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[MaxHeadRoom]

On a 3/4 HP motor that would have to be VERY large cap!
The quiet SCR style T.M. controllers do not use any caps on the bridge output. (2hp - 3...

[MaxHeadRoom]

I have never recalled seeing a motor choke included in any of these Triac style drives, they Have always been added externally, this includes any of the...

[MaxHeadRoom]

You don't normally find a smoothing capacitor on a Triac bridge version, just a series choke with the motor, maybe this one never had it?...

[MaxHeadRoom]

That is one of the simpler SCR bridge controllers, they rectify and chop the AC sine wave, so power is very 'noisy'.
Early TM motors controllers...

[MaxHeadRoom]

One example of Lamacoid panel, when reverse-engraved, it does not result in grooved front, it is done on the rear and eliminates engraving groove collecting...

[MaxHeadRoom]

What I do is get a local engraving Co. to make custom panels up in reverse-engraved Lamacoid.
The beauty of it is, you can cover the whole panel...

[MaxHeadRoom]

Worked on magnetic core memory in the old PDP-8 ,back in the 70's , the magnetic toroid had two conductors, or single turn windings, one was for writing...

[MaxHeadRoom]

The top one is a 2 pole motor and rated Definite Purpose, i.e. Compressor motor.

[MaxHeadRoom]

So it sounds as though it is the contactor itself, the retaining contact is somehow being held closed.
Either the contactor is sticking in, or something...

[MaxHeadRoom]

From my experience, machine control voltage has dropped from 120vac to 24vdc many decades ago, mainly because of Safety, LV LED devices, PLC systems,...

[MaxHeadRoom]

There is one other option if solid state is considered, and that is thyristor soft starters, AutomationDirect have a large selection of 1ph and 3ph, but...

[MaxHeadRoom]

I would also agree on keeping mechanical contactors as replacements, you could look at the Types Rated 'Definite Purpose' these are used in such as HVAC...

[MaxHeadRoom]

Many 1ph applications, are now going with ECM (Electronically commutated motors) , from HVAC to industrial types, A interesting one is the one now used...

[MaxHeadRoom]

I did the same for a short term job when I first came to Canada in the 70's , you often heard the expression, "One day they will make a flat TV set...

[MaxHeadRoom]

I remember the ones you carried in a suitcase, I used to tune my short wave radio in and overhear a few conversations! Some pretty lurid.
One amusing...