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1A4 Plug-In "Invert Switch" - Tektronix Part No. 260-0723-00
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Hello All.
I am trying to locate a source for the "Invert Switches" used in the 1A4 Plug-in. Their Tektronix Part Number is: "260-0723-00". Does anyone know where I can get these, please? (Mine are faulty now and causing a serious DC imbalance in three out of four of the channels, and the fourth isn't looking so cool...). Thanks in advance. MDA |
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@ Albert: Thanks for the source. - I may look into them.
- What I failed to make clear is that I'm in the UK, so would find it easier and more convenient to deal with people over here. But, if I can't find a more local supplier, Qservice may be the place. @ snapdiode: Yes, I'll certainly give that eBay etc a try. - I've already doused the switches with Servisol and there's definite improvement in three of them, but the behaviour isn't back to normal yet. You're right, they are not in the most accessible of places. If I've got to do any major dismantling, I hope I don't damage anything else in the process... Thanks for your response. @ All: If anyone else knows somewhere in the UK who may carry these switches, please feel free to tell me . MDA. |
¿ªÔÆÌåÓýIt seems everything in the 1A4 is in a
hard-to-get-to place! I'm having to do some work on the channel 2
attenuator module. It was easiest, by far, to actually swap the
channels 1 and 2 modules just to work on the bad one... Anyone who
has seen the 1A4 knows how tricky even that is...
But all that is a price I'm very willing to pay for the superb capabilities of it. :) :) Respectfully,
On 01/26/2014 06:43 PM, mda231@... wrote:Cliff White, W5CNW w5cnw@... ? |
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Took a closer look at the switches on mine. The logo is for CW Switches. http://switches-connectors-custom.cwind.com/item/miniature-slide-switches/ted-panel-mount-miniature-slide-switches-swidgets-/item-1504?&plpver=10&origin=advsrch&by=prod&filter=0&categid=1125&prodid=1047 This is very close dimensionally. http://www.digikey.ca/product-search/en?x=14&y=10&lang=en&site=ca&KeyWords=GF-126-0119 Not quite the same size of pins though. Something I noticed is that the switches are installed a certain height from the PCB, but there's no standoff on the switches. If you decide to go through the trouble of replacing the switches, make sure they're put back in at the same height, otherwise I'm sure the "invert pull" won't work. |
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This is from the switch datasheet. Relative humidity¡ªSwitches will be operable and insulation I've never seen a DC imbalance show up because of a switch, what's the history of this 1A4? You know, if I had just won a 1A4 and had it shipped here in winter at -25C, I'd assume there would be plenty of condensation. |
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@ Cliff: Absolutely! - I was really hoping the faults were in some of the transistors - at least they're in sockets... Just my luck it was the switches.
You're right; it's a superb piece of gear (when it works properly ;-)). - What's wrong with your channel 2? @ snapdiode: Those look very similar indeed. You've tracked down a very definite lead. My switches have different information stamped on the side: "UND. LAB. INC. LIST. 0.5 AMP 125V - A.C.D.C. PHILA. USA." So that's what I went looking for. - It seems Tektronix may have used multiple suppliers to provide these components. Mine are also soldered on both sides of the board, top and underside. - This potential repair job is looking more strenuous by the minute. Now I'm really hoping the switch cleaner will do the trick. @ Albert: Thanks for pointing that out - Let's just hope I can resolve this problem without resorting to a major intervention. MDA. |
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@ snapdiode: The DC imbalance caused by malfunctioning Invert switch is mentioned in the 1A4 Instruction Manual, p.5-8, Table 5-3 "Circuit Isolation Troubleshooting Guide":
"3. No trace or waveform from one of the channels. DC imbalance in the Input Amplifier for the channel affected. Check for faulty INVERT switch (could be caused by mechanical linkage that prevents switch from reaching the full-contact positions)." http://bama.edebris.com/manuals/tek/1a4/ (- At PDF page 92). I've never heard of anyone else having this problem with a 1A4, so maybe I've just been unlucky. But if anyone else has, perhaps they will consider joining the conversation: The more we can learn about these malfunctions, the better. MDA. |
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Yup, but if you look closely, you'll see the little cW logo, with the W
having like wings or something. That was my clue, we've got the same
switches. CW is a huge switch manufacturer, but maybe the logo changed a
bit over the decades.
The CW part numbering system is obtuse, it looks like a sequential bunch of numbers with no obvious way to map the pin type to part number. You just gotta slog through one by one keeping in mind the picture may not be correct... Anyways. I'm pretty sure the PCB is plated through so you'll be able to suck off the solder from the solder side. But I'm gonna ask again, what's the history of this 1A4? I'm afraid that you can break more stuff in the process of stripping down the 1A4 to get to the switches. Just look at the fragile little common mode chokes for example, or all that mechanical cruft. I mean there are other ways you can inject a DC offset in that signal path, like messed up position and identify pots, switches and resistors. |
¿ªÔÆÌåÓý"What's wrong with your channel 2?" --
Well, it's now channel 1. ;) It started as a bit of instability,
ie: trace jumping around with no change to the controls. And the
position wasn't properly centered, such that to center the trace
the position knob had to be at about 10 o'clock. Swapping all the
transistors from CH1 to CH2 one at a time made no difference. Now
that I've swapped the attenuators, the position centering issue is
still on channel 2, but otherwise channel two works perfectly, so
I'll probably leave it alone for now. Channel 1 had the
instability; until now it has a DC bias that drives it way off the
screen. The invert switches which way it is driven off, and
sometimes tapping on the attenuator module switches it too. Upon
further investigation the trace came back if I disconnected one
side of the differential signal from the attenuator to the main
output board. That's a slide on connector that is right before the
invert switch in the signal path. That's where I am so far with
the troubleshooting.
