How do you know it is time to recap?

[sweetbeats]

Hi folks.

I apologize in advance due to the fact that, at my skill level, I am much more likely to be a taker here than a giver.

I started a thread about recapping over in the Analog Only forum thinking it might be more appropriate over here, and another member reinforced that idea, so here I am.

The original thread is here.

As you'll get from the original thread, I am comfortable with a soldering iron, have a pile of mid-80's Tascam gear that I intend on treating right for many, many years. I want to keep it going and going well. I have heard about the degredation in performance that bad caps can cause, not to mention the potential damage. I especially want to avoid the latter. So in the spirit of good stewardship to my gear and my craft I'm trying to evaluate if I get into recapping now, and where to start.

Thanks in advance for the time you expend in this newbie!

 

[Whale Bone]

From what I've read and been told, I would agree with an early post in your other thread that says if you've cleaned your pots, switches and faders and they still pop and/or scratch, then you probably need to recap (as long as the pots, etc. are really clean and good). I've also been told told, when asking about a mid to late 80's Soundcraft 200B, that recapping the electrolytic caps is likely a good idea. I haven't yet, but I would like to try a few channel strips now that I've built a work bench. My dilemma is that the mixer sounds good, but I do have some scratchy faders and some channels that are the same revision (I've got 5 different rev's across all of them) do sound different. So, leave it alone and just set the gains differently or start recapping? Sorry, I guess I've posed the same question in response, but I'm leaning towards recapping, but doing it at my leisure instead of immediately. Note: Someone might've mentioned this, but the ones you care about replacing are generally only the electrolytics, the can-shaped ones.

I'd say if you have the time, skills and can risk screwing it up, go for it on a few channels/groups/auxes, etc. and see if it helps. Then decide from there.

The other consideration in my case is that many people advocate using larger value caps as you can fit them in the same foot print as 80's-era and get more low-end. Doing this eliminates your existing channels as controls for the experiment and also risks losing some of the flavor of the original design.

One last thought is that many nicer, low-ESR caps have one-time surcharges when ordering, so bulk is good, but that makes experimentation more expensive.

The last two are where I'm currently stuck, but as a bassist primarily, I'm very tempted to go with larger value caps when I do this.

Hope this helps in some way.

 

[sweetbeats]

A sincere thanks for your post, and it is helpful...getting somebody else's thoughts and ponderings, even though some may be inconclusive, is helpful.

I realized as I read your post that (duh) I have 8 spare channel PCB's for my Tascam M520. Could I post some links to some hi-res detailed pics as well as the schematic for for the channel PCB and get some recommendations on component replacement?

I could do two cards...one with just cap replacements, and the other with caps and IC replacements if there are solid recommendations that would be known improvements...?

Thanks again...

Do larger value caps require more power from the source?

Any thoughts on my question about a new soldering iron?

What temp works good for this kind of work, and what solder wire guage is recommended?

 

[pianodano]

If it was a Leslie, you'd know. Thunderstorms is what we used to call it.

 

[sweetbeats]

If anybody would be so graciously inclined, I have scanned and zipped pertinent schematics and parts lists for my M520 and would love to know what should be replaced and with what.

The .zip file is located here. Its about 3Mb.

 

[stevieb]

When I'm riding along with the top down, and my hair is blowing all over the place- I know I need to re-cap- the old one obviously blew off!

Couldn't help myself...

 

[sweetbeats]

Um...

I think my mother-in-law had a recap a couple weeks ago...damage due to sticky food...I guess that was a crown.

You guys are nuts.

 

[sweetbeats]

Seriously...anybody?

Maybe I'll just wait awhile...maybe I'm being impatient.

1. Do I replace caps with the same value caps or is there an art to selecting other values for a desired result?

2. Any IC replacement recommendation for the M520? Somnium7 are you out there?

I'm generating a parts list for my 58 as well...where is a good place to by capacitors?

 

[dementedchord]

1st as to where to buy??? i like digikey... prices are good seems like it's always in stock (or i've been lucky)... good selection...

as to the caps... if ya look at the parts books you would hopefully realize that they tend to come in ranges... ie. it goes from say 11mf-22mf-33mf-47mf and on... so you can think of useing the next step... but it may not help that much unless that particular one is in the audio path... also there's a temp rateing ... the higher temp is a good thing they tend to last alot longer and dont drift as much...

as to what chips to use... looks like most of whats in there are 4556's tl072's and such... there are way better chips available but before i would recommend some specifics i'ld want to see an actuall schematic... board layouts and parts lists dont work for me... i need to see what that one is used for... ya dont want to just add say the fastest op-amp available if there's a chance that it's used as say a line driver where current handling is more important than speed... get my drift??? also if/when you change out these op-amps ya should consider adding extra decoupling caps at each opamp...easiest way is to jumper a cap between pins 4+8 on dual opamps...

 

[sweetbeats]

dementedchord...thanks!

Digikey...okay.

as to the caps... if ya look at the parts books you would hopefully realize that they tend to come in ranges... ie. it goes from say 11mf-22mf-33mf-47mf and on... so you can think of useing the next step... but it may not help that much unless that particular one is in the audio path... also there's a temp rateing ... the higher temp is a good thing they tend to last alot longer and dont drift as much...

