Conion C100 - no sound?
- Thread starter mmcodomino
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JVC Floyd said:
Thanks for your thoughts
The alarm actually works perfectly on both boxes
I really go the amp way since both boxes show exactly the same symptoms and this seems to be well known for them
@Max:
Just to clarify, I have not diagnosed your box. My contribution previously was only to follow up on Bill's post about my post in the other forum, regarding a different C100 and my comments regarding the C100 amps being failure prone and my suggestion that if replacing, to find OEM chips. That's it.
Before you replace your amps, you really should be investigating whether or not the amps are at issue. Keep in mind that your amps are separate for left and right channel. So unless both amps failed at the same time (less likelihood), then whatever the issue is must be common to both channels. There are only so many things that can be common to both channels and a single weak solder joint or a single bad capacitor is unlikely to be the culprit since unless it involves the power rail or something similar, such failures usually involve only 1 channel if it's in the audio stream. This involves checking to make sure your amps have power, making sure your tuner has power and you can do that by checking the appropriate places with voltmeter.
You should also check your line-in and line-outs because (1) your Cassette is not working and (2) you did not check your line-in. That's already 2/3 of the source generators leaving only the tuner. Well, if your tuner is dead, and you don't confirm whether either of those other two sources are "live", then the dead amp conclusion is faulty. Also, you need to verify whether line-outs are working because that will at least tell us whether the line-amps are working. If yes, then we can move on to test the preamps.
Your power amps -- remember to check pin 2 or pin 5 of each amp with a signal tracer. A signal received at either of those two pins suggests that the amp is not amplifying the signal. However, if either of those pins, and I think pin 2 is the primary one, does not receive a signal, then the faulty amp diagnoses would be premature since the amp can not reproduce or amplify an empty signal.
Finally, you say the alarm works perfectly. Well that sucks. I mean not really, but the alarm really is an oscillator that sends a signal to the amp, and if the amp is blasting out a loud sound from both speakers -- that suggests to me that the amps may indeed be working OK since it's apparent that it has no trouble reproducing and amplifying an audio signal.
Just to clarify, I have not diagnosed your box. My contribution previously was only to follow up on Bill's post about my post in the other forum, regarding a different C100 and my comments regarding the C100 amps being failure prone and my suggestion that if replacing, to find OEM chips. That's it.
Before you replace your amps, you really should be investigating whether or not the amps are at issue. Keep in mind that your amps are separate for left and right channel. So unless both amps failed at the same time (less likelihood), then whatever the issue is must be common to both channels. There are only so many things that can be common to both channels and a single weak solder joint or a single bad capacitor is unlikely to be the culprit since unless it involves the power rail or something similar, such failures usually involve only 1 channel if it's in the audio stream. This involves checking to make sure your amps have power, making sure your tuner has power and you can do that by checking the appropriate places with voltmeter.
You should also check your line-in and line-outs because (1) your Cassette is not working and (2) you did not check your line-in. That's already 2/3 of the source generators leaving only the tuner. Well, if your tuner is dead, and you don't confirm whether either of those other two sources are "live", then the dead amp conclusion is faulty. Also, you need to verify whether line-outs are working because that will at least tell us whether the line-amps are working. If yes, then we can move on to test the preamps.
Your power amps -- remember to check pin 2 or pin 5 of each amp with a signal tracer. A signal received at either of those two pins suggests that the amp is not amplifying the signal. However, if either of those pins, and I think pin 2 is the primary one, does not receive a signal, then the faulty amp diagnoses would be premature since the amp can not reproduce or amplify an empty signal.
Finally, you say the alarm works perfectly. Well that sucks. I mean not really, but the alarm really is an oscillator that sends a signal to the amp, and if the amp is blasting out a loud sound from both speakers -- that suggests to me that the amps may indeed be working OK since it's apparent that it has no trouble reproducing and amplifying an audio signal.
Superduper said:@Max:
Just to clarify, I have not diagnosed your box. My contribution previously was only to follow up on Bill's post about my post in the other forum, regarding a different C100 and my comments regarding the C100 amps being failure prone and my suggestion that if replacing, to find OEM chips. That's it.
Before you replace your amps, you really should be investigating whether or not the amps are at issue. Keep in mind that your amps are separate for left and right channel. So unless both amps failed at the same time (less likelihood), then whatever the issue is must be common to both channels. There are only so many things that can be common to both channels and a single weak solder joint or a single bad capacitor is unlikely to be the culprit since unless it involves the power rail or something similar, such failures usually involve only 1 channel if it's in the audio stream. This involves checking to make sure your amps have power, making sure your tuner has power and you can do that by checking the appropriate places with voltmeter.
