Anyone build with a Mercury Magnetics P45RS

[studiodunn]

I have this PT ready to wire up in a build and talked to MM about the wiring since there is none available to actually look at. After getting the run down from them I realized that what i was told and what I have are different.

If anyone has used this PT can you chime in so i can get some confirmation on some things. Thanks

[Phil_S]

Can't answer your question directly, but figuring out a PT shouldn't be that challenging. I've done it many times. The good news is that you know what you have and what you expect of the windings. My best guess is the colors need to be sorted out. Here's what I suggest:
1) A photo showing all the wires, so we can see the colors and where they emerge from the end bells.
2) What are the expected primary and secondary voltage specs? Are any windings supposed to be center tapped?
3) Are you able to pair up (or if there is a CT, triple) the assorted wires, so we know the "end to end" pairs, and if there is a CT, too? To do this use your DMM and measure the Ohms. Either you'll get something or nothing. A CT will be roughly half, but windings are not perfectly symmetrical. The exception is if there is a bias tap that is part way along the secondary, but that, too, will become apparent. While you are at it, record the Ohms readings between various pairs.

Once we have this, we should be able to sort it out.

After that, you can run a low AC voltage on the primary to test it for voltage ratios. If you have a 10V source, that is ideal, but I use a 5V filament winding from a transformer I keep on the bench. If you put 5V into the primary and you get 10V on what you think is the high voltage secondary, then you know it is 1:2, so 120V in will give you 240V out. And so on.

Post the info. You'll get help. This isn't difficult.

[studiodunn]

Thanks Phil. i have a variac, so understanding the testing process will get me on the right track.

what i know
Secondary
Reds and Black have continuity = B+
Greys and Blue have continuity = 6.3v @ 2.5a per the info I got from MM.

Primary:
Greens and Pink have continuity = 2nd 6.3v @ 2.5a per the info I got from MM.
White =120
Brown = 220
Orange = unknown but has continuity to white and Brown, So I am assuming this is the Com.

Purple is a Ground per MM and has continuity to nothing else.

Now the 5 small wires are unknown and MM thought they may have been some part of a special request.

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[martin manning]

I would put 12VAC on the orange and white primary leads and see if you get 10% of the voltages expected on all the other windings.

[studiodunn]

I would put 12VAC on the orange and white primary leads and see if you get 10% of the voltages expected on all the other windings.

Thanks Martin. Do I need to ground the CTs back to the earth on the variac?

[Reeltarded]

To test? No.. stake all the leads firmly to a board and apply a measured and known voltage to the primaries then meter every lead on the secondary.

[martin manning]

Yes, keep all the leads separated so you don't accidentally short any of them. Painter's tape works well for that. Measure across the various windings and see if for example you get 0.5VAC across the 5V, 0.63 across the 6.3V, etc. The HV secondary will have 60-70V across it, so you still need to be careful.

[studiodunn]

So I set the variac to 12v AC, hook up the orange and white and got an ugly hum from the variac when i turned it on. Hums scare me

Even att 12v in I am getting 5v on the heater leads. Regardless I "think" know enough to know the variac is telling me something isn't right, me thinks.

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[imjonwain]

With no load but the meter you may get fairly high numbers on windings expecting a load. I don't know enough to say though in this case.

[Reeltarded]

Let's ignore the hum. I hear you. It's a little unsettling.. ignore it.

Let's not ignore 5v heaters at 12VAC. hmmmm

[studiodunn]

Let's ignore the hum. I hear you. It's a little unsettling.. ignore it.

Let's not ignore 5v heaters at 12VAC. hmmmm

We can definitely ignore the hum since the variac made smoke. Sooooo I need to come up with a new test supply. I think I have a 6.3v supply in the bin

Solved.The 22g. wires are the actually Primary feeds, The 18g wht/brwn/orange are 5v and 6.3v feeds. I obviously did a piss poor job of getting clear information on the call. I heard white + 120, brown + 240 and assumed they were the 18g wires.


My next question is, the amp has a 100v tap. Can this be used with 120v safely? Reason being to drive the B+ a bit higher.

[Reeltarded]

Yikes! This hum was louder than my hum.

You can always buy a 12VAC wall wart for something under $20 in a lot of places.

[martin manning]

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.

[Reeltarded]

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

[Phil_S]

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.