Re: Proper Way to Pull Single-Ended Connectors?
Been there. You can replace the broken connectors with DuPont ones. They are cheap, widely used, i.e. in Arduino projects and in various pin counts. They are always black.
Ignacio
toggle quoted message
Show quoted text
El 06/05/2022 a las 16:22, David C. Partridge escribi¨®: Yes, It's always the blue ones that crumble.
D.
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of n4buq
Sent: 06 May 2022 14:41
To: tekscopes <[email protected]>
Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors?
Regarding those harmonica connectors, when I pulled one of them from one of the circuit boards last night (P1306 on the A22 board), it crumbled in my fingers. Interestingly, it was a blue connector. The other colors were okay. I have noticed that the blue connectors have crumbled more consistently in some of my plugins and I'm wondering what a specific color would have to do with this. Presumably they're all mixed with a dye but odd that blue is affected more than the other colors. Anyone else noticed this?
Thanks,
Barry - N4BUQ
--
El software de antivirus Avast ha analizado este correo electr¨®nico en busca de virus.
|
Re: Can't "calibrate" one channel of a 7A26
Tom,
I have to admit that I haven't looked closely at the interior of the plugin attenuators, the manual simply shows a 'black box' with a resistor to ground at the mid-point of the box and I simply assumed that they were constant impedance tee sections. Either way they can show an attenuation greater than, or less than, the designer intended depending on where you get a poor contact or bad solder joint. In the cases I have come across (two or three, I didn't document everything as well as I should) the accompanying symptom is severe aberration on the edges of the square wave from the calibrator.
Regards,
Roger
|
Re: Proper Way to Pull Single-Ended Connectors?
Yes, It's always the blue ones that crumble.
D.
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of n4buq Sent: 06 May 2022 14:41 To: tekscopes < [email protected]> Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors? Regarding those harmonica connectors, when I pulled one of them from one of the circuit boards last night (P1306 on the A22 board), it crumbled in my fingers. Interestingly, it was a blue connector. The other colors were okay. I have noticed that the blue connectors have crumbled more consistently in some of my plugins and I'm wondering what a specific color would have to do with this. Presumably they're all mixed with a dye but odd that blue is affected more than the other colors. Anyone else noticed this? Thanks, Barry - N4BUQ
|
Re: Proper Way to Pull Single-Ended Connectors?
Regarding those harmonica connectors, when I pulled one of them from one of the circuit boards last night (P1306 on the A22 board), it crumbled in my fingers. Interestingly, it was a blue connector. The other colors were okay. I have noticed that the blue connectors have crumbled more consistently in some of my plugins and I'm wondering what a specific color would have to do with this. Presumably they're all mixed with a dye but odd that blue is affected more than the other colors. Anyone else noticed this?
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "n4buq" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, May 5, 2022 8:07:06 AM
Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors? Jon,
Yes, I'm familiar with the "harmonica" connectors. The 7704A uses them
extensively as well as the plugins and that makes taking the 7704A apart quite
a bit easier. The 7514 uses a half dozen of those to the Main Interface, but
there are many, many individual slide-on connectors that must be removed in
order to remove that board. The manual mentions those but I didn't realize
there'd be so many of them!
Yes, I could clean it with IPA and can remove sub-boards and clean them;
however, the plugin socket side covers are in very bad shape and I'd like to
have the Main Interface board out to better see what I can do about that. If I
had a complete set of covers, then that might not be necessary but if I have to
try and find a substitute method for those, then having that board out where I
can access it directly will be much better.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jean-Paul" <jonpaul@...>
To: "tekscopes" <[email protected]>
Sent: Thursday, May 5, 2022 7:35:03 AM
Subject: Re: [TekScopes] Proper Way to Pull Single-Ended Connectors? Barry I have no experience on 7514, but most 7000 mainframes use single or
double row inlune black Molex or AMP flat ribbon cable to PCB connectiors, one
name is "harmonica" style.
