Blown Power Tranny in a 140B?

[bcatchings]

Hey folks, long time no post but I'll get to it.

I think I blew the power transformer in my 140B. I've tried some of the tests measuring the resistance across the the different terminals of the transformer (it's shorted from ground to the outputs) and if you plug the thing in and turn it on it blows the breaker (the one for my room, not the fuse in the amp mind you).

I'm looking for some hints in determining if I'm correct (I'm going by the GeoFX debug by the way http://www.geofex.com/ampdbug/pwrtrans.htm) though it looks like I am and if so I'm wondering if you guys might know what the part number is, where I can find a replacement, and what it should cost me. It looks like MM has a wurli power tranny but I'm not sure which model it's for and I'm wondering if it's gotta cost me $100+ to get a new one. Your thoughts?

Thanks,
B

[bcatchings]

Just realized that the side of the transformer that's kinda scratched up on mine has what I assume are the part and serial numbers on it. I believe the part number is 11-0411 and what I assume is the serial number is 8316606. That help anybody out because neither are yielding any results on Google?

[Alan Lenhoff]

Years ago, Morelock's Organ in Mississippi acquired all the spare parts when Wurlitzer shut down its electric piano production.  They are sold out of many of the most commonly replaced parts (such as reeds), but they still have a good assortment of other parts, even for very early models. Email them with the part number and a description: morelocksorgan@frontiernet.net .  It often takes them several days to reply.

Alan

[bcatchings]

Thanks Alan. I forgot about Morelocks. I'm actually from MS and have talked to them many years ago for reeds for this same Wurli. I'll drop them a line and see what the word is on a power tranny just in case. In the meantime I'm still blowing the breaker in this room when I hit the amp with power. It never blows the fuse on the amp but today I saw something I dread, it smoked. Fortunately it was not the tranny or a cap or anything I really fear smoking (I know, fear everything that smokes)... no but it was right at the connection from the small red wire on the switch at the spot that it connects to the unshielded cable on the four pin molex. I'm starting to think I have a short in there somewhere. Maybe something that isn't supposed to be going to ground is getting shorted. That'd definitely give me smoke right? I can't come up with another reason it'd smoke from there and not in the amp. Actually now that I think about it the thing blew the breaker and smoked at that spot one time today without turning the power switch on. That's got to be a short.

[pianotuner steveo]

You definitely have a serious dead short, I would NOT attempt to power up again until you find the problem. This sounds like it is dangerous- like possibly starting a fire kind of dangerous....

[bcatchings]

I hear ya Steve. I suppose I'll rebuild my control switch wiring and see if that sorts it out. Thanks guys. But back to that first thought... how do you guys test your power transformers and where would you go to replace one (acknowledging Morelocks of course)?

[pianotuner steveo]

I guess you would see if the leads of the transformer read any resistance or dead short in this case. (Disconnected from power, of course)

I think a bad one will either read wide open or shorted. But again, I am NOT an expert in electronics.

I had one go bad once,on a model 700, and it just opened up, luckily, because someone ( not me) left it on all night.

If yours is a dead short it would read 000 ohms on a digital meter, if it is open ( I doubt it) the display will look the same as when the leads are not connected to anything.

The dead short could be elsewhere too.

[voltergeist]

I guess you would see if the leads of the transformer read any resistance or dead short in this case. (Disconnected from power, of course)

I think a bad one will either read wide open or shorted. But again, I am NOT an expert in electronics.

If yours is a dead short it would read 000 ohms on a digital meter, if it is open ( I doubt it) the display will look the same as when the leads are not connected to anything.

The dead short could be elsewhere too.

You should see 0 Ohms when measuring at the ends of a given coil.  A given coil should have an open circuit between itself and another coil or itself and the transformer core or case. 

Each coil in a transformer usually has the same color wire.  So, for two wires of the same color, you should read zero ohms (roughly).  For different colors, you should read an open circuit.  All colors should read an open circuit to the core and case.  All colors should read an open circuit to ground.

[pianotuner steveo]

Thanks for clarifying...

[pianotuner steveo]

So...could the primary and seondary coils in the transformer be shorted together? I think that s what I meant.

[bcatchings]

Just a little update... I put down my 140 for a bit in favor of playing some modeled stuff live but yesterday I had a moment to open it up and finish sorting out the problems with fresh eyes. Turns out there was indeed a short in the power/volume switch.

It took me a minute to find but (and I'm writing this for the benefit of anyone who is a little in the dark as far as troubleshooting) I did so by unplugging the input, speaker, and the whole cheek block wiring harness from the chassis. I took that as an opportunity to completely rebuild my wiring harness just to make sure. Still shorted. Then, with everything unplugged I checked for a short between the hot(x2) pins and the ground of the power socket. No short. I plugged in the harness for the volume and tremolo and checked it again. No short. I unplugged that and plugged in the power harness and checked again. There it was. Tracked that back to the switch. Turns out two of the three wires coming (one ground and one hot) were going to the same terminal on the switch. Not sure why or when I'd done it that way (most likely when I was swapping the "running light" for an LED) but as soon as I pulled it all was well.

It's playing well now and I'm going back to perfecting my other modifications!