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For Sale: Tektronix oscilloscopes
I have stopped refurbishing test gear for fun to focus on other more RF-ish design pursuits. As I can't abide having stuff around that isn't being used, I have started pulling equipment from my bench and storage, figuring out its condition, and selling it.
I am located in Portland, Oregon. While I prefer local buyers, I will ship anywhere in the United States as long as the buyer covers the actual cost. I am sorry but I don't want to deal with customs and overseas shipping right now. I am also willing to drive within an hour or so of home to facilitate a transaction. Think my prices are ridiculous, make me an offer. Payment terms: cash, Zelle, USPS money order or bank check (gear shipped when cleared). If you are interested in something, please send me an email (K7WXW at qrpdx dot net) in preference to responding here, which will be easier on everyone involved. In this batch: - Tektronix 2465, SN B025686. In working condition, w/ original service and operators manuals, all knobs intact, intermittent light fan noise, excellent cosmetic condition. $250 plus shipping. - Tektronix 475A, SN B016612. In working condition, all knobs intact, good cosmetic condition. $200 plus shipping - (2) Tektronix 485s, SN B155585 and B061036. Sold as a pair only. B155585 in working condition, all knobs intact, some sticky actuators and switches, good cosmetic condition. B061036 powers up, screen illuminates, no traces, a couple of cracked knobs, for parts. A refurbishing project I never got around to doing. $225 for the pair plus shipping. I have other non-Tektronix gear for sale or to be sold, which will be listed on other forums. Let me know if you want to know where. Thanks for looking - Bill |
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Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps
Yes, you found the right info. The WE document shows in fig. 6 an example bounce of 500 us, and in chapter the 3.2 calculation the specified bounce time is 10ms. That is also the value I normally use. Fig 7 shows the proper solution, R2 is the minimum resistor for the delay, and also isolates the switch from the capacitor.
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If you split that resistor in two, and place the cap in between, you can have a low-pass filter and also a minimum impedance to allow the '139 to pull down the signal line through the S210 / 220 / 230 switch, without being loaded by the capacitor. Some optimization of values will have to be done. A better solution of course is adding a real low pass filter + Schmidt trigger to clean up quadrature encoder outputs before being passed to the bus inputs. However, studying the circuit again - what are the 'encoders'? I thought, the pull-ups were used to sense off-board quadrature decoders with switches to GND, but that bus is connected to lots of logic, not to quadrature encoders. So, are the 'encoders' S210/220/230 (which are switches)? In that case those switches are read on a multiplexed bus, de-bounce is done in software and cannot be done in hardware, that would mess up all bus sensing. Cleaning the contacts, or replacing the 'encoders' (better named switches I think) is the best you can do. Arie On 2024-03-06 20:40, Christian F1GWR wrote:
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Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps
It will not be dissipated by the Hi-Z of the input, but by the *Lo-Z* of the HC139 *output* transistor which selects the corresponding switch.
About bouncing duration see oscillograms examples: Again the question is still: is there a solution to avoid or limit the value jumps? |
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Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps
I've never seen bouncing that short, but you may have excellent bouncing encoders. Most people use 10..100nF and that will hurt.
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Yes, I studied the diagram on that page. Cap over resistor is same as cap over switch - on closing, the charging current will go via the low-impedance path via VCC to GND so the current spike is the same. It will not be dissipated by the hi-Z input of the HC139. Arie On 2024-03-06 18:57, Christian F1GWR wrote:
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Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps
@ Arie de Muijnck
As bouncing is typically short (~ .5 ... 1 ms) following mechanical action we are talking about 100 pF...1 nF; under 5 V this means .5 to 5 nC which is very low. If you read me well you'd have seen that my purpose is to parallel the resistances, not the switches. Did you have a look at the mentionned schematic? The power induced by capacitors switching will be dissipated by the 74HC139. According to its datasheet formula (Note 1) estimated Pd will be 26 nW per coder step and per gate, worst case. Also very low. Anyway the question is still: is there a solution to avoid or limit the value jumps? |
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Re: Sony/Tektronix 370 : Gray Encoders unexpected value jumps
On 2024-03-06 13:48, Christian F1GWR wrote:
Don;t do that. Placing a filter cap _directly_ over a contact will cause big discharge currents and will damage the contact. Always use a resistor in between to limit the current. Arie |
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Sony/Tektronix 370 : Gray Encoders unexpected value jumps
When rotating Vert, Horiz and Step/Offset front panel knobs large unexpected jumps in settings occur.
Gray encoders S210-220-230 are unobtainum. Unsoldered the culprits, unmounted the sealed blue plastic parts and drowned them into alcohol for 24 hours as they had oil stains over them. Unfortunately this didn't help. Now the question is: wouldn't there instead be a contact bouncing phenomenon misleading the MC68000 processor? If this is the case would it be wise to add integrating caps in parallel to the R130...4 pull-ups? (see Service Man p.303 here: ) Or would this mod impair other processor I/O's? Any help appreciated. |
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Sony/Tektronix 370 Curve Tracer "drawer" pull-out for servicing
It took me some time to find out, as the service manual does not explicit what the "drawer" is. It appears this is the lower part of the tracer, under the display and upper front panel. It's a slider assembly including Lower Key panel, Bubble memory, component fixtures holder, collector supply switch. Explanation only appears in 370B Service Manual on page 4-15. You must remove two lower lateral brackets (with adjustable potentiometers markings) held each by 8 screws (four flat-head and four round-head. And then push forward the said drawer by its rear corners.
HTH. |
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FS: Tektronix 7613 w/Horizontal plug-in in, and vertical plug-in
Hi, I am selling my Tektronix 7613. The scope works perfectly fine. I have uploaded some photos to imgur.
The 7613 itself has some missing parts, which inlide the plastic bezel, and metal blue plastic filter holder. The plastic bits of the readout intensity and beam intensity is missing, but they work. It's obvious in the images. Other than that, nothing else is missing. The selling offer is, one fully functional 7613, a horizontal plug in of your choice, and if you pay an extra $10, you get a 7A26. The choices for the horizontal plug-in are a 7B53A(see notes), or a TD-1085/U(fully funtional) Notes: 7B53A is faulty, this is due to the B-Sweep cam not acruating the B-sweep shaft. This is likely due to brittle plastic that has broken down over time. A sweep still works perfectly fine. B-sweep does work, it's just a mechanical issue. As seen in photos, mixed sweep still works. Also the trigger source select knob on the 7A26 has broken off. Images: Located 95608 Carmichael CA, USA. Hoping to sell for maybe $130? Will consider trades. |
bill K7WXW
Arie de Muijnck
Christian F1GWR
Jean-Paul
radeng
Benjamin Badrakh