BEWARE!! over the decades the thin plastic deterioration causes breakage or
crumbling of the connectors plastic!
VERY haed to fix.
If gentle rocking does not release then the pins may he frozen to the
recipticles.
In fact removal may nit be needed, perhaps just a water or isopropyl alcohol
wash can clean up the PCB.
A photo of the dirty board and close-up of connector will be useful
Bon courage
Jon
|
Re: Can't "calibrate" one channel of a 7A26
Swap the attenuators between the channels. If the problem follows the attenuators you have a bad one. They do fail.
|
Re: 2465 Calibration Completed but boot still fails
si_emi_01 I guess I don't understand the slow-moving dot comment. By that, I mean the sweep rate is slow enough and the phosphor persistence is not long enough, to make the whole sweep visible. But I think you understand that part. I don't recall what the slowest sweep rate was, but it was slow enough to make it difficult to see what was happening on the scope. Next time I try it, I will turn off the room lights and lower the scope intensity to see if that will make the intensified parts of the sweep more visible. Same for the high speed sweeps.
|
Re: Fault Finding with a Millivolt Meter
Looking online reveals a confusing selection of techniques, which include voltage injection, milliohm meter use, and spraying IP alcohol and watching where it evaporates first?
I do have a current limiting bench PSU, so perhaps that is what I should use? One fella, says he plugged in the suspect rail, limited to 1A at 500mV and was first able to quickly locate the general area, before homing in by measuring each individual component. This would be a good thing to learn.
|
Fault Finding with a Millivolt Meter
Hi all,
I'm looking for tips and tricks for millivolt fault finding.
I recently ran a long thread whilst finding the solution on a TEK 466 power supply section, and in that thread various members suggested using a millivolt meter to locate the shorted components, and I know the details are already in that thread, however it would be good to have a short compacted thread with all the relevant information.
Apart from the minor detail of not having a miilivolt meter at the time, I struggled to visualise how to know that the component under test wasn't part of rail without any issues? The 466 interface board is a sea of components with six different voltage rails intertwining as the circuits weave their way to the other boards. For example a zener diode from the +5v might sit side-by-side on the board with an identical zener diode from the -8v rail.
Anyway, there is now a 0.xxx range millivolt meter in the toolkit and I am up for another learning curve, so it would be seriously appreciated if we could clarify a few points.
The fact that any shorted or failing component will show the lowest voltage across it is understood.
What is not so clear is whether people differentiate between rails (by colouring-in components on a print, for example?) or just measure across every component on the board? Thinking beyond Tek scopes, some components measure low anyway (a 0.12¦¸ resistor would be one), although they would also be marked as such, but surely there must be short-cuts to avoid measuring 500 components on a packed board if the rail at fault only has 50 in total?
Therefore if anyone can add anything to speed up miilvolt fault finding it would be great.
Thanks in advance,
James
|
Re: Can't "calibrate" one channel of a 7A26
I always thought that the modules were pi-sections (normalizing capacitance across the input, compensating capacitance shunting a resistance bridging input and output, and another resistance across the output).
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 5/6/2022 01:14, Roger Evans via groups.io wrote: The 7A26 has small plug-in fixed attenuator modules underneath the aluminium cover that sits immediately behind the BNC connectors. These are T-section resistor/capacitor networks and can give high or low errors depending if the poor contact is in the arms or leg of the tee. If cleaning the contacts on the cam operated switches fixes the problem then at this stage you don't need to investigate the plugin modules. If after cleaning the cam switches you still have trouble then carefully remove these modules and clean the pins.
If the Ch1/Ch2 error is the same for all positions of the attenuators then you need to look elsewhere as others have suggested.
Best of luck,
Roger
|
Re: Can't "calibrate" one channel of a 7A26
The 7A26 has small plug-in fixed attenuator modules underneath the aluminium cover that sits immediately behind the BNC connectors. These are T-section resistor/capacitor networks and can give high or low errors depending if the poor contact is in the arms or leg of the tee. If cleaning the contacts on the cam operated switches fixes the problem then at this stage you don't need to investigate the plugin modules. If after cleaning the cam switches you still have trouble then carefully remove these modules and clean the pins.
