The voltage from my generator drooped so much that a 3500 watt
generator would no longer start a 1/4 hp motor. So I opened up the
back of the generator and removed the voltage regulator so I could see
the part number. Upon removal I see the ubiquitous bulged electrolytic
capacitor. All the electronics are are potted into the reg case but
the bad cap protrudes from the potting compound by about 5/8". Today I
ordered a new reg but I am thinking that since the bad cap sticks up
so far why not just remove the contents of the cap and peel the can
out of the potting compound, thereby exposing the cap leads. Then just
solder a new cap to the old leads or even directly to the circuit
board if I can get to it. I think that I will end needing to solder a
couple wires to the old leads and then solder the cap to the wires
though. If this turns out to be the case will having the cap connected
to wires that may end up being about 6 inches long be a problem? The
cap in question is 220 MFD 250 volt. I will be replacing it with one
that has a higher voltage rating.
Eric

Given that the alternative is landfill, use your heat gun (wife's hair dryer or oven) to remove the guts from the case and replace what is needed. IT may not be just that cap.

If you slide the potted guts out of the case, you then may freeze it hard, and hit it with a hammer to shatter the potting. This may help you get to the individual components faster. Been there. Done that.

Peter Wieck
Melrose Park, PA

On Wednesday, November 15, 2017 at 1:50:49 PM UTC-5, wrote:
The voltage from my generator drooped so much that a 3500 watt
generator would no longer start a 1/4 hp motor. So I opened up the
back of the generator and removed the voltage regulator so I could see
the part number. Upon removal I see the ubiquitous bulged electrolytic
capacitor. All the electronics are are potted into the reg case but
the bad cap protrudes from the potting compound by about 5/8". Today I
ordered a new reg but I am thinking that since the bad cap sticks up
so far why not just remove the contents of the cap and peel the can
out of the potting compound, thereby exposing the cap leads. Then just
solder a new cap to the old leads or even directly to the circuit
board if I can get to it. I think that I will end needing to solder a
couple wires to the old leads and then solder the cap to the wires
though. If this turns out to be the case will having the cap connected
to wires that may end up being about 6 inches long be a problem? The
cap in question is 220 MFD 250 volt. I will be replacing it with one
that has a higher voltage rating.
Eric

A lot of smps designs want the bypass electros as close to the secondary rectifier as possible. I don't suppose a good electro a few inches away will be as bad as one with high esr properly mounted, but it still might cause problems.

Unless it's an epoxy potting, you should be able to de-pot the board and get that cap in as it should.

wrote on 11/15/2017 1:56 PM:
The voltage from my generator drooped so much that a 3500 watt
generator would no longer start a 1/4 hp motor. So I opened up the
back of the generator and removed the voltage regulator so I could see
the part number. Upon removal I see the ubiquitous bulged electrolytic
capacitor. All the electronics are are potted into the reg case but
the bad cap protrudes from the potting compound by about 5/8". Today I
ordered a new reg but I am thinking that since the bad cap sticks up
so far why not just remove the contents of the cap and peel the can
out of the potting compound, thereby exposing the cap leads. Then just
solder a new cap to the old leads or even directly to the circuit
board if I can get to it. I think that I will end needing to solder a
couple wires to the old leads and then solder the cap to the wires
though. If this turns out to be the case will having the cap connected
to wires that may end up being about 6 inches long be a problem? The
cap in question is 220 MFD 250 volt. I will be replacing it with one
that has a higher voltage rating.

No.

Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

Prickman complete moron wrote:

---------------------------------


Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.



** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

The OP should add just enough wire to make connection to the PCB and twist the pair.


..... Phil

On Wednesday, 15 November 2017 23:26:21 UTC, Phil Allison wrote:
rickman complete moron wrote:

Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

which might or might not be a problem. I have a computer somewhere that had all its on-board supply caps replaced with the new ones hanging on wires. Works flawlessly.


The OP should add just enough wire to make connection to the PCB and twist the pair.

Do what you can do.


NT

On 11/15/2017 3:26 PM, Phil Allison wrote:
Prickman complete moron wrote:

---------------------------------


Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.



** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

The OP should add just enough wire to make connection to the PCB and twist the pair.


.... Phil

Put the biggest cap you can solder into the hole and parallel the wires
to the external cap.

wrote:

----------------------------

Prickman complete moron wrote:


Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

which might or might not be a problem.


** FFS - do you *read* posts at all????

How is that relevant to the Prickman's bull**** claim ?

FOAD



..... Phil

On Thursday, 16 November 2017 00:42:20 UTC, Phil Allison wrote:
tabby wrote:
rickman complete moron wrote:

Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

which might or might not be a problem.


** FFS - do you *read* posts at all????

yes

How is that relevant to the Prickman's bull**** claim ?

it's relevant to the OP's situation

FOAD

thanks charmer.


NT

wrote:

---------------------------


Prickman complete moron wrote:


Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

which might or might not be a problem.


