Re: 1S1 Serial No. 100396 Guernsey
Also,
I have a couple of these 1S1's and get the same response from both. So, either they both share the same fault or more likely, I don't know how the heck to run my scope. I suspect the latter. But anything is possible I suppose. I am at first trying to determine which of the two plug-ins to restore. Then I can go from there.
I do have an extension cable for the scope and plug-in, but had not wanted to move forward until I spoke with you all here. My next step was going to be just go through the CAL procedure and check all the power supplies in the PI and hopefully reveal something there. I would like to at least try to get this "trace to appear, as the restoration might be simple. HA!!!
Thanks for the help folks.
Cheers,
David
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1S1 Serial No. 100396 Guernsey
Good Morning All,
I am trying to restore this 1S1 back to working condition, but I am having difficulty just setting it up in the first place. I am using it in my 556 and having a heck of a time getting a trace at all. I have been through the archives, my manuals, and I am pretty certain I have it set-up properly, but not 100%.
What I do see on the display when I set everything up as per the 1S1 Manual is a remnant of what appears to be a beam of phosphor being lit up from below the display. The "light" or "beam of light" is about 5mm wide, can be controlled by the HORZ POS on the scope, and its origin remains below the bottom of the CRT as it looks like one of those HUGE crowd gathering, attention getting, movie lights that they put in parking lots to attract visitors. Defined horizontally about 5mm wide, shooting up towards the middle of the CRT. I would say the height is about 20mm and quickly fades. Also, it seems that in order to see this "trace", I have to push the intensity about 1/4-turn higher to be visible. This does happen no matter which vertical side of the scope I try.
Please keep in mind that this is by far the most complicated of plug-ins I have worked on and I have ZERO sampling plug-in experience.
Any Thoughts?
Cheers,
David
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Re: Help in using TEK Differential Amp to check Switchmode Supplies
Insulation resistance should be many megaohms, at DC. The standards generally specify a leakage current at operating voltage and a withstand voltage for the hipot test, rather than an insulation resistance. ST On Wed, Nov 19, 2014 at 11:52 AM, Bob Vines bobvines00@... [TekScopes] <TekScopes@...> wrote:
I haven't worked on any power (or any other types of) transformers
yet, but _may_ have a failed one in a (spare) linear power supply for
a PDP-8/E. Is there a "rule of thumb" for when the resistance
measured between either the primary or the secondary and the core
shows when there is a problem with the transformer? Manfred implies
that certainly only 10Kohm is too low, and others in different
discussion threads here have mentioned X-number of Mohms as showing a
good transformer, as far as shorts are concerned.
Where is the "dividing line" between good vs. bad resistance readings
when doing simple (resistance) tests like this (on un-powered
transformers)?
I'd like to use this _basic_ information when working on anything with
a transformer, including my 'scopes.
Thanks,
Bob
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Re: Help in using TEK Differential Amp to check Switchmode Supplies
In Manfred's & Tom's discussion on Testing with Floating 'Scopes,
Manfred stated (on Tuesday, 18 November, 2014 at 0718 (PST)):
[snip]
"I haven't yet given my GFI's any reason to trigger, while working with a
floating scope. But one of the GFI's has already done a good job, by triggering
repeatedly when I was using an old tube-type signal generator. That signal
generator had an ungrounded cabinet and two-prong power plug, like all old stuff
does, and used to give a slight tickle when touching it. Not uncommon, it's
caused by the capacitances between the circuit and the cabinet. But then the
tickles started getting stronger, and some day the GFI started triggering when I
connected the signal generator to a grounded circuit. Time to check the
generator. It turned out that its power transformer had severely degraded
insulation, and had a resistance like ten kiloohm from the primary to the core!"
[snip]
====================
I haven't worked on any power (or any other types of) transformers
yet, but _may_ have a failed one in a (spare) linear power supply for
a PDP-8/E. Is there a "rule of thumb" for when the resistance
measured between either the primary or the secondary and the core
shows when there is a problem with the transformer? Manfred implies
that certainly only 10Kohm is too low, and others in different
discussion threads here have mentioned X-number of Mohms as showing a
good transformer, as far as shorts are concerned.
