Hi All, hope you all had a wonderful Thanksgiving!!! Just recently picked up a Grunow 560 radio. It didn't have any tubes in it and has been recently recapped. I put in good tubes but got just static. I replaced 2 250K resistors now I get our strongest station all across the dial and it sounds the best when it is on 720 were it belongs it gets weaker when you go off of the station but it still plays through out the dial. I'm thinking maybe another bad resistor on the 6A7 tube, what are your thoughts? Thanks, George T.

George,
Have you checked the voltages around the 6A7?

http://www.nostalgiaair.org/PagesByModel/363/M0008363.pdf
Carl T

:Hi All, hope you all had a wonderful Thanksgiving!!! Just recently picked up a Grunow 560 radio. It didn't have any tubes in it and has been recently recapped. I put in good tubes but got just static. I replaced 2 250K resistors now I get our strongest station all across the dial and it sounds the best when it is on 720 were it belongs it gets weaker when you go off of the station but it still plays through out the dial. I'm thinking maybe another bad resistor on the 6A7 tube, what are your thoughts? Thanks, George T.
:

:George,
:Have you checked the voltages around the 6A7?
:
:http://www.nostalgiaair.org/PagesByModel/363/M0008363.pdf
:Carl T

No not yet the resistors are way off tolerance so going to give them a shot. Then start checking voltages. Thanks, George T.
:
::Hi All, hope you all had a wonderful Thanksgiving!!! Just recently picked up a Grunow 560 radio. It didn't have any tubes in it and has been recently recapped. I put in good tubes but got just static. I replaced 2 250K resistors now I get our strongest station all across the dial and it sounds the best when it is on 720 were it belongs it gets weaker when you go off of the station but it still plays through out the dial. I'm thinking maybe another bad resistor on the 6A7 tube, what are your thoughts? Thanks, George T.
::
:
:

Hello George. How is the Packard radio doing? I hope you did read "Note About Packard" This might save the owner a lot of grief.

:Hello George. How is the Packard radio doing? I hope you did read "Note About Packard" This might save the owner a lot of grief.

Hi Warren, I copied the info that you sent and sent it to the owner and haven't heard back from him yet. It sure did provide a lot of food for thought. Will keep you abreast of the situation. Thanks So Much, George.

Forgot to mention the Heater Defroster motor. This is 6 volt positive ground. This too will run backwards, and blow the warm air out. Not for long though. 12 volts is sure to burn that out too.

As others have suggested, check the voltages around the 6A7. The voltage at the oscillator grid should be negative in the neighborhood of 5 volts on broadcast frequencies. The symptom you describe is common with super heterodynes whose oscillator is not functioning.

T.
:

:As others have suggested, check the voltages around the 6A7. The voltage at the oscillator grid should be negative in the neighborhood of 5 volts on broadcast frequencies. The symptom you describe is common with super heterodynes whose oscillator is not functioning.
:
:T.
::
:
Hi, checked the voltages on the 6A7 tube. Pin 1 = 6.8 ac, 2 = 276.9 DC, 3 = 111 DC, 4 = 275 AC, 5 none, 6 4.7 DC and .002 AC. The tuning condenser screws make no change but the IF trans seems to be working fine. Thanks Again, George T.
:

http://www.nostalgiaair.org/PagesByModel/363/M0008363.pdf

Pin 5 is your biggest concern. Should be around -5VDC. Check all resistors associated with this circuit. It appears that you have B+ at pin 4, indicating that the oscillator secondary and the resistor that feeds it B+ are fine. However, the voltage should be DC.

Check the oscillator primary and the 50K resistor that biases the oscillator grid. Check capacitors for shorts (including tuning capacitor).

T.

:http://www.nostalgiaair.org/PagesByModel/363/M0008363.pdf
:
:Pin 5 is your biggest concern. Should be around -5VDC. Check all resistors associated with this circuit. It appears that you have B+ at pin 4, indicating that the oscillator secondary and the resistor that feeds it B+ are fine. However, the voltage should be DC.
:
Hi, checked the transformer by the 6A7 and 6D6 under the chassis, repaired one broken wire. Now I get 1280 and 720 really good. I get other stations also but 720 can be heard up to around 900 on the dial. I replaced the 50K on the 6A7 tube. This is going to sound stupid but by oscillator secondary what do you mean? If you could give me the number for it from the schematic it would really help. I should have known when I got the radio and there was no tubes in it and it had been recapped it was going to be a problem. LOL I have no responce from the tunning condenser adjustment but it does change stations now. Thank You, George T.
:Check the oscillator primary and the 50K resistor that biases the oscillator grid. Check capacitors for shorts (including tuning capacitor).
:
:T.
:

::http://www.nostalgiaair.org/PagesByModel/363/M0008363.pdf

http://www.nostalgiaair.org/tubes/6a7.htm

The oscillator coil is located down and to the left of the oscillator tube (6A7). It has two primaries: one for broadcast and one for short wave. These connect through the band switch to pin 5 of the oscillator section of the 6A7, and to the chassis return through small value capacitors. The oscillator coil secondary connects to pin 4, grid 2 of the 6A7, which serves as the oscillator plate. The other side of the secondary winding connects to B+ through a 20K resistor.

