Fluke 732B repair.

[kkayser]

My 732B has a defective battery charger.  It will not go into the constant current (fast) mode unless the unit has been run, on battery, for over 36 hours.  Less than 36 hours, it charges on the trickle charger. 

Does anyone know of any company (except Fluke) who will repair this?  Fluke wants $300 to "evaluate" then they will quote a price for repair.  THEN they insist on calibrating the unit for about $1100.00.  So, the total price will be $1400.00 +  the repair cost !!!!!!!!!!!!!!!!!!!!!!!!!!!!!  For repairing a battery charger

[TheElectricChicken]

Try a different lead acid battery first, beyond that you could just include some hefty switch to an external charger. Is the battery ruled out as the cause?

[TiN]

Also including your location would help people to suggest possible company around. 

[kkayser]

Try a different lead acid battery first, beyond that you could just include some hefty switch to an external charger. Is the battery ruled out as the cause?

The old battery had the same malfunction as the new one.  The new battery will run the 732B for 70 hours.  The charger does charge the battery, but slowly if the battery has not run the 732b for 36 hours.  Over 36 hours it works fine.

[kkayser]

Also including your location would help people to suggest possible company around. 

I live in the greater Milwaukee, WI area.  I have no problem shipping the unit anywhere in the lower 48.

[TheElectricChicken]

The old battery had the same malfunction as the new one.  The new battery will run the 732B for 70 hours.  The charger does charge the battery, but slowly if the battery has not run the 732b for 36 hours.  Over 36 hours it works fine.

By the time it has run the machine for 36 hours what state of charge is in the battery ?

[Bill158]

I don't know if you want to or if you have the necessary skills to work on the Regulator Circuit board?  But if you read the "Theory of Operation" section of the 732B manual P/N 869321 Rev 3, 11/97 at the bottom of the section on how the "battery charger" works, paragraph 4-16, they tell you:

"?Constant I to Float Voltage at 14.6V
 Float Voltage to Constant I at 12.0V
Any time ac power is applied, a transient is injected into comparator U501 pin 6 via C541. This results in the constant current recharge mode being enabled regardless of the battery voltage."

From your description of the problem with the circuit I would replace C541 before going any further.  This forces the supply to go into the constant current mode whenever AC power is removed and then reconnected.  If the battery is fully charged it will go from constant I to constant V within a few seconds.  My guess is that this capacitor has lost it's capacitance or is open.  If the LM 339 comparator U501 was bad the whole circuit would never work correctly.  As you can see the battery voltage has to drop to below about 12 volts before the supply goes into the constant I mode which fits with you observation of it taking about 36 hours to get into that state.  This battery takes quite a long time to drop to below 12 volts and 36 hours would seem about correct.
Good Luck!
Bill

[kkayser]

By the time it has run the machine for 36 hours what state of charge is in the battery ?
[/quote]

At 36 hrs the voltage is 12.67, loaded.  State of charge is approx 50%.  At 12.04 volts the charge light blinks (67 hours).  This battery has slightly higher MAH than the Fluke OEM.  I have run the unit for 70 hours before the "in cal" light goes out.

[kkayser]

I don't know if you want to or if you have the necessary skills to work on the Regulator Circuit board?  But if you read the "Theory of Operation" section of the 732B manual P/N 869321 Rev 3, 11/97 at the bottom of the section on how the "battery charger" works, paragraph 4-16, they tell you:

"?Constant I to Float Voltage at 14.6V
 Float Voltage to Constant I at 12.0V
Any time ac power is applied, a transient is injected into comparator U501 pin 6 via C541. This results in the constant current recharge mode being enabled regardless of the battery voltage."

