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Author Topic: IC-2340H UHF Transmit  (Read 13007 times)

AD5QA

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IC-2340H UHF Transmit
« on: July 09, 2014, 12:50:46 PM »

I got the  IC-2340H from my grandfather and the UHF side does not transmit. I am assuming the output transmitter, havent had time to crack it open. If this is common can anyone tell what part number and where to purchase it? VHF transmits fine. Thanks.
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AD5QA

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RE: IC-2340H UHF Transmit
« Reply #1 on: July 14, 2014, 06:15:19 AM »

sp(output transistor) Was typing on my phone when I wrote that message. Just getting back into town from a move and catching up.
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KA4POL

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RE: IC-2340H UHF Transmit
« Reply #2 on: July 14, 2014, 07:32:05 AM »

It could either be the driver MRF 559 or more likely the SC-1054 module. Another possibility would be the RX/TX switching.
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AD5QA

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RE: IC-2340H UHF Transmit
« Reply #3 on: July 28, 2014, 08:19:56 PM »

Thanks,

I just cracked it open and looking into it a little more. I don't think it is the module and may seem to be the driver or something. When I key down the radio does not even attempt to transmit on UHF. The VHF works and sounds fine putting out 50 watts. The fan in the rear was defaulted as off and I reversed that as it was warm just receiving. I grabbed the datasheet for the Q08 MRF599 and will probe around tomorrow to see if I get any readings. Just downloaded the service manual and found that the MRF599 is not expensive. If that is a common failure then that will be my starting point. Will measure and find out if that is bad or not. If not I will have fun tracing it down lol, will look closer for any heat damage. I hope I remember to grab my IR thermometer from work tomorrow.

http://pdf1.alldatasheet.com/datasheet-pdf/view/76514/MICROSEMI/MRF559.html

Tom AD5QA
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KA4POL

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RE: IC-2340H UHF Transmit
« Reply #4 on: July 28, 2014, 09:43:34 PM »

what do you mean by 'does not even attempt to transmit'? It does switch to TX, doesn't it?
You could use an RF detector, just a diode and C, to find out if there is RF going to the module.
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AD5QA

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RE: IC-2340H UHF Transmit
« Reply #5 on: July 29, 2014, 07:49:57 AM »

I may have to try that. It has been awhile since I played with electronics and I need to get my tools back. When I press the PTT the radio does not attempt to change state at all. I am also thinking that it may not be getting a signal to transmit. I just need to isolate the problematic board from the service manual, maybe hit some test points. Right now I only have a multimeter and very few spare parts. I don't even have my logic probe and signal generator all thrown out/sold. Since joining the Military in 1997 I haven't tinkered much at all. Those electronic courses I took in school/college still reside in my memory though which is good.

I do miss troubleshooting and fixing stuff so I am slowly buying all new equipment. I am looking at a few cool portable oscilloscopes  now available for a decent price.

Tom
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KA4POL

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RE: IC-2340H UHF Transmit
« Reply #6 on: July 29, 2014, 09:00:57 AM »

Check the PTT switch first. You may carefully bridge the respective contacts on the connector in the radio to see what happens.
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KB4VVE

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RE: IC-2340H UHF Transmit
« Reply #7 on: August 10, 2014, 03:31:19 PM »

Had a couple of those.  V/U circuit seems to fail a lot, won't switch to UHF at all, no freq control, etc.
First see if you can get the band switch to function.
Greg KB4VVE 
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AD5QA

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RE: IC-2340H UHF Transmit
« Reply #8 on: August 10, 2014, 05:09:53 PM »

Band switch works fine and receive works as well. Just no xmit on UHF. I passed it to the side for a bit after taking out about 30 screws to get to the mic circuit on the Logic board. With all that surface mount and cross tracing I went cross eyed. So I put it to the side as work got crazy. Will take another look on my free weekend. Need to check out Q23/Q11 on the PTT circuit.
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KA5IPF

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RE: IC-2340H UHF Transmit
« Reply #9 on: August 11, 2014, 05:44:00 AM »

Why are you doing that? The PTT circuit is the same for both bands and it works on VHF. IF it's not going into TX on UHF most likely a PLL is unlocked and telling that to the processor and it will not allow TX. Check the 440 PLL circuit first for an unlock condition.
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AD5QA

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RE: IC-2340H UHF Transmit
« Reply #10 on: August 11, 2014, 06:38:36 AM »

Will do, that actually makes sense especially the way it seems to be functioning. I will check it out tonight if I get a chance. Thanks
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