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Old 20th Dec 2014, 6:56 am   #1
Nymrod121
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Default HP8640B signal generator: range/FM tracking

Good morning,

As you'll see from the picture, the 'range vs FM deviation' tracking assembly on my machine has seen better days (!).

The instrument is version 1536U, serial number 00700 and has conventional wafer switches rather than that using plastic discs with spring fingers in conjunction with a dedicated PCB assembly.

The only manuals I have (both soft and printed copy) refer to this assembly as A9 but none of them cover the wafer-switch design.

Does anyone have any information covering this type, please? (I've posted a request on the HP-Agilent user forum as well).

Many thanks and best wishes

Guy
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Old 20th Dec 2014, 10:34 am   #2
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Default Re: HP8640B signal generator: range/FM tracking

The wafer switch design and assembly instructions would have been on drawings later moved onto microfiche inserted into big holes in 80-column cards for machine sorting. I could have accessed them several years ago, but I think they will have gone for paper recovery if not landfill. The wafer switch version may be less common, but it will have had HP part numbers for every bit bought and a full set of engineering drawings.

1536U mens that it was made in the 36th week of 1975 in the plant at South Queensferry.

Take a look at the South end of the Forth Rail Bridge and you'll still see the plant on Google Earth, though it's now been torn town and only earthmovers roam the plain. In 1975, only the eastern two-thirds of the northern building would have been there. Your 8640 will have been built very close to the centre of the northernmost building you'll see on Google.

Tony West's mechanical inspector's stamp will be all over it as well. Tony retired back down to his home area of Northhants.

If you heard on national news of the bloke getting killed by his runaway dustbin lorry 2 weeks ago and it ending up on the pier, across the sea wall at South Queensferry, he was an ex-HP guy. I'm still in touch with some of the people from the old firm, but there was a huge dispersal and there has been inevitable attrition.

A lot went on in that place and there were certainly some interesting characters. I think Hugh's writing a history.

Thinking about it, quite a bit of the books and periodicals library, though I'm fairly sure not the huge archive of drawings went to the museum of communications.

David
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Old 20th Dec 2014, 1:45 pm   #3
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Default Re: HP8640B signal generator: range/FM tracking

Thanks David - very interesting. I found the site from its [Google search result] postcode of EH30 9TG.

Best wishes
Guy
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Old 20th Dec 2014, 2:02 pm   #4
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Default Re: HP8640B signal generator: range/FM tracking

The 8640B is the sig gen I always wanted... but never bought...

However, I do have quite a few manuals for it here because I studied its design a few times.

The best manual I have here has been scanned with searchable text and it appears to cover your version of A9. But maybe you already have this manual and it isn't quite the right one. However, If I search for A9 in the manual it has hundreds of hits and it logs all the changes to A9 over the years.

See below for a jpg of part of the manual showing something like your version of A9. The quality of the manual is far better than the low definition jpg I've attached below and it is quite readable and gives a schematic and parts list etc.

I can email you the manual but it is 11Mb in size so this might hit a size limit for an email.

Hope this is of use...
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Old 20th Dec 2014, 2:47 pm   #5
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Default Re: HP8640B signal generator: range/FM tracking

Guy,

I saw your query on the HP_Agilent Yahoo forum and on here, so one reply should be enough! There are three versions of the HP8640B manual available on the web that I have found. All are available on the BAMA site among others. The 'very early' one does not seem to include circuits, whereas the 'early' and 'late' versions do. Your serial number comes under the 'early' version which is provided as the US Army version in TM 9-4935-601-14-7&P. If you have already found that this manual does not have the detail you need, my other suggestion is to contact Telford Electronics and see whether they have a hard copy manual that covers your exact S/N. I got a manual for my 8640B from them some years ago and they certainly had manuals covering numerous S/N variants at that time. It cost me about £20 back then but well worth it for the big pull-out diagrams.

PS: How are your plastic gears? I had to work on the ones in mine, but achieved acceptable success without having to get or make replacements.

PPS: Jeremy has posted a part of the same US Army manual as I mentioned while I was typing.

Mike
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Old 20th Dec 2014, 5:22 pm   #6
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Default Re: HP8640B signal generator: range/FM tracking

Guy,
you can download your 11MB SM from here (too): http://www.premium-rx.org/ref%20mans...b/HP-8640B.pdf
Karl
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Old 21st Dec 2014, 1:07 am   #7
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Default Re: HP8640B signal generator: range/FM tracking

Thank you all for your time taken in reply.

(1) G0HZU_JMR - Jeremy, I'd be very grateful if you could try emailing me the version you have? - I'll send a PM with my address;

(2) Humber888 - Mike, I'll try Telford on Monday - as regards the gears, I have got two of the cast resin replacements from Emanuele Girlando in Turin (that's only part of my tale of woe, as you can see from the pictures);

(3) karesz - Karl, thanks for providing the link - however pages 297 - 303 of that pdf file indicate the later design of printed board switch tracks by way of a change item and I've not come across anything covering the original wafer-switch assembly ... or have I missed something?

Best wishes
Guy
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Old 21st Dec 2014, 1:41 am   #8
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Default Re: HP8640B signal generator: range/FM tracking

Guy,
check it at page 315 please..
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Old 21st Dec 2014, 2:27 am   #9
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Default Re: HP8640B signal generator: range/FM tracking

Thanks Karl - got it

I've been looking through a pdf copy of the 8640A manual (33MB!) which shows what appears to be an identical mechanical layout to the A9 assembly I have. There's also a note on how to physically align the switch wafers which I'll need to compare with the reality of what I have. so a degree of progress
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Old 21st Dec 2014, 8:22 am   #10
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Default Re: HP8640B signal generator: range/FM tracking

Those bits are polycarbonate. When the generators were made we routinely used 'Inhibisol' and then 'ultraclene' solvent cleaners. It was known that the various polycarbonate materials became dramatically brittle on exposure to these liquids (board extractors fell apart rather than worked, the knobs would split etc)

If I ever got an 8640 I'd assumed I'd bemaking new bits out of brass...

