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6 WHY 6? R.I.P. 6X4 (Read 2671 times)
Rivieraranch
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6 WHY 6? R.I.P. 6X4
07/24/10 at 03:38:43
 
I purchased some NOS 1953 Sylvania 6Y6G in their original Leprechaun green boxes. They look mint and they tested fine. I had cleaned the pins with DeOxit and wiped them off. I placed them in the unit and turned on both sides. The left side amp would only light the 6Y6G's and the 12AU7 input. The other tubes (6X4; OA3, OC2) would not light.

I popped the 6X4WA into the tester and it would not light. What would cause this sudden tube death? I put the OC2 back in and it lit. I have to check the OA3 tomorrow.  

I replaced the 6X4, OA3 and OC2 and the unit works fine. I am so agitated by this experience that I cannot clear my head to evaluate the 6Y6 versus 6V6 sound.



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« Last Edit: 07/24/10 at 03:54:19 by Rivieraranch »  

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Rivieraranch
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Re: 6 WHY 6? R.I.P. 6X4
Reply #1 - 07/24/10 at 16:06:47
 
Balanced out the tubes
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Rivieraranch
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Re: 6 WHY 6? R.I.P. 6X4
Reply #2 - 07/24/10 at 22:59:29
 
From bad to worse. With the new Sylvania 6X4 rectifiers in place I turned on both sides. A light show ensued in the right side 6X4 rectifier and the whole unit went down. I guess it blew a fuse. I took the 6X4 out, tested it and it is shorted. I never had this trouble with the 6V6 tubes.  
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« Last Edit: 07/25/10 at 01:40:30 by Rivieraranch »  

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Steve Deckert
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If the 1st watt
sucks why continue?

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Re: 6 WHY 6? R.I.P. 6X4
Reply #3 - 07/24/10 at 23:41:37
 
A few tips:

1) The 6X4 is the limiting factor that determines the max allowable tube bias.  

2) All of the different output tubes that a mini torii can use draw different amounts of current (bias)

3) If an output tube is partially or completely shorted, it will take out the 6X4 rectifier tube on that channel.

4) There are two types of 6X4 rectifier tubes.  One is rated at a lower current, but works at higher altitudes that one might find in airplanes.  Using this lower rated 6X4 will be problematic.

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Rivieraranch
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Re: 6 WHY 6? R.I.P. 6X4
Reply #4 - 07/25/10 at 01:38:53
 
I noticed that the right 6X4 tube was rocking in the socket. That might be what caused it to short out. I put a new 6X4 in there and bent the pins outward slightly so they would all make contact. I changed the fuse and put in my Tung Sol reissue 6V6's, new 6X4's and all is well.  There did not seem to be anything wrong with the 6Y6's I tried.
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« Last Edit: 07/25/10 at 01:41:49 by Rivieraranch »  

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Rivieraranch
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Re: 6 WHY 6? R.I.P. 6X4
Reply #5 - 07/25/10 at 15:20:06
 
Looking at your suggestion about avoiding high altitude, lower current 6X4 types, I noticed that the 6X4WA and 6202 are rated for high altitude.

The Tung Sol 6X4 tube data page says that their regular 6X4 is only good to 10,000 feet. Since I live at sea level that would probably do fine.

Are there any particular brands or types of 6X4 that would be best in the Mini Torii, for one who wants to switch output tubes once in a while?
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Rivieraranch
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Re: 6 WHY 6? R.I.P. 6X4
Reply #6 - 07/31/10 at 03:40:23
 
After reflecting further on the whole episode, I am convinced that the 6Y6 tubes were very frisky. One of them was either arcing slightly or just presenting the rectifier with more current than it could handle. As a result of this I am stocking up on regular 6x4 variants and also am securing an adapter to use the 6CA4/EZ81 rectifier in place of the 6X4. This was O.K'd. by Steve and I am anxious to try the new rectifier.
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