Jupiter Jukebox Amp

[Paleo Pete]

Just had a project dropped in my lap, need some minor info for now. Jupiter Jukebox, I can't find a model number anywhere, only marking found so far is A04287 stamped on the amp chassis. Not a big issue for now, I'm trying to get caps for it, don't want to even plug it in till the 50 year old caps are replaced.

Thing is, I don't know what type, I'm not familiar with parts as old as I am. The electrolytics are not an issue, those are easy. If I can get a picture to work, I forgot how I did it before, I'm not sure what I need to replace a couple of these.



These, (red arrows) are 0.1uF, I'm guessing that's 630V, not sure what type, but I'm thinking orange drops. (don't know the proper name for those, that's what I've always seen them called. )

Then there's these. 4700pF (if I read it right that's pF not uF, so pico farads) and one is 22000 pF. Voltage is marked. What type here? I'm thinking orange drops would do here too but don't know. Without being able to ID the thing it's going to be tricky but I just spent 20 minutes inside it with a flashlight, not a mark anywhere...



These are really old, so I don't know what type interchanges. Filter caps are can type, I'll probably put in electrolytic replacements same as I did with my Fender Champ, I doubt if I can find new or reliable can caps at all. Not a problem there, 50uF 500V two per can.

At the moment I don't know if tube replacements will be needed, two 7189 and three 12ax7a so that shouldn't be a problem, if I remember correctly 7189 is a EL84 substitute, I think I already have 2 or 3.

Thanks for the help,

[Enzo]

Orange Drop is a brand, the caps are film type.

Your red arrow ones look like nice caps, are you sure they are leaky? If not, I'd sure leave them.

The others probably are in picofarads. Remember that a 22000pf is the same as a 0.022uf. But again, are those leaky?

[Paleo Pete]

Don't know if they are leaky, actually not sure how to find out, just wanted to do a full cap job before trying to plug in this thing. It has records in it from late 50's, Jerry Lee Lewis on Sun records, Bobby Vee, people and record labels I've never heard of...if it's built while I was in diapers, I want a cap job done...

Anyway I thought replace everything except maybe the ceramic disks, and those if I have to. Electrolytics are no problem, already found all of those, will have to replace a 64uF with a 68, otherwise I've already found exact replacements. Will also be checking solder joints and resistors along the way, have most of the tubes if needed.

The one thing that drives me nuts is not being able to make sense of a schematic...I envy the hell out of you guys who can, but if you showed me a schematic of a flashlight I couldn't tell you what it is. Board layout is fine, and I can read the symbols, just can't tell you which 470 ohm resistor on the schematic it is when I look into the amp. Drives me nuts...and I've tried for 20 years...

So far I haven't been able to ID this thing either, nothing stamped, written or printed anywhere.

Thanks for the answers, I understand your concern, just thought it best to do a full cap job. I plugged in my Super Reverb once, found it worked, started replacing caps...I don't want an inexpensive part to fry something. It may be shotgunning, but I do the same with a used car. Plugs and wires, points (if it has them), brakes, bearings, shocks...then I can drive it.

[52 Bill]

None of those parts look that old to me. The brownish green ones are the same "mustard" caps that were used in Marshalls in the '60s and '70s.

I'd start by replacing the main filters and then power it up to see if the other caps are bad or not. Those caps usually go bad by either shorting (beacoming leaky) or going open (losing value). If you have a cap meter you can measure their values and you can use your voltmeter to measure if they are leaking voltage.

[Enzo]

Your electrolytics probably are dried out. The film caps or possible paper caps are used as coupling caps between stages. You tell they are leaky by determining if any DC voltage is coming through them. They should block DC.


SOmetimes I find one or two leaky ones in a jukebox amp, and if do, then I replace them all. But if I find them working, I leave them.


Which 470 ohm? Look at what it is wired to. If one end is connected to pin 4 of a 6V6 socket (Yes, I know you amp has no 6V6, this is just an example.) Then look at the 6V6 on the drawing and the resistor on pin 4 ought to be a 470, and voila, you found it.

[Paleo Pete]

Thanks guys.

Enzo - I understood that was an example, same as mine, it just never did click for me. Don't know what it is, and I appreciate your trying. It irritates me no end, especially considering all the other things I can do. IQ around 140-150, machinist, musician, carpenter, mechanic (rebuilt the engine in my Jeep), did ceramics for years, built and repaired computers for a living for 12 years or so and electronics just stumps me...some things I can find, just the way you described, even thought I don't have a clue what I'm looking at. If only one 470 ohm, to use the same example, is connected to a 25uF cap, OK that has to be it. That's the only way I've ever been able to look at a schematic and actually find the part...and the schematic still doesn't give me half a clue what the circuit is actually doing. Like I said I probably couldn't tell you if it was a flashlight or not...