If the Ch1/Ch2 error is the same for all positions of the attenuators then you need to look elsewhere as others have suggested.
Best of luck,
Roger
|
Re: Can't "calibrate" one channel of a 7A26
Hello again
We have many 7A26, the issues you mentioned are common.
LF /DC cal is the first priority. Afterwards HF comp and finally transients response.
Be sure of your calibration sources.
1/ RE attenuator cleaning...very important to follow precautions in manuals. PCB and contacts are easily damaged.
2/ replacement of carbon resistance is not trivial as the self capacitance and inductance of a film or deposited resistance may affect the HF response.
3/ Most such problems on 7A24, 7A26 are resolved by exercising of every control and trimmer, and carefully cleaning switch contacts.
Accuracy of 5..10% is OK on these, its not a precision calibration.
Bon courage
Jon
|
Spotted at RE-PC Tukwila, WA...
As of, at least, yesterday (May 4th) there's a fairly clean (except for the decaying foam in the lid) Tek 496 at RE-PC in Tukwila, WA (600 Andover Park East). Condition unknown, it's sticker priced at around $400.
??? No relation, just a long-time customer. I don't need it, as I've already got an RSA3308.
??? Keep the peace(es).
--
Bruce Lane, ARS KC7GR
kyrrin@...
"Quando Omni Flunkus Moritati" (Red Green)
|
Re: Can't "calibrate" one channel of a 7A26
William,
To expand on what Harvey said, the 1/8W carbon resistors between the dual variable C under the shield can be a/the problem. I have had some that were well out of tolerance which caused problems like you are having. I have found that over 10% out caused problems. After I put in 1/2W 1% types, my problems went away. While I had it open, I also replaced the input 1meg resistors with 1% types as mine were 30% or more high. These resistors plug in like the variable Cs. Be sure to clean the pins and sockets these plug into with 91% IPA or whatever you have that works. I am saying what I found as my problem, you may or may not have this problem. I like the 7A26.
Mark
|
Re: 2232 Scope; What am I seeing?
Is there any audible ticking when that happens? A good start would be to
monitor the various voltages from the PSU section and see if any of them
are dropping out.
toggle quoted message
Show quoted text
On Sat, Apr 30, 2022 at 11:26 AM Harrison <buma7@...> wrote: Picked up a 2232 scope recently at a Club auction. Pulling it from the
case I found the J9011 connector broken and the eight wires to it
dangling. As was suggested in the Group I hard wired the eight wires
directly to the analog power distribution board. Now I seem to have a
trace on both channels and I can acquire a AC and a DC signal. Plus, probe
compensation can be attained. However, at times the trace spikes and
disappears. After which the power light and the SGL Sweep light blink at a
rate of about once per second and a single digit LED display located at the
front of the analog power distribution board flashes. It seems to have
done this for a little as 30 blinks (seconds) to perhaps 60 blinks
(seconds). After this occurs the trace returns and all seems normal until
the nonoccurence of the cycle. I don't see anything in the operators
manual or the service manual referring to this LED display. Is it a set up
issue, operator error or equipment malfunction? I have pretty much stayed
in the analog (non-store) mode but when I did briefly select the digital
mode I did have the proper displays and selections on the CRT. Can anyone
help me better understand what is going on when the unit acts as I
described. Thank you for your input. 73 de N1FAM
|
Re: Can't "calibrate" one channel of a 7A26
If channel 2 is less sensitive than channel 1 (5 v/div vs 10 v/div) regardless of what the display says, you might want to check the set of contacts that switch in the variable attenuator. Once those are cleaned, there is a calibration (IIRC) somewhere in the vertical amplifier before the switch, for channel 2.? I'd have to look to be sure of that, but I'd suspect the switch contacts that short out the variable pot.
