I just bought my first tube amp, an early 70's Garnet Deputy 50w combo. It has a 1 Hi and Low input and a 2 Hi and Low input, plus one input that joins all four into one for Marshall distortion.
When I bought it, it was a little worse for wear. input 1 was a little quiet, and input 2 didn't work. I know nothing about tube amps, but I decided to open it, and I found a loose wire. I resoldered it, and input 2 worked. Then I realized that input 1 ran at about half the volume of input 2, and I have no idea why it would do that. Can anyone help me?
Also, tubes are still original, it that helps you out at all. (2 6L6, 2 12AX7, and 1 12AU7)
When I bought it, it was a little worse for wear. input 1 was a little quiet, and input 2 didn't work. I know nothing about tube amps, but I decided to open it, and I found a loose wire. I resoldered it, and input 2 worked. Then I realized that input 1 ran at about half the volume of input 2, and I have no idea why it would do that. Can anyone help me?
Also, tubes are still original, it that helps you out at all. (2 6L6, 2 12AX7, and 1 12AU7)
Even though guitar amplifiers are designed for guitar pic-ups and such, inputs 1 & 2 are naturally going to be different levels. My Fender 5E3 has multiple inputs labeled 1, 2, 3, & 4. 1 & 2 are labled "low", and 3 & 4 are labled "high". Low inputs are for guitars and guitar pick-ups, and high inputs are for something like a microphones.
People tend to focus on the tubes as any source of problems, partly because they come in sockets and are easily replaceable, and partly because fifties televisions burnt up so many. After forty years, it is much more likely that the electrolytic capacitors in the amp are dried up and blocking or shorting out the bass depending on configuration. These all need to be changed just because of the passage of time. They contain water, which leaks out through the rubber seal around the leads. Electrolytics can store voltage with the power off, so before touching any metal inside you need to read tube high voltage safety thread at the top of tube forum. Changing 2 electrolytic capacitors in my 1968 organ doubled the volume. 4 more doubled it again and made the attack feature work. 64 more made it sound like new with good treble and bass. A guitar amp will have fewer electrolytic capacitors. These look like aluminum cans with a plus on one lead or a minus near the other. They have a cardboard sleeve, or plastic, or are tall cans with circles moons and squares indicating different sections. They come in whole mf after 1960. mf stood for microfarad until about 1980, and has been changed to "uf" after 1980 by some illiterate academic who couldn't tell his mu's from his u's. mf offended the fans of the metric system that though it might stand for millifarad, which capacitors would be the size of D-cell flashlights or hand lanterns if they existed at all. Caps have dates like YYWW where YY is year. Any electrolytic caps after 95 might be totally okay, unless they were cheap 500 hour or less versions.
The one tube sure to go based on high hours, not years of life, is the rectifier tube. Some guitar amps "overdrive" some tubes for second harmonic distortion, and that tends to burn them up, cutting output current. This shortening of life is also based more on hours of use ( or abuse, as we organ people call it). You may find more experts on which tube in your circuit is the overdrive, on the musical instrument forum. The 6l6's have a life of maybe 3000 hours, and a pro might have worn them down to a lower power state. All the tubes you listed are amplifying tubes, none are rectifiers. Either you have another tube, or you have solid state rectifiers, which might last forever if they didn't do any of 6 cheesy workarounds that designers did in the late sixties to save money. One SS rectifier in my 1975 tractor battery charger shorted out last year due to a stupidly cheap design and burned out a $100 transformer. You measure worn out power tubes by checking the current in the cathode resistor idle, to make sure it is high enough. 100 ma is about enough for 6CA7, I think 6L6 is a more high power tube with more current, but I am no expert on it. Tube datasheets are at triodeelectronics.com.
However, after forty years I would concentrate on the capacitors before worrying much about tubes. Electrolytic capacitors near the fransformer can short out, burning the transformer out, or even boil and explode, drenching everything in conductive borax water and aluminum foil shreds.
