[Yaesu] Fwd: Deaf FT-901DM

[n3sb at qis.net]

Hi Wayne;

Thanks for the suggestion. I will give that relay a close look.

 From the RF connector on the back of the radio, I can measure a very  
low DC resistance to ground, which would probably be the primary side  
of T1. When I hit the attenuator button, the DC resistance goes up  
corresponding to the resistors in the pi attenuator network.

I hope to get some time soon to walk a signal generator through the RF  
and IF stages in the radio, to measure their gain - hoping to find the  
area where the problem is lurking.

I still find it very unusual the way the calibrator level drops when a  
load is connected to the radio. So I'm really suspecting something in  
the front end.

73; Steve, N3SB

Quoting wayne johnson <k9wkjham at gmail.com>:

> have look at the change over relay
> my ZD had a similar issue before tha magic smoke came out of the mains
> transformer [?]
>
> On Sun, Apr 26, 2015 at 1:54 PM, <n3sb at qis.net> wrote:
>
>> I should add that I've tested the Attenuator switch and it is behaving OK.
>>
>> 73; Steve, N3SB
>>
>> ----- Forwarded message from n3sb at qis.net -----
>>     Date: Sun, 26 Apr 2015 14:45:35 -0400
>>     From: n3sb at qis.net
>>  Subject: [Yaesu] Deaf FT-901DM
>>       To: yaesu at mailman.qth.net
>>
>>
>> Hi Folks;
>>
>> I picked up an FT-901DM recently that's got a deaf receiver. I've checked
>> the antenna fuse and it's good. Also checked the first RF amp transistor by
>> plugging it into a Kenwood radio, where it worked fine. I've re-seated the
>> plug in boards and done a little other basic poking around. Getting 50
>> Watts out from the transmitter with an old pair of 6146's.
>>
>> The calibrator level is about S-7 on 20m, and the preselector does peak
>> the calibrator in a normal way. However, when I connect a dummy load to the
>> antenna connector, the calibrator level drops down to an S-1. Is this
>> normal behavior??
>>
>> 73; Steve, N3SB
>>
>>
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>>
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