Okay. I will likely have some specific questions as I get into this, like stating what I'm replacing (cap spec and application) and what the replacement options are. If I can get some feedback on what the better choice is among the options I will learn from that and be able to apply that to future replacements. I hope this works and that I will get some said assistance. Be kind...I'm a rookie.

as to what chips to use... looks like most of whats in there are 4556's tl072's and such... there are way better chips available but before i would recommend some specifics i'ld want to see an actuall schematic... board layouts and parts lists dont work for me... i need to see what that one is used for...

Got it. I will, at some point, scan in the schematics and post a link.

if/when you change out these op-amps ya should consider adding extra decoupling caps at each opamp...easiest way is to jumper a cap between pins 4+8 on dual opamps

I remember reading somewhere about decoupling caps, but I can't find the reference and I've forgotten what function that provides. Can you explain?

Thank you so much for the information.

 

[sweetbeats]

I'm making a catalog of the electrolytic caps on my 58 and...

I noticed that there are many caps that have the same capacitance and voltage rating, but there are additional bits that are different. Can somebody explain those differences to me?

Like look at these 3 caps...All the same capacitance and voltage rating, but the percentages and that pesky "(B. P.)"...what is that?

10uF 16V
10uF 16V (B.P.)
10uF 16V (B.P.) 20%

 

[dementedchord]

most caps have side that is high voltage and the other is low... at least relitively to each other... make sense??? in otherwords... they're polarized... also a cap can be rated within certain tolerences... some in big guitar power supplies can be +20/-50% ??? wow thats a lotta tolerence ya got there dude... in things that are high speed circuits or in tone controlls i use 5%... which is bout as tight as it gets for caps...

so your 3 caps there are ...

10mf 16V (polarized)
10mf 16v bp (bipolar or non polarized)
10mf 16V bp 20% (bipolar and at a 20% tolerence)

 

[sweetbeats]

Dementedchord,

Awesome response...thank you...I'd add to your chiclets but I'll have to wait until I "spread it around" some more.

So is there any advantage to going with a tighter tolerance cap if there is one that is originally spec'ed at 20% say and going with a 5 or 10%?

 

[dementedchord]

the advantage is going to come in when you start doing the channels in that 520... especially in the eq's... a tighter tolerence here will mean better matching between channels... in fact what ya may want to do is go through each channel and pick the one that you like the best... they all will have drifted some but which way and how much??? so when we get the one you like the best meter the caps and then build two channels... one with the original spec the other the one you liked... now you can test them against each other and decide which way to go with the rest.... make sense???

 

[sweetbeats]

Makes perfect sense. Thank you again.

So am I right in assuming that the downside to using tighter tolerance caps is that they cost more?

so when we get the one you like the best meter the caps

And when you say "meter the caps" you are talking with a good quality capacitance meter (like my Fluke 85?)...pull one leg of the cap and measure away?

 

[dementedchord]

And when you say "meter the caps" you are talking with a good quality capacitance meter (like my Fluke 85?)...pull one leg of the cap and measure away?

yep... wish my fluke79 had cap testing...

 

[Dr ZEE]

Fluke 80 Series Digital Multimeters (that is for "III" )

DCV Maximum Voltage: 1000V

Accuracy: Fluke 83 III: ±(0.1%+1)
Fluke 85 III: ±(0.08%+1)
Fluke 87 III: ±(0.05%+1)
Fluke 87/E: ±(0.05%+1)

Maximum Resolution: 0.1 mV

ACV Maximum Voltage: 1000V

Accuracy:
Fluke 83 III: ±(0.5%+2)
Fluke 85 III: ±(0.7%+2)
Fluke 87 III: ±(0.7%+2)
Fluke 87/E: ±(0.7%+2)

Maximum Resolution: 0.1 mV

DC Current Maximum Amps: 10A

Amps Accuracy:
Fluke 83 III: ±(0.4%+2)
Fluke 85 III: ±(0.2%+2)
Fluke 87 III: ±(0.2%+2)
Fluke 87/E: ±(0.2%+2)

Maximum Resolution:
Fluke 83 III: 0.01 mA
Fluke 85 III: 0.1 µA
Fluke 87 III: 0.1 µA
Fluke 87/E: 0.1 µA

AC Current Maximum Amps: 10A

Amps Accuracy:
Fluke 83 III: ±(1.2%+2)
Fluke 85 III: ±(1.0%+2)
Fluke 87 III: ±(1.0%+2)
Fluke 87/E: ±(1.0%+2)

Maximum Resolution: 0.1 µA

Resistance Max Resistance: 40 MW

Accuracy:
Fluke 83 III: ±(0.4%+1)
Fluke 85 III: ±(0.2%+1)
Fluke 87 III: ±(0.2%+1)
Fluke 87/E: ±(0.2%+1)

Maximum Resolution: 0.1W

!!!! Capacitance 1 nF-5µF !!!!

Frequency 0.5 Hz to 200 kHz
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Happy "matching". ... don't forget having fun doing all that.

