Zen and the Art of Hi-Fi Repair

[maxhifi]

Oh man, I love the headlight analogy; that really helps me to understand! I love how you explained this. Didn't know vintage Elnas had such a good reputation; that's good background knowledge to have. My go-to replacement caps have become Nichicon Gold Tunes, Elna Silmic IIs, and Kemets for filter caps/big main caps. Nichicon seems to deliberately oversize some of the Gold Tunes for vintage replacements, a welcome feature when trying to Smurf up a way to fit a teeny modern cap into a gaping bracket vacated by a King Kong sized 63V/8000uF.

I use Nichicon and Panasonic 105 degree caps for almost everything. For filter caps you can search by size, on mouser, and almost always find a fit that way. CDE makes some decent affordable big filter caps, which are in physical sizes that fit the brackets on old gear - made in usa too, don't see that every day anymore.

 

[birchoak]

There is a secondary consideration for some of these older units. I just did a KX-1030 ( Cassette deck).. my rules typically mean I will rebuild any filter caps and/or power supply as a minimal effort. In this case, it uncovered a couple of caps that measured over 8 ohms of resistance vs the .50 ish that was expected. I also had a couple more on the main board that were running about 10 degrees hotter than everybody else per heat sensor. So 8 caps in total on the main board.. four know troublemakers to films and 4 electolyics. Where the problems arose is the traces on the main board are very, very thin and easily lifted.. like by sneezing nearby. So as much as I would love to replace ALL the caps and there is a crap ton of them, I stuck with these.. and I still had to repair two pads. Some of these units really do not lend themselves to repair so the idea of minimal work is a good one. @maxhifi , good thinking about replacing "matching sets".. thats what I had here.. the bad ones were all Chem-cons vs the Elnas which seem to hold up well even at 40 years

I'm not familiar with that particular Yamaha deck, but I do have a KX-530 that is the best cassette deck I have ever used. Much easier to work on than NAD, Harman Kardon, Onkyo decks I've had. Fastest FF and rewind I've had the pleasure to behold. Has a damned light in the cassette well; finally, someone had the cajones to put an LED in the cassette well so I can get a visual on how much tape I have left. Sounds virtually identical to whatever source I've recorded, what with the HX-PRO. Only has two heads but sounds just as good as the three-head Onkyo it replaced, and I have absolutely no need for three heads anyway. I did have to touch up a bunch of solder joints behind the face plate to get the display to come back to life, but it wasn't a big deal. The thing has been built with enough logic and simplicity that taking it apart isn't a nightmare.

 

[birchoak]

I use Nichicon and Panasonic 105 degree caps for almost everything. For filter caps you can search by size, on mouser, and almost always find a fit that way. CDE makes some decent affordable big filter caps, which are in physical sizes that fit the brackets on old gear - made in usa too, don't see that every day anymore.

I've never heard a bad thing about Panasonic caps, let alone most Panasonic products. I've just started modifying my parts searches to find appropriate diameters, etc.---very good advice, sir. Never heard of CDE but always willing to try a product if someone here likes it. I don't know if others do this, but I often bump the quantity up to ten to get the discount, which can be significant. Then I have some spare caps, too.

 

[maxhifi]

I've never heard a bad thing about Panasonic caps, let alone most Panasonic products. I've just started modifying my parts searches to find appropriate diameters, etc.---very good advice, sir. Never heard of CDE but always willing to try a product if someone here likes it. I don't know if others do this, but I often bump the quantity up to ten to get the discount, which can be significant. Then I have some spare caps, too.

CDE is Cornell Dubilier, they've been making capacitors since the dawn of time. If you work with old US made electronics, you will see the name again and again. They're good stuff.

 

[birchoak]

CDE is Cornell Dubilier, they've been making capacitors since the dawn of time. If you work with old US made electronics, you will see the name again and again. They're good stuff.

Ok, now I recognize the name. Acronym threw me.

