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having problems finding capacitors for first re-cap

Debassige

Debassige

Well-Known Member
I'll start off by listing what I'm looking for

200uf-50v (axial)
200uf-10v (radial)
5uf-15v (radial
50uf-50v (radial)
50uf-25v (radial)
1000uf-50v (radial)
2000uf-100v (radial)

the problem I'm having is trying to locate exact matches. I've used Digikey, Mouser, Parts Express, Parts Connexion.

Is there a rule of thumb as to how much bigger or smaller I can go as far as specs (eg. 47uf as apposed to 50uf, 16v instead of 10v, etc..). I saw a thread where member Fred longwoth says not to use higher value or voltage electrolytics, which is why I'm trying to match specs.

I'd like to buy from one source and I would like to buy the same brand.

50uf are hard to find, 47uf not so much, 2000 hard, 2200uf, not so hard

One last newb question, polarized vs non. Can I assume unless the part says non-polarized, that it is polarized? (all the capacitors i need are polarized).

if it helps any I'm recapping a yamaha TA-30 guitar amp.

I think in the end I'm looking at buying from many different sources and different brands.

Any help or any other sources would be greatly appreciated :yes:
 
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I BELIEVE that unless the cap says non-polar, it will be polarized. Somebody please tell me if that's not so.

You can go up in voltage a bit without worry (16V should work as a replacement for a 10V cap), but don't try to go crazy and get the highest voltage rated cap you can get. I'd say try to get the right voltage, and if it's not available, go to the next higher one. I don't think there's any situation you should put in a lower voltage valued cap.

As far as the capacitance...I think you really want to keep it the same. I'm curious as to others' responses to the 47uf replacement for the 50uf. I don't know how much wiggle room there is... I've heard Fred say anything but the exact value could cause oscillations (bad).

If the s**t really comes down, you can always wire multiple caps in parallel to acheive your desired capacitance using the following relationship, where Ceq is the equivalent capacitance of all the capacitors:


fa34ce461e6988fd973081401cc9790c.png
 
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I would modernize

I would go with the modern equivalents myself.

Those old parts are +-20% aren't they? Stay within your tolerances and anyone who says it has to be better is building it to their own specs, not the manufacturers.

Which is all good, but, you just have to recognize the difference. If you need it dead on for your enjoyment, then do it. It might sound better!

I still remember after my first few service calls telling my boss how tricky it was to get this product properly aligned on the oscilloscope. He was like, what specs are you using? The ones in the book or the 'Dan' specs? Hah, he knew I was trying to get it dead in the middle, not to the published spec.

And, a couple of extra volts capacity should be fine.

I just looked up the amp, is that the 70's one shaped like a triangle?

Way cool looking.

http://www.grouseguitars.com.au/sold/yamahata30amp.htm has a good pic

I do like Yamaha equipment. They always build solid stuff.
 
Get the correct capacitance (mF) but the voltage can be anything that is >= the value you are replacing. That should make it easier. Also, replace the axial with radial where needed as there are less and less axial caps out there. You can make the radial work as replacements in 99.9% of instances.
 
The values you're quoting are plenty close enough. Actual manufacturing tolerances are much wider than that. I've heard -0/+50% is not unusual.

As far as voltages, as has already been stated you can go up, but not down. Replacing a 25v with a 50v is no problem at all.

Btw, johnnm, I think you might have your formulas reversed. I think the one in your post is for capacitors in series. Oh, wait, your formula is reciprocals and reciprocals. Whow, that's doing it the hard way! In parallel they simply add. Iow, a 10uf in parallel with a 20uf is 30uf. Much easier math!
 
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I've been buying lot of caps lately...

Radial and axial makes no difference.. unless it is for caps on top and it's an astetic reason..

As far as voltages, No problem to go with a higher voltage. Just don't get any that are less voltage.

I've had to go with 4.7mfd instead of 5mfd. This happens, and like mentioned, the tolerances will keep you in the park like that.

Also, I've found that the electrolitics that were polerized said so on digikey. I've found that if they are non polerized they don't say anything.
 
Afaik, modern caps tend to be smaller than their older brethern due to advances in technology. But, still, higher capacitance and or higher voltage tend to make the cap size larger.

Using too much/too little capacitance could disturb the circuit, too much voltage and or capacitance could manifest a physical sizing issue.

I'd stick to the closest value of capacitance, but I'd go up one or two steps in voltage if it were available and will fit. Seems I recall reading some companies pushed the voltages fairly close to the factory/OEM cap ratings.
 
johnnm said:
If the s**t really comes down, you can always wire multiple caps in parallel to acheive your desired capacitance using the following relationship, where Ceq is the equivalent capacitance of all the capacitors:


fa34ce461e6988fd973081401cc9790c.png
Click to expand...

