Better explanation of how and when higher Temp Caps Payoff

[Onelasttime]

Ok so I am recapping a radio that is going to live a nice gentle life in my new shack in my new to me home. Since the unit will not be in hot car or see any vibration baring an earth quake I could not see springing for heavy duty computer grade or higher 105°C caps. I did go for high end Audio caps that have a low ESR rating but are only 85°C rated. I did doubled the voltage rating of all the caps and due to increases in capacitor technology and electrolytic technology the capacitance on every cap is at least 3x-10X greater than OEM on the smallest caps and the larger caps the increases is anywhere from 5X to 100X greater. I made sure to match the size of the old caps in terms of physical dimensions because this board has more caps than Jimmy Carter has liver pills! In a lot of cases the size bellow was too small in terms of capacitance and the next step up was a HUGE step up. The radio in question was purchased in 1998 when my first some was born so a lot has improved with electrolytic capacitors.

So in the real world assuming you never see harsh conditions do the 105°C caps really pay off over the 85°C caps? Does the quality of the cap's electrical properties pay off over just the temp rating? I could have used dirt cheap 105°C caps or 85°C premium audio grade caps or could have gone for 105°C audio grade caps. I chose the the 85°C premium audio caps. They where very affordable and had really good electrical properties on the white paper's.

They are name brand by the way and not made in China I just do not want to mention the name and get into a brand war debate.

I would though like to understand better what one actually get's when they upgrade to 105°C caps and if it is always worth it in a CB or Export radio?

I would like to understand better what you get by increases the voltage rating and capacitance in terms of real world pay off in the field. I understand that many times the 6.3V and 10V caps where far too close to the operational limit of the design and failed due to that. Outside of that do you get any more durability or performance cushion by increasing the voltage or capacitance of the cap's beyond the OEM's recommendation.

The above assumes the fidelity of a CB or Export radio is such that no change in capacitance or brand specific electrolyte will have a noticeable effect on fidelity. It also assumes circuit are not so highly tuned that minor changes in capacitors is going to upset the function of the circuit beyond design parameters!

I would just like to be able to make a more informed decsion when purchasing capacitors for my old CB's and Export radio's!

As always thanks!!

 

[bob85]

It depends where in the circuit the caps are,

voltage rating won't make any difference so long as they are not operating near to max rating,

organic electrolytics like black gates last much longer than conventional electrolytics and cost an arm & a leg even used,
elna cerafine last a long time too, don't know about the other brands that have come to market more recently

if they are reservoir caps in the psu of a homebase increasing value raises average voltage and peak current in the rectifier and transformer winding,
not a great idea to increase value by 10 or 100x as most base psu's are under rated for the job they have to do,

if they are part of an ALC or AGC loop they can have a large effect,

if the caps are in the audio section then changing value can have a dramatic effect even in a cb radio depending on them been in series coupling the signal to the next stage or part of a feedback loop or used as bypassing,

swapping electrolytic or tantalum coupling in the audio stage to wima polypropylene of the same value tends to improve the sound in cb or hf sets,

going cap crazy and cramming V-Cap CuTF in there would be a waste of time & huge money,

in a cb or hf set id go with quality 105 degree caps over a lower temp rated audio grade cap for power supply rails,
105 degree caps tend to last longer in high temperature environments

 

[Captain Kilowatt]

I couldn't have said it better Bob. You need to be careful when replacing caps with values far outside their original value. Series audio caps are more forgiving and will affect the frequency response to some degree while changing values in an AGC circuit can have drastic results.

 

[Onelasttime]

I was not trying to raise the capacitance up some of the caps have values that are not made in modern cap.'s of the same voltage and lead spacing. Some of these caps are insanely small. I tried Dig-Key and Mouser's and some values just are not made today. The caps had by today standards odd ball diameter's as well. I am talking about caps that where 25V or 50V maybe 2-3mm wide and maybe 3mm tall. with super low values like .0001uf at 25V etc.....I tried to say at the same level of capacitance when I could. Likewise I tried to select 5000 hour 105°C caps but diameter, height and lead spacing sometimes forced me to increase. Some caps the only way I could the right lead spacing, diameter that would clear or height that would clear was to go down to 85°C or 2000 hour rating etc... I also had to work around huge back order's or wait 18 weeks for some of the caps I would have preferred. I managed to stick to Nichicon, Panasonic, and United Chemi-Con.

The caps I would have most liked to upgrade like the power filter caps where limited by space. I did not want to do the stuff a huge cap in with long leads exposed then push it over on it's side to make it fit. Same thing with the 1000uf 6.3V cap I had a hard time finding a 10V or 16V that would fit at the OEM rating of 1000uf.