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 Post subject: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Mon 20, 2017 8:14 pm 
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Hello all,

I purchased a Hallicrafters S40-B general coverage radio that I've been restoring to hopefully use for many years to come. My problem stems from when I was trying to align the thing. I had stations that would come in with my primitive antenna and that was okay. Nothing on Band 4 mind you but the others I could find a strong station or two. This was after I had replaced two faulty tubes and did a recap using Hayseed Hamfests recap kit. The recap kit was awesome and I highly recommend it versus just buying separate individual caps. I also did the usual check and change out of tolerance resistors, which I found many in this set, and for a short time all seemed well apart from an alignment which needed to be done due to the recapping although I did hear what was sounding like crashing sounds like something out of a thunderstorm.

Having said this here is where the dilemma started. I started to peak the coils as per alignment instructions. T2, the IF Can which goes by the number S3 and S4 arched a little when I was peaking them and then no sound reception was heard thereafter. Reading about the dreaded Silver Mica Disease I set about to investigate it that was was causing the problem. Sure enough it was rearing its ugly head in this IF Can so I removed the mica slabs and put two 100 pf caps in its place. I did a bit of searching and that what I am understanding to be the right values for that IF can. If I'm in error on this then by all means please correct me as to the right values or near to them. I also put the caps in the IF Can instead of outside of the can as that is how I read to do the procedure. I kinda wished, looking back on it all, that I had put them on the outside of the can but my own cockiness can sometimes get the best of me some days. :-(

Once that was done now I still don't have any radio sounds coming from the unit regardless of which way I try to peak the coils with my rca tube signal generator set at 455 kc as per directions. So at this point I am a bit lost as how to proceed so any help or sites to point me out to would be wonderful as I am not sure what do do next nor check next. I have also a tube signal tracer and I do have an Oscilloscope although I am not familiar how to use it yet (it is a Conar Model 255 solid state unit).

Thanks in Advance:
Dennis Perusse

ps The IF Can# is 50C243.


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Mon 20, 2017 10:18 pm 
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Dennis,

It is possible a wire was knocked loose inside the transformer during repair. Check for plate voltage at the plate of V3 (pin 8 ) and with the power off and the AVC switch off measure the resistance from V4 pin 4 (control grid) to ground, it should be 150 ohms or less.

I generally put replacement capacitors inside of the IF can so there is nothing wrong with doing it that way and it looks neater.

Rodger WQ9E


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Tue 21, 2017 10:51 pm 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1350
Location: Rochester, NY.
If the short knocked out an IF coil, you might find a good used part. The 1st and 2nd IF was part # 50C243 and the DET/IF xformer was 50C242.
If it was a B+ short to ground it could have damaged an adjacent tube. Best to use a non-conducting tool in these.
I don't know if WZ1M (Gary) has really retired yet, but he has them still listed if you want to send an email:
http://wz1m.xfrmrs.com/id118.html


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Wed 22, 2017 2:10 am 
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Joined: Mar Mon 20, 2017 7:42 pm
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Hello all,

Okay, sorry for my delay in responding back but here are some numbers.
I checked out the voltage on the plate of v3 and it was 6.6 mv. The ohms for pin 4 was 160.
Just for giggles I checked the plate on v4 and it was 309 volts. I also tested the tube in v3 and it tests okay. Not sure what to troubleshoot next so any advice is welcomed. :)

Dennis Perusse


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Wed 22, 2017 2:16 am 
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Dennis,

You should have B+ voltage on the plate so either the transformer primary winding is open or there is a fault preventing voltage from getting to the primary winding. I would start by checking for continuity of the IF transformer primary and if it is open you will need to investigate whether it is a broken wire at the terminal (probably repairable) or a winding that burned open due to a shorted capacitor (probably not repairable thus requiring a replacement IF transformer).

