Losing hope for the C100....

So I bought this gem a month or so ago, looks great, hadn't been used in a while, had a lot of static when operating switches. So much so that the channels would cut out somewhat here and there. So I took her all apart, cleaned all the switches extensively and searched for broken solder joints. I couldn't find any. It really looks good on the inside. I put it all back together and the right channel sounded great! No more static or cutting out. The left channel however, wasn't working at all.

So in a last ditch effort before I put this up for sale, I'm going to describe whats going on as best as I can with the hope that someone might have dealt with this before. The sweep meters both move great, left and right. Only the right LEDs light up though. However if you switch from stereo to wide mode, some of the left LEDS light up and some sound comes from the left speaker. Plugging in headphones gives the same result. Sound on right no sound on left. The fact that the left will put out sound when in the wide mode makes me hopeful the channel isn't blown, but I'm stumped and a bit frustrated. :annoyed:

When 1 channel is dead in stereo mode but has sound is wide mode, it indicates a break or fault in the preamp signal path for that channel. The reason is because in wide mode, the signal from the opposite channel is mixed (with a delay) into both channels to give the perceived spatial effect.

The problem might still be that your switches and controls still need cleaning, but if that's the case the issue will usually be intermittent. If it's not intermittent, then you most likely have a fault in the preamp signal path.

Ok that makes sense, but I wouldn't know where to find this signal path.

Trace out the switches and short the contacts one by one this will eliminate the faulty contact!

Never give up! Get it fixed. Good luck!

NO! Do not short anything unless you know what you are doing! Short the wrong one and you could blow some semiconductors, many of which may no longer available anywhere.

Anyone with the technical knowledge to diagnose this can do so without having to ask for step by steps. Otherwise the best thing to do is allow someone with the proper expertise to troubleshoot for him.

To suggest to anyone, especially someone who is already saying they don't know how to do this, to start shorting contacts on a nice grail, would be terribly irresponsible. The fault could just as well be a failed buffer amp (transistor) as well as electronic components and not just a poor connection that becomes obvious from shorting the right contact.

It could be something simple - I worked on a C100F with a dead channel - all it needed was one amp chip to be reflowed.

Take it to a tech and get professional advice - the C100F is definately worth the cost.

James.....

My C-100 had a 'dead' channel too, (from an earlier post):


I had a similar problem and cleaned everything within an inch of it's life and the problem persisted.

I then went about replacing the amp chips and that still didn't fix it.

After taking it to my repairer he diagnosed voltage leaking out of the mode selector.

He rejigged it and rewired it slightly and the problem's gone.

I'm not saying it's the same, but it's definitely a fault C100's sometimes develop.
You'll need access to a proper repairer to diagnose this probably anyway.

Good luck!



Rock On.

BoomboxLover48 said:

Never give up! Get it fixed. Good luck!

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Gluecifer said:

My C-100 had a 'dead' channel too, (from an earlier post):


I had a similar problem and cleaned everything within an inch of it's life and the problem persisted.

I then went about replacing the amp chips and that still didn't fix it.

After taking it to my repairer he diagnosed voltage leaking out of the mode selector.

He rejigged it and rewired it slightly and the problem's gone.

I'm not saying it's the same, but it's definitely a fault C100's sometimes develop.
You'll need access to a proper repairer to diagnose this probably anyway.

Good luck!



Rock On.

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Thanks for the encouragement guys. A new day has brought renewed hope and determination. Unfortunately here in rural New Hampshire we have plenty of tractor repair repair guys, but no vintage electronic repair guys. Super duper you are on a whole different level, but what I do understand is that it not hopeless! I will take another look at those switches and maybe reflow some solder joints. I must say the channel that is playing absolutely pounds, I can only imagine it with the other channel banging away! Thanks again guys I will keep you posted.

Superduper said:

NO! Do not short anything unless you know what you are doing! Short the wrong one and you could blow some semiconductors, many of which may no longer available anywhere.
Anyone with the technical knowledge to diagnose this can do so without having to ask for step by steps. Otherwise the best thing to do is allow someone with the proper expertise to troubleshoot for him.
To suggest to anyone, especially someone who is already saying they don't know how to do this, to start shorting contacts on a nice grail, would be terribly irresponsible. The fault could just as well be a failed buffer amp (transistor) as well as electronic components and not just a poor connection that becomes obvious from shorting the right contact.

Click to expand...

I guess it's implied jasatc77 has A good idea of what he's doing cause he pulled it apart and put it back together again Yeah!

I should have clarified to trace the switch logic de-energised

Cheers.

Hope it works out for you. If not, I need a RIKERTRON battle partner. ELAMTRON in all white

jasatc77 said:

Ok that makes sense, but I wouldn't know where to find this signal path.

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hopey said:

I guess it's implied jasatc77 has A good idea of what he's doing cause he pulled it apart and put it back together again Yeah!

I should have clarified to trace the switch logic de-energised

Cheers.

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If the litmus test to whether a collector can trace out a circuit fault is whether he can take it apart and put it back together again, then I suppose we can just go ahead and "assume" 90% of the guys here can all trace out dead circuits, Yeah! Go ahead and start probing and shorting pads guys, go for it!

Oh, or then maybe you can just read the third post (quoted above) by the original poster.

