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Radio Newbie in need of some guidance for an 84 - Printable Version

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RE: Radio Newbie in need of some guidance for an 84 - jerryhawthorne - 01-16-2015

Nice if you could sign off on a thread with your first name. If your not planning on doing a lot of radios (we all say that at the first), a dim bulb will do nicely with a 60 watt light bulb. If it gets really bright at first fire up and does not dim down, unplug! I would still want to hear from you on resistance to ground from the 10mfd wire to the speaker. It shouldn't result in the smoking of the cap but could cause problems with the rectifier and power transformer.
I would not worry much about various resistances to the chassis from ground points, the measurements you indicated could be nothing more than a bad meter connection.
Jerry

RE: Radio Newbie in need of some guidance for an 84 - rciancia - 01-16-2015

Jerry,
Here is the reading (Ohms) from the positive side of the 10uf Cap to chassis ground. 29.84K ohms.
I am building a Dim Bulb tester tomorrow and have ordered a variac as suggested.

Sorry for the delay in my response.

Ron

RE: Radio Newbie in need of some guidance for an 84 - LASJayhawk - 01-17-2015

(01-16-2015, 06:55 PM)rciancia Wrote:  Interesting... the testing I have done shows when I clip the wire to the lamp, the rest of the chassis will go down to zero after a beep on the continuity test.  My bulb setup is odd... only 1 wire goes to it... on my other chassis, there are 2 wires..  thoughts ?


https://pbs.twimg.com/media/B7gZkSnIcAAX2E9.jpg
Unless there is a change to the 84 that I'm missing, that pilot light arrangement will be dim, and should add some hum to the audio as well.

I would leave the bulb out until we get the radio playing.

RE: Radio Newbie in need of some guidance for an 84 - rciancia - 01-17-2015

Thank you John, makes sense and will do I just completed building my dim bulb tester ( and it works beautifully with a radio I restored the case on prior to the 84). The Variac will arrive tomorrow so after I am done rewiring my 84, I will have those two tools to help me prevent blowing the caps and damaging the transformer.

Many thanks
Ron

RE: Radio Newbie in need of some guidance for an 84 - codefox1 - 01-17-2015

Well, you can test a transformer when it is "out of the chassis" by hooking up the primary wnding, and carefully testing all the secondary windings. Your high voltage readings should be just about equal compared to the center tap. Hooked up this way with no load, there should be little if any heat build up. Additionally, most (but not every transformer) does not have any windings connected to the shell.

RE: Radio Newbie in need of some guidance for an 84 - rciancia - 01-17-2015

Codefox, I have done that and it checks out as good.

I have come across something that I am not sure is normal or matters. With all wires, caps and resistors removed from my chassis ( a bare chassis) , I have been checking for shorts around the tube sockets. I am finding that the 42 tube socket only has continuity from ONE of the rivets to the chassis, on one of the 77's neither rivet has continuity. I would expect that these rivets would give me a reading since they rivet directly to the chassis. Does this create a problem and if so, I assume the solution is removing the rivets with a Dremel tool and using screws/nuts?

EDIT UPDATE - I took an AWL and inserted it in the rivets that were not grounded and spun them. This has corrected the problem with continuity and now all my tube sockets show good continuity to the chassis. Only question that remains is , what problem would this cause, except for possibly some hum (whenever I get this radio working) Icon_smile


Thanks Ron

RE: Radio Newbie in need of some guidance for an 84 - rciancia - 01-18-2015

Well friends, I have a good update. After rewiring my unit and correcting the resistor, and socket grounds I am happy to report my radio works. Just went thru the alignment procedure and I am getting stations clear and loud.

As far as root cause I suspect my problem was the IF transformer. It was in very bad shape in my unit, so I swapped it with the unit from my parts chassis and all is well.

I can not express enough gratitude for all of your help here, it is truly appreciated.

https://pbs.twimg.com/media/B7pmz67IAAAMHZr.jpg

Now on to my next project which is an Atwater Kent 854 which is in very bad shape ( rubber wire insulators)

Many Many Thanks
Ron

RE: Radio Newbie in need of some guidance for an 84 - klondike98 - 01-18-2015

Congrats!! Nice work  Icon_clap Icon_clap Icon_clap

RE: Radio Newbie in need of some guidance for an 84 - KCMike - 01-18-2015

Been following your posts through out . Glad to hear you got it fixed. Good job of staying with it.