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Old 3rd Feb 2015, 11:25 pm   #61
Ed_Dinning
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Default Re: Cossor 3339 Oscillograph(Scope).

Hi Gents, I think I have one of the blue trace photographic tubes. PM me if interested and I'll see if I can find it.

Ed
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Old 4th Feb 2015, 3:23 am   #62
frankmcvey
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Default Re: Cossor 3339 Oscillograph(Scope) Manual

Quote:
Originally Posted by David Simpson View Post
But then, our workshop at RAF Cosford was awash with old 13A's & loads of spares. Before the Hartley 436 came into general use, it was the main tuition scope for Boy Entrants & Apprentices. Likewise we were awash with AVO 7's. My, how those old bits of gear suffered at the hands of blue uniformed teenagers
Afraid to say that I was one of those blue-uniformed teenagers that you looked after, , David. While I never actually transmitted down the 13A (unlike some!), I was certainly part of the general wear-and-tear! I owe a tremendous amount to the outstanding training I received at No 2 School of Technical Training, so belated thanks to the instructors and the backroom boys in Training Support (who got to fix all the kit that we ********!) for all that I have been and done during my 38 years in the Service. You guys shaped a LOT of lives.

Cheers,

Frank

(Tech App, 109 Entry RAF Cosford, Oct 65 - Oct 68)
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Old 4th Feb 2015, 12:08 pm   #63
David Simpson
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Default Re: Cossor 3339 Oscillograph(Scope).

Frank, a nice reminder of past years & old scopes.
Oct 65 was when I completed my fitters course(241 AWF), & set off for the wireless bay at Finningley. However, a chance encounter with a Yorkshireman J/T resulted in my return to Cosford in May 66 on an exchange posting. Hence my joining a great wee handful of guys in the test eq. repair section(TERS). A year later I was off to Cyprus, & another TERS in 103 MU.
In 1970 I returned as an instructor. I think that 114 entry was the senior entry at the time. Four postings at Cosford might seem excessive, but my Mother was originally a Shropshire lass, hence I had strong Salopian family links. By the time I left, I think 121 or 122 entries were passing through.
38 years in the RAF ! My, you must have reached heady heights, as well as enjoying service life.
I never imagined back then that I'd be gaining great pleasure from repairing & restoring old Cossor scopes, or indeed owning a CT436, all these years later.
You'll find some very helpful guys in this Forum. I know I have.

Regards, David
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Old 5th Feb 2015, 8:20 pm   #64
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

My wife has gone to visit her father for a few days ..... the cats away etc .... Have taken over the kitchen to work on the 339's - see attached photos. I decided to start at the back of the scopes and work forward. The chassis of the 339B is not in too bad nick so I am going to try and keep that as original as possible. All the rubber wire insulation is perished and I have been quite surprised at how brittle the heavy duty single strand inner copper wire is where it enters the solder, several have broken on the least movement - it must have "work hardened" over the last 70 years. I am therefore replacing all the wiring. As I remove and replace a wire on the old chassis I am putting a new one on the resprayed chassis. Along with labels and annotating the circuit diagram I hope to be able to keep track!! All the components are being checked as I get to them. All the 1500v 0.5F metal cased capacitors showed no leak at 540v (as high as I can get) so will hopefully be OK.
Interestingly some old repairs were wrong - electrolytic polarity reversed wrong values etc, also, one original joint had not been soldered at all and a couple of dry joints so far - hope that I can do better. I have an original 339 blue print which I think Sean gave to me, it does not quite match the diagram in the 339 manual. If anyone is interested I will copy the relevant bits.

Mark
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Old 5th Feb 2015, 11:10 pm   #65
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Default Re: Cossor 3339 Oscillograph(Scope).

WME-Bill wanted to know about the Hartley:

According to Jonz valvepage, the Hartley was introduced in 1950s so is post-war - they were still being sold in Tottenham Court Road in the 60s for 22/10/0.
Regards
Roger Walker
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Old 6th Feb 2015, 2:29 pm   #66
avocollector
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Default Re: Cossor 3339 Oscillograph(Scope).

