Being an "Elmer"......

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Being an "Elmer"......

Post by Wildcat445 on Sat Jul 04, 2015 12:03 pm

........is not as easy as it looks.

I have a neighbor who is trying to get into old radios, specifically Hallicrafters. You may recall that I did an old S-38C for him a year or so ago. He wants to start tinkering on his own, and asked if I'd help him. I was fortunate to have two "Elmers" in my lifetime, so it is only right that I should pay it forward.

He bought a Hallicrafters 406 chassis on ebay. The schematic is in Riders 19-36, if you would care to refer to it. By the look of the faceplate, the console this chassis came from was fairly nice. There is some hack work that has been done on this chassis. Nothing major, but it needs to be corrected. The red flag for me was that the 5Y3 rectifier was missing. And there is black tape on all the wires to the power transformer. All the caps and resistors are original with the exception of the filter caps. The input filter cap is listed as 60uf @450 volts, which is a fairly uncommon value. Someone has used a 40uf paralleled with a 20uf in another can. The main problem with this chassis is that there is no B+. No B+ even on the cathode of the rectifier. It appears to have an open in B+ somewhere, so there is no current draw on the cathode. I have never run across this trouble in all my years of messing with radios. Short, yes, but never an apparent open. Thinking that perhaps there was a short somewhere, I disconnected the first filter cap from the circuit and still no B+ at the rectifier cathode. My thinking, based on what I have seen here, is that somebody had a problem with no B+, gave up, and just parted the set out. Really unfortunate if it was as nice as the faceplate. It is a SW, AM, FM chassis with a phono input and originally equipped with a 12" PM speaker.

So my first foray into being an Elmer has resulted in a radio that is a problem child. This should make an interesting project. I have to remain optimistic and produce results so that the neighbor does not become discouraged. His name is Frank. A retired truck driver. We are going to get this chassis going and restored then he is going to build a cabinet of some sort to house it. He has fun DX'ing with his S38 and wanted an FM receiver. Stay tuned.

WC

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Re: Being an "Elmer"......

Post by Wildcat445 on Sat Jul 04, 2015 1:58 pm

Power transformer! Bummer! Crying or Very sad

I got to checking this thing a little better and found the secondary of the power transformer partially or totally shorted. I had been checking at relatively low voltage, on the order of 70 volts. I decided to crank up the voltage to around 100. The dim bulb lit fairly brightly. I removed the rectifier, and it was still bright. I removed all the tubes, and the dial bulbs. Still bright. Then I checked from the PT center tap to both sides, at the rectifier plates. I had 350 volts (approx.) on one, and 50 volts (approx.) on the other. Further checking revealed the 330 ohm, 2 watt cathode bypass resistor burnt in two. The cathode bypass cap was completely gone, evidenced by the ends of the wires being still there. Why someone cut it out, who knows. This thing suffered a catastrophic meltdown and it was sold rather than repaired. This is a tough way for a newbie to get broken in. It needs a power transformer and one of everything. There is a 470 K ohm resistor burnt going to one of the 6SQ7 audio tubes. That may have stopped B+ to those tubes, but should not kill B+ totally. We will have to go component by component checking this chassis thoroughly. IF the decision is made to replace the power transformer.

WC

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Re: Being an "Elmer"......

Post by Bill Cahill on Sat Jul 04, 2015 3:43 pm

Taps time....................................................

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Re: Being an "Elmer"......

Post by Wildcat445 on Sat Jul 04, 2015 4:25 pm

I am officially in the market for a transformer for this thing. Hallicrafters part number 52C-153. One that is not toasted. Thank you.

WC

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Re: Being an "Elmer"......

Post by willy3486 on Sat Jul 04, 2015 10:01 pm

I had a few elmers that helped me. Mostly with going by and getting parts and stories of the old days. I got a lot of books and such. My elmers were TV shop guys and there wasn't any money in tube stuff. So I got a lot of parts and books. I would mostly try to teach myself.

Now I try to help others. One fellow I am helping is into taking late 50s/early 60s stereos apart for the amps. He wants to set them up as stand alone amps. I suggested just finding amps or building one from scratch using plans from the web. I am not into redesigning this stuff to work and don't like it. I do try to help. My problem with being an elmer is not that I don't want to its that I have little free time. I let him know in the summer I have no free time. Due to grass cutting every other week and my garden I have no free time.

I have needed to look for parts for him to see if I have any. I have been meaning to do so for a few weeks but I have been tied up. I have been on vacation since a week ago Thursday and haven't even looked at my own stuff. Anyway good luck with being a Elmer but don't let it take over so you have no time for your own projects.

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Re: Being an "Elmer"......

Post by Wildcat445 on Sun Jul 05, 2015 10:26 pm

While we are discussing a fried power transformer, let me add one tidbit of information. This chassis was "protected" by a fuse. The fuse is still perfectly good, while the transformer it is there to protect, got fried.

WC

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Re: Being an "Elmer"......

Post by Bill Cahill on Mon Jul 06, 2015 8:46 am

That often is the case... Fuses don't guarantee the transformer will survive....
In cheaper sets, especially, power transformers were wound as cheaply as possible. Of course, I've seen them fried in radios such as Edison as well. That paper filter shorts, and, you have instant smoke out of the transformer...........

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Re: Being an "Elmer"......

Post by Greg Davis on Mon Jul 06, 2015 9:30 am

I've never really had an Elmer, as such. Nobody I knew ever had any interest in electronics. Nice to see how modern day mentors share their skills. Good on ya!
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Re: Being an "Elmer"......

Post by Wildcat445 on Mon Jul 06, 2015 10:33 am

I've been blessed with two GOOD Elmers. One, my step-dad was a WW2 Navy-trained electronics technician who had a TV repair shop. The other was an electrical engineer who worked in the aircraft industry. The two of them never met. Besides being electronic geniuses with the patience of Job, they also shared the same birthday, August 25. One was born in 1924, the other in 1934. Both are gone now and I still miss them. Forums like this are the modern Elmers, I reckon. I'm glad to have somebody to tinker with.

WC

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Re: Being an "Elmer"......

Post by 75X11 on Mon Jul 06, 2015 2:42 pm

Be sure to check Ebay and go at it with 2 or 3 different search keys. There are usually a few up for sale.
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