It would be nice to compare this 275 unit with an early model hand-built by Bob himself. I can't imagine he would glue that PCB to the chassis. Additionally, Bob started to use a proper earth ground when he added IEC's to his amps.
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.
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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. The 3 pin IEC power inlet connector on the Carver amp falsely leads the consumer to believe the chassis is grounded when plugged into grounded wall outlet. |
A neutral is only a neutral when it is electrically connected to the electrical service grounded conductor neutral bar, in the electrical panel. Open the neutral up stream on a load connected to a live HOT conductor and the lead, wiring, from load is HOT. At that point it’s no longer a neutral. It is a HOT conductor and can be lethal. Never fuse a neutral conductor. Just because it was done in audio equipment over 35 to 40 years ago is no excuse... . |
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Here are just a few examples. https://robrobinette.com/Widowmakers.htm You had a 50/50 chance of plugging the radio into the wall outlet with the chassis grounded conductor plugged in the wall outlet grounded neutral conductor. In the radios defense the chassis was installed in a wood or plastic case. Plastic or wood knobs with an insulated back cover. . |
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