" AA targeting Radar,perhaps I should have said then that this system was a development or offshoot of "AI" flown Radar since the "target" would have been the same! and therefore these scopes may have been in use in Night Fighter Sqd'n service too?.

Both systems were designed by different teams,very likely not aware of each other,in close proximity, but a commonality of support instrumentation would make total sense.

Much more to come out in this thread I feel.....

[David Simpson]

Well folks, I'm getting close now. HT & EHT now spot-on. Ripple-free HT. Decent Brill & Focus, and super sawtooth. Had to change several resistors, associated with V3 & V4, in my efforts to get the 'X' Amplitude wider than 1/2". Still 1/2" short of the recommended 2". The choice of matching V3 to a decent VR65 Pentode is critical. Should have marked the original VR65 used for V4 when I pulled all the valves initially for testing.
If any other owner has a Type11 circuit diagram to look at, I'd be grateful for any hints at increasing the X width.
'Fine Freq' needs a wee tweak every min or two, as the sinusoidal display starts to wander L or R. But hey, this thing is almost my age. I'm sure I wander slightly when I'm out for the daily walk with my wife & lab.
If any of you guys, with an old Type11 in need of much TLC, don't think you'll get round to start working on it - my fellow Cossor 339 enthusiast Forum chum - Mark James - fancies having a shot at one. Perhaps you could send him a PM, please.

Regards, David

[David Simpson]

Advice needed please on restoring the faceplate. Folk may remember earlier this year my efforts with the wee EMI scope's brass faceplate. I did initially post a 'Services Req.' thread, but no one offered.
This time the plate is flat & made of steel. The etched lettering stamped into the steel is slightly bigger and nowhere as near fine as the EMI's. Rust has made inroads into the plate in patches, & in & around the lettering. The top layer of paint is a dull military green, over a grey primer. The steel had been originally plated. The lettering was originally white.
The AM ID's top left & right are just stick-on labels.
I've used a Deremel with a wee s/steel brush & some 600 gauge emery cloth, & paint thinners, so far.
Thankfully, all the pots, switches, etc. were wired with stiff copper wiring. With the faceplate off, it should be jolly easy to give them all a good clean.
Re the 'X' width, am now just 3/8" short. But hey - me & this scope are from the 1940's. So who am I to complain of the loss of 3/8".

Regards, David

[David Simpson]

Well, no advice offered, so have soldiered on. After a serious, but careful rub down, to remove rust & pitting - applied two coats of acrylic grey primer, then two coats of "so called" Army green acrylic paint.(It was the nearest wee tinny of green paint that the guy in the paint shop assured me was ideal).
Thankfully, praise the Lord, the lettering indentations remain intact, and will hopefully accept careful application of whiting. Then a final two coats of clear acrylic lacquer.

Regards, David

PS. I did rotate the pictures in the SD card file, but they've returned to their original state somehow during the attachment procedure. Sorry. D

[trh01uk]

David,

it looks like you have taken the right approach, judging by the photo of the result. More drastic options would have been to sandblast it down to remove all paint and rust, and then fill any indentations left. After further sanding you would get a really smooth surface, and could then respray.

An alternative would be just to get a replica made out of new metal, which would also need spraying of course, and the lettering cut.

I can't see from the result you have achieved that either of these approaches would be required, though if you wanted back "as new" you would probably have to resort to one or the other.

I am slightly puzzled by the colour you have chosen? Why green? Why not match the original grey?

Richard

[David Simpson]

Richard, you'll see back in post 67 that I'd said that the paint was originally a "dull military green over a grey primer". Hence the green paint job.
I feared that shot blasting would have left too little of the lettering left, if it was to remove all the pitting also. Also, to purchase a new replica face plate plus getting the lettering done, would have been totally un-economic - considering the worth of the Type 11. A rare HP or Tek scope - yes, but not an old surplus war-time Air Ministry 'scope. Back in post 67 I also mentioned that it had been plated underneath the old grey primer. Some of that plating had also suffered from the rust pitting. Considering the options, I think that hopefully I've made the right choice. Had there been a wealth of advice given when I asked for it, or some expert Forum guy had offered to have a go - then I would have willingly sent off the faceplate.
The wooden casing is just painted a medium grey over a light grey undercoat. Scratched & chipped in quite a few places. Me thinks that it would look great stripped & sanded back to the original plywood, then just varnished.

