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zenith: 8S463 alignment question

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » zenith: 8S463 alignment question
           
Tom Mitchell
 
 
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14.Feb.20 03:32
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I'm aligning my 8S463 and I ran into an issue during the alignment. I followed the alignment instructions and I connected the generator to the grid of the 6A8G converter and I was able to align all of the sections ABCD, etc.

 

My problem is, The alignment seems to be on target, but when going to the standard band, and trying to pick up radio signals, I recieve them, but they're full of static, or muffled. I added a bluetooth module to the audio section, and the audio I stream send into the radio is fine. I think the problem is 1232 RF area. 

 

I'm going to double check my wiring tomorrow, but the schematic shows the switches in the "police" position. I have Auto, STD, short wave, and medium wave. Is it safe to assume that the medium wave is "police"?

 

The antenna switch on the schematic shows it's in the wavemagnet position, but I don't have a wavemagnet switch on my radio or wavemagnet itself.  I have a 5 pin wavemegnet connector witht he center pin being ground.  Should I just ignore it?

 

Thanks

 

 

Tom Mitchell
 
 
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15.Feb.20 00:41
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I reviewed the schematic and I had 1 capacitor the wrong value in the area of the 1232 tube. I went through  the alignment again, and I feel that it was the best alignment I've gone though for the radio. But, the radio still isn't working.

 

The problem that I have is there's a station in our area WJR that's at 760 AM, but it shows up at around 880AM, and it sounds like it's off-tune too. I'm stumped. I walked away to clear my head.

 

I'm using a Heathkit signal generator, and the output isn't a pure sinewave. Maybe that's it?

 

Any ideas?????

Daniel Best
 
 
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19.Feb.20 22:48

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Hi Tom,

considering the problem you described, it's likely there is still something wrong with the RF frontend.

The frontend alignment is apparently off by 120kHz, that can't be right.

Check all the voltages on the converter tube, just to make sure the biasing is right.

Re-check the alignment of the IF strip. You should have good response on the IF frequency of 455kHz, and only on that frequency. Make sure the IF strip has no sporadic response on any other frequency than that.

Only then you can start doing a proper frontend alignment.

Make sure you are not overloading the frontend while aligning it. The generator wants to be loosely coupled into the device under test, try not to connect it directly with a cable, because that could falsify the result.

Your radio should pick up the generator even if it is just sitting on the bench next to it with a short wire antenna.

Also, what antenna are you using on the radio? I don't know how Zenith built it, but unless you have a ferrite rod antenna, you probably need an external antenna of some sort. You can try to connect a random wire antenna to the grid of the converter tube, see if the reception gets better with that. Connect it through a small capacitor (10-100pF).

Kind regards

D.B.

Tom Mitchell
 
 
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20.Feb.20 04:09
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I have it working properly now. I'm not 100% sure what I did. I did found that the padder capacitor was loose. I went through the alignment for A B C and D trimmers, then did some minor tweeks on I believe it was F. I used my VTVM and went through the IF stages to get it alignened.

 

I'm not 100% satisfied with the final result, but it's close enough for now. I can receive AM stations, but the short and medium waves are pretty much empty anyway.

 

I need to put it aside and go onto another project.

 

Thanks for the assistance.

  
rmXorg