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Re: 468 case removal
It may have a springy metal plate inside that earths the case to the ‘scope chassis.
Tim P Sent from Mail ( ) for Windows *From:* v_12eng@... *Sent:* 05 April 2024 00:34 *To:* [email protected] *Subject:* [TekScopes] 468 case removal Hi, I just picked up a 468 and am trying to slide the case off, it has some minor damage but it doesn't appear to interfere with the insides. It binds up "sticks" a little past half way off. Do you have to remove the handle on this model I didn't have to on the other ones I have 466, 475? Is there anything with the digital section in the back that interferer's with the case? Jim O |
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Re: TDS744A tick tick tick when power on (and something smelling)
To check whether its the standby's fault or if its a shutdown due to a shorted cap somewhere I would try to inject the voltages from a regulated supply and see if current is reasonable.
Its helpful to have the nominal current available, but not mandatory. A shorted cap will lead to currents in excess of 1 amp even on very low voltage that won't hurt anything. In case you have a thermal imager you can then see where the current leads to :-) cheers Martin |
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Re: TDS744A tick tick tick when power on (and something smelling)
For troubleshooting of standby power supply part you do not need load, but for power supply as such external loads are needed. Please check Jared’s video I mentioned before, there are all details.
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Vladimir On 5. 4. 2024, at 6:59, Sigur?ur ?sgeirsson via groups.io <siggi@...> wrote: |
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Re: trigger problem with 7B70
On Apr 3, 2024, at 22:05 , Adam R. Maxwell via groups.io <amaxwell@...> wrote:Messing around with this a bit more tonight, I tested both of the 151-0220-00 transistors from the bad 7B70 in my cheapo tester (BSIDE ESR02 Pro). It recognizes both as PNP transistors, one with B=187, Uf=682 mV and the other with B=150, Uf=676 mV. The 7B70 manual (S/N <205000) specifies 151-0220-00 for Q309/Q317, and the Common Design catalog says a 2N3906 is close (fT is 400 MHz for the 151-0220-00, 2N3906 is 250 MHz). I tried stealing a pair of 151-0220-00 transistors from elsewhere on the trigger board (assuming they were fine) for the Q309/Q317 sockets (replacing the donors with 2N3906s), and the bad 7B70 still did not work. I finally realized my good 7B70 has a >205000 serial number, and the manual for that specifies a 151-0271-00 (which explains why the ones that work in both plugins are marked 151271). That transistor has a minimum fT of 2 GHz, and is an AST4261 or 2N4261 in a TO-92 case, so I might be SOL if the bad 7B70 needs those. I assume the (much!) slower transistor worked at some point in the low serial number unit, but Tek must have had a reason for that change. I've grown a bit less optimistic that NOS 151-0220-00 transistors will be the silver bullet, though. Further bulletins as events warrant, etc. Adam |
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Re: TDS744A tick tick tick when power on (and something smelling)
?ann f?s., 5. apr. 2024 kl. 00:19 skrifa?i Staffan <testjarfalla63@...
: In order to troubleshoot, it would be good to disconnect different parts The PSU from my TDS684A didn’t run without a nominal load on the main 5V rail. I don’t remember how much I loaded it, but it couldn’t have been much - probably inside an amp. |
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Re: TDS744A tick tick tick when power on (and something smelling)
Many switching supplies need a minimum load, typically on the 5.0 volt rail (could be different).? Is there anything in the documentation for the scope?
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Harvey On 4/5/2024 12:19 AM, Staffan wrote:
Many thanks for all the pointers! |
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Re: trigger problem with 7B70
Hi Barry, Adam,
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Thank you for the nice words. Your detailed data taking and coming up with good questions were key to fixing the issues and it was fun to spend time on these puzzles. Ozan On Thu, Apr 4, 2024 at 06:43 AM, n4buq wrote:
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Also a bit off topic - capacitor issues
Hi - this relates to strange power supply behaviour of a Mac - iMac 24". It may be relevant to other issues people are encountering.
This computer just had its power supply replaced. Now - provided the mains supply to the computer has been turned off - it will start - and stay on for a time that seems directly related to the amount of time it has been disconnected from the mains. Weird. So, as it's a switching supply - is it possible that we are seeing a strange sort of electrolytic capacitor failure - becoming slowly open circuit with voltage applied, and recovering with no voltage? Has anyone encountered anything like this? Thanks Hugh |
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468 case removal
Hi, I just picked up a 468 and am trying to slide the case off, it has some minor damage but it doesn't appear to interfere with the insides. It binds up "sticks" a little past half way off.
