Members Demonofthefall Posted August 27, 2007 Members Share Posted August 27, 2007 So I got a call earlier this evening from a bandmate. He told me that one of his friend tried my VH100R at our studio and that the VH100R is no longer in good shape. After a few angry minutes of swearing I got into my car and drove to our studio. 1) There was an impedance mismatch between the head and the cab. Head was at 4 ohm and cab was at 16 ohm.2) When the power is on, the 4 poweramp tubes still glow as usual 3) No matter what I do, the amp remains silent. Not a single hiss is produced when I crank the gain and volume knobs (and God knows VH100R can get loud ...)4) There are 2 fuses at the back of the amp. Power fuse and HT fuse. What could be happening ? Thx. Link to comment Share on other sites More sharing options...
Members Demonofthefall Posted August 27, 2007 Author Members Share Posted August 27, 2007 Hey I thought that the sunday night crew knew everything amp-wise ! Could it be that the HT fuse has blown ? Link to comment Share on other sites More sharing options...
Members 496dart Posted August 27, 2007 Members Share Posted August 27, 2007 fuses are ok? check the HT fuse Link to comment Share on other sites More sharing options...
Members Demonofthefall Posted August 27, 2007 Author Members Share Posted August 27, 2007 Power fuse is ok for sure.I don't have any device to check if the HT is OK but my n00b eyes are telling me it has not blown ... I'll have it checked tomorrow.I know that running a 16 ohm load on a 4 ohm amp is begging to kill the amp.Since my poweramp tubes appear to be working, I wonder if the impedance mismatch really caused the problem. Usually, what are the first components to toast in such a case ? Link to comment Share on other sites More sharing options...
Members bass_n_drums Posted August 27, 2007 Members Share Posted August 27, 2007 it might be the phase inverter......replace that. If that doesn't work. Replace a fresh set of preamp tubes. And have a set of power tubes available as welll. Link to comment Share on other sites More sharing options...
Members Demonofthefall Posted August 27, 2007 Author Members Share Posted August 27, 2007 it might be the phase inverter......replace that. If that doesn't work. Replace a fresh set of preamp tubes. And have a set of power tubes available as welll. Where is the best place to have it repaired ? Guitar Gear Store ? Some Electro-wizard-dude ?I don't feel really comfortable fixing it myself ... Link to comment Share on other sites More sharing options...
Members satannica Posted August 27, 2007 Members Share Posted August 27, 2007 Could be anything - I'd just take it to a reputable tech. I did this myself years back with my own VH100r. Luckily, needed a retube and a few badly burned resistors, that was it. Link to comment Share on other sites More sharing options...
Members Syn Harvest Posted August 27, 2007 Members Share Posted August 27, 2007 Thats why i dont let people touch my {censored} anymore if im not there. Sounds like it could be a Phase inverter. Most stores that sell amps and stuff have techs or any kind of electronic repair store should be able to figure it out Link to comment Share on other sites More sharing options...
Members bass_n_drums Posted August 27, 2007 Members Share Posted August 27, 2007 Where is the best place to have it repaired ? Guitar Gear Store ? Some Electro-wizard-dude ?I don't feel really comfortable fixing it myself ... you can do it yourself...get some 12ax7a like Tung Sol, JJ or etc and just pull out the old one and put in a new one...that's it. Link to comment Share on other sites More sharing options...
Members Demonofthefall Posted August 27, 2007 Author Members Share Posted August 27, 2007 you can do it yourself...get some 12ax7a like Tung Sol, JJ or etc and just pull out the old one and put in a new one...that's it. I'm ok with tubes replacement but I'm less comfortable with the phase inverter stuff ...Anyway, I'll check it out tonight with new fuses and preamp tubes. Thanks guys. Link to comment Share on other sites More sharing options...
Members Let It Burn... Posted August 27, 2007 Members Share Posted August 27, 2007 impedance mismatch should be no problem, I've had the same problem as you and that was when my HT fuse blew, so just replace it. Link to comment Share on other sites More sharing options...
Members Demonofthefall Posted August 27, 2007 Author Members Share Posted August 27, 2007 impedance mismatch should be no problem, I've had the same problem as you and that was when my HT fuse blew, so just replace it. I have confirmation that HT blew. Now let's hope that nothing blew before it ... Oh and how long can the amp usually run at gig volume with a 4-16 impedance mismatch before blowing the fuse ?4-16 is a huge gap ... Link to comment Share on other sites More sharing options...
Members Viesczy Posted August 27, 2007 Members Share Posted August 27, 2007 The one fuse on my VH100 blew and upon quick inspection it looked fine. I had to take it out and observe it in BRIGHT light to see that it popped-was the slow blow one, the cylindrical one (yeah I realize how technical that reads! ). I would hope your VH100 is fine, that the fuse popped before there was any damage. Such was the case with him. Derek Link to comment Share on other sites More sharing options...
Members bass_n_drums Posted August 28, 2007 Members Share Posted August 28, 2007 I'm ok with tubes replacement but I'm less comfortable with the phase inverter stuff ...Anyway, I'll check it out tonight with new fuses and preamp tubes.Thanks guys. the phase inverter is a preamp tube like the rest. It's the one nearest to the power tube. Link to comment Share on other sites More sharing options...
Members Demonofthefall Posted August 28, 2007 Author Members Share Posted August 28, 2007 the phase inverter is a preamp tube like the rest. It's the one nearest to the power tube. Thanks."Phase inverter". This felt like some scary-high-tech-Star-Trek stuff ... now why do I feel n00b/dumb/idiot/... The worst part of this story is that I was suppose to sell the Laney this week. I was thinking of replacing it by a Mark IV or a RK-II ... So I hope it'll be easily fixed ... Link to comment Share on other sites More sharing options...
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