F&T 32/32uF cap

[PelliX]

Bit of a random question; I bought a few F&T filtercaps and they measure on spec, except for the 32/32uF can which reads around 48uF on both sides. They all seem brand spanking new as they should be. Just curious, is this something that others have encountered (recently)? The 50/50uF actually only reads a couple of uF higher.

AL-ELK Typ LFAZ
IEC 60 384-4
40/085/56 ND

While it would actually work fine in the intended position (main filter cap in a JTM45 RI), I was looking to drop the value a little.

 

[Pete Farrington]

Ooh, kudos, I’ve never thought to check them.

 

[PelliX]

Ooh, kudos, I’ve never thought to check them.

I run most caps through a cheap tester just to make sure they're in the ballpark before installing them. This is one of the few times I've noticed a considerable deviation in value. The stock value is also 50/50, but I was just wondering whether there was a 'batch' that got the wrong jackets, somehow.

 

[Dblgun]

I for the most part always try to check them when I receive them just in case I get one that tests way outside the listed capacitance. My experience is that F&T's are usually very close so sounds like you have one that is bad, or as you stated, mislabeled. My guess would be the former rather than the latter. I have had Mallory/Sprague's test way out of spec when new and the vendor stood behind them. I would be concerned that it would drift further from spec when in use but have nothing to back that up!

 

[PelliX]

I have had Mallory/Sprague's test way out of spec when new and the vendor stood behind them.

You mean they argued that it wasn't a problem, or refused to exchange them? I would expect them to refer you to the retailer unless purchased directly, but otherwise...

I would be concerned that it would drift further from spec when in use

Yup, indeed. 50/50 in front of a GZ34 is well within spec, but I wouldn't want to push it over maybe 70/70. FWIW, the ESR and leakage are practically perfect on those 32/32's, so I'm still guessing it's a wrong jacket. I reached out to F&T but haven't heard back from them yet.

Does anyone know how to decipher their date codes (presuming those are date code) on the caps?

 

[Jon Snell]

The specification of an electrolytic capacitor is usually +50 -10%.
32u + 50% is 48uF.
Funny old world, ain't it.

 

[PelliX]

The specification of an electrolytic capacitor is usually +50 -10%.
32u + 50% is 48uF.

Well yes, but these are -10/+30%. I understand it's not "totally out of range", but compared to the others that are within a couple of % deviation, I find this a little odd. As mentioned, ESR and leakage are very good - on all of them.

 

[Ronquest]

Will it negatively effect the tone at 50uF? If your concerned that it could short, would it cause collateral damage?, if not I'd have no problem running them. Maybe check them after some run time for any drift.

EDIT to add. Just re-read your post and looks like your using them right after your GZ34, then shorting would be bad. But, does having higher than spec capacitance lead to shorting and is it any more prone to shorting than any other cap?

 

[PelliX]

Will it negatively effect the tone at 50uF?

No, just the 'sag' might require higher volume. That's a sort of guesstimate in my head. As I won't be running the amp full bore most of the time, it doesn't really matter.

If your concerned that it could short, would it cause collateral damage?, if not I'd have no problem running them. Maybe check them after some run time for any drift.

Certainly, a short would be bad, though I'll be putting silicon diodes inline anyway. I do take fairly good care of my gear and perform preemptive maintenance and checks here and there from time to time, but as an engineer I find it undesirable to put a (possibly) flaky part in as part of routine maintenance. The amp is currently still equipped with its stock (1998) LCR caps, so they've had their years, and I'm replacing them as part of my standard MO.

 

[Ronquest]

I'll be interested to hear what F&T replies. I would also feel better using an in spec part, whether that in spec part gives better results is subject for another discussion.

 

[PelliX]

I'll be interested to hear what F&T replies. I would also feel better using an in spec part, whether that in spec part gives better results is subject for another discussion.

