2500 Series Desk Phone
oesjmr:
I recently acquired a circa 1972 2500D series desk phone that I would love to make work with my Obi200. I get a dial tone when I hook up the phone. However, the dial tones for 1, 4, 7 don't seem to work correctly (they're very faint but don't break the dial tone). 3, 6, 9 sound fine. 2, 5, 8, 0 are somewhere in between.
I did some Googling and looked into the polarity issue, switching L1 and L2, but I received absolutely no dial tone then. Further, the phone isn't ringing when I call. I found a post elsewhere in this forum suggesting changing the ring voltage to 82VAC in expert settings, but the phone still didn't ring. I also tried to switch the pin position for the ringer inside the phone to no avail.
So far I haven't been able to make this phone work at all. I know I can use a more modern phone or get a cheap replica of the 2500 series phone on Amazon, but I really want to put this vintage phone to use! Has anyone had any luck getting their older 2500 series phone to work with the Obi200? I've included a photo of the phone and the wiring board inside.
drgeoff:
The phone isn't working with your OBi because the phone is faulty. No amount of tinkering with the OBi's configuration is going to change that.
You are much more likely to get helpful info to fix the phone on a site where the main interest is old phones.
http://www.beatriceco.com/bti/porticus/bell/telephones.html may and http://www.telephonecollectors.info/index.php/document-repository/cat_view/3-bsp-bell-system-practice-library/69-bsp-categories-by-later-division-number-e-g-512/97-500-529-station-equipment/24-502-division-station-sets-common-battery be useful.
SteveInWA:
Gawd, 1970s "avocado" color; hideous! Do you have an avocado colored refrigerator, too? ;D At least, the Bell System was trying to keep up with the fashion of that era.
The keypad on the phone is probably shot. The original TouchTone keypads used mechanical leaf spring switches, and the switch contacts would eventually become corroded and fail to make reliable contact. The circuitry was all analog; each key had to close the two corresponding switches to generate the two tones (as opposed to modern keypads, that simply send a digital signal to an IC). Poor contact would result in distorted or absent tones.
You could try to remove the keypad, and clean it with contact cleaner. There was a special relay contact cleaning tool back in the day that you might still find for sale -- it was a thin strip of spring steel coated with very fine abrasive (probably diamond dust). Don't try any other type of tool (emery board, sandpaper, file), as those will likely ruin the contacts.
You can probably buy a replacement keypad on eBay, but unless the seller will accept returns, it's possible that the replacement will be just as bad. There were some later-generation keypads that worked digitally; if you can find one of those, it'll work great.
Lavarock7:
Pressing two vertical keys like 1&4 or 2&5 or 3&6 should produce a single tone for each column as should 1^2 etc will produce a single tone for each row. All tones should be essentially the same volume as I remember.
https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling
SteveInWA:
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