From your description of the problem with the circuit I would replace C541 before going any further.  This forces the supply to go into the constant current mode whenever AC power is removed and then reconnected.  If the battery is fully charged it will go from constant I to constant V within a few seconds.  My guess is that this capacitor has lost it's capacitance or is open.  If the LM 339 comparator U501 was bad the whole circuit would never work correctly.  As you can see the battery voltage has to drop to below about 12 volts before the supply goes into the constant I mode which fits with you observation of it taking about 36 hours to get into that state.  This battery takes quite a long time to drop to below 12 volts and 36 hours would seem about correct.
Good Luck!
Bill

That is extremely helpful.  I was going to try a new comparator, but this is much easier.

Thanks

kk

[kkayser]

I could not find C541 on the board.  I looked at the component layout.  There it was.  But, it is not on the board.  Nor are U516 and C544.  That part of the board is empty.  The manual is dated 1997, 18 years ago.  Apparently, Fluke modified the board, and I have a newer version.  I'll call Fluke and see if I can get a schematic for this version.

Help would be appreciated.

[ManateeMafia]

kkayser,

I have seen your symptoms on a 732B. It essentially won't go into the CC mode if the power is cycled. I have seen other 732B's go immediately into CC after a power bump.
Since the charger was missing some of the components from the schematic, I had guessed the CC mode may have been an added feature later on in the newer revs. I would be interested in seeing if you truly have an issue with the board.

Also, I have had to replace the regulator on the charge circuit for a 732B-7001 due to a short between the input and output terminals.

[Bill158]

I could not find C541 on the board.  I looked at the component layout.  There it was.  But, it is not on the board.  Nor are U516 and C544.  That part of the board is empty.  The manual is dated 1997, 18 years ago.  Apparently, Fluke modified the board, and I have a newer version.  I'll call Fluke and see if I can get a schematic for this version.

Help would be appreciated.

kk:
My 732B S/N is 6785005 and my Power Supply Board A-5 is P/N 869185 rev K.  I don't see anything missing on mine nor do I see a place for U516.  My only assumption is that your 732B has a different A-5 board.  I just don't see any Engineering Change Orders or anything else from earlier units.  I would put a C-541 in, if the ends of that cap go to the right places, and see what happens.  I doubt a capacitor in there can hurt anything.  Why it would not be installed doesn't make sense to me, but what do I know?
Bill

[kkayser]

I could not find C541 on the board.  I looked at the component layout.  There it was.  But, it is not on the board.  Nor are U516 and C544.  That part of the board is empty.  The manual is dated 1997, 18 years ago.  Apparently, Fluke modified the board, and I have a newer version.  I'll call Fluke and see if I can get a schematic for this version.

Help would be appreciated.

kk:
My 732B S/N is 6785005 and my Power Supply Board A-5 is P/N 869185 rev K.  I don't see anything missing on mine nor do I see a place for U516.  My only assumption is that your 732B has a different A-5 board.  I just don't see any Engineering Change Orders or anything else from earlier units.  I would put a C-541 in, if the ends of that cap go to the right places, and see what happens.  I doubt a capacitor in there can hurt anything.  Why it would not be installed doesn't make sense to me, but what do I know?
Bill

I'm sorry is was unclear.  There is nothing on that part of the board, no holes, no conductors on the back.  An engineer at Fluke told me there is an upgrade on the charger.  My serial is lower than yours, 5535205.  So, it looks like my unit was made before the upgrade.  If I can get the upgrade specs, I can probably do it myself. Since the P/N of yours is Rev. K.  Is the "K" printed in yellow?  My board has nothing printed after "Rev." but does have something written in black that appears to be a "C".

Many thanks for your help.

[Bill158]

I could not find C541 on the board.  I looked at the component layout.  There it was.  But, it is not on the board.  Nor are U516 and C544.  That part of the board is empty.  The manual is dated 1997, 18 years ago.  Apparently, Fluke modified the board, and I have a newer version.  I'll call Fluke and see if I can get a schematic for this version.

