| Author |
Message |
    
Drgrant
New member
Username: Drgrant
Post Number: 4
Registered: 6-2007
| | Posted on Thursday, June 07, 2007 - 1:06 pm: | 
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I have one of these amps, which is basically a
knockoff of an M4V, although in my case the
amp has been modified, a tech removed the
driver pill from the input circuit. It was 1
SD1146 feeding 8 but now it is just the radio
feeding all 8 pills directly. (I drive it with
an Icom 706mkII, turned down of course)
The problem I am having is that the amp does not
want to unkey. If I key it for even a short
while on AM or FM, then I hear this "whoooossssh"
of static come back at about S10 or so into the
reciever for many seconds, and then it eventually
unkeys. It is worse if I use the amp in SSB
mode with the delay.
This amp also had an RCA jack on it for direct
keying... whenever I use the direct key it ends
up being worse, and I have to shut the amp off
to get the "whooossssh" noise to go away.
All tests were done with a Bird 43 into a Bird
dummy load, using a 100A switching power supply
set to 14 VDC.
Any ideas? I would even settle for getting rid of the RF sensing circuit entirely... as all my rigs are direct key capable.
Output of the amp is not a problem... I have
gotten this thing to key 700W+ on the bird,
obviously I didn't do most of the testing like
that, but output is fine and input SWR is
low. I would bring it back to the guy that
worked on it but he had to shut his shop down
due to lack of business in the area, and I have
no way of contacting him otherwise.
-Mike |
Drzuo
Junior Member
Username: Drzuo
Post Number: 12
Registered: 1-2006
| | Posted on Friday, July 06, 2007 - 11:54 pm: |
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one possibility I can think of off the top of my head. Across the keying relay's coil terminals, there should be a diode reverse polarized.1)is it there, 2) is it good? I had a similar issue once, and it was a bad diode, when the field in the coil collapsed, it spiked my Icom and gave it all sorts of heck, just like you described. |
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