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Old 16th June 2009, 03:53 PM   #21
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Quote:
Originally posted by rknize
Also, if there is a short from hot to earth ground on the primary side somewhere (like the power switch), a fuse on the neutral won't even blow!
ah - now that's a good reason. This I could see happening with wires going through a chassis plate.

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Old 17th June 2009, 07:36 AM   #22
skipper is offline skipper  United States
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Default Auricaps polarity

Ok, so I will fuse the hot side, i've read some post that 2.5A slo-blow fuse is correct for the simple se? Does it matter if from the fuse, the hot goes to the blk/grn or the blk/white-grn/wht.

120 Volt Primary: Connect the two primary windings in parrallel.
Black adn Green connected together
Black/White and Green/White connected together

I got my Auricaps coupling caps but have a question. The caps are not labled with a +/-. From the board, C11 and C21 show a longer leg on the silk screen. I assumed that this was the positive side (like the longer leg of the radial legged caps). From the attached pictue, both caps have oppisite wire coloring to each other. Can I assume that if I install the caps where the lettering is upside down to the board that the polarity will be correct?

I will post some pictues of my hardware later sometime today.

Thanks,
skipper
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Old 17th June 2009, 11:44 AM   #23
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The auricaps have no polarity, either way is fine. I think that is in George's instructions.

I don't believe that there is any polarity to the power xfmr input - or you would have seen something saying so on the paperwork/spec. But I'll defer to others on this one...
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Old 17th June 2009, 02:53 PM   #24
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Default Re: can someone compare their wiring

All film/foil caps have no polarity, so you can connect them either way. If you visualize that the cap is built like a jelly-roll (it's a strip of mylar and a strip of foil laid on top of each other and rolled up), one lead is connected to the foil on the OD (outside dia) and the other lead is connected to the foil on the ID (inside dia). Some folks like to wire the foil OD side to the input (I think) for sonic reasons but I cannot notice any difference either way. They'll work just fine in either polarity.

If you buy boutique caps from Michael Percy, he puts a dot on the foil side before shipping them out. I typically wire them with the text facing the same direction for both caps (or all 4 for a PP amp), that way the foil ODs are all connected the same way (hopefully). That assumes that the text on the caps is always put on in the same orientation. I can just visualize caps shooting out of the cap-making machine into a big hopper and then going to the printing station in the factory.

On the transformer primary, wire as you have outlined above and connect the fused mains hot to either pair. The black/green pair would be my choice only because the other wires are both somewhat white to signify neutral, but connecting to either end will work.
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Old 18th June 2009, 01:50 AM   #25
skipper is offline skipper  United States
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Here are a couple of pictures of my board. I still have to add the coupling caps. I plan on running it on a test bench. The inputs and spreaker jacks, where should I run the ground to these for the bench test? Do I just run them to the ground on the power connector?
Also, I got the currently limiters from mouser, so these should come off the fuse and to the power transformer?

Thanks,
Skipper
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Old 18th June 2009, 03:11 AM   #26
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I wouldn't have the current limiter right off the hot line, place it after the switch. Btw I have the exact same transformer. It performs wonderfully.
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Old 18th June 2009, 04:34 AM   #27
rknize is offline rknize  United States
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Put one on the primary side and put another in series with the center tap of the high voltage winding. The first one will heat up right away as the heaters come up due to their large current draw. The second is there to limit current when the rectifier comes up to temp. It takes a long time for the 5AR4 to come up, but once it starts it comes up fast. Those big caps draw a lot of current even before the rectifier is up to full temp and that's hard on the tube.
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Old 18th June 2009, 06:13 AM   #28
skipper is offline skipper  United States
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I do hope these transformers sound nice as the reviews on this forum.

From looking at the schematic, I see that the high voltage CT grounds the two high voltage legs. I bought two current limiter just in case I needed and extra so I will add it to the CT.

Another question, tonight I completed all the soldering on the board. I double checked the resistors as a sanity check. Everything checked out except R2 150K 3W and R4 150K 2W. The both seem to measure in the M Ohms and the values change,, they are not stable. I even put clips on the resistors to get a good reading. Is there a reason these are reading funning (.421 M ohm ) or are they just bad?

Skipper
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Old 18th June 2009, 06:26 AM   #29
rknize is offline rknize  United States
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They are in parallel with the filter caps and are probably mucking with your meter. i suspect they are fine.
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Old 23rd June 2009, 06:40 AM   #30
skipper is offline skipper  United States
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Hey guys,

I am almost done with wiring up my bench top set up. I still have to connect up the OPT and add the tubes and I think I am done.

Should I ground the OPT and the PWRT cover to the inlet power conector ground (center pin) for the bench test?

Anything I should check before powering up? I added a current limiter to the high power CT and to the out let of the 2.5A slo-blo fuse.

Here are a couple of pictures of what I have so far.

Thanks,
skipper
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