Teardown : HP 4263B LCR Bridge meter (and repair)

[TiN]

Ok, time to start new restoration thread, this time HP/Agilent 4263B LCR meter. Yes, it's not Keithley, as some people already wondering
about Keithley graveyard in here, and reliability of their products 

Any owners of 4263B, which don't care warranty and can open up their meter (just 4 screws on sides and cover off) and take photo to give me a hand
in repairs?

I'd like to know value or photo of four thru-hole resistors near J101 (A output). They are burnt on 4263B i received today badly, so cannot read value.
Attached photo of them. Also one burnt SMD resistor from pin 2 of U182, D5210G IC.

Also photo of SMD side on two mosfet/transistor module U107 would be helpful (some parts blown there too) but that need removal of front panel (uncrew 6 screws and disconnect front
terminals)

4263B Service manual does not contain parts list, nor schematics to help on this matter.
Units still power on, and gives PASS on self-test, but i doubt it works fine with these damages....

Teardown coming... 





So far total visible damages:

4 x 1/2W resistors (need value for them)
Broken in half tranzorb Z6010
Burnt 1206 on main pcb (100 ohm?)
And on secondary module with pair of PNP/NPN bulged SOT23 with code Y23 (second module have same layout and same Y23) and bunch of 1206 resistors..

As usual - handle tasks via my redmine tracker.

Thanks!

[TiN]

Noone have 4263B ? 

[TiN]

Seem it's way to go good old way, if want something done - do it by youself
Will try some usual "try put some parts and see what happens" way later.

For now teardown, as whole internet don't have a single hi-res photo of 4263B internals...
So here we goes, all photos click-able for hi-res.

Front panel



Back I/O



Unit is not deep, but wider than usual Keithley/HP bench meters, so it will not match in rack as for size



Remove cover by two screws from rear:



Bird's view



Disassembly pretty simple and user friendly. All can be done in few minutes. Well thought design layout.



Input BNC connectors.



LCD is standard 40x2 char type, with very well known 44780 controller. Maybe later I'll change LCD to something with better contrast, if repair will be successful.



Protection on inputs?



Mains protection and filters.



Unit low voltage power supply in it's cage. Two 22000uF 25V KMH capacitors and lot of small 22uF 50V electrolytes.



Here goes digital board, mounted on standoffs above signal acquisition bottom board. MC68HC000FN10 CPU, two Sony branded CXK581000AM 70ns SRAMs, Xicor X28C64 ROM, AM27C2048 UV ROM with firmware (04263-85041 on my unit) and some big National Semi S9652AB SCX6B65AHI ASIC, and bunch of 7400 series logic and AMD-branded PALs around.






No batteries to store cal/configuration constants or NVRAM, only supercap there. So this unit pretty safe from dying from dead batteries, like some other gear



Some sections done with PCB-PCB modules, one of which near standoff had burnt resistors and SOT-23 resistor.
It's similar to other presumably alive module, so should be not very hard to find out what it does.



Good module:



It have PNP and NPN with small heatsinks on another side.

Input terminals protection and switching. Probably some stuff is borked here...
I already put some resistors to check basic functions, but it's not working right, readings sometimes, all over the joint often, sometimes seem ok.. Need debugging




Analog/switching/measurement components

[TiN]

Got back to 4263B repair project...

Made a schematics for little modules on 4263B front end board.



Some kind of half-bridge with pair of PNP/NPN.
SOT-23 probably BJTs, need to find out what part are they to replace on faulty module.

Faulty module had burnt 51 ohm resistors, 2.2ohm between power BJT's and "Y23" SOT23.

[ve7xen]

I think the transistors are 2SC3734 / 2SC1461. Might be hard to find these days, and mind the gain binning.

Nice looking instrument, I look forward to seeing it in operation

[TiN]

Great info.
I'll just buy modern replacement with similar parameters.

[TiN]

Replaced small PNP with similar part and bodged 1206 resistors.

Soldered 2 x 50ohm resistors instead of burnt ones (wild guess on resistance value, lol).
Removed blown transzorb (will install it later, don't have replacement atm).

LCR meter now able to do some measurements, seem pretty ok.
Self-test pass ok as well.

[Zucca]

Kudos TiN!

That HP 4263B was on my watching list for about 2-3 weeks, and I have to admit I would have been not able to repair it. The seller told me just the 4 resistor were broken, go figure.
I got at the end a DE-5000 (for my first LCR Meter, it is good enough).

I am happy that it ended to someone at the EEVBlog, still very surprised none here had one to compare/post some picture.
I think you made a good deal for that price.

Good Luck and keep posted on what is going on.

