4th May 2020, 3:13 pm | #41 |
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Re: HP8640B Signal Generator
It's certainly a relief to know I've not been wasting my time David.
Tuning is restricted (but correct) due to the plastic bits jamming up (see the two pictures) and the range switch does not alter the display. Allan |
4th May 2020, 6:10 pm | #42 |
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Re: HP8640B Signal Generator
Sounds like the range knob isn't moving the wafer switch that selects dividers and filters.
It also sounds like some of the plastic bits have welded together. You don't want to risk breaking them but you do need to pry them apart. With the output amp known to be a good one, this 8640 is beginning to look worth a set of those brass gears. David
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4th May 2020, 6:35 pm | #43 |
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Re: HP8640B Signal Generator
I think I may be getting close to at least some faults David.
When I first turned it on before the pyrotechnics began, the fan was running, albeit intermittently. Since then it hasn't run but I noticed the body was warm and the blade was stopped with rubbery resistance so extracted the 5.2v regulator and fan controller board. I found odd results at the four TO18 transistors, Q6, 8, 9 and 11 because it seems their legs have corroded. A couple were broken and the others yielded to slight pressure. These are 1853-0050 which seem to be 360mW PNP devices, perhaps with a code SS2107. A pound to a penny there are several others dotted around with the same fault. I'll fit some BCY71 and see if the fan works then hunt down any others... Allan |
4th May 2020, 7:12 pm | #44 | |
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Re: HP8640B Signal Generator
Quote:
Re (1), your A9 assembly could be early wafer switch or later PCB track type (got any pics?). If it is the wafer switch type, beware of misalignment of the switch wafers relative to one another in each 'stack' and between the 'range stack' and the 'deviation stack'. Re (2) ... I agree with David 100% - !! Re. the fan, the bearings are probably suffering from solidified lubricant (almost certainly the factory original) so treatment with Servisol etc. will help. However ... WD40 WILL NOT ... its formulation is as a Water Dispersal agent (if you believe the rumours, 'version 40' was the one approved by a certain defense [sic] procurement department) and any lubrication qualities tend to be short-lived. Guy
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4th May 2020, 7:38 pm | #45 |
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Re: HP8640B Signal Generator
Not easy to take a picture Guy, but they look like mode switches of the style used in VCRs ... gold track and wipers.
The eqt S/No is 1625U01095 made in 1976. The four new BCY71's got the fan working, but perhaps another bad (2 legged) 1853-0050 is in the meter circuit? It must be common to AM/FM/LEVEL because none show a reading. The voltage at the meter is 20/20 Tuning It looks as if the set of plastic thingies all bunch together correctly but unwinding doesn't leave enough clearance for the first tab to miss the post. Possibly the knob was forced clockwise and pushed past the post and now its jammed at about one turn? Allan |
4th May 2020, 8:25 pm | #46 |
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Re: HP8640B Signal Generator
I'm working off of 40 plus year old memories. I think your fan must be a siemens hall-effect one. A silver cylinder with a load of connection tags off of one end in a ring almost the same diameter as the body? Small square board with the amplifiers on it... small transistors.
David
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4th May 2020, 8:38 pm | #47 |
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Re: HP8640B Signal Generator
That's the one David.
There's certainly a lot of wire needed and Siemens pay my pension... Allan |
4th May 2020, 9:35 pm | #48 | |
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Re: HP8640B Signal Generator
Quote:
Brilliant.
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4th May 2020, 9:39 pm | #49 |
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Re: HP8640B Signal Generator
'U' in the serial number ... Palo Alto build, David?
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4th May 2020, 9:43 pm | #50 |
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Re: HP8640B Signal Generator
Something like this then, not sure how much of mine will differ as it's a little newer (SN prefix 2350A). Seems to be a lack of manuals to cover either serial number.
David |
4th May 2020, 9:49 pm | #51 |
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Re: HP8640B Signal Generator
As far as I know "U" is the code for one made in South Queensferry, Scotland.
List of other codes; A = America E = England (Bedford) G = West Germany (Böblingen) J = Japan (made by Yokogawa) U= United Kingdom (South Queensferry) No letter = America David |
4th May 2020, 10:12 pm | #52 |
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Re: HP8640B Signal Generator
Thanks David!
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4th May 2020, 10:41 pm | #53 |
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Re: HP8640B Signal Generator
An American built 8640B!
I'm trying to remember when the last ones were built in the Ferry, at some point sales dropped to the point where it was decided to have a single line, and we had the 8656 to take over, then we did the 8657 a bit later. 2350A says Factory's 8640 was built in week 50 1983, not sure which division. Spokane is a possibility. 1625U is indeed 1976, week 25 and it'll have Tony West's mechanical inspection stamp on the cavity oscillator, vernier assembly and the gear assemblies. Maisey Armes and her gang will have built it on Bill Fulton's line. Good people. David
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4th May 2020, 10:57 pm | #54 |
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Re: HP8640B Signal Generator
I was surprised it was an American one too, Spokane is listed in the front of the 1991 PDF manual, it also says Second Edition, does that mean there are only two full manuals (1974 & 1991) and the in-between ones need the change sheets?
