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Owners of Carver Crimson 275 -Caution/Warning--Potential Increased Risk of Electric Shock

What's going on?:   If you own a Carver Crimson 275 amplifier there is a real potential that your amplifier does not have a proper chassis grounding scheme inside.  There is a type of grounding system involved, but the third prong of the IEC socket (the actual electrical socket on the inside of the amplifier) is left wide open on my amplifier and and at least one other amp that I have virtually confirmed (not firsthand--only through another owner).  

What does this mean?:  If one of the hookup wires carrying power/B+ came loose from its soldered weld and touched either the chassis or something conductive to the chassis and the user then touched the chassis/unit with the power on they could get a significant electric shock. There are some seriously high voltages in this tube amp (like many amps of its topology) and the result could be lethal.

Carver Corporation's Response to Status on Grounding:  I have notified Frank Malitz of the Carver Corporation about this problem.  He responded to me in writing saying the following, exact quotation, nothing more or less:  

"the design is under review with engineering and I'll contact you tomorrow." (F. Malitz)

In the interim, users may be at an increased risk of shock and bodily harm.   I would encourage you to check with an electronics expert or the Carver Corporation for further guidance, as I'm not qualified to say more than there's no confirmed chassis ground in the unit that I have and at least one other unit.  

Finally, unless you are qualified in working with high voltages do not open your unit to check for the ground wire running to the ground prong on the IEC. Please note that doing so with or without a chassis ground should only be done by someone experienced with electronics--i.e. caps must be discharged and care taken to cause an issue.  Seek professional help. 

I'm just a music lover and hobbyist.  I'm merely relaying this information out of concern for the safety of fellow humans. I'm not an expert and perhaps an expert will rule out this identified potential increased risk as non-existent.  For now, I can say that it is my opinion that there is a real reason to believe that grounding scheme might be deficient and I will not be using my amp until this is sorted out.  

I'll report any response from the Carver Corporation as soon as I hear back.  For now, my amp will sit unplugged. 

 

128x128jbhiller
jbhiller's avatar
jbhiller OP
1,445 posts
 

Carlsbad, I would think that any tube power amplifier using power transformers, output transformers, which has 600+ volts going on in some sections must use a grounding scheme that grounds to chassis and to earth prong so that if something happens the current goes into the 3rd prong and your wall wiring and trips a breaker. 

Stuff happens. People drop amps. Wires age, And so on.  

Maybe an electrical engineer can chime in on this.  

Disclaimer:  I am not taking the position that this amplifier is a "Widowmaker" or "Widowermaker".  Could it be? Yes.  That's the sole point.

czarivey
5,946 posts
 

LOL all of Bob’s equipment doesn’t connect to safety ground, because it’s not needed and there’s no risk of electric shock.

What happens with vintage gear that has only 2 prongs for the powercords?

Gimme break dude, you’re really trippin on somethn

jea48
4,649 posts
 

@jbhiller ,

What a mess. Sell it and never look back!

Good news don’t worry about the DC power supply B+ inside the amp. On the back of the amp is a fuse for the B+.

Bad news, from what I see the AC power wiring violates electrical safety standards that have been in effect for at least the last 30 years...

The AC power fuse is connected to the neutral connection on the IEC inlet connector. That’s a no no... You don’t fuse the neutral conductor.

The Hot connection on the IEC inlet connector is connected to the on/off power switch. The guy got that right. Except he should have went to the fuse first then to the switch.

Will the AC fuse blow in the event of an overload condition? Yes... Will a blown fuse kill the HOT energized AC conductor inside the amp? NO!

IF for what ever reason, your fault my fault anybody’s fault if the fuse blew due an overload and it was caused by a short in the primary winding of the transformer and the insulation on the winding got hot enough and bared the conductor, and the bared conductor came into contact with the iron core of the transformer, the metal chassis of the amp would be energized... HOT...

 

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jbhiller's avatar
jbhiller OP
1,445 posts
 

@czarivey ,  Thank you for your courtesy.  Lovely. 

jbhiller's avatar
jbhiller OP
1,445 posts
 

@jea48,  Thank you once again.  Yes, I was wondering about that neutral hookup to the power fuse.  I built a very very simple single ended amp about 4-5 years ago and the plans came from a book.  I remember the author saying something just like you are about this being a big no. 

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