Michael A. Terrell
Jennifer Crock
My 2247A just failed on me and am looking for some initial thoughts on the likely culprit.
After pressing the on/off button, it immediately goes into a repetitive cycle of clicking (like relays turning on) and briefly flashing all the push-button LEDs.
The CRT never turns on and doesn't display any diagnostic information, obviously.
Before I open the unit up, I'm hoping there's a likely cause for such power-up problems.
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Re: needing to re-home a few 7K
Don I am intrested in some of the 79xx equipment Please contact me off list. Eric On Thu, Mar 9, 2023, 11:51 AM Don AD7LL via <donfrasher=[email protected]> wrote: ? ?It would seem that I have bit off more than I can chew and have far more projects than I can keep up with or have time for. |
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needing to re-home a few 7K
? ?It would seem that I have bit off more than I can chew and have far more projects than I can keep up with or have time for.
I truly do not wish to ship, certainly not the main frames primarily due to time and laziness.? SO if you are in or coming near the Chattanooga - Cleveland Tennessee area and would be interested please let me know. ?Also realize they will all need repair or as parts units. 3 - 7904? - one has the blue crt 1 - 7834 1 - 2465 - has the u800 chip failure as a minimum 2 - 7A19 2 - 7B80 - on with the x-y switch.- switch functions but? only if switch by hand internally 1 - 7B92A 1 - 7B15? 1 - CRT for the 7904's 1 - CRT for the 2465 1 - cable # 012-0648-00? 7K SA to tracking gen ( I think) outer shield missing on one end 1 - HP 8654A? Frequency is stable through all ranges however output levels vary wildly? a few misc? parts / boards for 7904 and 2465 Open to any and all offers as I primarily do not want these to go to the dump.? If no one interested or able to get to this area for the whole lot, then I will place the plug-ins and CRT's on ebay, The Main frames will just have to go.?? No real hurry If I know some one wants the lot but needs time to come down here later, maybe on? a vaca to Dollywood or such. But sooner or later they need to go. Thank you, Don Frasher drfrasher@... donfrasher@... 423-244-1334 |
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
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For those following along:
The jumper (J2726) that connects connect the PSU board to the CRT can be found if you continue following the red cable.. Unlike the other jumpers on the PSU board, it is not found with a header on the PSU board.
I am still unable to figure out a way to disconnect the switch on the PSU board to the mechanical extension arm (part 2-44 in the mechanical parts section). If anyone has any tips, I'd love to hear it.
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
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Thanks again for the earlier info...?I'm now at another crossroad in troubleshooting my 2247A...
How do you fully remove the PSU board from the chassis? The screws to be removed and most jumpers that need to be disconnected are obvious.?
However, there are two connections that I'm not sure about:
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
It is a switching power supply, so anything after the input caps after the rectifier should be low ESR. especially after the transformer. On Tue, Mar 7, 2023 at 9:47?AM Chris Kniker <chris@...> wrote:
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
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Thanks! This is exactly the kind of info I was hoping for when I posted my issue.
Other than the diode replacement info, is there anything special about the caps that may need replacement? low-ESR, etc?
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
If the 'scope has been used regularly, it is unlikely a PSU cap will have dried up.
But, a shorted cap, in the 'scope or PSU could indeed cause such issues.? As could any number of other things sadly. I have old Tek 465 and 468 here (and lots of other similar aged analogue test equipment) that have never been re-capped, and though well out of calibration and in need of some adjustment, they show no signs of PSU (or as yet, any other) capacitor trouble.?? (Scratchy switches and pot's yes, but not power supply/regulator issues.) The above is based on my experience, both as an active hobby user, and professional fixer of such things in the near past. Sadly, true "Diagnosis and Fault Finding" skill's and methods are rarely taught these throw-away days.? :-( Cheers All. ??? Dave G8KBV ??? (Ex Tek UK back in the 70's) -- Created on and sent from a Unix like PC running and using free and open source software: |
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
It looks like your power supply is trying to start but is folding back probably due to a short or overload on one of the power rails.
