TallonReazin Posted January 17, 2009 Share Posted January 17, 2009 Well, I'm a little embarassed to admit this, but I have to, to hopefully get the help I need. I was attempting to modify my epiphone valve jr from the 12ax7 down to a 12au7. I was in a bit of a dark room and should've done quite a few things differently, but it is what it is. Turns out I actually put the 12au7 tube in place of the EL84 tube. When you do this, you get a pretty cool smoke effect out of the amp, but no sound. I quickly turned it off when I discovered it was smoking, but the damage had already been done. There are globs of hot glue everywhere and the capacitor that sits by the EL84 was nice and shiny from the freshly heated/melted hot glue. And also the resistor beside the tube socket is actually a bit charred. Any ideas as to how to go about repairing this? I'll post some pics later tonight. Is it repairable, or should I just rebuild the whole thing? Thanks, TLN TLN Link to comment Share on other sites More sharing options...
Zephyr Posted January 17, 2009 Share Posted January 17, 2009 Oh man, that's quite a misfortune! If the damage was THAT severe, then I'd consult a professional tech rather than try it yourself even if you have the know-how. To me, it just seems too messy for a DIY. Never argue with an idiot. They'll bring you down to their level and beat you with experience. http://www.soundclick.com/bands/default.cfm?bandID=810593 http://www.myspace.com/dandelavega Link to comment Share on other sites More sharing options...
TallonReazin Posted January 17, 2009 Author Share Posted January 17, 2009 Well, it's not entire a DIY. My father has built a few amps before and makes custom electric guitars. (Speaking of which, I'll have to post some on here to get your opinions) He's experienced in wiring and electronics, but he recommended me getting a few other opinions from online. Perhaps other people have had other similar situations? Maybe? TLN Link to comment Share on other sites More sharing options...
miroslav Posted January 17, 2009 Share Posted January 17, 2009 I have one, among some pricey stuff...and I love it. BUT...it's only a $100 amp! You can get used ones for less than that on eBay. So.....you either get a used one and replace the entire PCB...OR...remove most if not all of the electronics and replace them. It's just so hard to tell how many components actually got fried...you might end up wasting a lot of time/effort playing trial and error...??? You would have to really understand what putting a 12xx7 type tube in the EL84 socket on THAT amp can do to the other components. You need the schematics and you need to really know how all that stuff interacts at the component level. There are a couple dedicated Epi Valve Jr. DIY websitesjust hit Google, you will find them. Many of those guys have chopped up those little amps 6 ways to Sundayand Im sure some of them will be able to guide you quite well in your repair efforts. Also...you can just replace what appears to be visually damaged...and leave the rest alone...plug 'er in...(stand back ) and then see what you got. :grin: You're not going to incur too much cost on a couple of caps and resistors...so use it as a learning experience. miroslav - miroslavmusic.com "Just because it happened to you, it doesn't mean it's important." Link to comment Share on other sites More sharing options...
picker Posted January 17, 2009 Share Posted January 17, 2009 There are globs of hot glue everywhere Do you know where and/or what it came from? Glue is not usually a large component in tube amps. I may be wrong but I'd guess it's the innards of your big power filter cap(s), and they blew up when the wrong size or type of voltage hit 'em. Get your electronically savvy in-law to discharge that cap or caps and test it with a multimeter to see if the marked value is still right. and the capacitor that sits by the EL84 was nice and shiny from the freshly heated/melted hot glue. Just replace it. And also the resistor beside the tube socket is actually a bit charred. That's probably where the smoke came from, or some of it anyway. Replace that too, and the tube you wired up wrong as well. It's probably toast, or near enough to it that you want to replace it. Wire it up right and plug it in. If it doesn't explode and the pilot light comes on, hook it up to a speaker, and plug in a guitar. If it works, you're home. If it doesn't work, there aren't too many more major parts to replace. The choke transformer and output transformer are pretty much all that's left. There are replacements you can buy, some more costly than others, but you'll probably pay as much as another Valve Jr would cost to get them. Always remember that you are unique. Just like everyone else. Link to comment Share on other sites More sharing options...
Bluesape Posted January 17, 2009 Share Posted January 17, 2009 I'm no tech, but it sounds like ya got a nightmare on your hands. I'd just grab another, seein' how it's dirt cheap. If this happened to, say, a JMP, Twin, AC30, etc, ya'd have somethin' worth fixin', but fiscally speaking, in this case ya don't. Never a DUH! moment! Well, almost never. OK, OK! Sometimes never! Link to comment Share on other sites More sharing options...
miroslav Posted January 17, 2009 Share Posted January 17, 2009 There are globs of hot glue everywhere Do you know where and/or what it came from? Yeah...that's not too common. Im wondering if it's just the dielectric goop from inside the caps after they tossed their cookies? miroslav - miroslavmusic.com "Just because it happened to you, it doesn't mean it's important." Link to comment Share on other sites More sharing options...
