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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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#1
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Erratic output on Kenwood KR-A5030
This receiver seems to work fine in every respect except that the volume
knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. .. |
#2
Posted to sci.electronics.repair
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Erratic output on Kenwood KR-A5030
"Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Gareth. |
#3
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Erratic output on Kenwood KR-A5030
Sam Goldwasser wrote:
This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? I don't know about the Kenwood, but it`s a common occurance on some lower end pro audio amplifiers and usually attributable to high resistance contacts on the speaker relay. Ron |
#4
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Erratic output on Kenwood KR-A5030
"Gareth Magennis" writes:
"Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Yeah, that's what I think also. I even seem to recall this very receiver having that problem back before dinosaurs..... There are two relays with covers that pop off. Thanks! --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#5
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Erratic output on Kenwood KR-A5030
"Sam Goldwasser" wrote in message ... "Gareth Magennis" writes: "Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Yeah, that's what I think also. I even seem to recall this very receiver having that problem back before dinosaurs..... There are two relays with covers that pop off. Thanks! --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. Power it up and don't turn up the volume. Put a scope probe at either the speaker relay input or the emitter resistors of the power transistors. Turn the volume up slowly. If you see signal before the sound comes on then you know it's either the relay, or speaker switch. If you see signal at the same time the sound comes on, then you have a different problem. I'm a little confused by your observation that the problem happens whether or not the speakers are enabled. How can you hear anything with the speakers disabled? Are you using headphones? Or do you mean you turn the volume up and down with the speakers off, then turn the speakers on, and then everything is ok? -- David Farber David Farber's Service Center L.A., CA |
#6
Posted to sci.electronics.repair
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Erratic output on Kenwood KR-A5030
"David Farber" writes:
"Sam Goldwasser" wrote in message ... "Gareth Magennis" writes: "Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Yeah, that's what I think also. I even seem to recall this very receiver having that problem back before dinosaurs..... There are two relays with covers that pop off. Thanks! --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Power it up and don't turn up the volume. Put a scope probe at either the speaker relay input or the emitter resistors of the power transistors. Turn the volume up slowly. If you see signal before the sound comes on then you know it's either the relay, or speaker switch. If you see signal at the same time the sound comes on, then you have a different problem. Intend to do something like that, or just clean the relay contacts! I'm a little confused by your observation that the problem happens whether or not the speakers are enabled. How can you hear anything with the speakers disabled? Are you using headphones? Or do you mean you turn the volume up and down with the speakers off, then turn the speakers on, and then everything is ok? Turn on and no sound. Turn off Speaker A switch. Turn up volume and turn back down. Turn on Speaker A and it works at low volume. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#7
Posted to sci.electronics.repair
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Erratic output on Kenwood KR-A5030
"Sam Goldwasser" wrote in message ... "David Farber" writes: "Sam Goldwasser" wrote in message ... "Gareth Magennis" writes: "Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Yeah, that's what I think also. I even seem to recall this very receiver having that problem back before dinosaurs..... There are two relays with covers that pop off. Thanks! --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Power it up and don't turn up the volume. Put a scope probe at either the speaker relay input or the emitter resistors of the power transistors. Turn the volume up slowly. If you see signal before the sound comes on then you know it's either the relay, or speaker switch. If you see signal at the same time the sound comes on, then you have a different problem. Intend to do something like that, or just clean the relay contacts! I'm a little confused by your observation that the problem happens whether or not the speakers are enabled. How can you hear anything with the speakers disabled? Are you using headphones? Or do you mean you turn the volume up and down with the speakers off, then turn the speakers on, and then everything is ok? Turn on and no sound. Turn off Speaker A switch. Turn up volume and turn back down. Turn on Speaker A and it works at low volume. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html I remember the Kenwood KR-4070 had the power switch piggy backed onto the speaker selector switch. If yours has the same design, make sure the long, skinny, metal piece that connects the rotary switches together has not slipped out of place. That might be contributing to the problem. This is where hooking up your oscilloscope will answer your question in a matter of seconds. Good luck. -- David Farber David Farber's Service Center L.A., CA |
