# Capacitor help please (vintage phone)

**URL:** <https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822>\
**Category:** General Electronics\
**Created:** [February 16, 2023, 4:08am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822 "2023-02-16T04:08:36Z")\
**Posts on this page:** 20\
**Page:** 1

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**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 4:08am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/1 "2023-02-16T04:08:36Z")

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I am working with an old rotary phone and want to make the ringer work. The "network" box the phone has uses a 0.47µF capacitor, (seen here [https://cdn.shopify.com/s/files/1/0654/8704/4831/products/DSC\_0132-01.jpg?v=1657660375&width=1445](https://cdn.shopify.com/s/files/1/0654/8704/4831/products/DSC_0132-01.jpg?v=1657660375&width=1445)). This is Greek to me, (I'm learning), This "network" box is big and all I need from it is the capacitor. What capacitor do I need?

Again, I am new to this, so please forgive my ignorance.

Thanks.

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**Author:** ![JohnRob](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/johnrob/32/253560_2.png) [@JohnRob](https://forum.arduino.cc/u/JohnRob)\
**Post date:** [February 16, 2023, 4:55am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/2 "2023-02-16T04:55:13Z")

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I highly doubt the device in the photo is a capacitor. My best guess is it's a specialty transformer of some sort.

Not sure where you got the 0.47µf value.

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**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 5:10am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/3 "2023-02-16T05:10:24Z")

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The device is a phone network controller. It has in internal capacitor that according to [classicrotaryphones.com](http://www.classicrotaryphones.com/forum/index.php?topic=13436.0) is a 0.47µF capacitor.

> The ringer must have a capacitor (condenser) in series before connecting to the line. The network provides this 0.47µF capacitor on terminals A and K. Polarity is not important.

I am just unsure of a smaller equivalent version/option.

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**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\
**Post date:** [February 16, 2023, 5:11am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/4 "2023-02-16T05:11:27Z")

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ORIGINAL IMAAGE:

 ![DSC_0132-01](https://europe1.discourse-cdn.com/arduino/original/4X/a/9/9/a99a52e6e8f4049c82ceb629b2bb4e2cc259bbc2.webp)

> **[Telephone interfacing circuits](https://www.epanorama.net/circuits/teleinterface.html)**
>
> Telephone line interfacing described.

(\<3 the schematics)

[units - key telephone, 425B, 1, 1972-01-31.pdf](https://forum.arduino.cc/uploads/short-url/3AjmT1deXTxV41baaDOCWNqpv1t.pdf) (284.7 KB)

 ![Screenshot 2023-02-16 at 00-13-21 units - key telephone 425B 1 1972-01-31.jpg - units - key telephone 425B 1 1972-01-31.pdf](https://europe1.discourse-cdn.com/arduino/original/4X/7/1/4/714e3907902d9ec735b36f1350ee8f268065e257.png)

This is the link to that cap:  
[http://bellsystempractices.org/500-/501-/501-135-100-i01\_1974-03-01.pdf](http://bellsystempractices.org/500-/501-/501-135-100-i01_1974-03-01.pdf)

 ![Screenshot 2023-02-16 at 00-17-30 501-135-100-i01_1974-03-01.pdf](https://europe1.discourse-cdn.com/arduino/original/4X/e/c/0/ec0b2e22f71aa4a8c4cbb408e69319b58a1234e6.jpeg)

 ![WE500-07b](https://europe1.discourse-cdn.com/arduino/original/4X/d/9/8/d9879f008ca750fe33259b50d63ca17eb21d0050.jpeg)

Different model, but same symbols (RR, F, R, K, et c.)

 ![4228D_network](https://europe1.discourse-cdn.com/arduino/original/4X/f/0/b/f0b4d63427cc3b7e9df48d46b9bfe8e57656f86a.webp)

 ![wd_we500a-b-j-k_big](https://europe1.discourse-cdn.com/arduino/original/4X/6/5/d/65dc1e3aaa213e89577c0a778074b48d66fadc88.webp)

 ![fluxcap](https://europe1.discourse-cdn.com/arduino/original/4X/c/3/b/c3b96b8cde0ce7f8e16cf4f579082d4e1e78bc34.jpeg)

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<div class="post-metadata">

**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 5:33am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/5 "2023-02-16T05:33:32Z")

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Thank you. 🙂 I have the OE parts but only need the capacitor from the box and it takes up a lot of space, so I'm looking for a smaller option?

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<div class="post-metadata">

**Author:** ![build\_1971](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/build_1971/32/689930_2.png) [@build\_1971](https://forum.arduino.cc/u/build_1971)\
**Post date:** [February 16, 2023, 5:34am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/6 "2023-02-16T05:34:57Z")

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An integrated circuit with screw terminals from the fifties or so....! 😃  
Anyway definitely more than only one capacitor...

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<div class="post-metadata">

**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 5:36am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/7 "2023-02-16T05:36:29Z")

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I have a schematic for it, but not able to post images here.

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<div class="post-metadata">

**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\
**Post date:** [February 16, 2023, 5:36am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/8 "2023-02-16T05:36:41Z")

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> [@build\_1971](#):
>
> fifties

1. 

Schematics in post #4

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<div class="post-metadata">

**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 5:40am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/9 "2023-02-16T05:40:59Z")

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Your diagram and schematics are different from the ones I found.

