Is that right? Black Gate caps are/were infamous for taking months to settle down, I've experienced some of that myself. So does a new electrolytic cap need reforming? I don't know, I'm honestly interested. Certainly it is claimed that if unused for a while, they need time to come "on song" again.
The electrolytic manufacturers tell us that tests to check parameters of their capacitors must only be done on a freshly reformed DUT. I think they meant reformed less than 24hours before the test. And that applies to a new, or an old capacitor.
This seems to suggest that the meaurements will be different if carried out on a not freshly reformed capacitor.
That to me means one should not judge the "in circuit" performance of a capacitor unless it was reformed before assembly. Otherwise it is possible/likely that some performance will not be within specification.
This seems to suggest that the meaurements will be different if carried out on a not freshly reformed capacitor.
That to me means one should not judge the "in circuit" performance of a capacitor unless it was reformed before assembly. Otherwise it is possible/likely that some performance will not be within specification.
For checking measurements, I can understand their caution, but surely they don't expect the reforming process to be carried out before use? How would that be possible?
Are you suggesting that for any cap that hasn't been reformed, even brand new, the specs shouldn't be trusted? That's a kicker!
Are you suggesting that for any cap that hasn't been reformed, even brand new, the specs shouldn't be trusted? That's a kicker!
On re-reading your post, I feel that "could" would be a better word than "will". Which is a very different thing, and perfectly reasonable, IMO.
It is clearly my opinion based on what I have read, but I see will as more likely than could.
If there was only a small chance that using unreformed capacitors during DUT measurements then you might get far fewer manufacturers playing safe with their reforming advice.
If there was only a small chance that using unreformed capacitors during DUT measurements then you might get far fewer manufacturers playing safe with their reforming advice.
yes that is exactly what I have posting on this Forum for years. Reform your electrolytics before assembly.
I haven't been paying attention. Have you been suggesting reforming new ones? I'm struggling to imagine equipment manufacturers doing this, BTW.
Equipment manufacturers won't.
Do It Yourself.
I do mine over 72hours.
24hours very slowly. Discharge slowly (while the next batch are 24hr reforming)
second very slow 24hr reform.
Leakage current is typically 1% to 0.1% of the value specified in the datasheet after doing this. eg Leakage ~ 0.0001CV Amperes, at maximum rated DC voltage.
Do It Yourself.
I do mine over 72hours.
24hours very slowly. Discharge slowly (while the next batch are 24hr reforming)
second very slow 24hr reform.
Leakage current is typically 1% to 0.1% of the value specified in the datasheet after doing this. eg Leakage ~ 0.0001CV Amperes, at maximum rated DC voltage.
OK, thanks for that. Do you do this for all 'lytics, or just large values?
And another question; I have (for instance) an active crossover that has sat unused for 4 years now, and growing, full of Black Gate and Silmic 2 caps. What, if anything, can or should, I do about them? I won't be removing them, that's for sure!
Sorry if this is threadjacking.
And another question; I have (for instance) an active crossover that has sat unused for 4 years now, and growing, full of Black Gate and Silmic 2 caps. What, if anything, can or should, I do about them? I won't be removing them, that's for sure!
Sorry if this is threadjacking.
Most manufacturers say that electrolytics which were made less than about 2 years ago need no reforming before use. This is not the same as saying that the capacitor will deliver its rated performance under test conditions. What happens is that when you first switch the circuit on the electrolytics get some reforming simply from the circuit itself. If the cap is in good condition then this may take a few seconds or a few minutes. The circuit will work, but perhaps not at its best if it is sensitive to leakage current.
So as always in engineering it depends on context. I think AndrewT exaggerates the issue. Others completely ignore the issue. The truth lies somewhere in between.
What I do is check high voltage electrolytics for leakage before using them, as my stock tends to be 10-20 years old. Low voltage I am less bothered about, but I would still check larger ones.
So as always in engineering it depends on context. I think AndrewT exaggerates the issue. Others completely ignore the issue. The truth lies somewhere in between.
What I do is check high voltage electrolytics for leakage before using them, as my stock tends to be 10-20 years old. Low voltage I am less bothered about, but I would still check larger ones.
While I have seen it stated that transformers won't work because they arn't air gaped. I decided test that assumption. I built a choke input supply and tried 4 different transformers as the choke. Even when exceeding the current rating of the secondarys by 80% they seemed to work fine. That is the resultant voltage was about what was predicted by the choke input formula. If they had been saturated the voltage would have been higher than predicted.
To get choke input behaviour the inductance just has to be above a certain amount, set by the current draw. A good transformer can be used as a choke for small currents, but it will be much bigger and heavier than a choke designed to do the same duty.
Also, a choke input supply has the peak current (when the choke is most likely to saturate) at the point where the incoming AC voltage is going down past the DC voltage. Around this point a sudden drop in choke inductance will not make much difference. Beyond this point as the AC voltage continues to fall the choke may come out of saturation. My conclusion is that a choke input supply is not a good way to test a choke for saturation.
Also, a choke input supply has the peak current (when the choke is most likely to saturate) at the point where the incoming AC voltage is going down past the DC voltage. Around this point a sudden drop in choke inductance will not make much difference. Beyond this point as the AC voltage continues to fall the choke may come out of saturation. My conclusion is that a choke input supply is not a good way to test a choke for saturation.
drop by the house, i will give you some for a song.....
seriously, someone posted that you have to dismantle the traffo
so that you can put in some gap between the e's and the i's...
you can not use the traffo as is, you have to apportion ac and dc flux,
otherwise you can not be sure that that traffo will only be for show....
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