:Greetings,
:I have a Westinghouse 50"s radio with a 20 and 40 uF @150 Volts in a can. Is it way out to replace the 40 with a 50? all at the same volts.
:Is there a general rule when substituting electrolytics up and down? I believe I have read that it is 10% up or down, but not sure if 50 in place of a 40 is to much.
:Thank you,
:Vinny
The tolerance is 20% or greater anyway... so going up is always better. The 1st cap after the rectifier should not go too high because it stresses the rectifier tube so that one should be close to original value and not up more than 20% ... nut the next one after the choke or resistor can go much higher and it's ok.
As has been pointed out, the radios were built to make the most profit, ergo, the minimum of everything that would work. Here, I must disagree with Peter a bit, and say put in the biggest value you can get into the space.
Lewis
I use 100 50 50 10 MFD. Radio seems to like that. Works better with way less low voulme hum.
If you look up any rectifier it will tell you the MAX allowed input cap size.
This is because when the radio 1st turns on the cap looks like a short until it starts charging.
The bigger the cap the longer it looks like a hard load...like a short... the tube will arc over from plate to cathode if the cap is larger than the spec and destroy the tube.
Peter:
When I said "space" I meant physical and electrical specs both.
Lewis
That is bad advice.
As it been pointed out, reading specs from a tube manual will tell you the maximum allowable capacity to be used for a specific rectifier. Never exceed the maximum value, unless you like replacing shorted rectifiers.
Syl
Am I reading right? Are you using a 50uH choke in a PI filter for a PSU?
Syl
Vinny,
You can use a 50uF in lieu of the 40uF without problem, BUT, I would go with a higher voltage capacitor, say at least 160V. My line voltage sits at 123V constant here and rectified I read well over 150V. I like using 200V-250V caps for a good safety margin although 160V would do.
Syl
The inductor (speaker field coil, etc) or resistor before the other cap will reduce the charge time of the cap (T=RC).
I still like to stay as close to the original capacitance (F) values I can. There are reasons why the values that were used were picked, and it is not primarily cost & size - but that plays a part.
The LC filter values are important to filter the proper frequency range, and not be in a resonant situation, as I think was mentioned in the other thread.
As also mentioned, those old caps probably have a wider tolerance than the standard 20% today. Your old caps are worse on low side by now. If you pick a higher cap value, its probably a tighter tolerance than what you had. Today's mfr processes are also much tighter than they were years ago, so a 20% part will most likely be much better than 20%, but you need to account for aging, change with temperature, etc.
Higher cap value, more inrush. Lower cap value, more ripple. There is always a tradeoff.
@Vinny - To answer your question, 47uF is standard these days. You can buy 47uF, 160V 20% cap at Mouser for less than a buck.
Personally, I go with the Vishay/Sprague Atom series made for these applications. They still make the old values. Yours is a TVA1511 Newark has the best price on these - 3 bucks for that P/N.
If in a pinch the 50uF would work, but there may be somewhat of a compromise to the design of your equipment - maybe not.
Dave
I too go along with using values as close to original. But how many times have you encountered the manufacturer's installed caps being much different from schematic. And always higher?
Bill
:Greetings,
:I have a Westinghouse 50"s radio with a 20 and 40 uF @150 Volts in a can. Is it way out to replace the 40 with a 50? all at the same volts.
:Is there a general rule when substituting electrolytics up and down? I believe I have read that it is 10% up or down, but not sure if 50 in place of a 40 is to much.
:Thank you,
:Vinny
With such bad advice, no wonder you don't sign your post.
Yes it is important for all the reason already stated.
The % is worst case scenarios and temperature related.
If the cap going up in value while the radio is hot (which happens in real world) can't damage the rectifier as it is already active. It is at turn on that damage occurs. see explanation in previous post.
Following your "logic", using an 80uF would seem right?
Fine, then that same cap also has an -20/+80% spec. That would make it possibly an 100uF under some condition or worst case scenario, enough to blow the rectifier.
Syl
What is the purpose of this kind of response? If you don't like the guy's post, ignore it. If you want to give different advice, do so. The world will get along fine whether you agree with others or not. Making silly remarks doesn't exactly make you seem intelligent.
As for signing posts, does that make you feel important? If so, it's only to yourself.
I can't let wrong advice and misinformation go by.
If you do, it probably is because you don't care about others and the hobby. As for myself I do care that the right information goes through.
BTW, why don't you follow your own advice and ignore my post? It [i]does[/i] get under your skin eh?
Syl
::If you don't like the guy's post, ignore it.
:
:I can't let wrong advice and misinformation go by.
:If you do, it probably is because you don't care about others and the hobby. As for myself I do care that the right information goes through.
:
:BTW, why don't you follow your own advice and ignore my post? It [i]does[/i] get under your skin eh?
:
:Syl
Thanks, kind words are always appreciated.
Syl
::Older electrolytics often had tolerances of -20%/+80%. That being the case, trying to get very close to the original marked value isn't all that important.
