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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 18 Jan 2017, 19:39 
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Joined: 14 Jun 2012, 23:41
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Hi All,

In my quest to find a good, cheap output transformer for SE, I got 2 of these Indel units from TME in Poland. They look great, but I'm puzzled on how to hook them up. The top pair of terminals appear to be the 8 ohm outputs, but the bottom 3 terminals are odd. The left one is stubby, without a solder tab, and has a different colored wire. The other 2 have the same colored wire with solder tabs that you can thread a wire through. So is the odd one a primary terminal or is it the UL tap? OR is the center terminal the UL tap?

http://www.tme.eu/gb/details/tgl5_001/transformers-with-fastening/indel/tgl-5001/

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Last edited by vvelt on 18 Jan 2017, 20:16, edited 1 time in total.

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PostPosted: 18 Jan 2017, 19:57 
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If you measure the resistances across the three taps you should be able to figure out which is the UL tap. It may also be a ground so check for continuity to the frame.

Let us know how you make out.

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PostPosted: 19 Jan 2017, 06:08 
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If resistance measurement would yield only close to zero Ohm You can do the following:
Apply a low AC signal to the supposed 8 Ohm outputs (A sinus-generator at 1000Hz or a few volts of 50Hz) and measure the voltages between the 3 unknown terminals.
As far as i know the UL branch should be round 40% of the primary winding.


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PostPosted: 19 Jan 2017, 07:16 
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I test using the above method, but attaching a 6.3V filament transformer to the primary and using a DMM. Zpri= (Vhi/Vlo)^2 * 8 ohms

Even with low voltages, with high ratios, doing it step-up can give you quite a "Bazinga!" :hot:

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PostPosted: 19 Jan 2017, 08:03 
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lol

A few means 2V max...


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PostPosted: 19 Jan 2017, 09:29 
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I would think the numbers after the impedances reflect the associated terminal numbers.
5.2kΩ 5-2 primary is terminals 5 and 2. Secondary 8Ω 10-12 is terminals 10 and 12.
As terminal 7 has no exposed solder tab, I guess it is not meant to be used.


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PostPosted: 19 Jan 2017, 12:56 
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Wow, thanks for all your suggestions, this helps a lot. I'll try these things out tonight and report back. BTW, these transformers were very inexpensive and air shipping to Connecticut, USA was only $9.90. I ordered them on Monday and got them yesterday (Weds).


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PostPosted: 19 Jan 2017, 20:51 
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Ok, so Chris's suggestion was correct, and the top connections are the primaries while the bottom 2 are the secondaries, which is not what I assumed. Good thing I didn't wire them incorrectly last night!

I Googled around and found the link below that verifies pins 2 & 5 across the top are the primaries. The odd pin, #7 on the bottom left appears to be a tap point. Per Gio's suggestion, I measured 30.6 ohms across the top 2 pins and 17.4 ohms from pin 2 to 7, and 13.6 ohms from pin 5 to 7. Pins 10 & 12 across the bottom measured just .4 ohms. You could wrap a wire around pin 7 and solder it, but there is no tab hole to make it easy, so this doesn't appear to be intended for UL.

Link to data:
http://www.ges.cz/en/output-transformer-otr-5w-1-GES08202220.html

Attachment:
otr-5w-1p.jpg

I wired them up to my 6bm8 prototype assuming that pin 2 would be B+ while pin 10 would be the 8 ohm positive connection. Wrong again, I got some puffing, futzing sounds. Swapping the primaries fixed that, so the top 2 pins and bottom pins line up vertically in terms of phasing.

I'm still making adjustments to my 6bm8 project and will post later about it on the Vacumm Tube forum. However, my initial impressions are very good about these transformers. They have plenty of good bass!

Attachment:
prototype.jpg


Thanks again to all who responded, really appreciate your help!


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PostPosted: 23 Jan 2017, 09:52 
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Another thought on the odd pin on these transformers, this may be a tie point used to join 2 halves of the primary winding. See post by Tubelab on another forum: http://www.diyaudio.com/forums/tubes-valves/76541-cathode-other-types-feedback-2.html#post880240.


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