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GE 107 wont start up - Printable Version

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RE: GE 107 wont start up - Tgace459 - 06-13-2016

(06-13-2016, 01:29 PM)Radioroslyn Wrote:  Just as an aside try measuring the resistance 35Z5 out of it's socket, pins 2,3,and 7 should show a low resistance to each other. The pilot lamp get it's power from a tap in the 35Z5 heater (pin3) if there is no resistance from pin 3 to 2 or 7 the lamp won't light but the power supply will make HV. Don't know if an open tap will show on the tube tester. This may solve your pilot lamp issue.

Gl
Terry

Thanks. I will do that when I get home today.

While I'm at it. Let me put up a couple of photos to see if things look right. I think someone did some work on this before it came to me....or the factory wiring is different from what I understand the schematics to mean...anyway.

This is the 35Z5:

[Image: http://i.imgur.com/9vEJIRq.jpg]

Now first excuse the sloppy solder job. That will be cleaned up.

What seems odd is that the power and bulb wire are supposed to attach to pin 2 according to the schematic, but is jumpered over to pin 4 with that wire and there's that other wire attached to pin 2 that goes off to something I can't recall. I'll have to check that when I get home, but I can't see that anything else is supposed to attach to that pin according to the schematic. Everything else looks logical compared to the schematic. Is this normal?

And when it comes to the switch this is how I received it:

[Image: http://i.imgur.com/w8rmDFI.jpg]

What I "think" is odd is how the switch is "grounded"/jumpered/wired to pin 8 of the 12SQ7 tube. If that is supposed to be the ground wire for that switch shouldn't it be attached to pin 1? That obviously looks like the ground since that wire running off of it is attached directly to the chassis.

RE: GE 107 wont start up - Radioroslyn - 06-13-2016

What I "think" is odd is how the switch is "grounded"/jumpered/wired to pin 8 of the 12SQ7 tube. If that is supposed to be the ground wire for that switch shouldn't be attached to pin 1? That obviously looks like the ground since that wire running off of it is attached directly to the chassis.

http://www.nostalgiaair.org/pagesbymodel/583/M0007583.pdf
Pin 8 of the 12SQ7 is one of the two pins connected to the heater it goes to the off/ on sw and is also B-. B- is floating in this set (not connected to the chassis as it would present a shock hazard). Chassis ground is connected to B- though C20 and R11 they provide a rf ground for the tubes shield on pin 1 of the metal tubes.
Check ur PM box.

Terry

RE: GE 107 wont start up - Tgace459 - 06-13-2016

Thanks. That's why I don't change anything before consulting people who know more than I. Icon_smile

Since I'm still a newb at this, I stick to the newb rules of changing out the electrolytic caps, trying a start-up then doing a cap at a time vs shotgunning all the caps. Is there any advantage to changing out the rest of the caps at this point?

And let me throw this out there too. When I got this radio the pilot lamp was blown. I picked up a bulb at radio shack and it fits and lights up when I run a 9v through it. Is it possible that the bulb is "wrong" or could be part of my problem?

RE: GE 107 wont start up - Radioroslyn - 06-13-2016

Yes, C-14,16,20,11,and 12.
When caps are leaky or shorted they can cause excessive
current flow lowering the HV among other things.
The burned out lamp could be from C-13 being shorted.
Hey wait just a minute! There's no lamp in the circuit!
Perhaps someone added it and miss wired it.Lamp
goes to pin 2 and 3 of the 35Z5 tube. The lamp socket
must be isolated from the chassis.
Terry

RE: GE 107 wont start up - Tgace459 - 06-13-2016

(06-13-2016, 05:25 PM)Radioroslyn Wrote:  Yes, C-14 looks like it's missing,16,20,11,and 12.
When casps are leaky or shorted they can cause excessive
current flow lowering the HV among other things.
The burned out lamp could be from C-13 being shorted.
Hey wait just a minute! There's no lamp in the circuit!
Perhaps someone added it and miss wired it.
Terry

The schematic im using shows it...if you go back to page 1 there is a link to it.

RE: GE 107 wont start up - Radioroslyn - 06-13-2016

Interesting, Riders doesn't show the lamp. So we back to c13 was shorted and took out the lamp or the heater tap is open.

Terry

RE: GE 107 wont start up - Tgace459 - 06-13-2016

(06-13-2016, 05:44 PM)Radioroslyn Wrote:  Interesting, Riders doesn't show the lamp. So we back to c13 was shorted and took out the lamp or the heater tap is open.

Terry

Something odd...

The schematic you showed me has no lamp, but a resistor running off of the plate (and back to the negative blade of the plug? I think?). I have a resistor attached to the plate and to Pin 3 as you see in the photo.

The schematic I'm using shows the lamp...but no resistor. I have a lamp AND a resistor. Is this set-up right?

RE: GE 107 wont start up - Tgace459 - 06-15-2016

What has me stumped for now is why the 35Z5 wont light up (pilot lamp or tube). I can light the bulb from the pins with a 9V and 2,3 and 7 show continuity between themselves. I'm getting voltage when I turn it on. But the bulb and tube stay dark....

RE: GE 107 wont start up - Radioroslyn - 06-15-2016

Sound like a bad heater in one of your tubes. Remove tubes, Measure resistance from pin 2 to pin 7 on all except on the  'SQ7 it's 7 and 8. Should show low resistance. 

Terry

RE: GE 107 wont start up - Tgace459 - 06-15-2016

Thanks! Think I may have found a or THE culprit....no 2-7 continuity on the 12SK7.

RE: GE 107 wont start up - Radioroslyn - 06-15-2016

Drop in another 12SK7 and that will get the heaters going again.

GL
Terry

RE: GE 107 wont start up - Tgace459 - 06-15-2016

Have one coming tomorrow hopefully.

Thanks for taking the time to answer my questions. It helps in more ways than one. Like understanding schematics better. Now that I look at the schematic I feel like a complete newb for not figuring that out for myself. The circuit goes through all the heaters so obviously if one is open the circuit isn't complete.

RE: GE 107 wont start up - gregb - 06-15-2016

Did I miss something here, I thought you had voltages on all of the tubes? That would be impossible if the filaments were not lighting up. Were the tubes lighting up and then they stopped?

Gregb

RE: GE 107 wont start up - Tgace459 - 06-16-2016

That was it!

Now I just have the antenna issue to figure out. The back with the antenna was toast on this thing.

The voltage thing. Looking back at the readings I posted it looks like some of the 2 and 7 pin readings were low (or non-existent) while others were giving readings. The voltage readings on the other pins I cant explain. I was still getting them as recently as yesterday.