 

[Binkman]

Well you been posting for 3 pages... when are you going to get to it? perhaps you can borrow a scope and help with some analytics..

 

[birchoak]

Well you been posting for 3 pages... when are you going to get to it? perhaps you can borrow a scope and help with some analytics..

I'm still meditating. Just kidding. Replaced the big cap under the main board (I assume this is a filter cap) and the twin caps on top of the board (output caps?). Passed DBT, then plugged into regular outlet for music test. After about 20 minutes (I concur with the guy at select45rpm.com on this), bass seemed deeper and cleaner. Took my sweet time doing it and found that I actually enjoyed the process. And the darned thing still works--most important of all. This Sherwood is a delight to work on--so very simple to open up, clean internal layout, virtually no dust inside.

I have a scope (curbside rescue) but it will not self-calibrate so I'm pretty sure it's useless for actual work. Every once in a while I hook it onto active speaker terminals and my son and I watch the show. It's definitely good for that.

 

[Mike Sweeney]

Great idea using heat sensor to find naughty components. I forgot about that. What do you use? Are they expensive?

I use a cheap one from Harbor Freight.. the AC guys like them for measuring ducts etc for temps.. car guys like it for hose temps etc. I find it's handy for measuring heat sinks and the bigger caps. Isopropyl will work really good on crowded boards to show something getting hot since it will evaporate off that part way sooner than the rest of the parts. I use that on SMT stuff looking for shorts. Quick and dirty and a lot cheaper than these FLIR guns I see now.

 

[cabs]

Glad I stumbled onto this. I have an old Adcom GTP-500ii that *works* but clearly needs to be refreshed. It has a veiled, soft sound now compared with a lesser quality Kenwood pre from 5-10yrs later, and when i switch the tone control circuit into the mix i seem to be getting DC from the lab out. I do get some audio from the 'norm out' (and the tone controls seem to work somewhat, but with a much lower output level) but the distortion alert LEDs on my GFP-535 light up (and an extremely loud 'pop' is heard) whenever the tone controls are switched in/out of the circuit (via the 'tone in' button)

I am armed with a moderate level of soldering experience, lots of patience, a nice low-wattage detail soldering iron, (12w i believe? one with some very fine tips) and a printout of the service manual that looks to have gone through a couple iterations with a photocopier. Should I replace all the electrolytic caps? (no, clearly not - I did read the OP's hints/suggestions) There are no less than 6 PCBs that have 10+ components (a few more with only a couple, that seem to be for buttons or connections on the rear) and I can follow through the schematics with a moderate level of understanding of how the signal traverses its way along the circuitry. Is this my best bet? (when electrolytic caps fail, they can allow DC to pass through, is that correct?) I would really love to restore this thing close to its original glory and go back to using it on my main audio-only setup.

 

[Mike Sweeney]

Should I replace all the electrolytic caps?

This is a relatively "recent" tuner.. early 90s right? I would do a few things first.. DeOxit all the controls.. and it's not just using the spray and flood everything.. Thats really wasteful and can cause issues. Get a bottle of D100L ( D100L-2DB-8211).. yeah it's pricy.. stop bitching and suck it up buttercup, this is restoration work In all seriousness, this small container will last quite a while and I use mine of everything.. including the broiler oven I just fixed this weekend.. a few pennies of cleaner saved me 150 dollars by not buying a new oven. THat paid for the bottle many times over. Anyways.. do that to all controls, Deoxit has "Fader lube" for the sliders if required. Dont forget to clean any cross connections between boards. Those get crappy too and are often times forgotten in the deoxit binge. Personal speaking, I always replace the filter caps in the power supply. They tend to be undersized and/or abused over the years. Often, cleaning up the power can "solve" alot of issues. Replacement of incandescent lights with LEDs can lower the power draw, I've seen it help a few times.. Thats a nice to have. I've seen a few units with socketed chips.. why I have no idea.. but pull, clean and put them back if needed. Those seem to be the exception fortunately. I would not recommend a whole sales swap of caps at this point UNLESS you see signs of leakage/bulging caps. If it was about early-mid 2000s, I'd say do them all. There were a few billion caps sold with a stolen formula used in the electrolytic and it ended badly. Around 2004, we replaced every cap on IBM motherboards because of this.. and they were not the only ones. IBM came into our shop and replaced over 900 motherboards ( major retailer) because the problem was so bad.

