Install "F" connector in a TU 717

seadzz

Active Member
I was thinking about installing a "F" connector into my TU 717 in an effort to eliminate some signal loss. It looks easy enough to do but I have a question.

Inside the tuner there is a internal balun. Do you hard-wire the "F" connector directly to the secondary side of that balun or do you keep using the internal balun?

Attached is the existing design and a modified drawing of what I have in mind. Will it fly?

sdz
 

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I usually request that my tech disconnect the balun if possible with the idea of increasing sensitivity. :scratch2: YMMV. Good luck!
 
That will work just fine, only hook it to the bulan if you plan ever using the 300 ohm input.

X
 
Well Punker I installed a F61 connecter and ran a short section of some shielded wire to the secondary side of L01. The results stinko. The signal strength on the TU 717's meter dropped from a "4" to a "3" on my fav station. I would have expected no degradation or maybe even a slight improvement in signal strength.

Are you sure I can directly connect to the top side of the capacitor C01 and feed the antanna signal directly into the FET that way or do I need to still utilize the internal balun? To the three or four brain cells I have left it would seem there should be a way to bypass the internal balun......just I don't know exactly how to make the connection.

Thoughts?

sdz
 
Do you have the original antenna connections hooked to the front-end still? A cable going from the bulan to the front end should go to two terminals on the frontend. Follow the ground back to the frontend. Sometimes soldered directly to the case of the fronend. Measuring either terminal to ground will read 0 ohms because you are just measuring the resistance of a coil.

What kind of impeadance does the shielded cable you using have. You should only use 75 ohm cable. You should just be able to disconnect the orginal antenna connections, solder the center conductor to the terminal 1 and the shield to terminal 2 or 3. You can take the original antenna connection and roll it up and use a tie wrap and put it out of the way. It would be out of the circuit and could be just cut out.

The antenna coil and cap may need to be tweaked to match the new 75 ohm connection. If you tune to a station near 106 and tweak the cap for highest signal reading, then tune to a station ear 90 and tweak the coil, it will get you really close.

X
 
Thanks Punker,

I ran the hot side of the F 61 connector to terminal 1 and the shield to ground. Left all OEM connections in place and the tuner works like a champ. I no longer have to fool around with the Rat Shack 75 ohm to 300 ohm transformer.

In retrospect the L01 transformer needs to be left in the circuit it seems afterall.

If no one told you you would think that "F" looks like it was factory installed.

Should any of you folks at home wish to do this upgrade to your tuner I have attached a "parts list". The first is a F 61 connector they come two to a pack. You need to drill a hole in the back of your tuner being careful not to rip into wires when the drill comes through the sheet metal. In the case of a TU 717 the back pannel is made from aluminum so opening the hole is a snap. First center punch a spot where you want to locate the connector then using a sharp 1/8 dia drill open a pilot hole. Next taking a larger diameter dril .3XX" open the correct mounting hole. The second item you will need to obtain is a length of shielded wire to run from the F connector to the PCB. I purchased one of these and just cut off the 1/8" plug and allagator clips. I cut the wire to length, solderede one end to the F connector and mounted the connector. Then routed the wire and soldered it to the correct terminal on the PCB.

No, there are no pictures I forgot to take them and the unit is all buttoned up now. Maybe next time I have the hood open.

sdz

Edit: If all of this seems like too much trouble you can just ship your tuner off to PunkerX and he can add the connector while he is aligning your tuner
 
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