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Just got a Tek 2465A, couple questions (how I screwed the calibration data)!!

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alpher:

--- Quote from: MarkL on April 03, 2018, 07:56:01 pm ---
--- Quote from: alpher on April 03, 2018, 12:41:20 am ---...
Pin 12 of U2310 goes up to ~ 1V, looks like something is pulling it down?
...

--- End quote ---
Just on this one point, that's odd because U2310 is an LS174 6-bit latch and pin 12 is one of the totem-pole outputs.  If it's not pulsing, it should be nailed to a low or high and not something in between (like 1V).

The only thing I can think of at the moment is if you had the unit in diag mode when you made the measurement.  The diag jumper removes power from U2310 (and U2350 and U2450).  If that's the case I could imagine pin 12 might have settled at some strange level.

--- End quote ---

Wow, that's some detailed info about the memory operation, really impresive. :-+ :-+
Wonder how did you get the PAL info (can you actually read it from the chip) , I've allways thought that they are protected from reading after being burned?

Any way this is how I tried your code on my scope, as you can see there's a mini grabber connected to pin 12 of U2310.
At the back you can see the side of my rigol, unless I made some grave error setting up that scope (I must admit i's possible since I just got it and still learning how to use, but not likely) there was no pulse recorded on it even once.



On a different topic, here's a page from options service manual regarding calibrating CTT:



Do I read it correctly that this setup of 2 generators will produce what is essentialy 1MHz square wave 1V?
I'm I wrong here?
I must be. :-//

Here's a copy of the options service manual, it does have diagnostic error test 81  error 01 and 02 only listed.

https://drive.google.com/open?id=1XyZqO2u1x5B9Le-zL154XTEcoKKDVG4-

MarkL:

--- Quote from: alpher on April 03, 2018, 08:48:39 pm ---...
Wow, that's some detailed info about the memory operation, really impresive. :-+ :-+
Wonder how did you get the PAL info (can you actually read it from the chip) , I've allways thought that they are protected from reading after being burned?

--- End quote ---
Yeah that was actually interesting.  I never decoded a PAL by hand before.  I got the JEDEC file from here:

  ftp://ftp.bluefeathertech.com/electronics/testgear/Tektronix/firmware/24x5/2465A-B/2465A.zip

No idea where they got it, but it seems to be right.  Only afterwards did I notice they also had the equation file, which would have saved me some time.

This PAL is pretty old and the datasheet doesn't mention any protection mechanism.  Then again, the whole "how to program this thing" is also not in the datahseet.  Who knows.


--- Quote ---Any way this is how I tried your code on my scope, as you can see there's a mini grabber connected to pin 12 of U2310.
At the back you can see the side of my rigol, unless I made some grave error setting up that scope (I must admit i's possible since I just got it and still learning how to use, but not likely) there was no pulse recorded on it even once.

--- End quote ---
It's hard to tell, but it looks like the probe might be on pin 13?  The PAGE signal is also on pin 1 of both EPROMs, so I probably should have pointed to that as an easier place to look for it.  But even if it was pin 13, it still should not have been 1V.  It would have been good TTL logic levels and there would have been pulsing as the program ran.

If you probe it now with the scope running it will have random looking pulses on it.


--- Quote ---On a different topic, here's a page from options service manual regarding calibrating CTT:
...
Do I read it correctly that this setup of 2 generators will produce what is essentialy 1MHz square wave 1V?
I'm I wrong here?
I must be. :-//

--- End quote ---
You're right.

The pulse generator can produce a 50% duty cycle at 1V pk-pk into 50ohms, but it's not very accurate.  So they use the time-mark generator as a stable time reference to drive the pulse generator.  What you get is a 1MHz ~50% duty cycle square wave that has an accurate frequency.  If you have an accurate 1MHz square wave generator that can do 1V pk-pk into 50ohms, you can use that.


--- Quote ---Here's a copy of the options service manual, it does have diagnostic error test 81  error 01 and 02 only listed.

--- End quote ---
Yep.  Same one I have.

We're assuming the 81 03 error has something to do with calibration.

MarkL:
If it's any consolation, the service flowchart in the back says if there's any CTT error 81, the next step is to re-cal the CTT (PDF page 305).

alpher:


That's all I have, worth a try?  :-DD :-DD

alpher:
Guess what, as incredible as it sounds, it worked!!! :-+ :-+
Here's the setup:




I just passed the signal through Rigol using it as a basicly frequency counter.
My cheeapass analog function generator turned out to be quite stable,  :-DD
Had to run the rutine a couple of times but as soon I went with the frequency a touch under 1MHz, bam! passed.
Scope boots without any errors now:

https://youtu.be/HCpPTXSqk0I

I realize that it should be calibrated anyway, but I guess have to wait till I get my hands on something slightly better than my FG8002.  :-DD :-DD


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