Help with re-cap and upgrade

[spaceludwig]

I have some questions before I start re-capping some channels on an old board. Please be advised that my knowledge of electronics is quite rudimentary so I apologize in advance if anyone is annoyed by my ignorance.

As can be seen in the pictures below:

the three black 47uF caps to the left of the DOA are a good deal bigger then the other 47uF caps (the bigger blue ones) scattered on the board. In This close up

you can clearly see the difference between the black cap on the upper left-hand side and the blue cap to its immediate right.  They both have the same value and rating, i.e. 47uF/16 volts.

What I'd like to know is what accounts for the difference in size? I am not the original owner of this board but I know that these have not been changed since they have the same glue at the bottom as the other caps in the console.

I do not want to get involved in some audio-foolery discussion about the merits of using such-and-such cap and how some exotic oil capacitors will change my perception of reality and the other silliness that seems to pervade hi-fi audio blather regarding components. However, Yamaha is a multinational corporation with very deep pockets and know-how, and I am sure when they set out to design these mixing boards that they hired what was regarded as the best-and-brightest electrical engineers of the time that they could get their hands on. I am also assuming that those caps are there because the designers decided it was a good idea. Who am I to argue?

In short, I would appreciate if someone could elucidate me on what the thinking might have been and what I should replace these with if they are not to be general aluminum capacitors, a multitude of which I recently purchased to recap the 2 output and 12 input channels of the console.

Thanks you for your time and consideration.

Cheers!

 

[[email protected]]

i might  be wrong but that light blue one in the center looks like its leaking, might be glue ( I haven't got my glasses on)

edit: no it is leaking.

yamaha  is a big corp, and such watches the bottom line. a $0.01  difference per unit cost makes a big difference in the quantity they buy/produce.

replace with panasonic FM

its funny how the smaller but "identically rated" cap has failed

 

[spaceludwig]

Actually, I don't think it is leaking. It seems to be the same substance/glue that's on the bottom of all the 47Uf + caps, including the black ones. None of the 10uF caps that aren't glued have this.

I have bought enough caps to redo the whole console. Do the Panasonic FM caps have characteristics that affect sound, in other words, can I use the ones I've bought? Because if it's a matter of longevity I'll worry about it in 10 years and buy the proper ones then.

Cheers

 

[[email protected]]

if you've already bought them then use them,

panasonic FM's are good caps for audio and rated for 105 degrees. depends how much you spent on your caps you bought, and what caps?

remember this a time consuming process and the risk of lifting traces etc. it might be worth sticking the better caps in to start with,

 

[JohnRoberts]

The size (volume) of electrolytic capacitors have been on a evolutionary development path over the decades where manufacturers constantly try to make them smaller, cheaper, better. In general, all things equal, the size (internal volume) of the caps will track with capacitance x voltage, but when technology changes all things aren't equal any more.

Most of the electrolytic technology changes a few decades ago were to reduce volume, in recent decades the technology focus has been to reduce internal impedance for use in switching supply applications. 

Your two different sized caps could be very similar in specs and performance, just from different production lots or manufacturers. Typically the cap makers use different model series for changes that dramatic. 

JR

Note: bigger is not necessarily better, while i have seen unexpected problems with at least one bleeding edge new technology cap model. Any that have been around for a while and are well regarded should be fine.

 

[spaceludwig]

Thank you all for taking the time to answer.

As per the responses on the other thread I started to identify one of the caps found all over this board, it turns out I bought the wrong ones, i.e. polarized.  Just placed an order with an online site as in this city bi-polar caps seem to be an endangered species (though bi-polar people are ubiquitous and thriving).

The store I returned the wrong ones to said they had bipolar caps in stock at the value I needed. When I arrived I was shown caps the size of garbage cans and  about 8X the price. Multiply that by 140...  I said no thank you and bought a small tube of lead-solder so the owner could feel like he gained some advantage from the transaction.

I don't know if I should start another thread but I was wondering what song/musical piece would be good to use as a reference when tracking changes/upgrades to the console, i.e. I change so-and-so component and can listen to just one or two songs where the whole spectrum of the frequency range is well represented. I remember someone once telling me that live mixers liked to use "You shook me all night long". 

 

[[email protected]]

personally i would choose the same type of music that you are likely to mix / record.  at least similar frequencies / instruments.


what would you use as a reference track to mix against?

 

[spaceludwig]

I think I might have worded myself incorrectly. It's not that I don't have tracks I'm familiar with or like to reference myself when working on mixes, I was more curious about what other people might use for the same purpose simply to expand my horizons, so-to-speak, and discover new material. I remember when I bought some new headphones recently the salesperson seemed to have a CD specifically for this purpose. One piece he played, some samba/jazz pop, had such a beautiful array of instruments that really allowed one to zone in on specific frequency ranges and tones. I didn't have the presence of mind at the time to ask for the name of the track. 

