What to look for in a PW ZW 275 prior to purchase?

One of the big ones is look at the power cord, if it looks really old that is not a good sign. The handles should neither be loose (usually as sign of a problem with the rollers inside being broken IME) or too stiff (could be internal components have fused from not being used).  I would ask outright if the seller ever had it serviced and when, if the guy says no, I would not recommend buying it.

In terms of with power, a voltmeter should be able to show that the voltage increases as the handle is moved, the max is I think around 18v give or take. Make sure when you push the direction button, that the power cuts out. You can't test the whistle controller with just a meter (?). You also can test the fixed output, to make sure the voltage is reasonably within where it is (like if it is 14v, should be 13.5-14.5 or so).

If it were me? If it is relatively cheap (these days ZW's are not expensive) at all, I would take it to a service place and have it checked out. It will cost a bit, but it will mean you know it is working right and is safe. If you pay like 35 bucks and spend 100 to get it repaired, it is worth it IMO. On the other hand if the guy is selling it for what I typically see, like 90 bucks or so, and doesn't know or won't tell you the repair history, walk away.

Tom, top issues with the ZW are the power cord, the rollers, the rear binding posts, and the whistle rectifier and switches.

The rollers are very important as if they're worn down they can score the windings and kill the transformer!  If I were buying a used transformer, I'd open it up and check to see if the rollers have worn down enough that the arms have scored the windings.  Reject any transformer that has happened to.  The cord, binding posts, and the whistle rectifier can be repaired, so those aren't as pressing.

Years ago I used to rebuild these, but I gave that up.

The other item to check is the circuit breaker or at least ask about. Some of the sellers on the auction sites show the transformer with the cover off to show off the rollers and condition of the windings.

Pete

@Tom Tee posted:

Will be picking up a PW "Z" 275.  Will only have a multi-meter.

What should I check out?

How should the handles and dials "feel"?   How should the winding "sound"?

Just guessing that there should be  absolute zero output at full off?

Max reading at full on is_____?  Each circuit?

Any thing else?

Thank you...

Adding to the good advice already provided.  All four outputs should be 0 when off, ~8 Volts when the throttle is barely open, and around 19-20 Volts at full throttle, all with no load.  If the rectifier discs (or replacement diodes) are working, there should be about 5V DC between U posts and the corresponding A and D posts when the whistle button is activated.  If not, the rectifiers are fairly easy to replace.

I would also suggest walking away from a transformer if it generates any noticeable heat with no load connected.

To remove the top cover, remove the 4 Phillips head screws in the top cover, the red and green lamp covers unscrew, and the two bulbs are bayonet base that are pressed down and turn counter-clockwise 1/4 turn:

Look for any signs of charring, excessive wear on the windings from current or previously worn rollers.

The roller diameters when new are about 3/8".

Look for any "repairs" that don't look right to you.

May seem obvious but...

In addition to the above (all great advice) what I looked for was who I was buying from. There were a handful of guys here who specialized in transformers, including ZWs, who were reliable,  known to do great work, and stood behind it. I bought one years ago from a long-time forum member.

Of course, it's been so long that I can't remember who it was.    I'm sure some others may chime in.

I'm still the new guy around here and know just enough to be dangerous. My experience has been the best way to know is a proper inspection by taking the 4 screws on top and the cover just lifts off. You can see first hand the condition of the rollers, any repairs, the core transformer condition and so forth. Testing by feel, unless you know the difference between good and bad, I would think that is risky. And then you get into electrical details. Example I knew one guy who was very abusive and burned out more than one ZW 8V winding. Once that winding fails, that transformer is going to run hot, and not output full voltage- but it still outputs voltage. In other words, it's damaged, and sure, certain tests like max output and starting voltage can help detect it, but the heat aspect- to tell takes it being plugged in and or using some form of AC power meter to see idle power draw.

Hands down, your best bet is one properly serviced and tested by someone who knows this transformer like the back of their hand.

In case you haven’t removed the cover on a ZW before, its best to remove the green and red lenses and bulbs before trying to lift the cover off. Many times the bulbs have been replaced with ones with larger globes and will break when lifting the cover.

Pete

I can recommend Kent as he does a top notch job of rebuilding transformers.

Tranz4mr’s Home Page