Do you have to remove the handle on this model I didn't have to on the other ones I have 466, 475? Is there anything with the digital section in the back that interferer's with the case? Jim O |
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Re: TDS744A tick tick tick when power on (and something smelling)
You can check excellent Youtube video from Jared (channel NFM) about TDS power supply repair:
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Especially part about standby power, starting around 19. minute. It helped me to repair two TDS7xx scopes what had broken standby power supply. Vladimir Dne 04.04.2024 v 21:46 Sigur?ur ?sgeirsson via groups.io napsal(a): On Thu, Apr 4, 2024 at 3:18?PM Staffan<testjarfalla63@...> wrote:Any suggestions on how to go about in pinpointing the faulty componentI believe these are subject to the capacitor plaque. I'd check to see |
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Re: Help! I bricked a perfectly functioning 2467B!
I am in North Dakota. I am a hobbyist and have two other scopes including a digital scope, so not sure I would be able to justify the cost of a full calibration. I would just like to get the scope functional again. If you know how I can write back the calibration data that I saved, that would be great!
Don |
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Re: TDS744A tick tick tick when power on (and something smelling)
On Thu, Apr 4, 2024 at 3:18?PM Staffan <testjarfalla63@...> wrote:
Any suggestions on how to go about in pinpointing the faulty component I believe these are subject to the capacitor plaque. I'd check to see whether any of the SMD electrolytics have leaked. They're all over, front panel, acquisition board and main board at least. Are schematics available anywhere?See for some. The PSUs on these seem to be all over the place, you might get lucky with the TDS520B component service manual, or there's a TDS520 (IIRC) service manual available from Artek Manuals. H?kan has some schematics on his site too: . |
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Re: TDS744A tick tick tick when power on (and something smelling)
Hi Evan,
The cable looks actually really clean so I doubt that is the cause here. In fact, the complete CRT supply looks really tidy compared to some other instruments I have opened. Very little black powder anywhere really. Regards, Staffan |
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Re: TDS744A tick tick tick when power on (and something smelling)
Hi Staffan,
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Did you check if there is contamination on the CRT flyback cable? Sometimes it can get dirty and arc to the chassis causing a power supply fault. I have never seen this scope but I have seen it happen in others from Tek (and in TV sets of the era). Obviously all normal precautions for working around high voltage apply. -Evan On Thu, Apr 4, 2024 at 7:18?PM Staffan <testjarfalla63@...> wrote:
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TDS744A tick tick tick when power on (and something smelling)
Hello,
Starting my trusty 744A today, it seems to have given up. There is a ticking sound (once every second?) from something likely trying to restart within the power supply? There was a distinct smell, but not as bad as when a cap on the primary has given up. Not wanting to destroy anything else, I disconnected power as fast as I could. Now I have opened the unit down to the power supply. Nothing visible at first sight, but -phew- it doesn't look trivial. Any suggestions on how to go about in pinpointing the faulty component would be very much appreciated. Are schematics available anywhere? Searching the message history I found some discussions regarding the CRT board. There are four transistors on the neck board of the CRT, but none of those is visibly burnt at least. Very much hoping for hints and suggestions! Regards, Staffan |
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Re: 7904A--Horizontal and Power Supply Seem Ok, but Not Much Else
Check if the readout is working at all.
You can do that by probing the X-Y outputs with a scope in xy mode. The text may be upside down, but still you will see the readout. If you get a dot or unreadable gibberish, the readout system is bad or not getting power. Benjamin |
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Re: Help! I bricked a perfectly functioning 2467B!
Don,
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Where are you located? The lab might be able to help in this situation as I can do a full calibration on a 2467B as a last resort I might be able to help run it through a calibration process. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Don via groups.io Sent: Thursday, April 4, 2024 1:20 PM To: [email protected] Subject: [TekScopes] Help! I bricked a perfectly functioning 2467B! Hello all, I had a perfectly functioning 2467B scope (1989 vintage). After reading about possible loss of calibration data due to the NVRAM battery dying, I decided to put in a new battery (mine is the older version, below 50000 serial #) which has the battery separate from the NVRAM. The battery had a date code of 2689, so the battery is 35 years old. I did hook up a backup battery before removing the Lithium battery and confirmed that pin 28 of the RAM chip had at least 3 V on it from the backup battery after removal of the original battery. After putting in the new replacement battery, I also changed out the 4 electrolytic capacitors on the A5 board. When I put the scope back together and fired her up, I got the dreaded " Test 04 Fail 13" message indicating corrupted or lost calibration data. Not sure how this happened since I hooked up a backup battery before removing the original battery. So, the very thing I was hoping to prevent happened by my being proactive! Before doing all this, I had made a copy of the RAM contents by running through the Exercise 02 option, so I have the original calibration data available. My question is: how to write this data to the RAM? (my scope does not have the GPIB option). I look forward to your suggestions and hope to get this fine scope functioning again! |
Benjamin Badrakh
Martin
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