surfpup Posted February 25, 2011 Share Posted February 25, 2011 So last weekend I go into my little studio/office and flip on the Ceriatone 18 watt Marshall clone and prepare to make some joyous racket... nope... No sound, no power light, nothing. Check the A/C power - a okay. Check the other amps in the room - a okay. Check the new fuse - popped. Put in another - pop. Finally, put in a 5 amp fuse just to keep it running... hmmmmm .... crackling noise... not good... oh no, what's that burning smell? Grrrrrrr.... Smells like a transformer to me. My amp builder bud and I pop it open the next day, and everything looks and tests okay except the power transformer. Long story short a new one arrived today, and he is going to start the repair tonight. I'm hoping that was the problem (and the only problem). That is one amp I don't really want to lose! Link to comment Share on other sites More sharing options...
Dub-T-123 Posted February 25, 2011 Share Posted February 25, 2011 Bummer! Those 18 watt heads are so sweet! How much do one of those Ceriatone clones go for? Link to comment Share on other sites More sharing options...
milod Posted February 25, 2011 Share Posted February 25, 2011 AS we used to say in the olden days, better to pop the fuse than fry the amp. I always had one or two taped somewhere inside the amp body just for that potential. m Link to comment Share on other sites More sharing options...
surfpup Posted February 25, 2011 Author Share Posted February 25, 2011 Bummer! Those 18 watt heads are so sweet! How much do one of those Ceriatone clones go for? With shipping it was $724 for the chassis and tubes - assembled and ready to play. I bought my own head cabinet to put it in. AS we used to say in the olden days, better to pop the fuse than fry the amp. I always had one or two taped somewhere inside the amp body just for that potential. m Yep. I always carry spares. Of course they popped! And the question now is... was the fuse blowing because the PT was shot. Or did I blow the PT with the larger fuse because of another problem. The next few days should tell the tale... Link to comment Share on other sites More sharing options...
Californiaman Posted February 25, 2011 Share Posted February 25, 2011 Wow man... good luck with that. Hopefully it's only in need of a new power transformer. I'm going to start taping extra fuses in my amps just because I read this. Link to comment Share on other sites More sharing options...
Andy R Posted February 25, 2011 Share Posted February 25, 2011 With shipping it was $724 for the chassis and tubes - assembled and ready to play. I bought my own head cabinet to put it in. Yep. I always carry spares. Of course they popped! And the question now is... was the fuse blowing because the PT was shot. Or did I blow the PT with the larger fuse because of another problem. The next few days should tell the tale... Definitely have him check out the bias capacitors and resistors as well as rectifier diodes! Link to comment Share on other sites More sharing options...
surfpup Posted February 25, 2011 Author Share Posted February 25, 2011 Definitely have him check out the bias capacitors and resistors as well as rectifier diodes! Thanks, Andy. Surprisingly there are no diodes on the rectifier tube socket. All the caps and resistors seem to be a-okay. Link to comment Share on other sites More sharing options...
Andy R Posted February 25, 2011 Share Posted February 25, 2011 Thanks, Andy. Surprisingly there are no diodes on the rectifier tube socket. All the caps and resistors seem to be a-okay. Duh...I never really looked to hard at an 18 watter and didn't realize they had a tube rectifier thus no diodes (they would be the rectifier) . I know you're familiar with amps but i will add my 2 cents anyway. Well I'm assuming it was the power transformer that blew correct??? The Bias caps can fool you into thinking they're good. I went through two quads of 6550's (Ouch) once because of a freakin bad bias cap. It would test fine, bias would be fine and then the next thing you know the HT fuse would blow and tubes would be cooked. Finally realized that it wouldn't start leaking back current and causing the bias to drift until after you played it for a while... I took a quick look at an 18 watt schematic looks like a fixed bias setup with a shared bias cap? watch that thing like a hawk after you can get power to it. Might check your rectifier tube and the obvious potential pin shorts on the power tubes. I have found that usually fuse blows when there is component failure somewhere as opposed to power transformers. Guess you will find out quick if it is just a faulty transformer if it blows the correct size fuse again once it is replaced... Let me know I like to learn why things don't work... Might save me some money in the future[thumbup] Link to comment Share on other sites More sharing options...
L5Larry Posted February 25, 2011 Share Posted February 25, 2011 You most likely did additional damage to the amp with the overrated fuse. Never put an overrated fuse into any electrical devise, they have specific fuse ratings for a reason, preservation of the unit, AND safety of YOU. A word of advise AND caution: There are momentary anomalies that can blow a fuse such as a power surge, or fuses can blow because of a replaceable part such as a bad tube, plug or power cable. Try a second fuse of same and proper value, if it blows STOP, carefully unplug the devise and seek professional help. Link to comment Share on other sites More sharing options...
dbreslauer Posted February 25, 2011 Share Posted February 25, 2011 the Marshall 18W is cathode biased. i would have pulled the tubes and immediately started measuring currents and voltages: something downstream likely is not right. Larry's right: i'd say have your amp guy measure everything before just powering back up with a new PT. there's a GREAT site named 18watt.com that has extensive information on all things Marshall 18W, including recommended voltages and currents, troubleshooting techniques, etc. hope this helps! Don Link to comment Share on other sites More sharing options...
