Wreck PT/Lamp limiter testing

[Herzog]

I’m testing my PT for an Express build

It’s 280-280 on the secondaries and I’m getting 502V ac when testing.

My heaters show 5.2v ac.

Unloaded of course. I'm guessing the low voltages are due to the lamp limiter

What concerns me though is that my lamp limiter is staying lit. I’ve only powered up for a couple of seconds at a time.

Is it normal for a lamp limiter to remain lit when testing like this? I don't recall this from previous builds

[martin manning]

You should be seeing some glow in the limiter bulb due to core losses. Using a 60W clear bulb I can see the filament wire glowing orange, and 565VAC across the secondary when powering an unloaded 'wreck PT. With no limiter it's 600VAC, so a 60W limiter reduces the voltage by about 6%.

[Herzog]

Thanks Martin

Decided to check voltages without the limiter and the fuse popped so I guess there’s something up with my PT or my wiring.

[Herzog]

Turns out to be worse than just the fuse popping



Wiring diagram (wired for 240v, with the 120v neon powered from one winding of the primary)



Any clues from the much smarter guys here as to what might have gone wrong here?

[pompeiisneaks]

First off are you wiring for 120V or 240?? It's hard to say for sure with your picture, but it seems to me you've got black and white/black connected to the switch so that means 240V. What I can't see is do you have the black/white and white jumped together? Just wanting to understand the whole picture. Yes if the MOV blew then you're drawing way too much current. It may be the transformer is bad, or it may be one of the wires is grounding that shouldn't etc. Can you get a bigger picture of the whole wiring you've got for the PT?

~Phil

[M Fowler]

So for the full 240 are black/white and white tied together? The other wires going to switch?

[Herzog]

Thanks for the input guys. Well, the current draw explains the lamp being lit rather than glowing..

It’s wired as in the diagram. Have checked it tens of times.

The black/white and white are jumped together on a terminal strip beyond the neon, hopefully its visible on the second pic.

[pompeiisneaks]

You've maybe thought of these, but I think two things could be wrong:
1. I can't see super well, but the jumpered middle connection on the terminal strip 'may' be making contact to chassis, just double check with a continuity to chassis test... probably not it, but I can't see in there very well
2. it MAY be a bad MOV. Just was wrong from the factory and smoked, or they accidentally marked a 120V type with 240V? You're doubly sure they sent you a 250V rated MOV? most days line voltages at least in the US can sometimes hike up a bit and I think I read here that sometimes it's best to have that MOV be 5 to 10 V over the wall voltage to make sure it's okay. (even the Rocket layout shows the mov rated at 130V here for US 120 line voltages) That's about all I can think of that excludes it being the PT itself. You could at least temporarily remove the MOV, retest and see if you're still getting the bright light, if so it's more likely the PT itself. If not, maybe it was a dud?

~Phil

[Herzog]

Thanks Phil

There’s no continuity to ground from the primaries or the jumpers connection. The primaries read around 7 ohms across them

I’ll remove the the mov and test again with the lamp on. Hopefully it’s an under spec or faulty mov and not a dud PT.

Will post results, likely tomorrow.

[mrn1ngstr]

Its probably not, but thats not a progressive switch is it? Also, are you certain that its wired to the switch correctly? I know you said the transformer leads are in the right order but aren't you basically throwing a resistor/diode combo in to the mix adding in that lamp where it is?

[Herzog]

Thanks for chiming in.
A progressive switch? Not sure what you mean here.
Disconnecting the neon had no effect on the current draw with the lamp limiter. I am thinking a 240v neon would sit better here though.

[mrn1ngstr]

If it were a progressive switch, the toggle would have more than two positions. From off to standby to on, in one switch. I only ask because that appears to be a carling switch, and they make a progressive in the same product line as yours. I'd say a 240V would probably be a smart move.

[Herzog]

Ok thanks for clarifying, I thought that was what you meant.
It’s a DPDT as specced. Two position on/off.
Good suggestion, thanks again for putting it forward.

[rooster]

No. The Primary wiring calls for the black wire to be combined/joined with the white wire on the switch at one tab, the black/white and white/black to be joined together on the adjacent/parallel switch tab - and then the AC is parallel on the lower two switch tabs. I don't see this. Run your AC to the bottom lugs of the switch first. When you have the correct wires on the other two tabs of the switch, run some small wire (20 gage) from there to the AC panel light. Don't hang the AC on the light. When you flip the switch 'ON' the AC will light. Also it seems you have your Filaments connected to the AC supply for the Rectifier if you are reading 5.3AC? If not, your Primary must be goofing this reading up if you are reading the two brown wires. Weird.

If you are just checking your tranny, don't use a limiter - the limiter is to slowly engage the power supply caps. Plainly these are not hooked up yet.

And this is for 120 volt operation.

[pompeiisneaks]

No. The Primary wiring calls for the black wire to be combined/joined with the white wire on the switch at one tab, the black/white and white/black to be joined together on the adjacent/parallel switch tab - and then the AC is parallel on the lower two switch tabs. I don't see this. Run your AC to the bottom lugs of the switch first. When you have the correct wires on the other two tabs of the switch, run some small wire (20 gage) from there to the AC panel light. Don't hang the AC on the light. When you flip the switch 'ON' the AC will light. Also it seems you have your Filaments connected to the AC supply for the Rectifier if you are reading 5.3AC? If not, your Primary must be goofing this reading up if you are reading the two brown wires. Weird.

If you are just checking your tranny, don't use a limiter - the limiter is to slowly engage the power supply caps. Plainly these are not hooked up yet.

And this is for 120 volt operation.

I asked earlier if it was 240 and Herzog confirmed it was. thus the discussion about the two leads being joined together. Sounds like Herzog will try without that MOV, and we'll see from there. It seems to me it's wired correctly for 240V, if, on the other hand I misunderstood, you're 100% right its wrong for 120.

~Phil