Help would be appreciated.

kk:
My 732B S/N is 6785005 and my Power Supply Board A-5 is P/N 869185 rev K.  I don't see anything missing on mine nor do I see a place for U516.  My only assumption is that your 732B has a different A-5 board.  I just don't see any Engineering Change Orders or anything else from earlier units.  I would put a C-541 in, if the ends of that cap go to the right places, and see what happens.  I doubt a capacitor in there can hurt anything.  Why it would not be installed doesn't make sense to me, but what do I know?
Bill

I'm sorry is was unclear.  There is nothing on that part of the board, no holes, no conductors on the back.  An engineer at Fluke told me there is an upgrade on the charger.  My serial is lower than yours, 5535205.  So, it looks like my unit was made before the upgrade.  If I can get the upgrade specs, I can probably do it myself. Since the P/N of yours is Rev. K.  Is the "K" printed in yellow?  My board has nothing printed after "Rev." but does have something written in black that appears to be a "C".

Many thanks for your help.

Ah Ha, Now I see what your problem is perfectly.  See the attached photos of where the cap has been soldered in on my A5 board.  It is connected between R515 and CR506 as shown in the photos.  There are NO holes provided on the PC Board, but just an "after thought" that makes the whole charger work a LOT better and the way it is described in the Theory of Operation.  I hope this gets you going finally.  I didn't realize what this cap did before you asked.  I had seen it there but the circuit worked perfectly for the constant I/V operation when plugged in to AC line.  The reason I had been working on my PC Board was that the switch over point from constant I to V was about 15 volts which is way to high.  I just trimmed the divider circuit by replacing R514 with a better value that allowed the comparator to trip at 14.6 volts.
Bill

[kkayser]

kkayser,

I have seen your symptoms on a 732B. It essentially won't go into the CC mode if the power is cycled. I have seen other 732B's go immediately into CC after a power bump.
Since the charger was missing some of the components from the schematic, I had guessed the CC mode may have been an added feature later on in the newer revs. I would be interested in seeing if you truly have an issue with the board.

I think you are right.  There is nothing wrong with my board.  It is just an earlier version.  My board looks like Bill158's in the area pictured.  I'll get the cap, connect it and see what happens.

[plesa]

I surprissed that Fluke shipped unit with C506 damaged ( melted ) by soldering iron.

[Bill158]

I surprissed that Fluke shipped unit with C506 damaged ( melted ) by soldering iron.

That happened when I was troubleshooting the comparator not changing over from CI to CV mode at 14.6 volts, but up around 15.0 volts.  I was measuring all resistors in the circuit and couldn't find any that were out of tolerance.  I finally guessed that the comparator input VOS had drifted, but was never able to confirm that theory.  While removing and resoldering I managed to do damage to C506.  Sorry about that!
Bill

[plesa]

Ah, thats makes sense. Thanks for explanation!

[kkayser]

I talked to Fluke tech support person, Pat Stewart.  He was very good, as helpful as he could be under Fluke policy.  I asked if there was anything else that was changed when the capacitor was added.  Here is his email reply:

There was a PCN (product change notice) for the charging circuit. Unfortunately, we are not allowed to send out PCN's to anyone other than a Fluke service center.  As well as the capacitor, there are two resistors that are also changed in that circuit.

Good old Fluke.

There are not that many resistors that I can't check them all.  I will start with r514.  My charger cuts off near 15volts, so that has to be corrected regardless.  Is 13 Volts reasonable?

[plesa]

I do not have 732B but for lead acid sealed batteries is recommended to charge them max to 14,5V - 14,9V. And for continuous charging (trickle) mode is voltage lower  13,6V-13,8V, but this is not the case.

So 13V is too low I suppose.
Check what type of batery is used and adjust voltage according to datasheet, values above and for common types for UPS at 25°C.

[Bill158]

I talked to Fluke tech support person, Pat Stewart.  He was very good, as helpful as he could be under Fluke policy.  I asked if there was anything else that was changed when the capacitor was added.  Here is his email reply:

There was a PCN (product change notice) for the charging circuit. Unfortunately, we are not allowed to send out PCN's to anyone other than a Fluke service center.  As well as the capacitor, there are two resistors that are also changed in that circuit.

