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hotbox Question


 
12/10/2000 7:38 AM
Morgan hotbox Question
according to the schematic at  
 
 
 
http://www.geocities.com/CollegePark/Library/1355/hotbox.jpg  
 
 
 
Does the 6.3VDC after the "Diamond" shaped rectifier go to the heaters of the tube?  
 
 
 
Thanks  
 
Morgan Miller
 
12/10/2000 3:30 PM
Eric H
email

[QUOTE]Does the 6.3VDC after the "Diamond" shaped rectifier go to the heaters of the tube?  
 
[/QUOTE]  
 
Yes.  
 
 
 
If that is rectified off a 6.3v ac tap it'll be higher that 6.3 voltsDC --you'll probably need to drop it with resistors, or, better yet, use a 6v regulator.  
 
 
 
-Eric
 
 
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12/10/2000 4:31 PM
Morgan a couple more questions
According to this schematic i need a .22 uf and .1 uf electrolytic capacitor. Where am i suspose to find these?  
 
I have seen another hotbox schematic that doesn't show these as electrolytics. Think it will work with normal ones?  
 
Then for the tube heaters do i run the 6.3VDC into the 4 and 5 pins and groung the 9 pin?  
 
 
 
Thanks
 
12/10/2000 8:09 PM
Frank Clarke
email

They don't have to be electrolytics. So, will your heaters be in parallel?
 
12/11/2000 12:12 AM
Morgan
I need to know if i am suspose to ground the number 9 pin.
 
12/11/2000 2:54 PM
Scott Swartz
email

Yes, pin 9 will be grounded, and 4 & 5 to the 6.3 VDC.  
 
 
 
For the lowest hum you will want to use correct star ground practice, ie don't ground pin 9 to the chassis at the socket. The negative wire of the filament pair should connect to the junction of the filter cap and the bridge rectifier, then run a wire from that junction to the power supply star ground.  
 
 
 
Read up on star grounding if you're not sure what I'm talking about because correct grounding is very important in a tube pedal because of the low signal voltages.  
 
 
 
You may still get a hum from the third prong of the AC power cord, which can be eliminated by transformer coupling out of the pedal. This is a better solution than using a 3 to 2 prong adapter on the AC cord, which of course defeats the safety ground.
 
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