CTC-9 Power Caps

[columbia]

I'm getting ready to re stuff the power caps in my ctc-9 Abington. As a replacement for the 160mf 250v caps, do most of you guys use a 150mf as a lone replacement or maybe two 80's? If you use multiple caps, is it dangerous not to use balancing resistors? Any personal experiences as to safest/best approach? Thanks

[timmy]

the same voltage and MF never less. 2- 250v caps @ 80MF in paralle will give you 250v 160MF, but not a good idea. if you cant get the same value as original, higher is the way to go both voltage and MF, never less. if there is a bleeder resistor between caps it should be put back as is was but adding to balance, ah no i dont think so. hope this helps.

[Findm-Keepm]

just did a recap of a Silvertone for a cousin - I used two 100uf 250V caps in parallel for the 160uF input filter.. I used radial caps, stacked. it was a tight fit in the can, but worked great. The B+ went up only 4V over the Sams value, so it worked fine.

Most caps were rated at +80%, -20% tolerance, so there was a wide variance of value. Todays caps are more tightly rated, with +/- 20% tolerance - that's the "M" code on most electrolytics. So your 150 could have been as high as 260-270uf new, hence the 200uf will suffice just fine.

Only in series do you need balancing/sharing resistors.

[columbia]

Wow. Thanks great info. I would have never thought of two 100mf's but it makes sense. It gives me higher mF so it's safer. Thanks much guys!

[stromberg67]

A while back I got four 160@350 from Mouser that i used on CTC-11 chassis. They were Mallory branded axials. They worked out fine. Hope the re-cap goes well for you .
Kevin

[columbia]

I'll check them out. Thanks Kevin.

[Phototone]

In paralleling caps one does not need bleeder resistors, these are only needed in series connection of caps. That is what I always understood, anyway.

[Electronic M]

Originally Posted by timmy

the same voltage and MF never less. 2- 250v caps @ 80MF in paralle will give you 250v 160MF, but not a good idea. if you cant get the same value as original, higher is the way to go both voltage and MF, never less. if there is a bleeder resistor between caps it should be put back as is was but adding to balance, ah no i dont think so. hope this helps.

On lytics you can go slightly lower in capacitance and be fine because of the tolerance mentioned before, in fact going higher in capacitance can be bad in some applications...If the B+ is high to begin with or if it drifts outside of ~30% tolerance due to a value change then running the set that way for a prolonged period could have adverse effects (if the set even works properly that way).

Never go lower in voltage though! That can be even worse.

[StellarTV]

150s are fine. Just make sure they're both changed to 150uF. The resulting voltage difference is negligible.

[columbia]

So Justin, are you saying to use two 100uF's in parallel? I got another good suggestion to use two 150uF's in parallel. I guess I'm a little confused. Wouldn't 100uF's put me out of the low tolerance range?

[columbia]

Correction to justin: I know you said 150's and not 100's. But do you think that would then put me too high in uF's? Thanks

[StellarTV]

Oh no, I'm talking about just replacing each single 160uF filter with a single 150uF at rated voltage or higher.

[columbia]

Got it and thanks!