HP-97 not Charging

[aj04062]

Hi,
I recently acquired a very nice 97, however it does not run or display connected to the AC adapter. Works fine with a charged battery. I tested charging circuit by running the battery dead then attaching the AC adapter. Still nothing.

Naturally I then checked the charging circuit resistors on the keyboard PCB. These seem to be fine.

The AC adapter is fine as it runs other machines.

I’m have several other machines. To my surprise the everything works as expected by swapping the logic board with another one. In other words, it appears that the logic board seems to be at fault.

I’ve checked the transistors and resistors on the logic board and they seem fine.

Any ideas on where to look next?

[Geoff Quickfall]

Diagnosing over the internet is like trying to describe a new operating system over the phone without a computer.

For me, I check the following in order:

1. Any observable mechanical faults; leaky caps, burnt resistors, visible cold solder joints, oxidized solder joints (flat powdery grey (gray) look.

2. If no visible signs then the suspect circuit solder is reflowed.

3. If no success and in this case. Follow the voltage pathway starting at the HP 97 plug. Test on each side of the next component for voltage; capacitor, diode (of course only in one direction) until you find a zero voltage indication.

4) Use the HP 97 manual for test points and compare voltage requirements versus your indications.

5) it may be the first IC in line with the power supply.

And of course, let us know what you find!

Best of luck, geoff

[AnnoyedOne]

(11-28-2024 06:39 PM)Geoff Quickfall Wrote:  Diagnosing over the internet is like trying to describe a new operating system over the phone without a computer.

Kinda like trying to take off/land/fly a plane with no instruments. Maybe it'll work. Maybe not!

Do they still test pilots with no instruments? Or do you just "reboot" the flight computer?

A1

[Geoff Quickfall]

Have done the following in the SIM:

1) loss of all electrics (737, 767)

2) partial loss of electrics (DC 10, 737,767,777,787)

3) loss of all hydraulics 737

4) loss of partial hydraulics

5) the dreaded electrical smoke…

Of course these all involve loss of instrumentation. On the 37, 67, 77 and 87 this results in partial instrumentation, usually on the Captains side. Bare minimum to keep the wings level until partial systems or all systems restored.

In reallity in 45 years:

1. DC 10 loss of all pneumatics with partial pneumatics reinstated after checklists

2. Shattered outerpane of windshield.

3. One loss of engine power (737) and one total engine failure (737)

4. Assymetric slat extension followed by flap only landing and high speed touch down (737 into SFO)

5. Major fuel spill at gate (3500kgs!) on 787; first flight as Captain in TPE. Led to an FAA, Boeing and Taiwan complete rewrite of the fuel spill manual. To put that in perspective, a 1 meter square spill of fuel is considered a MAJOR fire hazard. By the time I convinced the fueler to stop fueling the 30 meters square had been spilt. Did that by evacuating the aircraft at the gate including flight attendants and the other pilots, securing the aircraft, then running out on to the ramp because no one was answering my cockpit to ground calls, alarm and not answering the VHF. As soon as I ran down the stairs to confront the fueler, three guards with machine guns ran after me and pointed the guns at me. No one spoke english. Managed to stop the fueler from fueling with sign language, whereupon the guards grabbed meand escorted me to the gate to talk to the authorities. (Idiots all).

6. Total loss of hydraulics on a 737-200 and reverted to ‘manual reversion’ to land aircraft ( think no power steering while on a car racetrack with chicanes but include vertical chicanes also, that is 3D chicanes!)

Lots of minor issues but nothing major other than above.


My captains upgrade on the 787 final test was:

False cargo fire indication on the ground while using a ground cart for electrical supply as the APU was flagged inoperative.

Loss of both GPS just before coasting out of Japan for trans Pacific flight to Vancouver.

At cruise the forward cargo door warning light came on followed by an explosive decompression, emergency descent.

The door blew off the aircraft at 40,000 feet and took the right engine with it.

After securing those faults in descent to 10,000 feet and a return back to Narita had to deal with a business class passenger in the aisle having a heart attack. All this with a (supposed) brand new first officer and inexperience cabin crew.

Landed at Narita and having secured the aircraft, briefed the crew, and explained which paper work was to be completed, how to handle the crew, press and management; they passed me into the left seat.

That was followed by day two exam. The difference in the two days, each four hour exams with no break was that the Narita one you had all the time in the world to solve the issues (tons and tons of fuel). On day two, you had enough fuel to legally fly to your destination, hold for 30 minutes, leave to your alternate, hold for 30 minutes then land. So no time to deal with issues. Funny how fast time flies when no one at ATC wants to answer the radio, problems occur and the FO (in this scenario) is useless.

Solved with a MAYDAY and fuel low call.

Boeing reboots depend on the aircraft. The Embraer’s are rebooted every day prior to first flight or during a maintenance issue. The 787 has multiple computers for each system, so the two that agree kick out the one that doesn’t agree. To get a handle on that i suggest you read the greatest science fiction book ever written: “ the Excession” by Ian M Banks.

Cheers, Geoff

[AnnoyedOne]

Yeah, fixing calculators etc is much easier/less stressful.

My flying (anywhere) days are over fortunately. I'm not sure that the plane would make it.

A1

[teenix]

The 97 is not guaranteed to work with the charger alone, although it shouldn't cause damage. The printer and card reader definitely won't work. Some 97's may "sort of work" with the charger only if the power supply capacitors are in good working order. Otherwise, the rectified AC from the charger may not be smoothed enough to operate the calculator circuitry.


If that is not the case then...

The battery charge circuit is split between the CPU board and the key/display board. The key/display board seems ok, if a different CPU board makes the charger work.

The charge components on the CPU board are the 4 diodes near the top of the board, and the charger plug. If you have a multimeter you can test the diodes and the connections to the plug.

Another point that may fail and stop the charger is the board to board connector marked in the attached image. This is the connection that transfers the rectified charger voltage to the battery charge circuitry on the key/display board. If this is open circuit, then the battery will not charge.

cheers

Tony