Bluesape Posted January 17, 2009 Share Posted January 17, 2009 Hmmmm......ask Myles..... Never a DUH! moment! Well, almost never. OK, OK! Sometimes never! Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted January 18, 2009 Share Posted January 18, 2009 Damn, that's a good example of a bad catastrophic failure!! Nasty! It hadn't occurred to me that you could fit an EL84 into a 12A*7's socket, I didn't know they were that similar in both dimension and pin-out. I'm with picker and miro on the goop, and Bluesape on the matter of this being a major enough project that it might be more cost-effective to write it off. ALTHOUGH- I have seen gobs of yellowed, hardened "hot-glue" put here and there on the components inside cheap amps before, as a cheap means of reducing rattling, microphonics, play in parts damaging connections, etc. (There's also a highly heat-resistant silicon RTV compound that's sometimes used, far better quality than the "hot-glue"; it looks sort of like calk or rubber-cement, and is usually clear.) And, I've seen absolutely shameful amounts of left-over flux-residue from wave-solder production, looking like some kind of syrup had once been spilled. Maybe that's what you're seeing in there? Or is it definitely the result of something melting/burning in this catastrophic failure? If your Dad is experienced in electronic repair along these lines and would know what to look for, then you both might be able to make it worthwhile to repair the amp. (In the following I'm not trying to dissuade you from repairing the amp, only trying to make sure that you do it right- and safely- the first time.) There's a LOT of damage in there, and possibly in places that wouldn't be visibly obvious or something you'd intuitively look for. And if you miss something and power it up, even more damage could occur. Components that could've taken damage or problematic residual crap like arc or the aforementioned gluey-goop include all of the tubes, the rectifier, caps, resistors, the PCB (I would have little enough confidence in such an amp's PCB even when brand new, let alone after this kind of heat and burning damage; there's a reason they can sell amps like these so cheaply), the tube-sockets, the output-transformer, the power-transformer and power-supply components, the power-switch... lots of stuff to look for, probably lots to replace. Thoroughness counts; that may seem like a lot to look through, but if you power-up and something's still not right in there, more damage can occur to even more parts- both the old ones, and the new ones you just installed. AND SAFETY IS OF PARAMOUNT IMPORTANCE- we don't want to add YOU to the list of things destroyed by the amp's electrical failure!! Good, proper Mil-Spec soldering and assembly workmanship is very important, too (even if the amp was originally manufactured to consumer-grade "standards"). If you do repair it, for safety- both your own, and the amps- install some extra fuses in various places, an MOV across the incoming AC at the power-switch, and some diodes between the plate and cathode of each of the EL84 output-tubes; if you get that far, I'll help you with links, info, etc. as much as I can, as will others here, including Myles who's ridiculously super qualified for tube-amp matters. Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
miroslav Posted January 18, 2009 Share Posted January 18, 2009 I've been inside my Epi VJ...and there's not too much hot glue on the PCB...a bit here-n-there...though it's possible his was done by a sloppy assembler. miroslav - miroslavmusic.com "Just because it happened to you, it doesn't mean it's important." Link to comment Share on other sites More sharing options...
RocketRick Posted January 18, 2009 Share Posted January 18, 2009 What Bs said..myles is the man. Money may buy a fine dog, but only kindness will make him wag his tail. Link to comment Share on other sites More sharing options...
Bluesape Posted January 19, 2009 Share Posted January 19, 2009 I still say it's spilled milk... Never a DUH! moment! Well, almost never. OK, OK! Sometimes never! Link to comment Share on other sites More sharing options...
TallonReazin Posted January 19, 2009 Author Share Posted January 19, 2009 Sorry that I didn't get the pics up this past weekend. I'll attempt to do this at some point today. RE: Hot Glue; These were there when I first opened up the amp. I agree with Caevan that they are anti-rattle or some other purpose. Nothing exploded to send the hot glue or silicon everwhere. There's a glob at the base of most of the caps and a few other places that were intentional. Perhaps they were installed so when people install something wrong, they can quickly identify the part of the board that got WAAAAY too hot. =) I've left it unplugged for quite a while so the voltages should be running out by now. Even so, I'll make the attempt to discharge the components. I don't want the amp to do to me what I did to it! What I think I'll end up doing is testing the caps and resistors and replace the fried ones. If things still don't work, I'll attempt to rebuild it entirely; I'll end up with a better amp in the end by doing this. Or at least an amp with higher quality components. Either way, I plan on learning a lot through this process. on a side note, my brother was attempting to fix an old fender champ that someone had modded. He wanted to put it back to factory specs and did so successfully except for one of the caps, I believe. I think he said he has the neg on the ground, ground on the pos, and pos on the neg; not an equation for success. He turned on the amp and heard a electronic sound that increased up to a loud "POP!" and then the smoke started pouring out of the amp. Luckily, mine wasn't quite as extreme as this. After telling me this story (making me feel a little less like a moron) he said "welcome to the world of tube amps!" Has anyone else fried an amp trying to mod it? TLN Link to comment Share on other sites More sharing options...