Anyway thanks for the help, filter caps are definitely on the list, going to be looking them up in a few minutes. Oops...no I'm not, forgot my parts list...I know they're 50uF x 2 can caps, can't remember voltage but it should be at least 350, that was the lowest of them. I'm probably going to go for 500V but will have to look at the list before doing anything. The electrolytics are the ones I'm most concerned about, those are definitely dry after 50 years or so...only about 6 or 7 in it, the rest are the ones I asked about here.

Bill - This thing is old, it has records in it I've never even heard of...all 50's stuff, nothing in it newer than sometime around 1960. I need to see if I can find some dates on one of the pots, it only has a couple, or transformers maybe. It's clean as can be because the amp is in a square bowl shaped metal housing that bolts to the bottom and has everything but the tubes and transformer completely covered, no dust can get inside. I like the design, keeps it in good shape with no dust and crud. Can caps are on top of it, some dust on top of those, and on top of the tubes, that's about it. Everything inside will fool you it's clean as can be. I'd like it if the thing was laid out on a board the way Fender amps are made, but it's not, it's all a cluster of parts, wires and contact strips.

[Enzo]

It isn't about being smart or stupid, it is a matter of how you look at things and how you understand your world. MY sister is a very good artist, she has stuff hanging in galleries and does shows. People buy her stuff. Growing up, I could never draw, still can't. She'd draw a horse, it was magnificent, looked just like a horse, by god. I draw a horse, and there are ears, check, nostrils, check, a mane, check, all the parts, but looking at the whole thing you see some sort of distorted I don't know what. When she draws a line drawing, she obviously "sees" the picture as she draws, because it never involves drawing over something else to put an arm on a figure or whatever. I have no such vision.

She on the other hand has no clue about electronics.

Electronics is an abstract, you cannot see electric current. You can only see evidence of it. Sure, music is abstract too. But to "get" electronic circuits, you have to have certain concepts internalized. If they don;t click for you, then they don't. I was always a whiz at diffy-Q, but not so much at calculus. Classmates would look at me funny and say, "well calculus is simple, it is just the ..." No, it is not simple, or I'd get it. I used to work in a large music store. I ran the electronic repair shop, but elsewhere in the building was a large department of band/orchestra repair guys. Guys rebuilding violins and cellos all day, other guys bumping out bent trombones or repadding clarinets. I used to think, we are all instrument repairmen, but geez how different what I do is from what they do. They shape metal and wood, I don;t have that skill. On the other hand, electronic repair is about solving puzzles. A cracked guitar body requires a lot of skill to repair, but I doubt it is a mystery to the luthier. Though I am good at solder work, I don;t think it takes a lot of skill to solder a part into an amp, but solving the mystery of which part to replace is the challenge. Of course the store needed ALL those abilities.

So if this part of the world escapes you, well, you do all those other things. The only way to get electronics is to actually learn it. it may never set well on you, but to give it the chance, you need to start at the start. Just picking it up as you go may never work.

[Paleo Pete]

Some good points there. I do know some of the basics, I know what resistors and capacitors do, I know basically how electricity works, the difference between AC and DC, I can do things like wire a light switch or wall outlet correctly, but as in your analogy, I just don't "see" it. Similar to the carpenter work I did. My uncle and a friend could "see" a job like that. I can't. I can do you some of the nicest looking trim work around, I can actually build the entire house, and do it correctly - sheetrock, paneling, framing, roofing, all of it - but tell me you need to rebuild a bathroom and I can't just see it, I have to take measurements and draw it out to have an idea what I need to do. Main problem is the schematic is just Greek to me...I can follow a board layout, no problem but show me a schematic and you might as well show me the Gettysburg Address in Chinese...It's kind of like a friend I had who taught me some of this. I had a cordless drill charger that stopped working, he opened it up and took a look. Pointed out a part, told me it was a rectifier, go get another one with that number and he'd bet it would work again. He was right and he never touched a meter...just looked inside. I have no idea how he did that, without even testing anything, and I'll certainly never be able to do it, but if I keep at it I might just be able to get this jukebox working even if I have to bug you guys a bit...I don't expect to have tons of stuff, I suspect this is probably a case of bad tubes. Only reason I'm replacing caps is age. But I need to know what type caps to use, parts as old as I am I've never dealt with.

