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Old 2nd Nov 2019, 6:56 pm   #6
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
Default Re: "Rectifier" 161A/162A

On the Tester 301B there seems to be a pin on the left, a pin at the bottom and a pin on the right of the XLR.

The pin on the left is ground. The pin at the bottom is the +ve input to the unit to run it without using the battery. The pin on the right is the +ve input to the charge circuit. You can check it as follows :

Ground goes to things you might expect to be system ground, like the -ve suppy pin of the TTL ICs and the common (also tabs) of the 7805 and 7812 regulators.

Switch to 'Ext'. The +ve supply pin will now be connected to the 2A fuse (F1) on the main board.

Switch to 'Off/Charge'. The charger +ve input is then connected to the 500mA fuse (F2) on the main board.

The battery in the Tester 301B is at the bottom. To get to it you have to remove the top cover, then the fixing screws on the main board. Unplug the battery cable from the front panel PCB (Conn 3) then lift the front panel and mainboard out together. It's made harder than it should be, the main board plug into a Molex KK type connector on the front panel PCB so they have to come out together. And of course there's the CRT.

With that out, the battery cover is obvious. Remove it, then there are 2 sets of 6 NiCd cells inside, plugging into a little connector bracket.

I can e-mail you the circuit if you want it.
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