Forming filter caps

[novosibir]

Larry - your Norwegian is pretty good!

Roe, "my" Norwegian is generated with the help of this site:

http://www.translation.paralink.com/" onclick="window.open(this.href);return false;

My 'personal' language knowledge only is German, English & Russian - and maybe a bit remaining Latin from school, but that's already been nearly 40 years ago

Larry

[el34on11]

Before forming I put the caps (solder lugs upside) into hot water for about 20-30 minutes, to decristallize the electrolytic inside. It's similar as what you have to do with hard, old honey, to make it fluid again - and this pre procedure helps much to reduce the forming time.
Ouch - so many of my 'secrets' in only one post.....
Larry

Larry THANKS for shairing your secrets!!
I just acquired 6 nos LCR caps which will be finding their way into a 2203 build very soon and want to know if it is a good idea to do this procedure prior to forming these caps. I will be forming them after the build is complete as per your instructions before I start the testing procedure. Once decristallized, how long will the electrolytic inside stay decristallized? If it is relavant these are from '93 and '95.
Thanks again for shairing your wisdome!!!!!

Derrick

[novosibir]

... how long will the electrolytic inside stay decristallized?

After they're formed - by principle forever, if you're using the amp regularly and it doesn't reast longer than maybe 6 months.

If it is relavant these are from '93 and '95.

Those were good years of the LCR's! My congrats!
My whole stash is from 1993 and they're part of the legendary British Voice of my amps.

Larry

[el34on11]

Thanks Larry for the info.....

Do you ever worry about moisture getting under the outer "shrink wrap" on the caps or is this really not a problem?

Thanks

Derrick

[novosibir]

Do you ever worry about moisture getting under the outer "shrink wrap" on the caps or is this really not a problem?

No, never worried about it!
The shrink wrap is sitting so tight - and if nonetheless...

... the cap itself is sealed! So what?

Larry

[el34on11]

OK Thanks.......

Derrick

[el34on11]

Hey Guys.....

Larry I need your help........

Well I finished up my second 2203MV build, I used NOS LCR caps on this build so I thought I better use the forming procedure on this one as Larry suggested.
I'm using Hammond transformers 290HX Power, 1750U output and 194c choke. Specs for these transformers are here.....

http://www.hammondmfg.com/guitarLine.htm" onclick="window.open(this.href);return false;

I'm using Metro layout and chassis and most small parts...
Pics of chassis are here,how I was doing the reforming of the LCR caps....
http://s244.photobucket.com/albums/gg31 ... ng%202203/" onclick="window.open(this.href);return false;

O K well everything started out fine......Or so I thought...

298V accross the 100k at first fire up
Dropped to aprox 120V within about a minute or two
Was dropping steadly but slowly after that
It got to about 95V.....Aprox 5 minutes later


Then the power transformer got very very very HOT And had a MELT DOWN before I had realised what had happened and was able to shut the power off.....

Then it started smoking and oozing all kinds black stuff....It died a painfull death...

I know the power transformer is SCRAP now and has to be replaced, did I wreck my NOS caps???

Please look at the pics in the link and tell me if I have something wrong during the reforming prossess.. I will get a new transformer next week and have it changed out that is no problem.....

I don't know what the problem was that created the MELT DOWN I did make sure that none of the "tweaks" for forming were shorting to cause this as well.....

Could these caps have such high leakage to cause this? And are these caps going to be OK to start the reforming prossess over again once the transformer is replaced???

Thanks for any suggestions and help

Derrick

[novosibir]

I wonder why the mains fuse didn't blew!
Did your metal clip from the B+ to the 100K short to the chassis by accident?

A eventually high leakage current of the LCR's can't be the colprit, because the 100K before is a huge current limiter.
Check for the reason! Short? Main fuse way too big?

But the LCR's can't be damaged, when the current source (PT) before goes down!

Larry

[el34on11]

Thanks for the help Larry.....

I wonder why the mains fuse didn't blew!

Mains fuse is still OK didnt blow....I was wondering this myself

Main fuse way too big?

I have a 4amp slo blow in there,and a 1amp slo blow for the H.T.fuse, I think those are the correct values. Double checked the stamping on the fuse to make sure.

Did your metal clip from the B+ to the 100K short to the chassis by accident?

Larry I am sure that the clip didnt touch any part of the chassis,also not seen in the pictures i did have the clips protected with electrical tape while forming

Check for the reason! Short? Main fuse way too big?

Ok I've checked to make sure nothing visable was shorted,pulled the board back up to make sure there was no pinched wires, I did recheck the voltage switch and I have continuity between all terminals (i think this is because the transformer has melted down tho)...
Could it have been a bad switch or maybe a bad transformer that caused this?
I'm pretty sure that there were no visable shorts and the transformer was wired correctly,any suggestions where I can start looking for shorts?
Thanks for your help!!!!

Derrick

[novosibir]

I think, that after that all it's simply been a bad PT, who has eaten itself.
Probably a manufacturer's fault?

Swap in another one and start again.

Larry

[el34on11]

Thanks Larry
I'll have the new transformer by the end of next week. I'll make sure I pay closer attention to see if the new transformer is getting hot!!!
Even tho I'm out a brand new transformer I'm feeling better that I didn't do something wrong to cause the melt down.....

I'm going to pull this one appart and have a look inside, even tho I dont think I will I will find anything.......I just have to look

Thanks again for your help Larry

Derrick

[el34on11]

Well here it is...........

P1000384-1.jpg

(90.18 KiB) Downloaded 1056 times

Primary side shorted out......

It releised all it's "magic electrical smoke" and now its dead! BTW it is the worst smell ever.......

Too bad there is "no refunds or exchanges on electrical products"

Derrick

[Structo]

Yep, once you smell that smell you will always remember it.

Which is kind of good in a way because if you ever smell it again you will reach for the power switch very fast.

[Greazygeo]

I'm getting ready to try this on my 1959RR. It has bleeder resistors on 4 of the filter caps. Do I need to unsolder all of them or just the two that were mentioned?

[novosibir]

It has bleeder resistors on 4 of the filter caps.

If thee are two across the 1-st filter caps, then they anyway have to be removed entirely, cos they aren't there original.

Check, whether there's an orig. PT in the amp with the yello CT from the HT secondary, what is going between the 1-st filters!

Larry