Quote:
Originally Posted by David Simpson View Post
Mark, what a lovely looking chassis. I'm glad that my humble advice & help has helped another 339 enthusiast.
I've been told in the past that there were loads of surplus 339's in the late 40's/early 50's. However, now in the early decades of the 21st century, I reckon there is only a small handful of them in full working order.
I've got one (339) over here in NZ and last time I turned it on it was still going(about 5 years ago). Bought it off a fellow electronics enthusiast for $25 (about 12 UK pounds) back in the mid 80's. This restoration makes me want to see if it still goes.
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Old 6th Feb 2015, 5:38 pm   #67
David Simpson
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Default Re: Cossor 3339 Oscillograph(Scope).

Right enough Roger, the Hartley 13A was a post-war oscilloscope. RAF-wise, for general purpose use, I reckon the chronology was :- 13A, CT436(another Hartley product), HP180A, during my time. Hartley Electromotives Ltd having a big factory on the outskirts of Shrewsbury.
Peter, glad to hear that another 339 is about to receive some TLC down in New Zealand. Please let us know how you get on.
Mark, you're a brave guy to take a chance with incurring your wife's wrath. Re circuit diagrams - I've several, and all are slightly different. I too have a big AO size original works diagram(a 'yellow print', not blue like yours), but I cant find a printers up here to copy it. I reckon that there was such a push to produce the wartime 339 version of the original pre-war 3339, that little discrepancies were bound to happen, circuit diagram-wise.

Regards, David
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Old 12th Mar 2015, 5:27 pm   #68
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

Slowly progressing ..... have now finished wiring the undersides of both chassis. Something more of an undertaking than I had realised! Photos attached. Next back to the upper surface and more wafers, pots and the high power resistors.

Mark
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Old 21st Mar 2015, 12:49 pm   #69
avocollector
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Default Re: Cossor 3339 Oscillograph(Scope).

Here's my 3339 - sitting neglected on a shelf in my shed poor soul
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Old 21st Mar 2015, 2:15 pm   #70
David Simpson
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Default Re: Cossor 3339 Oscillograph(Scope).

Its coming up 5 years since I first started this thread. You'll see that I'd acquired a 3339 in a sorry state. Internally, in particular. Likewise, avocollector's is sorely needing loads of TLC. But, full repair & renovation is achievable.
So, great plaudits to Mark for his endeavours. Ghostly visitations from Prof Puckle for avocollector.

Regards, David
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Old 8th Apr 2015, 12:39 pm   #71
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

The work continues... I have definitely taken on more than I realised! David warned me that the wafer switches and potentiometers may cause some problems - he was correct. Several of the pots had the same fault. The wiper consists of a piece of spring steel which has a right angle bend at the end which is pointed. This locates in a 3mm diameter disc of metal which forms the actual contact against the track. On several of these the disc had come away and the sharp point on the wiper had scored a deep groove in the track which was open circuit from the wiper. I tried making a slightly larger diameter brass disc on the lathe to bridge this but it did not work. I have managed to find enough spares although some are quite worn.
On the wafer switch front you will notice that on the left hand chassis the swiching shaft for the 4 section wafer switch had not been inserted. While doing this one of the rotating wafers got caught and broke - it could have been cracked already. I had a replacement switch but of a different pattern so all 4 wafers had to be replaced - all situated below the now laced wiring. It took several hours of work to do this! The undersides are now complete and work is ongoing on the upper surface wiring.

Mark
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Old 10th Apr 2015, 9:40 pm   #72
Ed_Dinning
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Default Re: Cossor 3339 Oscillograph(Scope).

Hi Mark, that was a common style of switch that was used on instruments back then. If you are going to Golbourne on Sunday you may get lucky in the junk boxes with something like that as well as some of the nice large pots that were used.
Failing that post some pics of the pots and I'll see if I have anything suitable.

Ed
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Old 11th Apr 2015, 4:16 pm   #73
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

Dear Ed,

Thanks for the offer but I was able to find enough passable spares. Hope to see you tomorrow.

Mark
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Old 11th Jun 2015, 5:33 pm   #74
Daimlernut
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Default Re: Cossor 3339 Oscillograph(Scope).

