LW Won't Work Under Load

[gottcent]

My postwar LW transformer was working fine until recently, but it has now decided it will not work under load. If I connect a voltmeter across terminals U and A and slowly move the voltage control arm, I get the proper readings. But as soon as those terminals are connected to a load (either a small 520 engine or an operating accessory) the voltage drops to zero. (The constant voltage terminals do not seem to be affected.) I checked the circuit breaker and its contacts are closed. Any thoughts?

[lionelsoni]

Does the lamp light up?

 

[emdmike]

Sounds like a solder joint has gone "cold" and will conduct but not under a load, kind of like a loose battery cable on your car, will work till you try to crank the starter, which is a huge amp load.  Probably something simple.  If diving into the internals is beyond you means, leave it to someone that works on these.    Mike the Aspie

 

[ADCX Rob]

gottcent

...I checked the circuit breaker and its contacts are closed...

I was not aware you could see the contacts on the LW transformer circuit breaker.

The syptoms point to the breaker. Try actually running a jumper to bypass the breaker and check again.

[gottcent]

Thanks for your replies. Yes, the lamp lights up. I will follow up on your tips by searching for a loose connection and bypassing the breaker.

[lionelsoni]

The circuit breaker is in series with the AB and AC accessory circuits and also the pilot lamp.  That seems to rule out the circuit breaker as the culprit and to point to the whistle-and-direction circuits as the location of a high-resistance connection.