How do you know it is time to recap?

[sweetbeats]

If you know for sure that the function of the cap is just for filtering (power supply caps) then you can safely up the value and voltage rating.

So up the size and voltage to the max values that will fit in the location on the board? This is where I'm confused. We are indeed talking about PS caps. All the caps that I've found with the same values as stock are in a smaller can these days, so I've got room...so, get the biggest capacitance value and voltage that will fit in the space??? There's got to be a catch...

get a good soldering station

Check. I have a new Antex pencil iron that is working fantastic.

The solder sucker should be ESD safe.

Check...non-conductive plastic hi-temp tip...

Through hole boards are the toughest to remove components and if you can remove them without damaging the pad/etches, you can remove surface mount anything

This is actually going quite we'll. I learned my lesson the hard way and got some excellent advisement on another thread and I'm pulling caps left and right and the traces/pads are left clean and intact.

 

[sweetbeats]

Here's another question...

What is up with the sticky gluey stuff that is holding the caps in on some PCB's???

Is there a good way to loosen it when pulling the caps, and is it neccesary (i.e. can I go without it when putting the new cap(s) in)?

 

[dementedchord]

the glue is from automated insert machines.... as to ps supply caps values anything more than 2x's the original value is most likely a waste...

 

[sweetbeats]

the glue is from automated insert machines

Oh interesting. Okay...So I don't need to reapply the adhesive right? And is there a way to safely soften the adhesive or do you just rip the cap offa there, figuratively speaking?

to ps supply caps values anything more than 2x's the original value is most likely a waste...

Okay...thank you for the help. I'm almost ready to take the plunge then and put in an order, but:

1. Are you talking about the capacitance and voltage values, or just capacitance?
2. If anything roughly in excess of 2x's stpck value presents as a waste, is the converse true then that anything up to roughly 2x's stock value is likely of som benefit?

Ultimately what I am trying to get my brain around is this example:

6800uF cap on my 58 PS PCB...stock can is 40mm x 40mm and that's as big as will fit in that space. Every 6800uF cap I've seen so far is smaller...maybe 25mm x 40mm or 35mm x 30mm. So do I shop for the greatest capacitance cap I can find in a 40mm x 40mm can assuming it is less than 2x the stock value of 6800uF (otherwise I'd be wasting my money, right)?

Thank you again, respectfully, for taking the time to help.

 

[illacov]

The minute you...

Get your MXL/Nady/Shanghai mic home!

Peace
Illumination

 

[sweetbeats]

...............................wha?

 

[illacov]

Oh come come...

...............................wha?

The caps in the MXL mics/Shanghai mics are cheap caps to begin with but alot of them are grossly underspecced.

One infamous one is the capsule capacitor. In their tube mics they usually have them anywhere from a 1000pf 10V to a 1000pf 35V. The junction that this capacitor is on sees up to 135V!

So, we know that simple math tells us the cap will blow. So the minute you get your MXL mic home, you should probably recap that mic or will die in your arms, sometimes when you plug it in for the first time. The only to get it to work at that point would be recapping it.

The solid state mics, improve from replacing that capsule too. It usually is across the two posts for the capsule on the PCB.

Upgrading the cap here will lower the noise usually.

I mean one could simply write down the values of the capacitors on an mxl mic and upgrade them to better values and you should see a better performance.

Every capacitor may not make a huge world of difference but not every mod has been tried on every shanghai mic. You may discover something about yours.

The exception to the rule on this one (there may be others) is the Behringer B1 microphone.
It has WIMA caps in there which are extremely expensive compared to what the Chinese normally use to manufacture their OEM mics.

Peace
Illumination

 

[sweetbeats]

Okay...I'm with you...

Sorry for being so daft , I was so focused on my questions that I put in my post just prior to your first post that I totally missed that you were respondingto the original topic......that's funny.

Okay...huh!

Makes me want to open up my Studio Projects mics...they are a product of the 797 factory. I have a C1 and two B3's...all solid state but...

Thanks for the intrigue.

 

[dementedchord]

if the caps you find have the short solid tabs on the bottom then you might have to go with a larger value just to get it to fit... but if they have long tails like resistors do then anything will fit... dont sweat the glue stuff...

 

[sweetbeats]

This is driving me nuts...

Trying to find a cap to replace the aforementioned 6800uF 50V cap...

The lead spacng is about 19mm (though the original cap and the holes in the board are perpendicular blade type slots, so if a new cap has pins anything from about 16mm ~ 20mm will work, the case size is 40mm x 40mm...

I want a 105 degree cap with 20% tolerance.

I've checked Newark, Allied, Mouser and Digikey...the engines on these sites either make lead spacing or case size a pain to determine, and in the end I'm having trouble getting all the parameters to fit.

