Re: [drakelist] DRAKE R-4C (4-NB Noise Blanker)

[Garey Barrell]

Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Steve -

I assume you have the shorting plug in the MUTE jack?  :-)

First lift up slightly on the Calibrator board.  Sometimes the leads are
left too long on the bottom of the board and short out to the chassis if
it's pushed all the way down.

There are fully annotated photos of the NB-4 on my C-Line CD, but Drake
didn't provide any description or voltage information.   I have a scan
of the 34-PNB Noise Blanker on my TR-4 CDs, which are essentially the
same circuit, and it has a circuit description included.  That CD also
has a separate set of photo's with voltage measurements for the 34-PNB.

If you want the C-Line CD, I could include a copy of the 34-PNB manual
and docs on it as well.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, B & C-Line and TR-4/C Service Supplement CDs
<www.k4oah.com>

STEVE SCOGGINS wrote:

STEVE SCOGGINS <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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I have a Drake R-4C receiver with the 4-NB noise
blanker that is not working.

I have the 4-NB manual with schematic from the bama
website.

There is no receiver audio when switched to NB
position.  Using a scope I can see that the 7.935 Mhz
oscillator in the NB is oscillating. Perhaps the FETs

are blown in the NB.

Does any one have a parts layout and theory of
operation for this NB. This type of info. would be
useful for troubleshooting.

73 Steve KE7RR

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