Philco 46-1203 Phono hum. too much? - Printable Version
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Philco 46-1203 Phono hum. too much? - BUbba - 07-08-2011
Radio side sounds awsome. Little to ZERO hum. Had the Shure Crystal P90S Phono cartridge rebuilt by westech services and put it in. Phono is there but hums too much with respect to audio.. what are the suspect things to get rid of it or are they all this bad? I did all the filter caps a few years back maybee 6 years ago..
Bubba
Re: Philco 46-1203 Phono hum. too much? - BUbba - 07-08-2011
Never mind got the offending ground wire..
Re: Philco 46-1203 Phono hum. too much? - Radioroslyn - 07-08-2011
Sounds like you got a bad ground connection. Try this reverse the wire on the cartridge. See if there is a difference. Same with the ac cord. Try shorting the wires going to the cartridge. If that mitigates the hum you my have a bad cartridge but check the see how the tone arm is grounded to the chassis and make sure all of that is connected. Check C-26 and 27.
Good luck
Terry
Re: Philco 46-1203 Phono hum. too much? - BUbba - 07-09-2011
Mine is the 46-1201-122 version. Does anyone know how or have the schematic of how the photo should be wired?
I think I wired it wrong using the 46-1201 Schematic that was not the 122 version.
THX
Re: Philco 46-1203 Phono hum. too much? - BUbba - 07-09-2011
Fixed it,,, had wired the leads from the chassis backwards.
Any tips on reducing Phono volume? the thing blares now even on lowest volume I would like a bit more headroom. I can always turn it up.
How would I do this? Resister in series with hot lead of phono? Values?
THX
Re: Philco 46-1203 Phono hum. too much? - Marsupial - 07-09-2011
maybe try a potentiometer at first?
Re: Philco 46-1203 Phono hum. too much? - BUbba - 07-09-2011
If I were to put a resistor in series with the hot of the phono. What value would you use.
Pot is a 500K
20K? Would that work or effect the sound badly?
Bubbs
Re: Philco 46-1203 Phono hum. too much? - codefox1 - 07-09-2011
If the set expected a low output cartridge and you (or the last owner,) have replaced it with a high output cartrtidge, yes you will need a voltage divider of some sort, and a potentiometer would be a good start, but then the curve compensation may be way off. Not too great an issue if you just have a few scratchy 78's to play but if you get it right, these old sets can rock. Very very old jukeboxes sounded great.
Re: Philco 46-1203 Phono hum. too much? - Radioroslyn - 07-10-2011
If it is a crystal cartridge the output impedance is going to be very high. So if you are going to use a pot to adjust the output level of the cartridge then make it a high one like a meg or better. Hook the leads from the cartridge across the ends of the pot. This way the cartridge will always see the meg or so across it. If not it may tend to mess with the frequency response.
Terry
ps Hook the amplifier input across the ground side of the cartridge and the pot wiper.