Anyhow, I know this is a technical site. I am more curious about what the people who are building and modding like to use as a reference, if anything. However, this probably deserves a separate thread.

 

[Matador]

The store I returned the wrong ones to said they had bipolar caps in stock at the value I needed. When I arrived I was shown caps the size of garbage cans and  about 8X the price. Multiply that by 140...  I said no thank you and bought a small tube of lead-solder so the owner could feel like he gained some advantage from the transaction.

What size/value were you looking for?  Are you sure you need a bipolar cap?

 

[spaceludwig]

What size/value were you looking for?  Are you sure you need a bipolar cap?

Yes, I do.

As a matter-of-fact I just had an AHA moment while de-soldering the caps currently on the channels.

Those black caps are bigger because they are.... BIPOLAR. That's ironic given the other thread I just started. I feel somewhat stupid but had I not started the other thread nothing would have clicked when I saw the letters BP printed on the side of the black caps. We can even see it on the top of the 100uF cap in the first picture.

I'm going to see if I can modify the order I placed earlier accordingly.........

BTW: the values I need are 10, 47 & 100 uF/16 V

 

[abechap024]

I remember those boards....Master section out of a pm-700.

You can put the polarized ones in if you want. but the BP will probably sound better. I put some pm1000 input transformers on the front of the 2 channel cards that I have and made some really nice sounding preamps

 

[spaceludwig]

I remember those boards....Master section out of a pm-700.

You can put the polarized ones in if you want. but the BP will probably sound better. I put some pm1000 input transformers on the front of the 2 channel cards that I have and made some really nice sounding preamps

That's correct.

You can use BP instead of the regular caps??? Same value? Why would they not have done that in the first place, due to cost? In what way would it sound "better"?

Sorry for all the questions, but I 'm curious.

 

[abechap024]

yes polarized caps and BP caps are interchangeable.  Just take care that you instert the polarized ones the correct way.

From my research and understanding, when polarized caps have a biasing voltage across them they sound fine, but in circuits where there isn't a a biasing voltage or people just want to make sure that the ca owill sound good they use BP.

You can use BI=Polar everywhere and they do tend to sound better. Why people don't use them all the time? Well they are bigger and more expensive (but not that much more expensive)

You can make your own BP capacitors by taking 2 polarized capacitors and connecting the negatives together and then using the 2 positive leads like you would a BP. You can even bias the 2 connected negative leads from the neg rail through a 10k is resistor and make them sound even better (SSL did it that way) Keep in mind though that the capacitance halves when you connect caps in series.

But basically. IF you got BP caps use em!

 

[Matador]

I remember those boards....Master section out of a pm-700.

You can put the polarized ones in if you want. but the BP will probably sound better. I put some pm1000 input transformers on the front of the 2 channel cards that I have and made some really nice sounding preamps

That's correct.

You can use BP instead of the regular caps??? Same value? Why would they not have done that in the first place, due to cost? In what way would it sound "better"?

Sorry for all the questions, but I 'm curious.

It all depends on what the caps are used for.  If they are bypass caps in the power supply they don't need to be bipolar.  If they are used for DC blocking in the audio path you may need them.

Since the values you need are on the big size I'm leaning towards supply rail bypassing, but just in case...

I'm really liking the Nichicon VZ series (high temp, low ESR).  If you need bipolar the EP series is really good.  All these caps should be available in the 25 cent to 50 cents a piece.

 

[spaceludwig]

You can make your own BP capacitors by taking 2 polarized capacitors and connecting the negatives together and then using the 2 positive leads like you would a BP. You can even bias the 2 connected negative leads from the neg rail through a 10k is resistor and make them sound even better (SSL did it that way) Keep in mind though that the capacitance halves when you connect caps in series.

But basically. IF you got BP caps use em!

Are the Biased ones better sounding than the BP ones? Or are you saying the biased ones sound better than non-biased? Because if home-made biased caps sound better than BP I would rather take the time to make them.

 

[abechap024]

I haven't sat down and tested them, but there is a PDF somewhere from the 70s were a respected electronics engineer tests all of them,
I believe the ones connected at the neg terminals (essentially a BP cap) and then biased with voltage through a resistor were the lowest distortion ones.

But if your worried about it and have the extra money, just get BP.

I've often wondered too while a lot of designers/manufactures don't use more BP so it must not be that big of a deal in most places.

 

[spaceludwig]

Ok, I'll stick with the BP's then, thanks for your reply.

I'm going to start a new PM700 thread a little later today as it would be nice to document the process & the progress I make, and also have it archived as a reference for anyone else who might want to undertake this project. I find it incredibly helpful to be able to find sometimes very thorough and detailed info & discussions relating to specific gear.

 

[abechap024]

Yes its also fun for people like me that don't have a pm700 board but we can vicariously go through the process through your pics and documentation