Good old Fluke.

There are not that many resistors that I can't check them all.  I will start with r514.  My charger cuts off near 15volts, so that has to be corrected regardless.  Is 13 Volts reasonable?

kkayser:
In reviewing what I did to change the switchover voltage I now see that I changed the value of R-520 from the original 18.1k to around 16.5k.  This got my switchover voltage down to around 14.5 volts.  The sealed lead acid battery spec is from 14.4 to 14.7 for a "full charge" of the battery.  It is interesting that yours also does not switch until around 15 volts, just like mine did.  Isn't nice of FLUKE that they won't let the end user know about any PCNs that would affect the end user!  I paid for this thing so I should get full support.  This is just like automobile manufacturers, they just don't want to tell the owner anything unless NHTSA forces them to disclose defects!
Bill

[kkayser]

Fluke seems to have the attitude that they, and only they, should repair "their" equipment.  My son has problems getting parts.  Fluke wants to "repair" the instrument then charge you an arm and a leg to calibrate it.  Their excuse it that they cannot be sure the device is properly repaired unless they calibrate it.  I think the real reason is that Fluke spent a large sum building their Josephson array and now has to get their money back.  So they coerce everyone to pay for calibrations. 

This will work until someone comes out with a good competitor to the 732B.  Also, this policy sours me on all other Fluke products.  All of my 6 1/2 to 8 1/2 digit meters are Keysight.

[Bill158]

Fluke seems to have the attitude that they, and only they, should repair "their" equipment.  My son has problems getting parts.  Fluke wants to "repair" the instrument then charge you an arm and a leg to calibrate it.  Their excuse it that they cannot be sure the device is properly repaired unless they calibrate it.  I think the real reason is that Fluke spent a large sum building their Josephson array and now has to get their money back.  So they coerce everyone to pay for calibrations. 

This will work until someone comes out with a good competitor to the 732B.  Also, this policy sours me on all other Fluke products.  All of my 6 1/2 to 8 1/2 digit meters are Keysight.

I just got my 732B "Calibrated" early in August 2015 by FLUKE.  I took the Z540.1:1994 cal because it was the least expensive.  The Z540.1:1994 gives "as-found" and "as-left" readings.  I fully expected FLUKE to adjust the 732B to output exactly 10.000000 volts.  Instead they just measured the output voltage to their standards ( a bank of 4 ea 732Bs ) and reported that value was 10.000023 volts ( high by 2.3 ppm ) for my 732B.  So this covered the "as-found" and "as-left" portion of Z540, with the "Result Summary:  In Tolerance".  Of course this is fine also as I can now assigned output voltages to my other 732As.  Then I can track any drift between all of these units.  But for $695 you would expect a little more.  You are right, they need to cover all those on-going costs of maintaining a Josephson Junction Array.  FLUKE did cover the return shipping ( overnight ) and a proper shipping box, which I can use when I decide to send the 732B in again, in a few years from now.
Has anyone else out there had the Z540 cal also and experienced the same results in service from FLUKE?  Just wondering?  At least I have a good idea what a "volt" is.  My last cal was 10 years ago when FLUKE had a Cal Lab in the SF Bay Area.  I had adjusted my newly acquired/used 732B to what I "thought" was 10 volts, from my 732As, before I sent it in for Calibration.  So during the last 10 years I was only 2.3 ppm high which is probably pretty good over that period of time.
Bill

[kkayser]

We soldered the capacitor in and it seems to work fine.  The charge light goes on whenever the unit is connected to line voltage. I ran it 74 hours and the low batt light did not go on.  ( I know it works). Charge took somewhere between 24 and 36 hrs.  Now off to Tektronix for calibration. They do both voltages for $439.00.

[ManateeMafia]

I shipped mine to Tektronix with a new battery and the in-cal light out. They adjusted the output as close to 10V as possible, or the output just happened to be within .2 ppm of nominal. They noted the light was out but they never noted it was adjusted.