BTW, I'd rather restrain myself from commenting on the whole idea of "matching" electrolytic capacitor's values to somehow match the channels ( making them sounding the same as the one that sounds best (or the one that you "like it best", what ever that may mean )., heh heh, I must be missing something here completely. Very interesting "idea" indeed

also, some rant on Fluke Meters - 80 Type, Models and Series @eBay, this is just in case as I don't know which "fluke" exactly we are talking here, not that it really matters in this case...

**************
***********************

one more little thing.

Maybe I'll just wait awhile...

I'd say instead of "waiting", instead! and if you actually do have time for something else, then get yourself couple of prototype breadboards, get some basic test equipment, get some parts (new, old, used - as many and different kinds as you can get): transistors, opamps, cap, resistors etc. Then surf on the internetnet for info , start putting together some basic audio-related circuits, then experiment something around, measure things, test components, change values, try different types (including trying out tested-BAD components and things like that, so you really know what happens when this or that goes "wrong" or "dies") etc etc - learn some basics about components, circuits and how they work and what happens when you change this or that. You may be very surprised by "findings". You really need this if you really care about your precious gear and the consequences of what you are about to do to them
But you don't have to, of course. As I've said before, it's all great as long the "doctor" is busy and happy

/respects

 

[altitude909]

Electrolytic caps failing in a power supply (i.e. the really big ones) will manifest itself in a hum. PSU caps ("smoothing" Caps, they filter the ripple out of the DC after being converted from AC) are always the ones to start with since they deal with higher currents and will be the first to go.

Another important thing to understand with lytics is how they are rated voltage wise. The voltage rating is only related to the MAX voltage the device can withstand, so really when recapping you can use anything the same rating or higher (NEVER LOWER, they will blow). The catch is that the higher the voltage rating, the larger the cap. This generally has no bearing on the low values since they are all very small physically and rated for high voltages but larger uF values, it will be can be an issue depending on what else is around it. It is always very good practice to double check the case size/lead spacing of what you are buying vs what is there on the board.

The big electronic suppliers in the US are Mouser, Digikey, Allied, Newark. Between those four you should be able to find just about everything. I have had good luck finding the odd value stuff at:

http://www.surplussales.com/Capacitors/CapacitorsAll.html

 

[sweetbeats]

Dr. ZEE, altitude 909 et al,

THANK YOU for the replies. All very helpful.

Dr. Zee:

also, some rant on Fluke Meters - 80 Type, Models and Series @eBay...

I think I knew what I had before reviewing the said "rant", but now I know for sure and better understand what is what. Mine is a Series-1 85 (with a dying screen )

I'd say instead of "waiting", instead! and if you actually do have time for something else, then get yourself couple of prototype breadboards, get some basic test equipment, get some parts (new, old, used - as many and different kinds as you can get): transistors, opamps, cap, resistors etc. Then surf on the internetnet for info , start putting together some basic audio-related circuits, then experiment something around, measure things, test components, change values, try different types (including trying out tested-BAD components and things like that, so you really know what happens when this or that goes "wrong" or "dies") etc etc - learn some basics about components, circuits and how they work and what happens when you change this or that. You may be very surprised by "findings". You really need this if you really care about your precious gear and the consequences of what you are about to do to them
But you don't have to, of course. As I've said before, it's all great as long the "doctor" is busy and happy

I absolutely love the suggestion...the crux is the time-factor "for something else." Time is pretty short these days and for the forseeable future. I am the kind of persone that really likes to understand what it is that I'm doing and not just paint by numbers, but It would be a very long time before I'd get to some work that may preserve my gear if I were to experiment...I realize the dichotomy here is that the experimentation may help keep me from killing my gear, but that's why I'm trying to understand the different cap nomenclature and some of the theory behind the functions served by the differing values, and also what tried and true upgrades or replacement conventions are standard fare...still painting by numbers but with some trusted choices built in.

Altitude909:

Electrolytic caps failing in a power supply (i.e. the really big ones) will manifest itself in a hum. PSU caps ("smoothing" Caps, they filter the ripple out of the DC after being converted from AC) are always the ones to start with since they deal with higher currents and will be the first to go.

So recapping the PSU would be the best place to start in your opinion?

Another important thing to understand with lytics is how they are rated voltage wise. The voltage rating is only related to the MAX voltage the device can withstand, so really when recapping you can use anything the same rating or higher (NEVER LOWER, they will blow). The catch is that the higher the voltage rating, the larger the cap. This generally has no bearing on the low values since they are all very small physically and rated for high voltages but larger uF values, it will be can be an issue depending on what else is around it. It is always very good practice to double check the case size/lead spacing of what you are buying vs what is there on the board.

Okay. Is there sort of a divide in the capacitance value what is considered a low value vs. a large value?

 

[altitude909]

So recapping the PSU would be the best place to start in your opinion?

Yes.

Okay. Is there sort of a divide in the capacitance value what is considered a low value vs. a large value?

Filter caps are always on the large size capacitence wise and they are usually in the hundreds to thousands of uF. The larger the current draw, the larger the smoothing cap.