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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 3rd September 2017, 03:42 PM   #11
colnago55 is offline colnago55  United States
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Looking at one of the James sites, it seems that the power transformers can be ordered as either 110 or 220. It doesn't look to me like it is dual voltage.
http://www.jyaudio.cn/james_new.htm

Check out the foot note under the power transformer list.
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Old 4th September 2017, 08:17 AM   #12
canersahin is offline canersahin  Turkey
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Quote:
Originally Posted by colnago55 View Post
Looking at one of the James sites, it seems that the power transformers can be ordered as either 110 or 220. It doesn't look to me like it is dual voltage.
JAMES

Check out the foot note under the power transformer list.
I just got confirmation from the factory which says:

"The JS-9612-2 of yours is PRI:0-110V x2
So., this power of primary can be used in AC:110V (parallel connection) or in AC :220V (series connection).
It cannot be used in AC 115V."

So it can be used either 110 or 220.

Well I am going to try the PT when I get there and see what ratings I have
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Old 4th September 2017, 08:22 AM   #13
canersahin is offline canersahin  Turkey
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Originally Posted by w5jag View Post
It may be a little higher or lower than 120v. I've seen mine as high as 126, and it usually runs about 122.

The voltages out of the transformer will be slightly higher when 120 ish is applied to the 110 primary. It probably won't be a problem on the high voltage secondary, but it may push your filament voltage up close to 7 volts.

You'll just have to take some measurements when you get here and see where you're at. Might want to leave room on / in your chassis for a small filament transformer to buck the line voltage if it looks like the voltages out of your transformer are too high, or just use a separate filament transformer made for 120 volt primary.

Much less expensive than buying as new PT!

Win W5JAG
Do you know any reliable brand that produces "filament transformer"? If needed, what should i be checking?
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Old 5th September 2017, 03:28 PM   #14
w5jag is online now w5jag  United States
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A "filament transformer" is just a generic phrase for a small transformer designed for, or used for, powering filaments ( heaters ) of vacuum tubes.

Common secondary voltages are 2.5, 5.0, 6.3, 7.5, 10, 12.6, etc., with or without a center tap on the secondary.

Common manufacturers would be Edcor, Hammond, Stancor, Thordarson, Triad, United Transformer ( UTC ), and probably many others.

If you do a search for the phrase "bucking transformer", it will explain how to use a small transformer to reduce the line voltage going into the primary of another power transformer.

Hope this helps.

Win W5JAG

Last edited by w5jag; 5th September 2017 at 03:45 PM.
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Old 5th September 2017, 04:03 PM   #15
canersahin is offline canersahin  Turkey
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Originally Posted by w5jag View Post

Hope this helps.

Win W5JAG
Thank you so much. That is an excellent idea
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Old 5th September 2017, 05:13 PM   #16
nigelwright7557 is offline nigelwright7557  United Kingdom
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Valve power transformers can be quite expensive.
What I do is buy two cheap low voltage transformers.
The first transformer drops down mains to 12vac or 6vac for the heaters.
The second transformer (18v) is wired backwards to first transformer to give the HT.
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Old 5th September 2017, 05:30 PM   #17
w5jag is online now w5jag  United States
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Which Tubelab amp are you building, TSE or SSE?

Win W5JAG
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Old 5th September 2017, 05:39 PM   #18
canersahin is offline canersahin  Turkey
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I am going to build TSE
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Old 5th September 2017, 06:29 PM   #19
w5jag is online now w5jag  United States
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Okay.

That looks like a nice PT you have from James. Are you using their OPT's, also?

For what it's worth, here's how I see this:

Using your 110 volt transformer on a 120 volt line, will result in higher than specified secondary voltages from your existing transformer. How much higher, no one can say, because it depends on the tolerance of your transformer, and the exact line voltage, but you are probably going to see in the ballpark of an 8 - 10 % increase.

There are six voltages in the TSE: B+ for the power tubes; B+ for the 5842 driver tubes; B - for the negative rail for the MOSFET follower and fixed bias; heater voltage for the power tubes, heater voltage for the driver tubes, and heater voltage for the rectifier tube.

More B+ to the power tubes probably won't be a problem.

More B+ to the driver tubes might be, as they need to be adjusted to a particular value, but you can adjust some resistances on the board to accommodate this, so shouldn't be a big deal.

More B- might or might not be issue. Some, not all, folks have trouble with heat in this part of the circuit, and more voltage will be more heat. This probably won't be an issue, but if it is, some resistances can probably be adjusted on the board, so, again, shouldn't be a big deal.

Heater voltage for the power tubes is controlled by an on board regulator, so, as long as you have adequate heatsink, should not be a problem.

Heater voltage for the driver tubes is set by an onboard resistor, so this can be adjusted - not a big deal.

Heater voltage for the rectifier tube will probably be slightly too high, and may reduce the life of that tube. I probably wouldn't put a genuine Mullard in that socket, but if you have to replace a $20 Sovtek every couple of years, who cares. I wouldn't worry about it.

It looks like you will also have an unused 6.3 volt secondary on your PT, so I don't see why you couldn't use that for a buck. A 6.3 volt reduction in your line voltage will be good enough, I think.

So, I wouldn't worry much about it right now - several ways to solve this small issue, all of them inexpensive.

Hope this helps.

Win W5JAG
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Old 5th September 2017, 06:40 PM   #20
zman01 is offline zman01  Bangladesh
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Originally Posted by canersahin View Post
I am going to build TSE
Do you have all the parts?
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