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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
fiesta75
1,378 posts
 

Another excellent solution.

jea48
4,451 posts
 

@jbhiller 

CORRECTION:

 

jea48
3,741 posts
 
 

@jbhiller ,

What a mess. Sell it and never look back!

Good news don’t worry about the DC power supply B+ inside the amp. On the back of the amp is a fuse for the B+.

The B+ rail is not fused! 

B- is bonded, connected, directly to the chassis. IF the B+ ever came into contact with the chassis there would be a loud big bang...

The DC fuse on the back panel:

The (rear panel) vacuum tube cathode fuse
(B+) is a 1.0 ampere and should be replaced with
the same type and rating. If the fuse blows during
bench testing, it may be temporarily replaced with
a 1.25 or 1.5 ampere fuse. Do not, under any cir-
cumstances, use a "slow-blow" fuse here

Quote from owner manual.

.

jbhiller's avatar
jbhiller OP
1,430 posts
 

Hi @jea48 , can you explain the takeaway for us from this observation?  Are you saying the B- is properly handled so we do not have to worry about other means of chassis grounding? 

jbhiller's avatar
jbhiller OP
1,430 posts
 

I have asked EJ Sarmento of Wyred4Sound the following questions on the ASR thread where he chimed in: 

"Folks have raised these salient questions to which there has been utterly no response--just conclusory statements by Malitz and now Bob. Maybe you could help answer them as your firm looks to have built a good number of copies.

1. Is mounting the DC restorer circuit by gluing it vertically to the chassis part of the design?

2. Is mounting the meter to the chassis by gluing it part of the design?

3. Are the Edcor 15w OPTs part of the design?

4. What gauge hookup wire is supposed to be running from the PCB to the speaker output terminals?

5. Does the design-manufacturing process allow for substitution of Panasonic film caps with Suntan brand or other lesser known caps?

6. Have there been reports of transformer hum? I have owned two units and both hum/buzz at the transformers with no signal and volume totally attenuated (not a sound coming from the speakers, but buzz/hum coming from the transformers (all 3)?

7. Frank Malitz stated there was a problem with transformers when the vendor deviated from specification, and that resolved. Would that vendor be Edcor? What can be done to silence the transformers for those with those issues?

8. Grounding. Are you aware of what many of us view as a problem with the grounding scheme in this amplifier? Specifically, several of us have the neutral running to fuse and no chassis grounding or ground to earth. Do you believe these scheme is safe and acceptable?

This unit is supposed to have a 5 year warranty and many of us are just trying to figure out where things stand.

I'm not trying to come at anybody. I like the amp. I'm just trying to navigate through this and Frank Malitz and Bob just say: (a) the amp is awesome; (b) the amp is totally safe: (c) everyone who hears it loves it; (d) Amir and associates test it incorrectly.

I'm sure you can appreciate that when a consumer spends $3k on something they want to know they bought what was sold to them and it is safe."


 

jbhiller's avatar
jbhiller OP
1,430 posts
 

Carver Corporation Refund:

By the way, Bob Carver (by handle) chimed in on ASR offering a full refund to consumers who bought the amp if they want it, directing consumers to email info@bobcarvercorp.com

 

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