Slightly beyond my skills but I have a little Aiwa amplifier as part of my Carryin' Compo which only works on one channel. Now, there really isn't much to this thing but I can't get my head round what could cause it.
Any ideas?
That is also beyond me
Maybe Frank would know?
If it has any controls, have you tried lubing them perhaps with deoxit...just a thought...
maybe a short somewhere or try checking for loose speaker wire or if you hear balanced sound coming from the headphones....
Is it outputting in both channels through the line-out?
This is interesting as the right speaker (from the dead channel) crackles when I wire it up.
Norman, how do you mean? It's really a mini component amp with standard phono (RCA) inputs and speaker binding posts.
If I can hear stereo via the headphone jack (not tried it yet), what does this tell me?
If you take a signal from the line-outs and inject it into another audio device line-in (boombox, whatever) and you can get both channels to work, then that tells me that the pre-amp portion is working fine and your issue is either in the tone controls, output amplifier, or in the connections. But........When you say this is a mini component amp, then are you saying that the device in question is simply an amp and not a boombox? If that is the case, verify that you are in fact injecting a signal through both the L/R inputs. You can also try to reverse the L/R RCA's and if the sound outputted is likewise reversed, then that means that the RCA jacks on one side is not passing a signal.
Every system is different but most headphone jacks is inline and fore of the speaker outs. So if you connect headphones and hear both channels working, then there is a good chance that you have a poor connection in the headphone jacks. Try flooding the headphone jack with deoxit while working the plug in/out repeatedly to see if this helps. If not, then perhaps the output amp is blown, or you have failure of a device in the component level.
Originally Posted by agentorange:
This is interesting as the right speaker (from the dead channel) crackles when I wire it up.
Not uncommon. Many amplifiers are capacitor coupled at the outputs. The capacitors charge up, especially when no speaker is connected. Even when powered off, the capacitors may hold a charge temporarily. When you hook up the speakers, the remaining charge can discharge causing the crackling you hear. Of course once discharged, the crackling should not continue. To verify, you can disconnect and reconnect, you'll probably find that the crackling is gone. Crackling at the outputs can sometimes indicate a bad amplfier. The point is.... no conclusion should be drawn simply from crackling when speakers are connected to an amp that was previously powered on with no speaker connected.
Norman, I very much appreciate the time you've spent here. I'm sure there's nothing more dull than idiots asking basic questions.
OK, just done some tests with the following conclusions...
1. No signal from dead right channel with input RCA's reversed.
2. Very quiet signal (and crackly) can be heard from dead channel when using headphones.
Questions...
1. Am I right in thinking that the speaker output is effected if there are issues in the headphone circuit? I suspect you've already answered this above, in which case I need to dust off my deoxit & report back.
The Amp is this nice little Aiwa A10, which is actually a nice quality bit of kit with nicely made chassis and components. Nice enough to be worth the effort.
OK, an update here....
Just flooded headphone jack with Deoxit & worked the jack in and out with the following results...
1. No change to dead speaker output (rear binding posts, not binding posts but you know what I mean)
2. When listening through headphones I can clearly hear audio but about 50% louder than before along with crackle. The audio goes louder and quieter in a very even pulse with exact 1.5 second gaps between peaks, very odd.
What you appear to have here is an integrated amplifier. That means it is an amplifier with a built in preamplifier.
In answer to your question regarding the headphone circuit -- most boomboxes (since we are in a boombox forum) power the headphones directly via the output amplifiers. The signal path is --> input --> selector swtich --> preamplifier --> tonal controls --> amplifier --> headphone jack --> external speaker jack--> internal speakers. When headphone plug is inserted into the jack, then the signal to the speakers is broken and routed through the headphones instead. That is why if you hear sound normally via headphones but not in speakers, then the jack is usually dirty. In this case, integrated amplifiers usually have a separate circuit for the headphones due to the fact that they produce far MORE power than a typical boombox. Judging by the size of that torroidal transformer and those massive heatsinks, my guess is that your component system would have a separate headphone amplifer as it appears it would output significant power. You say that you hear 50% louder than before? Before cleaning? That means that the cleaning made a difference? Then perhaps more vigorous cleaning might be helpful but the crackling suggests failing capacitors or an amplifier stage to me.
