Camera PV 2007 » Digital Camera » Champ 3 prong conversion
Champ 3 prong conversion
Question:
I have an old Champ (1963 5F1) that still has a two prong non-polarized plug. As is, the hot goes to the switch and neutral to the fuse. If I hooked a new 3 prong cord the same way plus chassis ground would the chassis not ground out the switch or can I just do that? Also would it be horribly unsafe to just put a two prong polarized plug (I don’t plan on playing out with this just keeping it at home)?
Response:
> I have an old Champ (1963 5F1) that still has a two prong non-polarized > plug. As is, the hot goes to the switch and neutral to the fuse. If I > hooked a new 3 prong cord the same way plus chassis ground would the > chassis not ground out the switch or can I just do that? >Also would it be horribly unsafe to just put a two prong polarized plug (I
don’t plan on playing out with this just keeping it at home)?<< Even so, get it wrong and it will kill you just as dead as if you were using it to gig with I feel sure I won’t be the only one to recommend you get a qualified electrician to do the conversion and fit the grounding properly, and a pro repair guy should be able to modify in such a way that it can be reverted to original status should you want to sell it "in original condition" at some time in the future. Regards – Hide quoted text — Show quoted text –
Response:
>I have an old Champ (1963 5F1) that still has a two prong non-polarized > plug. As is, the hot goes to the switch and neutral to the fuse. If I > hooked a new 3 prong cord the same way plus chassis ground would the > chassis not ground out the switch or can I just do that? Also would it > be horribly unsafe to just put a two prong polarized plug (I don’t plan > on playing out with this just keeping it at home)?
It’s all right here: http://www.rru.com/~meo/Guitar/Amps/Kalamazoo/Mods/safe.html courtesy of Miles O’Neal. If you are handy with a soldering iron, you can do the job. It seems you know one end from another, as you’ve described the existing power supply circuit. Wire this with the fuse on the hot leg. I usually put the green ground wire under a power tranny bolt. Remember to properly discharge the filter caps so you don’t end up dead. This is considered essential to your safety. If you can’t get a free power cord from the IT guys at work, go to Target and get one there (extra cheap and same quality as Home Depot). Hack off the end you don’t need. The molded plug is really the way to go. Do this before you plug it in again. If it has a death cap, it’s also time to clip that fella out of there. Regards, Phil
Response:
> I have an old Champ (1963 5F1) that still has a two prong non-polarized > plug. As is, the hot goes to the switch and neutral to the fuse. If I > hooked a new 3 prong cord the same way plus chassis ground would the > chassis not ground out the switch or can I just do that? Also would it > be horribly unsafe to just put a two prong polarized plug (I don’t plan > on playing out with this just keeping it at home)?
If you’re thinking of replacing the plug, you may as well go ahead and replace the entire AC cord with a 3-prong type. (Keep the old cord for posterity.) Here’s how the cord should be connected: HOT: HOT–>Fuse–>Switch–>Power Transformer HOT lead. NEUTRAL: NEUTRAL–>Power Transformer NEUTRAL lead. GROUND: GROUND bolted and soldered to chassis. (Use lug on PT bolt.) That should keep you alive. Regards, –E
Response:
Phil didn’t explain what a "death cap" is so I will. Amps often used to put a capacitor between the hot and/or neutral side(s) of the line and the chassis ground. The purpose was to filter noise coming in the power cord to ground. With a three prong plug that is properly grounded if one of those caps goes bad and shorts, the voltage is shunted to ground. But if the third wire ground is somehow defective or missing and the cap fails, it can put full voltage on your amp chassis and hence on your guitar! Hence the name "death cap".
Response:
Thanks a lot guys, so I still have a couple of questions– should I now attach the neutral side of the power transformer to the lamp as per the MilesO’Neal website? there’s already a green lead from the PT on the lamp (the other green lead goes to chassis ground along with a red with orange stripe) the original schematic says green goes to all 6.3V filaments so maybe I don’t want to directly attach that to the neutral? Anyway it seems as if should do this: Hot to side lug of fuse (where death cap and PT lead currently are) remove death cap from circuit, jumper to switch, leave PT lead to other side of switch, which leaves the Neutral side of the PT–do I just directly hook this to the neutral wire of the cord? should I do this slightly differently and run hot fuse, fuse to PT, PT to switch, Switch to neutral–this would be the way it’s currently wired, in reverse, minus the death cap, plus chassis ground.
Response:
thanks for the reply, yeah I think maybe that death had gone bad because the thing was always hot either way the plug was in the socket.
