Strange acting Crosley AA5 - Printable Version
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Strange acting Crosley AA5 - NostalgiaRadioTime - 11-10-2018
Working on the little AA5 AM / Shortwave Crosley model 56TXL I picked up last weekend and, after a complete recap, am encountering something odd. The set receives stations, but only for a second or two and they fade away. They're where they should be on the dial but as quickly as I find them they're gone. Even my overpowering sstran amt3000 disappears. I've swapped all the tubes with the exception of the mixer, 14Q7 which I don't have a spare. While I'm waiting for one to arrive, does anyone have any ideas on what could be causing this or have experienced it before? I still have a few resistors to check but this acts more like an OSC or ANT problem? It has the factory loop antenna attached to the back cover.
Here's the schematic:
http://www.nostalgiaair.org/pagesbymodel/471/M0003471.pdf
RE: Strange acting Crosley AA5 - Radioroslyn - 11-10-2018
Oh no U again!!!!!![Image: http://philcoradio.com/phorum/images/smilies/icon_lol.gif]
As normal I'm confused. When you tune in a station and it plays for several seconds does the set not recive any more? Set is dead?? If you tune it to another station does it just play for a few seconds too??
RE: Strange acting Crosley AA5 - NostalgiaRadioTime - 11-10-2018
>> As normal I'm confused.
That makes two of us!
>>When you tune in a station and it plays for several seconds does the set not receive any more?
I can tune the dial slightly and the same station will come in again, for only a second or two.
>>Set is dead??
No, not dead just doesn't hold stations.
>>If you tune it to another station does it just play for a few seconds too??
Yes, then they fade away quickly too.
RE: Strange acting Crosley AA5 - Radioroslyn - 11-10-2018
Ok have a look at the avc voltage. Connect the - voltmeter lead to the - side of one of the filter caps ( that's B-) and the + lead to the junction of #29 and 30. With a weak signal should see a small - voltage like .5-1v. With a strong signal could see -5 or 6v.
ps the set won't work as drawn in the schematic, plate of the 1st audio is grounded needs hv there. Dumb schematic!!!
RE: Strange acting Crosley AA5 - David - 11-10-2018
Hope this helps!!!!!
RE: Strange acting Crosley AA5 - NostalgiaRadioTime - 11-10-2018
Thanks, David!
Spent a while looking for the 47K resistor #30...then I realized it's in the IF can. I found the 3.3 meg #29 and it's attached directly to the volume control.
Doing your test, with no station I get -.6 VDC at that point.
When I get the strong local station to come in for a second or two, I get -1.8 VDC.
Am still wondering if, even though it tests OK, if that 14Q7 tube is causing this lack of station hold. I won't be able to verify that until I get the tube next week sometime.
RE: Strange acting Crosley AA5 - Radioroslyn - 11-11-2018
Ok so w/a strong station does the avc voltage drop as if there's no station when it's misbehaving?
RE: Strange acting Crosley AA5 - NostalgiaRadioTime - 11-11-2018
Yes as the station fades the voltage goes back to what it was with no station coming in.
RE: Strange acting Crosley AA5 - Radioroslyn - 11-11-2018
Ok seems your issue in in the rf or if section. Try feeding a 455kc signal into the ant and hear if it misbehaves.
RE: Strange acting Crosley AA5 - NostalgiaRadioTime - 11-11-2018
Seems to be a loctal tube socket problem. Pins are too loose in the 14B6 and 14A7 sockets. If I use my poker stick and hold tension on the socket against the pin it plays fine. But how do you tighten those little pin sockets around the tube pins?
RE: Strange acting Crosley AA5 - David - 11-11-2018
Would it be possible to put a little solder inn the pin sockets to take up some of the space??? Yes I have been one with some Irish whiskey tonight.