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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Sep Sun 17, 2017 3:24 am 
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Joined: Mar Mon 20, 2017 7:42 pm
Posts: 10
Hello all,

My apologies for taking so long in this but between my mom turning 70 and a friend of mine now turning 50 I have been a bit slow and responding but I have more questions. I have an RCA signal generator that was a kit that people used to build when RCA was offering electronics courses. Now the signal generator has two functions. One is what is labeled as an RF output and I can match perfectly a 455 khz signal on my BK Precision 1805 Frequency counter.

Now the other function is the AF output which is controlled by an AF Mod/Int Mod switch above it which I believe puts out a signal but unfortunately I don't know what it is since my frequency counter doesn't tell me but it works as I have used it on the radio at the grids of my 6sc7 tube, the 6k6 tube and the detector tube at the plates which is the 6h6 tube respectively. When I inject a signal with the AF/output signal on those grids (and the 6h6's plates) I get a clear loud sound. Even when I put the injected signal into the volume control I get a sound that is loud and clear as well as controllable when I play with the vol control. So the back end has noise and works, hooray at this point.

But it's when I try to go back to the 455 khz signal over to the grids of the other tubes in the signal chain I hear nothing. Now I have the dial set at 1.0 on band 1 on the dial as I am not sure where to put the thing to have it set. I hear no sound at all, no 455 khz sound at all so I am unsure what to either check or do next. Just from my description it seems like it is the front end that needs to be checked but how? My instinct tells me that it is probably in the IF cans that are severely off and need realignment but are their other things to check out first before I go into that area? I can't reset the IF cans only because I accidentally ran over my plastic IF tweaker tools with my chair which has wheels on it so I have to get a new set first before I do anything else.

Onward and upward in this saga of first time radio alignment. Learning but hungry for understanding at this point. :-)

Dennis


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Nov Sun 26, 2017 2:33 am 
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Joined: May Mon 13, 2013 8:58 pm
Posts: 7
Hello to everyone here,


A bit of an update is in order. I decided to look into more visual methods of instruction. Whilst perusing on Youtube I found the site of Bretts Old Radios. He carries videos on DVD on how to do radio restoration, one dvd being on aligning an old tube radio.
So I purchased the item and watched it a few times. I also contacted him about the DVD and tossed a few questions at him. He is a wealth of information and where I was struggling with this he pointed me in a few directions. Here is some of the stuff I did.

1. Check the orientation of my I.F. Cans. Using my junker s40b as reference as my pics that I took were okay but not as informative as I'd like. I came to the conclusion that one of the Cans was put in wrong. I then preceded to put the offending one right.

2. Rechecked my soldering in some areas. This can plague even the most careful of people so on a lark I decided to get down with the schematic and check areas and through that I cleaned up some of my bad cold jointed soldering. When I tested the AF tone on my RCA Signal Generator it sounded better than it did when tested earlier.

3. Reinstalled the remaining I.F. Cans from the junker into this radio. That might seem controversial in some ways but I had done my original ones on a bench putting a 455 kc signal into one side and peaked them with an O'scope. I figured that the better way to do this was to use the other ones as they tested good and put them in correctly. Those hadn't been fiddled with so at least I can get into the ball park with this.

Using the standard dummy load I then put the high size of the signal generator on the middle
of the tuning stator and then proceeded to inject a signal into the radio. Nothing, then at the beginning occurred to my surprise. I then started working the tuning knob and then low and behold I got a sound. An actual sound from my signal generator out the end of my speaker. Hooray for now, but I have an issue with that success. The dial says that I am under 1000 kc which it was set for before I injected the signal into it. I only hear it when it is at a couple of bars before 1000 kc. Where are the trimmers for the osc trimmer in this thing to move closer to the frequency that is being 1000 kc and not slightly past .9 on my dial? Are they refering to the tuning caps under the radio or are there some on the tuning cap itself?

Any help is greatly appreciated as I'm getting there but slowly. :)

Dennis


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