[VK5RC]

I am sorry I can't help,  have you tried the yahoo hp/Agilent group?
It sounds as though you are doing well by yourself.  When you do fix it,  I would post there as well,  regards Rob

[TiN]

Okay, some useless update/modification. I like negative LCDs more, so replaced original 40 x 2 for a blue negative.
Because it's HD44780 compatible interface, change is plain simple.

Before, original display is upper one with cables, new is on bottom.



Front face



Desolder ribbon cable for interface from original LCD



Cable soldered in place. Unconnected pin 15 and pin 16 are just backlight. LED Backlight is connected via separate cable, which is about to be soldered...



New negative LCD ready for installation...



Needed to update contrast setting resistor (Original 1.0kOhm, new is 2.0kOhm) and increase current for LED backlight by adding few 1R's in series with 10R's near J5 connector on digital board.

And final result:



Now unit is assembled and permanently joined homelab setup.
 

[Zucca]

Extremely cool TiN, I liked it a lot.
One day I hope to hack like you some gear.

There is always so much to learn in this Blog...

[SeanB]

On a lot of those displays the front polariser is a separate item, so you can take it out and flip it around to reverse the LCD. Either turn it 180 degrees or flip front to back and check.

[CaptnYellowShirt]

What's the difference between the 4263a and b?

[free_electron]

Proceoor board and display. A uses hp proprietary starbursts like in the 3488 and 6624 supplies. No backlight. When they stopped making those they introduced the b version.
The motherboard is the same. Only the cpu card is different (and the software of course)

[Sailor]

@ TiN

I PM'd you a while ago TiN, did you receive it?

Regards, Sailor

[carl_lab]

On a lot of those displays the front polariser is a separate item, so you can take it out and flip it around to reverse the LCD. Either turn it 180 degrees or flip front to back and check.

90 degrees, I think. So you need a new polarizer.

[MiDi]

Got a unit with OPT 001 & 002 from 2012 in mint condition, unfortunately with Error E-313: Calibration memory.
After a couple of restarts it went through POST without error - so there was hope for recovery of cal rom saving $$$ for full calibration/adjustment.
Unit cannot be operated with POST error - unless switching it to ignore POST errors (service manual p. 59).



Next step was to take backup of cal eeprom A2U1 X28HC64 (X28C64 on other units spotted).
Verification showed several errors - wear out or data retention time expired?
Comparison of 20 backups showed at least 12 wobbly bits, but luckily only in unused areas with FF - hence spotting the correct values was easy task.
Only one of those backups was correct, it was reflashed and several verifications were successful.
Seems this guy not only forgot part of its data, but also his datasheet which states 100 years data retention
Sidenote: the programmer needs to handle the software write protection - I used TL866-II+ with Xicor X28C64 template (after failing with AT28C64 - which lacks WP ).

Now unit powers up without errors, several self tests did not show any error - that was an easy fix 
Anyway it seems to be a good idea to get a replacement for this forgetful ic, only awailable compatible PDIP-28 as a new part seems to be AT28C64B.
It states only 10 years data retention in the datasheet, hopefully this is worst case with margin and better than 8 years of currently installed one.



Cal rom for this unit attached for reference.
xDevs repository has latest firmware 1.06 and several cal rom backups.
As TiNs pictures seem to have vanished, here the link to the article on xDevs.

Part of performance verification was successful - as far as I could get with my equipment.



PS: Someone in EU who would lend me cal-kit?

HPAK equipment (or equivalent) needed for cal:
Standard Capacitor Set   16380A
Standard Capacitor Set   16380C
100m Standard Resistor   42033A1
100k Standard Resistor   42039A1
OPEN Termination      42090A2
SHORT Termination      42091A2
1m, 2m, 4m Test Leads kit

[Le_Bassiste]

haha, extra cookie for the cool cal sticker
any idea what it reads?

[MiDi]

Unit came from Slovakia, but seems Cal-Sticker is hungarian.
"Év Következő Felülvizsgálata ideje Hónap" translates to "Next review time Year Month".
I guess that means next cal due 12 2019

[MiDi]

Replaced forgetful cal rom A2U1 X28HC64 with AT28C64B without problems.
As the keys had a sloppy response the front panel was taken off.
The silicone key pad was removed and cleaned carefully with warm water and soap, the counterpart with pcb cleaner.

As the front panel was off anyway, I decided to swap the LCD for a black/white one.
After setting the contrast with a 1kΩ and adding a current limiting resistor for LED backlight everything was put together again.
Keys are now responsive and as new, the display is pleasant with good contrast, but viewing angle could be a touch better.