ZW repaired with issues

The laminations look pretty tight where it matters. The block of them might be better secured by the bendable tabs holding it.

Hi Bimmer050 - you can learn a bit more about humming/buzzing right here - this will explain where your hum (in all probability) is coming from. Then when you're doing reading that, follow my adventures in getting rid of the hum in my ZW right here

I kind of doubt that the repair tech did anything to cause the hum. My guess would be the shipping may have loosened some 50+ year old laminations, and that will definitely cause some humming. 

Look right here for info on your diodes - at 45 volts they are ok, but the 8 amps is just a wee bit on the light side, IMHO. Mind you, I do NOT claim to be an expert, but the stud diode I bought was at least twice that.

cjack posted:

The laminations look pretty tight where it matters. The block of them might be better secured by the bendable tabs holding it.

OK, I might try shimming temporarily. Might get a tighter fit than bending the tabs (it looks like someone already tried that).

GeoPeg posted:

Hi Bimmer050 - you can learn a bit more about humming/buzzing right here - this will explain where your hum (in all probability) is coming from. Then when you're doing reading that, follow my adventures in getting rid of the hum in my ZW right here

I kind of doubt that the repair tech did anything to cause the hum. My guess would be the shipping may have loosened some 50+ year old laminations, and that will definitely cause some humming. 

Look right here for info on your diodes - at 45 volts they are ok, but the 8 amps is just a wee bit on the light side, IMHO. Mind you, I do NOT claim to be an expert, but the stud diode I bought was at least twice that.

Hi GeoPeg,

Thanks for the link to Tranz4mer's ZW page...I've seen that before but was hoping to avoid major surgery on the core.  Rough shipping may indeed be the cause...one handle was broken in shipment as the ZW was not double-boxed coming back like I sent it out.

Thank you for the diode page. At least now I know what was installed. The 1N1190AR is a 600V 40A stud diode which is substantially heftier than the 45V 8A I have. 

Can anyone on the forum enlighten me why a 600V 40A diode might be specified for the whistle circuit?

Roger

I can think of two reasons why a 40 amp diode was specified. The first is simple; bigger is better - or stated in other terms, overkill is better than not enough.

The other reason might be to handle a dead short that could occur just as you are blowing the whistle. I stole the following explanation from LIONELSLONI :

When you work the whistle control, it first replaces the direct connection from the roller with the 5-volt winding in series with the rectifier. This gives a strong DC voltage intended to operate the whistle relay. But the motor will slow down. Then, as you move the control farther, it should connect a 1.5 ohm resistor in parallel with the rectifier to get the voltage back up to a reasonable level, with only a small DC component to keep the relay closed. If you work the control quickly enough, the train will not have enough time to slow down while the control is in transition.

So for that brief instant before the 1.5 ohm resistor is hooked in parallel with the diode, it is possible to dump all of the ZW's 14 amps directly through your diode. That could be an issue I think, for an 8 amp diode.

GeoPeg posted:

I can think of two reasons why a 40 amp diode was specified. The first is simple; bigger is better - or stated in other terms, overkill is better than not enough.

The other reason might be to handle a dead short that could occur just as you are blowing the whistle. I stole the following explanation from LIONELSLONI :

When you work the whistle control, it first replaces the direct connection from the roller with the 5-volt winding in series with the rectifier. This gives a strong DC voltage intended to operate the whistle relay. But the motor will slow down. Then, as you move the control farther, it should connect a 1.5 ohm resistor in parallel with the rectifier to get the voltage back up to a reasonable level, with only a small DC component to keep the relay closed. If you work the control quickly enough, the train will not have enough time to slow down while the control is in transition.

So for that brief instant before the 1.5 ohm resistor is hooked in parallel with the diode, it is possible to dump all of the ZW's 14 amps directly through your diode. That could be an issue I think, for an 8 amp diode.

That's a great explanation; there's more going on behind the whistle control than I realized. Thank you for sharing that. Also I was looking around but couldn't find a chart that shows the maximum current the various transformers put out. Good to know the ZW is 14A.

I once read on this forum that the ZW can weld into a dead short before the old thermal breaker kicked in...I have some 1122 switches from 30 years ago to prove that! (geez, 30 years ago seems like a long time ago, but then to realize that was in the mid-1980's which doesn't seem long ago at all...but I digress...)

Well, I just received two 1N1190AR's in the mail so my next project is to install them in the ZW. I can re-use the 45V/8A diodes in my 1033 and RW transformers.

Roger

30 years ago, eh? Somewhere around 1964 I was in an electrical experimentation phase of my young life. I sharpened BOTH ends of a #2 pencil, grabbed some lamp cord wire, attached alligator clips to one end of each wire with the other ends going to A and U. I then hooked up the clips to each end of the pencil. After a few seconds of "full throttle", the pencil started smoking, eventually burning and cracking right off the pencil lead, then I watched the pencil lead glowing bright red, til I tired of this dangerous vocation. Not too surprised that I had to overhaul my ZW in later years!

HAHA! I'd never thought to do that. Quite a curious mind...at least the circuit breaker didn't trip!

I feel a need to share an update on the ZW repair I got in April. Two weeks ago, one of the rebuilt whistle controls quit; I confirmed that one of the 45V-8A diodes failed. It was working one day, and the next day the whistle control would not work. I've since replaced both diodes with the 1N1190AR stud diodes which I expect to put an end to this story. Now that I've done it, it's super easy with Tranz4mer's ZW diode page -- excellent documentation!