Many of the members here love to jam their boxes, display them, carry them out on their shoulders, host disco parties, whatever. Some folks just like listening to soft music in the comfort of their homes. I guess we all get different things from the hobby. For me, what I get out of the hobby is rehabilitating them. Sure, I listen to them but I don't do break dancing or nothing like that. In fact, boomboxes with modest prowess but clean clear sound is more valuable to me. How many can you listen to anyhow? But mostly, I just love getting something that is not quite 100% but has the potential to be nice, then take a critical look and then fix. Take the following example:
Sony CFS-81. NOT a highly sought after model. A lower smaller model, to be sure. Is it worth doing all the following work? From an economic point of view -- not in the least. Firstly, you bring a car into the dealership and no matter what is wrong, you got to fix it -- even with labor at $100 per hour. At that rate, a boombox like this probably wouldn't warrant 10 minutes of repair time before reaching the point of diminishing return. So..... we don't do this for profit. Just for the love of it.
Anyhow, I received this. It was advertised as good shape, tape deck not working and tweeter has come loose in case. Sold as-is. That's it. Pretty typical ebay description. OK, now after I receive it, here are the issues I find, instead:
Cassette is not working -- needs belts and idler wheels dressed.
Woofers are filthy
Tweeter chrome caps smashed in and one fallen off, inside grill
Cockroach legs inside the tuner dial
Controls are sooooo noisy it's practically unusable
Weird chirping, oscillating
Something (big) loose inside
balance control works but neither BASS or TREBLE has any effect
OK, right to work here.
Firstly, the transformer has broken loose, both mounting towers broke off and one side of the plastic dam is broke off. I had to reaffix the towers, then hot glue the transformer to the back of the case. Finally, built up the area surrounding the tower with hot glue and reattach everything.
Here is the tape deck. It is going to be rebelted. See the crud under the tape buttons? THIS IS WHY I DO THIS.
Tweeter has lost it's center chrome cap. They don't sell chrome replacement but black ones which will result in like $10 cost after shipping is factored in. Forget that -- just take the original cap, re-shape it best I can, and reglue it back -- both sides.
BEFORE
AFTER
Seems the cockroach body parts inside the tuner dial compartment is inaccessible as it's sealed from the backside. Wait a minute, it looks like it can be cleaned from the front side.... if only I can get that tuner glass off!
Luckily, I was able to get the stainless trim off since the adhesive was already worn. It came off without too much effort -- hooray! Definitely not a high percentage procedure. Tuner glass was affixed in the usual manner -- plastic pegs spot welded in place. An exacto knife made quick work of the rivets and the glass was removed, then cockroach parts/poo was scrubbed off. Looks presentable afterwards.
Woofers -- grills removed.
BEFORE
AFTER
This bothered me to no end. Look carefully and you can see (2) areas where the circuit board traces were "cut" on the left and right side of the board. Clearly this was deliberate. I thought that maybe it was done due to problems in a part of a circuit and the cuts were done to isolate the problem areas rather than fix it. After tracing the broken circuit on the obverse, I have found that there is a grounded jumper on the other side of the board. Apparently, that is a signal line that was probably suffering from EMI or RFI. The grounded jumper takes the same path but via a shielded cable. It's apparent to me that this was done to correct a poor circuit board design and rather than redesign the board, the PCB it was "retrofitted" to correct the issue. I felt comfortable with it and left it alone.
TOOLS OF THE TRADE:
My capacitor stockpile and my Panavise circuit board jig, then my temp controlled soldering iron.
