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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#42
Posted to sci.electronics.repair
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Tried to recap a tube receiver, and failed.
On 29 Apr, 06:30, (Derwin) wrote:
In article , says... On Sat, 28 Apr 2007 04:43:11 +0000, Derwin wrote: In article 5HzYh.5314$Dq6.1620@edtnps82, says... "Derwin" wrote in message news:6mzYh.5305$Dq6.3498@edtnps82... I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it on it starts playing music for a few seconds after it warms up, then the music fades out and and hum takes over. I don't really know what I'm doing, and the wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering if the value difference, added up over 8 caps would make a difference? No. That's not what I've read. Are you sure you're not thinking of electrolytics? Other than that, does anyone have any advice based on my description of the unit's behavior? Any comments whatsoever might be helpful.. At this point you need to fault find. Does it work OK with tape or other music input? Perhaps I should have specified that the unit worked fine before I recapped it. It had a bit of a squishy sound so I figured it could use a re-capping but I must've screwed up somehow. But re-capping is pretty straight-forward, and I think I did it right. So now, what could have gone wrong? Switching inputs is not going to help me track down the problem at all. C'mon, I may be a 'self-taught' novice electronics tinkerer, but that is downright stupid - I already said the music plays fine for a few seconds after it warms up then it fades out, so obviously its not a problem of a flakey input.. sheesh. How the hell is anyone on the other end of the internet going to know what the hell you "screwed up somehow"? That's absolutely absurd. Toss the ****er in the trash you idiot. Only a moron like you would do something like that. There's always at least one or two people on each newsgroup with no life who spend all day every day saying stupid things to anyone who happens to post looking for information. I bet you even think you're unique. I've been swatting usenet flies like you for the past 15 years, ever since the internet went commercial and twits like you found out you couldn't be kicked off usenet so you set up camp here in droves... Retards and the socially inept should be smiling and happy, not scowling meanies. Why don't you try riding a public bus while farting and giggling? Seems to cheer up most of the retards in my neighborhood. First you changed caps that had nothing to do with the problem you were trying to solve. Second you ballsed it up 3rd you expect us to tell you whats wrong when you dont even understand the basics, and wont even try some basic checks to narrow things down a bit. 4th you insult one of the few people that actually knows what he's talking about and has consistently given accurate answers so far. You dont have a hope in hell of fixing it. Other than by chance. NT |
#43
Posted to sci.electronics.repair
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Tried to recap a tube receiver, and failed.
On Apr 27, 8:39 pm, (Derwin) wrote:
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it on it starts playing music for a few seconds after it warms up, then the music fades out and and hum takes over. I don't really know what I'm doing, and the wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering if the value difference, added up over 8 caps would make a difference? Other than that, does anyone have any advice based on my description of the unit's behavior? Any comments whatsoever might be helpful.. the squishy sound was due to power supply issues... could have been a cap issue floating around.. u need to take careful measurements of ur power supply a VTVM will not load down the circuits when u look at them.. good luck |
#44
Posted to sci.electronics.repair
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Tried to recap a tube receiver, and failed.
Derwin wrote:
In article , says... Derwin wrote: I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it on it starts playing music for a few seconds after it warms up, then the music fades out and and hum takes over. I don't really know what I'm doing, and the wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering if the value difference, added up over 8 caps would make a difference? Other than that, does anyone have any advice based on my description of the unit's behavior? Any comments whatsoever might be helpful.. Obviously what you did caused the problem. Check for cold solder joints and inadvertent connections via solder flash. If you have enough information (e.g. a detailed log of what you did, or before/after photos), go back and recheck your work. Did it look like spaghetti before you started? YES. Why are you even replying if you obviously have never looked inside an old tube amp? You know not of what you speak. I was probably repairing tube equipment before you were born. And much tube equipment is very un-spaghetti-like. Or maybe we have different ideas of what spaghetti looks like. From your description, it sounds like maybe it's drawing more current now than before, so that the power supply capacitors are no longer adequate. Does it have a rectifier tube in the power supply? probably Is it glowing red? they're all glowing and I tested every tube a few months ago and they were all fine. I no longer have a tube-tester to check again, however. I meant are the PLATES glowing red. Of course the heaters would be glowing. Perhaps you've dramatically changed the bias point in the output stage by some misconnection. All the caps I replaced are connected exactly where they were before I replaced them. What I'm thinking is that the guy who sold it to me, after having 'restored' it from non-working condition wired it up in some jeri-rigged fashion to get it to look like it was working enough to be able to sell it to me. Probably one of the caps was bad and compensating for a bad resistor as someone else mentioned. However, the wiring he added did not contribute to the 'spaghetti' much. Anyone who has ever looked inside any old electronics from before the days of circuit-boards will know what 'spaghetti' wiring looks like. Those who havent, try this: Look at a circuitboard populated with a bunch of components. Look at the traces the circuit makes on the back of the board. Now imagine each one of those traces being replaced with a wire. Now perhaps you will be able to envision the 'spaghetti' wiring that a circuit not build on a PCB will look like.. Anyway now I'm pretty much screwed. I don't own an oscilliscope .... or even know how to spell it. so I will probably just sell off the tubes and toss the chassis. I prefer the sound of solid-state these days anyway, my interest in tube gear was a folly that only lasted a couple years. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#45
Posted to sci.electronics.repair
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Tried to recap a tube receiver, and failed.
