Recapping a Bell Expressvu 9242 satellite receiver

[goldbird78]

Hi All, I am recapping a Bell Expressvu satellite receiver due to the known issues with swollen caps. I want to use Nichicon or Panasonic caps...Couple questions

1) is low ESR & low impedance the same thing ?
2) Am I safe using low or super low impedance capacitors as a replacement everywhere ?
3) I have read that you can go higher on voltage with replacements. for an example if the originals are 820uf 10v could I put 820uf 25v without any issues ?

[stj]

Re: Recapping a Bell Expressvu 9242 satellite receiver

yes to all of it,
but if you up the voltage they get bigger and may not fit - check the diameters before you buy.
i recommend panasonic FR
maybe one day they will sponsor me and give me free caps!

[goldbird78]

Re: Recapping a Bell Expressvu 9242 satellite receiver

Thank you for the reply.......One last question. Ripple current ??? From what I have read, low EST/impedance has a higher ripple current rating which is a good thing ???

yes to all of it,
but if you up the voltage they get bigger and may not fit - check the diameters before you buy.
i recommend panasonic FR
maybe one day they will sponsor me and give me free caps!

[PeteS in CA]

Re: Recapping a Bell Expressvu 9242 satellite receiver

Hi All, I am recapping a Bell Expressvu satellite receiver due to the known issues with swollen caps. I want to use Nichicon or Panasonic caps...Couple questions

1) is low ESR & low impedance the same thing ? Close. Impedance is a vector sum of the cap's ESR, inductive reactance, and capacitive reactance. The two reactances vary with frequency and partially cancel each other, so impedance is usually given for a specific frequency.
2) Am I safe using low or super low impedance capacitors as a replacement everywhere ? If the part being replaced is a general purpose part, yes. If the part being replaced is a filter cap in a switching power supply DC-DC converter, a close impedance match is best, if possible.
3) I have read that you can go higher on voltage with replacements. for an example if the originals are 820uf 10v could I put 820uf 25v without any issues ? A higher voltage would be OK if it fits and the circuit isn't sensitive to the probably higher impedance.

Nichicon PW and HE series are good long life low impedance parts. Likewise United Chemicon LXZ and KY series.

If your circuit uses ultra-low impedance parts, you might want to look into polymer caps.

[goldbird78]

Re: Recapping a Bell Expressvu 9242 satellite receiver

I am not an electronic tech, just a hobbyist that is very good with a soldering iron and have fixed many electronics with obvious issues. Is there anyway to determine if it is a filter cap on a switching circuit ? The ones I am replacing are round Aluminum Electrolytic Capacitors. The capacitors I am replacing are 680uf 10V, 820uf 6.3v, 1200uf 6.3V. I have read the original caps were know to fail because the voltage was too low so I was going to replace them all with 16v ratings.

[stj]

Re: Recapping a Bell Expressvu 9242 satellite receiver

they sound like output filters

[goldbird78]

Re: Recapping a Bell Expressvu 9242 satellite receiver

So low impedance and a higher voltage would be fine ?

they sound like output filters

[stj]

Re: Recapping a Bell Expressvu 9242 satellite receiver

yes
it would help if you know the actual voltages - is the psu on a seperate board?
if yes, is the connector labelled?

[momaka]

Re: Recapping a Bell Expressvu 9242 satellite receiver

I have read the original caps were know to fail because the voltage was too low so I was going to replace them all with 16v ratings.

Probably not true.
The original caps likely failed because they were crap Chinese/Taiwanese brands to begin with.

Is there anyway to determine if it is a filter cap on a switching circuit ?

You mean on the power supply board vs. the mainboard (or main part of the board in case of one "do-it-all" PCB)? Post a picture of the board(s).

For power supply recapping, it's generally not recommended to go too far from the specs of the original capacitors, as otherwise the PSU may oscillate and actually output more ripple... in addition to also possibly make annoying audible chirping / whining noise. In rare cases, the PSU may get damaged too. So for PSUs, avoid deviating from the parameters too much (i.e. capacitance, voltage, and ESR/impedance) unless you know that you're doing.

As for the rest of the board in the box (mainboard): you can probably deviate quite a bit from the cap specs without any issues. In some cases, you can get away with much "worse" (on paper, in terms of specs) capacitors, as long as they are a quality Japanese brand - e.g. circuits with linear regulators that don't run hot (rare case, since LDOs *do* usually run hot.) In other cases, you cap probably put a super-low ESR cap (maybe even polymers) on a buck regulator, improving ripple/noise.

So it all depends.
You don't need to be an electronics engineer/tech, though, to be able to identify the PSU board vs. the main board... or again, in the case of one "do-it-all" PCB, which parts are for the power supply and which parts are for the board's step-down regulators and general filters. Just looking over many different electronic devices over time will get you there.

[PeteS in CA]

Re: Recapping a Bell Expressvu 9242 satellite receiver

I am not an electronic tech, just a hobbyist that is very good with a soldering iron and have fixed many electronics with obvious issues. Is there anyway to determine if it is a filter cap on a switching circuit ? The ones I am replacing are round Aluminum Electrolytic Capacitors. The capacitors I am replacing are 680uf 10V, 820uf 6.3v, 1200uf 6.3V. I have read the original caps were know to fail because the voltage was too low so I was going to replace them all with 16v ratings.

A couple of kind of coarse clues would be:

* 85C caps are not low impedance types; they're either general purpose or some special purpose (e.g. non-polarized);

* If they aren't near power components or near/on a processor module, they're probably not low impedance types (the digital guys may set me straight on that point, or refine it).

[stj]

Re: Recapping a Bell Expressvu 9242 satellite receiver

a lot of cheap consumer crap uses standard esr caps where it should be lower esr to save money.
pisses me off seeing stuff only a year or 2 old needing a recap because of this behaviour.

[momaka]

Re: Recapping a Bell Expressvu 9242 satellite receiver

a lot of cheap consumer crap uses standard esr caps where it should be lower esr to save money.
pisses me off seeing stuff only a year or 2 old needing a recap because of this behaviour.

No, it's just because they use crap cap brands that you see failures.
Even general purpose Japanese caps lasted for AGES in CRT TVs and monitors... and those bastards run hot and certainly should use at least entry-level low-ESR caps. After all, CRT PSUs are flyback/discontinuous transformer design, and those tend to be rather stressful on caps. So if Japanese GP caps can handle the application for a decade or more, there's no reason why "LOWESR" China/Taiwan caps shouldn't... except they don't, because their caps are just that unreliable.