Fluke 5440A repair

[Rax]

If you had a logic analyzer, you could stand on the display board and track the writing on the letter bus to the display.

Funny you should mention that, I do... Sort of. I have an 8 CH Saleae (I think?...) 24MHz USB logic analyzer. Not sure how many channels I need, or if this is anywhere near up to par. But I'm definitely willing to find out.
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Well, the POS doesn't work. I got it a couple of years ago and I don't think I ever used it.

Just picked up a Hantek 6022BL which I should receive tomorrow. Would this fit the bill?

[MegaVolt]

Funny you should mention that, I do... Sort of. I have an 8 CH Saleae (I think?...) 24MHz USB logic analyzer. Not sure how many channels I need, or if this is anywhere near up to par. But I'm definitely willing to find out.

You need 7 channels.
1. Letter writing signal. There is a small circle in the picture. Unfortunately I don't have a schematic for this board and you'll have to do a bit of research to find it. Address for accessing the display A15...A11 = 11111. When setting this address and the WR signal, you should see a signal at the output.
Display_2_WR  =  [A15...A11 = 11111]   +   [nMREQ_Z80=0]   +   [nFRSH_Z80=0] + [nWR_Z80=0]

2. Data bus D0...D5.

If 0x20 is added to the data, then the letter codes will correspond to ASCII codes.

[Rax]

Repair is probably going to be a challenge.  But that's what you're after, right?

yes, and you well know it

[Rax]

Does anyone have any info on the extender cards needed for this? I can't find anything in the SM, but maybe I'm missing it. I'm not even sure if there's one type for servicing the entire unit.
I think I'll have to raise the controller to pursue some troubleshooting steps from the SM (4-28 @ p. 4-31).
Thank you.

[bdunham7]

You might try asking ebay seller Sparko0679.

https://www.ebay.com/sch/i.html?_ssn=sparko6079&store_name=sparko6079&_oac=1&_trksid=p2047675.m3561.l2562

[Tony_G]

I have several of his extenders - They work very well and he'll work with you to create a new one (He did his 8340 & 5200 extenders because we asked).

Also did some extenders for 8350 plug-ins from PCBWay and they were great too - If the extender is just a passthrough, then don't let the lack of original pieces stop you - If they have additional bits on them (I think the 8902A micro board extender has things like this) then you might just have to go with a passthrough and a logic analyzer.

TonyG

[Rax]

You might try asking ebay seller Sparko0679.

The interactions I had with him make me not want to touch his business with a ten foot pole, frankly. Besides, these are machined, or routed PCBs, so not precise and rely on a good hand when made, etc. Due to the fabrication process, the reviews I heard from other people have been at best mixed - there's inherent tolerances I'd rather... not. One puts their equipment at risk when using them, in my opinion.

I am hoping to find a genuine extender or just fabricated better.

[Rax]

Still looking for any info on these extenders. I haven't been able to even find part numbers, or pictures, or really anything.

If anyone has any information, I'd appreciate sharing it. Thank you.

[Tony_G]

The connectors are just standard (for the time) Cinch connectors - You can buy modern equivalents from Newark (and probably others).

Grab KiCAD and create a simple board that passes from an edge connector to whatever you get from Newark. That is what I did for the 8350 plugins. Cost me US$5 for the boards - Would be more for the 5440 as it seems to double up those connectors.

Regarding the actual part numbers, according to the publicly available service manual, the complete extender kit seems to have the part number Y5021 - The extender board has the part number 608281 - The filter extender has the part number 608117.

TonyG

[Rax]

Regarding the actual part numbers, according to the publicly available service manual
TonyG

Thank you very much, Tony! I really appreciate it. I couldn't find it in there if my life depended on it.

[Rax]

Grab KiCAD and create a simple board that passes from an edge connector to whatever you get from Newark. That is what I did for the 8350 plugins. Cost me US$5 for the boards - Would be more for the 5440 as it seems to double up those connectors.

That's not a bad idea at all. I can't imagine finding the time with all projects, but it'd be a very useful contribution if no one else has done it already.

[Rax]

You need 7 channels.
1. Letter writing signal. There is a small circle in the picture. Unfortunately I don't have a schematic for this board and you'll have to do a bit of research to find it. Address for accessing the display A15...A11 = 11111. When setting this address and the WR signal, you should see a signal at the output.
Display_2_WR  =  [A15...A11 = 11111]   +   [nMREQ_Z80=0]   +   [nFRSH_Z80=0] + [nWR_Z80=0]

2. Data bus D0...D5.

If 0x20 is added to the data, then the letter codes will correspond to ASCII codes.

Thank you for that, Megavolt. I'll likely try to read these data lines over the weekend, if I'm very lucky (timewise). I'm not sure I can probe all that without extenders, but I'll look into it. This is "path A."

That said, I'm trying to take a bit of a step back and figure out what exactly is my best next step here. You've previously mentioned pulling a bunch of cards and then - if I understand your approach correctly - putting them back in one by one? While watching how the trouble LEDs on the controller card act? (in other words, see which card triggers error codes) Is this what you had in mind with that? This is path "B."

So I have the following steps forward, in no particular order (as, to be honest, I'm not sure at all what to do next):

• step C - follow the procedure in the SM (p.4-31). This should, in theory, allow me to isolate the issue(s?) to the controller vs. the front panel.
• step A
• step B

Thanks in advance for any "birdseye view" guiding thoughts.

