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-   -   GE L-660 tubes don't work. (http://www.videokarma.org/showthread.php?t=252615)

HiFiCanada 11-14-2011 03:27 AM

GE L-660 tubes don't work.
 
:scratch2:When I got the radio, I can easliy see that someone else has been working on it, but since that type of radio does not have a power transformer, I was not to worried about going ahead to recap.
I slowly powered it up on my variac, the dial light is on, but the tubes did not light up.
I checked all the tubes on my Heathkit TC-1 tube tester and they are all good, at least they all glow.
So my queston is that if all the tube glows on my tester, then if everything was OK in the radio, it should also light up.
I am a bit worried that a coil is open,the queston is that if a coil is open, should the tubes still light up?
http://i1042.photobucket.com/albums/...L-660radio.jpg

stusnyder 11-14-2011 03:58 AM

check your voltages at the tubes. I think that the tubes are wired in series with the power cord.

electroking 11-14-2011 11:14 AM

Hello,

No coil in this radio is related to the operation of the tube heaters. Here is simple
test you should try with the radio not connected to the power line.

1 - With the radio off, connect your ohmmeter to the prongs of the power cord.
You should get an infinite reading.

2 - Turn the power switch on. You should get some low reading (maybe a few tens
of ohms). You are now measuring the cold resistance of the tube heaters in
series. If you don't get a correct reading, something is wrong either with one
or more tube, or with the wiring to the tube heaters.

3 - Assuming you got a correct result in the previous step, pull any of the tubes.
You should get an infinite reading again.

By the way, tubes take a few seconds to light up, as you can verify when testing
them on your tube tester. Good luck!

P.S.: the pilot light is a 110 V unit directly connected to the line, so it may
light up even with something wrong with the tube heater circuit.

maxhifi 11-14-2011 11:19 AM

check that the tubes are in the right sockets - looks like you have the mixed up as per riders diagram on nostalgia air

bob91343 11-14-2011 12:15 PM

I agree with maxhifi. The lamp lights because it's connected directly to the power line, unlike most radios of that ilk, where it's on a heater tap of the rectifier tube.

If it has the tubes I think it has, the 12SA7 goes at the end next to the tuning capacitor. The next one, on the other side of the IF can, should be the 12SK7. After that comes the 12SQ7 and then the 50L6GT, with the 35Z5GT close to the panel.

maxhifi 11-14-2011 12:41 PM

if you look close, it has an rf preamp before the converter, the converter is hiding behind an if can

So it's sk, sa, sk, sq, then 50L6 and 35z5

But look for a tube location chart on the cabinet, or use the one on nostalgia air

Quote:

Originally Posted by bob91343 (Post 3018472)
I agree with maxhifi. The lamp lights because it's connected directly to the power line, unlike most radios of that ilk, where it's on a heater tap of the rectifier tube.

If it has the tubes I think it has, the 12SA7 goes at the end next to the tuning capacitor. The next one, on the other side of the IF can, should be the 12SK7. After that comes the 12SQ7 and then the 50L6GT, with the 35Z5GT close to the panel.


electroking 11-14-2011 01:10 PM

Yes, some tubes are definitely in the wrong places. See figure 1 in the following:

http://www.nostalgiaair.org/PagesByM...0/M0008190.pdf

holmesuser01 11-14-2011 02:16 PM

I just love these tube radios!

How was the 6 tube set better than the 5 tuber?

maxhifi 11-14-2011 02:49 PM

Quote:

Originally Posted by holmesuser01 (Post 3018485)
I just love these tube radios!

How was the 6 tube set better than the 5 tuber?

More sensitive front end. Better at receiving distant stations. Not much difference with locals.

electroking 11-14-2011 03:24 PM

I think the answer is not that much related to sensitivity. Your typical 5-tube radio
has enough gain to amplify the atmospheric noise to an uncomfortable level.
The advantage of a tuned RF stage is improved rejection of the image frequency,
which is useful when the band is open, or when you have a local station at or
near the image frequency of the weak station you are listening to. The image
frequency is 910 kHz above the actual setting of the dial. For instance, if
you set your radio for 660 kHz, you may be able to hear a station transmitting
on 1570 kHz. The RF stages will amplify much more at 660 than at 1570
under such conditions, thus improving the performance.