"CJT" wrote in message
... Derwin wrote: In article , says... Derwin wrote: I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it on it starts playing music for a few seconds after it warms up, then the music fades out and and hum takes over. I don't really know what I'm doing, and the wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering if the value difference, added up over 8 caps would make a difference? Other than that, does anyone have any advice based on my description of the unit's behavior? Any comments whatsoever might be helpful.. Obviously what you did caused the problem. Check for cold solder joints and inadvertent connections via solder flash. If you have enough information (e.g. a detailed log of what you did, or before/after photos), go back and recheck your work. Did it look like spaghetti before you started? YES. Why are you even replying if you obviously have never looked inside an old tube amp? You know not of what you speak. I was probably repairing tube equipment before you were born. And much tube equipment is very un-spaghetti-like. Or maybe we have different ideas of what spaghetti looks like. From your description, it sounds like maybe it's drawing more current now than before, so that the power supply capacitors are no longer adequate. Does it have a rectifier tube in the power supply? probably Is it glowing red? they're all glowing and I tested every tube a few months ago and they were all fine. I no longer have a tube-tester to check again, however. I meant are the PLATES glowing red. Of course the heaters would be glowing. Perhaps you've dramatically changed the bias point in the output stage by some misconnection. All the caps I replaced are connected exactly where they were before I replaced them. What I'm thinking is that the guy who sold it to me, after having 'restored' it from non-working condition wired it up in some jeri-rigged fashion to get it to look like it was working enough to be able to sell it to me. Probably one of the caps was bad and compensating for a bad resistor as someone else mentioned. However, the wiring he added did not contribute to the 'spaghetti' much. Anyone who has ever looked inside any old electronics from before the days of circuit-boards will know what 'spaghetti' wiring looks like. Those who havent, try this: Look at a circuitboard populated with a bunch of components. Look at the traces the circuit makes on the back of the board. Now imagine each one of those traces being replaced with a wire. Now perhaps you will be able to envision the 'spaghetti' wiring that a circuit not build on a PCB will look like.. Anyway now I'm pretty much screwed. I don't own an oscilliscope ... or even know how to spell it. so I will probably just sell off the tubes and toss the chassis. I prefer the sound of solid-state these days anyway, my interest in tube gear was a folly that only lasted a couple years. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . Even the best of us who've got years of experience can make errors. Unless you were in a shop working side by side with or had access to other techs - "tough dogs" could really cause some wasted time. This forum and many others like it - provides an invaluable asset to all of us for working on things. None of us could know ALL the answers. Some things don't make sense sometimes and aren't always so clear to the eye. I've seen things appear to buck all theory - but - I still found the cause and corrected the issue. You have to keep an open mind when doing this stuff. Unless you can definately say an area/circuit has been isolated as not being at fault - don't rule it out. It is those issues where you must stop - analyze what has been done, all previous and current signs and so on. Any "help" issued - is a plus. Of course - it helps to give a complete and thorough analysis of the problems before you started, all steps taken and so on - as none of us can see your project, have a clue what you've done OR know your experience to know where/how to proceed to help. Are we to give you "basic" electronics knowledge to help OR are you advanced with lots of equipment we can tell you to use, etc.? You said you left out telling us some of the things you've done - which you apparently thought mundane items. Who knows - one of those steps - might have clued one of us in - to your problem! Maybe not ALL of our ideas will help - but only because we do NOT know your exact situation. So - rather than shoot down any helpful ideas - take them in stride - try them out - or mark them all down - take a day and do them - then get back to us with the results. OH and as for your new parts - IT IS POSSIBLE to buy defective parts. I've had it happen. I'm sure others have too. Radio Shack was good for that. As an example, I ordered a transistor once for a CB set - the issue narrowed down. I was sent a "replacement". I didn't bother to check it before installation. Turn on the switch - and smoke appeared. I checked it - and called the parts supplier. Here - THEY had a transistor "marked in their records" as a Sub - when in fact it was not. They apologized to me for the error - sent me a new "correct" part and offered to pay me for my time and any other damaged parts. And with the RS parts - I've had occasion to plug in a diode, transistor, etc. and find it to be bad. Took back out of circuit and tests revealed open parts in most cases. It might be extra work, but I double check my parts (if I can) - before installing. I'd rather know they're good BEFORE I put them in than to find out after - they weren't. In most cases, that few seconds can save a lot more time. And I HAVE caught a few more "defective" new parts since I've learned to do this from experience. As to your caps - I've seen many a chat in these groups discussing some brands to be very poor in quality - so who knows - maybe you latched on to some of those? At this point - anything is possible. Some of the other folks gave some damned good advice - best to just take time to prove out one way or another - what is happening. For now - we're all guessing - since we're going by what you say and we're not there to see it. As for "Spaghetti" - that term could be overkill. Wiring used before PC boards was often labeled as such. Even afterwards. Be it a lot of wiring or a little - the term could be being used. It is no big deal. The only way it could make a difference is if a wire "is" going to a wrong place, a piece of braid or a stray conductor from one of them is shorting OR something along the lines of inductance is happening as a result. Don't give up on the project - "LEARN" from it. The knowledge acquired from repairing it could outweigh any cost you've got into it thus far. I can't recall if you've got the schematic for it or not - if not - you may want to get it and study and compare. That could be immeasureable. As to the sound being "Squishy" - here's where a scope "may" have come in handy "BEFORE" tearing into it. So.......... there are lots of things to look at and consider. NO - you don't want to "waste" time - no one does. But in this case - working in the dark - there may be little choice til something starts to present itself. Just my 2 cents. |
#46
Posted to sci.electronics.repair
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Tried to recap a tube receiver, and failed.
On Apr 28, 4:39 am, (Derwin) wrote:
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it on it starts playing music for a few seconds after it warms up, then the music fades out and and hum takes over. I don't really know what I'm doing, and the wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering if the value difference, added up over 8 caps would make a difference? Other than that, does anyone have any advice based on my description of the unit's behavior? Any comments whatsoever might be helpful.. Go to paul stenning's 'uk vintage radio repair and restoration forum' . There you will find numerous specialists. Post the exact model and make and year if poss. -B. |
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