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Trying to decipher a particular capacitor rating

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cherylk

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It's an orange drop cap.

It has +4l7 +35V on it but the 4l7 looks like:

+4 7
l

I can't tell if it is a numeral one, a capital "I", or a lower case "L" and it is written like a subscript.

Can anyone help me decipher this? It is in a 1979 vintage pre-amp.

EDIT: I can't make this look right. The edit function keeps dropping my spaces.

The "l" is a subscript between the 4 and 7.
 
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It has +4l7 +35V on it
.... The "l" is a subscript between the 4 and 7.
I think the "l" is supposed to be a comma ( , ) and is used as a decimal point.
I have seen capacitors like this before, I even have some somewhere.

So your capacitor is a 4.7µF

JimB
 
Take a picture of it and post it, it'll replace a thousand words =)
 
Thanks JimB!

I can try taking a pic but I'm not sure if I can get close enough with my camera for the pic to be readable. Maybe it's time for a new camera with a macro lens. It would sure be easier than trying to describe this stuff.

Aloha,
Cheryl
 
I have a digital camera that's at least 7 years old, anything that wasn't DIRT cheap should have a manual or macro focus mode that will let you take pictures up to about 4 inches or so.
 
Trust me on this since I've tried repeatedly and used 35mm SLR's for many years and do understand cameras.

My Olympus (about 8 yrs old) will not produce an in-focus picture when you are closer than about 12-14 inches. Doesn't matter if you use manual focus, auto-focus, flash or no flash, tripod or no tripod. The resulting picture will be so blurry that the small print will be impossible to read.

While it was still under warranty I sent it back to the factory due to the poor focus. They sent it back and said they "fixed it." Well, they sure did -- it was even worse. On an otherwise decent camera the focusing is a joke.
 
I'm sorry cherylk, it's not a matter of trust, it's a matter of first hand experience.
Attached is an image I just shot sitting at my desk using my cell phones12-14 inch fixed focused lense in bad lighting using a flashlight and a piece of paper as a diffuser at 1 inch from the mm scale of my ruler using a cheap Chinese 10x plastic eyeloop to adjust the focus, all freehand. Based on some rough guesstimates and the general focus quality of the image it allows for seeing details down to about .2mm
 

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I've been bored a few times, I've done the same thing using a pair of binoculars as a telephoto lens for some birds shots. Not great, not bad, more than clear enough to view.
Fixed focus is easy to deal with, and a lot of modern digital cameras use a through the lens auto-focus technique which will automatically adapt to any additional lens put in it's way obviously within it's ability to focus, you lose the edges of the images, but even old digital cameras have enough usable pixels to spare.
 
I've got a desk magnifier lamp that I've used with an old digicam (KODAK DC3200) to get "almost macro" shots. I just clean the lens real well on the lamp, then focus thru the lens (via the CCD preview) as best as I can. The nice thing is the lamp give even lighting to whatever I am photographing. Its nothing compared to my small Canon with its macro/autofocus modes, but not bad for the cheapness of it, either...
 
Okay, finally. Let's see if I did this right...

There is the weird orange drop cap. It's a little hard to see because of the angle. I was afraid if I bent it down further it would break.

In the other picture is a ceramic cap that has "47K" on it. I think it is 47pf with a 10% tolerance. Someone else told me it was 47,000pf. And yet another person said both of those are wrong and it is 470,000pf. I'm pretty certain the last one is dead wrong.

What do you guys think?
 

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Cool! Thanks JimB. I've been trying to read up on all of this coding.

Interesting that I was the only one who actually got the ceramic value correct. A guy at Mouser electronics was the one who said it was 470,000pf and told me they had nothing like that in stock. :-(

I didn't know they were making tantalum caps in the late 70's. Do you know if they go bad as often as the other orange film caps (mylar and PP)?

Thanks! Cheryl
 
mylyar and PP caps should be nearly imortal, tantalum caps electrolyte is solid so as long as their voltage and temperature is kept well within range they should have a considerable lifetime. By the way those pictures came out pretty decent, did you use a different camera or were you able to refocus the one you were having trouble with before?
 
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I did have to replace a couple of orange drop mylar caps in my old Nakamichi cassette deck.

Unfortunately, after our last move most of my stereo gear remained boxed for 5 years until we added a room and there was finally space to set it all up. When it was all boxed up everything worked fine. When it was finally set up, everything but the tuner had problems. I'm slowly working through all of them.

