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Old 1st August 2009, 01:27 AM   #1
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Default Tubelab SE - alternate power transformer

As some of you may have noticed, I recently acquired a toroidal power transformer that may be suitable for my Tubelab SE. The reason for it was because of buzzing problem with my existing PT (Hammond 272JX). I thought about going with Edcor that's been mentioned on this forum many times but I found this TPT at low price so I decided to give it a try. Below is the schematic.
Click the image to open in full size.

I hooked it up to my TSE today with both primaries tied together as parallel. Secondary tap 1 and 2 are tied as parallel and connected to T1-4 and T1-5. Tap 3 is connected to T1-2 and T1-3. Tap 4 is connected to T1-7 and T1-8. T1-1 and T1-6 on the board are not connected to anything.

TSE schematic is shown here for reference.

I started to go through "check out" process and at the first step, I noticed something was missing. There was no B+ or B-. They both read 0. OPT filament powers up though (5V). I stopped there and decided to bring this up here.

Obviously something isn't working. Can someone guess what that may be? It does get 345VAC at T1-4 and T1-5 tap on the board but nothing at R30 and R7. Does T1-1 have something to do with it?
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Old 1st August 2009, 01:38 AM   #2
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I sent this to your email but I will post it here so that others can read it. I have not tried the Anteks on a Tubelab SE, but I have used them on Simple SE's and other (bigger) amplifiers. I have a big Antek in mind for a big P-P amp that will use all toroidal transformers (power and OPT).

You can make the high voltage windings on an Antek transformer work. You have to connect the two windings in series so they work like a typical Hammond transformer. Connect ONE yellow wire to ONE white wire and use this for the center tap, the T1-1 connection (the red-yellow wire on a Hammond). Use the other yellow wire for T1-4 (red on a Hammond) and the other white wire for T1-5(red on a Hammond).
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Old 1st August 2009, 01:43 AM   #3
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Default Re: Tubelab SE - alternate power transformer

Quote:
Originally posted by Evenharmonics
I hooked it up to my TSE today with both primaries tied together as parallel. Secondary tap 1 and 2 are tied as parallel and connected to T1-4 and T1-5.

I started to go through "check out" process and at the first step, I noticed something was missing. There was no B+ or B-. They both read 0.

Obviously something isn't working... Does T1-1 have something to do with it?
Yes, T1-1 does have something to do with it. You don't want to tie tap 1 and 2 in parallel. You want to tie them together in series. Treat the connection between them as the center tap of the HV secondary. You do need to mind the phase of the windings. If it's an Antek, you would typically tie one white to one yellow and use that for the center tap (to T1-1). The remaining white and the the remaining yellow go to T1-4 and T1-5.
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Old 1st August 2009, 02:48 AM   #4
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Quote:
Originally posted by tubelab.com
You have to connect the two windings in series so they work like a typical Hammond transformer. Connect ONE yellow wire to ONE white wire and use this for the center tap, the T1-1 connection (the red-yellow wire on a Hammond). Use the other yellow wire for T1-4 (red on a Hammond) and the other white wire for T1-5(red on a Hammond).
Thank you.
It's working now and the voltage readings are close to my previous setup (Hammond 272JX) except there is no more buzzing PT. Hooray!!!
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Old 1st August 2009, 02:55 AM   #5
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As for Antek toroidal transformer, it is AN-3T325 but what they sell come with 12.6V 2A for tap 3 and 6.4V 4A for tap 4. I had to modify it to get 5V from tap 3. I may post "how to" on this later if there are interests. It would void the warranty but that's the risk I was willing to take to get rid of buzzing. Plus, their TPT are cheap compare to others.
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Old 1st August 2009, 03:03 AM   #6
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Quote:
Originally posted by Evenharmonics
I had to modify it to get 5V from tap 3. I may post "how to" on this later if there are interests.
You took off the tape and unwound a few turns?
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Old 1st August 2009, 03:14 AM   #7
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Yes but it was quite a bit more involving. Tap 4 is on top of tap 3 so I had to take off tap 4 layer, unwind 20 turns of tap 3 wire (total 32 turns existing). Actually, I unwound the entire tap 3 layer and rewound 12 turns but with even spacing of wire. Then I put the plastic back on and tap 4 wire back on top of that and finally outer plastic tape back on. It is time consuming work.

I'll see how this thing holds up. For those who are thinking of trying this TPT, it may be a good idea to wait a while.
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Old 1st August 2009, 12:42 PM   #8
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If you only needed 12 turns, wouldn't it have been easier to just add a new 5V winding on top of the existing?
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Old 1st August 2009, 03:18 PM   #9
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You could but I didn't have the type of wire suitable for it and wanted to see how the details are worked out at the connections. Plus, I would rather not have extra taps around. If someone wants to try that method, I sure would like to hear about the result.
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Old 2nd August 2009, 01:39 AM   #10
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Quote:
If someone wants to try that method, I sure would like to hear about the result.
I have added two more filament windings to an AN4TK400. This is a nice transformer that has two 400 volt windings with a bias tap on each at 70 volts. This makes it easy to get -100 volts, +100 volts, -500 volts and +500 volts all from the same winding. It also has a 5 volt winding but only ONE 6.3 volt winding, I need 3 so I wound two more windings through the core using ordinary 18 gauge hookup wire (Belden 9918). I simply added turns until I got enough voltage. It looks like about 14 turns each, but it could be 13 to 16.

I have been using the transformer for various tests but it has not been in continuous service. I will probably do a better job once I am sure what I really need.
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