The one tube sure to go based on high hours, not years of life, is the rectifier tube. Some guitar amps "overdrive" some tubes for second harmonic distortion, and that tends to burn them up, cutting output current. This shortening of life is also based more on hours of use ( or abuse, as we organ people call it). You may find more experts on which tube in your circuit is the overdrive, on the musical instrument forum. The 6l6's have a life of maybe 3000 hours, and a pro might have worn them down to a lower power state. All the tubes you listed are amplifying tubes, none are rectifiers. Either you have another tube, or you have solid state rectifiers, which might last forever if they didn't do any of 6 cheesy workarounds that designers did in the late sixties to save money. One SS rectifier in my 1975 tractor battery charger shorted out last year due to a stupidly cheap design and burned out a $100 transformer. You measure worn out power tubes by checking the current in the cathode resistor idle, to make sure it is high enough. 100 ma is about enough for 6CA7, I think 6L6 is a more high power tube with more current, but I am no expert on it. Tube datasheets are at triodeelectronics.com.
However, after forty years I would concentrate on the capacitors before worrying much about tubes. Electrolytic capacitors near the fransformer can short out, burning the transformer out, or even boil and explode, drenching everything in conductive borax water and aluminum foil shreds.
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Millifarad would actually be mF, not mf, and they are quite common nowadays although usually marked in thousands of microfarads. Look in any solid-state amp.
Most academics know the difference between u and mu, but not all fonts have Greek so u is often used instead of mu. There is little scope for confusion, as u is not an SI unit multiple.
For some reason the US was slow to adopt the SI system, so what everyone else calls pF (picofarads) they sometimes called mmf (micro-microfarads).
Most academics know the difference between u and mu, but not all fonts have Greek so u is often used instead of mu. There is little scope for confusion, as u is not an SI unit multiple.
For some reason the US was slow to adopt the SI system, so what everyone else calls pF (picofarads) they sometimes called mmf (micro-microfarads).
The point is, caps that could be measured in millifarads are huge enough they have a lot of room to print the 000's of microfarads. No confusion about the m. I don't know why they went to uf, but you can't buy mf caps online except at antique radio stores, or if you do you might get something 1000 times too big.
I view the metric system as a way for manufactures to make sure you buy every nut and bolt from the dealer. There are German metric bolts, different Itaiian metric bolts, different Japanese metric bolts. If you want to rethread a Mercedes oil pan stud, you have to drive to a different state or 200 km to the state capitol to get a die; nobody in 2 counties stocks German metric dies. Nobody in the USA has bolts to put a scoop on my Fiat tractor. (it said it was an Oliver, made in Chicago previously) When I was in FRGermany, I couln't buy anything like DOT 3 brake fluid, which is in every grocery store and mini-mart in the USA. There was Mercedes brake fluid, and Porche brake fluid, and Audi brake fluid where our army truck ran out of brakes, but no generic brake fluid. No wonder everybody in Europe rides the train or bus. Their cars are useless after 10 years, nobody can afford to fix them so they flog them off to Africa or Palestine, where I see them on BBC news.
I view the metric system as a way for manufactures to make sure you buy every nut and bolt from the dealer. There are German metric bolts, different Itaiian metric bolts, different Japanese metric bolts. If you want to rethread a Mercedes oil pan stud, you have to drive to a different state or 200 km to the state capitol to get a die; nobody in 2 counties stocks German metric dies. Nobody in the USA has bolts to put a scoop on my Fiat tractor. (it said it was an Oliver, made in Chicago previously) When I was in FRGermany, I couln't buy anything like DOT 3 brake fluid, which is in every grocery store and mini-mart in the USA. There was Mercedes brake fluid, and Porche brake fluid, and Audi brake fluid where our army truck ran out of brakes, but no generic brake fluid. No wonder everybody in Europe rides the train or bus. Their cars are useless after 10 years, nobody can afford to fix them so they flog them off to Africa or Palestine, where I see them on BBC news.
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Grab a copy of this:
http://www.webphix.com/schematic heaven/www.schematicheaven.com/bargainbin/garnet_g100_deputy.pdf
This is the schematic for the 100 Watt version but all of the preamp section (page 1 of that document) and most of the power amp section are the same.