** FFS - do you *read* posts at all????

yes


** But then ignore them and all context.


How is that relevant to the Prickman's bull**** claim ?

it's relevant to the OP's situation


** You ignored the question and the context, again.

Wot a tenth-wit.




..... Phil

On Wed, 15 Nov 2017 10:56:56 -0800, wrote:

All the electronics are are potted into the reg case

If it's an epoxy potting compound (usually hard and black), you can
soften it with commercial epoxy paint remover (methanol and methylene
chloride).
http://www.jasco-help.com/product/premium-paint-epoxy-remover
Or, you can use a hot air SMT desoldering thing:
https://www.youtube.com/watch?v=Oiyg6jIZg_w

I think that I will end needing to solder a
couple wires to the old leads and then solder the cap to the wires
though. If this turns out to be the case will having the cap connected
to wires that may end up being about 6 inches long be a problem? The
cap in question is 220 MFD 250 volt. I will be replacing it with one
that has a higher voltage rating.
Eric

Much depends on at what frequency the regulator is operating.

12 inches of wire = 31 cm
I'll assume #16 AWG wire, which is 1.3 mm in diameter.
1 ft of #16 AWG has a resistance of about 4 milliohms, which is much
smaller than the capacitor ESR and can be ignored.
I'll assume that the voltage regulator uses some kind of switcher
running at 1 MHz.

Plugging all that into:
http://chemandy.com/calculators/round-wire-inductance-calculator.htm
I get 378 nano-henrys inductance. At 1 MHz, that 0.421 ohms.

You didn't supply the original capacitor value, voltage, manufacturer,
and type, so I can't calculate what the ESR should be. For 250 uF and
25v, my guess(tm) would be about 2 ohms (at 100KHz).

Therefore, adding 12 inches of #16 AWG wire to the filter increases
its ESR by about 25%. That's not a huge amount and will probably
work, but I would increase the voltage rating of the capacitor in
order to get something with a lower ESR.

I don't suppose you could disclose the maker and model of the
generator, possibly a guess as to the original capacitor specs, and
perhaps a photo of the regulator?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Wed, 15 Nov 2017 10:56:56 -0800, wrote:

The voltage from my generator drooped so much that a 3500 watt
generator would no longer start a 1/4 hp motor.

I wonder what caused the capacitor to bulge? Mostly, I find that it's
the ripple current, where a small amount of AC voltage ripple is
impressed across a filter capacitor. This causes a high current to
flow through the capacitor, which causes heating, which causes the
electrolyte to boil, which eventually blows the lid off the capacitor.

So, what would cause AC to flow through the capacitor? Well, the
generator will do that if the output from each of the presumably two
phases is different. That could be caused by having a radically
different load on each of the two phases. A two phase 3500 watt
generator is really a dual 1750 watt generator, where each phase can
only supply 1750 watts. If you try to load all 3500 watts across one
phase, bad things will happen. Another possibility is a shorted turn
on one winding. I have a few other guesses, but can offer much
without a clue as to how its wired, which might be available once you
disclose the maker and model number.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Wed, 15 Nov 2017 20:38:35 -0800, Jeff Liebermann
wrote:

On Wed, 15 Nov 2017 10:56:56 -0800, wrote:

The voltage from my generator drooped so much that a 3500 watt
generator would no longer start a 1/4 hp motor.

I wonder what caused the capacitor to bulge? Mostly, I find that it's
the ripple current, where a small amount of AC voltage ripple is
impressed across a filter capacitor. This causes a high current to
flow through the capacitor, which causes heating, which causes the
electrolyte to boil, which eventually blows the lid off the capacitor.

So, what would cause AC to flow through the capacitor? Well, the
generator will do that if the output from each of the presumably two
phases is different. That could be caused by having a radically
different load on each of the two phases. A two phase 3500 watt
generator is really a dual 1750 watt generator, where each phase can
only supply 1750 watts. If you try to load all 3500 watts across one
phase, bad things will happen. Another possibility is a shorted turn
on one winding. I have a few other guesses, but can offer much
without a clue as to how its wired, which might be available once you
disclose the maker and model number.
Thanks for your replies Jeff. I did describe the cap in my first
post. It is a 220 MFD 250 volt cap.I did not name the generator
though. It is a Champion model C46540. It has an RV type 120 volt
receptacle that used to put out the full 29 or so amps. It also has
another 120 volt receptacle that is wired in parallel to the RV
receptacle and it is the type that allows either a 15 amp or a 30 amp
plug to be used. It also used to put out the full rated amperage. I
don't know if it does now. It also has a 240 volt receptacle that I
have never used except once just to test it.
In your previous post you mentioned using a heat gun to remove the
pottying compound. I'll take a look at the links you posted.
Thanks,
Eric

On Wed, 15 Nov 2017 10:56:56 -0800 (PST), "
wrote:

Given that the alternative is landfill, use your heat gun (wife's hair dryer or oven) to remove the guts from the case and replace what is needed. IT may not be just that cap.

If you slide the potted guts out of the case, you then may freeze it hard, and hit it with a hammer to shatter the potting. This may help you get to the individual components faster. Been there. Done that.

