2000s

[ray]

Hope someone can help.. Why does my recently acquired 2000s have 2 blank, capped spots for the 2 tube postions to the left of the 4 RCA 6550's? Also, are these the best tubes to use? They all measure 80 or better on the tester. Thanks for the help. (I can do demolition work with this thing!!)

[Ryan Phelps]

Ray;
The early 2000S amps utilized two 5AR4 (GZ34) rectifiers to supply enough DC current to the power supply. This was to prevent "sag"....prized by guitarists for the natural compression it gives (such as in the tweed Fender Bassman amps), but undesirable when you want low end thump from your bass! So they used two rectifier tubes in the Sunn 2000S to prevent sag. I believe that these were replaced by diodes in later years, hence the two cover plates where the chassis was punched for the tube sockets. The diodes are far cheaper and more reliable than tube rectifiers.
RCA 6550s are great tubes. Have the amp checked for even current draw at all four output tubes for best tone.

Good Luck!
Ryan

[ray]

Thanks for the quick response. I have one other question.. I have two RCA 6550's that have a bulbous top and then the two on the left are perfectly cylindrical RCA 6550's. Is this the best way to go?

Thanks again.

[devon8]

I think I can help you.  I have a 2000s with the same capped spots.  Those were for the 2 GZ34 rectifier tubes.  Your head is like mine as it has a diode bridge instead of the tubes.  I have been trying to get a schematic on this amp that shows the diode circuit to no avail.  My power transformer fried and I need to repair.  Also, the 6550 tubes are what I have and they work good. Can you blow out a lit book of matches by holding them at the folded horn?  Talk about air movement.  Hope I helped.  

On 2001-04-02 19:59, ray wrote:
Hope someone can help.. Why does my recently acquired 2000s have 2 blank, capped spots for the 2 tube postions to the left of the 4 RCA 6550's? Also, are these the best tubes to use? They all measure 80 or better on the tester. Thanks for the help. (I can do demolition work with this thing!!)