1502 and 1503 are in series. If one is bad the voltage will read wrong on both. I would replace both just to be sure. I believe others have used 1N4007 with success. Also check CR1401 and CR1402 at the other end of the module.
On Tue, 13 May 2025 12:30:33 -0700
"Bill NZ0T via groups.io" <nz0tham@...> wrote:
[Edited Message Follows]
I tested the three PIN diodes on the rear HPF board.? The Drake service group document says the following is? normal:
RX? ? ? ? ? ? ? ? TX
CR1501? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??0.9V max? ? ?11V typical
CR1502 , CR1503? ? ? ? ? ? ? ? ? ? ?11V typical? 0.9V max
I measured:
CR1501? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 12.01V? ? ? ? ?11.41V
CR1502? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 12.69V? ? ? ? ? 0.00V
CR1503? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 11.60V? ? ? ? ?10.67V
Seems only CR 1502 is still good so looks like I need to replace all three diodes to do it right.? I have seen some say 1N4007 will be OK as a replacement for the OE UM9401 diodes, is that true?? I have plenty of the 4007s laying around.
73, Bill NZ0T
--
73
-Jim
NU0C
Jim Shorney