Respectfully,
On 01/27/2014 06:31 PM, mda231@... wrote:Cliff White, W5CNW w5cnw@... ? |
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My switch says in full text Continental Wirt where Wirt is in kind of logo style. This is at the side opposite to that of the rating text mentioned earlier. ==== Yup, but if you look closely, you'll see the little cW logo, with the W having like wings or something. That was my clue, we've got the same switches. CW is a huge switch manufacturer, but maybe the logo changed a bit over the decades. |
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@ snapdiode: I looked again using a strong light and a magnifying glass - there's definitely a logo there. It looks a little bit like a swan with a second vertical line just behind where its neck and head would be.
Sorry - I misread your question about the history of my 1A4: 1) - I bought it about 2 1/2 years ago and it seemed to be functioning fully. It was, however, very dusty on its upper surfaces as though it had been stored uncovered in a loft. 2) Some time after getting it, channel 4 died: No trace visible on screen under normal circumstances, but the trace could be seen by using the beam finder. - It was deflected upwards. 3) Last year, channel 2 malfunctioned. - Trace only visible with beam finder; deflected downwards. Position and Identify controls had no effect. VAR BAL control had no effect. 4) Channel 3 was the next to malfunction, albeit with different symptoms: (sine waves in 20 - 96MHz range produced extremely attenuated displays, and there was no response to DC). - This looks like either an amplification problem or a broken connection behaving like a small capacitor. I suspect the latter. (- Lower frequency sine waves produced a display consisting of spikes characteristic of a differentiator). Finally, channel 1 died in similar fashion to Ch.2 and 4. While tinkering yesterday I accidentally removed the beige plastic connector which exerts force on the Invert switch, so I tested it without the mechanical connection, (as you also suggested): Behaviour was still the same. - It looks like it really is the switch that's at fault. I'm going to carry on with switch cleaner for a while, but it's starting to look inevitable that the switches will have to go... @ Cliff: I agree - best to leave channel 2 alone, at least for now. It sounds useable and not too annoying. Your channel 1 problem sounds somewhat similar to my Ch.1, 2 and 4 faults: Using the beam finder, I can see the trace sits at 9cm with the switch in and 3cm with it pulled. Since removing one of the attenuator slide on connectors restored your trace to the screen, have you tried shorting the pair of them together (Pins "A" and "B" for channel 1)? - This is suggested in the 1A4 manual, (p.5-9). I'm going to investigate Pins "AK" and "AL" from the Position control also. Since you can switch the direction in which the trace is driven off screen by tapping the attenuator module, hopefully the problem is just a loose connection somewhere. @ Albert: I was probably wrong to assume Tek used more than one supplier for these switches. It looks like we've all got the same manufacturer. The other sides of all of mine are blank. The picture in the link to Qservice you sent also has CW written large on the side. MDA. |
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Probably late to this game, but the original invert switch part number is listed with DoD WEBFLIS with a CW part number GF-126-0028, a part number Mouser?has in?stock.? YMMV, as?DoD/Webflis goes on Tek data, and they may have changed part numbers over the years. ? Another note - we had lots of problems with slide switches when I was an Avionics Tech in the navy - Silver Sulfide contamination was the culprit.? CW slide switches are typically with Silver contacts, and a stored plug-in surely might have been exposed to a Sulphur contaminant.? ? We had problems with the MIL Spray cleaner for switches - it dissolved the Silver Sulfide, only to have it congregate in the porous phenolic part of the switch.? Hi-Pot testing at 300V yielded a nice blue-green flame, with static resistances of open contacts in the 100's of Kilohms.? Both CW and UID switches were susceptible.? Our problem was an outgassing rubber environmental seal on a rectangular connector, about 1x4 inches in size.? Storage in excess of 12 years (Vietnam war-stock material) didn't help. ? Cheers, taylor |
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@ taylor: Thanks for the part number. - I checked it on Mouser in the UK and they seem like the original switches:
http://uk.mouser.com/ProductDetail/CW-Industries/GF-126-0028/?qs=%2fha2pyFaduizgFgikLFm9MUHur6zHr%252bbJZYwIKvHDes%3d http://www.mouser.com/catalog/specsheets/GF-126-0327.PDF - All I need to do now is confirm the pin placement is correct, and if so, I'll order some. What you said about your switch problems while in the Navy makes me more certain I've tracked down the source of the malfunction: My 1A4 was definitely not stored under ideal conditions before I bought it! @ snapdiode: Loads of work to go. - And while measuring the resistances of the Position controls, I also discovered that one of those is faulty as well! - I'm sorely tempted to just track down a new 1A4 and buy it before attempting to fix this one! MDA. |
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Well, you won't know any more about a new 1A4. I think 1A4s are a high-strung plugin, there's a lot that can go wrong in there.
I find the assembly of the input attenuators is fragile, it's just lead-to-lead held by so-so solder joints, at least in mine, and some cold solder joints on PCB and weird grainy ones on cables. |