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RE: arver Sunfire Super Junior subwoofer. In attempting repair, I found Q12 shorted, gate to source(not to drain!), and F1 open. After replacing with exact cmpnts, operation returned to normal, however, when level cntrl was turned down after several minutes of testing, failure recurred(same cmpnts.), BUT this time R110 "smoked" beyound visible identification! Need to know it's value, and anything else I may have "overlooked" (Curious, everything seemed great for awhile after my initial attempt!)

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  • Larry Landos Nov 13, 2009

    Aforementioned resistor isn't in the line to Q12(MOSFET that shorted,type IRF640), but in the line to (lge.)output MOSFET,Q11(one of two), connecting drain of it to "common",of pwr supply(+&-163VDC). I really need an "expert" with the schematic diagram/pts. list to this(no doubt, highly"proprietary"(Carver)design)!The resistor in question appears to be a 1 watt, carbon-film type(hence the dramatic "flame-out"(why f.p. metal-film type wasn't used beats me!),and I assume with the high currents involved with a 1200watt(4 ohm woofer) it's value is less than an ohm. Additionally transistors Q13&14 in the gate circuit of failed Q12(and Q10, gates and drains of the two being tied together)check o.k.(so what is causing gate-source breakdown of(only)Q12 to be exceeded(intermittently)???

  • Larry Landos Nov 14, 2009

    Sorry, I don't think I supplied enough information; this Carver design is not the old-fashioned class-AB linear- type, but a class-D high-efficiency switching- type.

    I mistakingly mis-identified the resistor in question; it's R107,not R110! Of course, being carbon(not metal)-film type, it's burned and black, after failure measuring approx. 390 ohms. and then about 560 ohms after I cleaned all the"soot" off it and adjacent circuit board with methanol(more carbon mat'l. having obviously been removed). It must be rather low, originally, probably less than an ohm, phyisical size indicating 1-watt type. Being tied between the drain of one of the two large output- Mosfets and pwr- supply common, it obviously carries full spkr load current(spkr, by the way, must be 4 ohm, measuring around 3 ohms DC, with huge 25 pound magnet!). B-plus rails are plus and minus 163VDC.

    The smaller Mosfet that fails is paired with another(there are two pairs of these total, and they may be being used to modulate the B- voltage rails for increased efficiency), in a "switching-mode" fashion? Again, failure was not immediate, but after testing unit awhile with audio generator, 20 to 100Hz. Spec sheet of the IRF640 Mosfet(200V/18A) indicates max gate- to- source voltage to be plus and minus 20 volts(operating at 2 to 4 volts). I wonder if adding zener -protection would help? But I don't think trying to circumvent whatever the problem is in a sophisticated design as this is the proper course, though! These two pairs of Mosfets have a small smd-type NPN and a PNP transistor in their gate circuits, but disconnecting and measuring them indicates they are o.k. Interestingly, measuring gate-to- source of one pair of the IRF640 Mosfets with mm in "diode-check" mode indicated 0.7 volt (what zeners normally measure), while the pair with the one that failed was 1.07 volt (that's why I disconnected the small PNP and NPN's and measured them, but all four were o.k.)---

    I REALLY NEED A SCHEMATIC AND PARTS LIST WITH VALUES; CAN THE PRECEEDING INFORMATION BE SAVED AND FORWARDED TO ANY OTHER "EXPERTS" THAT ARE FAMILIAR WITH BOB CARVER'S UNIQUELY DESIGNED SUBWOOFERS???

  • Larry Landos Nov 15, 2009

    just see my previous postings!

  • Larry Landos Nov 17, 2009

    Guess no one out there's repaired one of these?

  • Larry Landos Nov 17, 2009

    Hi!-As I mentioned in an additional "pblm" post (which FIXYA apparently won't submit until first one is resolved), I mistakenly identified the location-number of the resistor in question- it's R107, not R110! (R110 is a smd-type,1/16watt, marked"202".i.e.,2k-ohm, not 22k!) Is your reference mat'l. for the correct Carver model?(SUNFIRE JUNIOR) As I mentioned before, R107 is a 1-watt carbon film type, which I believe is very low ohmage, judging by it's location in the circuit(connected between drain of large output Mosfet Q11 and power-supply"common",i.e.,junction of (plus and minus) filter caps C65 and C76). I observed the woofer- cone excurse to extreme outward- position at moment of failure(of Q12), indicating very large DC current which took out the resistor! Interestingly, outputs Q11 and Q7 are OK(not shorted), only Q12(re)shorted-any ideas what causes this? Also(perhaps a mistake) I noted fuses F1 and F2 were marked"T4A", which I thought indicated time-lag types, while markings on the board were only"4A/250V"; having replaced them with actual time-lag types, I wonder if this is why R107"smoked" when circuit re-failed(additional time for the large current to do it)? As I said before, SMD's Q13 and Q14 in the gate-

    circuit of Q12 check OK, so what could be causing gate- to- source breakdown voltage(spec:plus/minus20volts for IRF640) to be exceeded?(F1 is connected to drain of Q12). And the unit appeared to be working and sounding fine before re- failure. Where did you get the (supposed) value of SMD R110? A schematic and parts list would be greatly appreciated if you have access(I doubt going to Carver would be of any use, as these high-end "audiophile" companies generally limit servicing of their products to themselves; since the company I work for retailed this unit(which is now well out-of-warr) to my customer, I am trying to save him the time and expense of sending it to Carver!) Any more helpful ideas/suggestions would be great; otherwise, I'll have to give up on my"trial" membership with FIXYA and try to resolve this on my own-thanks!

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R107 is 1.2K. I have similar problem, if you do find a schematic, let me know. Thanks.

Posted on Jan 05, 2010

Testimonial: "Thanks, but I already got that value from Rita(Carver repair shop in WA)Found pblm on my own!etvservice@yahoo.com"

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Is that resistor in the line to q12 ? if so it should be in the spec sheet for that device. if you don't have the spec sheet then let me know what q12 part number is.

Posted on Nov 13, 2009

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Hello,

To etvservice:

I have the same issue with R107 - smoked - in circuit reads approx 600 ohms - F1 also open. I have not had a chance to troubleshoot the Mosfets or any other circuits yet, but was wondering what you had found within your amp that was causing R107 to blow. Maybe you can provide some feedback? Also, the resistor appears to be a wire-wound style power resistor (instead of a standard carbon comp resistor).

Thanks

Posted on Jan 29, 2010

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The exact value of R110 is 22K Ohm resistor which controls the amp gain for the cabinet speaker.
check out.thanks.keep updated

Posted on Nov 17, 2009

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Have you considered sending it to Carver for repair? Maybe they can provide a schematic for you.

Posted on Nov 15, 2009

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