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Yamaha CR-2040 Shorted During DC/Bias/Voltage Adjustment

avionic said:
Hope you made good notes or photos where to reconnect everything..:biggrin:
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Oh man, I was total OCD about it...it's daunting before you start and I knew I needed a good process in place to keep track of it all. I'm going to try to start pricing out what it would be to replace every cap to get a basis and then whittle down if needs be. The pull and replace part doesn't bother me, actually enjoy that part. The finding and evaluation of data sheets to determine the right replacement is the hard part here.

What about the large filter caps? I understand those are going to be pricey. Meter wont go that high to test them. Are those an automatic for replacement or what's the advice there?

The one small cap I pulled was CR915 that tested at 1.264 uf and should have been 1.0 uf... so the small ones should probably all just go but there sure is a lot of them!
 
avionic said:
C915 ?... To totally recap the 2040 will run close to $60-80 give or take. Including the two large caps.

https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/382LX223M080B062VS/?qs=fupM46RXT60ay8BUYD/V0Q==
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Oops, typo, C915.

For $60-80 I have no issue whatsoever dropping that into this. Never heard of the Cornell Dubilier caps....everybody talks about Nichicon Gold caps but I've never heard a unit redone with those. This being a long term keeper, are these Cornell Dubilier perfectly suitable to be the choice of capacitors to use? I know nothing about what types of sonic differences would be expected from using one brand vs another. And I don't care to put Nichicon Gold in just so I can say the same thing I've heard other people say many times about recapping their old equipment. I like to save money where I can so I can spend money on the big stuff that matters and actually makes a difference. The CR-2040 is one of the "big" things that matters to me, and if a higher grade cap will serve it better I'm glad to spend the money on it...but again, I don't care about the bragging rights about what type of caps I used, just that it sounds tip-top! So, avionic, if this were yours, what would you do?
 
avionic said:
I have a 2040 in the wings awaiting work. This is what I'm using..
https://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/382LX223M080B062VS/?qs=fupM46RXT60ay8BUYD/V0Q==
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Cornell Dubilier it is then. You're gonna use those alligator clips when adjusting the DC offset and bias on yours, right...? Ugh, still kinda bummed about that but actually glad to have a reason to start tearing it down and having to learn so much more about it than if it had just functioned great when it arrived.
 
Definitely use the mini-grabbers! One short is quite enough.

Electrolytic caps are too cheap to bother with using old ones. But I do get a giggle of people selling "original" filter caps on eBay -- why on earth would you put a 50 year old electrolytic in to replace an equally old one?

You will be limited to what is available for filter caps, typically they are semi-custom for the model and exact replacements are often difficult to find. We are pretty much stuck with whatever manufacturer makes one that will physically fit and has the correct minimum capacitance and voltage rating.
 
So in searching/filtering on mouser/digikey/wherever....capacitance, voltage, lead orientation/physical size are must. Are there additional specific parameters (ie - tolerance) that I should keep in mind to narrow down choices for caps across the board? Or some rules for larger caps and different rules for smaller?

And little gear shift here, replace tantalum with tantalum? Any different search parameters for those?
 
85°F or 105°F.. If the capacitor is in close proximity of warm or hot running transistors or resistors .. 105° is the way to go.
 
There is another consideration with capacitors, and that's the use in the actual circuit. Power supply/filtering caps need low impedance to work correctly with minimal heating, while caps in the audio path need to be very "quiet" -- which is to say don't change the sound of the signal. One of the BOM lists in post above this one will help you with that since they've been selected by someone who is familiar with those requirements.

Small value electrolytics can be replaced with film caps IF the film caps will fit -- there are four such caps in my KA-80 I would love to replace with film, but there is no way to physically stuff them into the space, lead spacing on the films is too wide and I don't think all four would fit into the space of those tiny electrolytics. Film caps last much, much longer and are better in the signal path, but standing them off the board on long leads is a VERY poor idea in the pre-amp section. Last thing you want there is a stray signal antenna.....
 
I used all 105 degree caps in my KA-80 -- inverted single board, and they are known to run very hot, probably why the one that shorted failed.
 
avionic said:
85°F or 105°F.. If the capacitor is in close proximity of warm or hot running transistors or resistors .. 105° is the way to go.
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Good point, that C915 cap was a bit toasty on one side from the transistor/heat sink right by it.
 
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HPMguy said:
Film caps last much, much longer and are better in the signal path, but standing them off the board on long leads is a VERY poor idea in the pre-amp section. Last thing you want there is a stray signal antenna.....
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Very good point, not that I planned to try something like that but that will go in the memory bank in the event I ever run into fit up problems here or in the future.
 
avionic said:
They have been making electrolytic caps for a very long time..

https://www.cde.com/why-cde/history
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That's a cool history read on them, do they manufacture in the US still or did their manufacturing go to China...they didn't explicitly state that when mentioning China.

On the mouser specs on it...1,000 hour lifespan? That seems awfully short for something that will get daily use for multiple hours a day. Hopefully like a 1 year guaranteed warranty on a product that you know can last 20 years with no issues.
 
I put together this spreadsheet of all Electrolytic capacitors in the CR-2040 parts list if this is of use to anybody paying attention to this or that stumbles across it in the future. First tab is in the order listed from the parts list, second tab is sorted by capacitance value. Third tab is an "Others" list that I've pasted below with a question. DESC column shows any additional info from the part description beside the type of capacitor. (Ummm, doesn't look like I can upload an Excel file, pasted in posts below, PM me if you want the spreadsheet).

I did not include any Mylar or Ceramic capacitors in this list as avionic has advised those rarely go bad. Questions as follows:

MS meaning from the descriptions?

(Z) after voltage value in the parts list? See C917 and C949 in parts list or spreadsheet.

'Others' tab has Polyester Film, SA, and Bipolar as capacitor types from the description in the parts list. Series of questions for this as follows, table pasted below:
- Which types should I plan to replace while replacing the Electrolytics?
- (G) in description on PolyFilm caps?
- "50V(J)" change anything from just 50V?
upload_2021-2-25_13-34-4.png
 
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