The AM Forum

Unhappy about SBC lack of phone service I decided to look at the problem after the the phone was dead for over 24 hours.
I took out the lightning suppressors and the phone came up. There appears to be carbon contacts on them. I cleaned them off and shoved them back in and phone still works. Does anyone know if I could have just had a carbon track shorting the line? I had no dial tone just 60 hz buzz.  gfz

Must have been the negative line getting enough leakage to ground from some carbon path to appear to be an off-hook phone.  That would cause hum, too, because it would introduce a heavy unbalance and introduce ground potential differences onto the line.  You could probably duplicate the symptoms with something like a 1.5K resistor to ground from the negative side of the line.

I had a slightly similar problem, except I still had service. Line would get very noisey with hum, static, etc. on any given day. Decided to check into it and found that the wiring was at fault, where it passes through the little porcelain feed thru tube from outside to inside the house. Tension on wire, impacts, whatever else over the years caused the wires to become somehow crappified inside the insulation. I found it odd because it didn't ever lose connection, but got noisey as hell to the point of having to hang up.

JSed a substitute piece of wire for testing and abracadabra - noise gone. Someday I need to go back and make the fix permanent.

Frank, if you have those old carbon suppressors at your Dmarc you must be in an old house with ancient wiring. that stuff has been gone for years. they get shorted by lightening hits, grow very leaky with age and humidity, and often go semiconductor and wreak RFI havoc in your house phone. ditch the old protector for a new one with MOV's and you will be a happy camper. by the way- if you have dialup those old carbons can raise hell with your throughput.

Yea, AHs finally showed up after I fixed it and claimed it was inside. They did not change the carbon rods. I'll have to fight the bill.  fc

see if you can get them back to change that protector. in these parts the techs are supposed to replace them on sight- good or bad. they don't meet current specs, and in some areas don't meet the local electrical code anymore either.