I asked a few weeks ago if anyone else could give me a report on the
function of the MUTE feature of their FT-8100R. I own 3 of these radios.
Two of them mute the audio all the way, one only takes the audio down
about 3dB, and that's NOT useful. I like the full mute.
One kind soul responded that his radio also only took the audio down
3dB, and also noted he'd prefer the 100% muting.
Today I had the opportunity to do some checking. I just got one of my
8100's back from Yaesu (warranty repair replacing most of the 2 meter RF
components), and did a check of some of the components in the mute
circuit. I compared the readings from a radio that does 100% muting to
another radio that does only 3dB. Here's what I found.
The mute circuit is on the UHF board in the audio output chain. Two
resistors are used in the circuit that are interesting. These are:
R2238 and R2237
The schematic says these are supposed to be 22K Ohms. The radio that
mutes 100% indeed contains 22K Ohm resistors.
However, the radio that provides only 3dB of muting had 335K Ohm
resistors in both of these positions. It's my guess that someone at
Yaesu thought they had a better idea and made a change... I'm going to
talk with the Yaesu USA folks about this and see if they'll fix this
circuit as per the schematic. I may try replacing the resistors myself
(they are sand -- tiny surface mount components).
I thought some of you might find this interesting. I'd REALLY like it if
Yaesu made information about ECOs available somehow (and explained why
they did them).
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