HELP! Electronic sequencer for vintage door chime.

Seeking any manner of help in making an electronic sequencer for a multi-note doorbell. I restore old door chimes and one particular model from the 1940's-1950's has an electromechanical linear distributor that works as the chime sequencer. It has a limited life expectancy- long since expired- and it defies repair. You can see details of this device by looking up patent number 2245443. The task to be done though is just like that of any more common chime sequencer that uses a rotary distributor. The idea is to replace the electromechanical mess with modern electronics to time the power sequence to three or four 16v or 24v solenoids. Looking for any help… guidance, advice, moral support... but mostly hoping to find someone who can design and build a few of these, as I am largely clueless about electronic design.

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gentleLion6 months ago

I was going to make a simple electronic sequencer to replace an old Rittenhouse 520 chime's dashpot using simple relays and capacitors (cheap and crude but effective). However, while examining the dashpot to document all its electrical connections, I found you can reduce gravity's influence on it by rotating it most of the way sideways. Note you must keep the metal can grounded to the holder, it's part of the circuit's return (if you don't keep it in contact it will not chime).

You can perform this fix simply if your wires are long enough and you have room in the assembly. My Rittenhouse 520 did. After rotating the dashpot style sequencer slightly sideways and zip-tying it firmly in place, it's been operating flawlessly for the past 8 years. See attached pictures.

One last note to anyone performing professional repair and/or restoration work, make sure you're adding a fuse. Should be standard practice for conscientious minded vintage electronics repair people (many vintage radios, TV's, etc. didn't have them). The adjustable rheostat in the 520 would be the first thing to poof if the chime jammed on.

Rittenhouse 520 Doorbell.JPGRotated Dashpot.JPG

I just started on my parents 520 doorbell and rotating it does make it work. It was previously missing the last note. I am going to look into determining the proper fuse to use....maybe even a "self healing" fuse or a time delay fuse. I will report back.

So I hooked the doorbell up to a 16VAC supply (my old Lionel train transformer) through a 1 ohm resistor and monitored the voltage across that resistor on a scope. The doorbell takes about 2 amps for about 80mS for each of the 4 chimes. Based on that, you might think it should be simple to just add a slow-blow fuse in the 0.5 to 1 amp range. However, this will not work in real life. In real life, you have kids that will press and hold the doorbell button for several seconds at a time. When the doorbell button is pressed, it will also draw 2 amps until you let go and you don't want the fuse to blow. I am thinking a re-settable fuse may be the way to go; see: https://en.wikipedia.org/wiki/Resettable_fuse

I just need to find some re-settable fuses around the .5 to 1 amp range and see which one will allow the doorbell to work properly under normal conditions but will "trip" if something is kept powered on for more than about 10-20 seconds.

I got the best results using a LITTELFUSE SMD050F-2 Resettable fuse. These cost under $1, are smaller than a dime, and seem to easily allow 2 amps to flow for a short amount of time; about 5 seconds or so. After that, the device rapidly decreases current flow to a steady state of about 100mA. That results in a total power dissipation of about 1.6 watts. This is very unlikely to cause a fire should a solenoid get stuck ON. Without this resettable fuse, 32 watts would be dissipated and that could cause a fire.

After power is removed, or some kid stops pressing the doorbell button, the fuse returns to normal in just a few seconds.

Attached is a picture of the device, one with some heatshrink used. I would have preferred to use the thru-hole version of this fuse, but this surface-mount device was the only style we had in stock. This tiny device will get hot under a short circuit condition, so keep the device suspended in free air. Do not try to heat-sink it as that defeats the whole purpose of the device; it is supposed to get hot!

knock (author)  gentleLion5 months ago
GentleLion- Thanks for the note. Yes, I have observed that tilting the dashpot can “restore” operation. I have not passed that tip on to owners of them as I think it’s just a bad idea to use these. If the action ever stalls and leaves a solenoid powered on, it becomes a little heating coil that could theoretical cause a house fire. Your advice to add a fuse is an excellent idea that could address that risk, if done right- and you know- actually used and not just bypassed if fuse/s pop.

Your observation that the volume control would act like a fuse and usually go first is true, but regardless, in that case it’s the volume control instead of a solenoid field coil that becomes the heating element that might cause ignition.

Of course, that risk exists to some degree with any solenoid-struck chime.

Whatever, these are just so troubled that I don’t recommend using them. If I’m not mistaken, many vintage electric devices that are filled with oil, contain PCBs. I don’t know if these do or not, but add that to the possible problems with these. KDB

knock (author) 5 months ago
Multi-note chimes latch onto power after the momentary press of the button. Note sure how long a Ritt 520 runs, but 10 seconds is likely. It would be great to find a fuse solution that would work for all sorts of momentary 2-note chimes as well as motorized multi-note chimes that might take 12 seconds or so to run, and chimes that are powered by transformers in the range of 8volt/10watts to 24volts/ 20 watts. The risk of burning out a chime volume control or solenoid field coil is not something measured in seconds, more like minutes or maybe hours of constant power.

JonAMax10 months ago

I have a Rittenhouse Model 552(?) but it only plays 7 notes. What do I need to do to get it to play the missing note. The sequencer seems to be wired correctly but what do I know...please help

knock (author)  JonAMax10 months ago

It probably needs service . Contact me through www.knockdoorbells.com and we can take it up from there.

AdamN151 year ago

Hi - just found this topic. I was in touch with Knock a while ago. I'm looking for a solution to replace the dashpot for a Rittenhouse 550 with 4 solenoids, chiming 8 notes. Did anyone ever solve this challenge? If so, I'd be interested in buying a replacement electronic sequencer - and whatever else I need to get the chimes working (transformer?). If I can't replace the sequencer, I might be in the market for a working 550 if anyone has one.
Thanks in advance - please contact me at adamnelson@comcast.net.

knock (author) 2 years ago

Sylvia- you have something entirely different from the topic of this discussion. The RC prefix suggests 1980s vintage or maybe later, for sure a number of decades after the last dashpot model was made. If you like, catch up with me at knockdoorbells.com and show me what you have.

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