Could be be a shorted cap. Perhaps a good time to recap that power supply anyhow, if it has never been done before. The other possibility is that one of the hi-speed rectifier diodes of the main inverter power rails has failed. The ones marked either ZM or ZS on them are well known to get leaky after some time and might fail. There was an advisory on all 224x scopes to outright replace them all (total 17 diodes). Original part number is 152-0400-00 (MB2501), and a good replacement would be to use MUR160 600V 1Amp 50nS diodes (Mouser PN 863-MUR160G). Or any 1amp 200-600PIV equivalent fast switching diode will work fine. Do NOT use regular 1N400x diodes. The LV power supply board is located in the middle of the scope and can be accessed by temporarily removing the top board (and the metal shield underneath) that you will see when you open the scope. While there you might want to also check the voltage of the Lithium cell and make sure it is at least 3.0V. Anything less and I would replace that battery, which basically only holds the last settings used. No calibration data is backed up by this battery so it can be easily swapped out with a fresh one without loosing any sensitive data. Before you do anything at all get the service manual, and read through it to familiarize yourself with the basics of the scope, and particularly the LV power supply board. https://w140.com/tekwiki/wiki/2247A |
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
It looks like your power supply is trying to start but is folding back probably due to a short or overload on one of the power rails.
Could be be a shorted cap. Perhaps a good time to recap that power supply anyhow, if it has never been done before. The other possibility is that one of the hi-speed rectifier diodes of the main inverter power rails has failed. The ones marked either ZM or ZS on them are well known to get leaky after some time and might fail. There was an advisory on all 224x scopes to outright replace them all (total 17 diodes). Original part number is 152-0400-00 (MB2501), and a good replacement would be to use MUR160 600V 1Amp 50nS diodes (Mouser PN 863-MUR160G). Or any 1amp 200-600PIV equivalent fast switching diode will work fine. Do NOT use regular 1N400x diodes. The LV power supply board is located in the middle of the scope and can be accessed by temporarily removing the top board (and the metal shield underneath) that you will see when you open the scope. While there you might want to also check the voltage of the Lithium cell and make sure it is at least 3.0V. Anything less and I would replace that battery, which basically only holds the last settings used. No calibration data is backed up by this battery so it can be easily swapped out with a fresh one without loosing any sensitive data. Before you do anything at all get the service manual, and read through it to familiarize yourself with the basics of the scope, and particularly the LV power supply board. https://w140.com/tekwiki/wiki/2247A |
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
Yes, correct, it¡¯s not getting as far as providing the self-test results via the trigger LEDs.
I plan to open it up for the first time and was hoping there was an experienced person who could say that it was likely the XYZ cap¡ Thanks |
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
Chris - Sounds like power supply issues. Suggest checking capacitors on the power supply as well as looking for shorts to ground on the various voltage rails. Some scopes use the various front panel LEDs to provide an error code, but it sounds like you're not even getting that far as you don't have stable power. Dave Casey On Mon, Mar 6, 2023 at 3:28?PM Chris Kniker <chris@...> wrote:
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Re: Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
¿ªÔÆÌåÓýI need to follow this thread.. my 2247A was purchased new by me when they were first introduced and though now surrounded by faster 7000 series, it remains my primary day to day scope. I dread the day it fails to start and run flawlessly.?Jennifer On Mar 6, 2023, at 1:28 PM, Chris Kniker <chris@...> wrote:
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Tek 2247A won't boot up. Relays clicking, push-button LEDs flash, but no display
¿ªÔÆÌåÓý
My 2247A just failed on me and am looking for some initial thoughts on the likely culprit.
After pressing the on/off button, it immediately goes into a repetitive cycle of clicking (like relays turning on) and briefly flashing all the push-button LEDs. The CRT never turns on and doesn't display any diagnostic information, obviously. Before I open the unit up, I'm hoping there's a likely cause for such power-up problems. |
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Re: What to do with 7834 that is missing its CRT?
If you have a 7904 - keep the power supply - check to be sure the are similar, there are differences between 7904 and 7904A. A spare supply is a REALLY good thing to have.
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Cheers! Bruce Quoting "G Hopper, KB7WSD" <kb7wsd@...>: I want to thank everyone for their input.? I posted the following on the "non-2" list and wanted to share it here too. |
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Re: What to do with 7834 that is missing its CRT?
I want to thank everyone for their input.? I posted the following on the "non-2" list and wanted to share it here too.