Yep, I'll post back when/if they get back to me. They were nice enough on the phone but suggested I email them of course. As for the stock value, didn't they change that up a few times over the years and re-issues of the JTM45? I'm not an expert on their history, but others here are, I believe.

 

[Ronquest]

A quick look at online schematics (that you can even read) show changes.

 

[21fret]

A little off topic, but curious, if that new F&T rolls on the table evenly.
-I purchased ARS 50s and 32s and half of them were out of round and wondering if F&T has these manufacturing characteristics.
I understood that they should be working just fine and all it is, is filler to keep the cap on the inside centered, but I'm not familiar on how to check tolerances (with a cheap tester) as you did to be sure of their spec. I'm procrastinating putting these fresh cans in my 1992.

I'd expect getting new cans off the shelf that wouldn't have this odd issue, or anomaly.

 

[PelliX]

A little off topic, but curious, if that new F&T rolls on the table evenly.

They're all perfect in that sense. This is also why I'm fairly convinced they're 50/50's in the wrong jacket.

but I'm not familiar on how to check tolerances (with a cheap tester) as you did to be sure of their spec.

This is just a simple low voltage test using a cheap component tester. One could take the readings with a pinch of salt, but I've found them (I have a couple) to be very accurate. Especially when you have a fair few capacitors of a given voltage rating, same manufacturer, same-ish date and the others measure dead on spec, but a couple stick out in the middle of the value range (16 - 50uF) it indicates something being off.

These show you the capacitance (right down to a couple of pF), ESR and voltage loss. Cost about a tenner on fleabay, two tenners with the plastic 'chassis'. I soldered on a couple of handy clips to the contact pads. Beats the crap out of some of the more expensive units and just about anything until you start looking at 'semi' professional gear. Limitation is of course only low voltage testing...

 

[Dblgun]

You mean they argued that it wasn't a problem, or refused to exchange them? I would expect them to refer you to the retailer unless purchased directly, but otherwise...



Yup, indeed. 50/50 in front of a GZ34 is well within spec, but I wouldn't want to push it over maybe 70/70. FWIW, the ESR and leakage are practically perfect on those 32/32's, so I'm still guessing it's a wrong jacket. I reached out to F&T but haven't heard back from them yet.

Does anyone know how to decipher their date codes (presuming those are date code) on the caps?

No, the vendor (retailer) upon being contacted just had me toss them and sent replacements. As I remember the replacements were much closer to the listed capacitance. All are still in use and seem to be functioning as designed.

 

[What?]

The specification of an electrolytic capacitor is usually +50 -10%.
32u + 50% is 48uF.
Funny old world, ain't it.

That sounds like a hell of a tolerance on the + side. I'm seeing +/- 20% in the F&T data sheets. https://www.ftcap.de/en/products/electrolytic-capacitors/axial-lead/

 

[PelliX]

That sounds like a hell of a tolerance on the + side. I'm seeing +/- 20% in the F&T data sheets. https://www.ftcap.de/en/products/electrolytic-capacitors/axial-lead/

You actually want to be looking at the LF (AZ) series. Funnily enough, I can't find these exact cans in their catalog and the closest matches all indicate 20%. The jackets on mine all state -10/+30%.

 

[What?]

You actually want to be looking at the LF (AZ) series. Funnily enough, I can't find these exact cans in their catalog and the closest matches all indicate 20%. The jackets on mine all state -10/+30%.

Any pics I see of those shows the same. -10/+30%. I'm also not seeing a datasheet anywhere.

 

[Spanngitter]

I measured all the 32+32uF F&Ts I currently have on stock (only 15) and all came out fairly exact on target.
Seems like you indeed did catch an outlier...

 

[PelliX]

Well, I've mailed Mersen / F&T twice now and not even received an automated reply. This is a little disappointing. I'm going to give them another call in a bit. Ah well, it's good to practice my German skills a bit from time to time.

EDIT: Called them, but nobody's available to check it out until January. At least they could confirm they received my emails. Ah well, if the LCR's work a few more days won't kill them.