Previously, I asked you to test and see if the amp would output a proper signal via the line-outs. Yours doesn't seem to have line-out but does have TAPE play/record RCA's. I believe the TAPE-play RCA's would be comparable to line-outs. If you can hear a proper signal through both L/R channels in this manner, then you can (probably) conclude that your output modules are not blown and the issue is fore of the amplifier.
Anyhow, I fear at this point that your problem is not something simple and that you have a failure at the component level or a bad connection through poor solder joint or something of that nature. I have seen RCA type jacks crack the solder joint where they connect to the PCB. But wait...... strike that. If you can hear both channels from your headphones, then the input signal is probably OK. Or it could be a coupling capacitor failing. Or it could be one of the amplifier modules or pre-amplfier stages have failed. In any event, it goes without saying that the first order of business would be to try cleaning the function selector switch and hope for the best --it is worth a try, because if that doesn't do it, then it sounds like the repair is beyond your ability.
Just FYI, I have seen many amplifier's exhibit exactly the crackling type noise you speak of. Recapping has fixed it most of the time and the rest -- bad amplifier stage somewhere.
Norman, this is great.
OK, when I wire the RCA Tape Outs into a tape deck I can see equal signal strength from both channels, is this telling me the pre-amp is working fine or the output stage?
I'm now going to check this thing over for broken solder connections and lube some selectors/jacks.
To be fair, I guess all I want here (apart from getting it working) is to ascertain whether it's a simple fix or not prior to permanent retirement. I.e. I'm not going to throw it away if I can fix it.
To add...
Just wired it all up again (with speakers) after applying a bit of lube and the crackle has gone from the dead channel and clear audio can be heard but very, very quietly. So, an improvement & something tells me (based on zero knowledge) that this is now far from beyond repair.
Does this help our diagnosis any Norman?
If you are getting improvements after performing some cleaning, then poor connection may indeed be the case. More vigorous cleaning may do it.
Remember.....
The signal path is --> input --> selector swtich --> preamplifier --> tonal controls --> amplifier --> headphone jack --> external speaker jack--> internal speakers.
Line-out signals is usually tapped between the pre-amplifier and tonal controls. So if you are getting good clean audio at the line-outs, then you can safely presume that the issue is not present fore of that location.
So........ we can eliminate these. Focus on the remaining.
The signal path is --> input --> selector swtich --> preamplifier --> tonal controls --> amplifier --> headphone jack --> external speaker jack.
Frequently, broken feelers inside controls (such as volume) can cause one channel to drop and function weird. It's worth investigating.
You've explained this very well and I am now considerably wiser than I was. OK, I am now armed with enough knowledge (and confidence) to eliminate a lot of options and focus on specific areas. My worry is that some of the components on this amp due to it's size are very small and fully enclosed thus making it tricky to gain access. I'm presuming by 'feelers' you're referring to the variable plates inside the volume pots and the like? Overall construction of the amp is good and connections all seem quite robust, tempted to suggest areas where wear/fatigue/dirt are present.
Anyway, onwards I go.
Glad to be helpful. No, it is definitely NOT beyond repair. The only question is whether the malady requires help beyond your own capability.
Correct on the feelers. They are the spring loaded contacts that wipe the variable resistor board. They are frequently assembled mechanically with small teeny pegs that can and do break off. Normally, there are 2 sets (1 per channel) and if one falls off or gets dislodged, then it bridges unintended signal paths or loses contacts causing unreliable and weird operation. Of course the variable resistors boards themselves can also wear out.
As for the diagnstics I asked you to do, it's merely to help isolate and narrow the possible stages where the problem may exist. You are the man on the spot since only you can actually test and see the amp. Obviously, I can't help you diagnose it down to the component level fault without it being in front of me. Good luck and hope you get it back up. It looks like a really nice unit. If I weren't across the pond, I would say send 'er here.
