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Carvin V3 Problem

 
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Carvin V3 Problem
 PostPosted: Sun Jan 08, 2012 11:53 pm Reply with quote  
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  twisted99
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I just picked up a Carvin v3 and was really digging the tone. After playing for a couple of hours I decided to switch it to the 50watt mode. I played it for about 30 seconds when I noticed one of the tubes red plating. I stopped playing and shut off the amp immediately. I turned off the amp and put it back in 100 watt mode and checked the bias. It was 140ma across the stand by switch. I know that it is not out of spec for el34s but I turned it down to the recommended 100ma. I turned it back on and it made a loud pop and then started humming really badly. I tried different tubes but it still hummed loudly. I checked the plate resistors and they still measured 350ohm I then tried to check the plate voltage at pin 3 and got a very large arc. Next I tried to measure the heater filament voltage and it registered zero but when I touched pin 7 with my multimeter the hum almost stopped completely. Any ideas? I would hate to have to pay $350 that Carvin charges to repair these as I just got it yesterday and payed $500. I could have gotten a new one for that amount.
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re: Carvin V3 Problem
 PostPosted: Mon Jan 09, 2012 11:48 pm Reply with quote  
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  twisted99
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It ended up being the filament heater resistors. All four of them must have went when the tube blew. They were way out of spec. If anyone else ever experiences this they are 100 ohm 1/4w 1% located at r27, r28, r78 and r79. I went down to radio shack and picked up a set. They of course only had them in the bulk pack that came with 50 resistors I will never use but, I replaced them and now all is good. Emeric at Carvin did an excellent job helping me troubleshoot. If you measure them in the amp with tubes in they should read 50ohms. Mine were reading 140ohms.
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Re: re: Carvin V3 Problem
 PostPosted: Fri Jan 13, 2012 3:37 pm Reply with quote  
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  scoti65
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twisted99 wrote:
It ended up being the filament heater resistors. All four of them must have went when the tube blew. They were way out of spec. If anyone else ever experiences this they are 100 ohm 1/4w 1% located at r27, r28, r78 and r79. I went down to radio shack and picked up a set. They of course only had them in the bulk pack that came with 50 resistors I will never use but, I replaced them and now all is good. Emeric at Carvin did an excellent job helping me troubleshoot. If you measure them in the amp with tubes in they should read 50ohms. Mine were reading 140ohms.


Good to keep in mind - thanks. Emeric has helped me out as well with some concerns. If you ever notice a wire soldered to a circuit card chase in front of the channel 1 section, don't be alarmed. It's a factory repair to help eliminate some noise. I was tripping because I had sent my V3 back for some UPS damage that had happened in transit and I thought it was a shoddy repair. I took some pics and sent them to him and he explained everything. I did have a "heartbeat" type of sound when it came back from being repaired and through reading some posts on the BBS, some other players have as well. On the Eurotubes site they mention that some V3's when biased with EL34's where they should be (about 70% plate dissipation) you'll get a "motorboating" or "heartbeat" sound. I checked my bias and sure enough - 153ma across the standby switch. Reset it to the factory spec 100ma and no more issues. Apparently if you load up with 6L6's or 5881's it's not an issue. Just a problem with EL34's. No one has figured out why yet. Wink Also, I recently replaced the stock Sovteks with 12AX7EH's to include a balanced triode12AX7EH in position V5 for the phase inverter and WOW! Just in case you're in the market for the best prices on replacement tubes.... http://tubedepot.com/ Applause
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