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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. 

 

jbhiller
jea48
4,788 posts
 
mrdecibel
2,549 posts

So, the 3rd prong on the ac connector is not grounded ( Crimson 275 ) ? Can someone, with the technical knowledge, explain how this is different to the hot wired 2 prong wire / plug we used to have on older components, before the iec inlet and the power cables war ? I was told by an electrician, the 3rd prong was developed as a 2ndary ground. I do not know.......

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.

.

jbhiller's avatar
jbhiller OP
1,446 posts
 

@jea48 ,  I wish you were in my town and I could take a class from you. Thank you. 

It seems we may be seeing an update from Carver Corp. on this soon per Jim Clark.  However, @jea48 , if Carver Corp.'s offer is to chassis ground the scheme would you say that is not enough?  Specifically, they must remove the neutral to fuse connection too?  That would be my understanding.  

Still no response from Frank Malik.  

I would think that knowing they have a loose bolt rolling around in an amp with a loose power transformer (the one ASR bought), they would want to issue a statement sooner than later.  They have now been alerted (they have actual knowledge) that there's a grounding scheme problem that could result in serious injury/death.  

All this raises the question:  Wouldn't Wyred4Sound see the wonky design issues that relate to grounding, securing the meter and the DC restorer circuit PCB, etc., when they build these things? I'm not trying to be critical.  I'm just thinking if Jea48 and others can see this so simply, would W4Sound?  Something is off here. 

And we wait....

jea48
4,788 posts
 

@jbhiller

Why is the schematic wiring diagram for the AC mains connection to the switch and fuse connection to the power transformer in the manual different than the unit shown in the photos of the amp in your thread? Also note the schematic wiring digram in the manual shows a switch to change from 120V AC mains to 240V AC mains.

Was the amp also sold as kit?

 

aberyclark
1,410 posts
 

Dumb question. 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. Just curious.

atmasphere's avatar
atmasphere
12,168 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.

 

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