You should also check your line-in and line-outs because (1) your Cassette is not working and (2) you did not check your line-in. That's already 2/3 of the source generators leaving only the tuner. Well, if your tuner is dead, and you don't confirm whether either of those other two sources are "live", then the dead amp conclusion is faulty. Also, you need to verify whether line-outs are working because that will at least tell us whether the line-amps are working. If yes, then we can move on to test the preamps.
Your power amps -- remember to check pin 2 or pin 5 of each amp with a signal tracer. A signal received at either of those two pins suggests that the amp is not amplifying the signal. However, if either of those pins, and I think pin 2 is the primary one, does not receive a signal, then the faulty amp diagnoses would be premature since the amp can not reproduce or amplify an empty signal.
Finally, you say the alarm works perfectly. Well that sucks. I mean not really, but the alarm really is an oscillator that sends a signal to the amp, and if the amp is blasting out a loud sound from both speakers -- that suggests to me that the amps may indeed be working OK since it's apparent that it has no trouble reproducing and amplifying an audio signal.
Wow, good read, thanks.
So however, I tested line-in and line in is dead too meaning it does not show movement on the VU meters.
There is no background noise to be amplified by turning the volume/bass/treble knobs up.
One of the two Conions occasionally goes into a 50hz humming mode which is really loud.
You know as far as the alarm goes - I tried it by just pressing the alarm button and heard a very silent alarm in the background - did not mean to scare the heck out of the house owners so the actualy LOUD alarm never made a sound.
The tuner does not show any reception as stated before.
Oh - and the LEDs do not light up when I power the unit up...
Actually there is no signal to be seen on the LEDs at all.
Any ideas left for me?
I still somehow believe in the amp chip theory for some reason - I guess I have faith in it and a semi-experienced friend told me that the 50hz humm could in fact be a short in the amp chips.
The stereo/mono switch does in fact do some static noise to both channels btw...dunno if this is an indicator for anything.
Nothing on headphones either...I did not test line in with line out together since I just did not think of it.
Damn...any ideas on that one Norm? I pretty much described everything I know
.
Well, if you are just hearing a faint noise when alarm is triggered, then it certainly could be the amps. I was merely saying that if the alarm was working perfectly like you said, then the bad amp theory would be suspect. That's like saying nothing electrical in the house works except for the TV. Maybe the power pole got severed? See what I mean, it doesn't make sense.
The thing about the alarm is that it introduces a very high audio signal to the amps, much higher signal than would normally ever be introduced from the audio preamps. So I wonder if you turn the volume control full tilt, would you maybe hear a faint signal through the radio or line-in?
Anyhow, I do recall on one of the Conions I worked on -- that the alarm did emit sound faintly -- nothing like it is supposed to. New amps fixed it. See the thing is that there are two amps run in bridged mode. If one of the two in bridged config is still working, you might could hear an attenuated version of the original signal.
The thing about the alarm is that it introduces a very high audio signal to the amps, much higher signal than would normally ever be introduced from the audio preamps. So I wonder if you turn the volume control full tilt, would you maybe hear a faint signal through the radio or line-in?
Anyhow, I do recall on one of the Conions I worked on -- that the alarm did emit sound faintly -- nothing like it is supposed to. New amps fixed it. See the thing is that there are two amps run in bridged mode. If one of the two in bridged config is still working, you might could hear an attenuated version of the original signal.
Superduper said:
Sorry about my wrong Statements about the alarm.
Here is the thing - one alarm sounds more like a hissing than a horn. The other one is very weak.
I hear nothing from any Input source even at full volume.
I will check the second amp pin as soon as i get my hands on a voltmeter...never did restoration on such a grail box before. Damn, i wish it was just new belts and deoxit :-(
Thanks for your help Norm! I really appreciate it.
This is a call to Norm our master of electronics again 
I just got to test the amps on Conion #2 and (sadly) they in fact work both...right and left channel .
Conion #1 cannot be tested right now since the chassis is out but i am more optimistic with that one since the alarm only came out as weak hissing sound .
Soooo...I found two blown resistors in Conion #2 - one is on the Tape 1 board (the weird double one standing up in a triangle shape) and the other one is on the Amp board.
I strongly doubt that one single blown resistor could actually cause both channels to not produce any sound . What's you word on that, Norm?
