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

Showing 5 responses by erik_squires

We are reaching peak conspiracy theory here. Might as well chalk up the entire 3 prong outlet requirements to the copper industry desire to sell more wiring or the need for the CIA to alter your brain waves.

GFCI is a suitable replacement for two prong outlets without a grounded wire.

 

This is absolutely true per the NEC, but the assumption made is that the incoming AC would come into contact with the chassis and trip in time. I’m not sure if this would prevent electrocution if a high voltage DC supply with lots of potential energy in the rectifier caps were to come into contact with the chassis. Lots of things could come into play here and even if the GFCI DID trip those caps may be several seconds away from fully discharging through someone’s heart or through the ground on the interconnect cables.

Seriously though, not grounding the chassis of a high voltage component is hobbyist level BS.

This sounds like a hot mess.

If the gear is in fact double insulated (which I'm not sure applies JUST to the power supply) then why use a 3 prong IEC connector?  Use a 2 prong like other gear which is double insulated uses.

And ... why oh why would you connect the chassis ground to signal ground directly?

Being a tube power amplifier we have lots of high voltage wiring besides the power supply.  In case of a high voltage short to the chassis that high voltage and current gets carried by the delicate ground in the interconnect wiring, which is then a fire hazard, or upstream equipment risk.

Really quite a messy set of choices.

It’s super easy to test this with a multi-meter you know. :)

Unplug the system from the wall, and measure resistance in Ohms from the ground prong on the AC cable to the chassis. Should be near zero.