eHam

eHam Forums => Mods And Repairs => Topic started by: K8AEC on June 21, 2012, 06:36:42 AM



Title: FT-450D receive problem
Post by: K8AEC on June 21, 2012, 06:36:42 AM
Greetings,

   Here is my problem:

The other day I switched to my CB radio from the FT-450D (i use a standard switchbox).   I use the HF on 20m with an A-99.   I made sure the HF rig was off, then switched the to the CB (the A-99 in use).
   I talked for a few minutes, then realized I hadn't re-tuned the tuner for 11 meters, which no doubt caused a high SWR.   I didn't key down very long and it was a short conversation.   A few hours later I switched the box back to the FT-450D and noticed the receive on 20m was lower than normal.  
     Could I have somehow damaged the FT-450D with a high SWR on the CB?   I've tried a direct connection to the 450D and the A-99 and do not notice a difference in signal strength than when the A-99 is running through the tuner.   Or has 20m prop just been bad for the last few days?

   You input would be appreciated.

Scott E. Fields, K8AEC


Title: RE: FT-450D receive problem
Post by: N4ATS on June 21, 2012, 07:41:35 AM
If you download the service manual for the FT-450 (its free all over the place, just google it) you will see on the IF board , near J-2001 , 2 protection diodes D2001 and D2002 , you probably shorted them out with front end harmonic overload. Then if that does not fix it , replace the FET preamps

First thng to do is throw out the MFJ switchbox (worthless) , get an Alpha Delta...


Title: RE: FT-450D receive problem
Post by: K8AEC on June 22, 2012, 08:35:13 AM
So even though the rig was not powered on and bypassed by the switchbox it can be damaged?

Wow...that stinks.


Title: RE: FT-450D receive problem
Post by: N4ATS on June 23, 2012, 04:58:41 AM
You bet , what kind of switchbox do you have? MFJ?


Title: RE: FT-450D receive problem
Post by: KA4POL on June 23, 2012, 10:11:37 PM
So even though the rig was not powered on and bypassed by the switchbox it can be damaged?

How do you think your microwave works? Put a diode inside and switch it on. You'll do that at your own risk  ;D


Title: RE: FT-450D receive problem
Post by: K7KBN on June 24, 2012, 04:25:16 PM
So even though the rig was not powered on and bypassed by the switchbox it can be damaged?

Wow...that stinks.

Obviously, it wasn't bypassed all that much.  N4ATS gave you good info regarding your switchbox.


Title: RE: FT-450D receive problem
Post by: K8AEC on June 27, 2012, 06:27:24 AM
Thanks so much for the info.

Took the radio to field day and put it on the meter; as expected, the diodes were dead.

It's only going to be a $40 repair, so lesson learned.

And the switch box is an old, unlabeled one.   A CB throw-back.

Needless to say, I won't be using it anymore.

Again, thanks SO much for the correct info.


Title: RE: FT-450D receive problem
Post by: N4ATS on June 27, 2012, 04:56:32 PM
Anytime....


Title: RE: FT-450D receive problem
Post by: K8AEC on October 28, 2012, 10:50:33 AM
Update:

The protection diodes were in fact blown.   However, replacement of the diodes did not fix the problem.
The radio was returned to Yaesu for a warrenty repair.
It turns out that the finals were blown...I was shocked.

I can only assume that there was a defect.

The radio is back in the shack and working flawlessly; as a matter of fact I just hit the 100 DXCC mark yesterday.

I'm going to add a TenTec 715 speech processor soon as I don't have the cash for a proper amp...none of that RM Italy crap.

Thanks for all the Elmer advice.

73,

K8AEC