Lowell Remote power control unit repair

norwintd

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Fight Leukemia
Hello All,
Has anyone repaired one of the Lowell RPC Remote Power Control Units. I have two from different racks with, I believe, bad transformers in them ( relay just chatters when activated). I hate to spend $200+ per new unit when all they need is a new transformer. My problem is I haven't been able to find replacement transformers based on the numbers on the transformers. Any help would be appreciated as always.
rpc1.jpg
rpc2.jpg
 
What's the secondary side voltage? 120 down to ?...Nevermind, I see it in the photo now. Several big box stores carry transformers for HVAC & Doorbell relays that go from 120 to 12 or 24 - just might not be the footprint you are looking for.
 
That is not a typical failure mode for a transformer. The secondary voltage should be around 18 V AC. Are there any electrolytic capacitors on the board? Those frequently fail from heat and age, and are cheap to replace. Very likely a dead capacitor.
 
That is not a typical failure mode for a transformer. The secondary voltage should be around 18 V AC. Are there any electrolytic capacitors on the board? Those frequently fail from heat and age, and are cheap to replace. Very likely a dead capacitor.
Here are interior photos of the unit in question. I will also vote for the 100uf 50v electrolytic capacitor as being the culprit. Only other components are two diodes and a resistor plus the relay.
@norwintd, does it look "domed" or leaking anything?
 

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In my experience, many electrolytic capacitors go kaput with no physical signs. That one lives right next to a heat source.
 
looks like $1.10 in parts and a bit of not-so-fiddly desoldering. Just pay attention to the orientation of the cap during reinstallation.
 

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