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FT-101ZD MK2 AM BOARD looks odd / modified???

 

Hello,

I had a look at the AM board and it seems to have been modified ...
Is that from factory and what is this for? AM doesn't work that's why I pulled the board.

73
 

Hi Andrew. I noticed this too on an AM board I have here. I discovered it was done in the factory on later boards due to an earth problem causing hum if I remember right. Each section of the board receives its ground point individually with these tracks cut. Could have been an earth loop problem originally and cured by making the ground arrangement radial with the track cuts. The AM pcb fitted to my FT101ZD mk3 works with the tracks cut like this. It checks out on the schematic too.

After replacing my FM pcb with the AM one I then found that the audio bandwidth on AM is very narrow. It is necessary to fit a wide filter, (Yaesu XF-8.9GA), and modify the set to bypass the width control circuit to get the full 6kHz audio output. I have fitted the pcb and acquired a filter but have yet to do the mod to the width filter. This is a well known issue with the FT101ZD mk3. It may require fitting a toggle switch to the rear panel to switch the width control circuit in or out. I am still researching.

Hope this helps. Doesn't explain why yours is not working however.
 

There are two pins on one of the IF board plugs that have to be swapped. Pin 3 and 4 of one of them will send all audio but CW N thru the narrow filter slot. CW N will then go through the normal SSB filter.

If you need the exact jack number send me a direct email and I’ll look it up when I get a chance. I found it out when I was reversing the mod to use on CW. I later found it documented in the old Fox Tango newsletters, maybe May of 1985 or so.

73 de Chuck, WS1L ?

On Sat, Jan 22, 2022 at 5:38 PM ddelectrical via <ddelectrical=[email protected]> wrote:
Hi Andrew. I noticed this too on an AM board I have here. I discovered it was done in the factory on later boards due to an earth problem causing hum if I remember right. Each section of the board receives its ground point individually with these tracks cut. Could have been an earth loop problem originally and cured by making the ground arrangement radial with the track cuts. The AM pcb fitted to my FT101ZD mk3 works with the tracks cut like this. It checks out on the schematic too.

After replacing my FM pcb with the AM one I then found that the audio bandwidth on AM is very narrow. It is necessary to fit a wide filter, (Yaesu XF-8.9GA), and modify the set to bypass the width control circuit to get the full 6kHz audio output. I have fitted the pcb and acquired a filter but have yet to do the mod to the width filter. This is a well known issue with the FT101ZD mk3. It may require fitting a toggle switch to the rear panel to switch the width control circuit in or out. I am still researching.

Hope this helps. Doesn't explain why yours is not working however.

--
Chuck Chandler chandlerusm@...
 

Post it here if possible.?
I have two MKIII radios and two of these optional AM boards. I’d like to install them correctly myself.?
 

OK, here are the pages?from the FT newsletter?- it requires swapping pins 3 and 4 on IF Board J03.??

73 de Chuck, WS1L



On Sat, Jan 22, 2022 at 9:01 PM Bruce Collins <kb0tj1@...> wrote:
Post it here if possible.?
I have two MKIII radios and two of these optional AM boards. I’d like to install them correctly myself.?

FT-101ZD AM Filter mod.pdf
FT-101ZD AM Filter mod.pdf

 
Edited

Thank you? ddelectrical,

That's reassuring :)

I also got my AM board to work, it was a mix-up in the coax connectors (there are 2 of them, and they're both grey)
 

Hi Cuck, very interested in the mod you suggest. All I have seen to overcome the narrow AM audio bandwidth after fitting the 6kHz filter involves fitting a relay to bypass the next, (width filter - 2.7kHz ?), If there is an easier way that's great. Any further info most appreciated. Thank you.
 

Yep, that's just the ticket. Thank you.

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