Rodger WQ9E


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Fri 24, 2017 12:18 am 
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Joined: Mar Mon 20, 2017 7:42 pm
Posts: 10
Hello,

Okay I checked the continuity on the if can and yes it is open on one side.
Looks like I'm going to have to get one to replace the open one. The other cans are okay. I appreciate all the help from everyone on this issue. A parts hunting I go. :)

Dennis Perusse


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Fri 24, 2017 12:23 am 
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Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Dennis Perusse wrote:
Hello,

Okay I checked the continuity on the if can and yes it is open on one side.
Looks like I'm going to have to get one to replace the open one. The other cans are okay. I appreciate all the help from everyone on this issue. A parts hunting I go. :)

Dennis Perusse



Before you go hunting ....

Maybe take the can apart and have a look to see if you disconnected one of the coil wires on the open side. If it was working after a fashion before, then quit, it's likely something simple like a broken wire. If you can see the break, maybe you can solder it back together. It doesn't have to be pretty inside the can ... it just has to have continuity.

cheers

_________________
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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Fri 24, 2017 1:23 am 
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As John stated it is likely the transformer can be repaired if a wire broke at the connecting point. To make it easier for a repair like this I solder a solid copper wire stub to the terminal and use the extra length of that to connect to the broken end.

The transformer is likely wound with Litzendraht (aka Litz) wire and Google will lead you to a number of different methods of prepping the end for solder if the broken part makes that necessary.

Rodger WQ9E


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Fri 24, 2017 10:14 pm 
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Joined: Mar Mon 20, 2017 7:42 pm
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Hello,

I removed and inspected the IF Can and found the break.
I must have been ratcheting the slug too much as the break
is on the coil form itself. Not sure if I can repair or not.


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Fri 24, 2017 10:47 pm 
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Breaks on the outside of the winding are almost always repairable. If the coil form itself came loose use a good epoxy to anchor it back in place before repairing the broken winding.

If the wire broke right at the winding carefully free a little bit of wire so that you can make a connection, a small amount of winding loss won't make any difference. Solder a new extension wire from the transformer pin to where the break is and after making a solder joint drip a small amount of molten wax to immobilize the new connection and anchor it to the coil form/winding.

Use a good magnifier if needed to aid you in freeing the wire and making a good connection.

I have repaired quite a few broken windings this way; proceed carefully and you should be successful.

Rodger WQ9E


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Sat 25, 2017 11:52 pm 
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Joined: Mar Mon 20, 2017 7:42 pm
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Hey,


Silly question but is the 50C242 and the 50C243 if can the same can or am I mistaken?
Also can anyone recommend a brand of if can tweaker where the Velma's one I have I'm rather unhappy with.

Dennis Perusse


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Sun 26, 2017 12:22 am 
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Dennis,

The 242 and 243 suffix cans are different. The 243 is a typical plate to grid transformer while the 242 is designed as a plate to detector transformer and they are designed for different load impedances.

I acquired a big set of GC Electronics alignment tools in a pouch that I like but there are many good choices. The less expensive ones tend to wear rapidly.

Rodger WQ9E


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Thu 30, 2017 11:24 pm 
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Hello everyone,

Okay, a quick update. I managed to re inspect the IF Can but it's
ready to be replaced as it was far more damaged than I thought.
Now I know that their are various models that share similar parts.
So my question is which model of S38 uses those those IF Cans?
I mention this as I see plenty of s38 parts machines that look like
I could grab a part from one of them. I know that the Sx-177 uses them, the 8r10, another
S40-b as well. I do fully want to thank everyone on this list for helping me figure this out, especially Roger for the quick replies.

Dennis


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Mar Fri 31, 2017 5:15 am 
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Joined: Jul Sat 23, 2011 9:33 pm
Posts: 792
Location: Long Beach Ms. USA 39560
If you replace the IF can, check first to see if the "new" can needs the silver-mica-disease fixed.
I have a simple way that worked for me.
The mica plate has two caps on it. Top and bottom on each side are one cap.
The side that connects to the plate circuit has B+ on it, and the side that connects to the grid or detector has nearly ground.
The difference in voltage on=top-to-top and bottom-to-bottom across the dividing gap causes the silver to grow small spikes and create the shorts you hear burning out.
If you can remove the mica, you can run a scribe between the top two silver areas and the bottom two areas. Then put a small amount of nonconductive paint in the groove. Bend the contacts back and reassemble. That way the value of the capacitors stays right and the paint or epoxy will prevent regrowing the spikes.
Good luck,
Pat

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Unhappy tubes blush while unhappy power FETs scatter plastic


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Aug Tue 22, 2017 11:41 pm 
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Hello everyone, update in this saga of repair.