Peter Wieck
Melrose Park, PA
Does the shattering damage other stuff? I could get some dry ice and
freeze it really hard and then go after the potting with a punch.
Eric

On Wed, 15 Nov 2017 11:13:51 -0800 (PST), John-Del
wrote:

On Wednesday, November 15, 2017 at 1:50:49 PM UTC-5, wrote:
The voltage from my generator drooped so much that a 3500 watt
generator would no longer start a 1/4 hp motor. So I opened up the
back of the generator and removed the voltage regulator so I could see
the part number. Upon removal I see the ubiquitous bulged electrolytic
capacitor. All the electronics are are potted into the reg case but
the bad cap protrudes from the potting compound by about 5/8". Today I
ordered a new reg but I am thinking that since the bad cap sticks up
so far why not just remove the contents of the cap and peel the can
out of the potting compound, thereby exposing the cap leads. Then just
solder a new cap to the old leads or even directly to the circuit
board if I can get to it. I think that I will end needing to solder a
couple wires to the old leads and then solder the cap to the wires
though. If this turns out to be the case will having the cap connected
to wires that may end up being about 6 inches long be a problem? The
cap in question is 220 MFD 250 volt. I will be replacing it with one
that has a higher voltage rating.
Eric

A lot of smps designs want the bypass electros as close to the secondary rectifier as possible. I don't suppose a good electro a few inches away will be as bad as one with high esr properly mounted, but it still might cause problems.

Unless it's an epoxy potting, you should be able to de-pot the board and get that cap in as it should.
I don't know what the compound is. It is black and hard. I'll try to
get the new cap as close as possible.
Thanks,
Eric

On Wed, 15 Nov 2017 16:07:08 -0800 (PST), wrote:

On Wednesday, 15 November 2017 23:26:21 UTC, Phil Allison wrote:
rickman complete moron wrote:

Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

which might or might not be a problem. I have a computer somewhere that had all its on-board supply caps replaced with the new ones hanging on wires. Works flawlessly.


The OP should add just enough wire to make connection to the PCB and twist the pair.

Do what you can do.


NT
Your's and Rick's replies pretty much agree. I'll just get the new cap
as close as possible and then not worry about it.
Thanks,
Eric

On Thursday, November 16, 2017 at 11:49:31 AM UTC-5, wrote:

Does the shattering damage other stuff? I could get some dry ice and
freeze it really hard and then go after the potting with a punch.

Typically, not. This is not liquid-nitrogen cold. The stuff usually cracks into fairly separate pieces, but not explosively.

Peter Wieck
Melrose Park, PA

On Thursday, 16 November 2017 02:02:20 UTC, Phil Allison wrote:
tabby wrote:

---------------------------


Prickman complete moron wrote:


Electrolytic caps have fairly high ESR and inductance so that they will
never notice the effect of 6 inches of wire.

** Bull**** !!!

The Prickman keeps reposting the SAME ******** he has been for decades.

Adding 6 inches of wire to an electro will massively increase its self inductance, by a factor of 10 at least.

which might or might not be a problem.


** FFS - do you *read* posts at all????

yes


** But then ignore them and all context.


How is that relevant to the Prickman's bull**** claim ?

it's relevant to the OP's situation


** You ignored the question and the context, again.

Wot a tenth-wit.




.... Phil

I apologise for not considering you the centre of the universe. Have a nice plonk. Again.

Every so often, Phil goes off his meds and starts to act out. Dealing with him at these times is much like nailing Jell-O or peeling raisins. Not very rewarding despite considerable effort.

I am not sure what drives him back onto his meds - I expect he mouths off to one-too-many people face-to-face and gets his clock cleaned, or he is found moldering in an ally somewhere. A stint in rehab, and he is fit, once again to be in polite society until the next 'event'.

Either way, he has some good knowledge, with the failing that it is neither absolute, entirely accurate or complete. This is true of all of us - however, Phil takes that failing very personally, and deems himself exempt from the consequences.

Peter Wieck
Melrose Park, PA

On Thursday, 16 November 2017 19:43:34 UTC, wrote:

Every so often, Phil goes off his meds and starts to act out. Dealing with him at these times is much like nailing Jell-O or peeling raisins. Not very rewarding despite considerable effort.

I am not sure what drives him back onto his meds - I expect he mouths off to one-too-many people face-to-face and gets his clock cleaned, or he is found moldering in an ally somewhere. A stint in rehab, and he is fit, once again to be in polite society until the next 'event'.

Either way, he has some good knowledge, with the failing that it is neither absolute, entirely accurate or complete. This is true of all of us - however, Phil takes that failing very personally, and deems himself exempt from the consequences.

Peter Wieck
Melrose Park, PA

I hope I never end up so intolerant or crazy.


NT

On Thu, 16 Nov 2017 12:37:41 -0800 (PST), wrote:

I hope I never end up so intolerant or crazy.
NT

Don't worry. If it does happen, you'll be the last person to notice.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558