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Hello,

I just received the HP-IL Printer and HP82161A cassette drive which I bought on EBay.
Both of them are using AC Adapter marked 82059D

110V AC input
8V AC output

Because I am in Europe, those adapters are not usable for me, so I want to make my own adapters. The only problem is that I do not know if the 8V AV output means 8V under load or without load.

Please, can anybody measure the actual output (without load) of this adapter and write me the voltage ?

Thx a lot

If memory serves me right, the idle voltage of these adapters is around 10.7 VAC. The 8 VAC nominal output is at the rated current; since the small transformer runs near saturation, the voltage drops quickly as the load increases.

For the printer, too strong a transformer may mean excessive charging current, wearing out the battery pack prematurely. (Of course the simplistic charging circuit does that already even with the standard adapter, but that's another matter.)

For the HP-IL interface, I _believe_ (hope you don't mind that I am not taking one apart just to check!) that it uses a standard 7805 internally for voltage regulation, which means that it can accept a wide range of input voltages without damage.


Viktor

Thx for the information.
The higher charging current should not be problem, because I suppose that the battery pack is old, so I will replace the NiCd cells with new ones. And modern NiCd cells are more tolerant to higher charging currents.

pavel,
here's what i found out so far:
charger HP82066B 'eurocharger' connected to a HP82161A cassette drive delivers the following voltages (all true RMS)
mains: 234.7 VAC (as a reference); charger with nothing connected: 12.08 VAC; charger with cassette drive 'OFF': 8.4 VAC; charger with cassette drive 'ON' and idling: 6.71 VAC
(yes, the battery pack is nearly dead...)

cheers,
hans

Thx a lot.

Now, I have a working charger.

I simply took a cheap (approx. USD 5) universal DC adapter (made by Hama), I removed the diodes and capacitor from inside and I have exactly what I need. When the universal adapter is set to 9 V, there is 11.5 V without anything connected and 7.5 V when printer is connected and batteries are charging.

Many (probably all) of the HP units that use the 82059D charger have a full wave bridge rectifier input. As long as there are no connections (via peripherals) to ground ouside of the calculator this circuit has the magic property of accepting AC or DC inputs of either polarity. Generally you need a higher level DC input than the specified AC input because the AC input is specified as RMS voltage while the peak voltages of the AC input are 1.414 * RMS. I know of at least one HP97 that has been running off of a 12VDC lab supply for ages. I don't think any changes were made to its internal circuitry.

So, there is no need to remove the guts of the standard wall adapter :-)
From the electrical point of view, it is a known fact (the full bridge rectifier), but I was not sure about the internals of the HP printer and cassette drive and I was affraid to burn them, so I wanted to be sure...

Thx for the info

Earlier this year I did some tests on some of the HP chargers -- connected different load resistors to them nd measured the voltage. Actaully, I used an HP3421+HP71 to measure the voltage, and to control relays to switch in different resistors so I could sit back while it did all the work :-)
Anyway, the chargers for these units (the 2 pin charger used on the HP71, HP75, HP41 battery pack, HPIL stuff, HP9x series, etc)
have an output voltage (off-load) of about 12-13V (depending on the mains input voltage and the type of charger (UK .vs. European .vs. UK) and an internal resistance of aobut 11 Ohms.
The battery charging current (for the internal NiCd pack) is partially controlled by this internal ressitance, so you shouldn't use a 'perfect' voltage supply.

Be careful!. _MOST_ HP devices using this series of chargers have a full-wave bridge rectifier input and can take AC or DC. But there are at least 2 exceptions that I have come across.
The first is the later battery pack for the 9114 disk drive. It has an SCR-based charger, which requires AC (or at least unsmoothed DC) to work properly. Feed it pure DC, and the SCR will latch on, and the the battery will be overcharged.
The other is the 82164 RS232 interface. Most of the HPIL interfaces just have a brisge rectifier/capacitor/7805 power supply and will run off DC. The 82164 has that (for the logic)
but it also has a mains-freqeuncy transformer inside to step up the AC input to about 16V. The output of that is rectified and smoothed, then regulated down to +/-12V for the RS232 buffers. This unit _needs_ an AC input for the transformer, of course.