Author Topic: Fluke 5440A repair  (Read 5255 times)

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Offline MegaVolt

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Fluke 5440A repair
« on: July 06, 2021, 08:35:12 am »
I received a Fluke 5440A in excellent condition with a small error. I thought it would be easy. But I checked everything I could and I don't see a problem: (I will accept any hints :)

This is what I see. When turned on, all the dots on the screen light up except for one position where the "?" This is problem?

Then I see an inscription (DV instead of DC)
5440A DV CALIBRATOR
FRONT PANEL RUNNING

And after the error "FRONT COMMUNIC FAULT"

In the service manual, this is error 64. Loss of communication between A2 and A16. But I switched the device to test mode and with the oscilloscope I see an exchange between these two boards in both directions. Signals are similar to RS232. This means that the UART is working, the processors are working, the communication line and buffers are working. I checked the frequencies they are normal.

What else can you check ??

Firmware except MC68701 I could not read it.
 

Offline picburner

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Re: Fluke 5440A repair
« Reply #1 on: July 06, 2021, 02:28:35 pm »
The first thing to check is if all the voltages are right and if the ripple of each is within the tolerances shown in the service manual.
A strong ripple on 5VDC could disturb the communications between the main cpu and the front panel as well as create other anomalies.
I have a 5440B which differs in the display (VFD vs LCD) and other little things.
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #2 on: July 06, 2021, 02:38:17 pm »
The first thing to check is if all the voltages

Thanks for your participation.

I have checked the voltages related to the processor boards. Everything is fine. The connection is made by differential signals of 5V swing each. This is a very reliable communication channel :))

But I didn't check the rest of the voltages. Perhaps it makes sense to do everything.

I thought that someone has information on how the ping is done. Or perhaps it has waveforms.
 

Offline TiN

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Re: Fluke 5440A repair
« Reply #3 on: July 06, 2021, 02:59:28 pm »
Check for life on main processorboard, check reset lines, check XO outputs, check if firmware chips on all digitaly boards is good or not.  :)
YouTube | Metrology IRC Chat room | Let's share T&M documentation? Upload! No upload limits for firmwares, photos, files.
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #4 on: July 06, 2021, 03:18:35 pm »
Check for life on main processorboard, check reset lines, check XO outputs, check if firmware chips on all digitaly boards is good or not.  :)
Thank you Ilya for your participation :)

1. The files that I posted are read from the current boards. Unfortunately, I cannot find out how much the correct firmware is in them.
2. Processors work and send information via UART. This means that some of the firmware, reset, and generator are working.

I see that the boards are working, displaying information on the screen and trying to communicate with each other. But something is not going quite the way it should be.

Perhaps the firmware began to be erased and a couple of bits changed their meaning: (((I'm trying to find another firmware to compare. But it's difficult :( I found only one person on the Internet with a similar device :(
 

Offline picburner

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Re: Fluke 5440A repair
« Reply #5 on: July 06, 2021, 03:44:30 pm »
The communication from A16 and A2A1front panel is by RS-422 data link @ 65KBaud.
The firmware on eproms (on A16) is protected by checksum, if it starts to lose bits it should make an error during boot.
At least this is written in the 5440A service manual.
 
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Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #6 on: July 06, 2021, 04:59:08 pm »
At least this is written in the 5440A service manual.
Thank you for this valuable information.  You can share the service manual for model "A".  I didn't find it.  there is only for "B".
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #7 on: July 06, 2021, 09:53:37 pm »
https://youtu.be/RgqR6af6lQc

Added a video in which the LEDs are visible.  It looks like the code is fine.  But there is a constant restart and there is an FPC error.  The LEDs in the distance are 4 diagnostic LEDs.  LED near it is Fault.
« Last Edit: July 06, 2021, 09:58:09 pm by MegaVolt »
 

Offline picburner

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Re: Fluke 5440A repair
« Reply #8 on: July 07, 2021, 03:50:34 am »
Yes, there is a fault: the four LEDs must all turn off to successfully complete the test (and remain off...).
I got this service manual here
 
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Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #9 on: July 11, 2021, 01:56:48 pm »
Maybe someone has copies of memory chips from 5440A?
 

Offline velik_kazakov

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Re: Fluke 5440A repair
« Reply #10 on: July 12, 2021, 07:44:41 am »
Maybe someone has copies of memory chips from 5440A?

Hi, I get your post. I send it (not sure that all is is the zip, but front controller is in).
Sorry for my bad English!
 
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Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #11 on: July 12, 2021, 07:51:44 am »
Hi, I get your post. I send it (not sure that all is is the zip, but front controller is in).

Thank you so much! This is a big relief :)
100% match :)))

I have to start thinking differently to understand the cause of this error.

I can definitely see the byte coming to the front panel and see the panel's response back. These transfers follow periodically.

Studying the A16 is difficult until I have extension cables (on the way).
 