This is the first step...I'm hoping caps of smaller values will be easier to select.

Can anybody help?

 

[dementedchord]

105degree caps is a real good idea... 20% is fine for supply filters.. when you get to things like the eqs in the board ya might want to go to 5% if ya can....

 

[evm1024]

Here are some options

This cap is 50 mm tall and if that would fit the available space I would use it.

http://www.mouser.com/Search/ProductDetail.aspx?qs=AoqyJxclAxghGW%2borEXkGw==

If you don't have 50mm of room you could try:

http://www.mouser.com/Search/ProductDetail.aspx?qs=0Kodg4Py2Q7rSUn%2b0qzmyg==

It has snap-in leads so you may have problems with the mounting holes....

I was looking for 6800 uF 50 to 63 v, 105 degree caps.

Staying at the original cap value (6800 uF) is OK (going up to 10,000 uF also would not be a problem - this is not a timing circuit), going from 50 to 63 volts just gives a little more longevity. You will stress the cap less at high line voltages. going to 105 degrees gives much more longevity. The cap is of a more robust design.construction to start with.

Hope this helps.

--Ethan

 

[sweetbeats]

Thanks, Ethan!

I'll check tonight to see if I can squeeze 50mm in there...

On a standard through hole raqdial mount cap if the lead spacing isn't in the range of the holes in the PCB then its just time to bend the leads until they fit right?

It has snap-in leads so you may have problems with the mounting holes....

Okay...yeah the whole snap-in thing was confusing me...its just a diffrent terminal shape and isn't as forgiving to being modified to fit (i.e. bending the leads) right?

 

[evm1024]

Thanks, Ethan!

I'll check tonight to see if I can squeeze 50mm in there...

On a standard through hole raqdial mount cap if the lead spacing isn't in the range of the holes in the PCB then its just time to bend the leads until they fit right?



Okay...yeah the whole snap-in thing was confusing me...its just a diffrent terminal shape and isn't as forgiving to being modified to fit (i.e. bending the leads) right?

Right on both - you can make snap in work in this size (plenty of room) by drilling new holes to fit. I would leave the original intact and just drill through the copper traces where needed. It looks like the PCB has large copper foil areas for this cap. That would be my second choice - I would look for a direct replacement first - even with bending the leads.

-Ethan

 

[sweetbeats]

105degree caps is a real good idea... 20% is fine for supply filters.. when you get to things like the eqs in the board ya might want to go to 5% if ya can....

So I was figuring up pricing to recap my whole Tascam M-520. I was on the Mouser site looking at 22uF 25V caps. I tried to find 5% tolerance units, but they are all no less than 20% tolerance. So I started looking at the functions of some of the different caps. I started with the eq section. All the caps in the eq section are non-electrolytic except for a 22uF 25V "feeder cap" (I think I'm using the right terminology...it is at the head of the input stream into the eq section). Or is it a "smoothing cap"?

Anyway, is it critical that this one be 5%, and is there any advantage to upgrading the value of this cap? I do plan on getting 105 degree caps.

 

[evm1024]

Nope

So I was figuring up pricing to recap my whole Tascam M-520. I was on the Mouser site looking at 22uF 25V caps. I tried to find 5% tolerance units, but they are all no less than 20% tolerance. So I started looking at the functions of some of the different caps. I started with the eq section. All the caps in the eq section are non-electrolytic except for a 22uF 25V "feeder cap" (I think I'm using the right terminology...it is at the head of the input stream into the eq section). Or is it a "smoothing cap"?

Anyway, is it critical that this one be 5%, and is there any advantage to upgrading the value of this cap? I do plan on getting 105 degree caps.

That cap is a coupling cap that is intended to block DC from entering the EQ section. I imagine that it is a bipolar electro (NP). The value is not too important as that it just needs to be large enough to pass the lowest frequencies. The 20% is built in to the value selected.

Using 5% caps is desirable in fixed EQ and timing circuits. The boards EQ are not fixed so using 5% just means that each channels >>range<< is more alike than not - not better.

--Ethan

 

[sweetbeats]

Hm...okay. That is helpful. Thank you again.

It is C12 on the Input Ampl. PCB...its a polar cap though...it sources from the EQ ON switch...I think I see though...when you say "coupling cap", it couples to ground right? Or is it "coupling" the input signal and the output of the circuit in which it resides? And if it is the former it does that "coupling" to ground through the EQ ON switch?

Anyway, if it is designed to filter DC, which is noisy, and it is going bad, then that (and all the other dern caps) could for sure be contributing to the roar, huh...