picker Posted January 19, 2009 Share Posted January 19, 2009 You may have lucked out. If the glue was there before, it may be you only fried that resistor. I'd replace it, the tubes, and the cap you mentioned, and see what happens. Always remember that you are unique. Just like everyone else. Link to comment Share on other sites More sharing options...
miroslav Posted January 19, 2009 Share Posted January 19, 2009 on a side note, my brother was attempting to fix an old fender champ that someone had modded. He wanted to put it back to factory specs and did so successfully except for one of the caps, I believe. I think he said he has the neg on the ground, ground on the pos, and pos on the neg; not an equation for success. He turned on the amp and heard a electronic sound that increased up to a loud "POP!" and then the smoke started pouring out of the amp. Luckily, mine wasn't quite as extreme as this. After telling me this story (making me feel a little less like a moron) he said "welcome to the world of tube amps!" Has anyone else fried an amp trying to mod it? Maybe you guys should move on to something else... miroslav - miroslavmusic.com "Just because it happened to you, it doesn't mean it's important." Link to comment Share on other sites More sharing options...
BadLife Posted January 19, 2009 Share Posted January 19, 2009 Hum cheap amp like that I would just give it a go for practice. I assume you know basic electronics safety. Link to comment Share on other sites More sharing options...
LeftyBlues Posted January 19, 2009 Share Posted January 19, 2009 Something I learned years ago in electronics school is that electrical stuff works great unless you let the smoke out. Once the smoke is set free, daggon things are durn near useless. I have a Valve Special I never use I'd sell to a fellow forumite if you're interested. L.B. I was born at night but I wasn't born last night... Link to comment Share on other sites More sharing options...
TallonReazin Posted January 19, 2009 Author Share Posted January 19, 2009 on a side note, my brother was attempting to fix an old fender champ that someone had modded. He wanted to put it back to factory specs and did so successfully except for one of the caps, I believe. I think he said he has the neg on the ground, ground on the pos, and pos on the neg; not an equation for success. He turned on the amp and heard a electronic sound that increased up to a loud "POP!" and then the smoke started pouring out of the amp. Luckily, mine wasn't quite as extreme as this. After telling me this story (making me feel a little less like a moron) he said "welcome to the world of tube amps!" Has anyone else fried an amp trying to mod it? Maybe you guys should move on to something else... Ouch.... How would we learn anything that way? =) TLN Link to comment Share on other sites More sharing options...
miroslav Posted January 19, 2009 Share Posted January 19, 2009 School/books...etc. Simple stuff like knowing which tube goes in which socket...and NOT to connect the negative to the positive... ...isn't something you really want to "learn" through trial-n-error...'cuz you guys are gonna go through a lot of amps that way! :grin: It's always good to get a little theory before the practical experimentation begins. Ahh...I hope you both at least know what NOT to touch in an amp with your bare hands..??? miroslav - miroslavmusic.com "Just because it happened to you, it doesn't mean it's important." Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted January 19, 2009 Share Posted January 19, 2009 Inspect that tube-socket (in fact, inspect all of them) very closely for any melting or burning damage, and for any arc- a dark, singed looking carbon build-up. If there is any, it's really best to replace the socket, and since you're replacing it, go directly to a ceramic/porcelain socket, do not bother with plastic or bakelite sockets. Any arc build-up will lead to further electrical arcing and shorting in the future. And replace any of the caps or resistors that are suspect in the least upon visual inspection. if they don't look right, they aren't. Hopefully, the parts that burned took the brunt of it, and spared the output-transformer from being damaged. Closely inspect the PCB, particularly around that socket and those components and along the traces that lead away from them. Clean it well with contact-cleaner. How are your soldering skills? What are you going to use to de-solder and solder? Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
Bluesape Posted January 20, 2009 Share Posted January 20, 2009 We're not beatin' up on ya here, but it seems you're in over your head, and could get hurt or worse without some qualified guidance. I truly believe this amp is cooked, for all practical purposes. Sure it could be totally refurbished, but likely not for the dollar value of a used Valve Jr. BTW - have you asked Myles? He's an amp god dispensing free advice for our members. Never a DUH! moment! Well, almost never. OK, OK! Sometimes never! Link to comment Share on other sites More sharing options...