Re-capping the boards. Both the tuner and Main board were re-capped. On the amp, only the large 4700uf cap was not replaced but it was tested and found good. Normally, on a more valuable box, I would replace them all including that filter cap. The tuner was recapped except the 2 under the RF shielding -- mainly because the tuner was not experiencing any issues and because I didn't want to affect the tuner in a manner that could possibly create an alignment issue as I wanted to avoid the extra work. However, mostly, the best excuse is that I just got lazy towards the end since I did remove the shielding under the amp board and redid those caps. Leads were left intact until the end to make it easier to determine which caps were new and which were old. You can tell by looking hard but this allows me to see my progress at a glance. While I sometimes re-cap a board on the chassis, for the most part, I always remove the board if possible as it's much easier and there is less chance of having the soldering iron damage something while trying to snake across stuff. This is one of my easier re-caps and demonstrated here just to show the process.
Before:
After:
Finally, how to deal with the non-responsive tonal control issue? After some testing, I've concluded that the tonal control assembly is shot. Yeah, I know what you are all saying -- yeah yeah, clean the controls with deoxit, it works miracles. Ok, sure, I did that -- no response. Since there is no way to confirm whether the cleaning was effective, it had to be reassembed to test. Of course now that it's CONFIRMED not working, I have to disassemble the boombox once again to tackle this. No, parts are NOT available anymore. I'm going to have to rebuild that thing. Damn! Removed the control, disassembled it, cleaned off all the broken cockroach parts, and tested the resistor board. Broken traces everywhere. Looks good but no continuity anwhere except on the balance control. So.... redrew the circuit using silver trace compound, and retest -- all good. To ensure a "relatively" lasting repair, the new traces was given 2 coats of urethane conformal coating, then the shaft assemblies were greased with silicone grease. On the resistor board, grease inhibits connectivity so that was treated with deoxit GoLD 100% pure brushed on the contact, then the whole thing reassembled, resoldered back onto the board.
BEFORE
AFTER
OK, so reassembled the clean, rebelted mechanical assembly, the tuner, the main board. All cables reattached, properly bound. This is what I like to see.... A PLACE FOR EVERYTHING, AND EVERYTHING IN IT'S PLACE. I'm a stickler for attention and make sure everything is done right. It costs me much more time but I don't believe in sloppy work. A loose wire could rub on the tape mechanism and cause a scraping noise during tape operation. If you have a tape deck that does that, I'll bet you an apple that the wires weren't properly tied and is rubbing on the spinning capstan flywheel. Also, loose wires could cause buzzing and other noise from speaker induced vibrations.
I won't bore you with pictures of me scrubbing the knobs with a toothbrush, cleaning the cabinet with fantastic, slight polishing of the cassette door and tuner glass with acrylic polish etc. You all know how to do that anyhow. If this was a finer, more desirable box like an M70, M9994, it would get the full disassembly and case shampooed. In this case, the cleaning was more like spring cleaning rather than a makeover.
Ready to go back in.....
HERE IT IS, BACK TOGETHER AGAIN. Sound is good but it's not a really loud box. Very pretty design, with the dual LED VU's and weird stepped styling. I've seen and heard better boxes. However, if all we ever wanted was the best box, then no one would ever have more than 1 box to their name. We own and do these things in the name of "boombox-collecting" hobby. Was it worth it? You bet -- it was fun as heck, although I never smiled once during the job. Was it worth it? Not a chance, my pocket book is already hurting and there is no chance in hell that I could ever sell it for what was it was purchased for and the work expended. However, if anyone just has to buy this from me, they could "steal" it for a song (PM me), which is not anywhere near what the boombox has in it money wise. No one will ever mistake it for an M70. However, if someone wants a Sony CFS-81 in their collection, this one is all done and should be reliable for some time to come. In my experience, however, most people would rather spend $75 on a box that needs work, then spend $125 on one that has been done. I'm posting this to show how that is often the "wrong" approach. If you like doing this, like I do, then sure. Why buy and tinker with something that doesn't need tinkering, and pay more in the process. However, if you don't have the ability to do this, then all I'm saying is don't even touch one of those boxes that says it needs this and that and EZ fix. Like heck it is..... when you bring the box to your tech and he quotes you $50 or $75 per hour, and he does THIS LEVEL OF SERVICE, you're going to find out fast that either you are going to pay far more than the boombox is ever worth to restore it, or the box will never be 100% again since it's repair will be deemed not "economical" to repair.