Response:
>NEUTRAL: NEUTRAL–>Power Transformer NEUTRAL lead
as I asked Phil S., does this hook directly to the PT lead or is there a stop somewhere else? the Miles O’Neal website shows hooking it to lamp lead but I think that’s incorrect with my amp (green lead from PT goes to lamp).
Response:
> Thanks a lot guys, so I still have a couple of questions– should I now > attach the neutral side of the power transformer to the lamp as per the > MilesO’Neal website? there’s already a green lead from the PT on the > lamp (the other green lead goes to chassis ground along with a red with > orange stripe) the original schematic says green goes to all 6.3V > filaments so maybe I don’t want to directly attach that to the neutral? > Anyway it seems as if should do this: Hot to side lug of fuse (where > death cap and PT lead currently are) remove death cap from circuit, > jumper to switch, leave PT lead to other side of switch, which leaves > the Neutral side of the PT–do I just directly hook this to the neutral > wire of the cord? should I do this slightly differently and run hot > fuse, fuse to PT, PT to switch, Switch to neutral–this would be the > way it’s currently wired, in reverse, minus the death cap, plus chassis > ground.
Josh, Let’s see if we can sort this out. First, the power transformer primary doesn’t care which side is hot. It’s got two black leads (or some variation) that send the electricity through the primary coil and direction (left to right or right to left) is irrelevant. If you found the two primary leads, you are past the first step. Assuming you’ve got a standard USA power cord with molded plug, black is hot, white is neutral, and green is ground. "Green is ground" really means redundant neutral. It is best to place the fuse on the hot leg between the wall recepticle and the power tranny. Any excessive current draw will blow the fuse and shut down the amp. Like this: Black power cord wire > fuse > switch > primary on transformer. You may need to rearrange the switch wiring, but there is a good chance you can leave it in place. Just think about what you are doing and draw yourself a picture if you need to. On the other leg simply connect the white power cord wire to the other primary on transformer. You can use a terminal strip, or simply splice, solder, and cover with heatshrink. The green wire gets a lug put on it. I feed the wire into the lug terminal and solder it in place. Get the kind of lug that is an open circle, not the U shaped ones. Put the lug under a bolt that holds the power transformer. (The U shaped lug and slip out of place.) If the bulb is on the 6.3V filament circuit, it is not under consideration for this conversation. If the bulb is on the 115v primary circuit. put the bulb between the switch and the power tranny. If your switch is a mutli position switch, for simplicity, only use it like a SPST switch and wire it so that it is On or Off. In all other positions, it is Off or nothing connected. If you want, you can wire it so that either On position is on. Just parallel the connection, but make sure the switch acts as a make or break and that it isn’t on all the time! Phil
Response:
thanks a lot, that’s what I thought needed to happen, the green wires I was referring are from the PT not the ground from the new cable (which I was planning on soldering to the lug where the death cap is currently grounded) one side is the 6.3V to the lamp and then to the filaments the other is grounded to the chassis. I do realize the PT leads are non-directional, I just worded it poorly when I said neutral side I meant because the other would already be hooked to the hot–I’ll figure how to talk about these things without sounding like an idiot eventually. I’ll try this tonight and see if it blows up 
josh
Response:
> >NEUTRAL: NEUTRAL–>Power Transformer NEUTRAL lead > as I asked Phil S., does this hook directly to the PT lead
Yes. > or is there a stop somewhere else?
There is no other stop in between. > the Miles O’Neal website shows hooking it to > lamp lead but I think that’s incorrect with my amp (green lead from PT > goes to lamp).
You’re right. Ignore Miles’ diagram. It doesn’t apply to your amp. (Not the part with the neutral wire going to the lamp, anyway.) Make sure you’ve got a good strain relief on the power cord so that it won’t budge if tugged upon. –E
Response:
> >NEUTRAL: NEUTRAL–>Power Transformer NEUTRAL lead > as I asked Phil S., does this hook directly to the PT lead or is there > a stop somewhere else? the Miles O’Neal website shows hooking it to > lamp lead but I think that’s incorrect with my amp (green lead from PT > goes to lamp).