I have the feeling that the main board (volume, bass, balance, treble, etc) does not get power somehow...the only reaction i get from it is that the power needle goes up on the VU when switched to radio.
no radio reception, no moving VUs on any source.
damn, this keeps on confusing me...and today's normal techs do not have a clue about these old units .
I just got to test the amps on Conion #2 and (sadly) they in fact work both...right and left channel
.Conion #1 cannot be tested right now since the chassis is out but i am more optimistic with that one since the alarm only came out as weak hissing sound
.Soooo...I found two blown resistors in Conion #2 - one is on the Tape 1 board (the weird double one standing up in a triangle shape) and the other one is on the Amp board.
I strongly doubt that one single blown resistor could actually cause both channels to not produce any sound
. What's you word on that, Norm? I have the feeling that the main board (volume, bass, balance, treble, etc) does not get power somehow...the only reaction i get from it is that the power needle goes up on the VU when switched to radio.
no radio reception, no moving VUs on any source.
damn, this keeps on confusing me...and today's normal techs do not have a clue about these old units
.
Okay, i spent 5 hours swapping the amp boards of both boxes - I am afraid of nothing on a friggin C100F anymore now :annoyed: .
It was pretty darn scary but after reassembling one with the defnitely proven good amp board, the same issues still occured :'-( .
Alarm blasts just perfectly as expected (so apparently I reconnected everything the right way after writing every plug down) but there is no reaction to any other inputs.
Any idea would be greatly appreciated!!!
PLEASE!!!
Have you ever experienced something similar? I mean BOTH Conions have the damn same issue .
Could maybe the pre-amp be bad? Semms unlikely to me though....
A defective function switch? Glue, you had something like that I remember! It was leaking voltage? Could it be a dead switch there?
I am really at the end of my knowledge...expected this to be much easier considering I knew the normal Conion issues.
The only good thing are the cosmetics which are still coming along well.
Does anyone have some Conion guts left?
It MUST be the baord with the volume, balance, bass, treble and function knobs...there basically is no other alternative i guess
A bad rec/play switch is unlikely either since I fiddled with it while it was (not) working.
.It was pretty darn scary but after reassembling one with the defnitely proven good amp board, the same issues still occured
:'-( .Alarm blasts just perfectly as expected (so apparently I reconnected everything the right way after writing every plug down) but there is no reaction to any other inputs.
Any idea would be greatly appreciated!!!
PLEASE!!!Have you ever experienced something similar? I mean BOTH Conions have the damn same issue
.Could maybe the pre-amp be bad? Semms unlikely to me though....
A defective function switch? Glue, you had something like that I remember! It was leaking voltage? Could it be a dead switch there?
I am really at the end of my knowledge...expected this to be much easier considering I knew the normal Conion issues.
The only good thing are the cosmetics which are still coming along well.
Does anyone have some Conion guts left?
It MUST be the baord with the volume, balance, bass, treble and function knobs...there basically is no other alternative i guess
A bad rec/play switch is unlikely either since I fiddled with it while it was (not) working.
Sorry, Max. Without personally looking at it, I can't comment on it any more. Remember there is no service documentation for me to refer to.
Also, I am 100% totally confused as to what exactly is your problems. You say one amp works and the other you aren't sure. But you say they behave the same. Then you say there is two blown resistors but you don't have a volt meter? How do you know they are blown and are you sure they are resistors? Also, the pins I asked you to check -- how did you check it? I asked you to check with a signal tracer. That is not a voltmeter. It is a high gain audio amplifier that amplies a small audio signal level that is line/preamp line level so you can hear/see when an audio signal is present. They aren't common anymore in repair shops. That's more of an old school diagnostic tool.
I think you'd really need to find someone else to help you with this. Unfortunately, issues with the Conion really aren't diyer type of repair except for maybe belts and deoxit issues.
Also, I am 100% totally confused as to what exactly is your problems. You say one amp works and the other you aren't sure. But you say they behave the same. Then you say there is two blown resistors but you don't have a volt meter? How do you know they are blown and are you sure they are resistors? Also, the pins I asked you to check -- how did you check it? I asked you to check with a signal tracer. That is not a voltmeter. It is a high gain audio amplifier that amplies a small audio signal level that is line/preamp line level so you can hear/see when an audio signal is present. They aren't common anymore in repair shops. That's more of an old school diagnostic tool.
I think you'd really need to find someone else to help you with this. Unfortunately, issues with the Conion really aren't diyer type of repair except for maybe belts and deoxit issues.