Cheers
~Norm.
Sony CFS-81. NOT a highly sought after model. A lower smaller model, to be sure. Is it worth doing all the following work? From an economic point of view -- not in the least. Firstly, you bring a car into the dealership and no matter what is wrong, you got to fix it -- even with labor at $100 per hour. At that rate, a boombox like this probably wouldn't warrant 10 minutes of repair time before reaching the point of diminishing return. So..... we don't do this for profit. Just for the love of it.
Anyhow, I received this. It was advertised as good shape, tape deck not working and tweeter has come loose in case. Sold as-is. That's it. Pretty typical ebay description. OK, now after I receive it, here are the issues I find, instead:
Cassette is not working -- needs belts and idler wheels dressed.
Woofers are filthy
Tweeter chrome caps smashed in and one fallen off, inside grill
Cockroach legs inside the tuner dial
Controls are sooooo noisy it's practically unusable
Weird chirping, oscillating
Something (big) loose inside
balance control works but neither BASS or TREBLE has any effect
OK, right to work here.
Firstly, the transformer has broken loose, both mounting towers broke off and one side of the plastic dam is broke off. I had to reaffix the towers, then hot glue the transformer to the back of the case. Finally, built up the area surrounding the tower with hot glue and reattach everything.
Here is the tape deck. It is going to be rebelted. See the crud under the tape buttons? THIS IS WHY I DO THIS.
Tweeter has lost it's center chrome cap. They don't sell chrome replacement but black ones which will result in like $10 cost after shipping is factored in. Forget that -- just take the original cap, re-shape it best I can, and reglue it back -- both sides.
BEFORE
AFTER
Seems the cockroach body parts inside the tuner dial compartment is inaccessible as it's sealed from the backside. Wait a minute, it looks like it can be cleaned from the front side.... if only I can get that tuner glass off!
Luckily, I was able to get the stainless trim off since the adhesive was already worn. It came off without too much effort -- hooray! Definitely not a high percentage procedure. Tuner glass was affixed in the usual manner -- plastic pegs spot welded in place. An exacto knife made quick work of the rivets and the glass was removed, then cockroach parts/poo was scrubbed off. Looks presentable afterwards.
Woofers -- grills removed.
BEFORE
AFTER
This bothered me to no end. Look carefully and you can see (2) areas where the circuit board traces were "cut" on the left and right side of the board. Clearly this was deliberate. I thought that maybe it was done due to problems in a part of a circuit and the cuts were done to isolate the problem areas rather than fix it. After tracing the broken circuit on the obverse, I have found that there is a grounded jumper on the other side of the board. Apparently, that is a signal line that was probably suffering from EMI or RFI. The grounded jumper takes the same path but via a shielded cable. It's apparent to me that this was done to correct a poor circuit board design and rather than redesign the board, the PCB it was "retrofitted" to correct the issue. I felt comfortable with it and left it alone.
TOOLS OF THE TRADE:
My capacitor stockpile and my Panavise circuit board jig, then my temp controlled soldering iron.
Re-capping the boards. Both the tuner and Main board were re-capped. On the amp, only the large 4700uf cap was not replaced but it was tested and found good. Normally, on a more valuable box, I would replace them all including that filter cap. The tuner was recapped except the 2 under the RF shielding -- mainly because the tuner was not experiencing any issues and because I didn't want to affect the tuner in a manner that could possibly create an alignment issue as I wanted to avoid the extra work. However, mostly, the best excuse is that I just got lazy towards the end since I did remove the shielding under the amp board and redid those caps. Leads were left intact until the end to make it easier to determine which caps were new and which were old. You can tell by looking hard but this allows me to see my progress at a glance. While I sometimes re-cap a board on the chassis, for the most part, I always remove the board if possible as it's much easier and there is less chance of having the soldering iron damage something while trying to snake across stuff. This is one of my easier re-caps and demonstrated here just to show the process.
