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Author Topic: Icom ic 735  (Read 696 times)
DW7DVE
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Posts: 180




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« on: November 02, 2016, 03:57:34 AM »

I need your help again guys. Somebody is offering me an icom ic 735 for a good price. If it still works, I would probably buy it but I like to be able to go qrp or play with the mike gain. I don't see any controls that would allow for that. So here's the question, is there any way to control or adjust output and mic gain on the 735? Also, I can't see a vox switch. Do I have to key the transmit key each time I tx in CW mode?

Thanks in advance.
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W8JX
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Posts: 10035




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« Reply #1 on: November 02, 2016, 04:56:31 AM »

I need your help again guys. Somebody is offering me an icom ic 735 for a good price. If it still works, I would probably buy it but I like to be able to go qrp or play with the mike gain. I don't see any controls that would allow for that. So here's the question, is there any way to control or adjust output and mic gain on the 735? Also, I can't see a vox switch. Do I have to key the transmit key each time I tx in CW mode?

Thanks in advance.

It is not a big problem to overcome. Those rigs have a ALC jack on back and you can make a up a simple way to reduce power using it. Take a 9v battery and connect a 50k to 100k "pot" (variable resistor) across it. Connect the negative terminal to center conductor of RCA ALC jack and the shield/out shell wiper/variable tap on pot. This applies a variable negative bias to ALC jack and you can dial in your desired power level. (you should place a switch in series with pot connection across battery to extend battery life when not using it)

On CW, you can if you want but it is not needed if you want to operate semi break-in.

BTW the 735 is a nice classic rig. I have used one a few time in past.
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Ham since 1969....  Old School 20 WPM Extra
DW7DVE
Member

Posts: 180




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« Reply #2 on: November 02, 2016, 05:04:39 AM »


It is not a big problem to overcome. Those rigs have a ALC jack on back and you can make a up a simple way to reduce power using it. Take a 9v battery and connect a 50k to 100k "pot" (variable resistor) across it. Connect the negative terminal to center conductor of RCA ALC jack and the shield/out shell wiper/variable tap on pot. This applies a variable negative bias to ALC jack and you can dial in your desired power level. (you should place a switch in series with pot connection across battery to extend battery life when not using it)

On CW, you can if you want but it is not needed if you want to operate semi break-in.

BTW the 735 is a nice classic rig. I have used one a few time in past.

Thank you. That would be my last resort though. I would have infinitely preferred something along the lines of cutting a diode or something and having a knob on the rig adjust the power. If there's nothing else that can be done, I would probably go with the external control.
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W8JX
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Posts: 10035




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« Reply #3 on: November 02, 2016, 05:10:16 AM »

Thank you. That would be my last resort though. I would have infinitely preferred something along the lines of cutting a diode or something and having a knob on the rig adjust the power. If there's nothing else that can be done, I would probably go with the external control.

There id not other good option here. That ALC trick works with all those older SS rigs without power controls including even older tubed ones.
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Ham since 1969....  Old School 20 WPM Extra
DW7DVE
Member

Posts: 180




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« Reply #4 on: November 02, 2016, 05:26:02 AM »


There id not other good option here. That ALC trick works with all those older SS rigs without power controls including even older tubed ones.

Thanks again. 73
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N4OGW
Member

Posts: 414




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« Reply #5 on: November 02, 2016, 08:37:42 AM »

I need your help again guys. Somebody is offering me an icom ic 735 for a good price. If it still works, I would probably buy it but I like to be able to go qrp or play with the mike gain. I don't see any controls that would allow for that. So here's the question, is there any way to control or adjust output and mic gain on the 735? Also, I can't see a vox switch. Do I have to key the transmit key each time I tx in CW mode?

Thanks in advance.

I used a 735 for several years. Controls for all of those (RF power, mic gain, and vox) are under the little hinged plastic panel on the front.

