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model 18 no reception - Printable Version

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RE: model 18 no reception - Radioroslyn - 02-04-2018

Methinks it's your osc coil. In a perfect world when you rewound the feedback or tickler winding you would have use the same size wire, # of turns and the same direction. If you didn't then this could cause your problem.
I'd pop it back out and add a few turns and see if that helps. The direction is critical. Gauge of the wire not so much original was 38ga. You can get away with use a size or two larger. # of turns = the original # but if it doesn't oscillate across the whole band add some more like 3 or 4 more.

GL

RE: model 18 no reception - madsowry - 02-04-2018

Thanks Terry   I will rewind it and not that I know even what I'm doing I agree after the 2 radio test it has to be the oscillator coil.  I rewound it before using 40 gauge and 17 wraps.  So if I wrap 19 or 20 will that be sufficient or just play with it with jumpers until I get a full dial?  Thanks

Dick

RE: model 18 no reception - madsowry - 02-05-2018

Hi guys   I took the oscillator coil out and rewound the feedback winding with 40 gauge wire for 20 wraps.  Put it back in and now I get reception up all the way but very low volume and a lot of interference.  Wondering if I should do more wraps or check something else.  Thanks

Dick

RE: model 18 no reception - Radioroslyn - 02-05-2018

Would align the rf, mixer, and oscillator sections the be sure that they are tracking properly.

RE: model 18 no reception - madsowry - 02-05-2018

I aligned it as best I could.  I hooked everything up as they say and hooked the out put meter to the output trans. and the meter was at halfway across the dial.  But my SG seems to be at full attenuation all the time.  I can't turn it down cause its all the way down now.  Without that the meter stays in 1 spot no matter how much you move the condensers.  Could this thing be stuck in AVC or is my SG screwed up.  At the low end of the dial I get blasted out by one station and can't hardly hear any other stations.  Might just stick this one on the shelf and try something else.  Thanks

Dick

RE: model 18 no reception - madsowry - 02-06-2018

Question:  Do tube shields have to have a solid connection to the chassis?  If chassis and shields are painted would that interfere with the shields function.  Also what's the best way to clean socket contacts-- Electric parts cleaner or Deoxit?

Thanks for any replies

madsowry

RE: model 18 no reception - morzh - 02-06-2018

Yes shields should have good connection to the chassis.

To clean sockets....fine grit sand paper rolled into tight matchstick size tube, or slim fine file, if really oxidized, otherwise Deoxit D series.

RE: model 18 no reception - madsowry - 02-07-2018

Thanks morzh  Trying everything I can think of.  Going back and check all cap and resistor values.

Dick

RE: model 18 no reception - madsowry - 02-09-2018

Hey  I have another mod.18 chassis that I'm going to restore along with the one I'm working on.  Originally the volume control on #1 chassis was stuck so I tried the one from #2 chassis.  It was stuck too.  So I opened it up and found out how it works.  Sprayed wd40 in both and got both working.  Put back together and #1 measures 1M.  #2 measures .5M.  They have the same part #.  The part # is not on Chuck's site so I don't know which is correct.  Any advice would be appreciated.

Dick

RE: model 18 no reception - Radioroslyn - 02-09-2018

According to the schematic neither. It shows a 350K taped @75K.
In the scheme of things both should work fine as long as the carbon track isn't cracked or badly worn.

http://www.theoldradiofixerupperguy.com/pdf/Philco/model18.pdf
NA copy stinks.

RE: model 18 no reception - madsowry - 02-09-2018

Thanks Terry  I don't know how to measure them for that result but if they will work that's fine.  I'm  planning on recapping and checking all resistors in chassis #2.  Already ohmed out coils,  the choke,  input trans. and output trans.  They all check out now.  Next I'm checking power trans. and if this one works then I'm thinking it's got to be the oscillator coil in chassis #1. Thanks for your help.

Dick

RE: model 18 no reception - Radioroslyn - 02-10-2018

>I don't know how to measure them for that result
Simple way is to use an analog ohm meter connected to center and one of the end terminal on the volume control. With the meter set for the proper range the needle on the meter should move nice and smooth as you rotate the shaft on the control. If the needle moves erratically it indicates that the carbon track is worn out and will not work properly.
 GL

RE: model 18 no reception - madsowry - 02-12-2018

Thanks Terry   Another question- this mod 18 chassis #2 has had the ecaps changed some time in the past.  They are Sprague 16uf.  The spec calls for 8uf.  These actually measure 15.8 and 12.5.  Should these be replaced?  Thanks for your thoughts

Dick

RE: model 18 no reception - Radioroslyn - 02-12-2018

I would just change them out especially if they are the older style in the cardboard tubes. Those are from the 70's or earlier. It's cheap insurance plus it can save you some troubleshooting later. Have had sets w/ odd symptoms like noisy audio but all the voltages look good. Rebuild the ecaps and all is good. To be clear these would be later model sets from the 50's and 60's w/twist lock caps.

RE: model 18 no reception - madsowry - 02-23-2018

Hey   I have a question after reading about safety caps in the line filtering.  I've restored a 90 and 2 18s and I've noticed the line filter caps are all .015uf.  The new safety caps only come in a few values.  Can we just go to the safety cap nearest the original schematic value i.e.  .01 for .015?  Thanks for any responses

Dick