using a 5R4 in a BMRI

[deluxe5D3]

I am using a 5R4 in my RI in order to drop the plate voltage low enough for me to use a pair of NOS Tungsol 5881's.. it took the plates right down to 430V which is right on the money to original 5F6-a specs. I really like the sound of it now..

The tube data sheet indicates a 4uF max filter input, but of course the RI runs 50 uF before the choke...will this be a problem? I'm thinking the 5881 plate Z is high enough for no worries.....

[Jazz P Bass]

I thought the 5R4 was good for 40uf. (old stock tube)
What rectifier was installed from Fender?
A GZ34?
Same thing.
Some tube rectifiers cannot handle charging up too high of a capacitance.
In my estimation, 50uf is fine.

[deluxe5D3]

Jazz:
It originally Came with a SS Rect. I am using a 5R4 not an 5AR4.

[pdf64]

Try a search; Enzo has answered this issue previously, he had a later edition of the RCA tube manual that gave a limiting value for 5R4XX of XXuF. Pete.

[Jazz P Bass]

5R4 Capacitance

It seems that 4uf is stated in every datasheet I looked at.
Them there is this disclaimer:
Source:Franks Electron Tube Data (Results of tube search)

[deluxe5D3]

Thanks, I did a search and found this quote from R.G.:

That's why tube rectifier data sheets list maximum values for the first filter cap. The bigger the cap, the smaller the time the rectifiers conduct at peaks of the AC wave, and the higher the current peaks must be to get enough DC in during the short conduction time. Eats the cathode coating. As I remember this, it's in the Tube Amp FAQ at GEO, since about 1994.

So it looks like it's not a good idea to run this in a BMRI, even though lot of people do... Last thing I need is for the rectifier to go, taking the PT with it.. I will go back to a 5U4

[pdf64]

See
http://music-electronics-forum.com/t1287/
'stokes' seems to be trying his best to get them to fail due to high value reservoir cap
and
https://www.kcanostubes.com/content/nos-rca-5r4gb
Pete.