Before:
After:
Finally, how to deal with the non-responsive tonal control issue? After some testing, I've concluded that the tonal control assembly is shot. Yeah, I know what you are all saying -- yeah yeah, clean the controls with deoxit, it works miracles. Ok, sure, I did that -- no response. Since there is no way to confirm whether the cleaning was effective, it had to be reassembed to test. Of course now that it's CONFIRMED not working, I have to disassemble the boombox once again to tackle this. No, parts are NOT available anymore. I'm going to have to rebuild that thing. Damn! Removed the control, disassembled it, cleaned off all the broken cockroach parts, and tested the resistor board. Broken traces everywhere. Looks good but no continuity anwhere except on the balance control. So.... redrew the circuit using silver trace compound, and retest -- all good. To ensure a "relatively" lasting repair, the new traces was given 2 coats of urethane conformal coating, then the shaft assemblies were greased with silicone grease. On the resistor board, grease inhibits connectivity so that was treated with deoxit GoLD 100% pure brushed on the contact, then the whole thing reassembled, resoldered back onto the board.
BEFORE
AFTER
OK, so reassembled the clean, rebelted mechanical assembly, the tuner, the main board. All cables reattached, properly bound. This is what I like to see.... A PLACE FOR EVERYTHING, AND EVERYTHING IN IT'S PLACE. I'm a stickler for attention and make sure everything is done right. It costs me much more time but I don't believe in sloppy work. A loose wire could rub on the tape mechanism and cause a scraping noise during tape operation. If you have a tape deck that does that, I'll bet you an apple that the wires weren't properly tied and is rubbing on the spinning capstan flywheel. Also, loose wires could cause buzzing and other noise from speaker induced vibrations.
I won't bore you with pictures of me scrubbing the knobs with a toothbrush, cleaning the cabinet with fantastic, slight polishing of the cassette door and tuner glass with acrylic polish etc. You all know how to do that anyhow. If this was a finer, more desirable box like an M70, M9994, it would get the full disassembly and case shampooed. In this case, the cleaning was more like spring cleaning rather than a makeover.
Ready to go back in.....
HERE IT IS, BACK TOGETHER AGAIN. Sound is good but it's not a really loud box. Very pretty design, with the dual LED VU's and weird stepped styling. I've seen and heard better boxes. However, if all we ever wanted was the best box, then no one would ever have more than 1 box to their name. We own and do these things in the name of "boombox-collecting" hobby. Was it worth it? You bet -- it was fun as heck, although I never smiled once during the job. Was it worth it? Not a chance, my pocket book is already hurting and there is no chance in hell that I could ever sell it for what was it was purchased for and the work expended. However, if anyone just has to buy this from me, they could "steal" it for a song (PM me), which is not anywhere near what the boombox has in it money wise. No one will ever mistake it for an M70. However, if someone wants a Sony CFS-81 in their collection, this one is all done and should be reliable for some time to come. In my experience, however, most people would rather spend $75 on a box that needs work, then spend $125 on one that has been done. I'm posting this to show how that is often the "wrong" approach. If you like doing this, like I do, then sure. Why buy and tinker with something that doesn't need tinkering, and pay more in the process. However, if you don't have the ability to do this, then all I'm saying is don't even touch one of those boxes that says it needs this and that and EZ fix. Like heck it is..... when you bring the box to your tech and he quotes you $50 or $75 per hour, and he does THIS LEVEL OF SERVICE, you're going to find out fast that either you are going to pay far more than the boombox is ever worth to restore it, or the box will never be 100% again since it's repair will be deemed not "economical" to repair.
Cheers
~Norm.
Super cleaning job Superduper 
.
i'll even let you keep 'em and play with 'em and take pictures of 'em all you want! 
:'-( 
but these days electronics are designed as throw away surface mount technology and just a few chips control everything, I don't see as many people repairing todays electronics in 30 years like we do with these old boomers. 