@Jsatc77, I will say this: The C100's are known for poor quality connectors resulting in poor connections and there are many, especially the ones tethering boards together. The wiring is thick/stiff and not very flexible. Perhaps try wiggling some connectors with it powered up to see if your dead channel suddenly comes back to life. If so, you've found the bad connector. It's not as far fetched as you might think.

All I'm saying is know your limitations and please farm out those you don't feel comfortable working on, especially the grails. It might be an easy fix, maybe not. But if you don't know, then chances are the problem is beyond your skill level to proceed and you can do more harm than good. I see it time/time again the damage that is done by haphazard hackers who I'm sure meant no harm and proceeded with good intentions.

^HE has spoken...

ok ok no fighting. No I am not stupid, I will not ruin a good boombox, and Hopey was trying to help. Are we friends again?

Nope, there's no fighting. My words often come across a bit rough but it's always meant to be helpful. Also, far too often, I see posts that are short on words and makes a presumption that everyone possess the same set of skills and knowledge as everyone else. We often forget that along with experienced tinkerers (those that have access to oscilloscopes, signal generators, top of the line fluke meters, LCR meters, frequency counters, etc etc and know how to use them) we also have newbies, novices and casual folks who also peruse these sites, and these short good intentioned advice often can do harm if that advice is followed thinking that it's OK to, for example (just start shorting contacts.) So this isn't really about you, it's more out of concern for other folks who are also reading but maybe not actively posting in these forums. Do I shoot from the hip? Absolutely. But I always say what I mean, and mean what I say (unless I made a mistake, of course, lol). Anyhow, I just hope to remind everyone to think before you post when giving advice that could be taken literally. This thread isn't via PM, it's in an open public forum visible to everyone and not everyone can change a belt. To some, that task is easy as pie. To others, it could be a nightmare and whenever I see a newbie ask "my deck doesn't work anymore, what's wrong?" I cringe when I see responses encouraging the newbie to just dig right in... "it's easy, just change the belt!" Yeah, right. It's just that I hate to see that Aiwa or Sanyo afterwards when it gets ruined. So Hopey, don't take this personal, it is not meant in that way.

No worries superduper, Technically speaking you can't do DIY on these boxes as once you open them up there are exposed Live contacts @ 110v or 240v which can be very nasty. The safest option is get someone trained to look at it but that means $$$ probably more than it is worth to the owner.

101 Electrical Safety always use RCD protected circuit to power your box when tinkering! You'll still get a boot but limited to 30ma.

Actually, RCD protectors are common in UK (and I guess AU too) but here in the states, we have GFCI's and those only limit to 5ma. When working on AC powered devices, I use an isolation transformer. When powered up by such, although not advised, you can safely touch the live wire without getting shocked since the live wire is isolated from mains ground (E) and therefore, no return path to mains ground through our body. Of course, there is still circumstances where you can get shocked but this is far safer method of working on live mains powered devices.

Whether or not a device is economically feasible to the owner to repair by a professional is irreleveant anyhow as to whether or not he should just jump in without having at least some experience or background in electronics theory (not necessary though helpful when changing belts or fixing mechanical issues.) However, to trace a circuit, it's not easy for a novice (ask around to any member here who tried to learn by fire) and of course working on tuner circuits is on a whole 'nother level and far more difficult concept to grasp and master. Heck we have guys here asking how do I connect an LED to the boombox to light it up? Not to make light of it but rather to show that some things we consider to be so easy is to some, not at all easy.

Hopefully, I've made clear my point that it's important to guage the technical level of the person seeking advice before responding since it's important to understand that if you are going to suggest a path more difficult or that requires a greater technical skillset than the OP possesses, that the person offering advice should then be willing to follow up and provide the handholding necessary to walk that person safely through the process.

Super has given me the courage to try working on my own stuff. Couldn't have done most of it with out his help and I have learned a lot from him. I'm surprised you still hang around here! Thanks again.

I'm curious what makes the mode switch on the C100 so flaky, is it plated with something weird? I'll be getting at mine soon, it's giving me fits also.

And thank you too, Superduper, for being here for us. I am really glad you're around, I've learned quite a lot from your posts so far and get me motivated to figure this shite out. I used to be into electronic projects years ago but drifted away from it, now I've got a new motivation to return to it and am currently repurchasing stuff to get set back up (scope, meters, etc) to a level where I can actually fix some of the more sophisticated issues.

There's nothing special or different about the C100 controls and they aren't coated with anything weird. In fact, that's exactly the problem on antique or classic stuff (except for the very high end stuff), which is that they aren't coated for the most part, or not coated with "noble" metals. Noble metals prevent oxidation and lasts a very long time but are also much more expensive. That's why they oxidize so quickly. The connectors on the 100 have stiff wiring, almost like you would see on cars. When they are strained at an extreme position, one or more contacts could lose connectivity. That's why wiggling them is a cheap and easy method to check -- why not? It's easy and costs nothing. Fixing them might be a whole nother matter. For maximum reliability, it might even be worthwhile to consider removing the connectors and hard soldering the wires. That might make it more of a PITA to work on later, but until it does, it is far more reliable in this way.

As for help, I used to post alot more and consequently, was, I think, more helpful to those requiring some step by steps in past years. In recent times, due to time constraints and a lack of patience, and other "life" things, I have been leaving that chore to others to answer since you can only answer the same things over/over again so many times before things start to get old. I conserve and pick/choose my posts nowadays to keep things sane, otherwise it gets overwhelming and then I become neglectful to life's other priorities.