Have a transformer that makes the motor have a large humm

[rrebell]

Have a transformer that make engine motors humm loadly. I know it is the transformer because I have an identical one that dose not cause this. MRC  2500

[RR_Mel]

Is the momentum switch on?  If so turn it off and see if that makes a difference.

 

 

 

Mel

 

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

 

[rrebell]

Thought of that, and no it was off, redxid it several times just to make sure it wasn't stuck.

 

[RR_Mel]

If it’s an older unit a capacitor most likely crapped out.

 

There is a large cap under the PC board that filters out the AC ripple.  It might be showing some leakage.

 

The only picture I have is the one below, the cap is under the board on the top.  I should have taken more pictures while I had it apart.

 

 

 

 

 

 

 

Mel

 

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BigDaddy]

I think we decided you need a torx screwdriver to crack the case.  There are pictures of another MRC in the electrical forum.

[gregc]

rrebell

MRC  2500

 

this came up a while ago -- MRC DC throttle - zero setting (http://cs.trains.com/mrr/f/744/p/276542/3157945.aspx#3158157).  The 2500 generates PWM at 60 Hz which will cause some motor/frames to vibrate

[BigDaddy]

gregc

this came up a while ago -- MRC DC throttle - zero setting (http://cs.trains.com/mrr/f/744/p/276542/3157945.aspx#3158157).  The 2500 generates PWM at 60 Hz which will cause some motor/frames to vibrate

That thread says it needs a torx security bit, the screw has a center pin.

Making it clickable

[rrebell]

Transformer works great, just produces humm, not engine either.

[qwerty99]

Found this which may help you https://www.electricaldeck.com/2020/03/starting-of-three-phase-induction-motor.html

[Redvdub1]

"transformer"?  What make/part number?   

[rrebell]

Redvdub1

"transformer"?  What make/part number?   

 

MRC 2500

 

[Redvdub1]

ok..an MRC2500.  They have a pulse switch.  Did you notice the hum on both pulse switch settings?  (on or off are the settings). 

I "think" (and I invite any corrections..) that pulse "on" means that you are supplying 60 cycle pulsed power (half wave DC) through the whole range of throttle settings. If that assumption is correct  I would expect "hum" at the high throttle settings.  "Off" means that you get "pulse" power only at the low throttle settings and that as you progress the throttle to full power you gradually get filtered full wave 60 cycle DC and no "hum".  

If you get "hum" on both settings something is "wrong" with the non-pulsed setting.  And Melvin Perry's suggestion re electrolytic capacitors is very probable.  Look for the large blue cylinders on the circuit board/s.  They are the electrolytic caps.  Inspect for burn marks at the leads or ruptures on the cylinder surface.  They are easy to solder out and back in.  

Unfortunately, MRC has never provided any circuit diagrams for their hardware and precious few responses to inquiries.