[MegaVolt]

You've previously mentioned pulling a bunch of cards and then - if I understand your approach correctly - putting them back in one by one? While watching how the trouble LEDs on the controller card act? (in other words, see which card triggers error codes) Is this what you had in mind with that? This is path "B."

Unfortunately, this is part of path A - the launch of the digital part of the device. Further tuning uses a rich set of self-test tools for the instrument itself. And for this you need to be able to read messages from the display. You do not have to make an insert board, you can solder the wires to the desired points and bring them up.

Connectors with a pitch of 3.81mm, I could not find. Be careful the internet is full of 3.96mm ones that don't fit.

[MegaVolt]

P.S. To access the above contacts, you do not need a debug board. They are located on the A2 board, which is accessible by removing the front panel.

[MegaVolt]

You can buy modern equivalents from Newark (and probably others).

Do you know the name?

[Rax]

You can buy modern equivalents from Newark (and probably others).

Do you know the name?

I'd also appreciate more specific information - part number, possibly link to one... Thanks much in advance.

[Rax]

The connectors are just standard (for the time) Cinch connectors - You can buy modern equivalents from Newark (and probably others).

I don't see any card edge connectors at Newark in the US with 3.81mm pitch, only 3.96mm. I am looking at other suppliers, but if I recall correctly, I ran into the same problem when trying to build extenders for some HP equipment.

[MegaVolt]

The part that is in the device itself has the TE Connectivity number 2-583407-0. Perhaps you can buy them.

I looked at the pci connector, they have a 1.27mm pitch. Those three pins per pin of the original connector. If you leave two out of three, you get a pretty good connector. Like this: 00_00_00_00_

[Rax]

P.S. To access the above contacts, you do not need a debug board. They are located on the A2 board, which is accessible by removing the front panel.

Here's how I set this up last night. This should allow access to the boards (at least for pulling) and the front panel too.

[MegaVolt]

Here's how I set this up last night. This should allow access to the boards (at least for pulling) and the front panel too.

You can disable the keyboard. This will add space.

[Tony_G]

I don't see any card edge connectors at Newark in the US with 3.81mm pitch, only 3.96mm. I am looking at other suppliers, but if I recall correctly, I ran into the same problem when trying to build extenders for some HP equipment.

Just looked at the part and yes you're right - While they are Cinch connectors, the specific part is a 0.150/3.81mm spacing - For all of the HP gear I have, I used 0.100/2.54 spacing connectors which I have bought from Newark.

No idea where you would get these ones - You might want to try reaching out to Fluke and asking - They might have a current part number for the connectors.

TonyG

[Rax]

You can disable the keyboard. This will add space.

As I'm further taking this apart, I am concerned about this ribbon cable in a sleeve which seems stressed the way I have this setup currently (see pic). Do I need to sit this to work on differently? Am I putting that cable under too much duress?

Edit: the way the forum mangles pictures in what seem like a capricious, random manner, no one'd be able to tell what they're looking at. The pic is upside down. So the ribbon in the black sleeve, even if the unit stands on the side railings on this bench I have it on, is a bit pressed under the unit.

[MegaVolt]

The black cable is the connection between the front panel and the A16.  It's just a flat cable.  Black insulation is protection against breakdown of high voltage that is in the device.  It shouldn't be damaged.

[Rax]

I've taken a bit of a step back and looked at the other threads on this unit and sim. It seems I also am looking at some trouble on A19, though different than essele. I see higher than expected voltages on the unregulated rails on there:

• TP1: +39V
• TP3: -40.5V
• TP4: +9.4V
• TP5: +9.9V

I'll take the board off and look for trouble, probably recap it and get some ballsy diodes in there to allow for lower/easier dissipation, but I'm a bit unsure how unregulated supplies can be this much off. For reference, I'm measuring this with my Fluke 189.

Any recommendations on what type of diodes to use? I should have some either Schottky or soft recovery all the way to TO220.
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Later: The hole size seems to exclude my "non-TO220" options. So, from the TO220s I have at hand, I'd probably go with either VT5202 (5A/200V), or STPSC110065D (10A/650V) or MBRF10200 (10A/200V), all Schottkys.
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Even later: In case anyone's wondering, I didn't check for ripple to explain the values above. It's all apart now, so I'm just going to proceed with the recap and... "rediod?..."  and rebuild this board. Should probably also see if any of the resistors has drifted.

[Rax]

Well, a CR1 bridge, C1, C3, C4, CR2, and CR3 "later," I still have high DC on at least TP1 (vs. TP2 taken as ground). I also have high ripple - about 1VAC - on the same test point... Given all rectifiers (except CR5/6) and all electrolytics are new, I just can't explain the ripple and high DC reading. Any pointers are welcome.

As a next step, I can think of verifying all resistors on the board, but I can't really imagine how they'd cause these symptoms. The other thought I have is some MB-level leak, which would be pretty bad news troubleshooting-wise.

I should also probably do the cards pull - and I guess my question from those having done it with this particular unit is if it the order and combinations of boards populated matters (can I break anything with al ill combination of populated boards?) - and see if that changes anything on the voltages I see, and therefore potentially localize trouble on one of the cards.