Another of the many threads on this topic: http://groups.google.com/group/alt.guitar.amps/browse_frm/thread/a681… –E
Response:
> thanks a lot, that’s what I thought needed to happen, the green wires I > was referring are from the PT not the ground from the new cable (which > I was planning on soldering to the lug where the death cap is currently > grounded) one side is the 6.3V to the lamp and then to the filaments > the other is grounded to the chassis. I do realize the PT leads are > non-directional, I just worded it poorly when I said neutral side I > meant because the other would already be hooked to the hot–I’ll figure > how to talk about these things without sounding like an idiot > eventually. I’ll try this tonight and see if it blows up > josh
The green secondary wires are typically for the 6.3v filament string. The lamp is on that string, so just leave all of that the way it is. If the former death cap ground is to the chassis and there is nothing else attached (actually nothing at all now that you clipped the death cap) it is probably OK for the power supply ground wire. You indicate the 6.3V string is involved, in which case, this is not an appropriate location for the A/C power supply ground. It is probably easiest to put it under the tranny bolt. This ground should not share the ground point with any of the amplifier ground scheme. It should be totally isolated. BTW, I didn’t mean to imply that you were "sounding like an idiot". Everyone starts out somewhere and you are making yourself reasonable clear. Regards, Phil
Response:
>If the former death cap ground is to the chassis and there is nothing else >attached (actually nothing at all now that you clipped the death cap) it is >probably OK for the power supply ground wire. You indicate the 6.3V string >is involved, in which case, this is not an appropriate location for the A/C >power supply ground. It is probably easiest to put it under the tranny >bolt. This ground should not share the ground point with any of the >amplifier ground scheme. It should be totally isolated.
The death cap is located on a lug which happens to be on one of the bolts for the transformer, which sounds perfect except there is nothing isolating that bolt from the chassis (or will that be okay?) >BTW, I didn’t mean to imply that you were "sounding like an idiot". >Everyone starts out somewhere and you are making yourself reasonable clear.
No worries, I really appreciate your help. …and if I can take advantage of your help even more I have another question–what connects the turrets? is there a permanent wire like a trace on a PC board, or if I solder a new cap in do I need to make sure that whatever that connector is doesn’t move. One of the big caps (actually the biggest cap that filters the power supply) is wired to the ground wire (the one that comes from the board and connects the caps in parrallel) directly instead of the turret that connects it to the next cap, I know its ending up in the same place in the circuit but it looks really sloppy. I’m hesitant to fix it though because I’m afraid if I melt the solder I’ll lose whatever it is that connects those two points. thanks, josh
Response:
– Hide quoted text — Show quoted text ->If the former death cap ground is to the chassis and there is nothing >else >attached (actually nothing at all now that you clipped the death cap) it >is >probably OK for the power supply ground wire. You indicate the 6.3V >string >is involved, in which case, this is not an appropriate location for the >A/C >power supply ground. It is probably easiest to put it under the tranny >bolt. This ground should not share the ground point with any of the >amplifier ground scheme. It should be totally isolated. > The death cap is located on a lug which happens to be on one of the > bolts for the transformer, which sounds perfect except there is nothing > isolating that bolt from the chassis (or will that be okay?)
I meant isolated from other grounds. The power circuit and the amplifier circuit shouldn’t mix. That bolt sounds like the right place. <bit o’ snip> > …and if I can take advantage of your help even more I have another > question–what connects the turrets? is there a permanent wire like a > trace on a PC board, or if I solder a new cap in do I need to make sure > that whatever that connector is doesn’t move. One of the big caps > (actually the biggest cap that filters the power supply) is wired to > the ground wire (the one that comes from the board and connects the > caps in parrallel) directly instead of the turret that connects it to > the next cap, I know its ending up in the same place in the circuit but > it looks really sloppy. I’m hesitant to fix it though because I’m > afraid if I melt the solder I’ll lose whatever it is that connects > those two points. > thanks, josh
Aha! U are getting curious! A turret or eyelet board is just a fixture that makes it easy to organize and hang components, mostly hookup wire, caps and resistors. If your Champ is a real Champ built back in the day (not some modern clone), it probably has an eyelet board Each eyelet or turret is insulated from all the others (the board itself is non conductive) unless you connect them somehow, by bridging them with wire, a resistor, or a cap. Components are first physically tied to the eyelet and then soldered to keep the tie point in place. Sometimes, there are wires run under the board that you can’t see. That big filter cap is grounded where it is for a reason. I think I’d need a picture to be sure what you are talking about (OK to send email, my address is real if you remove the appropriate part), but I wouldn’t go poking around trying to improve a tested design. For an amp, laying out the ground scheme is almost as much art as it is science. Each stage of the amp carries it’s own ground potential, and it is probable that each of those caps supplies B+ (high voltage) to a different part of the amp. There is a kind of "order" to the design that may not be obvious, but each succeeding amplification stage should have it’s ground located progressively closer to the power supply. (I think I didn’t say this very well, but trust me on this, there is a method being employed here that will be disrupted when you relocate the ground point, unless someone else has already messed with it.) You might want to have a look at the schematic and the layout diagram for a Champ. This is an amp with relatively few parts. A worthwhile exercise is to identify on the layout diagram all of the components on the schematic. This is a paper and pencil exercise. Then see if your amp follows the layout diagram. What you need, download from http://www.schematicheaven.com . Finally, if you are sticking anything conductive into the chassis (tools, fingers, even a pencil) it is imperative that you properly discharge the electrolytic caps. They retain enough charge to harm or kill you long after you unplug the amp. Read up at http://aga.rru.com on safety. Phil
Response:
It Worked!! it’s now rewired, quiet and doesn’t shock me! my local electronics store even has the proper strain relief for $0.25 so no grommets and wire ties. Now if I can just figure out where the funny sounds are coming from this amp will be sweet, any idea what would cause a funny electronic sound lower (in pitch unfortunately, not volume) than the note I’m playing? it’s wierd, like a really desirable guitar sound with all this fuzzy crap all around it. It is an original that I paid $28 for years ago and never really was able to use. I don’t have a digital camera unfortunately so I can’t send a picture, but I’m going to try and draw on layout to show you what I mean and send it to you, I don’t think I can possibly describe what it looks like accurately.
