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Curious problem with my Franken500

Started by McHeath, July 01, 2010, 06:48:32 PM

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McHeath

So I'm happily using my newly cooked up yellow and black frankenphone 500.  It's a mixture of dates and parts, with a 425B network dated 1960.  Everything is going swimmingly until:

Pop.

Heard that sound when I was talking to my son on it today, then the microphone went dead.  Everything else still works, but no microphone.  All the wiring is as D/P has it on his schematic here on the site, and it was working just fine.  But it did make a pop sound and then stopped transmitting sound.

No storms, a clear sunny day.

Any ideas?  I checked and retightened all connections, nothing.

Kenny C

take it out and bang it on your leg then try it
In memory of
  Marie B.
1926-2010

gpo706

Yes, if its a carbon granule mic a bit "percussive maintenance" might shake it up.
"now this should take five minutes, where's me screwdriver went now..?"

JorgeAmely

My initial reply to you was going to be "try your other ear", but you are a nice guy and deserve more than that.

Have you checked the hook switches, tried another microphone, or checked the dial contacts? In a 500, it doesn't go on hook when the mike circuit stops working. Using a DVM, check from screw head to screw head, to make sure the crimps are included in the circuit. I have seen those go bad after moving them around too much.

The microphone should have a relatively low reading of 75 to 250 ohms (from Dr. Meyer's book), but the one I just checked is about 3,000 ohms and works fine. It depends on how much current your meter produces at a particular range. Try tapping it lightly to see if that helps. The idea is that it should not be shorted or completely open.
Jorge

McHeath

Good replies folks.  Jorge, your idea of using the VDM to check continuity was dead on, I found that it was the crimps on the red wire.  Guess that happened from being old and being moved and tossed about a bit over the last couple of years in my closet.  Squeezed them down with pliers and we are good as new. 


Dan/Panther

Seems like recently I read here some place, that when things go south, try line or handset cords first. Seems to be true. I find the crimp is my most common reason for something not working. So far the only part in a 500 to malfunction on me is a ringer, and that was a Kellogg clone not WE. I still do not know why that phone makes all of my lines go dead ????
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

JorgeAmely

Jorge

Dan/Panther

Jorge;
That would be located in the Network ?
It's a 500 clone so basically just like a WE 500.
How do you test a network for bad components ?
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Phonesrfun

The ringer cap is located between network posts A and K.  It is a .5 mF capacitor, and the slate and slate/red ringer wires connect to A and K.

If you have a spare .5 mF cap laying around, try removing slate and slate/red from the network posts and hooking them to the spare cap instead, using some alligator clip-leads.  See if that gets things ringing again and eliminates the short.
-Bill G

Dan/Panther

Bill;
Got it, I will try that A.S.A.P.
Thanks;
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

JorgeAmely

D/P:

The cap in that network should show infinite resistance.
Jorge