HiFiCanada 11-14-2011 05:09 PM

Tubes are in the wrong laces
 
Quote:

Originally Posted by maxhifi (Post 3018471)
check that the tubes are in the right sockets - looks like you have the mixed up as per riders diagram on nostalgia air

Wow, I am sure glad that I posted a picture.
Yes, all the tubes are all in the wrong places and I would have never thought that the diagram was wrong. So now I can't trust the the schematics. I changed all the tubes around , according to the label underneath the cabinet and slowly turned the power back up with the variac and all the tubes light up.
Now I have a lot of hum, and if I just touch or tap the rectifier tube 35Z5 it almost sounds like I am taping a microphone. If I just tap it, the hum is louder and then just press on the tube, the hum gets a bit softer again.
The whole radio is recapped except two of the molded caps and I have not check the wiring to the schematic to see if it is all that it should be. I recapped the radio exactly to each capacitor what was in the radio, one by one, so I did not make a mistake unless it was wrong before.
I am getting zero radio reception and I may just try some other tubes from my stash.

electroking 11-14-2011 05:27 PM

Hum means plate voltage is present, and the output tube (35L6GT) is working.
You're on the right path, keep up the work!

maxhifi 11-14-2011 09:53 PM

Quote:

Originally Posted by electroking (Post 3018489)
I think the answer is not that much related to sensitivity. Your typical 5-tube radio
has enough gain to amplify the atmospheric noise to an uncomfortable level.
The advantage of a tuned RF stage is improved rejection of the image frequency,
which is useful when the band is open, or when you have a local station at or
near the image frequency of the weak station you are listening to. The image
frequency is 910 kHz above the actual setting of the dial. For instance, if
you set your radio for 660 kHz, you may be able to hear a station transmitting
on 1570 kHz. The RF stages will amplify much more at 660 than at 1570
under such conditions, thus improving the performance.

You are confusing sensitivity with gain. In the context of a radio, sensitivity means how much signal the radio needs at the input for a given signal to noise ratio at the output. This is why a more sensitive radio is more capable of receiving distant broadcasts than a less sensitive one.

If gain were the only measure of sensitivity, it would be quite useless, as you stated above.

maxhifi 11-14-2011 10:18 PM

Quote:

Originally Posted by HiFiCanada (Post 3018502)
Wow, I am sure glad that I posted a picture.
Yes, all the tubes are all in the wrong places and I would have never thought that the diagram was wrong. So now I can't trust the the schematics. I changed all the tubes around , according to the label underneath the cabinet and slowly turned the power back up with the variac and all the tubes light up.
Now I have a lot of hum, and if I just touch or tap the rectifier tube 35Z5 it almost sounds like I am taping a microphone. If I just tap it, the hum is louder and then just press on the tube, the hum gets a bit softer again.
The whole radio is recapped except two of the molded caps and I have not check the wiring to the schematic to see if it is all that it should be. I recapped the radio exactly to each capacitor what was in the radio, one by one, so I did not make a mistake unless it was wrong before.
I am getting zero radio reception and I may just try some other tubes from my stash.

Double check that all the tubes are in the right places. The 35Z5 can cause hum related problems sometimes, try replacing it.

I think checking the radio against the schematic will probably find the problem faster than typing on here. Measure all the voltages too, and compare vs riders. Double check elecrolytic capacitors for polarity.

When you check the wiring, don't take for granted anything in that radio is correct - the speaker is already at least 15 years newer than the radio itself, so who knows what else was changed.

If it's not a tube, or something simple, Use signal tracing to fix the radio. Go through the radio stage by stage, and touch the grid of each tube with a screwdriver. Work backwards, starting with the 50L6. You should hear a noise in the speaker each time you touch the grid. When you hear nothing, you have isolated the stage where the signal is dissapearing.

maxhifi 11-14-2011 10:32 PM

Quote:

Originally Posted by HiFiCanada (Post 3018502)
Wow, I am sure glad that I posted a picture.
Yes, all the tubes are all in the wrong places and I would have never thought that the diagram was wrong. So now I can't trust the the schematics. I changed all the tubes around , according to the label underneath the cabinet and slowly turned the power back up with the variac and all the tubes light up.
Now I have a lot of hum, and if I just touch or tap the rectifier tube 35Z5 it almost sounds like I am taping a microphone. If I just tap it, the hum is louder and then just press on the tube, the hum gets a bit softer again.
The whole radio is recapped except two of the molded caps and I have not check the wiring to the schematic to see if it is all that it should be. I recapped the radio exactly to each capacitor what was in the radio, one by one, so I did not make a mistake unless it was wrong before.
I am getting zero radio reception and I may just try some other tubes from my stash.

It just occured to me - long shot, but if I'm right it'll save hassle - the diagram is not wrong, you are aware, that the diagram on the bottom left is a BOTTOM view of the chassis. It looks exactly like the chassis in your picture, so double check again the tube locations.

You could still have the tubes in wrong and have them lighting up.


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