[Heathkit] SB-644 problem

[Bill Kuhn]

I've got an SB-644 VFO hooked to my SB-104A.

The SB-644 works properly if I have it set for Remote T/R (transmit and receive). The remote freq displays on the SB-104 and I can TX/RX fine on the remote freq.

If I have it set for Remote RX (where it *should* be using the radio VFO for TX and remote for RX), the radio displays the remote freq on TX and RX and the TX and RX are in fact on the remote freq.

If I have it set for Remote TX (where it *should* be using the radio VFO for RX and remote for TX), the radio displays the Radio VFO freq and TX and RX are on that freq.

Basically, split operation is not working. I'm either all on the remote or all on the radio.

Checking test points, I'm supposed to be getting 13V on test points A, C, or D depending on whether I'm switched for Remote RX or Remote TX. I get 0V no matter what on these test points.

Looking back a bit for a voltage source, I see I should be getting 13V in on a line coming in from the radio. This (brown) wire is confusing. 

>From the assembly instructions, It is supposed to connect to pins 2 and 5 of the accessory jack on the radio.

>From the schematic I downloaded at http://www.vintage-radio.info/download/download.php?dir=heathkit&file=sb-644.zip, it shows a plug wiring diagram with the brown wire connecting to pin 3 of the accessory jack, which is 13V switched on tx from the radio (best I can tell).

The schematic I have in my sb-644 assembly manual does not show the plug wiring at all.

Anyone know which is correct?

If I'm making stupid assumptions or otherwise doing something stupid, please be kind :)

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Bill Kuhn - MCSE , Microsoft Small Business Specialist
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