Where is the "dividing line" between good vs. bad resistance readings
when doing simple (resistance) tests like this (on un-powered
transformers)?
I'd like to use this _basic_ information when working on anything with
a transformer, including my 'scopes.
Thanks,
Bob
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Re: Testing Electrolythics and ordering replacements
Thanks David,
I like the 2khz test I'll try that.
Cheers
Alan
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Re: Testing Electrolythics and ordering replacements
Thanks for the kit suggestion, I have ordered something similar already But this seems good too.
Cheers
Alan
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Re: Using different values of smoothing capacitor for 475 test
Thanks Dan,
I may take you up on that if I can't get any sense out of the printouts, but yes its the layouts I need maybe I take a picture of the real thing and expand them.
Cheers
Alan
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Re: Using different values of smoothing capacitor for 475 test
I have a real 475A hardcopy manual, if there is anything you'd like a clearer copy of I would be happy to scan and PDF. The layout pictures are pretty bad, even in the original manual. The 475A is a slightly higher bandwidth version of the '475. I don't think the power supply would be different, but maybe someone can comment on that.
Dan
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Re: Weird cursor problem on 2465 scope
Yours is the first one reported on this group in my memory. Was it cracked or any physical damage apparent?
I would agree to avoiding pulling the main board but I would extract the leads one at a time with tweezers and a soldering iron with a small tip. Then use a solder sucker to clear the holes. Then solder in a new radial lead cap. You know, try to make it look factory. :)
Good job finding it.
Regards
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----- Original Message -----
From: Scott Burris slburris@... [TekScopes]
To: TekScopes@...
Sent: Tuesday, November 18, 2014 11:04 PM
Subject: Re: [TekScopes] Re: Weird cursor problem on 2465 scope
Finally following up on the cause of this failure...
It turned out to be a faulty C853 on the main board. I put a DMM across it in circuit and got about 300 ohms, even when I reversed the leads. That seemed suspicious to me so I lifted one of the leads. Still measured 300ish ohms. Did a quick capacitance check and instead of 0.47uf, I got 0.02nf. Not a happy capacitor.
To test, I bodged in a 0.1uf cap, and now the cursors work perfectly. So I'll need to get a replacement 0.47uf capacitor. Since I don't fancy removing the A1 board, I was planning to get some SMD caps and connecting the stubs of the original capacitor leads to the SMD pads.
I can't think of another incident where a (non abused) ceramic capacitor has failed. Electrolytics and tantalums, sure, but ceramics? There are 4 of these caps in a row, all related to the cursor signals. I'm tempted to just replace all four. Anyone know if these particular caps have a common failure story?
Scott
> On Nov 16, 2014, at 12:03 PM, sadosp@... [TekScopes] <TekScopes@...> wrote:
>
>
>
>
>
>
>
> ------------------------------------
> Posted by: sadosp@...
> ------------------------------------
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> Yahoo Groups Links
>
>
>
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Re: Weird cursor problem on 2465 scope
Finally following up on the cause of this failure...
It turned out to be a faulty C853 on the main board. I put a DMM across it in circuit and got about 300 ohms, even when I reversed the leads. That seemed suspicious to me so I lifted one of the leads. Still measured 300ish ohms. Did a quick capacitance check and instead of 0.47uf, I got 0.02nf. Not a happy capacitor.
To test, I bodged in a 0.1uf cap, and now the cursors work perfectly. So I'll need to get a replacement 0.47uf capacitor. Since I don't fancy removing the A1 board, I was planning to get some SMD caps and connecting the stubs of the original capacitor leads to the SMD pads.
I can't think of another incident where a (non abused) ceramic capacitor has failed. Electrolytics and tantalums, sure, but ceramics? There are 4 of these caps in a row, all related to the cursor signals. I'm tempted to just replace all four. Anyone know if these particular caps have a common failure story?
