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Author Topic: Calling all FT 736r Experts  (Read 985 times)
WB7TSO
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Posts: 34




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« on: April 07, 2013, 04:12:27 PM »

I need some help with my yaesu FT736r. This is a rather strange situation that has me scratching my head. Here goes the rig works perfect on 2m all modes. On 430-450 it fails to open up any local repeaters that require a tone. I tested it with my HT and it will work on decode not break the squelch unless the HT transmits the correct tone. If I open the repeater with the HT first and the key up the yaesu I can hear myself coming out of the repeater. So i'm 99% sure it is an isolated issue with the encode tone only on 440 go figure. Any helpful ideas before I tear into the rig and start randomly wiggling wires. I have the schematics and I'm at a loss to understand why it would work on 2m and not 440.

Thanks Brad WB7TSO  Huh
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KE3WD
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Posts: 5689




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« Reply #1 on: April 07, 2013, 04:17:21 PM »

The rig uses one PL tone generator that is fed to two different circuits. 

Looks like, for some reason, the PL tone is getting to the right place in the 2 meter circuit, but something is stopping the show at the 70cm circuit. 

This could be anything from a dirty internal adjustment pot to a bad connection to a bad ground at the board screws or possibly a bad component. 

Service Manual, Schematic, signal trace.  Oscilloscope handy but not essential.


73
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WB7TSO
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Posts: 34




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« Reply #2 on: April 07, 2013, 04:49:28 PM »

KE3WD:

 The plot thickens a little. I in a slight fit of frustration I keyed the microphone about 10 times in a row as fast I could and once out of about 3 bursts of 10 clicks I got it to open the repeater. Hence I think you might be onto something. I am very suspicious of connectors since I had a grad school prof. who constantly was pulling his computer apart and cleaning connections (it used 8" floppys). I'm very close to just opening her up and getting started. I just bought the rig from another ham who tested it before shipping and it was working just fine for him. Any additional ideas would be great from the group.

Thanks Again

Brad Smiley
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K1ZJH
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Posts: 1185




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« Reply #3 on: April 07, 2013, 05:34:23 PM »

Sounds like the PL level might be set just a bit too on 440 MHz. If it works after you key up the repeater with a HT, then I'd guess it is a PL deviation problem. Best way to check it is to find someone with a deviation or service monitor to verify that the PL level is at 600 Hz deviation.


Pete
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WB2WIK
Member

Posts: 20666




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« Reply #4 on: April 08, 2013, 03:42:59 PM »

Remember the memories store everything including the TX/RX frequencies as well as mode, CTCSS activation, CTCSS tone, etc.

When you programmed the rig for 440 MHz did you remember to set everything up correctly in VFO mode first, before storing all the data into the memories?

Also be sure you're not in FM-N (FM "narrow" mode), that won't have sufficient deviation...
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WB7TSO
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Posts: 34




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« Reply #5 on: April 08, 2013, 04:17:39 PM »

Thanks for the suggestion. I called Bud this morning at ARS come to find out he is right down the street from me. He also suggested that I try and tune slightly off frequency to see if that opens the repeater since he thinks that the rig might slightly off frequency. Thanks for the idea about the memory and yes I did try that using both the Mem and VFO to see if I could get either one to work (no luck when I was right on the repeater frequency). I'll try Bud's suggestion when I get home.

Thanks

Brad Smiley
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WB2WIK
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Posts: 20666




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« Reply #6 on: April 09, 2013, 09:31:27 AM »

Thanks for the suggestion. I called Bud this morning at ARS come to find out he is right down the street from me. He also suggested that I try and tune slightly off frequency to see if that opens the repeater since he thinks that the rig might slightly off frequency. Thanks for the idea about the memory and yes I did try that using both the Mem and VFO to see if I could get either one to work (no luck when I was right on the repeater frequency). I'll try Bud's suggestion when I get home.

Thanks

Brad Smiley

The 736R has a discriminator meter built-in as a standard feature.  You'll know if the rig is "off frequency" compared with the repeater by just selecting that function (DISC/ALC - it's a discriminator meter on RX and an ALC meter on TX) and tuning in the repeater in VFO mode.  When the meter is exactly "centered," you're tuned dead-on its frequency.  When you transmit with the standard offset, your transmitter will be 5.000 MHz offset.  If you find your dial reads the frequency the repeater is "supposed to be" on when you zero the meter, then there is no "off frequency" problem.
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