Offline velik_kazakov

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Re: Fluke 5440A repair
« Reply #12 on: July 12, 2021, 08:50:39 am »
The symbols on the LCD is generated from decoder and ROM. I don't remember now , but if I find some time in next days will check the schematic. Maybe you can to find the error on the decoder for this symbol. Just that is in my memories. Because my LCD is brockena and some symbols looks not good, I think to exchange it with LED dysplays. Get the dysplays but no time for that. But I remember that the schematic is very interesting for symbol generator for LCD.
Sorry for my bad English!
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #13 on: July 12, 2021, 08:58:08 am »
The symbols on the LCD is generated from decoder and ROM. I don't remember now , but if I find some time in next days will check the schematic. Maybe you can to find the error on the decoder for this symbol. Just that is in my memories. Because my LCD is brockena and some symbols looks not good, I think to exchange it with LED dysplays. Get the dysplays but no time for that. But I remember that the schematic is very interesting for symbol generator for LCD.
From what I see in the diagram from version "B", the ROM in front of the screen is simply transcoding. It works only towards the side of the screen and has no feedbacks. Those. error in something else.

I have an exchange problem between A2 and A16
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #14 on: July 28, 2021, 03:23:36 pm »
I found a problem IC :)) This is UART 6402 on the boards A16 and A14.
The complexity was that the chips worked and transmitted data. But not all bits. Part of the bit`s lost somewhere inside the chip. We send 5 accept 1 :)))
I managed to find new at $ 0.25 per piece :))

Now I see a power error. Further is easier :)))

I can tell a little about the exchange check cycle between A16 and A2.

1. A16 sends 0x05 with some period until A2 respond.
2. A2 replies 0x15

I will pay attention to what these two numbers coincide with the fact that they transmit these boards if the switches select testing mode.

Then goes an active exchange. See images.
« Last Edit: July 29, 2021, 08:16:03 am by MegaVolt »
 

Offline Dr. Frank

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Re: Fluke 5440A repair
« Reply #15 on: July 28, 2021, 07:04:14 pm »
Hello,

I've never seen a 5440 with an LCD, so I assumed it was always a VFD.
Are both displays LCDs?
Is this a late modification by FLUKE?
What's the vintage / datecode?
Does anybody have schematics for this change?

How does the front panel look like, as the green filter foil will be changed to something else?

Frank
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #16 on: July 28, 2021, 08:00:48 pm »
I've never seen a 5440 with an LCD, so I assumed it was always a VFD.
Are both displays LCDs?
Is this a late modification by FLUKE?
What's the vintage / datecode?
Yes, it has two LCD displays.  This is the very first 5440 with the letter "A".  Based on the date code on the IC, it was produced in the year 83.  I have inserted a video of the same device from velik_kazakov.
https://youtu.be/yJfPx0z0a78
Quote
Does anybody have schematics for this change?
The service manual is sold at this address.  http://artekmanuals.com/manuals/other-manuals/
 I am using instructions from 5442A / 5440B and there are differences only on the A2 board.  The rest of the scheme is completely identical.

I can take any photos you are interested in.
 
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Offline Dr. Frank

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Re: Fluke 5440A repair
« Reply #17 on: July 28, 2021, 08:21:52 pm »
Thank you very much, that's enough of information.
So it's the other way round, that they changed to VFD later.
Frank
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #18 on: July 28, 2021, 08:37:51 pm »
Data file with protocol between A16 and A2.
 
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Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #19 on: July 31, 2021, 01:36:33 pm »
The two Vishay resistors on the A10 board have changed the resistance a lot.  One for 10% and the second for 40%.  As a result, the + 17V power supply was about + 21V.  Replaced with new ones the error has disappeared.  Now the next error :))))

I also found that the A9 board has a date of 88.  It looks like it was replaced later.
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #20 on: July 31, 2021, 01:40:14 pm »
I just noticed that the error remained the same.  But the LED indicating the error went out.  I don't seem to notice something.
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #21 on: August 01, 2021, 01:43:26 pm »
The LCD panel seems to be dead :(. It's very sad. I don't know how to replace it :(
 

Offline Kleinstein

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Re: Fluke 5440A repair
« Reply #22 on: August 01, 2021, 03:44:54 pm »
A point where those LCDs may fail is with the contacts from the PCB to the glass (zebra strips or gules contacts). There is also a chance a driver chip lew and this may over a long time damage the LCD (e.g. with DC to the display).  Is this actually an LCD or maybe LEDs ?.
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #23 on: August 01, 2021, 05:14:40 pm »
There is also a chance a driver chip lew and this may over a long time damage the LCD (e.g. with DC to the display).
The display is almost black and this indicates that the screen itself is damaged.  The electronics are most likely damaged as well.  But it doesn't matter anymore.
Quote
Is this actually an LCD or maybe LEDs ?.
No doubt this is an LCD screen.  I specifically shot so that the characteristic tracks to the segments were visible.  Also in the video above you can see the same screen in operation.  There he is also in poor condition, but still shows a couple of digits.
 

Offline MegaVolt

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Re: Fluke 5440A repair
« Reply #24 on: August 01, 2021, 05:23:29 pm »
I was able to start the device without errors by pressing the reset key on the front panel.  It looks like there are some problems with the initial launch.  I'll deal with this later.

 The digital test is successful. 

The analog test stops with an error. 

The high voltage test causes a sound of electrical breakdown and the device freezes :((  I have not yet found a place with traces of discharges ...

To be continued :)
 


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