Regards, David

[M0FYA Andy]

David,
I would imagine that the Type 11 is much rarer than any HP or Tek oscilloscope.............
A much more intrinsically valuable item, even if not in cash terms, IMHO!
If it could speak I'm sure it would have much more interesting tales to tell.

Andy

[David Simpson]

Right enough Andy, to you & I & other vintage Oscillograph/Oscilloscope enthusiast guys, the Type 11 is worthy of loads of TLC. Particularly with it's association with later WW2 AA Radar systems. The limitations of the optical/mechanical Kerrison Predictor, which seemingly looked like a 1/2 Ton cine camera on a tripod, was experienced in the Blitz. So an AA Radar system(calibrated with Type11's), must have been a great improvement.
However, if I were to try & flog my Cossor 3339, 339, 343, or the Type 11 on eBay, I doubt that there would be any punters offering more than just a few quid, if at all. Bit like my experience based views on Hartley 13A's - horrible heavy lumps of metal.
I just get a lump in my throat every time I see a glow from an SU2150A, or an 807 or a VR65.

Regards, David

[jus_dave]

This is really interesting, I have a Ministry of Air Oscilloscope that my Grandfather gave to me which I was curious in finding out more information. Photographs to follow.

[David Simpson]

Well folks,
I've returned to this interesting old oscilloscope after a few month's diversions.
Have built up the courage to tackle finishing the faceplate. The corrosion pitting in general, & the loss of definition of the lettering in particular, was a worry, if you remember.
Firstly, brushed on some Focus Brilliant White Vinyl Silk Emulsion, and wiped of the excess after it was just about dry. repeated again, but still the fainter lettering still not clear enough. Finally, touched up the lettering with a special white drawing pen,(size 07 white. Made by "Begreen" & called "Pilot".
www.pilotpen.com ).
Finally, the acrylic green("Motip" Autolack Acrylic 44540, which our local motor paint shop reckons was near enough to the old Military Green), was touched up to cover up wee blemishes. Then two coats of Motip Clear Acrylic varnish.
Its come up well, but would have been better if the corrosion hadn't been so bad in places. Now the task of re-assembly.

Regards, David

[6AL5W-Martin]

That is so amazing, please post some pictures when it is back to life

Greetings, Martin.

[David Simpson]

Well Martin & folks, at last the faceplate has been re-instated, CRT re-fitted, & all the pots & switches re-secured. Just R41 - 500K Sync pot needed replacing.
Replaced a couple of more waxies which looked sus. Fired up & fed a sinewave from my Farnell LMF4 Osc. Everything seems tickety boo, thankfully.
Now, a heap of cosmetic work on the wooden cabinet & copper inner lining awaits me.
It might be a while before I can update folk.
Oh yes, forgot to mention - I replaced all the spiky lock-washers behind the locknuts on the switches & pots with NOS fibre washers. Those lock washers were the main culprits for the corrosion problems - cutting right through the original paintwork & the nickel plating - to the sheet steel underneath.

Regards, David

[karesz*]

Great work David, congratulations! I'm waiting curiously for more news.
Best regads, Karl

[David Simpson]

Well folks, have now started on the wooden cabinet with its sheet copper inner lining. The copper was held in place by the tiniest of wee brass panel pins. The grills were held in place by tiny wee brass screws.
They old grey gloss paint is well scratched & cracked. Used my heat gun on the hinged back wooden panel first as a paint stripping trial. Came off pretty easily, but the primer will need a good sanding to get to the grain of the solid pine.
The copper should polish up really nice.

Regards, David

[David Simpson]

Me thinks I've finished, at last ! The chassis is now back inside the repainted wooden cabinet & is looking tickety-boo. Its been a long haul, but well worth it.
I take my hat off to the joiners who built these lovely old wooden pine cabinets back in the 1940's. So, out of respect to them I've left the rear hinged panel just clear varnished. The rest of the cabinet - I've been a good boy & returned it to its military grey colour. The coppersmith who made the inner shielding also did a good job.
Many thanks to electronwilly, and all other folk who advised & encouraged me over the last year.

Regards, David

[M0FYA Andy]

Excellent, that looks really good, well done!
Andy