Re: 2247A PSU Troubleshooting
On Thu, Mar 14, 2019 at 08:29 PM, Nicholas Keller wrote:
But you are correct that this is starting
to feel overwhelming and I am losing confidence :(
Nick, That is the way some of these threads go. You don't need a variac at this stage. A while ago you mentioned you had an isolation transformer, as I recommended and you asked whether to connect the safety ground through to the 'scope. I recommended to do that and Brian S. made some good remarks, which didn't contradict my advice. In your current situation they are not relevant. What *is* relevant is that you isolate the mains-connected part i.e. up to the primary side of T2204 from the mains, nothing more, which is exactly what you did with the isolation transformer. I am not confusing you with another user, no variac or even autotransformer in your situation. OTOH, I'm not sure at the moment what the symptoms with your 'scope were and I'll have to look that up again. Unfortunately, I'll be quite busy over the next few days (promised to repair a few scopes). As long as you realise all the time that *inside* the now isolated (primary) part of your 'scope there are still places carrying a dangerously high potential between them, no longer against your 'scope's case, ground, the floor underneath your feet nor safety earth after you installed the isolation transformer to feed the primary side of the 2247A and you're sure it is in good shape i.e. *if it is safe*, you may take measurements. If you want, let me know what you know about the status and symptoms and I'll be able to look into it within a few days. Three things: 1. Make sure you understand where the dangerous voltages are and between which points, now that you have an isolation transformer installed, and have utter respect for those 2. Make sure you act accordingly 3. Don't despair! Raymond
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Re: TCP202 replacement body parts?
On Thu, Feb 28, 2019 at 4:57 PM Siggi via Groups.Io <siggi= [email protected]> wrote: I tried emailing buy@..., which acknowledged that the parts are
available, but instructed me to call 1-800-833-9200 ext 1 for sales. I
called this number, whereupon a very nice lady acknowledged the
availability and pricing, then proceeded to explain to me how she's unable
to process Canadian credit cards.
She then told me I could send a PO to the email above, and Tek would send
me an invoice, which I could pay by US check. She sincerely wished for me
to have a FedEx account or the like to arrange the shipping, as that's
going to be a problem otherwise also.
She could find no Tek representative in this here cold tundra that could
mediate this business either.
I'm happy to report that a kind gentleman member of this list had some parts he shared with me. I've transplanted the probe to a new housing and the patient looks to have survived. The little ball between the slide and the outer housing is feral, though. I don't know how many times it leaped for freedom, and I was sure I'd lost it several times. He also informed me that these probes are quite delicate and can fail in strange modes. In addition to the performance check in the service manual, he advised running my PG506 through the frequencies available for fast rise or high ampl, looking for "droop" on the measured waveform. Mine was pretty much ruler flat across all settings. In my performance testing this probe well exceeded spec. The rise seems to be on the order of 4.5ns and the 3dB bandwidth is closer to 100MHz than 50. DC accuracy was well inside 1% as received, and although the DC balance was totally out the window, it adjusted fine with the course balance trimmer on the probe.
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Re: 2247A PSU Troubleshooting
In my experience, the main transformer either works, or it doesn't... and yours works. Having an internal short to ground is what killed the few T2204's I know about.
There are about 17 one amp ultra fast diodes that are used to rectify the low voltages on the secondary side of the transformer. About a dozen of them are in a row next to the transformer in the middle of the A18 board and they are known to fail especially if they are marked "ZS" or one other marking which I can't remember. Regardless of markings, follow theT2204 secondaries and see what you get for voltage and ripple as it all gets rectified and filtered.
The Tekscopes message archive will remember the details of this and lots of other problems the 224x family had over the years, and it's all in there for you to read when you search on 2246, etc.
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On 3/14/2019 3:20 PM, Nicholas Keller wrote: It was suggested earlier this this thread that I should find 160-170VDC
across C2202. I tested across R2256 as they appear to share the same
connections, and got 156VDC. Next I checked for ripple using my DMM set to
VAC and got about 2.5V.
I also tested across C2203 by using the same ¡°negative¡± joint of
C2202/R2256 for the black probe and pin 10 of T2204 for the red probe:
result = 40.5VDC
I also got 40.5V at T2204 pins 8 and 9 which should give +7.5V and -7.5V
.... and 38.4V at all DC power pins at J1204
Does this point to a bad T2204? Is C2202 allowing too much ripple?