Scott
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On Nov 16, 2014, at 12:03 PM, sadosp@... [TekScopes] <TekScopes@...> wrote:
[Non-text portions of this message have been removed]
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Posted by: sadosp@...
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Yahoo Groups Links
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Re: Complete List of TM500/5000 Mainframe Pass Transistors
Hey Magnus,
thanks, but the credit is all to Jerry & Dennis, as they did all the hard work of gathering and collating the data.
I just pushed their data into a spreadsheet, took me all of 10 minutes. The file in the downloads section should be easier to link and to find than the original thread (sadly).
Siggi
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Re: Weird cursor problem on 2465 scope
Hey Panos,
is this your scope in this video? Looks very similar to what Scott describes. Did you fix it yet?
Siggi
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Re: Complete List of TM500/5000 Mainframe Pass Transistors
A word of thanks to Jerry, Dennis and Siggi for the time you have spent when creating and releasing this very useful list.
Highly appreciated!
Cheers,
Magnus
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Re: 2445B Readout problem
That all makes sense from what I remember of the 2445B readout design.
The way I remember it, there are different conditions neccessary for
interrupting the trace to generate the readout or part of the readout versus
generating the readout or part of the readout between sweeps. Since the logic
is complicated, I was going to first make other suggestings for finding the
problem.
Thanks for posting the actual cause of the problem.
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On Tue, 18 Nov 2014 20:23:41 +0000 (UTC), you wrote: Hi David,Yes, atthe end of the sweep the RO is drawn and after that another sweep starts
The mainproblem was a leaking aluminum capacitor in the Readout area and it had destroyed quite a lot of the copper tracks on the board. After restoration the described problemappeared. Another problem was that this 2445B has a third version of the RO schematic,not the low serial or the high serial but something in between and I could not find a schematic of this version. After making adrawing of the schematic of this version and further research I discovered ashort circuit under an IC. (also a result of the leaking capacitor) When thiswas solved the Readout is functioning as it should be.?Rens
On Tuesday, November 18, 2014 7:29 PM, "David davidwhess@... [TekScopes]" <TekScopes@...> wrote:
? The readout multiplexing with the trace on the 24xx series analog oscilloscopes
is complicated.
If the readout is only being drawn at the end of a sweep, then it should be
apparent at even slower sweep speeds. Is this what is happening?
On Wed, 12 Nov 2014 14:15:34 +0000 (UTC), you wrote:
Hi, Ihave a 2445B Readout problem and I am not sure, if it is a real fault or forinstance a wrong position of a jumper somewhere.
Thereadout display is flickering at low sweep speeds, with sweep speeds higher than100 usec. it is not noticeable.
Itappears that the sweep display and the readout display are alternating, aftereach sweep comes a RO display and so on.
Who cangive me some advice?
Thanks,Rens
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Re: 2445B Readout problem
Hi David,Yes, atthe end of the sweep the RO is drawn and after that another sweep starts
The mainproblem was a leaking aluminum capacitor in the Readout area and it had destroyed quite a lot of the copper tracks on the board. After restoration the described problemappeared. Another problem was that this 2445B has a third version of the RO schematic,not the low serial or the high serial but something in between and I could not find a schematic of this version. After making adrawing of the schematic of this version and further research I discovered ashort circuit under an IC. (also a result of the leaking capacitor) When thiswas solved the Readout is functioning as it should be.?Rens
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Show quoted text
On Tuesday, November 18, 2014 7:29 PM, "David davidwhess@... [TekScopes]" <TekScopes@...> wrote: ? The readout multiplexing with the trace on the 24xx series analog oscilloscopes is complicated. If the readout is only being drawn at the end of a sweep, then it should be apparent at even slower sweep speeds. Is this what is happening? On Wed, 12 Nov 2014 14:15:34 +0000 (UTC), you wrote: Hi, Ihave a 2445B Readout problem and I am not sure, if it is a real fault or forinstance a wrong position of a jumper somewhere.
Thereadout display is flickering at low sweep speeds, with sweep speeds higher than100 usec. it is not noticeable.
Itappears that the sweep display and the readout display are alternating, aftereach sweep comes a RO display and so on.
