Fluke 98B II service manual

[fleuroman]

hi

I'm trying to locate a service manual for the Fluke 98B II Automotive Scopemeter, or schematics for the digital board, a google search comes up with the owners manual (I have a hard copy of this) but no service manual/schematics. I've emailed the local fluke repair agent, who responded very quickly, and I've also contacted Fluke, who just say its an obsolete meter they no longer support. The digital board is very similar to the Fluke 91 Dave did a teardown on, the same Intel processor, the D-ASIC and M-ASIC have the same Fluke part number, the layout is slightly different.

The digital board has mods/repairs on a 74HC74D on the M-ASIC, which make no sense (see the attached image), even to this newbie. The device powers up, the screen lights up, but nothing is displayed.

any help appreciated
regards
Ross M

[fleuroman]

bump  anyone got any ideas on what they are trying to do with that 74HC74D?

[retiredcaps]

I can't help you with what the mod is doing, but maybe answering some background questions will get you some more help?

1) Are you the original owner of the 98B?
2) If yes, did the 98B just stop working one day?
3) If no, did you buy this as "working" from ebay or from some user?
4) If no, did you get this as "non working"?

[fleuroman]

I purchased it not working with a view to repairing it, I'm a mechanic by trade and these scopes were quite good in a workshop environment.

I'm guessing without Schematics, which Fluke cant supply, as the device is "obsolete". I've looked up the datasheet for the 74HC74D. pins 1 to 6 are flip flop 1 and pins 8 to 13 are flip flop 2. Pin 14 is VCC and pin 7 is ground. http://www.farnell.com/datasheets/1648944.pdf . Who ever did this "mod" has VCC jumping to pin 13 (asynchronous reset direct, Active Low) and pin 10 (asynchronous set direct, Active low) it doesn't make sense, nor does jumping pin 8 (complimented output) to pin 12 (data input) since both ouputs are supposed to change on the rising clock signal with data input. I was just going to jump in and remove the jumpers, but wanted some idea of what the previous repairer was trying to achieve, and are they trying to get a clock signal from pin 10 on the M-ASIC or send one from the flip flop.

It powers up on both the psu and batteries, and lights up the screen (I've checked a lot of test points on the board, I dont think its a voltage problem), the software for the device and what is displayed on the screen is on a flash ROM, and from reading other Fluke scopemeter manuals the D-ASIC gets the data to display from the flash. This board, like the 91 Dave did a teardown on has the same M-ASIC.

[MatthewEveritt]

Hard to be sure as I can't see which corner is pin one, and I don't have a pen and paper handy,  so take thus with a pinch of salt, but I think it's halving the frequency of the signal from the big chip in the corner of the image.

[retiredcaps]

I purchased it not working with a view to repairing it,

Okay, that makes more sense now.  While possible, I can't see a big company like Fluke selling test equipment direct from the factory with those bodge wires.

[fleuroman]

Hard to be sure as I can't see which corner is pin one

The labelling should mean pin one is in the lower left corner of the picture

[fleuroman]

While possible, I can't see a big company like Fluke selling test equipment direct from the factory with those bodge wires.

Dave showed a fluke bodge, in the teardown of the 196 scopemeter, they have a resistor flat on the board and a cap on 45 degrees, but Ive never seen anything like this, this is a repair job for sure.

[MatthewEveritt]

The labelling should mean pin one is in the lower left corner of the picture

Then yes, it's configured as a divide by two stage.
The two asynchronous resets are tied high, so do nothing.
!Q is tied  to D, so for every clock cycle (from the QFP)  the output (going off the top of the image) will switch state, meaning it takes two full clock cycles to get one cycle out.

If you're struggling to get your head around my hopeless explanation googling "d flip flop divide by 2" brings up plenty of good results.

Where does the output go?

[fleuroman]

Then yes, it's configured as a divide by two stage.
The two asynchronous resets are tied high, so do nothing.
!Q is tied  to D, so for every clock cycle (from the QFP)  the output (going off the top of the image) will switch state, meaning it takes two full clock cycles to get one cycle out.

If you're struggling to get your head around my hopeless explanation googling "d flip flop divide by 2" brings up plenty of good results.

Where does the output go?

a) your explanation wasn't hopeless, but googling /2 helped...
2) the PCB trace from the M-ASIC pin 10 looks like it goes to the clock input on the 74HC74D anyway, so why jump it...
iii) without a circuit diagram I cant tell where they are sending the output...

the big question is WHY?... my dad was an electrical engineer, and he always said "if its working, don't fix it"... this didn't stop me doing performance mods to cars as a teenager though 
It's obviously not how it was designed to work, unless the PCB traces under the flip flop do the same thing, and are damaged in some way, I'll have to remove the jumpers, and start from a standard board...

I'd still like a service manual...

[fleuroman]

Then yes, it's configured as a divide by two stage.
The two asynchronous resets are tied high, so do nothing.
!Q is tied  to D, so for every clock cycle (from the QFP)  the output (going off the top of the image) will switch state, meaning it takes two full clock cycles to get one cycle out.

If you're struggling to get your head around my hopeless explanation googling "d flip flop divide by 2" brings up plenty of good results.

Where does the output go?

Actually, if that was what they were attempting, they screwed up, as pin 11 is jumped to 14 VCC and 13 Async reset, but pin 10 is Async set, pin 11 is clock input. 

[MatthewEveritt]

Actually, if that was what they were attempting, they screwed up, as pin 11 is jumped to 14 VCC and 13 Async reset, but pin 10 is Async set, pin 11 is clock input. 

Ate you sure? It looks the other way around to me.

Have you tried probing at waveforms? Even a multimeter freq measurement could tell us if this bodge is working.

[fleuroman]

4Mhz on clock in 2mhz on output, the output goes of to a point on the board that is then connected to pin 64 on S83c196kb processor (T2CLK)... my glasses must have been dirty when I was looking at the jump wires... 

[fleuroman]

I got onto a mob in the USA called scopemeter repairs who list the obsolete meters, so I sent an email, I wasn't expecting a reply in the positive, I told him I was in AU and had exhausted trying locally for information/diagnostics/schematics, and fluke no longer support these devices, I got back a fairly positive response, what do you need, if I can help, I will... I explained the symptoms, the mod... and hopefully I can get schematics, diagnostics procedures and test point voltages/signals...

a huge kudos to scopemeterrepairs.com

[fleuroman]

still looking for Schematics/diagnostics
apparently this meter is identical to the Bosch PMS100, except for Bosch firmware...
and the Opel Tech31

[fleuroman]

finally back into this relics boards, been doing some case repairs where the battery compartment was damaged.
if the picture attaches...
I'm supposed to have -30v at C2523 then off to pin 11 on the connector. It took me ages to find the second capacitor C2507, the 35v should have been a clue, that it was through hole , it's the only one with that rating on the board. I have continuity from the + side of C2507 to pin 1 of the SOT23 BAV99 series diodes, but open circuit from C2507 to C2523. A small jumper sees -30v at pin11. I used coil wire from a small transformer off an A/C inverter board  , with some difficulty tinning it for soldering...

[griford]

Morning, found your old post online, I am trying to get the charging circuit diagram for the Fluke 98, it will power up and work perfectly from an externally charged battery pack, but will not power on or charge from the psu. any help would be appreciated