I may never completely understand it, but I won't stop trying either. I'll be looking up and ordering some of the caps this evening, starting with the electrolytics, and will probably be digging into it with a meter in a few days to see if any resistors are out of tolerance. I'm betting some are, but no way to know until I start checking. Fortunately it's not a very complicated amp, pair of 7189 tubes, pretty small, so it won't be a major project to check all the solder joints and components I can test.

I appreciate the help and will try not to bother you unless it's really necessary.

[Enzo]

The schematic shows the electrical relationship between parts - which is another way of saying it shows the circuit. The layout shows the physical relationship between parts.

The schematic is not intended to resemble the physical amplifier. If a resistor has a line over to another resistor on the drawing, and a branch to a capacitor, it does not imply they are spaced apart, it implies only that each of those three parts are connected together. Two could be at one terminal with as wire to the third, or all three could be at the same terminal, or the three parts could be in different places, but with wires connecting them. Not only that, on a schematic, you might see a line drawn across the page, and a resistor branching off every inch. That only implies all resistors involved are connected to that point in the circuit. It does not imply that the resistors are somehow connected in the order they appear on the page.

Think of it like one of those company organization charts with the CEO at the top, then lines down to two vice presidents, and from each of them, lines branching to various managers, etc. I(t shows the connections, but it does not imply the physical space between the individuals. The vice presidents may not be sitting side by side, and probably not on a different floor of the building to be below.

[Paleo Pete]

The schematic is not intended to resemble the physical amplifier. If a resistor has a line over to another resistor on the drawing, and a branch to a capacitor, it does not imply they are spaced apart, it implies only that each of those three parts are connected together. Two could be at one terminal with as wire to the third, or all three could be at the same terminal, or the three parts could be in different places, but with wires connecting them. Not only that, on a schematic, you might see a line drawn across the page, and a resistor branching off every inch. That only implies all resistors involved are connected to that point in the circuit. It does not imply that the resistors are somehow connected in the order they appear on the page.

I've seen that from looking at schematics then looking inside. What the schematic shows is nothing like what it looks like inside. But I also understand what you're trying to get across, it shows the electronic relationship, not the physical. Got that. I still don't really understand it, but I know that's what it shows me.

Maybe I'm not explaining myself well enough...what I can't quite get is...if you look at a schematic, say my Fender Champ, you can determine where the preamp section is, where the tone section is and so forth. Knowing a bit about how knowledgeable you in particular are, you might be able to do a lot of troubleshooting just by knowing what the circuit itself looks like. But if I look at the same Champ schematic, (I did by the way, it took me a while but I sat there and found everything on it in the amp itself) I don't have the slightest clue how to tell which caps are there to be the tone filters or which resistors might tweak the preamp gain. Most of you guys can probably look at it and say "that one". I know it's a resistor, but that's about as far as I can get...No I don't want to tweak or modify it. I like it as is, and by the way it's still working perfect after you guys helped me get through the arcing problem. And sounds fabulous. I use it at band practice every weekend.

Like I said it's really irritating, it seems I should be able to get a handle on this. I can do anything else I've ever tried...I don't give up easy though, I guess that's my parents' fault, they told me I could do anything...I always have...I need to find my box of books, I have a radio course from the WWII days, started a while back but had to pack everything and move to Texas, and like a dummy I didn't keep them out where they could be easily found again...something like 20 books, all tube stuff, I had started on the first couple but never got far before I had to move. I've done some digging in a couple of other books too, and gotten some basics, but that damn schematic thing has always stumped me. But so far it looks like the book box is buried under and behind a pile of other boxes 6 feet high...that may be where my tube tester is too, it needs a rebuild...

Anyway thanks a lot, that's one more explanation that helps some, I seem to be pretty dense in this field, and I don't learn as quick and easy as I did 40 years ago either, but I'm slowly getting it bit by bit.

Anyway back to this amp. I've ordered some of the caps, all the electrolytics except the filters, still looking for the best price I can find. I wish I knew just how much voltage this thing is running, it has 50uF 500V now x 4 in 2 cans, and I'm having a hard time finding much over 450V. A few but they seem to be pretty proud of them. I can't look up a schematic, because I can't even ID the damn thing. Nothing marked anywhere. It says Jupiter on back, that's it. I can't even find out what model jukebox it is, much less what amp it has inside...that may turn out to be a real problem...