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Old 16th March 2011, 06:06 PM   #1
BHD is offline BHD  United States
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Default RH84 SE Build and custom Edcor power transformer

I'm building an RH84 SE and am planning to use 12AX4GT series damper diodes as rectifiers. I like using them because of their performance, built in delay and also since they cost next to nothing.

The specifics of the transformer (XPWR180-120) are:

275-0-275 at 100mA
6.3 at 2A for the power and driver tube filaments
12.6 at 1.5A for the rectifier filaments

I designed a power supply in PSUD using the Radiodaze choke (part number RDC-100 specs: 8H, 125mA and 150 ohms series resistance and 500V max) as a pi filter with a 20uF input capacitor and a 200uF cap after the choke and it sims pretty well. The chokes are only seven bucks if you order five or more and are a screaming bargain.

I just wanted to let folks know about the availability of the transformer since this is a popular project and now that I've set it up anyone can order it.

Dealing with Phyllis at Edcor was a pleasure, BTW.

I'll be posting the results of my build in this thread when I've got parts in hand.

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Old 16th March 2011, 06:21 PM   #2
bichela is offline bichela  United States
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Quote:
Originally Posted by BHD View Post
I'm building an RH84 SE and am planning to use 12AX4GT series damper diodes as rectifiers. I like using them because of their performance, built in delay and also since they cost next to nothing.

The specifics of the transformer (XPWR180-120) are:

275-0-275 at 100mA
6.3 at 2A for the power and driver tube filaments
12.6 at 1.5A for the rectifier filaments

I designed a power supply in PSUD using the Radiodaze choke (part number RDC-100 specs: 8H, 125mA and 150 ohms series resistance and 500V max) as a pi filter with a 20uF input capacitor and a 200uF cap after the choke and it sims pretty well. The chokes are only seven bucks if you order five or more and are a screaming bargain.

I just wanted to let folks know about the availability of the transformer since this is a popular project and now that I've set it up anyone can order it.

Dealing with Phyllis at Edcor was a pleasure, BTW.

I'll be posting the results of my build in this thread when I've got parts in hand.

How much does Edcor charge to make a custom power transformer? what is the minimum number of units required? I need something a bit different. Heres what I need, they have a stock unit that is close to your specs but. heres my needs
250-0-250 160-200ma (bigger is better) 5v 3A for 5u4gb rectifier) 6.3V 6A for filaments.

I can get an ugly toroid that would provide some of the needed juice but.. it is a bit weak on the 6.3v side (3A). It has no cover, sure, a coffee can would work but. egads! that looks lousy! My amp is called "Fire and Ice" so.. I found the edcor power/audio transformers match my theme pretty well. My life partner (Lumi) thought it would be wise to stick with the Edcor line since they are blue and match our project's theme. I also am ordering two blue tube shields for the 12ax7 phono preamp section.
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Old 16th March 2011, 06:31 PM   #3
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Edcor charges a one time 40.00 set up fee for any new design, but since your transformer looks pretty standard (the bugaboo with mine was the 12V secondary for the rectifiers), they may have a design already made that will match your specs.

They have a pretty good website with a lot of their previously designed power transformers listed with model numbers.
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Old 16th March 2011, 06:41 PM   #4
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Quote:
Originally Posted by BHD View Post
Edcor charges a one time 40.00 set up fee for any new design, but since your transformer looks pretty standard (the bugaboo with mine was the 12V secondary for the rectifiers), they may have a design already made that will match your specs.
Like this one: EDCOR Electronics Corporation. XPWR093-120

They also have a list of previous "custom" designs - don't have a link though...
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Old 16th March 2011, 06:47 PM   #5
bichela is offline bichela  United States
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Originally Posted by BHD View Post
Edcor charges a one time 40.00 set up fee for any new design, but since your transformer looks pretty standard (the bugaboo with mine was the 12V secondary for the rectifiers), they may have a design already made that will match your specs.

They have a pretty good website with a lot of their previously designed power transformers listed with model numbers.
Yes, I have noticed that website and I did look at what was online before I emailed them with my needs. They had one transformer that was 275-0-275 200ma that was close to my specs but... what a waste of 25 volts (per leg) to dump into a dropping resistor! My Amp is going to be hot enough without dumping unwanted voltage into heat.
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Old 16th March 2011, 06:50 PM   #6
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Well, 25V is pretty close and you'll probably have to muck about with it anyway when you actually build it.

BTW, for those that want to sim the power supply I mentioned above in PSUD, use a 6AX4-GT rectifier and the cap that comes after the choke is actually 220uF and not 200. Oops.

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Old 16th March 2011, 07:42 PM   #7
TheGimp is offline TheGimp  United States
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Originally Posted by bichela View Post
Yes, I have noticed that website and I did look at what was online before I emailed them with my needs. They had one transformer that was 275-0-275 200ma that was close to my specs but... what a waste of 25 volts (per leg) to dump into a dropping resistor! My Amp is going to be hot enough without dumping unwanted voltage into heat.
Then use a choke input filter and you can drop the 25V across the choke which will not be a dissipative loss. The power will be delivered to the filter cap at a lower voltage.
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Old 16th March 2011, 07:54 PM   #8
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Excellent idea on the choke input supply.

If the amp is a stereo amp you could use two of the Radiodaze chokes listed above - one for each channel - and have an almost dual mono power supply!
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