#8
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Erratic output on Kenwood KR-A5030
On Saturday 03 May 2008 06:57, David Farber wrote:
I remember the Kenwood KR-4070 had the power switch piggy backed onto the speaker selector switch. If yours has the same design, make sure the long, skinny, metal piece that connects the rotary switches together has not slipped out of place. That might be contributing to the problem. This is where hooking up your oscilloscope will answer your question in a matter of seconds. Good luck. I have a KR4070 here, and that is probably not the problem. That pin indeed falls out sometimes, but it just results in not being able to turn the speakers on; or the entire amplifier for that matter. BTW I find it rather strange that dirty relay contacts would cause this behavior, most notably because after the sound has kicked in, the low volume setting works again, and because turning up the volume with the speakers disabled, also turns them on. If your relay experiment fails, try locating the power amplifier section and determine if the problem is present on the input signal, or only on the power output. |
#9
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Erratic output on Kenwood KR-A5030
"Sam Goldwasser" wrote in message ... "David Farber" writes: "Sam Goldwasser" wrote in message ... "Gareth Magennis" writes: "Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Yeah, that's what I think also. I even seem to recall this very receiver having that problem back before dinosaurs..... There are two relays with covers that pop off. Thanks! --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Power it up and don't turn up the volume. Put a scope probe at either the speaker relay input or the emitter resistors of the power transistors. Turn the volume up slowly. If you see signal before the sound comes on then you know it's either the relay, or speaker switch. If you see signal at the same time the sound comes on, then you have a different problem. Intend to do something like that, or just clean the relay contacts! I'm a little confused by your observation that the problem happens whether or not the speakers are enabled. How can you hear anything with the speakers disabled? Are you using headphones? Or do you mean you turn the volume up and down with the speakers off, then turn the speakers on, and then everything is ok? Turn on and no sound. Turn off Speaker A switch. Turn up volume and turn back down. Turn on Speaker A and it works at low volume. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. Just sounds like flaky relay contacts to me. Put a load on it look at a sine wave output on a 'scope, and tap on the relay(s). Probably see one or more of them cut out - could be solder connections there at the relay as well. To David Farber: This model isn't even CLOSE to the old KR-4070... that was an analog 40 w/ch receiver from the '70s. This is a more modern surround receiver. Mark Z. |
#10
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Erratic output on Kenwood KR-A5030
"Wiebe Cazemier" wrote in message . home.nl... On Saturday 03 May 2008 06:57, David Farber wrote: I remember the Kenwood KR-4070 had the power switch piggy backed onto the speaker selector switch. If yours has the same design, make sure the long, skinny, metal piece that connects the rotary switches together has not slipped out of place. That might be contributing to the problem. This is where hooking up your oscilloscope will answer your question in a matter of seconds. Good luck. I have a KR4070 here, and that is probably not the problem. That pin indeed falls out sometimes, but it just results in not being able to turn the speakers on; or the entire amplifier for that matter. BTW I find it rather strange that dirty relay contacts would cause this behavior, most notably because after the sound has kicked in, the low volume setting works again, and because turning up the volume with the speakers disabled, also turns them on. You may well find it strange, but that is in fact exactly what happens in the real world. Last time I heard any kind of technical explanation, it seemed to be little understood and/or quite a complex situation - often a kind of diode junction is formed. Turning up the volume (voltage across the junction) often seems to "punch through" the dirt and it will then behave normally for a while. You could try Googling for technical information on this. I did for about a minute and gave up. Gareth. If your relay experiment fails, try locating the power amplifier section and determine if the problem is present on the input signal, or only on the power output. |
#11
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Erratic output on Kenwood KR-A5030
