I was playing a club gig the other night with my 2-year-old Crate V16 Palomino 1X12. Had the Gain cranked to 5 o'clock, the Level cranked to 12 o'clock, Treble Mid and Bass set flat at 12 o'clock, and my MIJ Strat Volume at 7. The amp just cut out on me...no hiss, no buzz, no nothing. Walked over to the amp, and the power switch had flicked itself to ''Off.'' Flicked it back to ''On''...nada. Unplugged, replugged...nada. Waited overnight, replugged...nada. I have the board schematics, and am attempting to self-diagnose, as I live in Saudi Arabia; haven't gone to the local amp techs (mostly Filipinos who know Yamaha solid state amps real well...).
Things I can think of: 1) Power transformer headed south on me.
2) One or more power tubes (2 EL34's in this config) zorched. 3) The PT fuse zorched. 4) All of the above. Haven't opened the back of the cab to look yet. Any thoughts would be most appreciated, as I will be back in the States in a month for parts or replacement. Ron
Start easy. You could have a bad power switch. Do you get any kind of indication of any life at all, like tube filiments or front panel indicators? If the fuse is blown you have a fault that is drawing excess current, in which case you can check the rectifiers that create your bias voltages, yank the output tubes to see if they have an internal short, less likely would be a shorted filter capacitor (although I have seen it). You could also have a bias problem on the output tubes that causes them to draw excess current and likely makes the tube(s) glow bright red before popping the fuse. If this is the case, look for shorted or leaky coupling capacitors and burned bias resistors, or maybe just a tube with internal shorts, and you will likely have junk tubes as a bonus (they don't take kindly to glowing bright red- meaning a glow that is far more intense than the soft glow of the filiments). If the fix gets more involved than all of this, give me your email addy and we can get hard core.
Well I thought that could be an issue, although I considered it fairly unlikely.
I have done that same repair myself, although I was replacing a current fuse, not a thermal fuse. I have, in fact, never seen a thermal fuse in a PT and have only seen any kind of fuse in PT's made specifically for a manufacturer of some kind of equipment, and in my worst scepticism it is so they can simplify construction and keep costs down, while in some way convincing you to buy either an expensive PT or a new unit when the PT fails (out of warranty).
I would imagine that the fix they did for you, which is fairly involved and quite delicate work, will allow your amp to function just fine. Just to make sure, check how hot it gets. It is not uncommon for the iron core of a PT to be difficult to hold your hand on after it has been running for awhile, but if it is so hot you think you will be burned, it's pushing it. Having 2 output tubes, you have a 50 watt amp so probably about 100 watts into it (or so) and half of it becomes heat or light. With 120 VAC in, that would require just under 1 amp constantly so a 2 amp fuse would probably be a good choice (to allow for surges), I would consider 3 amp to be max. If you are using 240 VAC, the current would be half and so would the fuses (watts=volts X amps).
Power transformers can be had, but PT's suitable for use with tubes are a bit trickier to find. You need to know the AC voltage on the secondary side for each winding, whether they have taps and where on the windings they are (Xvolts-center tapped as an example) and what the current requirements are for each secondary. You can determine these characteristics either through a spec sheet or from voltage and current measurements with a meter (under max load) or from adding up the requirements of each section of the circuitry and calculating for waste as well. Then choose a PT that exceeds your current requirements a bit, but not too much (power supply voltage sagging assists in creating the unique sound of a tube amp). A good quality PT with minimal eddy (power soaking and heat generating magnetic) currents in the core would be more desirable than a far beefier current spec.
If you are concerned about the potential for fire, get a thermal fuse
rated for 200 degrees F and attach it to the core of the PT, inline
with the primary power (that also goes through the current fuse).
That said, I would advise to leave it alone unless you must do something about it.
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rjivaro,
Thanks for attempting to long-distance diagnose the problem with my Crate V16. Here's my e-mail address: [email protected]
After I got home yesterday, I opened up the cab, and v-e-r-y carefully eased the amp out of it, being careful not to touch any transformers, capacitors or tubes. I found the fuse to the power switch, and removed it to look at it. Fuse was still intact. I v-e-r-y carefully visually checked all plug-in connections, and most of the soldered connections for resistors and such, and found nothing obviously unplugged or unsoldered. I very carefully visually examined the EL-84 (not 34's as I said previously - tube envy) power tubes, and noticed no dark discoloration or spotting inside the glass bottles. The tubes were well seated in their sockets (I did not use my bare fingers; I wrapped some paper towels around the tubes and handled them that way). I then very carefully examined the 3 12AX7a preamp tubes, and noticed no dark discoloration or spotting inside their glass bottles. Since this is all I had time to do visually (no time to start getting out the multimeter, shocking myself into insensibility or death, or otherwise screwing things up that were perfectly good), I buttoned it all back up, hooked the speaker back up, plugged it into the wall, and got...nuthin'. No power. No power indicator light coming on. Tubes won't light up. No hum, no noise, absolutely nothing coming out of the box, because no power is getting to it. It could be a bad power switch, dunno. Could also be the PT, as I have been reading anecdotal reports on the Web about the Crate V-series having trouble with their PTs needing replacement after very short periods of time. I purchased this amp from Guitar Center in Dec 2006 (not 2007 as I stated above - it is a 2005 model according to other anecdotal evidence inside the amp, and states that it was "designed and manufactured in the USA" - Yellville, Arkansas, according to the documentation I have. I know SLM and Crate sold themselves to Ampeg fairly recently, and that they have shifted manufacturing to Vietnam and China.), have the original receipt, and so the electronics are still under their 5-year warranty. I have heard of other Crate owners going months trying to get warranty service, so am hoping that GC will replace with either repairs, or similar model or make; my wife has OK'd shipping the amp back to the States on our next trip, or even letting me buy a replacement for Father's Day, but I really do like the tones I get out of this amp when it's working properly. I A/B tested it against its competition (Fender Blues Junior, Epiphones, small Peaveys, etc.) and liked it the best for the classic rock and blues that I play. Let's continue further correspondence via e-mail, and I really appreciate your help! Best Regards, Ron
rjivaro,
Just to update you on the Crate V16. It has been resurrected by the local electrical specialists who work on sound equipment here. According to their bench tech, who called me last night, they were able to diagnose the problem, and "fix" it. The problem was indeed a burnt out power transformer. The internal thermal fuse had blown. They "converted" the PT so that there is no internal fuse (e.g., it flows direct), and they installed an external fuse just outboard of the PT. They claim to have done this with other amps numerous times with no problems.
What I'm wondering is, that PT was designed with the internal thermal fuse for a reason. What is your opinion of what will happen if I use it as is, and is there some other type of PT I could replace their "fix" with if necessary?
Best Regards, Ron < [email protected] >
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