ChewingAluminumFoil Posted April 9, 2006 Author Share Posted April 9, 2006 That's odd, ricochet. I had exactly the opposite. Adding more caps to main supply almost completely quieted the constant hum that was unaffected by the volume control. Going DC on the filaments dramatically quieted the hum which varied with the volume. And finally that one jumper wire making the input group a little better knocked the rest of the volume-variant hum way back. You sound like a real electronics vet, so I'm hesistant to ask, have you triple checked your wiring? CAF Link to comment Share on other sites More sharing options...
cockroach Posted April 12, 2006 Share Posted April 12, 2006 A 4w bulb with a Valve Junior yields pretty heavy compression, a 7w sounds nominal, and higher wattages don't do much Hi All Forgive the ignorance here, but does the voltage of the bulb make a difference? Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted April 12, 2006 Author Share Posted April 12, 2006 Yes, it has to be a 12v bulb, available in the outdoor lighting section of any home improvement store. CAF Link to comment Share on other sites More sharing options...
Basshappi Posted April 14, 2006 Share Posted April 14, 2006 Okay guys, I would like some suggestions.... I'm gonna pull the trigger on a cab to use with my VJ Head. SS Cabs 1x12 is the winner. Here's the question: Open back w/ Eminence 'Texas Heat' (150w) or Closed Back w/ Weber Signature. (25w) The price is so close as to be negligable. I'm leaning towards the Texas Heat, Blues and Classic Rock are what I'll be working on most so......Opinions? Nothing is as it seems but everything is exactly what it is - B. Banzai Life is what happens while you are busy playing in bands. Link to comment Share on other sites More sharing options...
miroslav Posted April 14, 2006 Share Posted April 14, 2006 I think for a 112...a closed-back will give you the "chunk" you want for Blues.... My Traynor YCV40 is a 112 open-back combo. But I also got the 112 closed-back extension cab for it. I can't remember the last time I used the 112 in the combo....it's usually disconnected, and I only use the closed-back 112 because the open-back is just way to bright and brittle sounding for my tastes. Of course...I also have other cabs that I use...my favorite right now being a 115 reflex cab. But between the identical speakers of the Traynor YCV40 (Celestin Vintage 30)...I prefer the sound of the one in the closed-back cab. 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...
Ricochet Posted April 14, 2006 Share Posted April 14, 2006 Originally posted by ChewingAluminumFoil: You sound like a real electronics vet, so I'm hesistant to ask, have you triple checked your wiring? Yep. Only thing I did was rectify the heater current. There are no changes to the wiring of the amplifier, I inserted a bridge rectifier between the original heater leads and the heater terminals on the board, with the filter capacitor across the DC terminals of the bridge. The original 60 Hz hum that was fairly loud, not responding to the volume control, was coming from the AC heater lines being immediately adjacent on the PC board to the grid line for the second stage of the 12AX7, returning from the volume pot. Bad PC board layout. It pretty much went away with rectifying the heater power. The very faint 60 Hz hum that responds to the volume control, only becoming noticeable with the first hum having been removed and with the volume cranked up, is 60 Hz electromagnetic field being picked up in the first stage, probably radiated field from the power transformer. It's not enough to fool with. The new loud 120 Hz hum is electromechanical sound resulting from magnetoconstriction in the core of the transformer, brought out by dividing the heater current that was in a smooth 60 Hz sine wave into short, sharp pulses of current at 120 Hz repetition rate, with lots of higher harmonics. The metal chassis amplifies it like a guitar top or piano soundboard. The heater rectification mod took away one hum and replaced it with another. If you're not hearing it, your power transformer's better built than mine. Tightly clamping the laminations and potting them well with varnish are done to reduce this electromechanical hum. I'm not too bothered by it, as I wasn't by the original hum. I'm not going to mod it any further. I've got a Pignose G40V (that I had to modify by inserting resistors in the heater lines to prevent frying the tubes with 7.5VAC), and it hums worse than the Valve Junior ever did. I might rectify its heater supply. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
