The PHILCO Phorum
4th of July in 555 2nd IF can - Printable Version

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4th of July in 555 2nd IF can - OldRestorer - 04-27-2014

So I recapped my 555 today and put her back together. Brought her up and then i see sparks coming from the 2nf IF can. It was only a second when I bumped the chassis and then it stopped so I am a bit confused.
Does this mean that there is a short in the can? I tapped the can again and more sparks. she is unhooked till this is figured out.
Could this be the result of a short? the dial lamps are on but thats it. the tubes are all new and were tested.

Did I screw up the recapping?

Where should I start looking?

Any help is appreciated.

Kirk

RE: 4th of July in 555 2nd IF can - Ron Ramirez - 04-27-2014

What is a 555? Is this a Philco or ?

RE: 4th of July in 555 2nd IF can - Warren - 04-27-2014

Sounds to me like a loose wire or connection in that can. If when you move it the sparks start again then some thing there is shorting out.

RE: 4th of July in 555 2nd IF can - Steve Davis - 04-27-2014

Kirk, start by removing the IF transformer from the can. Look to see if one of the wires is touching the can.

Steve

RE: 4th of July in my Crosley 555 2nd IF can - OldRestorer - 04-27-2014

yeah I never remember that non philcos don't go here. It is a crosley 555.
sorry about that Ron. I will take off the can and check.
thanks
Kirk

RE: 4th of July in 555 2nd IF can - TA Forbes - 04-27-2014

Look for the origin of the sparks. Have the chassis on it's side if necessary and try to locate where it is coming from. It sounds like you either have two leads touching that shouldn't be or a lead grounded. B+ goes through the IF can to feed the plate of the previous tube.

Yes, good idea to go where you did work and look there.

RE: 4th of July in 555 2nd IF can - morzh - 04-27-2014

It is a little gremlin sitting inside the can and trying to spot-weld a loose connection. Tell him to get out but leave the welder.

RE: 4th of July in 555 2nd IF can - codefox1 - 04-28-2014

There should be a wee black spot and/or a blister on the aluminum where the fault occured. Sometmes not, just the lead dressing. Best of Luck.

RE: 4th of July in 555 2nd IF can - OldRestorer - 04-30-2014

Ok the IF cans are off and no burn marks on the can. They did stop sparking without the cans on though.
I will say some of the wires were close to each other and they are missing insulation.

this is what they look like:

RE: 4th of July in 555 2nd IF can - Mondial - 04-30-2014

That IF transformer looks pretty smoked. Do the coils still measure good as to continuity and proper resistance?

RE: 4th of July in 555 2nd IF can - codefox1 - 04-30-2014

Agree. schematic needed problem likely in primary circuit of IF.

RE: 4th of July in 555 2nd IF can - OldRestorer - 04-30-2014

I dont know how to check the IF. Thats where my problems are. I dont have the tools or the knowhow.

Sch here
http://www.nostalgiaair.org/PagesByModel/424/M0003424.pdf

RE: 4th of July in 555 2nd IF can - jerryhawthorne - 04-30-2014

OR, put your meter on the ohms scale and set it for the lowest resistance range. Place the leads across the tabs sticking up in your picture, one on each side of one of the trimmer cap. You should have a low resistance reading. Now go to the other trimmer cap and repeat, hopefully with the same results of a low reading. A high reading (probably in the megaohm range will indicate an open coil. Make sense?
Best, Jerry

RE: 4th of July in 555 2nd IF can - Raleigh - 05-05-2014

Do you have a schematic? Schematics often say what color wire is connected through the transformer windings to whatever other color of wire. Sometimes the resistance across the coils is also listed. Find those wires that are supposed to be connected and measure ohms between them. Resistance is usually in the low ohms (less than 5 or 10, sometimes less than 1.)

High resistance is a bad sign if the schematic shows connection. Zero resistance is also a bad sign. Your ohm meter will probably show .3 or .4 ohms with the leads shorted, so you should subtract that from the reading when measuring low resistance.

Then measure across leads that are not supposed to be connected. They should read completely open, and your meter should read exactly as it does when not connected to anything. Any resistance at all means a short, and is a bad sign.

In the picture some of the tiny black wires look like they have crumbling insulation on them. If there is any chance of them touching anything, unsolder one end of them and put a sleeve on them, very carefully. That'll make them better than new. The primary side wires have high voltage on them. They'll make sparks if they touch the can, and that will likely burn out some tiny wires you can't replace.

I've never done it myself, but I've heard of people painting little wires like that with some stuff made for the purpose instead of sleeving. I can't remember the name of it.