CarverFest Tube Amps~

[Anders]

Usually when there is a ground loop problem you will measure ac volts between the RCA plug and the chassis ground.
Do you still get the hum just touching the grounds of the RCA plugs to the amps ?

[TNRabbit]

Extremely small hum if touching the grounds together with a wire.  HUGE hum if touching the hot with even two entirely separate interconnects.  On the carversite, they suggested switching the leads on the output transformers on one  amp....

[Anders]

Swapping output transformer speaker wires should make no difference.
Did you try putting a ground lifter on both the power cord plugs ?

[TNRabbit]

OK, here's where I'm at:

I thought Gary swapped the power transformer already.
 
This is what Mike wants you to do:
Swap the output transformer leads on one amp.
Yes, I know that looks like 5hi7.
 

OK: tried this swap & got VERY BAD SOUNDS immediately.  Sounded like a bomb whistling/dropping, followed by a very destructive sounding bass buzz getting lower & lower.  Unplugged everything immediately.  BAD CHOICE--note to self--don't try that again!
 
Also swapped the incoming power wires with no effect.

Another observation:  The constant buzz sounds out of phase on the speakers; if I swap speaker leads it's in phase.  However, then the music is out of phase.

[TNRabbit]

Here's the output transformer swap that was suggested:

[TNRabbit]

Crap. I was attempting to reverse polarity on the main input power by use a pigtail (stupid) & had a huge fireball, big bang, & blew fuses....

Amp #3 now blows the mains fuse every time I apply power to it.

Buzz is still there on #4 when they're both plugged in. No closer than I was before, but now I have a DOA amp.

So, I sent an email to Bob C. with a link to the thread on carveraudio to see what advice he could offer:


Bob's reply:

Sent: Thursday, March 1, 2012 4:20 PM
Subject: Re: Need help with CarverFest amplifiers, Please!!
Hi Gary, wow, trouble in river city!

First thing is get some good output tubes. The Electro Harmonix are great and have a nice high voltage rating.
Then replace the DC restorer 1n4148 diodes with 1n4004 units. Replace the 15 volt zener with two 5 watt units hooked in parallel. Amp should work then. As for blowing fuses immediately, check the power supply diodes for a short. Use a simple VTVM and just measure them in-circuit. If one shows a dead short, replace it. As for the hum unit, it sounds as if the AC line is somehow connected wrong. Just inspect it careful and I'm sure you will find the problem just by looking hard with your eyeballs. Be careful, because right now I think you may have a severe shock hazard on your hands with this amp until you find the trouble.

If all else fails, send them to me. I'll fix 'em right up!

No sweat,
Bob Carver

[TNRabbit]

Here while back, Bob Farinelli told me that Bob Carver LLC was going to offer a trade-in option on the new, improved Baby Black Beauties for those who built tube amps at CarverFest 2011.  The new amps have improved power & output transformers....I guess we were the "Alpha Testers" ~

He gave me the details today:

Bob Farinelli

First thoughts

1. Must turn in your unit. As is, workie, no workie, tubes, no tubes, doesn't matter.

You must promise not to sell your new unit for at least a year.

It will be brand new and carry the 7 year warranty. (1 year on tubes)

We will reserve a block of serial #s starting with 001 through 030.

Retail price is $2100.

Price to those who turn in carver Fest units:

$999.

Bob (Carver) might shoot me over this, but you guys who sat with me and built amps are friends and family.

Spread the word. This is only available for amps turned in.

Thx

Bob