Building a 5E5A

[J Rindt]

Starting from scratch.
Is there any reason I should not use a 5Y3 rectifier instead of a 5U4GA.?
Would it effect the rating of the mains fuse.?
Thank You.

http://www.ampwares.com/schematics/pro_5e5a.pdf

[sluckey]

A pair of 6L6s may want more current than a 5Y3 can safely supply. 6L6s usually want a beefier 5U4 or 5AR4.

[J Rindt]

Maybe I should post my REAL concern. I do not think the PT that I have will run this schematic with a 5U4. But it will supply current for a GZ34.
Thanks Sluckey.....I appreciate it

[Iannone]

Ih for 5U4GB is 3A; for 5AR4 its 1.9A.

[bluesbear]

Don't risk it. I burnt up a BF Deluxe Reverb transformer once trying a 5U4. Now I know!
Dave

[tubeswell]

spec your PT for a 3A 5V winding and you can run whatever rectifier tube you like.

[J Rindt]

spec your PT for a 3A 5V winding and you can run whatever rectifier tube you like.

Well.....it is a PT from an Ampeg B-25, and that ran a GZ34. Not sure it would take to a 5U4....I kind of doubt it has that much slack in it. I don't want to burn up my first PT just yet....

http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_B25B_.pdf

[StevieRayVehkakoski]

5V4 takes only 2 amps and to my ears it sounds closer to 5U4 than to 5AR4.

[J Rindt]

5V4 takes only 2 amps and to my ears it sounds closer to 5U4 than to 5AR4.

Thanks....I forgot about that tube,and only 2 amps is perfect. I am not a big fan of the GZ34 for some reason. Maybe because NOS tubes are so expensive compared to other rectifiers.....?
Thanks Again

[tubeswell]

spec your PT for a 3A 5V winding and you can run whatever rectifier tube you like.

Well.....it is a PT from an Ampeg B-25, and that ran a GZ34. Not sure it would take to a 5U4....I kind of doubt it has that much slack in it. I don't want to burn up my first PT just yet....

http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_B25B_.pdf

Well according to post#88 in this thread - http://www.talkbass.com/forum/f15/ampeg-svt-vr-head-requiring-least-115-volts-wall-socket-446053/index5.html - the Ampeg 300707-3 PT had a 3A 5V winding. (The 300707-1 was the US-voltage equivalent of the 300707-3, but I bet its the same rating on all the secondaries.) JM2CW - but ultimately your call. (Google is your friend)

[J Rindt]

Would that screw with the heater voltage.? To use a rectifier that draws 1.9 amps from a 3 amp tranny.? 

[tubeswell]

Would that screw with the heater voltage.? To use a rectifier that draws 1.9 amps from a 3 amp tranny.?  

No. But if the 5V winding was 2A and you tried to draw 3A from it, it would (screw it).

[J Rindt]

Would that screw with the heater voltage.? To use a rectifier that draws 1.9 amps from a 3 amp tranny.?  

No. But if the 5V winding was 2A and you tried to draw 3A from it, it would (screw it).

I should have been more clear.....just to make sure. I was thinking that maybe, if it is a 3A winding, and you only pull 1.9A from it, that there might be a smaller than "normal" voltage drop and the rectifier heater might get much higher than 5 Volts. Am I wrong about that.?
Thank You

[tubeswell]

Would that screw with the heater voltage.? To use a rectifier that draws 1.9 amps from a 3 amp tranny.?  

No. But if the 5V winding was 2A and you tried to draw 3A from it, it would (screw it).

I should have been more clear.....just to make sure. I was thinking that maybe, if it is a 3A winding, and you only pull 1.9A from it, that there might be a smaller than "normal" voltage drop and the rectifier heater might get much higher than 5 Volts. Am I wrong about that.?
Thank You

No. It will still be around 5V and it will be fine

[bluesbear]

Think of it this way: If a person can bench press 150 lbs, pushing 100 pounds would be easy. No strain; no sweat. That's exactly how a 3A winding operates with a 2A load.
Dave