The pre-amp pictured is almost fixed. The right channel was gone and it has crosstalk in the tape monitor position. I suspect the switch itself is the xtalk problem and I finally fixed the right channel (don't know for sure what it was but suspect a chassis ground issue). If a new switch doesn't fix the xtalk then I suspect the caps. I have searched high and low for a schematic and or wiring diagram to no avail. Fosgate bought Audionics but will not even respond to requests for service docs for the gear.

The turntable was sluggish and the tonearm rest/lock broke -- I fixed those problems. The head amp died and I ordered a new Pro-Ject.

The Nakamichi was missing the right channel when Dolby was on and a few new orange mylar caps in the Dolby circuit did the trick. The eject cable hold-down broke and I had to craft a solution for that. Then I accidentally knocked the nut off the tape guide and went through he** getting the guides and heads properly aligned again.

The CD Player/Recorder had a leaky electrolytic and I had to perform microsurgery on the PCB to repair the damage.

After fixing the pre-amp xtalk, next up is figuring out the subtle hum on the amp.

This gear is all in the 25-32 year old range except for the 10-year-old CD. I have read that NOT using old gear is the worst thing you can do and that is what causes the caps to fail. I've got a good working knowledge of basic electrical circuitry, but this is my first attempt at actually trouble-shooting and repairing electronic devices. I just kind of slowly slogging through them but am making progress. We moved to the Big Island of Hawaii 5 years ago and there is really no place to take them for repair. There are no audio shops and the only electronics supply store is a very poorly stocked Radio Shack with employees that don't know anything about electronics.

People like you guys have been my savior and are really helping me resurrect my beloved old gear. You don't know how much I appreciate the help!
Aloha and Mahalo,
Cheryl
 
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Yes Sceadwian, I used a different camera.

On mine, as you focus (either auto or manual), it seems to focus okay and then in the last fraction of a second it sort of backs up and goes out of focus. And the more times you try in succession, the more it backs up each time. It is really weird. I finally gave up and borrowed a friend's Nikon with a cheap macro lens...mucho bettero. It only took 3 shots to get 2 relatively good pics.
 
mylyar and PP caps should be nearly imortal, tantalum caps electrolyte is solid so as long as their voltage and temperature is kept well within range they should have a considerable lifetime.

I would certainly disagree with that, tantalum capacitors have proved to be EXTREMELY unreliable - and few manufacturers use them because of it.
 
Depends on their proper usage Nigel, there is nothing inherently unreliable about tantalum capacitors and to say such is a misrepresentation of reality. I don't care how many devices you've seen that have had a tantalum as a failure point, such as using them in inappropriate points in a circuit, without proper safeguards, or worse using dirt cheap poorly made ones and then blaming it on the core technology.

They're used in implantable heart defibrillators for one because of their energy density and high reliability.

And I think the military and Nasa might disagree with you as well.
https://www.electro-tech-online.com/custompdfs/2010/10/advpass-conn_sform.pdf
 
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One more question: How can I tell which lead is positive/negative on the tantalum cap whose picture I posted earlier?

The only possible markings I see are the + signs in front of the +4.7 and the +35V. If those are the polarity markings, then it looks like the left lead is the positive. Is this correct? HELP! Or is it some type of special code?

My new one is fairly well marked and I looked up the spec sheet to be sure and it has the positive lead on the right.

In both cases, I'm looking at the side with the printing on it.

Don't want to damage the preamp or have an explosion...
 
Depends on their proper usage Nigel, there is nothing inherently unreliable about tantalum capacitors and to say such is a misrepresentation of reality. I don't care how many devices you've seen that have had a tantalum as a failure point, such as using them in inappropriate points in a circuit, without proper safeguards, or worse using dirt cheap poorly made ones and then blaming it on the core technology.

Most of the ones I've seen fail have been on regulated 12V supplies, with only 17-18V feeding the input of the regulator, and the capacitors were rated at 35V. So that's running them at only 1/3 of their rating - I wouldn't ever use them - except where it's the only choice (good for timing caps, where electrolytics are rubbish).

Many others here agree on their unreliability, and like I said everyone using them in domestic electonics stopped using them for their poor reliability.

Pretty pointless quoting militray spec devices though :D
 
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