Response:
> It Worked!! it’s now rewired, quiet and doesn’t shock me! my local > electronics store even has the proper strain relief for $0.25 so no > grommets and wire ties. Now if I can just figure out where the funny > sounds are coming from this amp will be sweet, any idea what would > cause a funny electronic sound lower (in pitch unfortunately, not > volume) than the note I’m playing? it’s wierd, like a really desirable > guitar sound with all this fuzzy crap all around it. It is an original > that I paid $28 for years ago and never really was able to use. I don’t > have a digital camera unfortunately so I can’t send a picture, but I’m > going to try and draw on layout to show you what I mean and send it to > you, I don’t think I can possibly describe what it looks like > accurately.
Josh, I’m glad this worked out! Try to describe the "new" problem just a little more. Is the pitch (frequency) of the sound constant, or does it vary with the note you play? If it varies, is it always the same relative relationship to the note played (ghost note)? If it is constant, is it about the same pitch as a low A or B flat (open A string)? Or an octave above that? (60 Hz or 120 Hz) About the fuzz, does it vary any or is it always the same? I’m thinking you’ve got more than one problem and that this old amp just needs a little routine maintenance to be in top shape. We need to figure out the problems. Without experience and tools this could be a challenge. Have you got a DMM and do you know how to use one? Phil
Response:
After further consideration (and letting the amp warm up, the initial test was at 3:30 AM and very quiet and very quick so the tubes weren’t hot and the noise seemed even worse) I think at least part of the problem is the speaker but I’ll find out directly if that’s the case when I rig it up through some different speakers. I’ll get back to you with more info, check your inbox. josh
Response:
Tried it through two Celestion 90 watt 12s, works perfectly for the first time in the ten years I’ve had it, neglected to mention that while I was in there last night I replaced the last two electrolytic capacitors ( the power stage ones I replaced when I first got it, but I knew even less then which is why I was worried about the ground because I couldn’t remember if I did it or someone before me did but it works so I’m guessing it was someone before me), so it’s all good now except for a replacement speaker which are sale from Weber at the moment. It’s amazing how much sound that little amp can move when hooked up to the twelves. josh
Response:
Well said, Phil! The only thing I would add is that the hot lead should go to the end terminal on the fuse, not the side terminal. That makes it much more difficult for someone to accidentally get zapped if they touch the metal part of the cap while replacing a fuse.
Response:
> Tried it through two Celestion 90 watt 12s, works perfectly for the > first time in the ten years I’ve had it, neglected to mention that > while I was in there last night I replaced the last two electrolytic > capacitors ( the power stage ones I replaced when I first got it, but I > knew even less then which is why I was worried about the ground because > I couldn’t remember if I did it or someone before me did but it works > so I’m guessing it was someone before me), so it’s all good now except > for a replacement speaker which are sale from Weber at the moment. It’s > amazing how much sound that little amp can move when hooked up to the > twelves. > josh
Nice work, Josh. Enjoy! Phil
Response:
josh schrieb: > It Worked!! it’s now rewired, quiet and doesn’t shock me! my local > electronics store even has the proper strain relief for $0.25 so no > grommets and wire ties. Now if I can just figure out where the funny > sounds are coming from this amp will be sweet, any idea what would > cause a funny electronic sound lower (in pitch unfortunately, not > volume) than the note I’m playing?
Hi Josh, "subharmonics" normally indicate a problem with the filters; the line frequency modulates the signal. Somewhere you wrote that the first filters have already been replaced; correct values? solder connections intact? wiring ok? regards Jochen SNIP