Thanks for everyone¡¯s support!
Nick
On Thu, Mar 14, 2019 at 3:29 PM Nicholas Keller via Groups.Io <Nirokeforums=
[email protected]> wrote:
OP here. Variacs weren¡¯t mentioned until today so perhaps you are
confusing me with another user. But you are correct that this is starting
to feel overwhelming and I am losing confidence :(
This is the first HV device I have worked on so I am not familiar with all
the components in the 2247A PSU. Most of my experience has been with
analog synthesizers, drum machines, and effects, though often the problem
has been PSU related.
Nick
On Thu, Mar 14, 2019 at 12:56 PM Raymond Domp Frank <hewpatek@...>
wrote:
On Thu, Mar 14, 2019 at 05:03 PM, Brian Symons wrote:
I was only answering to the comment about isolation transformers.
Hi Brian,
I found your post very informative but wanted to keep things as simple and
clear as possible for the OP. I had recommended a Variac and he wasn't sure
what to do. In his case he can either connect safety earth or not.
Raymond
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Re: 2247A PSU Troubleshooting
It was suggested earlier this this thread that I should find 160-170VDC across C2202. I tested across R2256 as they appear to share the same connections, and got 156VDC. Next I checked for ripple using my DMM set to VAC and got about 2.5V. I also tested across C2203 by using the same ¡°negative¡± joint of C2202/R2256 for the black probe and pin 10 of T2204 for the red probe: result = 40.5VDC I also got 40.5V at T2204 pins 8 and 9 which should give +7.5V and -7.5V .... and 38.4V at all DC power pins at J1204 Does this point to a bad T2204? Is C2202 allowing too much ripple? Thanks for everyone¡¯s support! Nick On Thu, Mar 14, 2019 at 3:29 PM Nicholas Keller via Groups.Io <Nirokeforums= [email protected]> wrote: OP here. Variacs weren¡¯t mentioned until today so perhaps you are
confusing me with another user. But you are correct that this is starting
to feel overwhelming and I am losing confidence :(
This is the first HV device I have worked on so I am not familiar with all
the components in the 2247A PSU. Most of my experience has been with
analog synthesizers, drum machines, and effects, though often the problem
has been PSU related.
Nick
On Thu, Mar 14, 2019 at 12:56 PM Raymond Domp Frank <hewpatek@...>
wrote:
On Thu, Mar 14, 2019 at 05:03 PM, Brian Symons wrote:
I was only answering to the comment about isolation transformers.
Hi Brian,
I found your post very informative but wanted to keep things as simple and
clear as possible for the OP. I had recommended a Variac and he wasn't sure
what to do. In his case he can either connect safety earth or not.
Raymond
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Re: Test input for an SD-32 sampling head
Chris, I think you refer here to the so-called "nose-to-nose" method of characterizing sampling scopes (Rush e.a.).
Albert
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On Thu, Mar 14, 2019 at 11:37 AM, cmjones01 wrote:
With difficulty. I believe there's a method involving three sampling heads
looking at each other's kickout pulses and some maths which can be used to
evaluate their performance.
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Re: Test input for an SD-32 sampling head
Reginald,
To obtain significant NLT compression, you need lots of stages, and a fast and big enough signal to start with - not easily done with conventional electronic and transmission line components. This sort of thing is easier to implement inside an IC made with GaAs or SiGe or such, where you can build many of the same thing, on a tiny scale. I think you'll find that most modern treatises on the subject (at least for very high speeds) are about using them within ICs - the physics is the same, but it does not readily translate to putting up a simple lumped element and transmission line system copy.
With the scale of parts and assemblies we can typically handle and see (with magnification) and build and work with, it may be OK to go from a one nanosecond range, compressing to tens of picoseconds, if you have enough stages - maybe 20-100.
Now, if you happen to have access to microwave/RF IC processes, then that's a different story.
Ed
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Re: 2247A PSU Troubleshooting
OP here. Variacs weren¡¯t mentioned until today so perhaps you are confusing me with another user. But you are correct that this is starting to feel overwhelming and I am losing confidence :( This is the first HV device I have worked on so I am not familiar with all the components in the 2247A PSU. Most of my experience has been with analog synthesizers, drum machines, and effects, though often the problem has been PSU related. Nick On Thu, Mar 14, 2019 at 12:56 PM Raymond Domp Frank <hewpatek@...> wrote: On Thu, Mar 14, 2019 at 05:03 PM, Brian Symons wrote:
I was only answering to the comment about isolation transformers.
