1500D 10-button key pad problem - loose oscillator coil cover fix

[Tim Mc]

I received my 1500D yesterday and hooked it up to the house line to test.  The DTMF tones sounded off and would not break dial tone.  I removed the shell and the keypad's clear thin plastic dust cover, and burnished any contacts I could reach with a piece of paper index card.  I still had the weird tone problem, so I removed the bottom half of the dust cover.  One of the round ferrite pot covers (oscillator coil?) with its center coil was loose and dropped out.  I tinkered with it and found that I could change the tone by rotating the coil cover while holding it firmly in place.  I experimented until the tones sounded right and could break dial tone.  A dab of CA adhesive (super glue) and it's now in working order. 

Anyone that has a 1500 key pad experiencing weird tones may want to see if the coil covers are loose.  Hopefully this will save a key pad or two from the trash bin in the future.

[paul-f]

Well done, Tim!

The fix will work for any similar Western Electric touch tone dial, including 25-type, 35-type and 66-type, among others.

If the position doesn't end up perfect, the tuning slug in the coil may need to be moved a bit.  Since most of us don't have the tool designed for the purpose, a small dowel with one end whittled to fit the tuning slug will work.

[ESalter]

Paul-F said it.  The hardest part of that procedure is finding/making something triangular to use as a tuning tool.  I've only had a couple really bad dials that needed to be retuned, but both were able to be returned to working order.

---Eric

[Tim Mc]

Thanks!  The keys are looking a little worn.  Is it worth the risk to disassemble the key pad to clean up or replace the keys? 

[paul-f]

Are the keys worn or simply oxidized?  I've had good luck cleaning them with a cotton cloth and rubbing compound, then finishing with Novus or other polish.

The letters and numbers are double injection molded, so you can rub away and not worry about them.

[Tim Mc]

They look oxidized and already look better after a first round of Q-tips and rubbing compound last night.  I was worried about the lettering, so it's good news that they're double-injected.   I may hit them with 1000 and 2000 grit sandpaper and polish out with Novus.  I'll definitely try the electric toothbrush idea too.

Thanks again...love this forum!

[Dave F]

The triangular-tipped tool for adjusting the coils on a touchtone dial is KS19355-L3.  These were used in-house at phone refurbishing centers and were generally not distributed to field personnel, making them fairly rare to find today.

DF