:
:With such bad advice, no wonder you don't sign your post.
:
:Yes it is important for all the reason already stated.
:The % is worst case scenarios and temperature related.
:If the cap going up in value while the radio is hot (which happens in real world) can't damage the rectifier as it is already active. It is at turn on that damage occurs. see explanation in previous post.
:
:Following your "logic", using an 80uF would seem right?
:Fine, then that same cap also has an -20/+80% spec. That would make it possibly an 100uF under some condition or worst case scenario, enough to blow the rectifier.
:
:Syl
A lot depends on how an electrolytic cap is used in a circuit. A cap right at the rectifier should be limited to the tube manual spec. A second filter can be way increased in size. Higher values will usually filter out hum better but larger is size and cost.
Use a voltage rating same or higher than original.
If a person goes by tolerance and uses a cap at upper limit what says the replacement won't also be at the high end?
If original cap was 40 mf use 47 mf as this is the present standard value.
Norm
:Greetings,
:I have a Westinghouse 50"s radio with a 20 and 40 uF @150 Volts in a can. Is it way out to replace the 40 with a 50? all at the same volts.
:Is there a general rule when substituting electrolytics up and down? I believe I have read that it is 10% up or down, but not sure if 50 in place of a 40 is to much.
:Thank you,
:Vinny
:Hi Vinny
:
: A lot depends on how an electrolytic cap is used in a circuit. A cap right at the rectifier should be limited to the tube manual spec. A second filter can be way increased in size. Higher values will usually filter out hum better but larger is size and cost.
:
: Use a voltage rating same or higher than original.
:
: If a person goes by tolerance and uses a cap at upper limit what says the replacement won't also be at the high end?
:
: If original cap was 40 mf use 47 mf as this is the present standard value.
:
: Norm
:
::Greetings,
::I have a Westinghouse 50"s radio with a 20 and 40 uF @150 Volts in a can. Is it way out to replace the 40 with a 50? all at the same volts.
::Is there a general rule when substituting electrolytics up and down? I believe I have read that it is 10% up or down, but not sure if 50 in place of a 40 is to much.
::Thank you,
::Vinny
I certainly don't have to defend Norm, but it should be obvious to you that Norm is quite highly respected around here.
Norm is one of the most knowledgeable and courteous contributors to this form and his input is ALWAYS respected highly.
Trying to impugn his advice is not only pointless but shows how little you really understand.
Please go do something worthwhile...
You are just irritating people and wasting your time here.
.. AND... you are depriving some village of a good idiot.
:Hey..look!
:Now you are really making yourself look dumb as well as disrespectful.
:
:I certainly don't have to defend Norm, but it should be obvious to you that Norm is quite highly respected around here.
:
:Norm is one of the most knowledgeable and courteous contributors to this form and his input is ALWAYS respected highly.
:
:Trying to impugn his advice is not only pointless but shows how little you really understand.
:
:Please go do something worthwhile...
:You are just irritating people and wasting your time here.
:
:.. AND... you are depriving some village of a good idiot.
:
:Hey..look!
:Now you are really making yourself look dumb as well as disrespectful.
:
:I certainly don't have to defend Norm, but it should be obvious to you that Norm is quite highly respected around here.
:
:Norm is one of the most knowledgeable and courteous contributors to this form and his input is ALWAYS respected highly.
:
:Trying to impugn his advice is not only pointless but shows how little you really understand.
:
:Please go do something worthwhile...
:You are just irritating people and wasting your time here.
:
:.. AND... you are depriving some village of a good idiot.
:
:If that's what YOU call defending good people and against improper attacks ... ok
:Defending someone infers that you believe yourself to be superior to that person.
:
::If that's what YOU call defending good people and against improper attacks ... ok
So I defend only that which used to be a pleasant environment until you polluted it... that's all.
Call it what you like....lol
:Just sick and tired of seeing you cowardly no-namers drag down an otherwise nice civil environment.
:
:So I defend only that which used to be a pleasant environment until you polluted it... that's all.
:Call it what you like....lol
:
Then there are the ones who continually provide entertainment. They can always be counted on to respond with either some kind of nonsense to something they disagree with or by an insult to the person who posted it. Two of them were represented in this thread. It is so easy for someone to spin them up it's almost unfair. They can always be counted on to respond to a challenge, no matter how obvious. Sometimes it almost seems as if someone is impersonating them with the intent of making them look foolish.
So thanks again for the good information and the entertainment.
It is always best to aim for the nominal value rathar than rely on the tolerance extremes. Sometimes the extremes can cause problems. GM on a batch of Chevs had this hasppen. Rear axles, for easy in assembly, rely on force fit of axle shaft to bearing race to stop lateral movement. A number of cars were assembled with a batch of axles with minimum bearing surface diameter and maximum bearing ID. The axles on these cars would slip out of the car as there was not enough friction when the two parts were at the maximum tolerance in opposite ways (inside axle smallest, bearing ID largest). Maybe million to one chance that the batches, bearings/axles, would be placed on same cars but it did happen. PL