Who cangive me some advice?
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Re: TEK 2236 sweep problem
When you say "sync works", do you mean that the triggering works?
Get a service manual and make sure that you checked all of the low voltage power
supply voltages.
Do you have another oscilloscope to use for testing?
How does XY mode behave? The X and Y position controls should operate evenly
over their range.
Is the sweep accuracy good over the part of the trace which is not compressed?
I might guess that one of the leads going to the horizontal deflection plates
has fallen off and coupling from the intensity signal is coupling into it. This
just requires a visual inspection to verify.
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On 18 Nov 2014 10:26:03 -0800, you wrote: My 2236 has just failed. When I turn up the intensity, the horizontal sweep moves to the right,leaving half the display blank. The left edge of what is displayed is compressed. I pulled the cover and did a quick check of the LVPS voltages and they are ok. I may have missed some. The Vertical inputs and amps seem ok, and sync works. Brightness seems normal. Any ideas?
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Re: 2445B Readout problem
The readout multiplexing with the trace on the 24xx series analog oscilloscopes
is complicated.
If the readout is only being drawn at the end of a sweep, then it should be
apparent at even slower sweep speeds. Is this what is happening?
toggle quoted message
Show quoted text
On Wed, 12 Nov 2014 14:15:34 +0000 (UTC), you wrote: Hi, Ihave a 2445B Readout problem and I am not sure, if it is a real fault or forinstance a wrong position of a jumper somewhere.
Thereadout display is flickering at low sweep speeds, with sweep speeds higher than100 usec. it is not noticeable.
Itappears that the sweep display and the readout display are alternating, aftereach sweep comes a RO display and so on.
Who cangive me some advice?
Thanks,Rens
|
My 2236 has just failed. When I turn up the intensity, the horizontal sweep moves to the right,leaving half the display blank. The left edge of what is displayed is compressed. I pulled the cover and did a quick check of the LVPS voltages and they are ok. I may have missed some. The Vertical inputs and amps seem ok, and sync works. Brightness seems normal. Any ideas?
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Re: isolation transformers
On Mon, 17 Nov 2014 06:49:01 +0100, Stefan Trethan stefan_trethan@... wrote: You know, floating the DUT is only slightly safer.
After all you manipulate around on it, and might touch a heatsink or something.
The isolation transformer is only good before you connect that scope
probe ground lead, then it is no longer floating. I like to use the isolation transformer on the device under test to isolate the neutral which is then connected to ground at the point where the probe ground is attached. This isolates the neutral return current from the oscilloscope ground and prevents a ground loop. The device under test in this case still has a ground connection but instead of it being sourced from the panel, it is local and there is no difference between the neutral and ground voltage. That said, measurement fidelity is much better with a single ended probe.
In half a decade of doing professional SMPS work I haven't zapped
myself once that way and I measure on a hot DUT practically every day.
I always say I don't get paid enough for hurting myself, which is only
half a joke since I really do not get paid enough to take risks. I have had better results using a single ended probe and isolated device under test than a differential probe where this is feasible but even better was to combine both so that the common mode signal that the differential probe has to deal with is reduced and the differential probe ground return can be directly connected to the device.
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Re: Help in using TEK Differential Amp to check Switchmode Supplies
On Mon, 17 Nov 2014 14:47:21 +0000, Manfred Mornhinweg manfred@... wrote: When I float a scope to take measurements in directly line-connected circuits, I
do know that I have to treat all metal parts of the scope, such as its case,
connectors, metal knobs, test lead connections, etc, as having several hundred
volts on them, relative to me and to ground and to other things. So I don't
touch them, nor do I let them touch other things that have any continuity to
ground. To make connections, adjust settings, etc, I first unplug the DUT from
the line, except with scopes that have plastic knobs, that allow adjusting those
knobs without getting zapped. Besides the safety issue, another thing to watch out for when floating the oscilloscope without an isolation transformer is that excessive voltage across the oscilloscope's line transformer may cause breakdown. I trust my isolation transformer more than the oscilloscope's internal transformer.
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David Hess