Terrell Posted January 20, 2009 Share Posted January 20, 2009 You may want to see this as an opportunity. There are a lot of inexpensive point to point kits for the Valve Jrs. The kit's will pretty much replace everything on the board including the board... I have two of them... Love em as power amps with 12at7s! Link to comment Share on other sites More sharing options...
Junior 1 Posted January 20, 2009 Share Posted January 20, 2009 You could get $40 - $50 on Ebay just for the cabinet and speaker! You could then get a nice used one on the Bay for $100. For the net cost of $50 or so you could be back playing. Good luck with whatever you do and be careful. Link to comment Share on other sites More sharing options...
TallonReazin Posted January 20, 2009 Author Share Posted January 20, 2009 I'm keeping an eye out on ebay for parts and pieces and a have found a few things; none as cheap as what's been mentioned though... perhaps I'm searching the wrong thing? I haven't seen one of those kits before. Point to point kits, eh? May the google-ing commence! I have checked for the arching and see none. That particular issue I was aware of. My soldering skills seem to be up to par, but I haven't considered what to use yet. I'll probably go to my dad on that one. If the new caps and resistors don't work I'm just going to chalk it up to the Output Trans. at which point the point to point sounds even better. Pics, believe it or not, are on the way. I keep waiting on someone to say "pics, or it didn't happen." =) TLN TLN Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted January 20, 2009 Share Posted January 20, 2009 For desoldering for the removal of bad components, you can use a soldering-iron and what's known as solder-wick, a braided metal wire material that is steeped in flux; you put it against the solder-joint, and press carefully with the soldering-iron to heat it and the joint beneath it; the solder will melt and wick up into the braid. Just be careful not to overheat and/or press too hard, as it's actually very easy to severely damage pads and traces in PCB's, even heavy-duty, high-quality double-sided through-hole styles, let alone the cheap and flimsy PCB's found in most consumer-grade electronics (including a LOT of guitar amps). And that's way more damage than you want to have to deal with! So be careful, ask for help from someone more experienced if needed, and avoid that! Gheeze, if you lived down the road from me, I'd do loads of this stuff for you for free, or show you some of it. By the way, I like the Calvin & Hobbes avatar! Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
TallonReazin Posted January 21, 2009 Author Share Posted January 21, 2009 I have no clue if this picture is going to show up or not. I might have to try again. TLN Link to comment Share on other sites More sharing options...
TallonReazin Posted January 21, 2009 Author Share Posted January 21, 2009 Can you guys see the pic? TLN Link to comment Share on other sites More sharing options...
Caevan O’Shite Posted January 21, 2009 Share Posted January 21, 2009 Aaaaaah, I see the problem (with your image not displaying)... " C:\Documents and Settings\bhapps\Desktop\captions amp.JPG " must be the location on drive-C in your computer; this 'site doesn't support uploading of files like that, only the display of hosted files via UBB code. So, what that boils down to, is that you'll need to upload that jpg-file image to a 'site like Photobucket or the like (there are also others for hosting music like mp3 files), or your own website, and then copy-&-paste the url-address for that into the " " image/url/ubb-code brackets. Like this (I'll deliberately make a mistake in the first "img" code so that it displays as text instead of the image): Get yourself a hosted URL address for the desired image one way or another, and then: " http://www.batonrye.com/alex/Calvin_Hobbes%5B1%5D.gif " to " http://www.batonrye.com/alex/Calvin_Hobbes%5B1%5D.gif%5B/img%5Bb%5Dg%5B/b%5D%5D%20http://www.batonrye.com/alex/Calvin_Hobbes%5B1%5D.gif' alt='Calvin_Hobbes%5B1%5D.gif'> If an image is particularly huge, too large to display within one of these posts, you can instead provide a link via " http:// " brackets, like this. (Clonk on the bold-font "this", and the image will be displayed in another window.) (" [url=http://www.batonrye.com/alex/Calvin_Hobbes%5B1%5D.gif]this[/bb][/urll] ") Ask yourself- What Would Ren and Stimpy Do? ~ Caevan James-Michael Miller-O'Shite ~ _ ___ _ Leprechaun, Esquire _ ___ _ Link to comment Share on other sites More sharing options...
TallonReazin Posted January 21, 2009 Author Share Posted January 21, 2009 http://farm4.static.flickr.com/3451/3214803669_821c2f4678_o.jpg How about this one? also, I looked a bit for the point to point kits and perhaps I'm just searching for the wrong thing, but I found very little useful info. What specifically should I be searching for? TLN Link to comment Share on other sites More sharing options...
TallonReazin Posted January 21, 2009 Author Share Posted January 21, 2009 Here's a link to a few photos that if you guys have questions about a photo, ask on here. I don't check flickr very often so asking on there may not get a response from me very quickly. TLN Link to comment Share on other sites More sharing options...
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