For a bit of history
https://www.eetimes.com/author.asp?section_id=30&doc_id=1329037#

 

[cabs]

^ Indeed - well, the circuit boards seem to be date stamped 1989 but I think somewhere around that time period. (89-93) I'm guessing at bare minimum I would probably need to swap those that are related to the tone control circuitry. (since that's causing DC to output)

I remember that! My first IT related job was working H&R Block tech support while I was in college years ago (mid 2k's) and we were constantly getting in dead HP's where there were bulging caps.

 

[birchoak]

This is a relatively "recent" tuner.. early 90s right? I would do a few things first.. DeOxit all the controls.. and it's not just using the spray and flood everything.. Thats really wasteful and can cause issues. Get a bottle of D100L ( D100L-2DB-8211).. yeah it's pricy.. stop bitching and suck it up buttercup, this is restoration work In all seriousness, this small container will last quite a while and I use mine of everything.. including the broiler oven I just fixed this weekend.. a few pennies of cleaner saved me 150 dollars by not buying a new oven. THat paid for the bottle many times over. Anyways.. do that to all controls, Deoxit has "Fader lube" for the sliders if required. Dont forget to clean any cross connections between boards. Those get crappy too and are often times forgotten in the deoxit binge. Personal speaking, I always replace the filter caps in the power supply. They tend to be undersized and/or abused over the years. Often, cleaning up the power can "solve" alot of issues. Replacement of incandescent lights with LEDs can lower the power draw, I've seen it help a few times.. Thats a nice to have. I've seen a few units with socketed chips.. why I have no idea.. but pull, clean and put them back if needed. Those seem to be the exception fortunately. I would not recommend a whole sales swap of caps at this point UNLESS you see signs of leakage/bulging caps. If it was about early-mid 2000s, I'd say do them all. There were a few billion caps sold with a stolen formula used in the electrolytic and it ended badly. Around 2004, we replaced every cap on IBM motherboards because of this.. and they were not the only ones. IBM came into our shop and replaced over 900 motherboards ( major retailer) because the problem was so bad.

For a bit of history
https://www.eetimes.com/author.asp?section_id=30&doc_id=1329037#

What issues can flooding the controls with DeOxit cause? I ask because I've begun doing this (I do let the unit dry out overnight before turning it on again).

 

[Mike Sweeney]

What issues can flooding the controls with DeOxit cause? I ask because I've begun doing this

SOme of the better controls use "damping grease".. yah.. that's a real thing.. its a specialty grease that gives a nice "feel" to the controls by providing a bit of resistance your fingers twirling it. Its non-conductive so it doesnt short out the controls and it handles temps so it doesn't oooze out over time. I managed to get a sample pack so I have a small stash of it. You can also wash away any lube that the OEM may have put into the controls. So if you get crazy with it, use some faderlube to help protect the tracks. If the pots are noisy after all this, use some Shield which can quiet down a noisy pot but Shield is pricy so I use it when I have to. I also use DeOxit L260N ( non-conductive) grease inside power switches and slide switches if I take them apart.

From Nye Lubricants


Broad temperature film strength.
Since it is the film of lubricant that prevents wear, good film strength is essential. While arcing is not usually a problem, high heat generated by resistance — the temperature can reach 225°C in automotive dimmer switches, for example — requires a lubricant to retain film strength over a broad temperature range.

Ambient conditions also affect lubricant selection. Very low temperatures cause some lubricants to become so viscous that they prevent motion. On the other hand, in underhood applications where performance-related devices are multiplying, extreme wide temperature and fuel-resistant lubricants have become a necessity.

