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Old 24th December 2002, 01:22 PM   #11
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Ok! Enjoy your holiday..Going to San Francisco myself tomorrow on holiday!! Hurray!
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Old 24th December 2002, 09:17 PM   #12
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Hello and Merry Christmas,

Questions:

1. 6sn7, 76 tube. Connected the filament wire (6.3v 4a) wire from the power transformer to the turret board, one wire to each side. Then I took two shield wires, two 20awg leads each/w ground leads, soldered them to the turrets, running them to each tube filament, Is polarity a concern to be followed for a/c filament heaters? Also, where should the ground wire for the shields be soldered?

2. The power transformer filament tap for the 300b is 7.2v 1.5a and is to be rectified to achieve the needed 5V. 1.5a. I purchased 8 schottky barrier diodes from DigiKey, rated at 20v 16a. They are dual rectifiers. The part number is SR1602-ND http://dkc3.digikey.com/PDF/T023/V5/0491.pdf . They are in TO-220 packages. They have three leads coming out with these symbols (~ + ~). I hope I can use these and how do I hook them together to rectify the signal? I have heat sinks for them also. Iíll post a picture of the schematic from Electra Print.

Thanks again very much for any help
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Old 24th December 2002, 09:32 PM   #13
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Paul,

Quote:
Then I took two shield wires, two 20awg leads each/w ground leads, soldered them to the turrets, running them to each tube filament,
What did you use the turret tag board for?

Quote:
Then I took two shield wires, two 20awg leads each/w ground leads, soldered them to the turrets, running them to each tube filament, Is polarity a concern to be followed for a/c filament heaters? Also, where should the ground wire for the shields be soldered?
Why shielded wires?
Just twist them.Polarity doesn't matter.
If the leadouts from the transformer are too short just solder the same gauge to them so you reach the tube sockets directly.
Don't use the turrest boards for this.

Cheers,
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Old 24th December 2002, 09:42 PM   #14
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Quote:
Is polarity a concern to be followed for a/c filament heaters?
Not normally, though a switchover once the amp is completed, might make a tiny change in signal-to-noise.
Quote:
Also, where should the ground wire for the shields be soldered?
Unless directed otherwise, take them to the central earthing point. Ground only one end.
Rectifiers:
Quote:
They have three leads coming out with these symbols (~ + ~). I hope I can use these and how do I hook them together to rectify the signal?
Ah, how many did you buy?
If you bought 4, that's fine. Parallel the outer pins.
If you bought 2, it becomes more complex: One is suitable for the "top" end of the bridge, but you'll need another 2, or a different configuration of rectifer for the bottom. IMO it's better to use 4.
Heatsinking:
Your chassis is the best heatsink for miles. If there is a way of attaching them to the chassis - do it. If the tab is metal, it'll need an isolating kit. Some have plastic coated tabs; they're easiest.
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Old 24th December 2002, 09:49 PM   #15
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Default SHIELDED HEATER WIRES???

John,

Quote:
Unless directed otherwise, take them to the central earthing point. Ground only one end.
Shielded heater wires???

No,better to get them as far away as possible from anything else so don't use the turret boards for that.

IMO,you don't even need any of those turret boards anyway.

Why did I write up all these soldering instructions anyway?

Good thing it's X-mass,
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Old 24th December 2002, 09:59 PM   #16
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I agree that twisted heater wires are better, but it'll work fine either way. I'd forgotten that twisted had already been recommended and was just answering the current question.
Either way, keep the heater wiring away from everything else.
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Old 24th December 2002, 10:05 PM   #17
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Hi,

This starts to look like "Sleeples in Europe" errr Seatle.

Hmmm...feel like talking OTL in the OTL thread but I think I got my wires crossed....

Cheers,


P.S.What's on the menu?
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Old 24th December 2002, 10:11 PM   #18
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Quote:
P.S.What's on the menu?
I'm at work.
No food of interest.
A colleague brought in some Belgian beer.
I've just finished a Malheur (10%), she's just had a La Trappe (8%). Lucky we've got no more.
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Old 25th December 2002, 12:20 AM   #19
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Hi Frank,

Thank you for help, now and in the future. I am not trying to be difficult ,please remember I am new here and I am learning as fast as I can. Here is a labeled pic of what I did. There are two 20awg twisted wires in each shield. The shield is teflon wrapped, ground wire soldered on one end of each shield. If you really think the turret is a bad idea, would you please explain why? I will change if needed, nothing is in stone.


Hi dhaen,

I have eight diodes, would it be possible to see a diagram of how the connections should be made?

~ + ~-------) to choke
| |
~ + ~-------) to ground

Really guessing here, I am not an electronics wizard, I am new here and to DIY electronics.
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Old 25th December 2002, 08:25 PM   #20
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Default TURRET TAGS.

Hi,

Quote:
If you really think the turret is a bad idea, would you please explain why? I will change if needed, nothing is in stone.
No,I don't have anything against turret tags or strips as such,quite to the contrary.

My word of caution was that it is better not to use these for heater wire supports as you effectivelily lift the wiring away from the chassis.
Secondly there is also the risk of radiation of the heater wires into
other components you may have to solder in close proximity of them.
(hum pick-up).
Also there is no need to go overboard by shielding the twisted pair of heater wires as you do IMO.
I never tried it as I never felt the need for that arrangement,simply carefully laying them out won't cause any hum.
But,you have the benefit of the doubt,if it works well then why not?

If I were to use shielded twisted pairs as you do I would not ground the shield at on of the heater wires (the shiled now carries AC as well) but just ground the shield to chassis ground at the tube side.

Cheers,
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