Well this was on a supply that I purchased to rebuild for one of my C-lines.
Someone had broken off one of the terminals and I didn't discover it until I
took it apart to put the AC-4R board in. So everything else looks OK and as
soon as I get a new potentiometer, I should be in business. This supply will
then be used on my two meter Drake station (R-4C, T-4XC, TC-2, SC-2, etc.)
I don't know why the big rating in the DC-4 bias potentiometer. I have a
DC-4 but have never used it.
Thanks again for the assistance Garey. 73's
Terry, W8NJR
In a message dated 1/30/2008 1:21:00 P.M. Eastern Standard Time,
[EMAIL PROTECTED] writes:
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Terry -
Interesting.... I can't see any reason why the DC-4 supply should be
running so much more current through the divider.
Granted that carbon pots don't particularly like DC current flowing
through them, the Bias current is so small that it doesn't seem to
bother them. I hadn't seen or heard of a bad pot until yours, so the
vast majority seem to be lasting 40 years or so!
Do you know why yours failed? External short? Manufacturing defect?
The divider in the AC-4 only draws about 2.5 mA, and the supply is
specified at a 33k ohm load which is perhaps 2 mA.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
[EMAIL PROTECTED] wrote:
> Thanks Gary. I was looking at the rating on the bias pot in the DC-4.
> That is my mistake. It should be easier to find now. Thanks again for
> the correction.
>
> Terry,
> W8NJR
>
> In a message dated 1/30/2008 12:41:55 P.M. Eastern Standard Time,
> [EMAIL PROTECTED] writes:
>
>
> Garey Barrell <[EMAIL PROTECTED]> made an utterance to the
> drakelist gang
> ----------------------------------------------------------------------
> Terry -
>
> Where did you get the 5W rating? The Bias supply only supplies
> 3-4 mA,
> and the resistors on either side of the divider are 1/2W.
>
> The original is a standard carbon pot, probably rated at a watt or
> two
> originally.
>
> 73, Garey - K4OAH
> Glen Allen, VA
>
> Drake 2-B, 4-B & C-Line Service Supplement CDs
> <www.k4oah.com>
>
>
>
> [EMAIL PROTECTED] wrote:
> > I need a bias supply potentiometer for my Drake AC-4 power
> supply. The
> > schematic calls for a 10K, 5 watt potentiometer. Does anyone know
> > where I might purchase one? Thanks,
> >
> >
> Terry,
> > W8NJR
> >
> [EMAIL PROTECTED]
> > <mailto:[EMAIL PROTECTED]>
> >
> >
> >
>
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