I suppose I will have to own up to joining the Cossor 339 restoration club. I am currently restoring what I believe to be a 339 but no ID plate so could be a 339A so wanted some clarification of the difference. I have in fact 4 of these scopes so have most of the parts I need but there seems to be two types of mains transformer one with all the connections including the mains input taps on the tag board under the chassis and the second one which has the mains connections as separate loose wire tails from the top of the transformer is this a difference between 339 and 339A?
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Old 7th Apr 2016, 2:17 pm   #75
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

Had to put the 339's on one side until recently for various reasons, but they are now both finished! To update - the one I was building on the original chassis ... I did all the basic checks and powered it up on an isolated variac (very cautious about the 1200volts!). Very strange result, no trace on the tube and intermittent voltages registering. Eventually tracked it down to two faults, firstly a non-functioning tube and secondly a fuse holder which was only intermittently conducting. Picture attached shows all functional eventually!

Mark
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Old 7th Apr 2016, 2:32 pm   #76
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

The second 339 was more of a task. I had expected some issues as I had sprayed the chassis and therefore had to provide separate earth wires in many places - in fact this did not cause any problems! I transferred the good tube and valves from the first 339, did all the basic checks and then powered it up as before. Rapidly turned it all off when there was sparking from the back of the underside of the mains transformer. Very dissapointing as I had checked the integretity of all the windings and done insulation tests between all of them. Further inspection revealed one of the connections between windings had come adrift where it dived into the windings. My first thought was to replace it with the transformer from the WWII 'scope but on removing and testing this several of the windings were O/C. The only option appeared to be a repair which I did in situ by lifting the transformer an inch, using a scalpel to shave a hole in the paxolin board around the broken wire. (The paxolin board covered the end of the transformer.) The small protruding piece of wire was then soldered to a piece of tinned copper wire which was then soldered to the loose end of wire and encased in white heat shrink tubing. The attached pictures show the procedure. (Continued in next post.)
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Old 7th Apr 2016, 2:43 pm   #77
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

To give an idea of the inaccessability of the break the attached photo is taken from underneath and shows the repair now encased in white heat shrink at the top of the photo (on the light brown wire). When I first saw the fault my heart sank as removing the mains transformer is a major task. The 'scope was then powered up in a similar fashion to the previous one and worked fine ... see attached photo. I am looking for the Y1 and Y2 shift knobs that some may have noticed are missing from the 'scope in the attached photo - can anyone help? Happy to buy a complete 339 as I suspect that a spare mains transformer may be useful in the future!

I am indebted to many members of the forum for the advice offered but particularly to David Simpson not only for his advice and example but also the parts that he kindly gave me. Thanks also to Sean Williams for the spare CRT's. Having a spare chassis to build onto was a great help - if anyone is planning a re-build I now have a spare chassis that they are welcome to. Next will have to be the 343 wobbulator to make the set!

Mark
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Last edited by Mark James; 7th Apr 2016 at 2:48 pm. Reason: omission
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Old 7th Apr 2016, 6:00 pm   #78
David Simpson
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Default Re: Cossor 3339 Oscillograph(Scope).

Brilliant Job Mark. Its really good to see another two 339's fully refurbished. My only remaining quest, Cossor-wise, is to acquire the 3330 Camera fitment. I've had feelers out amongst the vintage photography fraternity up here for a couple of years, but no joy yet. I suppose that the Cossor Radio Service Rack, which would hold the 339 & a 343, would really complete the whole Oscillograph family. But, quite frankly, I just don't have the room in my wee workshop.
Keep up the good work, Regards, David
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Old 8th Apr 2016, 1:11 pm   #79
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

I forgot to attach a few pictures of the completed chassis yesterday. Firstly the one with the original chassis. I used silicone wire throughout and re-stuffed alll the paper capacitors. The large time base 750v capacitors were re-formed. The high wattage resistors on the twin paxolin rails were all hollow and I managed to conceal new components inside them. I am quite please with the overall appearence in that it retains some of the original character.

Mark
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Old 8th Apr 2016, 1:18 pm   #80
Mark James
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Default Re: Cossor 3339 Oscillograph(Scope).

The second chassis was so rusted that it required shot blasting and painting as detailed in previous posts. However I felt that new components would not look in keeping so I again re-stuffed the paper and metal pack capacitors. On this version the high power resistors were all solid. I tried drilling them but they shattered. I found several degraded hollow wire wound resistors in a junk box at one of the auctions and bought them. Cleaned up and painted they looked in keeping - again with the new components concealed inside. I personally prefer the original chassis although this does look more pristine!

Mark
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