Superduper said:
I checked the amps the oldschool-touch-the-second-pin-and-best-a-humm-way
Damn...the only (weak) idea i have left is to unplug the alarm Sensor if it somehow sucks up the Power... Lol
Will have a tech friend take a look at them though.
Damn...changing amp boards was a hard task...the only positive thing is that i did Not screw everything up
stragulus
Member (SA)
Kicking this old thread. My box has the *exact* same issue as yours with the working alarm. Pops on switching the stereo lever, but the preamp controls don't do anything at all. And it also has the backgrounde noise plugged in. Mine's a Helix by the way.
I am still investigating it, thread is in the restauration section (fixing ebay legend). So far I have concluded that both my amp chips work OK. The function switch works OK (I traced the audio signal). It does indeed seem to be an issue with power to the preamp board, or at least that's my current hunch.
The power distribution on this thing is really weird. Usually there's a separate print with the transformer on it to drop voltage, a diode bridge to create DC from AC, and a couple of big caps to smooth out the power. Well, there is such a print, but it's missing the filter caps. The output goes to the pcb with the power and alarm buttons on it. From there, multiple wires go to multiple boards. I *think* the main power line goes to the top amp board, which does have several big caps in a corner. Also, from there, a couple of thick wires lead to the preamp board underneath. I don't know if they're supposed to carry power with them, but I have a hunch they do.
I hope to find someone who's willing to do some measurements on their box for me, lacking a service manual. I'll create a new thread by then after some more digging.
I am still investigating it, thread is in the restauration section (fixing ebay legend). So far I have concluded that both my amp chips work OK. The function switch works OK (I traced the audio signal). It does indeed seem to be an issue with power to the preamp board, or at least that's my current hunch.
The power distribution on this thing is really weird. Usually there's a separate print with the transformer on it to drop voltage, a diode bridge to create DC from AC, and a couple of big caps to smooth out the power. Well, there is such a print, but it's missing the filter caps. The output goes to the pcb with the power and alarm buttons on it. From there, multiple wires go to multiple boards. I *think* the main power line goes to the top amp board, which does have several big caps in a corner. Also, from there, a couple of thick wires lead to the preamp board underneath. I don't know if they're supposed to carry power with them, but I have a hunch they do.
I hope to find someone who's willing to do some measurements on their box for me, lacking a service manual. I'll create a new thread by then after some more digging.
dirtwolf
Member (SA)
Hi there! I had this same problem. On circuit board PCB 2 there is a chip Q204 located around the center of PCB 2. The solder on this chip had become loose. When I adjusted the position of this chip the unit started to work again. I am going to go ahead and re-solder the connection today. I really hope this helps!
Here is a picture of the problem chip:
http://imgur.com/XYnZ6k3
Here is a picture of the problem chip:
http://imgur.com/XYnZ6k3
caution
Member (SA)
D204 is a 2SD325 low frequency power amplifier that is part of the alarm circuit. It seems to act as a switch between regular audio and alarm audio. I think if it fails, it leaves normal audio switched off/silenced. I had to replace the neighboring 11V zener diode, D202, to bring mine back to life.
The transistor was fine.
The transistor was fine.
dirtwolf
Member (SA)
Thanks for clarifying Caution! Can you give me any tips on accessing the bottom of PCB 2? It looks like I may have to disassemble the whole boombox. I didn't see anything on the board regarding taking out PCB 2 or PCB 3 circuit boards. I already have all the wires labeled and have tons of pictures. Is there anything else I should consider that is specific to this unit?
caution
Member (SA)
You do need to disassemble a fair amount to expose the bottom of the amp board. You have to disconnect and pull out the frame, and undo all the screws for the controls and pull out both the amp board and I/O board under it, as a pair. It's messy and not recommended unless you really need to.
I don't think you need to if you are only going to replace small amp board parts. Just clip the leads on the top of the board and solder new parts to those.
I don't think you need to if you are only going to replace small amp board parts. Just clip the leads on the top of the board and solder new parts to those.
He said he thought that the transistor had a bad solder joint. Clipping & installing new device from above won't resolve his problem right?
Perhaps, but a board diagram would be most helpful to be sure if it's doable. Schematics are frequently deceptive or misleading. I have seen components that are right next to each other on a schematic that was actually physically located all the way across the board. Unless the transistors leads can stretch across the nodes, I personally don't like the clip method, especially if lead extensions will be required. Long leads, especially on the base connections, and especially on high gain signal transistors (high hfe or beta) may act as antenna and introduce and amplify unwanted signals. Perhaps it's just me, but I much prefer to solder them in the proper way, even if significant disassembly is required to do that.
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