"David Farber" writes:
"Sam Goldwasser" wrote in message ... "David Farber" writes: "Sam Goldwasser" wrote in message ... "Gareth Magennis" writes: "Sam Goldwasser" wrote in message ... This receiver seems to work fine in every respect except that the volume knob has to be turned up to a modest value before the speakers come on. This will occur regardless of whether the speakers are actually enabled. After that, it will usually run at any volume until power cycled It has been sitting unused for about 10 years but don't know if this was a problem back then. Any common issues with this model? Thanks. Often this is down to dirty speaker relay contacts. If it has output relays. Sometimes you can pop the top off them to spray the contacts, others are sealed and need to be replaced. Signal relays do much the same thing by the way. If you see any relays inside, try getting it in the state where the speakers aren't working and then start tapping them with a stick. Yeah, that's what I think also. I even seem to recall this very receiver having that problem back before dinosaurs..... There are two relays with covers that pop off. Thanks! --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Power it up and don't turn up the volume. Put a scope probe at either the speaker relay input or the emitter resistors of the power transistors. Turn the volume up slowly. If you see signal before the sound comes on then you know it's either the relay, or speaker switch. If you see signal at the same time the sound comes on, then you have a different problem. Intend to do something like that, or just clean the relay contacts! I'm a little confused by your observation that the problem happens whether or not the speakers are enabled. How can you hear anything with the speakers disabled? Are you using headphones? Or do you mean you turn the volume up and down with the speakers off, then turn the speakers on, and then everything is ok? Turn on and no sound. Turn off Speaker A switch. Turn up volume and turn back down. Turn on Speaker A and it works at low volume. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ I remember the Kenwood KR-4070 had the power switch piggy backed onto the speaker selector switch. If yours has the same design, make sure the long, skinny, metal piece that connects the rotary switches together has not slipped out of place. That might be contributing to the problem. This is No, here there are separate pushbuttons for Spkr A and Spkr B. where hooking up your oscilloscope will answer your question in a matter of seconds. I know. I'm lazy. Also, getting to the solder side of the PCB looks like a major disassembly. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#12
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Erratic output on Kenwood KR-A5030
This is a final report on this problem.
I believe it was actually the solder connections to the PCB and not the relay contacts themselves. Kenwood actually provided easy acces to the bottom of the PCB. A large square section was partially punched out with only 4 thin metal strips holding it in place. So, cutting two on one side allowed the relevant part of the botton plate to be swung out of the way exposing everything but the AC line circuitry. When duplicating the erratic behavior, gently touching one of the relay pins would make the sound come and go. While there was no visible crack, the relay's solder terminals are physically the stationary contacts. So, the constant pounding over the years must have loosened at least one of them just enough to make marginal contact with the solder on this single-sided PCB. I removed the relay entirely and inspected the interior. The contact points were in perfect condition with no sign of wear or burning. After reinstalling the relay, the receiver has been 100 percent reliable. Thanks to all who replied. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#13
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Erratic output on Kenwood KR-A5030
"Sam Goldwasser" wrote in message ... This is a final report on this problem. I believe it was actually the solder connections to the PCB and not the relay contacts themselves. Kenwood actually provided easy acces to the bottom of the PCB. A large square section was partially punched out with only 4 thin metal strips holding it in place. So, cutting two on one side allowed the relevant part of the botton plate to be swung out of the way exposing everything but the AC line circuitry. When duplicating the erratic behavior, gently touching one of the relay pins would make the sound come and go. While there was no visible crack, the relay's solder terminals are physically the stationary contacts. So, the constant pounding over the years must have loosened at least one of them just enough to make marginal contact with the solder on this single-sided PCB. I removed the relay entirely and inspected the interior. The contact points were in perfect condition with no sign of wear or burning. After reinstalling the relay, the receiver has been 100 percent reliable. Thanks to all who replied. --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#14
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Erratic output on Kenwood KR-A5030
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