Cheers,
Ian
http://www.webphix.com/schematic heaven/www.schematicheaven.com/bargainbin/garnet_g100_deputy.pdf
This is the schematic for the 100 Watt version but all of the preamp section (page 1 of that document) and most of the power amp section are the same.
Cheers,
Ian
I looked at the two can caps in it, and I didn't see any bubbling near the seals, but they might very well be dying. I also noticed, when I play a low note at relatively high volumes, I get a harsh loud BUZZ sound, that lasts only as long as the note I play. I told my father that I would like to replace some of the caps in it, and he told me that It's one of the dumbest things he has heard me say, and that there is no way in hell I could do it. The closest old tube repair guy to me lives over 400km away. I don't think I really have a choice.
Also, the amp is a Deputy G100B, the bass model I believe. It should still have a very similar schematic. I did my best following that schematic that I printed out, and from what I can tell, it's very close.
Also, the amp is a Deputy G100B, the bass model I believe. It should still have a very similar schematic. I did my best following that schematic that I printed out, and from what I can tell, it's very close.
It really depends how big the caps are as to how much trouble you need to take. Have a quick look here for some tips on general capacitor discharge techniques. Your Dad seems to be speaking out of his (auto-censor won't let me put that, so I'll say 'posterior' instead). If you can hold a soldering iron, know which way the capacitors go in and have some new ones of the right values ready it shouldn't take you long at all! If something doesn't work then you can be almost certain it's your soldering to blame as it's very unlikely one of the new capacitors will be faulty. Take some digital photographs if you're stripping a lot out at a time so you know where the new ones go if you forget...
And read that "Tube Learning for Newbies" as has already been mentioned. If you're used to poking around in low-voltage circuits then a valve one could hold some nasty surprises. It's not a good idea to poke things with your fingers to see if they're connected, for example!
It should be a project that is relatively quick 'n' easy with a massive difference at the end - even if the capacitors don't look awful they're pretty old.
Good luck!
And read that "Tube Learning for Newbies" as has already been mentioned. If you're used to poking around in low-voltage circuits then a valve one could hold some nasty surprises. It's not a good idea to poke things with your fingers to see if they're connected, for example!
It should be a project that is relatively quick 'n' easy with a massive difference at the end - even if the capacitors don't look awful they're pretty old.
Good luck!
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Always use a resistor to discharge caps.
The old screw driver trick is for amateurs that will damage components and themselves.
A 100K 2-3w resistor is a good value to use.
Too low of resistance and you will get a spark. Too high and it will take a long time to discharge.
Take a insulated test lead with alligator clips at each end and cut it in two.
Solder the resistor in the middle then put heat shrink tubing over the resistor and solder joints.
Clip one end to chassis ground (a bare metal spot on the chassis) and clip the other end to the + end of a cap.
If you clip it to the last filter cap in the supply it will drain all the caps.
Should take a couple minutes.
Always verify that the voltage is below 10v before touching anything inside.
Good idea to leave the discharge lead attached while working to prevent any charge from building back up.
Remember to remove it before powering up!
Remember that tube amps often use voltages upwards of 450v DC.
Plenty enough to kill you in a split second or certainly enough to throw you across the room and use words not suitable for mixed company.
The old screw driver trick is for amateurs that will damage components and themselves.
A 100K 2-3w resistor is a good value to use.
Too low of resistance and you will get a spark. Too high and it will take a long time to discharge.
Take a insulated test lead with alligator clips at each end and cut it in two.
Solder the resistor in the middle then put heat shrink tubing over the resistor and solder joints.
Clip one end to chassis ground (a bare metal spot on the chassis) and clip the other end to the + end of a cap.
If you clip it to the last filter cap in the supply it will drain all the caps.
Should take a couple minutes.
Always verify that the voltage is below 10v before touching anything inside.
Good idea to leave the discharge lead attached while working to prevent any charge from building back up.
Remember to remove it before powering up!