low_fidelity2100 Posted May 2, 2006 Share Posted May 2, 2006 Hi, I just bought a valve junior, and I was trying to do the mod that converts the Filiments to DC. Like I saw on the Valvejunior.com website. I Got a Bridge rectifier from radio shack (Its a "full wave Bridge rectifier" 25 amps, 50 volts), and a 100uf/35v. And I did everything correctly, But when I turned the amp on There was no sound at all. So I checked everything over, and saw nothing wrong, so tried it again and Still no sound. So finally I just decided to return everything to stock and try and figure out what I'de done wrong, But when I tried it after returning everything to normal, It still doesn't work. I was hopeing That maybe Someone here could give me some advice as to what I should do to get it working again? Even if its back to stock, and still humming, As long as its actually working. So Please help with some advice. Cause I've had this thing for a week and Now I've managed brake it and I'm super bummed, so if anyone has any suggestions, please help. I'm really worried that sumthing is perminately broken and I dunno what to do. This is my first time ever working on an amp, so any advice anyone could give would be really really helpful. Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted May 2, 2006 Author Share Posted May 2, 2006 Do the tube filaments light up? The lugs that the filament supply attach to can tend to break the trace on the circuit board if you wiggle them trying to get the wires off. That happened on one of my VJs. Look for cracks in the foil trace near those lugs and if there's a crack, bridge the crack with solder or with a tiny piece of wire and solder. I'm assuming the front pilot light is coming on at least and that you didn't just blow the main fuse that's sorta hidden in the AC supply connector on the back. As for it being "permanently broken", relax, there really are very few things you can do to a tube amp that can cause "permanent" damage. Now transistor amps, you can pop every power transistor in the final stage(s) in the blink of an eye but tubes tend to be a *lot* more forgiving. CAF Link to comment Share on other sites More sharing options...
low_fidelity2100 Posted May 2, 2006 Share Posted May 2, 2006 Originally posted by ChewingAluminumFoil: Do the tube filaments light up? The lugs that the filament supply attach to can tend to break the trace on the circuit board if you wiggle them trying to get the wires off. That happened on one of my VJs. Look for cracks in the foil trace near those lugs and if there's a crack, bridge the crack with solder or with a tiny piece of wire and solder. I'm assuming the front pilot light is coming on at least and that you didn't just blow the main fuse that's sorta hidden in the AC supply connector on the back. As for it being "permanently broken", relax, there really are very few things you can do to a tube amp that can cause "permanent" damage. Now transistor amps, you can pop every power transistor in the final stage(s) in the blink of an eye but tubes tend to be a *lot* more forgiving. CAF The filiments weren't lighting, but The front power light was comeing on. And I did check to see if perhaps I had accidentally broken on the the CB traces, and I hadn't. I actually Found out what the problem was, and fixed it, so now its working again. The problem was The fuse in the Orange wire from the transformer had Popped, So I stuck a new one in (T4AL 250V) and Powered it up, and everything is working fine now! I feel pretty dumb. I had made sure to check the fuse in the AC in jack where the power chord plugs in, But actually didn't even realize there were fuses on the transformer. All my worrying, and it was just a fuse. And being as the few blew (apperently) when I made the mod, I must have done sumthing wrong. But I can't figure out what. Any Idea what might have caused the fuse to blow when I had wired it through the rectifer? On the back of the rectifers packageing There was a picture showing which legs on it where for what. Two legs (diagnal corners from eachother) Where labled AC, And the Other two were labled + and -. I had Connected The two orange wires To the Two Ac legs (Which were previously on t6 and t5 of the board). And Ran a Jumper From The + post to The Post on the Board Labled T6. And a Jumper From The - Post on the Rectifier To the Post labled T5. And Connected the Capacitor Going From The + post to the - Post. Is that correct? Thats what it looked like I was suppoused to do Based on the schematics I've been useing. But I've never really worked with Rectifiers Before, So I'm guessing I'm wrong (and a fuse blowing Kinda makes me believe that even More). Please lemme know whats the correct way to connect the connections? And also The rectifer Mod is the one that gets rid of the Buzz Right? The hum doesn't really bother me, half my pedals hum more than the amp. But the Buzz Drives me nuts sumtimes. And again Thanks For the Help guys. And Denis/Chewingaluminumfoil Thanks for Makeing The Valvejunior.com website. All the info is really useful, just reading it helped me kinda understand my amps a little better (not just valve jr.'s either). -edward Link to comment Share on other sites More sharing options...
