Originally posted by MWJB
View Post
Announcement
Collapse
No announcement yet.
5F1 hums, quiets down when volume at maximum
Collapse
X
-
-
"Yes, the hum dissapears when I power on without the 12AX7 preamp tube. I'm left with only the buzzing of the tubes and no change whatsoever in output level regardless of how I set the volume pot." You've lost me, with the 12AX7 pulled, you have no hum...but you still have "buzzing of the tubes"? There shouldn't be any buzzing of the tubes, either with or without the 12AX7.
Comment
-
Originally posted by MWJB View PostYou've lost me, with the 12AX7 pulled, you have no hum...but you still have "buzzing of the tubes"? There shouldn't be any buzzing of the tubes, either with or without the 12AX7.
Comment
-
Originally posted by MWJB View PostThat's not normal.
Comment
-
Originally posted by MWJB View Post"Finally, the third ground point is another solder lug attached to a PT screw and the chassis, and holds the AC cord ground wire and the PT ground wire." If bt PT geroun wire you mean the red/yel B+ centre tap, this should be grounded with the 16uf filter cap (& the 8uf filter cap for the screen supply @ junction of 10K & 22K power supply resistors).
ProGuitar - Preisliste Amps
Comment
-
Originally posted by motzu View PostThat's right - and in my layout, the red wire goes to pin 3 of the 6V6, and the blue wire is supposed to go to the cap/resistor junction. From the cap/resistor junction, there's also a wire going to pin 8 of the rectifier tube (where one of the PT's yellow wires is also connected).
Instead of wiring the blue OT wire to the cap/resistor junction, I've wired it directly to pin 8 of the rectifier tube, all the other wires connecting as specified. I don't see how this could have affected any grounding issues, but then again I might be wrong.Building a better world (one tube amp at a time)
"I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo
Comment
-
What's with the weird use of alligator clips? Why is floating right above a main ground point of the preamp?
Also, what is that green with black strip wire and where is it going? A left over piece that is used as a jumper?
Is that green/blk wire the primary hot wire to the fuse or ?
Is there a center tap for the 6v filament leads? A pair of 100 ohm virtual center tap leads?
Comment
-
Originally posted by tubeswell View PostThat is wrong - the blue OT wire is supposed to go to the 16 uF-10k resistor (B+ node) junction. Attaching it to the cathode of the 6V6 is incorrect. The OT primary needs to be connected to the B+ node
Again, just asking because I'd like to learn more, and I've assumed that what's good for Victoria is good enough for me (unless I got what they're doing wrong, but it does seem straightforward enough).
Comment
-
Originally posted by Bruce / Mission Amps View PostWhat's with the weird use of alligator clips? Why is floating right above a main ground point of the preamp?
Also, what is that green with black strip wire and where is it going? A left over piece that is used as a jumper?
Is that green/blk wire the primary hot wire to the fuse or ?
Is there a center tap for the 6v filament leads? A pair of 100 ohm virtual center tap leads?
There are no jumpers in there. The green/black wire is the 230V wire coming from the PT, and it goes to the on/off switch at the bottom of the volume pot.
Yes, I am using a pair of 100R resistors going from the heater wires (from the pilot light holder) to a solder lug held by a PT screw. You can't see that properly in the pictures, it's the top right screw and it's behind some wiring and the pilot light support.
I'm sorry, I don't understand the question about something floating above a main ground point for the preamp...
Comment
-
I think motzu is saying he put the OT onto pin 8 of the 5Y3 (as opposed to the 6V6 cathode), which should be the same thing electrically as the first filter node. I have to admit I too balked at the reference to "pin 8" initially. It's what we get for throwing around pin numbers (instead of function) and terms like "V3" (again, instead of which tube and what it does).
Comment
Comment