Harvey
toggle quoted message
Show quoted text
On 5/5/2022 6:33 PM, k6whp wrote: fingers (i.e., very careful cleaning) would not go amiss -- unless you thing there are other items I should check./
|
Re: Can't "calibrate" one channel of a 7A26
Jon and Roger:
To answer Roger's question, at 4 Vpp with the scope set on 5 Vdiv, ch 1 shows 4 Vpp (80% of one division). Ch 2 shows 10 Vpp. And var control is pushed in and locked.
BUT! I wiggled the switches and noted a distinct jumping in ch 2. Also, comparing the two channels on different settings, the difference changed. Ch 1 was dead-on accurate but ch 2 was not,
Consequently, I am led to believe some attention to the little attenuator fingers (i.e., very careful cleaning) would not go amiss -- unless you thing there are other items I should check./
Thanks
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"
|
@JimAdeny:
I, too, looked for "mod pot" on Ebay. Actually, I found a Bourns 1k/10k concentric pot (article #133006820204, Tek Part n¡ã 311-1411-00).
In the Tek Service Manual the part number is 311-1759-00, and its from Allen-Bradley (not Bourns). Do you think they are interchangeable? I don't know if they are the same, but I think that product line changed hands a few times, so it's quite possible that they are the same. I'm not familiar with the Tek product you're trying to fix, so I don't know how important it would be to be exactly alike. If they're being sold as Mod Pots, I'd suspect that what you'd be getting would be just a different brand on the backplate. There's no advantage to buying something that also has a Tek part number. The current maker/vendor is State Electronics (potentiometers.com.) Sounds like you already found their option chart for the Series 70. Then buy a couple of A-B versions off ebay that have the right value pots in them. If the auction shows the OE part number, the Series 70 chart might help you sort out exactly what's in there. The Mod Pot potentiometers were available in several different tapers as well as reverse tapers, so that's another variable. If you've already taken yours apart, you already know how they are assembled, so you should be able to buy anything with the right resistance (and hope for the right taper), disassemble it and replace your one bad module.
|
Re: Can't "calibrate" one channel of a 7A26
How do the two channels compare using the built in 1kHz calibrator? Is the discrepancy the same for different positions of the V/div switch and different calibrator voltages?
The front panel var control should be pushed in to lock in the cal position.
Roger
|
Re: Can't "calibrate" one channel of a 7A26
scratchy or changed resistance potentiometer?
lube or control cleaner?
jon
|
Re: 2465 Calibration Completed but boot still fails
I guess I don't understand the slow-moving dot comment.
The slowest calibration sweep called out is 10 milliseconds in Calibration step bb. Not seconds.
Ross
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of jimbert4 via groups.io Sent: Thursday, May 05, 2022 7:12 AM To: [email protected]Subject: Re: [TekScopes] 2465 Calibration Completed but boot still fails Yeah, I recalibrated the vertical, but this time I checked all of the calibration voltages of the PSG9080 waveform generator first on my Hantek portable scope and wrote the values down to get the proper voltages. Then the vertical calibration breezed through with no limit errors and when I checked them after calibration, they all looked good. HOWEVER - the uncalibrated dots still returned. This time I noticed that they returned when I changed the sweep rate. So I guess I need to redo the horizontal cal now. Sigh. The horizontal is tough to do accurately on the slow sweep cal. It's hard to see what's happening when the dot is moving slowly across the screen. Also the highest sweep rate gets difficult to see. But I'm determined to get this thing all working, so I will persist. I'm so close now. Then I can move on to something else. I have a friend that inherited his engineer neighbor's house. His neighbor was a horder and his house is totally packed with electronic gear. I was told I could have anything in it that I wanted, for free. That's how I got the 2465. I really don't understand how the 2465 knows it is uncalibrated. Is it comparing its sweep rate to some internal clock? If so, I wonder why it can't just do the whole calibration itself, using its internal clock.
|
David C. Partridge
James55
Jean-Paul
Bruce Lane
k6whp