Tektronix 2465B startup error

JVG wrote in news:7f72d417-7e7c-4d2e-95d3- snipped-for-privacy@s12g2000prg.googlegroups.com:

there's an IC called a NVRAM that stores the cal constants,and it fails often enough. you have to re-cal the scope after replacement. I have no idea if there's a modern substitute with a longer life.

--
Jim Yanik
jyanik
at
kua.net

I have very recently repaired my 2465B and successfully replaced the lithium battery with a pair of AA's in a battery holder stuck to the PCB with some double-sided foam adhesive tape. I used decent AA's (Duracell Ultra) in an attempt to reduce risk of leakage.

Recalibration takes quite some time afterwards, so be prepared!

Cheers, Howard

Hello Jim,

Thanks for your answer!

OK, I have found there are still some compatible ICs I can use (as the Dallas DS-1225AB-70)

Now, next problem... calibration. What equipment would I need to do it?

Regards,

JOSE

Hello Howard,

Thanks for your message!

Could you elaborate a bit about that?. Which equipment is needed?. I have a good lab at home but perhaps not for calibration purposes.

Best regards,

JOSE

The cal procedure, including the equipment needed is in the service manual. They discuss the use of a pulse/mark generator, although I used a standard signal generator with a variable duty cycle and a couple of attenuators for

2MHz and less, and an RF sig gen for the small number of higher frequency measurements: maybe not the most accurate, but with careful use you can still do a pretty good cal. The levels were calibrated with another 'scope in circuit.

The service manual is available at

One tiny correction - I actually used AAA's not AA's.

Cheers, Howard

Hi Howard,

Thanks a lot for your detailed message!. Yes, I will look at the Service Manual (had it downloaded but was curious to know if it could be d> The cal procedure, including the equipment needed is in the service manual.

One further question... when scope is uncalibrated, does it show a trace?. On mine, I get only text display with ??? after it.

What I get after the error display and pressing "A/B Trig" is more or less:

Volt/division ????? SEC/DIV ?????

But no trace... is this usual?

Thanks!

JOSE

Losing the trace was exactly what mine did until I replaced the batteries and re-cal'd it.

First check it's triggering - the TRIG'D LED should be on.

Your channel (eg, CH1) should be selected.

Try adjusting INTENSITY and the vertical POSITION for your channel.

If no luck, push the BEAM FIND.

If still no luck, press STEP/AUTO.

Still no luck?

Do a DC balance by pushing the upper and lower input coupling buttons for your channel simultaneously (P4-3 in the operator's manual)., then repeat the above.

I used to have to go through this each time I switched it on before replacing the battery and re-cal'ing.

I still have the ?????? on the lower display I believe because I have not managed to complete the calibration for the option 06 counter timer trigger module I have installed in my 'scope. I have left the 'scope in CAL mode, so that the "?????" become less annoying "......" instead for now until I can figure out the cal procedure for the CT option.

Cheers, Howard

Hello Howard,

Thanks for your interesting message!. I will try that ASAP.

But perhaps I can help you on this:

I had some information stored in my PC for 'future use'... and here is the future :-) !

I hope Jim W8ZR doesn't care for forwarding this information, as he sent it to help other people with similar troubles.

From the TekScopes Yahoogroup:

=================

Gang,

I thought I'd pass on some notes on calibrating my "new" 2465B, which is now freshly aligned and running perfectly. I owe Denis Cobley a huge debt of gratitude for walking me through some stumbling blocks.

Hope these notes can spare some other owners some of the frustration I experienced.

Here is the problem I experienced:

Before calibration, I was getting an ERROR 04 02 message at powerup, signifiying that one or more stored calibration constants was out of spec.

Using a time mark and calibration generator, I stepped throught CAL

01 (horizontal calibration) and CAL 02 (vertical calibration). At a few of the steps, I got a LIMIT error, and had to back up a step and redo it..

After I finished, I powered up the scope but still got the ERROR 04

02 message. I redid the entire calibration, but still couldn't get rid of the error message.

Also, the display showed a row of dots along the bottom line of the readout, where spaces were supposed to be. WHen I moved the calibration jumper back to its normal position, the dots turned into question marks.

Here's what I learned. The service manual doesn't say this, but none of the calibration constants are stored until the entire calibration routine (e.g., CAL 01, CAL 02, etc.) is completed and exited. In other words, if only some of the steps are completed and then the user exits the calibration routine, none of the new constants are saved..

Second, if a LIMIT error is encountered somewhere during the calibration, then the new constants won't be stored. The only solution is to exit the routine and start over.

Finallly (and this is what was causing my problem), there are three undocumented steps in the CAL 01 procedure. The service manual shows

31 steps for CAL 01, but the 2465B actually has 34 steps. After completeing the 31 steps, it is necessary to advance through 32, 33, and 34, and then let the scope exit the routine by itself. If you don't do this, none of the calibration constants will be stored.

After completing the entire calibration in this way, the dots and question marks disappeared, as did the startup error message, and all is as it should be.

Regards,

Jim Garland W8ZR

===============

Thanks again, Jim!

Best regards,

JOSE

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So give the scope and description a place on your "projects webpage". It is a nice 2465B, a good buy for 333 euros. Congratulations!

cu, Andreas

The CT option is tough, you need a pulse generator FG5010 or PG508 you can sync to a time mark generator TG501. I like the FG5010 with the TG501 going into the Trig Gate input with phase lock selected. My FG5010 is not working now but feel free to get in touch with me in a month or so at snipped-for-privacy@gmail.com I am in SE Portland