A bit more searching has found the change sheets to cover mine plus a couple of US army manuals for the 8640B here, the only problem is the manuals are just labelled 1,2 & 3, but we can't complain too much; http://ftb.ko4bb.com/getsimple/index...gnal_Generator As it isn't obvious here is a list of what they cover; HP 8640B Maintenance Manual & HP 8640B Service Manual 2 covers 1229A to 1552A (these appear to be the same PDF) HP 8640B Service Manual 3 covers 1435A & 1438A HP 8640B Signal Generator Service Manual-8640B sup 1 covers 2036A to 2408A HP 8640B Service Manual covers 2520A to 2923A Nothing for 1625 then, did they destroy all evidence when the factory in South Queensferry closed? Edit: It does exist (1609A & 1625U), it's being sold as a PDF by Qservice & Artek; https://www.qservice.tv/vpasp/shopco...asp?type=8640b http://artekmanuals.com/manuals/hp-manuals/ Some nice pictures here, including a 360° of the inside; http://hpmemoryproject.org/timeline/...hp8640b_01.htm David Last edited by factory; 4th May 2020 at 11:27 pm. Reason: More info |
4th May 2020, 11:32 pm | #55 |
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Re: HP8640B Signal Generator
Artek have a paid download covering 1625U to 2025U, that's the newest UK manaul I can find (you have to type in 8640B in the search box to find them);
http://artekmanuals.com/manuals/hp-manuals/ David |
5th May 2020, 12:54 am | #56 | |
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Re: HP8640B Signal Generator
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The plant had 4 operations buildings and the canteen. With the loss of employees through redundancies from 2001 onwards operations were moved into a smaller and smaller volume of the site until only one building was occupied... I was long gone by this time. Building 5, the newest one, all stainless and glass, was let out to the police and prisons service for anti-riot training. I'm told it was damaged by flash bombs they used. Buildings 1, 2, 3 were arranged as a strip, acting as a single building. But the occupied area was reduced to only one section. I was told that lack of heating allowed internal rain drains to freez and the roof to flood, resulting in damage and leaks. No problem, the population was down to the point where a move into hired space made sense, the site was sold for housing, but the 2009 financial crash killed the urgency, but nowadays a housing estate stands where so much test gear was once made. The site ran about 80% exports. As part of the move into smaller and smaller space, the library hd to shrink and the librarian was instructed to trash all material older than x years. As for the manufacturing records, I haven't a clue. I bought an HP 201C audio oscillator at an amateur radio sale. Bill Hewlett's circuit but moved into miniature valves and a smaller case. I checked it over and placed it in the equipment display in building 5 reception. I have no idea what became of it, though it wasn't theirs to dispose of. I would have liked to still have it. But I'll keep my eyes open for another one. There was a big sell off of equipment at the end of the old buildings. My current boss bought an amount of it that I'd selected... I knew a lot of the individual items. We actually have the old cert used by TEM to collect instruments for calibration. Definitely a high mileage one, but runs around our place just fine. Through the great years, it was a brilliant place to work, I couldn't imagine leaving, or retiring. I'd be missing out on so many interesting things. By the time I copped a redundancy package in 2005, I had no worries. There was nothing left I'd want to stay for. So I went back to aeroplanes. I'd been with Rolls-Royce before HP, and I found myself in a start-up struggling to get their first product out. Life was fun again. There is a rather long memoir written by John Wastle to be found on the HP memory website. It makes good reading and tells it as it was. I knew John fairly well. and can identify most of the people whose names got changed to protect the alternatively-innocent. David
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5th May 2020, 9:44 am | #57 |
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Re: HP8640B Signal Generator
I was aware, at least, that these things had different bits and pieces inside, but fortunately I'm using a document that describes my example almost down to a T.
It's TM9-4935-601-14-7 which has lots of pictures and circuits. My example doesn't seem to include the auto-ranging function for the meter and I don't think the RF on/off switch cuts off the oscillator though. I have a theory concerning corrosion. The top cover has a squarish area at the rear with a sort of granular dust stuck to it and this stuff was spread around the equipment in clumps, for example along the line of 1853-0050 fan driver transistors where it was stuffed between their legs. Despite being gold flashed these legs seem to have lost the material inside the gold where there are pin-pricks. The granular material has disolved the steel inside the gold. At the opposite side the RF compartment has no top cover so the two circuit boards also had the granular material stuck to the components. A small switch has a corroded top and various gold flashed bits have corrosion showing through. The meter failure might be due to a single duff component such as another legless 1853-0050. Oddly the double transistors and op amp legs still have pristine gold finish. Presumably, whatever was the material, it was corrosive, (to steel even via very thin gold flashing), and decomposed, perhaps when combined with damp atmosphere? I'm "half" scottish but from the other side, Lanarkshire, not the Lothians. What official size is the Allen Key for the tuning and attenuator knobs again? Allan |
5th May 2020, 10:39 am | #58 |
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Re: HP8640B Signal Generator
Here are some pics of the manual I have here
Guy
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5th May 2020, 5:56 pm | #59 |
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Re: HP8640B Signal Generator
Slight progress.
(a) I found the AGC board was plugged in back to front! (b) I'm working to the wrong circuits! (c) Found the reason for the limited tuning range. (d) One of the covers is for a different (but similar) equipment as the diagram on it shows a board parallel to the meter board where there isn't a socket. I don't think the AGC board is damaged (much?) I found the RF detector input to the meter board goes across one of the motherboards to a riser adjacent to the AGC board box and seems to either go to the RF board or is open circuit or has a series resistor mounted out of sight. This riser isn't shown in any of my docs. Tuning problem is in one of the plastic disks allowing the tuner to get stuck in no-mans land past the end stop. Once there you can't get out without persuading the other disks to let the tuner turn. It's slight wear in the disk nearest the cavity. Allan |
5th May 2020, 10:26 pm | #60 | ||
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Re: HP8640B Signal Generator
Quote:
Quote:
#8-32, 5/64" #6-32, 1/16" #4-40, 0.05" (50 thou) Had the same problem with the last two items I repaired (3400A & 412A), wrong manual versions, plus later modifications and in the case of the 3400A incorrect parts fitted. David Last edited by factory; 5th May 2020 at 10:36 pm. |
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