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Ubitx receive intermittent

M0CLS
 

Hi, 

The receive on my ubitx has gone very intermittent! One minute everything is coming in strong then all of a sudden it drops out and stronger stations are in the noise then back again. More often than not the receiver is deaf! I had problems with this last week after I soldered coax to R43 and C32 and it turned out R43 went bad. I replaced it and all has been fine since. Then this morning it  started again, although this time R43 is fine. But I have just noticed I have continuity over a lot of resistors in that area of the board including over both ends on r43?? If I have a short somewhere where do I start?? Would it even power up and work at all if this was the case? 

Help would be much appresciated! 

Carl.

Daniel Conklin <danconklin2@...>
 

Intermittent issues are hard to diagnose because they never show up when the technician is looking for them.  You have to force the issue.  As you check for continuity, you wiggle and flex the PCB and other suspect things until the problem rears its ugly head.
Dan, W2DLC

ajparent1/kb1gmx
 

From R43 to C32, Is this a uBitx or bitx40?

What mod involves the emitter resistor of q40(R43) and output capacitor(C32) of Q32 in the 12mhz IF???


Allison

Daniel Conklin <danconklin2@...>
 

Allison I think he's trying the SDR function of Ian's firmware  That taps off the IF to feed an SDR dongle. 

M0CLS
 

Daniel is right, I was tapping off the IF for the RTL dongle.... 

Unfortunately the radio is now only transmitting .5w too! Today I will test the finals although there is no point replacing them until I can find out why my receive is so intermittent. I do hear stations still, they are just much quieter when it cuts out. So maybe this is an audio amp issue and not a sensitivity fault. 

Carl.

 

Carl, gently shake the toroids and see. Tap the relays with the handle end of a small screwdriver and check.

Coil solder has been known to be occasionally bad. Relays also go bad..

Raj

At 01-07-18, you wrote:
Daniel is right, I was tapping off the IF for the RTL dongle....

Unfortunately the radio is now only transmitting .5w too! Today I will test the finals although there is no point replacing them until I can find out why my receive is so intermittent. I do hear stations still, they are just much quieter when it cuts out. So maybe this is an audio amp issue and not a sensitivity fault.

Carl.

M0CLS
 

I fixed the low power issue. It was down to the thick wire I had going from the Neg terminal of the power plug to the rear chassis bolt?? Anyway I removed this and power jumped back up.

The audio is a separate issue. As I said, I believe it is audio and not signal related as when it drops out I still receive signals only much quieter. My board is a later v3 with socketed audio chip. I wonder if I tap off the back of the volume control to a separate amplifier? 

Carl.

John Wulf
 

I had a similar problem where w1aw at 10 over would fade out to the point where I could no longer copy them on cw. Worked fine with headphones plugged. Replaced the 2 inch speaker and ok now.
73 John K4FT