You should be measuring the resistances of the primary coils and comparing them to those shown in the schematic. Be sure to not include the primary coil capacitors in your primary coil measurements. Also check the band switch for continuity when each coil is selected.

If all is well, check again for a negative voltage at pin 5. If it is there, then your receiver most likely just needs an alignment at this point.

T.

:::http://www.nostalgiaair.org/PagesByModel/363/M0008363.pdf
:
:http://www.nostalgiaair.org/tubes/6a7.htm
:
:The oscillator coil is located down and to the left of the oscillator tube (6A7). It has two primaries: one for broadcast and one for short wave. These connect through the band switch to pin 5 of the oscillator section of the 6A7, and to the chassis return through small value capacitors. The oscillator coil secondary connects to pin 4, grid 2 of the 6A7, which serves as the oscillator plate. The other side of the secondary winding connects to B+ through a 20K resistor.
:
:You should be measuring the resistances of the primary coils and comparing them to those shown in the schematic. Be sure to not include the primary coil capacitors in your primary coil measurements. Also check the band switch for continuity when each coil is selected.
:
:If all is well, check again for a negative voltage at pin 5. If it is there, then your receiver most likely just needs an alignment at this point.
:
:T.
:

Hi Thomas, I pulled that oscilliator out yesterday and it has 6 lugs on it. Well it has had lots of work done on it and had 2 wires hanging loose. I connected the 2 wires were I though they went but it didn't make a difference, although I did get some resistance through the repair job I did. But I still have 4 more lugs that I'm not getting anything through. Looks like I might have to pull it out again and try a little harder. To bad you can't just buy one for it. I bet somebody put the wrong tube in the wrong place at one time. On that coil there are bare wires showing and then it looks like there are other wires under a yellow tape does that mean anything? Thanks For All Of Your Help, George T.

I'd have to see a picture to know what you are talking about. Sometimes coils are wound one on top of the other.

You may be able to repair or rewind the coils if they are open.

T.

:I'd have to see a picture to know what you are talking about. Sometimes coils are wound one on top of the other.
:
:You may be able to repair or rewind the coils if they are open.
:
:T.
:

Hi Thomas, I will remove it tomorrow night and list my email. I will take a picture and send it to you if you would like, Thanks Again, George T

Hi Thomas, yeah that oscillator coil was toast. That
stuff I was telling you about was scotch tape. I think I'm going to get some 34 guage enamaled wire and try to rebuild it, there was no saving it. I'm not sure how many wraps I need but I do know how much space they took up on the coil. I would imaging the largest wrap will hook up to the 6A7 tube. Thanks for All Of Your Help. George T.

The largest coil with the finest wire is your broadcast coil. The second largest coil connects to the plate circuit. The least largest coil (least turns), and most likely the thickest wire, is your short wave coil. This will most likely still be good.

Count the turns of each bad coil as you unwind it. The broadcast coil and short wave coil are most critical (though hopefully the short wave coil is fine). The plate coil is not so critical. Wind the new coils in the same direction with the same turn counts, hopefully in the same formation.

If the oscillator fails to function at first, you may have one of the windings backwards. If both bands won't work, it's probably the plate coil. If only one band doesn't work and you rewound the coil for that band, then most likely that coil is connected backwards. If you didn't rewind that band, and it doesn't work, but the other band does, most likely you need to reverse the plate coil and the other band coil.

T.

:The largest coil with the finest wire is your broadcast coil. The second largest coil connects to the plate circuit. The least largest coil (least turns), and most likely the thickest wire, is your short wave coil. This will most likely still be good.
:
:Count the turns of each bad coil as you unwind it. The broadcast coil and short wave coil are most critical (though hopefully the short wave coil is fine). The plate coil is not so critical. Wind the new coils in the same direction with the same turn counts, hopefully in the same formation.
:
:If the oscillator fails to function at first, you may have one of the windings backwards. If both bands won't work, it's probably the plate coil. If only one band doesn't work and you rewound the coil for that band, then most likely that coil is connected backwards. If you didn't rewind that band, and it doesn't work, but the other band does, most likely you need to reverse the plate coil and the other band coil.
:
:T.
:

Hi Thomas, all 3 coils were broken in several places the wire got hot and brittle. Pretty much the only thing I can go by is the size the wires took up on the tube. I don't care to much about the SW but do know it had 20 turns and was the smallest. All 3 coils appear to have 34 guage wire. It's looks like it is going to be a Turkey Shoot. Wish Me Luck, they won't have the wire in until next week. Thanks a Million, George T.

Good luck! Hope you are able to rewind it easily. Even if the coils are broken, you can still count turns. Just keep removing the wire until it's all gone, and note how many turns it made and in what direction it was wound.

T.