Mallory cap

Kevin Mincke · Post by **Kevin Mincke** » 24 Mar 2014 2:15 am

Lookin' for a couple Mallory foil caps to bring my Gibson lap steels back to original. If not, any recommended replacements? They are #424 400vdc I believe.

Blake Hawkins · Post by **Blake Hawkins** » 24 Mar 2014 8:50 am

If you look around the cap, you will probably see
".05 mfd" or ".02 mfd." that will be the value of the cap. The voltage does not matter. The original caps were made for tube type radios which used high DC voltages.
Any modern cap of the right mfd will do for a replacement.
If you want to retain the original appearance,
you can melt the wax on the cap, remove the insides and put a modern cap in there. Then remelt the wax on to the cap. I've also used hot clue to seal the insides, with a bit of the old wax on the ends to give it the original look.

Blake Hawkins · Post by **Blake Hawkins** » 24 Mar 2014 9:03 am

Some additional thoughts on the cap.
If you have access to someone with a capacitor tester it would be useful to measure the value and see if it is more than 20% of the original value.
Usually the capacity will drift upward over the years.
In some cases the cap will short internally.
You can tell that if the tone control works like
a volume control and really decreases the output.
Of course, in normal operation when you put it in the bass position it will cut down the sound a bit.
Also, you could put in a modern cap and if the guitar does not sound different just put the original back.

John Billings · Post by **John Billings** » 24 Mar 2014 10:33 am

"you can melt the wax on the cap, remove the insides and put a modern cap in there."

That's what my amp tech did when he recapped my '52 Pro Amp. Looks like stock original.

Kevin Mincke · Post by **Kevin Mincke** » 25 Mar 2014 10:14 pm

Great info guys, thanks! I no longer have the caps as I gave the one to an amp shop to find me a couple and so far they haven't produced results. The other cap was actually all brown in color and was a few years older than the other. I could post a pic if needed but think if I found one of the same value it would be fine and I'd be happy!

Paul Arntson · Post by **Paul Arntson** » 26 Mar 2014 12:05 pm

I picked up one of these to see what value sounded best.

Capacitor substitution box.
http://www.amazon.com/Elenco-CS440-Capa ... B0002KX776

Larry Robinson · Post by **Larry Robinson** » 26 Mar 2014 12:16 pm

Les Paul Gibsons use 0.047 ufd for tone according to Gibson Guitar website.

Blake Hawkins · Post by **Blake Hawkins** » 26 Mar 2014 4:38 pm

.047 is the modern replacement for .05. A few years ago "standard values" were changed.

Jonathan Lam · Post by **Jonathan Lam** » 26 Mar 2014 9:36 pm

call leeds radio in brooklyn, ny
http://leedsradio.com/
Vintage parts supply.

Bob Isaac · Post by **Bob Isaac** » 28 Mar 2014 12:16 pm

This may be common knowledge already, but I'll throw it out, for what its worth. The old foil-lined cardboard tube, oil-filled, beeswax coated caps had a standard shelf-life of about 8 years. There are always exceptions, but generally speaking, any NOS or pulled caps of this design is most likely worthless. I love using the technique that Blake described, so succinctly. It really helps keep that "original" visual effect. Electronically speaking, a modern polyester cap of equal value and voltage as the original "should" be exactly the same. (A point of much debate within my vintage electronics hobby community!) But all things considered, sometimes you just want to replace an item with a new one that is constructed like the original.

I have a source for newly constructed AmpOhm paper-in-oil, tin foil caps. They are expensive and they come from the UK.
But the good news is that they do make a .047uF cap at 630v (the higher voltage rating is OK, you just don't want to go under - and in the case of this circuit, anything over a couple of volts is overkill anyhow)

http://www.audiocap.co.uk/ampohm-0047uf ... -336-p.asp

About $20 for the cap and about $10 for the shipping.

I see a couple of other alternatives out there, but this is the only one I have experience with. The microfarads measured true on the ones I purchased (for a friend's hi-fi amp), and he was pleased with the results. Honestly, my ear isn't "calibrated" enough to hear any difference...

Others:
V Cap http://www.v-cap.com/tftf-capacitors.php VERY expensive!

Jupiter HT Beeswax Paper Caps about $45 plus shipping from UK - I have also purchased from this vendor, but not this product. Good people.
http://www.hificollective.co.uk/catalog ... -4655.html

I'm sure there are others, probably closer to home and cheaper.
Good luck!
Bob

Blake Hawkins · Post by **Blake Hawkins** » 28 Mar 2014 12:54 pm

OK, I may get flamed by the Audiophiles in the crowd but for a tone control on a vintage steel guitar,
any type of cap: paper and tinfoil in oil; ceramic;
polyester, polystyrene and etc. will work fine because all it does is shunt some signal to ground.
The output of the guitar does not flow through the
cap as it would in a coupling circuit of an amp.
Mallory 150s, costs $0,67 at www.tubesandmore.com
will do the job.
However, the expensive caps will work fine too.
If you are more comfortable with them, then go for it.

Larry Robinson · Post by **Larry Robinson** » 28 Mar 2014 3:24 pm

Save your money and go for the 67 cent cap. $20 for a capacitor? I can't justify that!

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