HP 54601A Scope - Help needed

[Firebird00]

Hi all.
I'm trying to repair my old scope 54601A that had lost his calibration when the nvram was gone.
Some says the nvram don't store calibration data, others say yes, I don't know, but the case is that mine was working fine the same day the nvram was gone, and after that it never worked again. Always I get the message "No signal found" on the screen when I put a signal in any channel, no matter what kind of signal, I get the same message in  all 4 channels . If I use "manual" controls instead of Autoset I get the same message. Played with all options in the Trigger menu makes no difference.
I can see the signal on the screen but he don't wants to trigger, of course, it doesn't detect signal to trigger, right?
Revised all the soldering points on the new (socketed) nvram, voltajes and tracing the signal until arrives to digital components that I don't understand, all ok.
Do the Vertical Self calibration with failed in Hysteresis point, aborting the calibration process, so the scope still uncalibrated. I don't think I'm doing anything incorrect in the calibration process, I change the input channel cable  when the software asks to do. I'm using a regular 50 ohms cable with bnc in each end, and not using the probes, the bnc goes directly to input channel.
I'm asking to somebody that have the same scope, a copy (Dump) HEX or BIN file of the nvram so I can write it on mine and see what happens, at least it will be a good starting point. I spent too much hours trying to find something bad when maybe the only problem is this software.
Any help will be much appreciated.

[singapol]

It's best to download service manual to read and find out what to do. The scope software tried to read nvram
but failed hence the error message. The nvram internal battery is dead. You need a new nvram with your original data programmed into it or another hex file. There are people who did open nvram to replace battery,
it's not easy and I don't recommend to try. Maybe someone with a programmer can help you but you must first get new nvram with working battery (that is date code which is still working). Best of luck.

[Firebird00]

Singapol, I think you miss that I said before
"Revised all the soldering points on the new (socketed) nvram"
The scope have a new and fresh nvram, waiting for a software donation...

Thanks anyway...

[Dtec]

The new nvram needs to be downloaded upon powering up hold any front panel button in and press power this will recognize the new nvram chip then you may calibrate it

[Dtec]

It actually flashes the nvram so it will work with scope

[Dtec]

While you were in there replace the 10 uf 16 DVC vertical capacitor it will eventually go bad and cause short vertical I replace the electrolytic with a dipped tantalum

[Firebird00]

The new nvram needs to be downloaded upon powering up hold any front panel button in and press power this will recognize the new nvram chip then you may calibrate it

Yes, I do that maybe 15 times, and the problema still there.
Each time I do that, was pressing different key, not the same, but I don't know if I have to press one concrete key, or two or a sequence of keys, do you know?

[Firebird00]

I've been read on Internet that this IC have something like a "internal battery locked", to prevent discharge when it will be in stock in any place for some time (years?)
Once the IC is installed on the device (scope in that case), the first time the IC receives voltaje from the PS (power on), then the battery goes "unlocked" and supply voltage to the internal IC to maintain the configuration when the scope powers off. At this moment the IC have about 9 years of live, depending of the quality of the internal battery.
Am I wrong?

[Firebird00]

While you were in there replace the 10 uf 16 DVC vertical capacitor it will eventually go bad and cause short vertical I replace the electrolytic with a dipped tantalum

That was the first thing I do when buy this scope, because this cap was dead, and the image "stretched?"

Thank you 

[DimitriP]

I don't know the difference between the 54501 and the 54601, but here is the
501 version of NVRAM replacement:
 

[Firebird00]

This one is too different than 54601a, also in the Caibration process there's only a few similar procedures.
I think that the metod of pressing any key and power on to call default values doesn't work on 54601A, because when I do that on mine, it simply shows on the screen the message "Key pressed" with a value in Hexadecimal, no more than this.
Thank you

[Dtec]

I have the manual I'll send the page Saturday am the service manual is downloadable from single to website it's a546xx covers 54601, 602,600

[Dtec]

Did you try to load calibration defaults?

From the HP Service manual:

1. Check the rear panel DC CALIBRATOR output level.
If you are not sure how to check the DC CALIBRATOR, see "To check the output of the DC CALIBRATOR," on page 4–6.

2. Load the default calibration factors.
a. Set the rear-panel CALIBRATION switch to UNPROTECTED (up position).
b. PressPrint/Utility , then press the Self Cal Menu softkey.
c. Press the Load Defaults softkey.

Manual available here:
http://www.cube.co.za/~tva/workbench/hp54602b/HP-54602B-Oscilloscope.pdf

It covers the series.

[Dtec]

Found on the blog

[Firebird00]

Yes, I did it, a lot of times.

The thing is I can see the waverform on the screen, but can not trigger that signal. Using the Autoset key nothing changes, always the scope says "No signal found".
I think that's why it fails on the calibration procedure, Trigger Hysteresis step Failed, because in some point no signal is detected.

I will burn a image file containing calibration information from a (same) working scope to mine and see what  happens. Maybe when the battery of the nvram died, the calibration data also died.
Will try and see...

[Dtec]

Found on the blog

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[Dtec]

The default calibration is on an eeprom you may have a bad new nvram did you buy it on eBay what is date code it's right on chip I just bought ten from maxim for the 54501 it has a 2016 code date on all of them


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[Dtec]

You are correct but if you bought an old chip or a defective one that is you're problem what is code date on chip


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[Dtec]

You calibrate and then turn switch back to protected or it won't work


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[JacquesBBB]

If you still have the old NVRAM chip,  you  can try to hack it to replace the battery.
It is  delicate, but not  difficult.

https://www.eevblog.com/forum/repair/hp-54601a-failed-checksum-test/msg548141/#msg548141

As I understand,  your DS1220 is on a socket, so  it will be easy to test.

I had no time on my side to do any experiment this week end on this, sorry.

[Dtec]

Also it is soldered on top and bottom of board if solder did not flow thru hole to top you may have an incomplete connection


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