Andy R Posted February 25, 2011 Share Posted February 25, 2011 the Marshall 18W is cathode biased. i would have pulled the tubes and immediately started measuring currents and voltages: something downstream likely is not right. Larry's right: i'd say have your amp guy measure everything before just powering back up with a new PT. there's a GREAT site named 18watt.com that has extensive information on all things Marshall 18W, including recommended voltages and currents, troubleshooting techniques, etc. hope this helps! Don Oops yep... didn't notice the resistor with bypass cap Link to comment Share on other sites More sharing options...
retrosurfer1959 Posted February 25, 2011 Share Posted February 25, 2011 Ouch - Good luck man that hurts my 18 watt 74 is my baby it would really hurt to have anything happen to it. I won't say anything about the bigger fuse I've done the same thing myself when everything else looks ok and hell a few times it even worked. :unsure: Link to comment Share on other sites More sharing options...
Andy R Posted February 25, 2011 Share Posted February 25, 2011 Ouch - Good luck man that hurts my 18 watt 74 is my baby it would really hurt to have anything happen to it. I won't say anything about the bigger fuse I've done the same thing myself when everything else looks ok and hell a few times it even worked. :unsure: I did the old foil trick with a fuse in my car for my sub amplifier in my trans am. I never used my ashtray in the car and kept change in it. I pulled the lighter out one day and a penny fell in and shorted the wiring in the dash and i was trying like hell to find something to get it out of there as smoke was pouring up from the vents. That's when I first learned to take a dash completely apart to the firewall and rewire a harness.... As I said i learn more from my mistakes.... Link to comment Share on other sites More sharing options...
surfpup Posted February 25, 2011 Author Share Posted February 25, 2011 Well the new PT is bolted in. Tonight my bro is going to go over everything one more time before finishing the soldering and powering it up. Hopefully good things will happen when the current hits! Link to comment Share on other sites More sharing options...
Bowdiddley Posted February 25, 2011 Share Posted February 25, 2011 Here's to keeping the fingers crossed! Link to comment Share on other sites More sharing options...
TommyK Posted February 25, 2011 Share Posted February 25, 2011 Maybe they should put in some thermal overload protection to keep that from happening. Wish I could say I never did anything like that. :-" Link to comment Share on other sites More sharing options...
Andy R Posted February 27, 2011 Share Posted February 27, 2011 Surfpup, What's the verdict man? Is she smoking in a good way now? Did you find anything else wrong? I gotta know? Link to comment Share on other sites More sharing options...
MrNylon Posted February 27, 2011 Share Posted February 27, 2011 Thumbs up man! Link to comment Share on other sites More sharing options...
surfpup Posted February 27, 2011 Author Share Posted February 27, 2011 Surfpup, What's the verdict man? Is she smoking in a good way now? Did you find anything else wrong? I gotta know? I just picked it up tonight. My boy says it A-okay. Twas just the power transformer as we suspected. The new one I got from Triode Electronics in Chicago seems to be a better quality unit. Really pumped about the quality of their stuff so far. He's fixin to start a JCM 800 kit he got from them. Anyway, the 18 watter is back home where it belongs. I hope to put it through the paces tomorrow and see how it sounds. Link to comment Share on other sites More sharing options...
dbreslauer Posted February 27, 2011 Share Posted February 27, 2011 I just picked it up tonight. My boy says it A-okay. Twas just the power transformer as we suspected. The new one I got from Triode Electronics in Chicago seems to be a better quality unit. Really pumped about the quality of their stuff so far. He's fixin to start a JCM 800 kit he got from them. Anyway, the 18 watter is back home where it belongs. I hope to put it through the paces tomorrow and see how it sounds. that place is really close by us: i'd love to hear more about what you think of it. i've been tempted to check them out for a while. good luck with it! Don Link to comment Share on other sites More sharing options...
surfpup Posted February 27, 2011 Author Share Posted February 27, 2011 Ahhhhh... life is good again. Everything is working and sounding great. Man I love that amp. Even though it was only down for a week, I really missed it. (Not so sure my wife missed it though) Link to comment Share on other sites More sharing options...
surfpup Posted February 27, 2011 Author Share Posted February 27, 2011 that place is really close by us: i'd love to hear more about what you think of it. i've been tempted to check them out for a while. good luck with it! Don Oh yeah. Their stuff seems to be top notch. This power tranny is made by right there in Chicago. It's a solid hunk of American iron. Link to comment Share on other sites More sharing options...
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