09-22-2014, 08:47 PM
Today was a nice day for me!
This afternoon I collected my first HP-35 at the Post Office, and I have to share this with you:
The seller sold it for parts, as it didn't power on.
The charger cable near the 3-opin plug was tampered by someone that probably tried to repair a broken wire.
I was not expecting too much from this item, but when I measured the output of the charger, I saw to my surprise that the readings were at the wrong pins of the plug, having the 16V current and the 5V voltage sources swapped!
So I thought, surely this calculator has been beaten to death by receiving 16V to the power supply DC-DC converter.
What are the odds of these components to survive under these conditions?
Actually, a lot - The 16V are a current source to charge the battery.
Having corrected the mistake, I couldn't wait!
I used the multimeter in current mode and used its test probes as a switch, touching the switch contacts carefully while looking to the current meter... I saw 89.5mA... Yes, looks good enough so far...
And amazingly the calculator came to life on the first try!
The display gave that nice looking red color with a "0.".
I tried the classical multiply test: 12345679 ENTER 9 * -> 111111111
And just to make sure it works: 1000 log -> 3
This calculator was sealed from factory, never opened before, despite a lot of dirt in the keyboard area. So I decided to open it to do a good cleaning.
The electronics PCB is immaculate, though.
I will share better pictures later. For now I'm uploading the spontaneous shots took at the time of the troubleshooting.
This afternoon I collected my first HP-35 at the Post Office, and I have to share this with you:
The seller sold it for parts, as it didn't power on.
The charger cable near the 3-opin plug was tampered by someone that probably tried to repair a broken wire.
I was not expecting too much from this item, but when I measured the output of the charger, I saw to my surprise that the readings were at the wrong pins of the plug, having the 16V current and the 5V voltage sources swapped!
So I thought, surely this calculator has been beaten to death by receiving 16V to the power supply DC-DC converter.
What are the odds of these components to survive under these conditions?
Actually, a lot - The 16V are a current source to charge the battery.
Having corrected the mistake, I couldn't wait!
I used the multimeter in current mode and used its test probes as a switch, touching the switch contacts carefully while looking to the current meter... I saw 89.5mA... Yes, looks good enough so far...
And amazingly the calculator came to life on the first try!
The display gave that nice looking red color with a "0.".
I tried the classical multiply test: 12345679 ENTER 9 * -> 111111111
And just to make sure it works: 1000 log -> 3
This calculator was sealed from factory, never opened before, despite a lot of dirt in the keyboard area. So I decided to open it to do a good cleaning.
The electronics PCB is immaculate, though.
I will share better pictures later. For now I'm uploading the spontaneous shots took at the time of the troubleshooting.