Caps in parallel add up directly (Ceq = C1 + C2 + .. + Cn), when they're in series they follow inverse of the inverse sums rule (1/Ceq = 1/C1 + 1/C2 + .. + 1/Cn).

It's the reverse for resistors :)
 
Series circuit
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Uses this equation.
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and

Parallel circuit
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Uses this equation.
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thefragger said:
Caps in parallel add up directly (Ceq = C1 + C2 + .. + Cn), when they're in series they follow inverse of the inverse sums rule (1/Ceq = 1/C1 + 1/C2 + .. + 1/Cn).

It's the reverse for resistors :)
Click to expand...

My bad! [Insert embarrassed smiley here]
 
thanks for all the info. i guess I was just a little frustrated thinking I could go to one source and find exactly what I needed.

I'd like to do a bit more DIY on some of my gear, I have an AU-519 that needs recapping so I thought I'd start with something a little less involved and go from there. Odd thing though, I aquired a schematic/parts list for my amp and none of the caps match the parts list?, maybe it was recapped before (looks original).

The amp is indeed the "V" shaped (all I need now is a "flying V" guitar), not having a guitar or even knowing how to play I essentially bought it on looks, and price, alone. It has the flat membrane Yamaha speaker which I'm excited to hear someday soon.

Thanks again for all the help
 
If there's any mention -- or way to find out -- tolerances of the originals that will help, wouldn't it?

E.g., say you have a 200uF ... various tolerances are possible, but +/-20% is common... in which case wouldn't a 220uF (more common value) work? Maybe it'd need to be a +/-10% ?
 
It is not true that you can go up in voltage on an electrolytic capacitor without at the same time altering the performance of the circuit.

Let me put this another way. You have some latitude as far as increasing the voltage, but nowhere near as much latitude as is commonly discussed on the Web.

Here's a thought experiment. You are replacing a 100uF/10v capacitor used in the regulator section of a power supply board on a late-seventies Pioneer receiver. You are having trouble finding the correct value, so you use a readily-available 100uF/50v device. Nearby, there's a 220uF/16v part, which you replace with a 220uF/50v cap. In fact you replace eight parts with devices that have voltage ratings from 3 to 5 times as high as the originals.

Then you turn the equipment on, and you find that the power supply isn't working quite as you had hoped. For one thing, every now and then one of the regulator transistors oscillates!!! This phenomenon comes and goes.

Why is this happening? Here's why. When you hit an electrolytic capacitor with a polarizing voltage, the electrolyte forms. If you hit it with a polarizing voltage considerably lower than it was designed to sustain, it will often not fully form, and so the capacitor -- especially if it is used for power supply applications -- will not function at the extremely low-impedance state that you are hoping for.

This characteristic does not afflict film caps, just electrolytics. For this reason, on major power supply recaps, I strongly prefer devices with voltages ratings at, or only slightly above, the original values.

Fred
 
Interesting

So,

now you have it,

you have heard from both camps.

The ones that believe capacitors are pre-formed at the factory as the manufacturers claim. (For the last 3 decades)

And the ones that have very little faith in the consistency of the product.

So, you will have to decide on your own which way you want to go on this.

For what it is worth, I would not replace 10v caps with 50v caps unless I was in a tight. That is 5 times the voltage.

Would i do it if that was the only part I had? Without a doubt and I would never change it back.

You can also go with the camp that would re-form capacitors before they use them.

And, lets not even get into the brand of cap and what it is made out of! That is a much deeper hole we could fall into.

Have fun with your project,

Dan
 
I think it is a case of 'use your common sense'

A couple of years ago when re-capping my amp, I believe I made a mistake when I fitted 4 x 100uf 63v capacitors in place of the original 4 x 100uf 35v. They certainly seemed to work OK as the applied voltage is around 33v. But after doing some checking here and elsewhere about electrolytic capacitor voltages I decided I wasn't happy, so I changed them for 4 x 100uf 35v replacements as they were originally. I can't be sure if the 35v ones work better than the 63v ones, however, I was happier having made the change after I found out how electrolytic capacitors work, and why their voltage ratings are always specified on schematics.

Just my 3 ha'pence worth.

John
 
Would it be bad to install caps that are 'one step' up in voltage rating? ie 20V or 25V replacement for a 16V part?

Or is it more of a ratios thing, where an up from a 100V to a 110V part isn't comparatively as large a jump.

... does this mean I'll have to re-recap everything? :tears:


Philip.
 
thefragger said:
Would it be bad to install caps that are 'one step' up in voltage rating? ie 20V or 25V replacement for a 16V part?

Or is it more of a ratios thing, where an up from a 100V to a 110V part isn't comparatively as large a jump.

... does this mean I'll have to re-recap everything? :tears:


Philip.
Click to expand...

There is absolutely nothing wrong with going up a step in voltage.
 
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