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48-200 code121 Filament Wiring incorrect - Printable Version

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48-200 code121 Filament Wiring incorrect - Welder - 11-18-2017

I'm asking for help with the above problem.  I did a continuity check and all is well with the 14B6,14A7, and 7A8.  Things change with the pins on the 50L6GT  (2-7) and I found the filaments wired to the wrong pins and corrected same but now the rectifier 35Z5GT looks all wrong and I don't know where to start. What bothers me is that the soldering looks professional and can't understand why pins 1-8 would be occupied by other wires. I'm also a little Intimidated by all the resistors and caps buried near the rectifier and 50L6.  Is there a easier way to hook up the correct filaments without diving in with my soldering iron and such first ? By the way, I'm very impressed with this site and look forward to being an active  member.

Thank you, Icon_yawn

Welder

RE: 48-200 code121 Filament Wiring incorrect - morzh - 11-18-2017

Are you sure you have actual 50L6 in the radio?

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-18-2017

Morzh:

Sorry for the misinformation it's a 50A5.

Thanks for the reply

RE: 48-200 code121 Filament Wiring incorrect - Radioroslyn - 11-18-2017

Hi and welcome,
I think you'll find that for the most part loctal tubes the filament pins are on 1 and 8. Octals generally fils are across 2 and 7. There are exceptions like rectifier tubes, 12sq7's ect...

RE: 48-200 code121 Filament Wiring incorrect - klondike98 - 11-18-2017

Welcome to the Phorum!
Icon_wave

RE: 48-200 code121 Filament Wiring incorrect - morzh - 11-18-2017

Well, 50A5 and 50L6 are the same tube with different bases: the former is loctal and the other is octal. The sch calls for the latter and you have the former, hence the confusion.
I don't know if there was a version that used 50A5, some radios were like that, but see what you have first.

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-18-2017

Thanks, we'll try it.

Welder

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-20-2017

I now have a pilot light (1100) that lights but as soon as I bring up the variac past 15-20 volts the bulb burns out.  I found the right pins for the filaments on the rectifier 35Z5 but I had filaments only for awhile until I decided to solder two disconnected wires which I thought were wrong:  First I moved R204 to pin 8 (50A5) because R204 was burning and R102 back to it's original position off Pin 8 (35Z5) along with one of the positive legs of the electrolytic.  In any event, I have a light acting as a fuse but still no filaments. Both tubes appear to be good.  Any help would be appreciated.   

Welder

Thanks for the warm welcome!  Icon_evil

RE: 48-200 code121 Filament Wiring incorrect - Radioroslyn - 11-20-2017

Did you have while you were jugging wires around apply the filament voltage to the + side of the electrolytic cap?? If you did it toasted, ecaps will short if ac voltage is applied to them. If it still has the original caps in it replace them.

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-20-2017

Terry, thanks for your reply.  I probably did apply AC to the cap(s).  I converted the single three way cap to three new smaller cans.  I'll check them and replace as necessary.  I did a messy job anyway with all the leads being bare.  When I was checking voltages the tip of my meter lead did touch one of the + cap wires while I was checking the filament voltage and the pilot light came on several times before it blew. 

Welder

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-20-2017

The electrolytic caps (3) all check out okay but bulbs continue to blow past 30 volts on the variac.  I have one pos + from the electrolytic that I desoldered and of course can't remember where it belongs on the rectifier.  I'm recording everything I do now.  I'm new at this and find it's very easy to get confused! I can't raise the voltage enough to get the filaments to light. Something is amiss but I'll read the sch. and go from there.  Any suggestions would be apprecated. Just a note, Icon_clap Icon_clap  I replaced the 30, 25 & 20 Microfarad 3 lead cap with three (3)  33uf caps which was all I had at the time. I've ordered the correct caps from Just Radios.

Thanks, 






Rich

RE: 48-200 code121 Filament Wiring incorrect - Arran - 11-21-2017

35Z5s, 35W4s, and 35Y4s, all have a pilot light tap on the filament, the pilot light has to be connected across this, usually in parallel with a 1 watt resistor. It might be popping because the pilot lamp is connected in parallel across the entire 35Z5 filament rather then just one end and the tap.
Regards
Arran

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-21-2017

Thanks for the info.  Makes sense and I'm getting low on bulbs. I'll let you know how I did.


Rich

RE: 48-200 code121 Filament Wiring incorrect - Radioroslyn - 11-21-2017

Hi Rich,
I noticed that no one posted the service info to your set  [Image: http://philcoradio.com/phorum/images/smilies/icon_rolleyes.gif] so here it is:  http://www.nostalgiaair.org/pagesbymodel/627/M0013627.pdf  For a lot of us old timers we sort of have these circuits memorized so we don't refer to them often.  It was a fairly common practice for manufacturers after the war as parts were difficult to source to interchange electrically equivalent tubes w/different sockets. The 35Y4, 35Z5, and 35W4 or the 50A5, 50B5, 50C5, and 50L6 are two of the common sets of tubes (rectifier and audio output) that can be used. Sometimes the schematic will display the one you have in your set. On Philco sets a code # like 121 or 122 along w/the model. The code may indicate a slight difference from the same model.

So here's a plan. Double check your ac and heater wiring for correctness with special care around pin 4 of the 35Y4 . Use your ohm meter to check the heater in the 35Y4 by seeing that pins 1,8,and 4 have a low resistance against each other. The capacitance value of the filters isn't very critical 33ufd is fine.

RE: 48-200 code121 Filament Wiring incorrect - Welder - 11-21-2017

Terry:  I was hoping I'd get a response like yours.  My sch. shows the 35Y4 and I'm having trouble following the pins 'cause it's a 35Z5.  I've been moving things around and got the pilot light working w/o burning it out but now resistor R102 (1200 ohms) is cooking when I crank it up to 110V.  I can't seem to find the right pin for the pos leg of one of the 33 uf caps ergo the burning resistor. I'll check resistance again. 

Thanks,
Rich