A note about damping greases.
Although not intended as track lubricants, Nye’s damping greases are widely used on potentiometers and other rotary devices where shaft/bearing lubrication is needed to damp free motion and produce a “velvet feel.” See our application summary on Damping Greases for details.

 

[birchoak]

SOme of the better controls use "damping grease".. yah.. that's a real thing.. its a specialty grease that gives a nice "feel" to the controls by providing a bit of resistance your fingers twirling it. Its non-conductive so it doesnt short out the controls and it handles temps so it doesn't oooze out over time. I managed to get a sample pack so I have a small stash of it. You can also wash away any lube that the OEM may have put into the controls. So if you get crazy with it, use some faderlube to help protect the tracks. If the pots are noisy after all this, use some Shield which can quiet down a noisy pot but Shield is pricy so I use it when I have to. I also use DeOxit L260N ( non-conductive) grease inside power switches and slide switches if I take them apart.

From Nye Lubricants


Broad temperature film strength.
Since it is the film of lubricant that prevents wear, good film strength is essential. While arcing is not usually a problem, high heat generated by resistance — the temperature can reach 225°C in automotive dimmer switches, for example — requires a lubricant to retain film strength over a broad temperature range.

Ambient conditions also affect lubricant selection. Very low temperatures cause some lubricants to become so viscous that they prevent motion. On the other hand, in underhood applications where performance-related devices are multiplying, extreme wide temperature and fuel-resistant lubricants have become a necessity.

A note about damping greases.
Although not intended as track lubricants, Nye’s damping greases are widely used on potentiometers and other rotary devices where shaft/bearing lubrication is needed to damp free motion and produce a “velvet feel.” See our application summary on Damping Greases for details.

Well, as always, the more you learn about a thing the more you realize how much there is to know! I did not know about the dampening grease but it makes sense. I will ease off on my brief but energetic DeOxit flooding phase.

 

[Mike Sweeney]

Well, as always, the more you learn about a thing the more you realize how much there is to know!

Yeah.. tell me about it. I learned about this last year

 

[z-adamson]

From what I've gathered, as electrolytic capacitors age they build up an increased resistance to current and don't let as much power through as they did when they were new (anyone, jump in and correct this unwashed amateur!). They can look perfectly fine from the top but can be leaking through the leads, right at the board where you can't see

Double checking...

This could be said about any cap and as such any cap should be replaced then, right? Not just filters.

Me personally, I do blanket recaps, replacement of relays, STK if they have them and trim pots at a minimum. Sometimes transistors, resistors, diodes and PC boards, depending on the device.

I only have gotten my butt kicked by a device once, a hk775, the first amp I ever worked on.

 

[gadget73]

There are different failure modes of capacitors. Leakage is when voltage bleeds from one side to the other. Pretty simple concept. ESR equivalent series resistance) is a little different. It acts like there is a resistor in series with the capacitor, so it limits the amount of current the capacitor can deliver. This is more of a problem in power supply circuits. When used as an audio coupling / DC blocking cap it generally doesn't matter all that much since the capacitor isn't dealing with much current to speak of.

and then of course there is physical leakage which rots nearby component leads along with foil traces on double sided boards.

I'm not specifically opposed to blanket re-caps and I've done them myself but I don't believe its the first thing that ought to be done to a malfunctioning device unless its obvious that it is a capacitor problem. Often folks seem to have some glitch and the "time to re-cap" suggestion is trotted out before any diagnostics are done. Caps may or may not fix the problem, but it definitely adds a whole bunch of new variables to the troubleshooting process. I only like to re-cap things when I'm confident that the thing is basically working correctly already, that way I at least have somewhere to start with the troubleshooting process. Obviously if visual inspection shows leakage or other physical failure, then there isn't a lot of need to proceed further before changing the clearly defective parts.

The last two times I expected a re-cap situation to fix my ailment it was noisy transistors. They did get a re-cap after I figured out the problem and fixed it though.

