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AT-140 DOES NOT TUNE LOWER OR UPPER FREQ?

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AT-140 DOES NOT TUNE LOWER OR UPPER FREQ?

by wayneromberg » Tue Jun 19, 2018 1:42 pm

AT-140 DOES NOT TUNE LOWER OR UPPER FREQ?
My AT-140 turner installed with an ICOM 802 in 2006 no longer tunes to the lower frequencies or upper frequencies. It is installed with a backstay antenna on a Caliber 47 in 2006. It did work properly for many for several years. Then it started tuning slowly when cold. Sometimes I would have to go above or below the desired frequency to exercise it and then it would tune properly. In the last year, it has degraded so the it only tunes well in the 6-8 mhz range and then in the 12-16 mhz range. It will not tune down in the 4 mhz range or on the higher frequencies.
I did clean the connectors on both the transmitter coax as well as the connectors on the control cables. By the way they were clean and it made no difference. The unit does reduce the pwr output of the 802 during the tuning process as required which shows up on the SWR meter which tells me that the control cable is feeding voltage to the AT-140 and the “key “ signal is getting back to the 802. Also the fact that it does tune properly for some frequencies indicates the STAR voltage is ok.
I did inspect the internals of the unit hoping to find something obvious but the inside is pristine. The mode switch S1 is in the normal positon as required.
The three 8 switch DIP switches (SWR, SW4 SW3) were found with all the induvial switches in the on position with the exception of the sw 5 on DIP SW 5 was in a middle positon between off and on. This appeared to be incorrect since these DIP switches do not appear to have a middle positon.
Can someone tell me what the required position of the DIP switches is?
It appears the unit is full of relays and coils and I assume the internal electronics measures the SWR ratio and then operates relays to put the right coils in the circuit to tune the antenna.
Any wisdom would be appreciated as well as a recommendation on a good SSB radio shop that will charge a fair price to trouble shoot and repair this unit.
Wayne Romberg
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Re: AT-140 DOES NOT TUNE LOWER OR UPPER FREQ?

by Scott Berg » Fri Jun 22, 2018 9:16 pm

Hi Wayne! Where are you these days? Icom has service centers on both coasts of the US and they are the right place for tuners/etc.

Drop me a line and I'll walk you though some additional tests

Scott
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