I finally got an S40B for parts and took one of the 50C243 IF cans and installed it in. I know that it is a good part as it has continuity and I was able to peak it manually with my signal generator with a frequency counter on one end and an o'scope on the other end of it. I've also been changing out resistors that we're out of tolerance as well as there were a few.

My problem is that I now still have no sound at all and I have no clue as what to do next. I've checked all my tubes and they are okay. So can anyone here point out what I should try out next in terms of trouble shooting? Should I start doing voltage readings on the tubes in circuit at all? Any help is greatly appreciated.

Dennis


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Aug Wed 23, 2017 4:17 am 
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By no sound, do you mean no static or stations, or is that any sound at all?

1.) Clean the headphone jack. The sound has to travel through contacts in the jack to get to the speaker--or try some headphones and see if you hear sound.
2.) Touch the wiper (center contact ) of the audio volume control with a screwdriver. Don't short out anything, but you should hear a sound (hum) from the speaker.
3.) Try connecting the signal generator at 455 KHZ with the modulation on (40%) to pin 5 of V7. Use a .01 600 volt cap between the signal generator and the radio. Slowly turn up the amplitude until you hear a tone from the speaker.

Good luck and have fun. The solutions to these problems are always obvious-- but not until after you discover them.

Norm

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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Aug Thu 24, 2017 2:39 pm 
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Connect your scope to pin 4 of V4. Apply 455Khz to pin 4 of V3.
If T2 primary and secondary winding's are good you should see the RF sine wave on your scope.

I agree with the suggestion touching the center tab on the volume control with your finger.
This should produce a hum in the speaker.

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Mike RMC(SW) USN Retired
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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Aug Fri 25, 2017 1:59 am 
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Hello all,

Let me give some clarity here as I reread my own posting and thought it unclear too. I have no sound, just hum from the speaker. No stations on any band, nothing. I did try to put my finger on the vol center lug and it did get louder, so a result there. I also tried to put through a signal on my rca signal generator on v3 and the scope on v4 but no real clear sign wave on it. I am using my brothers tectronix 465 scope as mine is not working right now.

So something else is afoot here but not sure on anything yet.

Dennis

Oh, btw, I have continuity on all the IF Cans so that can be ruled out. The tubes are all good as tested on my Heathkit tc-1 tester. I appreciate all the help so far but this stumping me at this point. I also tested some earbuds, with an adaptor, on the headphone jack an nothing either.


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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Aug Fri 25, 2017 2:36 am 
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Normally you should start at the speaker and work toward the antenna. You have determined that the audio is functioning when you touched the volume control and the hum increased. Next step is to move to the other side of the detector. You want to use the signal generator at the grids of the tubes except the detector (V7 pin 5) where you will inject at the plate. The amplitude of the signal generator will be greatest at the detector and should decrease as you work toward the antenna. You will use a modulated 455 KHz signal from the detector plate all the way back to the mixer grid. From there you will use a specific frequency that the dial is tuned to and move to the antenna connection at the rear of the chassis. A few microvolts is normal there, but sometimes it takes much more if the radio is way out of alignment. The oscilloscope is not necessary. The point is to hear the tone from the signal generator coming from the speaker. That will tell you the radio is working. Once you have determined that a modulated tone applied to the antenna can be heard from the speaker, then you can connect something to tell you where the peak is as you adjust the transformers, and trimmers and follow the alignment protocol for your receiver.

Norm

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 Post subject: Re: Hallicrafters S-40B, no sound, IF Can issue
PostPosted: Aug Sun 27, 2017 1:57 am 
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Hello all,

I'll try that tomorrow when I get a moment. I'll let you know the results when I get it done. :)


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