Remember that tube amps often use voltages upwards of 450v DC.
Plenty enough to kill you in a split second or certainly enough to throw you across the room and use words not suitable for mixed company.
I once tossed a 300volt cap that i charged up at my brother. And a kid in school. They didn't know what happened, but got pretty angry when I explained to them what a capacitor is.
So I've decided That I'm going to change the filter caps. There is only two of them;
MFD WV
60 450
20 450
2 350
For 85 celsius OPER
and;
MFD WV
20 450
20 450
20 450
20 450
The second one should be simple to find, but the first one I have no idea what to do with. Any help? I've never ordered any caps before.
So I've decided That I'm going to change the filter caps. There is only two of them;
MFD WV
60 450
20 450
2 350
For 85 celsius OPER
and;
MFD WV
20 450
20 450
20 450
20 450
The second one should be simple to find, but the first one I have no idea what to do with. Any help? I've never ordered any caps before.
It helps to update your personel information to show what continent you are on anyway, if not country or city. In the US, tubesandmore.com and triodeelectronics.com are pretty useful sources of old tube caps. I don't know about europe or the far east. Mouser & farnell both operate there but they are expensive on HV caps and don't carry FP can caps. Don't forget the 10k 5 W resistor for discharging, some 600 V wire, and a little 3/8" heat shrink to enclose it. Save on shipping & get it all on one order. The first can cap could be replaced by a 50-50 @ 450 FP can cap, plus a separate 2 @ 400 axial cap etc mounted on a terminal strip under the deck. Another useful device is a 100 ohm 3 watt resistor (450 V rated minimum) on a terminal strip between the rectifier cathode (if tube ) or line (if solid state) and the first cap. This prevents blowups and allows more cap than the original without too much cold turn on surge current.
You'll need at least a 35 W iron with a chisel tip, not the pointy one they come with, to get those can tabs off. Wear safety glasses, solder splashes. You need some tin/lead rosin core solder, whatever continent you are on.(It is pretty banned in Europe). diagonal cutters, wire strippers, 600 V rated wire about 24 ga, steel pick, needle nose pliers, slip joint pliers for twisting on the can tabs. Write everything down with a sharpy black marker where it goes, or use tape over the wires to label them. If you get electrolytics backwards (- to +) they pop open .
You'll need at least a 35 W iron with a chisel tip, not the pointy one they come with, to get those can tabs off. Wear safety glasses, solder splashes. You need some tin/lead rosin core solder, whatever continent you are on.(It is pretty banned in Europe). diagonal cutters, wire strippers, 600 V rated wire about 24 ga, steel pick, needle nose pliers, slip joint pliers for twisting on the can tabs. Write everything down with a sharpy black marker where it goes, or use tape over the wires to label them. If you get electrolytics backwards (- to +) they pop open .
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I live in Saskatchewan, Canada. I understood almost everything you said, minus part of the procedure. (Terminal strip) I guess I have some studying to do now. Also, I've learned more about tubes and amps in 2 hours on here than anywhere else.
Just to give you all an idea of what it is,
Just to give you all an idea of what it is,
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Sorry, I saw Saskatch---- after I posted. tubesandmore.com has got terminal strips, for example part number P-0301H01. It costs $12 to ship UPS across the border I think.I hear US mail/RM is a little cheaper. I don't know any tube suppliers in Canada, but captain-foldback.com is in Quebec and has a lot of parts for tube Hammond organs and tube leslie speakers. He also answers the occasional newbie question. He also does whole repair jobs if you want him to quote it.
I would love you to explain how using different caps can give me the same capacitance as the one that needs to be replaced. I just need to get my mind around the concept, if it's not too much of an issue.
Also, here is a picture of the amp to hopefully give you an idea of what I have going on in there.
Also, here is a picture of the amp to hopefully give you an idea of what I have going on in there.
Good sharp picture.
