Dear TEA-fellownuts,
today (Friday) the Power Desingns Model 2005A showed up at my doorstep.
I have promised to do a teardown and here we go:
The package was not stellar but okay. It arrived undamaged at first sight.
This is the front. Looks nice and clean.
Backside the same, nice and clean. Someone has crossed out the 125VAC remark.
Let's have a closer look inside. Left picture is an overview, the red circle is the top of the oven. Middle picture shows more details of the wiring. The board does not have any traces on it. The picture on the right shows a side view of the oven (sorry, it is a bit blurring).
From left to right: mains input with fuse, transformer with some suspicious looking capacitors, outputs backside with capacitors
Left to right: Rotary switches with some precision resistors, another viewing angle to the rotary switches and the binding posts for the frontside outputs with some capacitors from Sprague
Left to right: the slot for the access to the cal- and zero-trimpots, the trimpots itself and a sideview of the instrument, made by General Electric
Left to right:
Some Sprague capacitors (the date codes suggests, that this 2005A has been built around 1970/71), Sprague capacitors and the wiring to the NPN power transistor for the linear regulation, the power transistor Q5 itself (Motorola MS1700, NPN-type, no idea, what this 6-36 means)
This is a hi-res picture of the bottomside of the board. Isn't it gorgeous?
Here are some details of the board and more datecodes from 1969. The fuse looks like the very first one which never got replaced.
But is it working? Let's find out ...
I've connected it to my Keithley DMM7510 because I wanted to see how it behaves when switched on.
I've set the 2005A to 10V and it seems, it is ca. 3mV off. But let's see how it will drift.
Left to right: Some more measurement after ca. 2h uptime, The two pictures to the left are showing the complete plot so far. The overshoot can be seen very nicely and it seems it want to settle somewhere around 9.997200V (actually it shows 9.997238V). There are also some spikes downwards, no idea actually where they are coming from. Will observe this further. The two pictures to the right are showing the details of these spikes. There are also some spikes upwards. My guess is: they are caused when the heater of the oven gets switched on. will check this as well.
Edit:
Forgot to show some statistics and the settings of the meter:
The contacts of the rotary switches need some cleaning and the switch for the 10mV range is hard to rotate - need some cleaning and lubrication but besides from that all the knobs, verniers and switches are working very nice.
I do like this 2005A and I'm happy that I got one which can be directly connected to 230VAC.
Thanks for watching, I hope, you've enjoyed this teardown.