Tor
N4OGW
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DW7DVE
Member

Posts: 180




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« Reply #6 on: November 02, 2016, 09:09:48 AM »


I used a 735 for several years. Controls for all of those (RF power, mic gain, and vox) are under the little hinged plastic panel on the front.

Tor
N4OGW


Ah, thanks. I was looking at the pic online and didn't notice that there were controls there. Smiley
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W8JX
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Posts: 10035




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« Reply #7 on: November 02, 2016, 10:41:14 AM »


I used a 735 for several years. Controls for all of those (RF power, mic gain, and vox) are under the little hinged plastic panel on the front.


Dah, I forgot all about that... The control under a flip down panel on 735.  It was a good solid rig in its day. Still a decent rig today if in good order.
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Ham since 1969....  Old School 20 WPM Extra
K0CBA
Member

Posts: 377




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« Reply #8 on: November 02, 2016, 11:55:52 AM »

The 735 was and still is a fine little radio that should do anything requested of it. Mine will be in my estate sale because I will never let it go and its my main HF rig.   I also have an IC 730....quad conversion receiver; FABULOUS!

If you get it for a good price and have any interest it CW, it would be well worth the money to get CW filter to put in. 

I have the Icom 250 Hz and like it a lot.  I believe Icom filters are no longer available so find a used one (NOT easy) or look at the selection of Inrads.  I  found a 400 Hz for the 730; I'd like a little tighter one but it was used at a real right price.

One sort of down side is the little green bulbs.  I got tired of trying to find them as they burnt out so I finally went the LED route.
I liked the green better but all in all a good trade off.

 
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W8JX
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Posts: 10035




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« Reply #9 on: November 02, 2016, 12:00:04 PM »


One sort of down side is the little green bulbs.  I got tired of trying to find them as they burnt out so I finally went the LED route. I liked the green better but all in all a good trade off.
 

Did you ever consider installing a small resistor to drop voltage a bit? That would extend bulb life considerably. 
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Ham since 1969....  Old School 20 WPM Extra
K0CBA
Member

Posts: 377




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« Reply #10 on: November 03, 2016, 08:02:15 AM »


One sort of down side is the little green bulbs.  I got tired of trying to find them as they burnt out so I finally went the LED route. I liked the green better but all in all a good trade off.
 

Did you ever consider installing a small resistor to drop voltage a bit? That would extend bulb life considerably. 

No need; there is already a dimmer control on the mic plug side of the rig.
 
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W8JX
Member

Posts: 10035




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« Reply #11 on: November 03, 2016, 08:14:44 AM »


One sort of down side is the little green bulbs.  I got tired of trying to find them as they burnt out so I finally went the LED route. I liked the green better but all in all a good trade off.
 

Did you ever consider installing a small resistor to drop voltage a bit? That would extend bulb life considerably. 

No need; there is already a dimmer control on the mic plug side of the rig.
 

Understand but it could still limit peak brightness and extend bulb life.
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Ham since 1969....  Old School 20 WPM Extra
DW7DVE
Member

Posts: 180




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« Reply #12 on: November 06, 2016, 03:35:05 AM »

Is this a good idea for reducing min output on the ic735? Or should I go with the potentiometer and 9v batt? Any downsides to the mod?

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W8JX
Member

Posts: 10035




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« Reply #13 on: November 06, 2016, 03:49:19 AM »

I see no down side to tweak of power level adjustments. With external 9v battery and pot the only downside is you need to replace battery every several months or so and it does not require opening up rig. If you use it often it may require sooner replacement. Put a switch in battery/pot circuit to shut it off when not using it.
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Ham since 1969....  Old School 20 WPM Extra
DW7DVE
Member

Posts: 180




Ignore
« Reply #14 on: November 06, 2016, 03:55:55 AM »

I see no down side to tweak of power level adjustments. With external 9v battery and pot the only downside is you need to replace battery every several months or so and it does not require opening up rig. If you use it often it may require sooner replacement. Put a switch in battery/pot circuit to shut it off when not using it.

Thank you.
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