Actually, it looks as if one section of the 60-20-2 cap at the left is not used. So you just need a 60-20 if that is the two sections used. They don't make that that I know of in a FP can. You can buy single axial caps of 20 pretty cheaply, but 60 is an obsolete number, it would have to be 50 or 68. And 68 would be rare and expensive. I know they make a FP can 50-50@450, I bought one for my organ. However, if you go a lot over in capacitance, you have to put a 100 ohm 3W resistor between the tube rectifier and the first electrolytic cap to keep the rectifier from arcing over at startup surge. I do see solid state rectifiers, they are a little less sensitive but you still have to be careful going over on filter capacitance. However, since the left can cap is totally below the chassis, and there is lots of room there, you could put a couple of terminal strips there and two axial lead caps, which are about $2 each from farnell.com, instead of $35 for FP can caps. You'd have to drill a hole, capturing the metal with a magnet so it doesn't short anything, and put in a #6-32 screw and nut to hold the terminal strip.
Be sure to check your can cap production dates. YYWW where YY is year. The yellow wires look new, and a real pro that might have replaced the transformer would also replace the electrolytic cap that blew it up. That blue thing on the terminal strip at upper right might be another low voltage electrolytic cap, look for a plus on one end, or a minus on the other.
Tuned circuits like bass or treble filters require close tolerance caps, +-20% or +-10%. Look out for that on the blue one. The cans are always +80-20%, filter caps, so you don't have to match those exactly, though if you go more than 40% over you have to do the series resistor thing. You can go up to about 40% over on voltage on filter caps, but if you go more than that the actual capacitance is less than the name on it says at the test voltage.
Actually, it looks as if one section of the 60-20-2 cap at the left is not used. So you just need a 60-20 if that is the two sections used. They don't make that that I know of in a FP can. You can buy single axial caps of 20 pretty cheaply, but 60 is an obsolete number, it would have to be 50 or 68. And 68 would be rare and expensive. I know they make a FP can 50-50@450, I bought one for my organ. However, if you go a lot over in capacitance, you have to put a 100 ohm 3W resistor between the tube rectifier and the first electrolytic cap to keep the rectifier from arcing over at startup surge. I do see solid state rectifiers, they are a little less sensitive but you still have to be careful going over on filter capacitance. However, since the left can cap is totally below the chassis, and there is lots of room there, you could put a couple of terminal strips there and two axial lead caps, which are about $2 each from farnell.com, instead of $35 for FP can caps. You'd have to drill a hole, capturing the metal with a magnet so it doesn't short anything, and put in a #6-32 screw and nut to hold the terminal strip.
Be sure to check your can cap production dates. YYWW where YY is year. The yellow wires look new, and a real pro that might have replaced the transformer would also replace the electrolytic cap that blew it up. That blue thing on the terminal strip at upper right might be another low voltage electrolytic cap, look for a plus on one end, or a minus on the other.
Tuned circuits like bass or treble filters require close tolerance caps, +-20% or +-10%. Look out for that on the blue one. The cans are always +80-20%, filter caps, so you don't have to match those exactly, though if you go more than 40% over you have to do the series resistor thing. You can go up to about 40% over on voltage on filter caps, but if you go more than that the actual capacitance is less than the name on it says at the test voltage.
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I'm sure someone will correct me if I'm wrong, but I have some recollection of Sprague (and maybe others) still making some 60uF capacitors... Maybe it's a European thing? I agree with Indianajo that I've not seen a 60-20 radial before. If you can find a 60, then like he said 20s are common.
I love the internet, and this forum in particular. I've learned a whole lot about transistors and op amps here, and a couple of things about tubes. When you get your caps up to spec, come back and ask about checking how good your tubes are without a tube checker. You need a voltmeter with a 600 Vdc scale and a data sheet is all for the emmision test. But you've learned enough theory for this month; get your hands dirty on caps and come back for more later.
If I used a terminal strip, could I use a 47 uf @500 (for the 60 uf @450) and a 20 uf @500 (for the 20 uf @ 450), and if so, how would I do that? I want to know in simple to follow detail so that I don't mess up and my parents and siblings can't say "I told you so." also, that blue one you mentioned was a 58 @450, and I found a 22 uf one at the first preamp tube.
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