Ricochet Posted May 2, 2006 Share Posted May 2, 2006 Sounds like you hooked everything up properly, BUT, were you aware that the electrolytic capacitor is polarized? Its cathode has to be hooked to the negative side, and its anode to the positive side, or it short circuits the current. After this happens, the capacitor has to be "re-formed," and may be ruined. Usually there's a marking on the side of the capacitor that looks like an arrow. It points to the cathode. It's actually pointing to the direction in which "conventional current" flows, from positive to negative, just like the symbol for a diode. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
low_fidelity2100 Posted May 2, 2006 Share Posted May 2, 2006 Originally posted by Ricochet: Sounds like you hooked everything up properly, BUT, were you aware that the electrolytic capacitor is polarized? Its cathode has to be hooked to the negative side, and its anode to the positive side, or it short circuits the current. After this happens, the capacitor has to be "re-formed," and may be ruined. Usually there's a marking on the side of the capacitor that looks like an arrow. It points to the cathode. It's actually pointing to the direction in which "conventional current" flows, from positive to negative, just like the symbol for a diode. Yeah, I'm pretty sure I hooked the electro cap up correctly. But maybe not (actually probably not considering sumthing shorted), So I guess I'll just buy another and Try rewireing it again, and Make sure I've got the polarity goin in correctly this time. hopefully that'll work. Thanks. Link to comment Share on other sites More sharing options...
Ricochet Posted May 2, 2006 Share Posted May 2, 2006 I recently bought some new electrolytic caps off the rack at a local electronics store that went into my organ as screen bypass caps. When I started it up, they were so leaky and noisy that I was scared I'd hooked 'em backward and shut it down, took it apart and checked 'em, even though I'd carefully checked and rechecked before soldering them in. They were in properly, so I fired it back up and let 'em re-form under the working voltage of the amp, and after a couple of minutes they got quiet. They'd just sat on the shelf till the aluminum oxide film on the foil had broken down. You could have gotten a similarly leaky "NOS" cap. (There are no date codes apparent on the leaky caps I bought.) Try checking it with an ohmmeter. It's also possible that there could be a shorted diode or diodes in your bridge rectifier, especially if it got hot while soldering. Check it out for current flow only in the proper directions. Ought to show an open circuit or very, very high resistance in reverse. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
low_fidelity2100 Posted May 3, 2006 Share Posted May 3, 2006 So, After getting myself all freaked out before, and then finding out it was only a fuse that had blown, I decided to try wireing the rectifier back in. And Upon checking everything, I had Installed the Previous electro cap Backwards. Which is probably why the fuse blew (from what ricochet said). So I rewired it like it was before, this time with a 2200uF/16v cap (wire correctly this time, haha), And It works perfectly now. With No Buzz!!!! So I want to thank everyone that helped, Its massively kool of ya guys to give advice to a total stranger, Let alone one with such a low post count (haha). And is it Just me, Or Does installing the rectifier and cap Make the amp Seem a bit brighter? It certainly seemed to make mine brighter. Thanks again everyone. -edward Link to comment Share on other sites More sharing options...
Ricochet Posted May 3, 2006 Share Posted May 3, 2006 All right! That's terrific! "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
schucky Posted May 12, 2006 Share Posted May 12, 2006 Hello, I'm new here...I just wanted to thank y'all for the info provided in this thread. I picked up a Valve Jr and loved the sound for the $$$ but the buzz was horrible. I did a couple mods listed here and it's buzzfree. Thanks! One question If I may: I did the bridge rectifier mod but could only locate a 1000uF capicitor that is rated at 35 volts (as opposed to 16) It's listed on the back of the package as 35WVDC (???) Will this have any adverse effect? Seems to work great so far. Thanks again Chris Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted May 12, 2006 Author Share Posted May 12, 2006 Nope, not a problem. You can pretty much always go up in working voltage ratings with caps. CAF Link to comment Share on other sites More sharing options...
Junior 1 Posted May 12, 2006 Share Posted May 12, 2006 Has anyone tried a Electro Harmonics 12AX7 in the VJ? If so, did it make a difference in the hum? Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted May 12, 2006 Author Share Posted May 12, 2006 Yes, I mention that on my www.valvejunior.com page. And I quote: Note: yes, I did try some of those tubes that EH says ostensibly reduce hum, but I didn't hear any discernible difference. You gotta solder, kids. CAF Link to comment Share on other sites More sharing options...
Ricochet Posted May 12, 2006 Share Posted May 12, 2006 The hum is not from the tube. It's from the bad layout with the grid trace to the second stage being right next to, and closely parallel to, the AC heater leads. Changing the tubes won't help. Neither will increasing the size of filter capacitors, or changing the grounding of the input jack. Those aren't the causes of the hum, either. It can only be alleviated by rectifying the heater current. However, in some cases (like mine) a new hum from the transformer core may result from rectifying the heater current. Far too much has been made of this hum. It's not worse than the hum on many vintage tube amps. No one will ever be bothered by it in playing live music. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
Junior 1 Posted May 12, 2006 Share Posted May 12, 2006 Thanks,ChewingAluminumFoil. I guess I'm going to sell my VJ combo and get the head. I've never worked on tube amps before and even if I sell it for $75,it's easier than trying to find a tech to do the work. I bought it in Feb. 06'and love the sound, but between the single coils and the hum!!! Thanks, I was looking for the easy way out. Link to comment Share on other sites More sharing options...
