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New owner SE84UFO (Read 327 times)
tomy2
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New owner SE84UFO
04/27/21 at 15:43:48
 
Hi there, I just picked up a used SE84UFO and am loving what I'm hearing. It didn't come with a manual of any sort so was hoping I could get a couple of questions answered here.

In regards to the switches...

There is a switch in front of each set of binding posts. What do they do?

The two switches in front of the input tube I believe are 1) to the left is for the rca inputs 2) high and low bias   Is this correct?


I have a few rectifier tubes I'd like to try with the amp. Does anybody know if a Western Electric 422a is compatible?

Thanks for any help!
Tom
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ArtMan
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Re: New owner SE84UFO
Reply #1 - 04/27/21 at 15:50:00
 
The manual is at the bottom of this page.

https://www.decware.com/newsite/SE84CKC.html
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Lon
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Re: New owner SE84UFO
Reply #2 - 04/27/21 at 16:14:39
 
The switches on the back should be to match the speakers you have, one lower and one higher setting. See which works best.

Regarding the 422a I found this:

"The WE 422A may be the best ever 5U4 upgrade design - it's a direct plug-in for most later 5U4's with octal bases."

That was on this page: http://www.hifitown.com/index.php?dispatch=products.view&product_id=30045

In your shoes I would try to get Steve on the phone and verify this first--that's a very valuable tube that you wouldn't want to damage.
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tomy2
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Re: New owner SE84UFO
Reply #3 - 04/27/21 at 17:23:19
 
Thanks for the link on the manual. I've seen that page but I guess I never scrolled down far enough to see the manual pdf.

I'll put in a call to Steve to see on the compatibility with the WE422a. I've used it with great success in a Melody 845 amp as it sounds glorious.
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JOMAN
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Re: New owner SE84UFO
Reply #4 - 04/27/21 at 23:38:16
 
I checked into this some time ago as that was THE tube that I wanted to try.  What I could find is that the WE 422A input cap value is specified as 10uF.  The first cap in the UFO is 47uF.  Very risky! Especially on a tube as costly to replace as the WE 422a.
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CAJames
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Re: New owner SE84UFO
Reply #5 - 04/28/21 at 00:09:27
 
Quote:
Posted by: JOMAN      Posted on: Yesterday at 23:38:16
I checked into this some time ago as that was THE tube that I wanted to try.  What I could find is that the WE 422A input cap value is specified as 10uF.  The first cap in the UFO is 47uF.  Very risky! Especially on a tube as costly to replace as the WE 422a.


I've never heard of anyone having trouble with a 422A because the input capacitor was too small. FWIW the data sheet that I found:

http://www.the-planet.org/gkaufman/pdf/WE422A.pdf

Says the "typical" (not minimum) input cap should be 10 uF. It also says the maximum transient current per plate is 4 amps, and I don't think a UFO is going to come remotely close to that, esp. since the 422A is indirectly heated and therefor turns on gradually. I wouldn't hesitate to use a 422A in my UFOs, but that is JMO/YMMV of course.
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JOMAN
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Re: New owner SE84UFO
Reply #6 - 04/28/21 at 02:45:41
 
See the link:
https://www.decware.com/newsite/SE84CKCowner.pdf

This makes reference to a 274b and that some will arc on start up because they are not compatible with the first 47uF cap.  There certainly are other variables that come to bear.  I did have a conversation with Steve when I owned my SE84UFO2, some time ago, specifically about the use of the WE422a.  He did not say that it would be a problem but that caution is warranted.  In fact he stated that a variac would be a consideration.

Having said that I have had two 274B that were supposed to be rated for use with a 47uF cap that arced on start up.  One in less than a year and one  on the very first start up, that cost me $400.00 and was I POed!  

I have used 5U4G variants that were rated for a max 40uF cap with no issues.  I have also tried a Valvo AZ1 mesh plate that was rated for 10uF at best and it survived, but I held my breath every time I turned it on.  It only cost me $80.00 plus the adapter, so I didn't care if it blew up like the 274b's.  I wanted to hear what it sounded like.

A WE422a costs far more than $80.00 and far more than my GZ34 metal base.  All I'm saying is that there is risk and that caution is warranted based on my experience.  I'd hate to see anyone loose a WE422a regardless of cost.
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CAJames
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Re: New owner SE84UFO
Reply #7 - 04/28/21 at 04:05:54
 
Sure, I'll never argue against caution. But Steve recommends, and sells, 5Y3 tubes and they have datasheet values for the first cap all over the map. Anywhere from 10 to 33 uF if memory serves. But I've never seen 47 uF for a 5Y3. So, yeah, I agree there is more to it then just the datasheet value.

I think, and again, JMO, it is really more about how the tube was made then what the spec says. That's why I'll take 60+ year old tubes everyday over current production.

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JOMAN
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Re: New owner SE84UFO
Reply #8 - 04/28/21 at 12:44:15
 
think, and again, JMO, it is really more about how the tube was made then what the spec says. That's why I'll take 60+ year old tubes everyday over current production.

Couldn't agree more.  That is why I'm now squarely in the NOS camp and paying more than I'd like, to get both the performance and longevity.  I also think that it is a combination of both specs and quality of construction.  The AWV AS4 are built like the proverbial brick outhouse and worked even though they did not meet the 47uF spec, as did the AZ-1.  Although I have to admit that I was surprised that it did not arc.

One of the concerns with respect to the WE422a was the ability of any production in any time period to meet the type of tolerances that would be required to be met in the execution of the design.  That combined with the specs gave reason for caution.  However, if I were given the choice of using the new 274b that arced and met spec or the WE422a, no brainer... WE422a hands down.

When I turn on the amp and per amp I am always amazed at how slow and gentle the start up of the GZ34 Metal Base is.  Probably contributes to it's reported longevity.

Too many hobbies and a limited supply of funds force me to put the WE422a on my bucket list.
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