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Philco 51-532 transitone squeaks, hums, and crackles (a little bit) - Printable Version

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Philco 51-532 transitone squeaks, hums, and crackles (a little bit) - ccomer1955 - 11-10-2016

I feel like I'm in a new world here. This will be the first time I've tried to fix an AA5. All my previous repairs have been transformer sets or 20s TRFs. I have recapped this one and changed out any resistors that needed it. I used my ohm meter to see if the filament string has continuity, and it does...that is if measuring from pin 2 on the 35Z5GT through pin 8 on the 14B6. When I apply power, the pilot light comes on and after warmup the speaker makes noise, but the noise is hum between strong stations, squeaks on signal (and the pilot light dims a bit), and some minor crackling as I tune across the dial.

I have made a mistake with the loop antenna I'm pretty sure. I disconnected it without labeling the leads (it has four-two to the antenna coil and two to the tuning capacitor. So I'm not sure if I have that connected correctly...I went by the drawing of the antenna on the schematic as well as I could. How crucial is the hookup on the loop?

Also, I used 33uf electrolytic caps at 250v for all three electrolytic caps because I had them here already...that should be OK, right?

I've read these sets get silver mica disease, but I would hear crackling all the time if that was the case, and I would have some stations behind the noise as well. Basically, it looks to me like the radio is responding to signal (judging by the different noises and the pilot light getting dimmer at certain spots on the dial), but isn't converting signal to output for some reason. Any ideas?

I will in the meantime start tracing the problem on the schematic. Is troubleshooting the same as with transformer sets? Start at the output and work backwards? If so, output is likely good since I hear noise and volume is acceptable. So check the detector next, then IF, then the converter.

RE: Philco 451-532 transitone squeaks, hums, and crackles (a little bit) - morzh - 11-10-2016

Can you provide the sch link?

RE: Philco 451-532 transitone squeaks, hums, and crackles (a little bit) - ccomer1955 - 11-10-2016

I'm sorry, I forgot. I went back and found a couple of resistors to replace that I had not caught the first time: R5 was measuring at around 200 ohms-should be 68 ohms, and R 4 was measuring way off in place, but when I removed it, it was on the money...I replaced it anyway.

I caught a bigger problem at C 5. I had put in a .0003 uf cap in stead of a .003 uf cap. I replaced it.

I powered it up again, and this time I get no squeals at all, but a buzzing that gets stronger where there seems to be stations on the dial...occasionally, it almost sounds like a signal getting through. Again, the pilot light burns brighter where the signal seems to be. I guess that is normal for an AA5?

http://www.nostalgiaair.org/pagesbymodel/721/M0013721.pdf

http://www.nostalgiaair.org/pagesbymodel/720/M0013720.pdf

RE: Philco 51-532 transitone squeaks, hums, and crackles (a little bit) - ccomer1955 - 11-10-2016

Update: definitely an antenna issue. I put a long wire antenna on it after I heard a weak signal on the dial, and had a few seconds of clear strong signal coming through...nice and loud, but the connection seems intermittent because it hasn't repeated for me. I can get a station to play weakly, but that seems to be it right now. The loop is made of about twenty or so turns of thin enameled wire and has two runs glued together yielding four leads. Two the leads are supposed to connect to the antenna post and the ground post, and the other two are supposed to connect to each of the two gangs on the tuning cap.

RE: Philco 51-532 transitone squeaks, hums, and crackles (a little bit) - Radioroslyn - 11-10-2016

Hey Charlie,
I knew you could do it!! I started to post a reply a couple of hours ago but got a phone call and distracted. Ant loop must be connected properly for the set to work.

Using the 33mf caps are  fine.