 ![425J_network](https://europe1.discourse-cdn.com/arduino/original/4X/c/e/1/ce111726f79b09644a7b531e61680883b9b429ce.gif)

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<div class="post-metadata">

**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\
**Post date:** [February 16, 2023, 5:43am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/10 "2023-02-16T05:43:38Z")

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@headmouse11279 You have the correct model (425). (my links were not exact models - except for this PDF link (paage in post #4) [http://bellsystempractices.org/500-/501-/501-135-100-i01\_1974-03-01.pdf](http://bellsystempractices.org/500-/501-/501-135-100-i01_1974-03-01.pdf)

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**Author:** ![EmilyJane](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/emilyjane/32/821537_2.png) [@EmilyJane](https://forum.arduino.cc/u/EmilyJane)\
**Post date:** [February 16, 2023, 5:46am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/11 "2023-02-16T05:46:05Z")

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This would work and costs less than a dollar. of course shipping would make it more but just find one with the same specs.

 ![cap 47](https://europe1.discourse-cdn.com/arduino/original/4X/7/d/b/7db31c0c10c079b40ca9b532d8f646bc24f93938.png)

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<div class="post-metadata">

**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 5:47am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/12 "2023-02-16T05:47:16Z")

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AH, ok. So. the capacitor between A and K is said to be a 0.47µF capacitor. When I do searches for that, I get things like this.

 ![Untitled](https://europe1.discourse-cdn.com/arduino/original/4X/3/5/4/354d22277bb52d2ad457329135765f07b26c3493.jpeg)

So, i should be able to use something much smaller to do the same job?

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<div class="post-metadata">

**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 5:48am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/13 "2023-02-16T05:48:48Z")

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Ok, thanks. That's what I was hoping. I just didn't know and wanted to make sure.

Thanks for the help. 🙂

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<div class="post-metadata">

**Author:** ![EmilyJane](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/emilyjane/32/821537_2.png) [@EmilyJane](https://forum.arduino.cc/u/EmilyJane)\
**Post date:** [February 16, 2023, 5:51am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/14 "2023-02-16T05:51:36Z")

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Sure. The important specs are that it be non-polarized and a high enough voltage rating. Ring voltage is typically 90 Vac and less than 150Vac max.

 ![Screen Shot 2023-02-16 at 12.13.50 AM](https://europe1.discourse-cdn.com/arduino/original/4X/6/9/7/697382aa34e768e7e924825bb4eeca9894bb0070.jpeg)

I found this on Amazon. You probably don't need 5 of them but anywhere you get one you are going to have to pay shipping so the cost will be the same.

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<div class="post-metadata">

**Author:** ![build\_1971](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/build_1971/32/689930_2.png) [@build\_1971](https://forum.arduino.cc/u/build_1971)\
**Post date:** [February 16, 2023, 6:12am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/15 "2023-02-16T06:12:38Z")

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Oh than it is still fresh and new!

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<div class="post-metadata">

**Author:** ![build\_1971](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/build_1971/32/689930_2.png) [@build\_1971](https://forum.arduino.cc/u/build_1971)\
**Post date:** [February 16, 2023, 6:15am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/16 "2023-02-16T06:15:51Z")

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Interestingly, the symbolic in the drawing indicates a electrolytic capacitor....  
Usually will not harm if you replace an electrolytic capacitor with a non-polarized one.  
But the bipolar one will be bigger and may not fit in the block thing

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<div class="post-metadata">

**Author:** ![EmilyJane](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/emilyjane/32/821537_2.png) [@EmilyJane](https://forum.arduino.cc/u/EmilyJane)\
**Post date:** [February 16, 2023, 6:20am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/17 "2023-02-16T06:20:13Z")

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I wouldn't use an electrolytic in that application. The ones I found aren't very big.

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<div class="post-metadata">

**Author:** ![PerryBebbington](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/perrybebbington/32/238766_2.png) [@PerryBebbington](https://forum.arduino.cc/u/PerryBebbington)\
**Post date:** [February 16, 2023, 11:05am UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/18 "2023-02-16T11:05:15Z")

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If you just want to make the ringer ring without a connection to a phone line then you need about 75VAC around 25Hz, exact voltage and frequency not important. The capacitor is to isolate the 50VDC on the line from the bell. No line no need for a capacitor.

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<div class="post-metadata">

**Author:** ![headmouse11279](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/headmouse11279/32/920654_2.png) [@headmouse11279](https://forum.arduino.cc/u/headmouse11279)\
**Post date:** [February 16, 2023, 8:40pm UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/19 "2023-02-16T20:40:30Z")

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Just so I understand, I can replace the OE unit with a 75 VAC capacitor and the +/- wires to the Arduino and it will ring?

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<div class="post-metadata">

**Author:** ![PerryBebbington](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/perrybebbington/32/238766_2.png) [@PerryBebbington](https://forum.arduino.cc/u/PerryBebbington)\
**Post date:** [February 16, 2023, 8:49pm UTC](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822/20 "2023-02-16T20:49:47Z")

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What is an OE unit?

But no, your description does not make sense, I'm not even going to try to understand what it means.

If you just want to ring the bell without it being connected to a phone line or the other functionality of the phone then you need to generate about 75VAC at 25Hz and connect that to the bell. I can't imagine where you think your capacitor and wires from the Arduino go.

[Next page](https://forum.arduino.cc/t/capacitor-help-please-vintage-phone/1090822.md?page=2)