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Old 23rd April 2019, 02:41 AM   #5531
BigE is offline BigE  Canada
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Quote:
Originally Posted by 6L6 View Post
If your PSU works and has a stable ground, you donít have your transformer attached in the manner shown on the schematic you posted in #5526.

Which leads to the question, how DO you have it attached, with the 5 secondaries...??
Just like the diagram shows. .

One V+/CT/V- secondary is not used. The 4 other secondaries are split into two groups and run in parallel. There is one full wave rectifier per channel.

The caps are strapped together on the PCB boards. They are the white teabag boards. There is a pair of boards per channel.

The ground on the right hand side of cap bank as shown on the diagram goes to the ground connected to the diode bridge/CL-60. There is one diode/CL-60 per channel.

Both of the diode/CL-60 grounds are connected to the same earth point on the chassis where the safety earth comes into the box.

I hope the drawing is OK.
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Old 23rd April 2019, 02:59 AM   #5532
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drawing is not ok to see it clearly. it is tough to see how you hooked them up.

i would feel there could be something wrong but can not indicate it.
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Old 23rd April 2019, 03:17 AM   #5533
BigE is offline BigE  Canada
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The secondaries are in parallel with the other secondaries. If they were not, fuses would be blowing.

The connection between the center tap and the zero volt line on the left of the cap bank is not made.

The ground on the right of the cap bank is connected directly to the ground on the left on the diode/CL-60. The other side of the diode/CL-60 is connected to earth.

This shows only secondary side and ground.
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File Type: jpg Power supply schematic.jpg (46.2 KB, 71 views)

Last edited by BigE; 23rd April 2019 at 03:25 AM.
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Old 23rd April 2019, 03:18 AM   #5534
6L6 is offline 6L6  United States
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F5 Turbo Builders Thread
Photos please
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Old 23rd April 2019, 03:35 AM   #5535
BigE is offline BigE  Canada
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does the re-drawing help? The build is a mess.... The first photo shows a terminal strip. With secondaries attached. The unused ones have heatshrink wrapped ends. The flying caps/resistors are snubbers.

One pair of red/white goes to a cap bank for each channel. The second is a closeup of one of the cap banks. You can clearly see that red and grey are +/-. No CT connection on the diode bridge side.

There are a lot of relays around the boards. The notion was that in the event of a short cycle while powering up, a relay would disconnect the diode bridge from the cap bank, to enable the thermistors to cool.

But this is not about the relays. This is about parallel secondaries of a CT transformer, still supplying the correct voltage, even though the CT is disconnected.

The secondaries are 2xV apart. The zero volt line is connected at the signal ground only. That gives the center voltage reference. Then V+ is V above signal ground ,and V- is V below. The signal ground is 10R above earth due to the CL-60.

So there is a center reference.
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File Type: jpg small secondary.jpg (220.7 KB, 68 views)
File Type: jpg small cap bank.jpg (204.2 KB, 68 views)

Last edited by BigE; 23rd April 2019 at 03:44 AM.
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Old 23rd April 2019, 04:35 AM   #5536
BigE is offline BigE  Canada
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Well, I decided to trust my meters, and the new channel biased up BEAUTIFULLY. Unfortunately, noisy.... 1.25mV ( channel with meters attached ) and 0.775 mV rms, according to the entry level Digital scope.

Now, onto grounding schemes....

Although I may have little luck with two channels and multiple secondaries in one box.

Also, this is with the output boards wired in parallel, which will certainly increase loop area.

Thanks for all the help!

I've got to go learn a bunch of stuff now.

Last edited by BigE; 23rd April 2019 at 05:03 AM.
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Old 23rd April 2019, 02:55 PM   #5537
BigE is offline BigE  Canada
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RE: grounding the center tap.

I found this online. EEVBlog entry

This mainly depends on the transformer and only after that comes if you like supplies with grounded outputs. If you let it float the transformer needs to be rated for use in class II appliances (double / reinforced insulation). You'll find that information sometimes on the nameplate of the transformer or you can see that it's a doubly insulated transformer (separate coil chambers, insulation to core etc.). If unsure, ground it.

Last edited by BigE; 23rd April 2019 at 03:24 PM.
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Old 23rd April 2019, 03:27 PM   #5538
BigE is offline BigE  Canada
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Quote:
Originally Posted by Bfpca View Post
If you are looking for more matches to the ones you got from me then I have more that are close to the same VGS values.
Thanks! Maybe next payday...
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