2. amps-preamps
  3. 174304-18279

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 3 responses by atmasphere

atmasphere's avatar
atmasphere
11,640 posts
 

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.

@erik_squires Tube amp or not, if the power switch were to be damaged (such as in shipment) and shorted to the chassis, if wired correctly the main power fuse would blow the instant the unit were plugged into the wall.

atmasphere's avatar
atmasphere
11,640 posts
 

I would be willing to bet you do not fuse the AC mains neutral conductor in your equipment.

The correct way is Hot from the IEC inlet connector to >> fuse to >> switch... Fuse as soon as possible inside the equipment.

@jea48 You are correct.

Do modern HI-Fi companies get UL certification (or similar) for their designs? If so, wouldn’t the grounding issue be a part of such certification? I don’t even know if UL is even a thing anymore.

@aberyclark  UL is not required for sales in the US. Overseas it isn't a thing. In the EU, the equipment must bear the CE mark which shares many of the same requirements needed to meet UL approval. UL isn't required, but if you don't have it things can go south bad if there is a lawsuit. If you meet CE though its no worries.

 

atmasphere's avatar
atmasphere
11,640 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.

All it takes is the switch shorted to chassis and you can have a problem. That could happen easily in shipping. OTOH If the wiring is set up properly, if the product is plugged in with a shorted switch and turned on it will simply blow the fuse. As best I can make out that is not the case here.

More to discover