All things LA2a related

[wave]

I blew one fuse. replaced it. I mounted the IEC ground up and I'm getting 110 VAC at the neutral (top left wired to transformer primary) and I grt no reading on the bottom left of the IEC (wired to B24) Also, even if the fuse is blown shouldn't I be able to probe the top right of the IEC and get 110?

 

[AnalogPackrat]

Yes, top right is always hot (if plugged in). Where is your ground clip? Do you have a ground on your outlet? Is your house/apt old? Seems like you have hot and neutral reversed. Check the outlet.

It's a safety issue (hot stops at the IEC if fuse blown), but this won't stop your unit from working. Have you checked the 250VAC secondary of the transformer?

 

[AnalogPackrat]

Also, you should be using slo blo fuses. 500mA in the US.

 

[wave]

I'm using 500mA slo-blo fuses If I probe the top right I get nothing (when plugged in) if I probe the top left I get 110 VAC is my apt wired backwards?
Why does all my other gear work. This sucks!!!

 

[AnalogPackrat]

Dood. Take your time and be methodical. Hot and neutral reversed isn't a good thing, but it won't stop your unit from working. It's AC. The transformer can't tell. Check your HV (250VAC) secondary on the transformer. Probe at B20 and B21.

 

[wave]

OK I got out the fluke meter and I'm getting the same reading 128 VAC on both the top left and top right of the IEC...So why do you think I'm blowing my fuses?

 

[wave]

I'm getting .005 vac on the red secondaries but i dont have my fuse in because it blows soon after throwing the power switch ( I'll throw the fuse in and test but it's my second to last one) What do you think

 

[bcarso]

I once salvaged a batch of power cords from the trash somewhere with the US convention on color code: black hot, white neutral, green safety ground. Three-wire plug on one end, breakout to a molex 0.156" pitch plug on the other.

I figured out finally why they were being discarded: black was actually connected to the neutral blade of the plug, white to the hot!!!

YOWWW

 

[AnalogPackrat]

So you blew another fuse? I'm having a hard time following what's going on. Unplug the thing and check your outlet. Put one probe in the ground hole and make sure its touching the contact, and then probe each of the other (hot and neutral) referenced to ground. Then probe between hot and neutral. What did you see?

 

[wave]

122 on what should be neutral. 112 on what should be hot and 122 between hot and neutral

 

[AnalogPackrat]

Smells like a 240V outlet. Check a different one in a different part of the house. I wish our electrician, Butterylicious, were around.

 

[wave]

OK fuse is in I'm getting 122VAC at these points...
IEC neutral
IEC top right
IEC bottom right
IEC hot
Turret B24 connected to
Power switch
Should I throw the power switch again (I'll probably blow the fuse again but I might be able to get a quick reading from A22,A23,A24, A25)

 

[AnalogPackrat]

I'm pretty sure that fuse will blow before anything interesting happens. You haven't changed anything. Did you measure another outlet or two? What has been plugged into this outlet before?

One more post and I'm calling it a night. Gotta work tomorrow.

 

[wave]

Same duplex powers this macintosh that im online with
Thanks alot for the help AP

 

[AnalogPackrat]

No problem. I'm not an electrician, but neutral is tied to ground back at the panel or the service entrance. You should get near 0VAC between ground neutral on a 120V outlet. I seem to recall that Macs have auto sensing power supplies so can take anything from 90-240V and figure out what to do with it.

Hopefully someone else will have a better idea tomorrow.

Later,
Analog Packrat

 

[wave]

If I probe continuity on the heater lines with the power tranny in place should there be continuity between every point? (i.e. before the power tranny was in place there was only continuity between all of the pin 9 wires but now there is continuity from pin 9 to pins 4-5 on each socket)

 

[wave]

I also found that my 6.3 V secondaries off the power trafo, even when lifted off of turrets B24&B25 are making continuity with ground. Is this right?

 

[SSLtech]

...It is if you have the center tap connected to ground...

Keith

 

[wave]

Yes I do
This is my primary wiring
1 black to B24
1 black to IEC neutral
red/yellow and green/yellow to ground bus (but i used tag 2)
1 red to A22 1 red to a23
1 green to A24 1 green to A25
Gray to IEC ground
I get continuity to ground through the green secondaries but not the red. Could this be the problem?

 

[Scenaria]

what do you mean by having used "Tag 2" for the center taps?

A22, A23 and A24, A25 look ok


be sure both of the center taps on the secondaries are tied to ground...

oh and if you really do have 120v sitting on your neutral.. I would suggest having an electrician come out to take a look at your service panel.. even if other stuff is working.. thats a big saftey issue...