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GE 115 troubleshooting - Printable Version

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GE 115 troubleshooting - Eric - 04-22-2016

I have a GE 115   http://www.nostalgiaair.org/pagesbymodel/591/M0007591.pdf

I have recapped and replaced any resistors out of spec. also replaced the vol pot they had a 150k in there instead of a 500k, Checked the tubes and there good. Did an alignment per the instruction I get a lot of stations but they all sound ragged (my term) or over modulated. I did a voltage check and all the numbers come in 15/20%. I did the Voltage check with the gang closed and the vol at min. I have also changed all the tubes as I had spares but it made no difference so I put the originals back.
  Now the original with the loop was gone but I have a back with loop from another GE 423   http://www.nostalgiaair.org/pagesbymodel/675/M0007675.pdf
Will this work? What am I missing?

Eric

RE: GE 115 troubleshooting - Eliot Ness - 04-22-2016

Here are new clickable links:

http://www.nostalgiaair.org/pagesbymodel/591/M0007591.pdf

http://www.nostalgiaair.org/pagesbymodel/675/M0007675.pdf

If all the caps have been replaced as well as out-of-spec resistors, your voltages are good, and you subbed out all the tubes that only leaves the speaker or output transformer.  Have you ohmed that out yet?

Years ago I was tearing my hair out on a Zenith console that was distorting and the speaker looked perfect.  Just for grins I grabbed another speaker out of a parts set I had and it sounded wonderful.  Since then I found an old speaker substitution box at a radio show, and while I don't use it very often, it was well worth the $10 or $20 I paid for it.

Not sure about subbing those antennas, but they are both listed at 2.5 ohms, although the one on the 115 looks like it has more windings.  You might try various lengths of long wire to see if it makes any difference or experiment making an antenna.  

RE: GE 115 troubleshooting - Eric - 04-22-2016

It has a perm magnet speaker and I have a few of those and have tried them and there is no change, I have not done anything with the output xformer other than checking resistance but since the radio does work not sure what else could be checked on the output xformer. I also have a wire running around my garage and use it as an antenna, the stations get louder but the distortion is still there. Even tried some other loops I had laying around but no changes. But I will take a closer look at the output xformer.

Eric

RE: GE 115 troubleshooting - Arran - 04-23-2016

 It could be that the 35L6 tube is gassy, that can cause the problem you described.
Regards
Arran

RE: GE 115 troubleshooting - Eric - 04-23-2016

Swapped out the 50L6 (not 35L6) no change. Any other Ideas?? I'm running out of thing to try!

RE: GE 115 troubleshooting - Radioroslyn - 04-23-2016

Hey Doc,
Measure the dc voltage from pin 5 of the 50L6 to pin 8. + to the p5 and - to p8. Should see about -10v.

Terry

RE: GE 115 troubleshooting - Eric - 04-23-2016

50L6 Pin 5 to pin 8 with 5 pin +lead I get -4.5vdc

RE: GE 115 troubleshooting - David - 04-23-2016

Eric might recheck R5,R6,R7,C9,C10,C11 and the solder connections. David

RE: GE 115 troubleshooting - Eric - 04-23-2016

Just did a quick check and the resistors are within 15% and they are connected per the print. The caps have been changed so I'm assuming the values for now are correct but I will check them when I re-solder the connections, and they are connected per the print. That will have to wait till Monday. Thanks for the Ideas.

Eric

RE: GE 115 troubleshooting - Joe Rossi - 04-24-2016

Did you do an alignment?  Have you checked the new volume control?  Could need cleaning.  I don't see on the schematic the value for R3.  I'm sure you have, but doesn't hurt to ask.

RE: GE 115 troubleshooting - David - 04-25-2016

15% on the resistors?  

RE: GE 115 troubleshooting - Eric - 04-26-2016

Did an alignment and I get a good selection of stations
R3 the vol is 500k I get 530k. I get good range of volume
Checked R5,6,7 with in 15% also checked through the solder connection at both ends and verified with print.
Checked C9,10,11, Lifted one end and verified the value and re-soldered.
I checked the IF coil and they are within a couple of ohms.
Still distorted...... I'd pull my hair out but it's already gone!

RE: GE 115 troubleshooting - Radioroslyn - 04-26-2016

(04-26-2016, 02:40 PM)Eric Wrote:  Did an alignment and I get a good selection of stations
R3 the vol is 500k I get 530k. I get good range of volume
Checked R5,6,7 with in 15% also checked through the solder connection at both ends and verified with print.
Checked C9,10,11, Lifted one end and verified the value and re-soldered.
I checked the IF coil and they are within a couple of ohms.
Still distorted...... I'd pull my hair out but it's already gone!

Ok so the next step is to get a signal tracer. Basically it's an audio amp with a switchable probe that can put the test signal straight through or through a small signal diode. What this will allow you to do is listen to each stage rf,if,and audio.So all you have to  do is  listen for the stage where the distortion is coming from. Also great for find which stages are working or not and which if transformer to replace when smd is a problem.
http://www.ohio.edu/people/postr/bapix/sigtrac2.htm

Now one other thought are we talking about about distortion or is the audio garbled sounding? Electrically these can be two different issues. A bad rf ground can cause the sound to be garbled(ac mixing into the control grid circuit) Open or bad connection at the loop antenna can do that.

GL
Terry

RE: GE 115 troubleshooting - gregb - 04-26-2016

Does the AVC voltage vary as you tune on and off a station? Check that on both the 12SA7 pin 8 and 12SK7 pin 4 tube, it should be a slightly negative value that goes more negative as a station is tuned in.
One of those two tubes could also be gassy and I would try the 12SK7 first.

Gregb

RE: GE 115 troubleshooting - Eric - 04-27-2016

The 12sa7 goes from a -.7 to -3 (distortion increases) but the 12sk7 is -.7 but the station is muted when I attach the probe and the value stays when I move off the station. I have changed both tubes but no change.
I do have a signal tracer that was given to me a Heathkit IT-5283 with probes doesn't look like it was used, but have never used it other than as an external pm speaker. looked at the inst online but it was less than clear( can only find a partial manual 9 pages)) to me like is the chassis energized? Hook the black lead to the antenna then probe with the prob with the diode selected on the probe?