Anyone build with a Mercury Magnetics P45RS

[studiodunn]

Be careful when fusing variacs of this size. It is normally 5A but I have bought them with 12A fuses in there!

This cheapo model had a 5a fuse and it stayed in tact.

Thanks again for the help

Ooff. Glad that you have it figured out, but that's unfortunate. Loud humming from transformers or a Variac (an autotransformer) is a red flag. I guess neither the ammeter or the fuse was enough to save the Variac.

I would say no to running 120V into the 100V primary. That will put the filaments at 20% over voltage, shortening their life significantly.

I know very little, but I know what unhappy electricity sounds like.
Thank you.

With 120/240 primary, look for 2 pairs of wires. In my experience, the set up is a split primary. For 120 the setup is to use them in parallel. For 240 use them in series. They need to be in phase. In other words, it is really (sort of) two 120 windings.

So when I charge up the white and black I get all expected voltages at 120v. MM told me the white was 120, so is it safe to say that is the right pair? Meaning no other lead would give me the right voltages in conjunction with the white?

[martin manning]

So when I charge up the white and black I get all expected voltages at 120v. MM told me the white was 120, so is it safe to say that is the right pair? Meaning no other lead would give me the right voltages in conjunction with the white?

Are there any other leads that have continuity with the white and black? Is there another pair of leads that have continuity with each other and show 120V when you apply power to the white and black?

[gktamps]

Doesn't Mercury have a wiring diagram for this transformer available to you? You said you talked to them, but can't they provide a PDF of the diagram?

[Reeltarded]

They don't show any spec sheet. They harlu show ANY spec sheet. It's a real bother to me. They seem to charge for a spec sheet.

[studiodunn]

So when I charge up the white and black I get all expected voltages at 120v. MM told me the white was 120, so is it safe to say that is the right pair? Meaning no other lead would give me the right voltages in conjunction with the white?

Are there any other leads that have continuity with the white and black? Is there another pair of leads that have continuity with each other and show 120V when you apply power to the white and black?

There is continuity between all 5 of the small leads

[studiodunn]

They don't show any spec sheet. They harlu show ANY spec sheet. It's a real bother to me. They seem to charge for a spec sheet.

Yeah their documentation sucks.

[Phil_S]

There is continuity between all 5 of the small leads

OK, then there is hope of figuring this out. It might be a little tedious. I would try to figure out (as best I could) if there is some order to them. If there is continuity among them, it suggests one long winding. The two outer leads will show the greatest number of ohms (longest wire length.) There is probably one in the middle, a sort of CT, but can't say for sure. I think there are 10 possible combinations. Make a chart and test each possible pair for ohms. This should give you a good idea of the position of each lead on the winding. Take a piece of tape and label the leads a-e. Here's the list of possible combinations: ab, ac, ad, ae, bc, bd, be, cd, ce, de. It is likely that 120 is a pair of inner taps. Some amount of guessing will be required. Once you have an idea, you can run low voltage on the HT secondary to see what comes out on the primary. You'll need to check all of the possible combinations. The voltage ratios should complete the picture.

[martin manning]

So when I charge up the white and black I get all expected voltages at 120v. MM told me the white was 120, so is it safe to say that is the right pair? Meaning no other lead would give me the right voltages in conjunction with the white?

Are there any other leads that have continuity with the white and black? Is there another pair of leads that have continuity with each other and show 120V when you apply power to the white and black?

There is continuity between all 5 of the small leads

ok, so it seems like you have something like this then. When you have 120V on what you believe to be the 120V tap measure the voltage on the others from what you believe to be the 0V lead. Then you should read the voltages for the other taps directly. If the readings don't line up properly you may have to change your assumption on which lead is 0V. If what MM told you is true (white is 120V), then you could be applying power to the 240V instead of 0V and still get the right voltages on the other windings.

[gktamps]

Yes, it may be somewhat similar but not identical to the APD non-RS version in the attached photo.

There was a 2007 discussion on the Metropolous forum about this transformer - If I speed-read through properly, Jim at Scumback Speakers used one and had similar difficulties identifying wires.
http://forum.metropoulos.net/viewtopic.php?t=14960

MM are jerks.

[studiodunn]

Are there any other leads that have continuity with the white and black? Is there another pair of leads that have continuity with each other and show 120V when you apply power to the white and black?

There is continuity between all 5 of the small leads

ok, so it seems like you have something like this then. When you have 120V on what you believe to be the 120V tap measure the voltage on the others from what you believe to be the 0V lead. Then you should read the voltages for the other taps directly. If the readings don't line up properly you may have to change your assumption on which lead is 0V. If what MM told you is true (white is 120V), then you could be applying power to the 240V instead of 0V and still get the right voltages on the other windings.

So if I did this right
@120v on black/com & white/hot I get all the other voltages expected. B/W=100v, Brown=220, Blue=240

[studiodunn]

Yes, it may be somewhat similar but not identical to the APD non-RS version in the attached photo.

There was a 2007 discussion on the Metropolous forum about this transformer - If I speed-read through properly, Jim at Scumback Speakers used one and had similar difficulties identifying wires.
http://forum.metropoulos.net/viewtopic.php?t=14960

MM are jerks.

Thanks. I've read that thread a dozen times hoping I missed some gem of info. This is the only photo of the actual transformer in use I have found. Now knowing what I think I know, the image looks to show the white and black being used at the primary.

JTM45chassisbirdseye.jpg

[gktamps]

Seems so. There are also hints about the center taps, right?
You might ask Jim at Scumback Speakers.

[studiodunn]

yes, the info i got from MM about the CT's seems to hold true when i was measuring voltages.

[martin manning]

So if I did this right
@120v on black/com & white/hot I get all the other voltages expected. B/W=100v, Brown=220, Blue=240

If those are your measurements, then it looks like you have it all figured out, and black and white are your 120V primary. I guessed at the 220 and 240; could have been 220 and 230, or 230 and 240.

[studiodunn]

Thanks again to everyone involved in helping me with this.

i think I'll go ahead an d make a wiring diagram in case the question ever gets asked again.