Replace Tube Rectifier With Weber CC?

[Monjul]

Someone suggested replacing a pair of 5V4 recs in a Cary amp with the Weber Copper Caps which is a solid state version of the 5V4. Has anyone tried it and if you have, how did it affect the sound and was it reliable? Thanks.

[Eli Duttman]

The Webber part is OK in a guitar amp. Do NOT use it in a HIFI unit.

I've heard tell that the now retired Dennis Had took considerable liberties with 1st filter cap. limits. Please describe your unit. Better yet, post a schematic.

[Monjul]

I don't have a schematic of my SLA 70A Signature which is a Class A design, but attached is the Class AB version of the amp which uses 5AR4 recs instead of the 5V4. The two schematics are almost identical. Thanks.

[Eli Duttman]

Do you see the 1100 μF. 1st filter cap.? That's a guarantee of trouble. A 5V4 really should be held down to 10 uF. in the 1st position. While it's true that 5AR4s are (for vacuum rectifiers) extremely tolerant of largish 1st filter caps., you can't go beserk. The 5AR4 limit is 60 μF.

Looks like Cary produced some VERY dubious designs.

[Monjul]

Thanks and yes, this was pointed out to me previously as a potential problem but another person mentioned that Cary also uses a choke to keep things stable. I don't know enough about tube electronics to really comment so I guess the question is this:

I've had a pair of Sylvania 5V4's in this amp for close to 10 years with no problem. I recently replaced them with a pair of RCA's in which one shorted after about 3 months. Should I consider the melt down of the RCA just a bad tube destined for the trash can or did I get lucky with the Sylvania's? Either way, I don't think that using Weber CC's is the answer.

[makaiyumtony]

I have a silicon version with the same socket for 5AR4 to replace, but the B+will turn higher, and sound different, even 5V4 also sound different to other direct heating tube like 5U4, depend on your personal choose, you should check amp's current still normal before to replace a new rectifier to it
tony ma

[Merlinb]

As far as I know, the copper cap is just a pair of SS diodes, a resistor (of the same value as the internal resistance of the tube) and a thermistor. I would have thought it would be an ideal substitute for an overworked 5V4.

[Captn Dave]

Originally Posted by Monjul

or did I get lucky with the Sylvania's?

Is it possible that the 1100uf cap is the one after the 500R 1W resistor and the 22uf is the first cap? That would be a rectifier friendly design.

If not: To answer your question, I suggest you download a copy of PSUII and model that power supply circuit. I think I'd look at adding a choke, changing some cap values (or perhaps just reversing their order) and keeping the 5AR4.

[Eli Duttman]

Monjul,

Without a truly accurate schematic, a certain amount of guessing is going on.

All indications are that your amp does not have a PSU choke.

Your Sylvania tubes survived by dumb luck. The "pedigree" of RCA tubes is beyond reproach.

Unless you are willing and able to make modifications to the unit, put the Weber CC rectifiers in and live with the sound you get.

If it were my amp, I'd put Chinese 5AR4s from a reliable vendor, like Jim McShane, in. I'd make the 1st filter cap. 100 μF. and add a choke of approx 1.5 H. between the 1st filter cap. and everything already in place.

BTW, another questionable item is paralleling plates from both rectifiers. The experience of John Atwood, a highly competent designer/builder, suggests that paralleling the plates of each rectifier tube and connecting each tube to only 1 end of the rectifier winding is the proper technique.

[Jim McShane]

Eli,

I don't have a better schematic, but I have looked at pics of the unit. A choke is nowhere to be found - it would be way too big to miss!