HP-65/67: Strange AC-Voltage on plug-in supply type 82002A

[TI59]

Hello,

I got two HP-67 and a HP-65. The first HP-67 came with a plug-in supply type 82002A (PSU #1) same with HP-65 (PSU #2)

Since all there calculators working (card-reader fixed, resoldering, tantalum-capacitor "cure") I got a odd behavior on PSU #1

Socket / Front

#######################
# #
# 1 ( ) 2 ( ) #
# 3 ( ) #
# #
#######################

-------- PSU #1 -------

Voltage u13 : 1,06 VAC 50Hz
Voltage u23 : 1,57 VAC 50Hz
Voltage u12 : 1,55 VAV 50Hz

The DC amount is

Voltage U13 : -0,678 V
Voltage U23 : 0,061 V
Voltage U12 : -0,001 V

--- PSU #2 --------------

Comparing this to PSU #2 which looks to work

DC:

Voltage U13 : 16,3 V
Voltage U23 : 5,3 V
Voltage U12 : 10,9 V

AC Amount

Voltage u13 : 0,115 VAC 50Hz
Voltage u23 : 0,112 VAC 50Hz
Voltage u12 : 0,030 VAC 50Hz

--------------------

So the PSU #2 has instead of the 4,5 V printed on the PSU 5,3 V - this should be OK since one Jacque Laporte's Page

https://www.jacques-laporte.org/HP3520power20unit.htm


The circuit diagram figure 8 shows a Zener-Diode of 5,1 V - so I assume the Pins 2 and 3 are for the calculator while the 16 V charging the battery with Pin 1 and 3
Which is in my taste at least 3 times to high going through the circuit diagram which shows 4 Volts for both pins.

So PSU #2 maybe usable but I prefer go load the batteries wirth an external charger to avoid damaging something

I replaced in PSU #1 the electrolyte capacitor with 400 mikro Farad - no remedy

Since working PSU #2 has only minimal AC ripples PSU #1 consist only of AC which is strange. I can only imagine that a Diode of the rectifier is broken - but as far as I can see they work (I don't have an oscilloscope - only LCR-Meter and a Fluke 289 Multimeter) - next thing is Zener-Diode but this would explain one one strange VAC voltages at one output - but not the second

Anyone facing the same issue ?

Kind regards
Frank

P.s: I started programming with TI59 in 1981 in school - that's why I choose the Alias :-)

---------
UPDATE

According to EBay auction

Vintage Hewlett-Packard Battery Charger 82002A for Calculators w/Box

the measured Voltage of U12 is 10,94 VDC which matches my findings for PSU #2 - so should be OK.

[teenix]

Is there any AC voltage coming out of the transformer?

[Johnboy]

What's the tantalum-capacitor "cure" ? do you have a link to more info on that ?

Thanks
John