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Author Topic: FT-102 low sensitivity  (Read 1628 times)
KG9H
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« on: September 06, 2017, 02:38:04 PM »

Trying to find a clean FT-102 schematic and board layouts to fix a receiver problem.  I have a low sensitivity issue on my 102.  I can hear the calibration signal with the preamp on, nothing with it off.  With the preamp on it is 70uV for a signal of any kind.
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G3RZP
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« Reply #1 on: September 07, 2017, 04:35:30 AM »

There's an FT102 group on Yahoo groups which you might find useful to join. There's a lot of manual info there, but the main service manual isn't, partially because it would be a major job to scan it.

Getting a schematic and aboard layout corresponding to your model of FT102 is another matter. There were a lot of changes made during the various production runs, and you can find significant differences between what you physically have in the radio and what you have - or can get - documentation for. For example, mine has a relay in the screen circuit of the PA, which I was told was to reduce power for Japanese Novice bands, but there's no documentation at all and it's not on the schematic.The operators handbook has all the original schematics, which at least provides guidance.

The usual problem is all the relays in the receive path oxidise because they 'dry' switching. Many people change them: I just fitted an RF choke, a capacitor and some resistors to bleed some current through the contacts from enough volts to break through the oxide film. If you have not already done so, try repeated switching to tx and switching the RF amp in and out several times.

Good luck with it. I inherited my FT102 which my father bought in November 1983  6 months before he went SK. Much modified, it has got me to the top of the DXCC Honor Roll, so the receiver is good enough for most people in today's RF noisy environment. If you need further help, my email is g8onATbtinternet.com
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K1DA
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« Reply #2 on: November 21, 2017, 05:48:04 PM »

Antenna relays get flaky  on the 102. 
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HAMHOCK75
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Posts: 402




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« Reply #3 on: November 21, 2017, 10:01:14 PM »

If it is anything like the FT101, RL1 will control whether the unit is in receive or transmit. For me every time it returns from transmit to receive and the receiver sounds dead, it is this relay. It is always the same contacts that control transmit/receive because they draw very little current so they do not self clean. You have to be very careful cleaning them because the plating is thin. If you accidentally clean through the plating to base metal, it will require far more frequent cleaning to stay working.

It is simple to test, just take the relay out and measure between the contacts with an ohmmeter.
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N8FVJ
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Posts: 378




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« Reply #4 on: November 22, 2017, 07:22:16 AM »

Clean the relays. FT-102 are well known for dirty relay contacts.
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KOP
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Posts: 247




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« Reply #5 on: November 23, 2017, 12:43:44 PM »

https://www.regonline.com/Register/Checkin.aspx?EventId=1121889
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October 02, 2017, 07:53:41 PM
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