Replacing the CRT is probably outside of the time and energy I have to devote to the project, and the fact that Dennis Tillman was suggesting parting it out rather than trying to find a CRT really influenced me. That was the direction I had been leaning after talking with Dennis (Tillman), but he had strongly suggested I post and ask on the lists. I've parted out older gear in the past, particularly stuff that was harder to find parts for in Europe. Mostly all HP gear, like 141T SAs, and that generation of stuff since I periodically run across it being thrown away. I have several HP 8660 signal generators that are slowly being disassembled and shipped out, so while not greatly experienced, I've done some. The two things that never seem to go are 1) the transformers, and 2) the CRTs. Besides four other random CRTs, I have four 141T CRTs in boxes that I can't bring myself to dump, but no one ever seems to want to spend the money to ship.... The other challenge is estimating value.? So, with no CRT to hassle with, I'll be all smiles. So, thanks to all for the advice and the private inquiries. I'll dig into it and reply to the couple of private requests shortly. Cheers, Grant |
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Re: What to do with 7834 that is missing its CRT?
The TDS series are already digital 'scopes, the A/D and sampling conversions are already done for you.
Try doing a FPGA analogue vector to raster conversion, that can take 500MHz+ (1GHZ for the 7104 of course) analogue bandwidth AND a fast sweep, I think that would be "pushing the envelope" somewhat, and "less than economical" I suspect. There are loads of other CRT to LCD conversions about, but the vast majority take an already existing video stream (analogue/composite or VGA etc) and put that on display, catering for non-standard scan rates.? Some (for several Marconi instruments) can cater for the Line and Field sweeps that are interchanged.? (The "Line" sweep runs vertically!) In effect, replacing a failing raster scanned CRT monitor (with a fault or "weak" CRT) with a LCD display. The result of those conversions are often stunningly good too. Regards. ??? Dave G8KBV. -- Created on and sent from a Unix like PC running and using free and open source software: |
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Re: What to do with 7834 that is missing its CRT?
OK - I'm nuts - I was thinking CRT. Actually all 3 supplies are interchangable. It is just that some of the ratings or possibly components are slightly different. I have interchanged all these supplies.
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But you are correct as far as the PS part numbers go. Chers! Bruce Quoting Chuck Harris <cfharris@...>: Hi Bruce, |
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Re: What to do with 7834 that is missing its CRT?
Hi Bruce,
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I only know what the parts list in the back of the respective manuals says. And they say the 7934 uses a 620-0823-02 power supply, and the 7904A uses a 620-823-01 or 02 power supply. Remember, that unlike the 7904 all-in-one transformer, the 7904A separates the EHT transformer from the rest of the HV/LV windings. If you want to double check my eyes... always a good idea..., the power supply units are listed in the mechanical parts sections. -Chuck Harris On Sat, 04 Mar 2023 10:24:33 -0700 "Bruce" <bruce@...> wrote:
Chuck, are you sure about the 7934 and 7904A ? One is a standard |
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Re: CRT gain nonlinearity in a tek 556
I would look at the common mode voltages on the deflection plates and the geometry electrodes. I am guessing that they should be around 175V to minimize the fields in the gun structure. The gun components are likely to be 304 or 305 stainless, which can under some conditions at welds or other deformation can become magnetic. I have seen that occasionally, usually causing astigmatism problems. Hugh Gilbert On Sat, Mar 4, 2023 at 4:00?AM ChrisBeee via <chrisbeee=[email protected]> wrote: John, |
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Re: Non-working 475 for shipping cost
¿ªÔÆÌåÓýHi Ed- ? That's fair. Please contact me off list to set things up. ? Thanks- ? Howard ? K3TOA ANATEK Retired From: [email protected]
[mailto:[email protected]] On Behalf Of Ed
Mohrman WA7EM via groups.io
Sent: Saturday, March 04, 2023 12:56 PM To: [email protected]; [email protected] Subject: Re: [TekScopes2] Non-working 475 for shipping cost ? It is in Erie, Co ? UPS extra large flat rate is $26. Add $10 for my work to securely box it and drive it to UPS drop-off point ? Ed ? On Saturday, March 4, 2023 at 12:16:28 PM MST, Leonard OBoyle <tinker43@...> wrote: ? ? where is it ? On Fri, Mar 3, 2023 at 6:44?PM Ed Mohrman WA7EM via <ejmohrman=[email protected]> wrote:
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