Hi Brian,
I found your post very informative but wanted to keep things as simple and
clear as possible for the OP. I had recommended a Variac and he wasn't sure
what to do. In his case he can either connect safety earth or not.
Raymond
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Free for shipping: Tekelec V.35 interface module
Got it from the Telogy auctions years ago and have no use for it.? No part number, but comes with v.35 cable and internal ribbon cable.? Can provide photos to interested parties (please contact me directly).? Ships from 94085
-Dave
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Re: WTB 012-0648-00 6 pin LEMO M-M 30" cable for Tracking Generator
Hi Is 1s, 12mm, not 2s, 14,8mm Regards Miguel -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Miguel Work Enviado el: jueves, 14 de marzo de 2019 19:52 Para: [email protected]Asunto: Re: [TekScopes] WTB 012-0648-00 6 pin LEMO M-M 30" cable for Tracking Generator is this? -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Dennis Tillman W7PF Enviado el: jueves, 14 de marzo de 2019 2:24 Para: [email protected]Asunto: [TekScopes] WTB 012-0648-00 6 pin LEMO M-M 30" cable for Tracking Generator I got my TR502 Tracking Generator, DC508 Option 7, and TM503 Option 7 all set up and I then discovered I need the 6 pin LEMO cable (3 male pins and 3 female pins) that goes from the Spectrum Analyzer to the TR502 Tracking Generator Logic . The part number is 012-0648-00. If anyone has one for sale please contact me OFF LIST at dennis at ridesoft dot com. Thank you, Dennis Tillman W7PF
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Re: WTB 012-0648-00 6 pin LEMO M-M 30" cable for Tracking Generator
is this? -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Dennis Tillman W7PF Enviado el: jueves, 14 de marzo de 2019 2:24 Para: [email protected]Asunto: [TekScopes] WTB 012-0648-00 6 pin LEMO M-M 30" cable for Tracking Generator I got my TR502 Tracking Generator, DC508 Option 7, and TM503 Option 7 all set up and I then discovered I need the 6 pin LEMO cable (3 male pins and 3 female pins) that goes from the Spectrum Analyzer to the TR502 Tracking Generator Logic . The part number is 012-0648-00. If anyone has one for sale please contact me OFF LIST at dennis at ridesoft dot com. Thank you, Dennis Tillman W7PF
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Re: Test input for an SD-32 sampling head
LOL With *great* difficulty. That's a large part of the appeal of the project. It's not very expensive and if I succeed serious bragging rights. It would be great fun to take to a Keysight trade show booth and put on their new 110 GHz DSO to check it.
I'll have to give an algebraic solution some thought. That had not occurred to me. I can't justify buying 3 fast heads. Just one is a real stretch to justify. But there may be a useful mathematical subterfuge.
Courtesy of a member of the EEVblog forum who was kind enough to give me the magic phrase, I found Michael Case's 1993 doctoral dissertation at UC Santa Barbara on "non-linear transmission line pulse generators". Very interesting approach. It uses the dispersion produced by reverse biased diodes at appropriate intervals to steepen the leading edge. I've only given it a quick glance. For reading I'll want a paper copy. But starting with a 21 pS edge from the laser diode driver Leo Bodnar is using i might not be too difficult. I'll have to work on the math a bit.
Have Fun!
Reg
I'm hoping that someone involved with the SD-30/32 heads will wander along and tell us how they did it at the factory.
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Re: 2247A PSU Troubleshooting
I have a Danica SV03 which is an isolated 3A variable source with V & A meters, but when you look inside it is simply a standard variable transformer with a separate isolation transformer so wouldn't be difficult to reproduce something like it.
Adrian
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On 3/14/2019 5:15 PM, David C. Partridge wrote: All variacs that I know of are auto-tranformers, so no isolation.
David
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John Williams
Sent: 14 March 2019 16:23
To: [email protected]
Subject: Re: [TekScopes] 2247A PSU Troubleshooting
Interesting information Brian. I have often wondered if a Variac would provide isolation also. I have never checked mine I probably should. Regards John
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Re: 2247A PSU Troubleshooting
There are variacs with an isolation transformer built in. But very rare. I own one made by Philips a dutch company.
