HP 53131A Universal Counter Repair

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My original 53131A Counter died with a weird error (would work for frequency but not rise time). So to fix it I bought a new motherboard (was cheaper than buying parts) but that also had a problem. In this video I work through the issues and fix the problem.

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Опубликовано:

24 мар 2017

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Комментарии : 28

@SoddingaboutSi 7 лет назад

Good job. You sound a happy man.

@tgsoapbox 7 лет назад

Thanks - I certainly was glad to get it going as I'd optimistically ordered the upgrade parts and the company I bought the motherboard off didn't have any more. If this had failed I was going to try moving parts between the 3 boards to see if I could get a working one. Glad it turned out to be such a simple fix.

@PelDaddy 7 лет назад

Nice job as usual. Thanks for sharing.

@tgsoapbox 7 лет назад

Thanks - Glad you enjoyed it.

@vidasvv 6 лет назад

Nice job, tnx for sharing ! I added the 10MHz oven and the 3GHz option and worked great for 6 months but now I get the "FAIL: FPGA" during power up. Makes a dandy paper weight now :( 73 N8AUM

@tgsoapbox 6 лет назад

Glad you enjoyed the video - I found the main board in this video from a vendor so you might be lucky to be able to get a board - It seems most of the failures on these boards are in the front end rather than the FPGA. I had to go through 3 boards before I found one that didn't say FAIL: FR END.

@TheDefpom 7 лет назад

One of those caps looks bulged in the power supply, based on how the light is reflecting on it.

@tgsoapbox 7 лет назад

Thanks, I didn't notice that but I'll take a look when I open it back up to install the oven and pre-scaler.

@tgsoapbox 7 лет назад

You're right - Just checked them when I installed the HS Timebase and the Pre-scaler. Will ened to replace them. Thanks for the heads up.

@JW-bd7em Год назад

I am having the exact issue you describe at the start of the video - frequency measurements work well but anything to do with timing fails. Can you remember at all where you got to with troubleshooting the ICs / FPGA before you changed the board? Do you know what outputs are expected from the front end when in timing mode? I can see the TIMEINT signal go high when I change to timing mode, and the CH1 line to the FPGA also goes high (when not in timing mode this line is a square wave with frequency some scaled value of the input signal frequency). Any help would be super appreciated!

@tgsoapbox Год назад

Unfortunately, I can't remember where I got to in looking at this - I think I did pretty much what you were doing in tracing the signals and they seemed to die somewhere (from a quick look at the schematic I have) around U52/53 but I really don't remember. What I do remember is that the ICs were sort of unobtanium with only those dodgy "warehouse" vendors having them. I wasn't sure if what I was looking at was correct though, which is why I didn't want to just go out and buy a replacement IC on speculation. Sorry, I can't be more helpful - Did you try the HPAK forum on groups.io?

@JW-bd7em Год назад

Thanks for the quick response! I will try the HPAK group. I’ve found U52/53 and U65 on ebay for not crazy prices but I was also wondering about Q10 as that seems to do something asymmetric and is driven by TIMEINT. Anyway I haven’t actually taken it apart fully yet (shield is still over the front end) so I should probably do that before I order anything!

@tgsoapbox Год назад

@@JW-bd7em Adding your post from the HPAK group here in case someone else goes looking for information on this (no solution or comments at the time of posting) - groups.io/g/HP-Agilent-Keysight-equipment/topic/hp_53131a_not_measuring_time/94582628

@JW-bd7em Год назад

Great, thanks for doing that. Fingers crossed someone is able to help!

@TheDefpom 7 лет назад

I see a what looks like a tantalum on that board, my guess is its shorted out... I'm only at 15.30 in video... so you may find that anyway.

@tgsoapbox 7 лет назад

Thanks, by now you've probably hit the real cause. If you look closely there seems to be another line in the track near the first one. I wonder if the whole thing came free. I didn't notice that when I was repairing it.

@douro20 7 лет назад

I wonder if anyone has developed an OLED display for these, seeing that it uses SPI?

@tgsoapbox 7 лет назад

Interesting project idea but now I've taken a closer look I think I was wrong on the SPI bit. The 68331 is pushing data out on it's MOSI pin but the VFD IC is an SN75518 which doesn't seem to be an SPI. However it does seem to be serial data so it might be able to be easily decoded (It seems to basically be a shift register that drives the VFD).

@dmg244 7 лет назад

Which firmware revision you have?

@tgsoapbox 7 лет назад

Sorry for the delay - Rev 3703

@dmg244 7 лет назад

Thank you! May be anyone know where can download new firmware?

@dmg244 7 лет назад

Thank you! I have two 53131A with 3402 and 3703 firmware. For example in 3702 display look like 10.000,000,00. In 3402 display look like 10.00000000 and it's very hard to read freq. I'm put EPROM IC's from 3703 in 3402 device and all working fine. Already ordered EPROM IC's and try to find newest as possible firmware to program them and test. I find Service note from Agilent site that says that 3944 firmware was in 2003 year. May be this is latest firmware for 53131A...

@tgsoapbox 7 лет назад

Great. Let me know how it goes, I might update mine too (though I'm happy with it as is)

@dmg244 7 лет назад

OK, but I can't download files: "You need to be a member to perform this action." I sent request to join the group, but it's still not approved.