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  1. DRAKE-RADIO
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Bad 4NB?

 


I have a 4NB noise blanker that Ron, WB4HFN said he was unable to repair due to parts availability.? Is there anyone who repairs them???
Thanks & 73
Jay
W6CJ
 

Jay, I just took a look at the schematic and didn't see anything that would currently be unavailable except maybe the coils and possibly the socket for the blanker. What is specifically wrong with it? Is it physical damage or electrically not functioning?
?
Dave
 

Dave,
I shipped an R4C (with PTO and other issues) to WB4HFN, who reported the NB was not repairable - parts availability.

Before shipping the R4C with the NB installed, I tried alignment from the R4C manual and not all of the 4NB adjustments were responsive.

Thanks & 73,
Jay




On Thu, Jan 2, 2025 at 12:44?PM Dave W7GZ via <w7gz=yahoo.com_at_groups.io_lastradioman@...> wrote:

Jay, I just took a look at the schematic and didn't see anything that would currently be unavailable except maybe the coils and possibly the socket for the blanker. What is specifically wrong with it? Is it physical damage or electrically not functioning?
?
Dave
 

Jay,
You might try the following procedure. I found this to work if the Drake procedures won't.?
?
If C19 & C25 adjustment procedure above does not work, provide a pulse source?
and adjust C19 and C25 for minimum pulse noise level, preferably zero with?
the function switch in the NB position. Verify adjustment by turning the function switch?
from the NB position to the Normal position and verify operation.
?
For the pulse source, I use my Weller WLC100 Soldering Station. It has an SCR to regulate the heat and is very noisy. Remember that the 4NB works on pulse noise. It will not work, in most cases with power line-type noises.?
?
73's,
Mark, WB0IQK

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