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On 14 mrt. 2019, at 18:15, David C. Partridge <david.partridge@...> wrote:
All variacs that I know of are auto-tranformers, so no isolation.
David
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John Williams
Sent: 14 March 2019 16:23
To: [email protected]
Subject: Re: [TekScopes] 2247A PSU Troubleshooting
Interesting information Brian. I have often wondered if a Variac would provide isolation also. I have never checked mine I probably should. Regards John
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Re: 2247A PSU Troubleshooting
All variacs that I know of are auto-tranformers, so no isolation.
David
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of John Williams Sent: 14 March 2019 16:23 To: [email protected]Subject: Re: [TekScopes] 2247A PSU Troubleshooting Interesting information Brian. I have often wondered if a Variac would provide isolation also. I have never checked mine I probably should. Regards John
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Re: 2247A PSU Troubleshooting
On Thu, Mar 14, 2019 at 05:03 PM, Brian Symons wrote:
I was only answering to the comment about isolation transformers.
Hi Brian, I found your post very informative but wanted to keep things as simple and clear as possible for the OP. I had recommended a Variac and he wasn't sure what to do. In his case he can either connect safety earth or not. Raymond
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Re: 2247A PSU Troubleshooting
On Thu, 14 Mar 2019 09:22:35 -0700, you wrote: Interesting information Brian. I have often wondered if a Variac would provide isolation also. I have never checked mine I probably should. Regards John Variacs are tapped autotransformers. No isolation. You can get an assembly that combines a variac with an isolation transformer. Some companies make a device specifically for checking leakage and isolation, though. Harvey
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Re: 2247A PSU Troubleshooting
On Thu, Mar 14, 2019 at 05:22 PM, John Williams wrote:
I have often wondered if a Variac would provide isolation also.
In general, no. A Variac is just a primary with an adjustable tap. Variacs with isolation exist, having their adjustable tap on a secondary winding. Raymond
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Re: 577 Curve tracer ringing CRT and noisy step generator
/g/TekScopes/album?id=86536&p=Name,,,20,1,0,0 Updates to the photo gallery, probing the base of the 177 test fixtures reveals small parasitic spikes, I believe this is what is causing the garbled trace I am experiencing, now to trace where that is coming from
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Re: 2247A PSU Troubleshooting
Interesting information Brian. I have often wondered if a Variac would provide isolation also. I have never checked mine I probably should. Regards John
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Re: 2247A PSU Troubleshooting
I was only answering to the comment about isolation transformers.
If any user gets one then I hope they can check them out to be sure that they are safe instead of expecting it to work & getting bitten.
Having purchased one that was dangerous - a 'lecky had obviously "fixed it to make it safe" which could have killed a user & finding two on test benches that were also dangerous, I just wished to make a purchaser or user aware of possible dangers that may not have been apparent.
I used to do quite a bit of "test & tag" & I found a hell of a lot of dangerous gear even on techs benches.
One of the jobs had several isolation transformers with the through earth of various sizes used for mains filtration so that's how I learned about them.
I saw one of them listed a while ago on eBay as a "test equipment" which it obviously isn't & other users may not have been aware of isolation transformers that aren't designed for the service industry..
Regards,
Brian.
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On 14-Mar.-19 22:57, Raymond Domp Frank wrote: On Thu, Mar 14, 2019 at 05:18 AM, Brian Symons wrote:
*Re: Isolation Transformers*
When using an isolation transformer for troubleshooting you do not want an
earth being connected through.
The whole idea is to break any reference between earth & the mains.
The winding will make both outputs fully isolated from earth so that you can
measure them safely.
This is one time that earth is your enemy.
Brian,
Let's not confuse the OP.
He has a 'scope with a HV (mains switching power supply) part that is galvanically connected to the mains and a LV part that is under normal conditions separated from the HV part through an internal "HF" transformer (inverter output).
Safety earth is normally connected to the 'scope's chassis, not the HV part.
The OP wants to do tests in the rather complicated HV part.
By earthing the chassis and the LV part, the HV part stays isolated.
For all intents and purposes, the LV part is a second isolated part (internal transformer) and there's no reason to float the chassis.
Raymond
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Raymond Domp Frank
Fred Schumacher
David C. Partridge
John Williams