That is one hell of expensive thermometer , considering how valuable this old gem is for that purpose.
But congrats on proofing it that its still performing very good, a temp reading using a scope.
Thanks for sharing.
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To my simple mind I think this is telling me that the Buffer Board EAROM is defective and after a certain time frame it is dropping data.
In the reading thru the service manual it appears that EXER 02 will read the EAROM data out of both the A5 main board as well as the Buffer Board. Beyond that I'm a little ignorant (and perhaps a little fear of “fail”) as to what I can do with it. I have no experience in dealing with these types of circuits. And I'm not sure if I want to go thru the expense and learning curve to put together an ROM writer and write a new chip. Especially since it appears that this checksum error has no affect on other functions of the scope other than being an annoyance upon power up. So I'm tempted to leave it until it's a total crap out. Which may or may not ever happen. What say the group? Fix it or leave it? I'm open to suggestions.
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Looking further into the 2465B’s abilities, the scope can also function as a time domain reflectometer. For those unfamiliar with this, the scope’s speed is fast enough to measure the transit time of signals traveling through conductors.
For this test, I connected a BNC T to the scope 50 ohm input at channel 1. A 50 ohm cable connected one port of the T, to the 50 ohm output of the SG503 pulse generator.
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To my simple mind I think this is telling me that the Buffer Board EAROM is defective and after a certain time frame it is dropping data.
In the reading thru the service manual it appears that EXER 02 will read the EAROM data out of both the A5 main board as well as the Buffer Board. Beyond that I'm a little ignorant (and perhaps a little fear of “fail”) as to what I can do with it. I have no experience in dealing with these types of circuits. And I'm not sure if I want to go thru the expense and learning curve to put together an ROM writer and write a new chip. Especially since it appears that this checksum error has no affect on other functions of the scope other than being an annoyance upon power up. So I'm tempted to leave it until it's a total crap out. Which may or may not ever happen. What say the group? Fix it or leave it? I'm open to suggestions.
...I also had an intermittent EAROM, but mine was on the main board. The scope would sometimes power up with a checksum error. I don't recall if it was dependent on how long it was off, but it could have been the same issue since data in the EAROM was being written when front panel settings were changed.
Properly done the EAROM should have been replaced, but I was able to change the supply voltage slightly and I got it to work without failure:
https://www.eevblog.com/forum/testgear/tektronix-2445-2465-cal-settings-earom-er1400/msg927144/#msg927144
It may be a long shot, but easy to try. The supply for the buffer board EAROM (signal OEA35) is connected to the one on the main board, so it's the same zener.
EXER02 is harmless. You can use it to make a backup copy of the contents in both EAROMs. Getting the data back in there, however, is another matter. It would have been nice for them to provide a "write" option in the diagnostics.
Mark, first....I want to publicly thank you for the prior assistance you've given me in getting this 2465 fully functional. It is greatly appreciated.
2nd, I saw your post in the other thread concerning lowering the voltage to the EAROM and I did wonder if perhaps it would help with mine. So I did some checking but I found a discrepancy in what you did vs what is currently in place and perhaps your memory of what you did 20 years ago is a little fuzzy.
I looked up A5 Board VR2003 and it's currently a 7.5 V Zener. You indicated that you lowered the voltage by 2 volts by installing a 9.1 V Zener. Isn't that actually RAISING the voltage by approx 2 volts? But you are correct. That line (OEA35) does supply the EAROM's on the both the A5 Board and the Buffer Board.
On VR2003, note that it and CR2004 are used as a dropper from the +42V rail to supply the EAROM. So, the end result to the EAROM is 42V - 9.1V - 0.7V = 32.2V. The spec on the ER1400 says 35V +/- 8%, so the minimum happens to also be 32.2V.
I just verified the voltage on my EAROM (between pins 1 & 2) as 32.3V. With the original 7.5V zener, this would be higher by 1.6V ( = 33.9V).
To use this GBIP board what am I looking for? I could not find a A20 board in the service manual or in the option manual unless I'm totally blind
TIA
Hello,
I have a 2467B that I have a GPIB interface for and I'm kind of stuck.
It came with a A20 Buffer Board (i believe the correct name for it). there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5. there is a 40Pin my Serial Number is B053273.
So I take it this A20 Buffer Board is not compatible with my Serial Number.
Heres a few pics of my A1, A5 and A20 boards.
To use this GBIP board what am I looking for? I could not find a A20 board in the service manual or in the option manual unless I'm totally blind
TIA
Hello,
I have a 2467B that I have a GPIB interface for and I'm kind of stuck.
It came with a A20 Buffer Board (i believe the correct name for it). there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5. there is a 40Pin my Serial Number is B053273.
So I take it this A20 Buffer Board is not compatible with my Serial Number.
Heres a few pics of my A1, A5 and A20 boards.
To use this GBIP board what am I looking for? I could not find a A20 board in the service manual or in the option manual unless I'm totally blind
TIA
Hello,
I have a 2467B that I have a GPIB interface for and I'm kind of stuck.
It came with a A20 Buffer Board (i believe the correct name for it). there are connections labeled C/D/E that I can find on the A1 board to connect to but also on the A20 is a 34pin connection that looks like it would go to the A5 Board but there is no 34 Pin connection available on the A5. there is a 40Pin my Serial Number is B053273.
So I take it this A20 Buffer Board is not compatible with my Serial Number.
Heres a few pics of my A1, A5 and A20 boards.
To use this GBIP board what am I looking for? I could not find a A20 board in the service manual or in the option manual unless I'm totally blind
TIAHere is the interconnect diagram, it shows that there is no longer a buffer board in the 2467B (serials > 50000)
On VR2003, note that it and CR2004 are used as a dropper from the +42V rail to supply the EAROM. So, the end result to the EAROM is 42V - 9.1V - 0.7V = 32.2V. The spec on the ER1400 says 35V +/- 8%, so the minimum happens to also be 32.2V.
I just verified the voltage on my EAROM (between pins 1 & 2) as 32.3V. With the original 7.5V zener, this would be higher by 1.6V ( = 33.9V).
D'OH . You are absolutely correct. It's a dropper circuit from the +42V supply. I think I have a 9.1V Zener in my pile of parts. If not it will be on my next parts order. Gonna give it try and see what happens.