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2500 Series Desk Phone

Started by oesjmr, June 10, 2017, 10:43:38 AM

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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

#1
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
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SteveInWA

Like this:

dircom

Bad dial, got many service calls for that problem, back in the Ma Bell days, and Steve is correct, they finally made a better dial (but that might have been after Ma Bell's divorce).

Lavarock7

You should be able to find a replacement pad.

In my earlier days, if I wanted to fix this one, I would gut it and  add a touch tone encoder chip or a bunch of Signetics 555 timer chips. http://www.boondog.com/tutorials/dtmf/dtmf.htm

(Before mobile phones were cheap, we used to make telephone calls with our Ham radios and touch tone pads listed from old phones).

I took a quick look and could not finds my individual replacement pad.

I once took an old rotary dial phone and converted it to a lamp. The lamp post came out behind the receiver. You lifted the receiver (the AC went through the switch contacts). Then there was a dimmer connected to the dial :-)

Strangely, I also found an AOL install kit inside a wooden box. I think it was handed out under a special promotion on American Airlines.
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SteveInWA

I think we've flogged this issue to death.

Here's a YouTube video showing the difference between the old and new 2500 keypads.  The video is insufferably long and boring, and it doesn't show how to repair the old keypad, so don't bother watching it to the end.  The author correctly points out that the "fix" is to replace it, not try to repair it.  Perhaps, if you contact them, they can either sell you an electronic keypad, or suggest a source.

https://www.youtube.com/watch?v=RWbONnfYyzU

oesjmr

Thanks for the replies everyone! Sorry for the late reply...it's amazing how much work piles up when you take a week's vacation!

I found a replacement keypad here, http://www.oldphoneworks.com/2500-2554-touch-pad-brand-new.html. They also sell a polarity guard, so I'll probably buy both to see if I can get things working.

Thanks again everyone! I'll post back if I'm able to get this old phone working again.

SteveInWA

Quote from: oesjmr on June 29, 2017, 08:11:33 PM
Thanks for the replies everyone! Sorry for the late reply...it's amazing how much work piles up when you take a week's vacation!

I found a replacement keypad here, http://www.oldphoneworks.com/2500-2554-touch-pad-brand-new.html. They also sell a polarity guard, so I'll probably buy both to see if I can get things working.

Thanks again everyone! I'll post back if I'm able to get this old phone working again.

Perfect.  I've bought from them before, and they have great service.  I suggest taking a photo of the wring before you disconnect things, just in case you lose track of what goes where.  If the new keypad has different wiring terminals than the old one, the guy at Old Phone Works can probably help you figure it out.

mihow

I have a 2500 phone as well (Bell System by Western Electric 2500D 2-69). I have a dial tone, the phone rings and I can receive calls but I can not dial out. When I press the key pad I hear button tones but the dial tone never stops. I tried reversing the polarity (swapped the red and green wires) without luck. There is also a yellow wire I'm not sure what to do with. Any ideas? Photos attached!

SteveInWA

Your keypad is shot.  Either throw away the phone, or try to get a replacement from somebody on eBay who will accept returns.

dircom

I think Steve meant to say, either take your old phone to a recycling place (hopefully you have one), or replace the keypad, and recycle the old one.
Too much e-Waste!