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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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28th Sep 2020, 12:35 am | #41 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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Re: HP 8640B displayed freq. is wrong
Re: my post #27.
As a wrote in that post, it is difficult to put into clear wording the bit about the block connector which is located between the motherboard and the time-base board. Attached is a sketch - that hopefully makes things clearer. Al. |
28th Sep 2020, 7:37 am | #42 |
Octode
Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 1,648
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Re: HP 8640B displayed freq. is wrong
Al,
yes, I have vague recollections of that rather strange arrangement when I was working on mine. You said in the earlier post that your "cleaned and polished" the block connector - did you use anything specific to do the cleaning? Isopropylalcohol or something similar? As I recall it was a way of allowing significant variation in the position of the two boards being connected without going to bother of using a multiway flexible cable. I think these connectors later evolved in the "zebra strip" used on LCD panels, where there are alternating bands of conductive and non-conductive rubber - picture enclosed. All one can say in its favour is this type of arrangement can work, and obviously does while dirt is held at bay. Richard |
28th Sep 2020, 9:52 am | #43 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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Re: HP 8640B displayed freq. is wrong
I cleaned the contact wires on that block connector and the pcb tracks using metal polish (Solvol Autosol) followed by a wash with I.P.A.
I still feel that that chosen approach to making an inter-board connector by using that method was a poor design idea. A back-to back female edge connector would have been much preferable with suitable RF screening. O.K., so that would probably have meant using a custom designed part, but the 8640 is full of such custom-made parts, anyway. Al. |
28th Sep 2020, 11:01 am | #44 |
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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Re: HP 8640B displayed freq. is wrong
It had to be, it was designed before parts of those natures entered the mainstream. You're looking at one of the fore-runners of a lot of RF technology that we take for granted.
Something like the 8640 is becoming harder to do again. Yes we have amazingly fast logic, but it's all locked away inside CPUs and other complex ASICs. It's remarkably hard to buy a single quick flip-flop. Some can be found at Hittite, but look at the prices! Hittite are now owned by Analog devices. With Hittite's biblical name, I always thought they ought to have the slogan "Devices with which to smite thine competitors" David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
28th Sep 2020, 8:24 pm | #45 | ||
Octode
Join Date: Jul 2009
Location: Cheshire, UK.
Posts: 1,706
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Re: HP 8640B displayed freq. is wrong
Quote:
It is used in a few early 1970's counters in my collection, there is version that wire looms can be soldered to (picture from HP K20-5280A); Plus they can be used to connect & mount two boards at right angles (used in HP 5326/7 series, picture from 5326B); David |
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