 

[z-adamson]

There are different failure modes of capacitors. Leakage is when voltage bleeds from one side to the other. Pretty simple concept. ESR equivalent series resistance) is a little different. It acts like there is a resistor in series with the capacitor, so it limits the amount of current the capacitor can deliver. This is more of a problem in power supply circuits. When used as an audio coupling / DC blocking cap it generally doesn't matter all that much since the capacitor isn't dealing with much current to speak of.

and then of course there is physical leakage which rots nearby component leads along with foil traces on double sided boards.

I'm not specifically opposed to blanket re-caps and I've done them myself but I don't believe its the first thing that ought to be done to a malfunctioning device unless its obvious that it is a capacitor problem. Often folks seem to have some glitch and the "time to re-cap" suggestion is trotted out before any diagnostics are done. Caps may or may not fix the problem, but it definitely adds a whole bunch of new variables to the troubleshooting process. I only like to re-cap things when I'm confident that the thing is basically working correctly already, that way I at least have somewhere to start with the troubleshooting process. Obviously if visual inspection shows leakage or other physical failure, then there isn't a lot of need to proceed further before changing the clearly defective parts.

The last two times I expected a re-cap situation to fix my ailment it was noisy transistors. They did get a re-cap after I figured out the problem and fixed it though.

A recap isn't about repairing a specific problem, it is about restoring the device. Other things go into the restoration too though....relays, transistors, pots....etc.

 

[Mike Sweeney]

Re-capping is much like discussing "restoring" a classic car or airplane. There is always, always a debate as to what to do, when to do it and how far to take. Years ago, if the underside of the car wasn't polished enough to see yourself, it wasn't "restored".. never mind the factory new car never looked that good. Now it's all about "survivor patina" or some such rubbish. I like my cars that look good, drive safely and include a few modern improvements. Which is why I'll never own a real "collectible".. My radios are the same thing. I restore to working order that can run all day and do it without smelling bad or overheating or anything else unpleasant. I do try to keep the next guy in mind so no extra holes or hacking up the chassis etc. Everything I do is reversible if you wanted to.

With all that said, I do this.. I always.. ALWAYS replace the power supply caps and filter caps regardless of what else is wrong. You cannot fix something without a known good baseline and clean/accurate power starts everything. I do that, RR the power switch, check the fuse etc. I will inspect for obvious issues.. burned out parts etc.. I normally deal in Marantz so if I do all that and the protection relay wont kick in, the amps come out. Then I jump each amp back in as needed to see if it's an obvious issue. I will always recap in the end.. but I try to limit what boards I'm working on so when it goes south I have a starting point. Any more I replace carbon composite resistors. They are more trouble than they are worth at 40+ years. The carbon films last near forever. On Marantz, I will always replace the output final transistors as a matter of course. They don't cost that much and to tear a unit back apart in a few weeks because a weak transistor craps out is not worth being "original" in my mind. You have no idea how abused they are or have been.

The last two cassette decks were treated the same.. power supply rebuilt first. In both cases, I found bad caps even though the units "worked" .. time spent putting in belts, cleaning sludge off the mechanics, cleaning the tape path, pots connectors etc all make a very nice sounding rig most of the time.

My Kenwood stack was like this. The amp worked but sounded flat.. the turntable worked but drifted here and there. The receiver worked but only on strong stations. In all three cases, the caps were the key. I'm reminded of the sistine chapel art. For decades the art was seen as dark and angry because of the "dark colors' etc.. Then someone realized that while it was impressive art while dark, it was just dirty from centuries of smoke and dirt. That the colors were really bright and punchy when cleaned. My amps worked but were flat.. but they were original. But when recapped, they went to being bright and responsive but now are not original but they sound original I can live with that ..

 

[gadget73]

A recap isn't about repairing a specific problem, it is about restoring the device. Other things go into the restoration too though....relays, transistors, pots....etc.

I know that, but I've seen "re-cap it" trotted out as an early suggestion in how to fix whatever ails a piece of equipment and I think that is not wise.