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Old 4th Oct 2021, 8:59 pm   #1
Chris55000
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Default O.U. Generatorscope HK/2A

Hi!

Here are some pictures of the O.U. Scope HK/2A I received this morning, and to say the internal quality of construction is an untidy mess is an understatement!

This instrument uses a Mullard DG7–32 CRT with the 12 pin B12A "duodecal" type base!

Circuit Diagrams will be started over the next few days!

Chris Williams
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Old 4th Oct 2021, 9:03 pm   #2
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Default Re: O.U. Generatorscope HK/2A

Hi!

Second pictures instalment!

Chris Williams
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Old 4th Oct 2021, 9:06 pm   #3
Chris55000
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Default Re: O.U. Generatorscope HK/2A

Hi!

Third instalment of pictures!

(Quite how you're supposed to determine the connections and routing of all this messy wiring I'm not sure, as all the individual connection points on both of the PCB assemblies are simply annotated 'X' on every pin without any other number or letter, etc!)

Chris Williams
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Last edited by Chris55000; 4th Oct 2021 at 9:15 pm.
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Old 9th Oct 2021, 9:05 pm   #4
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Default Re: O.U. Generatorscope HK/2A

Hi!

The fault on it is a total lack of anything on the CRT whatsoever, not even a dot or anything!

There is a faint buzz from the mains transformer at switch–on, but the 160mA mains fuse is fine!

The two ECC83 valves on the main PCB are both fed with 12.6V across pins 4 and 5, the "hct" on pin 9 left unused, and I measured 13 V across here!

There was 245V and 305V at the anodes of the horizontal plate amplifier valve, (the base of the vertical one is covered by a screening plate) altho' I didn't try the horizontal shift control, I suspect it's not doing much!

The CRT base is awkward to get at without a lot of dismantling, and I've received two spare DG7-32 CRTs, (allegedly n.o.s!), but I'm not going to poke about any further – I'll complete my circuit diagrams and parts lists first and then see what the CRT cathode, (but NOT grid – I'll do that by checking the cathode voltage and then ohms tests on the grid circuit!), anode and plate voltages are like when my documents are completed!

Oh yes, the CRT heater hasn't gone, neither is the 6.3V winding on the transformer at fault!)

Chris Williams
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Old 10th Oct 2021, 8:40 pm   #5
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Default Re: O.U. Generatorscope HK/2A

Hi!

It's not possible to see if the CRT heater is alight when the CRT and mu–metal screen is assembled and set up in the 'scope, as the DG7–32 is only a short tube and the back edge of the mu–metal screen covers all the glass part of the neck and partially overlaps the bakelite CRT base, with a rubber padding strip fitted around the base before the mu–metal screen is fitted over the tube!

(Obviously the CRT can be plugged in temporarily without the mu–metal screen, which I will be doing to make sure it is lighting up correctly tho'!)

Chris Williams
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Old 10th Oct 2021, 9:51 pm   #6
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Default Re: O.U. Generatorscope HK/2A

Hi!

First sheet of HK/2A Generatorscope Circuit Diagram Complete!

Chris Williams
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File Type: pdf HK-2A Generatorscope Attenuator & Preamp Sheet 1.pdf (351.7 KB, 74 views)
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Old 10th Oct 2021, 11:05 pm   #7
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Default Re: O.U. Generatorscope HK/2A

I must say that the circuit diagram actually makes sense. Your photos are as you described, a disaster.
I must compliment you on your work. I would not have bothered.

I would call it dedication to fanatical heights.

Thankyou

Joe
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Old 11th Oct 2021, 9:59 am   #8
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Default Re: O.U. Generatorscope HK/2A

Hi!

Like every Member of this Forum I am dedicated to the upkeep and repair of all the pieces of equipment that our erstwhile long–gone British Manufacturers provided, and the production of a clear and readable set of circuit/wiring diagrams is a vital part of that strategy!

If a set of my diagrams helps someone dig out something they'd given up on in despair then the aim of drawing them will have been achieved!

The principles and symbols I use in draughting them were gleaned from many years experience at reading the best and the worst from innumerable different manufacturers, and the standards from our Electronics Construction Magazines, both present and past!

Chris Williams
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Old 11th Oct 2021, 6:50 pm   #9
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Default Re: O.U. Generatorscope HK/2A

Excellent work Chris, I would like to see the full circuit diagram when you have finished it.

Dave
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Old 12th Oct 2021, 6:03 am   #10
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Default Re: O.U. Generatorscope HK/2A

Hi!

The first sheet I uploaded had reference for capacitor C7 duplicated in error which I only noticed after I'd sent it! "C7" in series with the "PREAMP GAIN" pot RV1 should read "C8" and "C8" (1n) between T2 and T3 emitters should read "C9".

I'll upload a revised sheet adding the circuit functions, voltage readings and the preamp PCB done in a lighter background tint after the remainder is completed!

Chris Williams
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Old 13th Oct 2021, 8:50 pm   #11
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Default Re: O.U. Generatorscope HK/2A

Hi!

Next section identified that will be drawn and posted will be the +9V and –9V external power supply regulator circuits, the outputs are brought out to three 4 mm wander sockets at the bottom right–hand corner of the front panel!

The regulator circuits are symmetrical four–transistor arrangements of opposite polarity!

Chris Williams
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Old 13th Oct 2021, 8:54 pm   #12
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Default Re: O.U. Generatorscope HK/2A

I have one of these not working I have been after a schematic for a no of years please post ASAP
Thanks Trev
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Old 17th Oct 2021, 12:46 pm   #13
Chris55000
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Default Re: O.U. Generatorscope HK/2A

Hi!

Power Supply Circuit Diagram, Sheet 7!

The complete documents set, as currently envisaged, runs to 12 pages in total, the other 10 I have still to design and draw, so please bear with me as some of them involve a very considerable amount of work!

Chris Williams
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File Type: pdf HK-2A Generatorscope Power Supply Sheet 7.pdf (376.8 KB, 14 views)
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Old 17th Oct 2021, 2:24 pm   #14
Chris55000
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Default Re: O.U. Generatorscope HK/2A

Hi!

I just noticed after uploading that a component value on Sheet 7 overlapped a diagram line, which I've now corrected!

Please use the sheet 7 attached to this post!

Chris Williams
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File Type: pdf HK-2A Generatorscope Power Supply Sheet 7.pdf (377.9 KB, 18 views)
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Old 17th Oct 2021, 7:10 pm   #15
Chris55000
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Default Re: O.U. Generatorscope HK/2A

Hi!

Sheet 3 for the Vertical and Horizontal Amplifier Valve stages now in progress!

Chris Williams
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