NOS Tektronix 2465? - Page 1
Forum section: electronics / beginners

author: Grateful6595
author_rank: Newbie
timestamp: November 30, 2016, 04:44:55 am
content: Hello. I'm just getting back into electronics. I have been purchasing equipment I need and/or think I'll need. I recently bought a Tek 2465 (the 300 MHz one). As I'm planning to work on audio equipment this seemed to be way more than I would need in a scope, but it allowed for growth should I need a faster scope. I'd been reading the 2465 threads as a guest and decided to open my scope to see if I should address the more common problems that the 2465 exhibits. I found pure bliss. I do not think this scope has ever been used. No dirt or lint of any kind, no cap leakage, no heat marks....everything looks brand new. My first question is; Should I even think of replacing components because of age but no use? The second is; Is this scope worth a ton of money to a collector? I can't believe it but it seems to be NOS.Any input will be appreciated. Thanks.

author: tggzzz
author_rank: Super Contributor
timestamp: November 30, 2016, 09:22:11 am
content: Make sure you check the "mains" capacitors before they rupture, carbon film gets deposited everywhere and prepreg on the PCB is removed. To be more precise, in my case it was the series resistor that detonated, leaving a 1cm patch on the PCB.There's a thread somewhere on this forum, but seehttp://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdfOn my 2445B those caps were cracked, so I replaced them before they detonated.

author: w2aew
author_rank: Super Contributor
timestamp: November 30, 2016, 03:48:11 pm
content: Quote from: Grateful6595 on November 30, 2016, 04:44:55 amIf you want to check how much the scope has been used, you can run the Diagnostic Exerciser EXER 05. It will tell you the total operating time and the power cycle count. Here's how you run this:Press and hold the delta-V and delta-t buttons, then press Trigger SLOPE (while still holding down delta-V and delta-t). Release all buttons. Then press the upper/lower Trigger MODE buttons until EXER 05 is selected. Then press the upper Trigger COUPLING button to run EXER 05. You can exit the exerciser with the lower Trigger COUPLING button and return to normal scope operation with the A/B TRIG button.

author: tggzzz
author_rank: Super Contributor
timestamp: November 30, 2016, 04:58:30 pm
content: Quote from: w2aew on November 30, 2016, 03:48:11 pmThat works on my 2445B, but not on my 2465 which only has exercises 1 to 4.

author: David Hess
author_rank: Super Contributor
timestamp: December 04, 2016, 02:11:44 am
content: Quote from: tggzzz on November 30, 2016, 04:58:30 pmThat is not surprising since the hour counter on a 2465 would need to be written periodically into EAROM (sort of like EEPROM) instead of the non-volitile SRAM used on a later model.

author: tggzzz
author_rank: Super Contributor
timestamp: December 04, 2016, 11:09:58 am
content: Quote from: David Hess on December 04, 2016, 02:11:44 amBut where is the "current config" stored so that it can be restored after the next powerup? I presume the EAROM, in which case there's no fundamental reason why the hours couldn't also be stored.More interestingly, is it possible to prolong the life of the EAROM by preventing such retention of the current config?

author: David Hess
author_rank: Super Contributor
timestamp: December 04, 2016, 03:04:25 pm
content: Quote from: tggzzz on December 04, 2016, 11:09:58 amIt has to be stored in the EAROM but is the front panel configuration stored when it is changed or only when power is lost? I only have the later oscilloscopes in the 24xx series which use nonvolatile SRAM so they do not have this issue under any condition.If the front panel settings are stored at power down, and there is a line up signal to support this, then Tektronix could have updated the time counter at that point. So why didn't they?Maybe Tektronix did not think of it. Did the 2430 which came out 2 years later and uses nonvolatile SRAM implement an hour counter? I could not find it in the manuals.

author: tggzzz
author_rank: Super Contributor
timestamp: December 04, 2016, 04:23:38 pm
content: Quote from: David Hess on December 04, 2016, 03:04:25 pmAll very sane.Looking at a 2465 service manual indicatespower down causes a non-maskable interrupt, but there's it is ambiguous as to whether anything is stored at that time. The NMI processing "begins shutting down the instrument in an orderly fashion", "places the EAROM in standby to prevent loss of data", and "disconnects the input 50ohm resistors"all EAROM signals, including the clock, are generated under software control. That sets limits on their timing, so I think they could be emulated by any small modern MCU with sufficient I/O pins.I guesstimate each bit twiddle will take ~1us, writing one data location consists of 34 bits (20 address, 14 data), and therefore ~80 bit twiddles when the clocking is included. The address space is only 100 locations and the number used isn't clear. However, that tends to imply a total write time of around 80us*100=>8ms. That's not short, but not out of line with how long the PSU can be expected to hold up the 5V line.All guesses are subject to checking with a logic analyser. I'm not going to bother to do that until after the EAROM has failed.However, I will take a precautionary video of the display showing the EAROM's contents, in case it later fails. (Video because it is easier to shoot/store than many stills, and I can leave transcription until after a failure occurs).

author: MarkL
author_rank: Unknown
timestamp: December 04, 2016, 05:49:18 pm
content: The 2465 stores front panel settings after 10 seconds of no changes to any settings. And the 10 second timer only starts when changes occur to settings that are solely tracked by the processor, such as the cursor push buttons. Changes to hard switches, such as horizontal sweep, do not trigger the timer since they can be read again on boot.So, for example, if you turn on cursors and turn the unit off within 10 seconds, it will not remember that you had cursors on.As tggzzz mentions, I would also recommend archiving the EAROM contents with a short video (service menu EXER 02).As for capacitors, the 2465(plain) does not have a chronic history of issues like the A and B series. The mains caps would be good to check, but I wouldn't mess with any others if the scope is working. If you feel like double-checking, you could check the voltage and ripple of the supplies as described in the service manual. And since the scope is working, you can even use it on itself to do this check.