Browning Golden Eagle Receiver

[w5dud]

Have been working on this receiver and cannot seem to get the sensitivity that it should have, all voltages are good , changed all the paper caps,and at 50 mv I can only get an S-6-7, all tubes are good and new 6ds4,s have done an alignment as per book, I know I am missing something,first one in yrs that is this weak, also changed the Rf gain control, it was bad,my be in the S-meter circuit, Thanks W5DUD

[Marc]

I am not an expert like Fixr or 2600 but I would check r25 and the SR3 diode. Just a thought its a place to start.

Also check the voltage at pin 7 of V7 should be around 6V.

Marc

[FIXR]

I wouldn't worry about the "S" meter readings at this time. What is the negative voltage at the detector testpoint with 50 uV input at the antenna connector?
If lower then -9 V, then I would change L2 first. This is the 18 uH choke right before the first 6DS4.

Fixr

[w5dud]

Thanks to both replys I will try , and let you know, Thanks

[Marc]

Fixr where is that test point??

Marc

[FIXR]

Marc,

VTVM between ground and the junction of R38, R39, R46 and C40.

Fixr

[Marc]

Thanks put it in my file.

Marc

[Sandbagger]

Mar 24, 2010 11:54:44 GMT -5 w5dud said:

Have been working on this receiver and cannot seem to get the sensitivity that it should have, all voltages are good , changed all the paper caps,and at 50 mv I can only get an S-6-7, all tubes are good and new 6ds4,s have done an alignment as per book, I know I am missing something,first one in yrs that is this weak, also changed the Rf gain control, it was bad,my be in the S-meter circuit, Thanks W5DUD

How weak is it? My MKIII had me pulling hairs for a while because the sensitivity was off, but not really bad. I was getting about 1 uV for a 6db S/N, which is weak for a Browning, but not something which would be easy to spot as you went through the receiver chain. Finally, I was fortunate to come across another receiver, which was working fine, that I could do a side-side comparison with. Long story short, it turned out that L2 on the RF front end had changed value. I've never had a choke change value before so it surprised me. I'm guessing these parts get hammered by lightning strikes or near miss strikes.

Also, since there is no S-Meter adjustment (other than a zero), the accuracy and linearity of the meter depends largely on the gain and cutoff of the tubes. My original 6DS4 ended up having great sensitivity, but a 50 uV signal would show +20db over S9. I replaced the tube with a new one, and the sensitivity remained the same, but the S meter now correctly read S9 with that 50uV signal. Overload on really strong signals seems to have been cured as well.

[w5dud]

Thanks for all the info, tested voltage at test point last nite and after adjusting got over -5v, but voltage on pin 2 of the 6al5 was only -2v, L-2 is ok did not check the value,at .25 uv there is a good sig,but S-Ometer is only showing s-6 with 50uv at ant,this is a Mk II rec ,it is in great shape I am going to replace the 6al5 later and ck the diff,

[2600]

I have come to associate a bad L2 with erratic behavior from the S-meter.

Turning up the signal generator level smoothly should get you a smooth rise in the S-meter reading. If it 'hangs', and won't advance much past S-4 below 100 uV or so, and then JUMPS suddenly up to a 20-over reading, that is almost certainly caused ba a damaged L2.

I chalk that one up to a "near-miss" lightning surge. Even if the lightning strike is a couple of houses up the street, a beam antenna will collect a big pulse of RF energy. Enough to darken the windings on L1, or to create hidden damage inside L2. Leaving the antennal connected during storm season is russian roulette. A ground plane can bring a damaging surge down the coax during a storm, too, even if it doesn't strike your antenna directly.

Since the normal circuit current through this part is pretty low, this is the only explanation I can see, especially if you see the color of the wires in the middle of L1 darker than the ends.

I would be more incilned to blame a "K-Tran" If or RF transformer going bad. Some of the tuning slugs in the radio will normally have a broad peak when they are tuned. Others should show one that is really sharp.

But a tuning slug that shows NO peak at all is suspect. Only takes one of them going bad to lose a few S-units on the meter, and make a weak singal hard to hear.

No easy fix for these when they inevitably go bad. A K-Tran coil will have only a slot for a screwdriver-tip tool visible under the adjustment hole.

The newer, more-reliable parts have the familiar six-sided hollow hole in the tuning slug. They fail far, far less often.

73

[mark4]

I just finished building a Mark IV.
last one ever. I had a NOS Mark IV receiver about 3 years ago.
It had low receive. But not that far off.
went through my old e-mails and found one from 2600.
At 1uv my S meter would not move maybe a hair. I changed out L102 and now I have 1 1/2 S units with 1uv. I gave up on this board because I never checked it at lower signal level.
I did not experience the jump in readings at 100uv.
But it would act crazy sometimes with no signal and jump up to 9 S units. This had just started. Now it's fixed and works perfectly.