I know the mixer was manufactured in 1988, and I think it spent the last 3 years unused in a storage unit, though I know it was dry as there is not a spec of rust anywhere on the whole mixer, but I'm sure 3 warm summers on 20 year old caps was not the best thing.

Okay. Well I will replace with like values but I'll source 105 degree caps then.

Its amazing. There are 722 caps on the M-520, and over a quarter of them are 22uF 25V (190 to be exact). That will cost me around $10...just 10 bucks! And it is likely to make a big difference...this is exciting.

 

[evm1024]

I got a chance to look at the schematic. C12 is the coupling cap that blocks any DC offset from U7's output (pin 7) and couples it to the input fader and the sw PCB (the output if you will)

Take a look at U5(1/2). It also has a 22uF cap on its output (C21) that does the same thing when not using the EQ section.

U5 (1/2) takes its input through C25 - it outputs on pin 1 to the EQ section vr2 and at the same time through C21 to the EQ/noEQ switch. The EQ section takes the signal and does the EQ and output the EQed signal on pin 7 of U7(2/2) which goes to the EQ/NoEQ switch through C12. The EQ/noEQ switch S6-3 selects which signal to pass (Eq or non-EQ) to the next subsystem.

--------

This beggs the question - does the noise/hiss you are chasing change when you select EQ vs non-EQ? If the noise is the same (with flat EQ settings) then it is not generated by C12. It would be unlikely that C12 and C25 make the same noise exactly....

To chase the source of the noise you will need to see what makes more noise that some place else. It could be in your driver amps for example. I would expect the mic pre at full gain to be more noisy that line in.

I'll talk about opamps in your other thread ....

 

[sweetbeats]

Some progress

To save money overall I'm trying to purchase as many caps at one time as possible to recap my 58-OB and M-520 from Tascam...taking advantage of combined shipping and quantity price-breaks...

Some of this is pretty straight forward thanks to the advisement in this thread, but here are some more questions as I peruse and load my carts at Digi-Key and Mouser:

1. In general I'm shooting for 105 degree caps on everything. Good idea right?
2. Am I correct that mixing and matching caps of different manufacturers is not an issue?
3. I seem to be gravitating toward the Nichicon caps...their offering range is filling more needs than the Panasonic caps, and they have caps specified for audio circuits, the KT Series. Is this just hype, or is there some benefit to these caps for circuits passing audio? unless I hear otherwise I am selecting those for any circuit carrying audio, and the VZ Series for applications in logic or control circuitry or power supplies. Is that logic sound?
4. In general I am oversizing caps in power supplies (either a nominal increase in capacitance and/or voltage rating), but for everything else I'm selecting direct replacements spec-wise. Is that logic sound? In other words, are their known general rules of thumb for varying from the manufacturer's specification when recapping? I am conceptually aware of the monkeying you can do with eq circuits and such, but I'm not interested in that at this stage, and the eq circuits on the M-520 don't utilize electrolytic caps anyway...I'm just interested in those tried-and-true deviations from spec that apply to the likes of the mid-80's gear from Tascam and such.
5. Since I'm planning on upgrading the opamps at least on the M-520, will that effect the demands on caps in those circuit paths? I'm thinking along the lines of opamps that draw more current and what that might do to effected caps...do I deal with this now or deal with it when I get to the opamp upgrade (note: I do recall that I will likely need to/want to add coupling caps to new opamps)
6. I'm having a tough time finding a couple-three caps: 0.22uF 50V 10% (used in position C4 on the Control PCB of the 58-OB...nothing in 10% in that capacitance range...), a 1uF 16V cap (used in C83 on the Monitor Amplifier PCB of the M-520...oddly enough the parts list specs 16V but the schematic shows 50V...can't find anything less than 50V in a 1uF cap...), and 1uF 50V 10% caps (used in positions C1 and C2 on the Function A PCB on the 58-OB...nothing in a 105 degree cap in that spec, only 85 degrees...just go with 85 degree caps?) I'm looking for help finding these seemingly obscure caps, or advice for alternate spec caps...

This is cool. Thanks again, everybody!

 

[sweetbeats]

Biting the proverbial bullet...almost

So I'm getting ready to submit an order to Digikey for supplies to recap the power supplies for my Tascam 58 and my Tascam M-520. Below is what is spec'ed and the Digikey part number I've preliminarily chosen to replace the stock cap. I've not settled on one brand/series of cap. Don't know if that is wrong or not, but I basically looked for long-life caps in the 105-degree range either Nichicon or Panasonic, and on the larger caps I'd try to up the voltage rating a notch. So I selected whatever series fit the bill for the particular cap (within reason as far as proper application...I had to do some reading to get a better idea of what series were geared for what and I may not be getting it right yet...)

All comments welcome...pleeeez.