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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
 

As an aside, my amp does not have the film capacitor and resistor linked to the speaker output terminals. Bizarre. 

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jbhiller's avatar
jbhiller OP
1,445 posts
 

@carlsbad, I would ask you to re-read my post. I talk about an "increased risk". I cannot quantify it, but I would agree that a good strong weld should not come loose. But they can and do come loose. While it may not be probable, it is entirely possible.

Not to mention, Carlsbad, there are questionable things going on in the amp. I actually did have the line running to the meter come lose and I re-worked and resoldered that. In my amp, some of the welds (not many) could have been better so I touched them up.

The other thing to note is that the DC Restorer circuit and its PCB are mounted vertically and some of it appears to be glued into place as opposed to being bolted or connected with a standoff. If that glue were to come loose due to heat, age, etc., that vertically mounted board carrying many hundreds of volts of power (per Carver’s own schematic available on their forums) could touch the chassis or other component parts. The hookup wires holding power have bare leads exposed before they attach to the solder welds.

So I don’t think I’m exaggerating the risk. I say numerous times its a potential increased risk.

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

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