David
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Old 21st Dec 2014, 10:08 am   #11
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Default Re: HP8640B signal generator: range/FM tracking

That figures ... I'd used Servisol contact cleaner on the wafers about two weeks ago while Richard (trh01uk) and I were conducting joint exercises on 8640b repairs over at Malvern.

I've managed to repair with superglue but purely to enable measurements to be taken with a view to rebuilding from new using stock ABS or similar.

Much as I'd prefer it, I can't think in terms of brass because I don't have the necessary tools/lathe etc. and to have them made by a specialist ... well, 'arm/leg/first-born' comes to mind

Best wishes
Guy
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Old 21st Dec 2014, 11:19 am   #12
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Default Re: HP8640B signal generator: range/FM tracking

You don't have to need much machining done before buying a lathe becomes the cheap way out.

I suspect the gears will be stock sizes out of some American late 1960s catalogue. As the US never really has come to grips with the metric system, they'll still be current.

The chlorinated hydrocarbon will have weakened the whole of the plastic part, and the crack will have started from a stress concentration point. Glueing will put the thing back into one piece, but will leace the rest of the piece weak.

How about a couple of normal switches, a bit of logic and a dozen little relays? Always have a plan B.

David
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Old 22nd Dec 2014, 11:26 am   #13
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Default Re: HP8640B signal generator: range/FM tracking

Guy,

Your plastic parts do look pretty sick. My HP8640B uses the newer PCB-mounted FM/bandchange assembly and it is only the plastic gears with a brass hub that have suffered. This seems primarily due to plastic shrinkage against an unchanging bit of brass cracking the gear at a weak point. Since you have some new moulded parts from Italy, you will know that there has been a lot of discussion over the years on the HP_Agilent Equipment forum on methods of repair. The member selling brass gears in the USA charges something like $200 for a set (or is that £s). I seem to remember that people were saying that the gears were not particularly standard US stock items, so had to be cut specially and then stuck together for the bevel gear parts.

I do wonder whether some of the plastic bits could now be made by 3d printing - maybe not the gears but the other coupling parts. The trouble is that ideally you need a CAD drawing of the part to get another made. I have wondered if there are people in the UK that will take your old physical part and make a 3d printed copy from it. Maybe someone on this forum knows of such a company.

Finally, just a comment on superglue. Most formulations do not bond 'greasy' plastics well i.e. polythene, polypropylene, PTFE, etc. However, Loctite do an 'all plastics' two-part superglue that has been very successful here in sticking such plastics together.

Mike
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Old 23rd Dec 2014, 12:54 pm   #14
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Default Re: HP8640B signal generator: range/FM tracking

Thanks for your feedback Mike; since my last posting I've also found references to a visually similar assembly within the manual for the 8640A (retrieved from a website whose details were obtained from 'another place'). I spent an hour selecting/copying 'n pasting the relevant diagrams from the PDF into MS Paint, fitting to A4 then editing with MS Office Picture Manager so I could get a half-decent print from my laser printer. I'll upload the resulting image files (in case anyone else has a need of them) in two batches - first batch of four herewith. This was an experiment in working with Acrobat as much as anything ... I'm going to go through the same exercise with the other file obtained from Karl's link to see if I can get better quality.

I've seen the HP_Agilent forum post regarding brass gears and wil consider this the option of last resort if I can't fashion a reliable alternative from standard plastic materials. Another possibility you mentioned was 3D printing; as it happens, I have a chum who was talking about getting a 3D printer for experimental purposes and I've left him a voicemail for when he returns from holiday ...

Thank you also for your feedback regarding adhesives - very helpful!

Best wishes
Guy
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Old 23rd Dec 2014, 12:56 pm   #15
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Default Re: HP8640B signal generator: range/FM tracking

Second batch (five).

Best wishes
Guy
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Old 5th Sep 2015, 8:44 pm   #16
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Default Re: HP8640B signal generator: range/FM tracking

Evening,

It's been a while getting there ... but at last I have replacement plastic components made for the A9 assembly.

Measurements were taken from the original; acetal rod was sourced locally and machined to size.. The axle pivot pins were made from g.r.p. rods recycled from a scrap Tektronix 7A18 plugin (fine gain control shafts) as 0.125" Acetal rod seems to be 'unobtainium' ...

So progress is being made, albeit slowly.

Best wishes
Guy
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Old 6th Sep 2015, 10:47 am   #17
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Arrow Re: HP8640B signal generator: range/FM tracking

Broken gear wheels, etc. In the distant past I repaired suchlike in my 8640B with Araldite - and many years later, that repair has still held. I've also done same on two other units, with no come-backs . . . yet.

Al.
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Old 7th Sep 2015, 5:48 am   #18
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Default Re: HP8640B signal generator: range/FM tracking

Good to see your making progress Guy. If you need any parts drop me a PM, I have wafer switches and some parts off scopes like odd pots/shafts etc.

Andy.
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Old 7th Sep 2015, 8:01 am   #19
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Default Re: HP8640B signal generator: range/FM tracking

Thanks, Andy!
Best wishes
Guy
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