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Author Topic: Restoring a Hallicrafters S-108  (Read 3996 times)
W2EAF
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Posts: 19




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« on: January 16, 2011, 09:02:16 PM »

I just picked up an S-108 on Ebay really cheap. Cosmetically, it looks almost brand new, no rust, peeling paint or dings. It seems to have been barely used over the past 50+ years. Electronically, however, it is in sorry shape. The sensitivity is very poor, the controls are very scratchy, and the audio is horribly distorted.

So, what would be the best course of action? A "shotgun" replacement of all caps for starters? Retubing? I have the manual, thanks to BAMA.

I have a soft spot in my heart for Hallicrafters, since it was my Dad's S-38 that got me started in the first place.

Rob, W2EAF
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AC5UP
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Posts: 3872




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« Reply #1 on: January 16, 2011, 10:12:05 PM »

If it doesn't hum with the volume turned all the way down I wouldn't automatically replace the power supply electrolytics. For the distorted audio C64, the 10uf electrolytic on the cathode of the 6K6, is probably your prime suspect. You will replace the PS filter caps before all is said & done, but for now I suggest you start by cleaning all switches and potentiometers. DeOxit is a perennial favorite for this but I've had good luck with CRC 2-26 clean & lube (it's like WD-40 but much better for electrical contacts). Don't forget to clean the tube sockets.

Next step is a functional check. Do all controls operate (mostly) as expected? Can you hear something on each band? If something doesn't work at all troubleshoot the section. If the radio works, but poorly, run through the voltage and resistance checks in the Hallicrafters service manual. This would probably be the point where you'd replace the filter electrolytics, because if something is too far out of spec you'll need to figure out why and troubleshooting a chassis with a soft power supply is a huge waste of time....

Last item would be replacing tubes as needed followed by an alignment, then I'd consider any cosmetics that need a little TLC.

UPDATE: This is to correct a typo. The clean & lube I like is CRC 2-26 (not 2-56)... This stuff: http://www.crcindustries.com/ei/content/prod_detail.aspx?PN=02005&S=Y
« Last Edit: January 17, 2011, 07:45:20 PM by AC5UP » Logged

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KE3WD
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Posts: 5689




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« Reply #2 on: January 17, 2011, 05:25:59 AM »

Very first thing - clean and lube all controls and switches w/Deoxit.  Work them while still wetted, ten to twenty times, full travel each, such that the wiping action can mechanically clean the contact surfaces before the first part of the chemical can evaporate. 

Then see how the receiver works from there. 

It may just need nothing else at all.


73
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KF6KXG
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Posts: 7




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« Reply #3 on: January 17, 2011, 08:51:49 PM »

Another "first" thing to do is to remove each tube one at a time and spritz the sockets lightly with DeOxit. The tube pin contact points get oxidized after a while. BTW, replace all electrolytics now rather than later, as they could take out the power transformer if they fail and that is an expensive fix. 73 Mike KF6KXG
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N4NYY
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Posts: 4758




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« Reply #4 on: January 18, 2011, 11:06:58 AM »

I always recap. There are pro and anti recapping guys. I am pro. Regarding the carbon composite resistors, I measure several at random. If they are close or slightly over the 10% tolerance, I let them be. If you find a few that are 25-50% of tolerance, I replace them all.

As far as Deoxit, this is the one you want: http://www.google.com/search?sourceid=navclient&aq=hts&oq=&ie=UTF-8&rlz=1T4ACAW_en___US371&q=DeoxIT+D100S-2

It is solvent free and has a timed burst, unlike WD-40. It won't keep spraying. Deoxit is a must have for anyone with a bench, and should be the first thing you do, before recapping or replacing resistors.
« Last Edit: January 18, 2011, 11:11:01 AM by N4NYY » Logged
W2EAF
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Posts: 19




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« Reply #5 on: January 19, 2011, 12:27:22 AM »

Thanks for all the tips! By the way, I also should mention that the receiver has a loud hiss in the audio, even with the volume turned down. In increases as the sensitivity control is advanced, and it is really drowning out the signals.

I'll be rolling up my sleeves this weekend to clean, lubricate, and start some cap replacements.
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KD0FAT
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Posts: 64




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« Reply #6 on: January 19, 2011, 06:24:24 AM »

Sounds like something getting into the front end--the RF amplifier section? Try pulling the RF amp tube out while listening to the hiss. If it still hisses, the problem is in the IF channel or the audio amp. Or could it be local RFI? Are you working next to a wall wart, dimmer switch, compact fluorescent? Does the hiss go away at frequencies above 10 mhz?  73, Al
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N4NYY
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« Reply #7 on: January 19, 2011, 09:01:53 AM »

Definitely start with the Deoxit first. You might have to Deoxit some of the tube sockets, too. Start with the pots, switches, and then move to the sockets. When you spray the sockets, seat seat and unseat the tubes a couple times, to work in the deoxit.
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N8CMQ
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Posts: 362




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« Reply #8 on: January 29, 2011, 04:10:38 AM »

If your radio is hissing with no antenna connected, and it increases with the sensitivity pot, look for an oscillating stage. I would suspect a cap is dried out and not neutralising the stage. Kinda like a regen set, with no signal...
And I prefer Deoxit D5, it has a nice tube to direct the spray. Or I apply it to a Q-tip and wipe an edge connector with it. Good stuff!
Hope you are having fun restoring the old girl! I am still working on my SX-101, and loving every minute I get to work on it!
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