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The BA-3 as preamp build guide
The BA-3 as preamp build guide
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Old 28th May 2019, 07:10 PM   #1441
nanchangbob is offline nanchangbob  United States
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I was just looking at 6L6's build and I noticed the MOSFETs are turned around, I know on some MOSFETS the drain and source can be reversed but I'm guessing it can not on these?

Does anyone have a part number for those heatsinks?
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Old 28th May 2019, 07:20 PM   #1442
nanchangbob is offline nanchangbob  United States
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I looked at the datasheet and I see the problem
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Old 28th May 2019, 08:50 PM   #1443
Zen Mod is online now Zen Mod  Serbia
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The BA-3 as preamp build guide
good

just wanted to say that I'm better seeing details on your avatar than on pic you posted

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Old 11th June 2019, 04:31 AM   #1444
budwiser is offline budwiser  United States
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Uhg, do I have a problem. Hooked up across R11, R10 and R12 as instructed. After turning pots, only R11 is showing any activity. Got to .25 volts on R11 and still no activity across R10. R12 has stayed at zero. Am I doing something wrong.. afraid to go any higher. Should R10 increase proportionately to R11 as I turn P1.
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Old 11th June 2019, 05:49 AM   #1445
Hikari1 is online now Hikari1  United States
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R10 and R11 is your bias.

What you are referring to as R12 is your DC offset. But you do not measure ACROSS R12. You measure after R12 and ground. Plus probe of your meter on output leg of R12 or input leg of C3 and negative meter on ground...you can use the ground pad of the PCB.

I'd start with the pots back at zero and start the biasing procedure over again. Because you are not measuring the DC offset you don't know what's going on yet.

Don't be afraid to turn the pots until you get a reading across R10/11. But try to null the dc offset as you go...it's kind of a back and forth game with the pots. The mosfets won't turn on until they reach a specific voltage so sometimes you need to turn a pot a lot until a reading shows up on R10/11.
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Old 12th June 2019, 01:32 PM   #1446
budwiser is offline budwiser  United States
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Worked like a charm. Thanks



Quote:
Originally Posted by Hikari1 View Post
R10 and R11 is your bias.

What you are referring to as R12 is your DC offset. But you do not measure ACROSS R12. You measure after R12 and ground. Plus probe of your meter on output leg of R12 or input leg of C3 and negative meter on ground...you can use the ground pad of the PCB.

I'd start with the pots back at zero and start the biasing procedure over again. Because you are not measuring the DC offset you don't know what's going on yet.

Don't be afraid to turn the pots until you get a reading across R10/11. But try to null the dc offset as you go...it's kind of a back and forth game with the pots. The mosfets won't turn on until they reach a specific voltage so sometimes you need to turn a pot a lot until a reading shows up on R10/11.
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Old 17th June 2019, 01:54 AM   #1447
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Okay, I have the boards for BA3-FE and power supply stuffed. Now to figure out how to wire up everything!

Before I solder any wires, I'd appreciate some confirmation that I'm headed in the right direction (or some course correction, if needed) with hooking up the IEC, switch, chassis ground, transformer, and PS board. I'm basically trying to mimic 6L6's build guide, and did my best to decipher how everything connects from his photos... but I'm still unclear on a few things. See attached pic. I tried to draw the wiring as I understand it.

Points of confusion:
1. Should I remove the (what I think is a) jumper plate that connects the fuse box to the IEC? If so, how should the two remaining pins be wired?

2. For wiring the secondaries to the regulator board: does it matter which color wire goes in which of the two AC in holes, so long as the secondaries are paired together (green/blue)?

3. For this dual/bipolar regulator board from Glassware, there's the option to run it in a dual configuration by leaving the two v+/v- sides separate, or in a bipolar configuration by adding jumper wires to connect the two sides. For the BA3-FE, I'm assuming I want to leave it in the dual configuration, right? (I can post a better picture of the board sans wires if that would help. Here's a link to the schematic.

BA-3 Power Wiring.jpg
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Old 17th June 2019, 10:10 AM   #1448
Attila I is offline Attila I  Germany
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@spryor
3. the ba3 fe needs a bipolar psu - optional two for stereo - so jumper!
1. leave the mains fuse in function for safety reasons!!!
2. you might want to check the phase of the primary/secondary windings
(in series configuration - like in ct - the voltages either null or sum up)

have fun
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Old 17th June 2019, 01:39 PM   #1449
McQuaide is offline McQuaide  United States
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The secondaries look right, each one has two wires coming out next to each other.
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Old 17th June 2019, 01:59 PM   #1450
6L6 is offline 6L6  United States
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The BA-3 as preamp build guide
1) Please explain why you are interested in removing that plate.

2) Correct, it doesn't matter as long as you have the secondary wires paired properly.

3) Install J1 and J2 to make the PSU bipolar. The center near the jumpers becomes ground, and V+/V- comes from the outside of the PCB. See photo from different project, but it's wired identically -

Click the image to open in full size.
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