Ricochet Posted May 12, 2006 Share Posted May 12, 2006 I've read recently that the currently produced combos incorporate the same mods to reduce hum found in the heads. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
Junior 1 Posted May 12, 2006 Share Posted May 12, 2006 I also heard that Ricochet. I have a 1x12 8 ohm cab that sounds good with the combo, so I figure I'll use it with the head, which has an 8 ohm speaker jack. Link to comment Share on other sites More sharing options...
schucky Posted May 12, 2006 Share Posted May 12, 2006 "Far too much has been made of this hum. It's not worse than the hum on many vintage tube amps" This was not the case with mine. I have a few tube amps from the 60's and 70's. They don't hum (or should I say buzz) like my Valve Jr did. I have read that other people don't seem to be bothered much by noise so maybe it varies from jr to jr??? Or maybe there are variants in the AC from house to house??? The Buzz I had was almost identical to the buzz you get from having a florescent light on on the same circuit as the amp or when you accidently plug a guitar in with a speaker cord. it was a super annoying, ratty buzz that could be heard over the guitar at higher volumes. I first isolated the jack and jumpered the ground on the back of the board. This alone did nothing. After installing the bridge rectifier and cap the ratty buzz was gone. It still has some hum but not enough to bother me or to prevent me from recording with it. Thanks again for all the helpful info! Chris Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted May 12, 2006 Author Share Posted May 12, 2006 Yeah, I have a class A Kalamazoo "vintage" amp with zero hum. Original caps and all. Similar circuit but they burn a little gain on a tone control. http://www.valvejunior.com/img/misc/ValveJunior/kalamazoo.jpg CAF Link to comment Share on other sites More sharing options...
lution Posted May 16, 2006 Share Posted May 16, 2006 hi, forum noob here. I'm really interested in performing the tone mod on my Valve Jr Head. This is installing a 50-100pf cap in the empty C3 spot. Can someone go into this in detail for me? I'm very good at soldering, but haven't ever installed a capacitor before and need some help in detail. I can pick up one of these caps at Radioshack? thanks for all your help. -Lution Link to comment Share on other sites More sharing options...
Ricochet Posted May 16, 2006 Share Posted May 16, 2006 It's just a matter of bending the wire leads to fit through the holes in the pads on the lead traces where the cap goes, slipping them through, trimming if necessary, and soldering them in. Don't use too much heat, and it's best to clip a heat sink on the lead you're soldering between the board and the device, to keep heat from traveling up to the cap. A 15-25W iron will work. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
lution Posted May 16, 2006 Share Posted May 16, 2006 Originally posted by Ricochet: It's just a matter of bending the wire leads to fit through the holes in the pads on the lead traces where the cap goes, slipping them through, trimming if necessary, and soldering them in. Don't use too much heat, and it's best to clip a heat sink on the lead you're soldering between the board and the device, to keep heat from traveling up to the cap. A 15-25W iron will work. cool, thanks. I'll give it a go. any idea what voltage rating these little caps should be? Link to comment Share on other sites More sharing options...
Ricochet Posted May 16, 2006 Share Posted May 16, 2006 It'll have very little voltage on it in operation. Maybe 10V or so max. "A cheerful heart is good medicine." Link to comment Share on other sites More sharing options...
lution Posted May 17, 2006 Share Posted May 17, 2006 ok, I'm confused. I opened up my head and could not find the empty slot. C3 is taken by a big black cap (middle left) http://www.members.hpnx.com/lution/IMG_0612.JPG could one of them be JP1 or JP2? http://www.members.hpnx.com/lution/IMG_0613.JPG any help would be appreciated. thanks. Not sure now where to install this cap. -Lution Link to comment Share on other sites More sharing options...
ChewingAluminumFoil Posted May 17, 2006 Author Share Posted May 17, 2006 Appears to not be on yours. http://www.valvejunior.com/img/misc/ValveJunior/vjcloseup.jpg CAF Link to comment Share on other sites More sharing options...
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