# Is this an electrolytic?



## WannabeGood (Oct 24, 2007)

I've opened up the back of my Silvertone 1471 (1960's) amp to do a power cord and fuse holder replacement and am thinking that I should probably replace the caps while I have it disassembled. Is the aqua/teal colored cap an electrolytic? I ask because it doesn't look like the ones available from the Tube Store and I want to be sure before I order anything. If they're not do they need replacing anyway? There are four of these. Assistance requested.










My apologizes if the photo is large. I tried resizing it in photobucket and then reattaching it but it still previews pretty huge. So sorry.

Regards,


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## keeperofthegood (Apr 30, 2008)

:O Image is kinda small for me actually.

That is a paper cap, looks to go across the line and ground. Not a good idea with those even when they were new (and as recently commented by one of the over 70's on the antiques radio forum I am a member of, when new those paper caps only had a 4 year life expectancy sitting on a shelf never mind being used). 

Read this: ABC's of Safety (Interference Suppression) Capacitors for Tube Radios

Yes, justradios sells them and I have had good business shopping from them too.



> *Types of Safety Capacitors: *
> 
> 
> There are *two major types* of interference-suppression / AC line filter safety capacitors; namely, type X and type Y. The purpose of these capacitors is to reduce radio frequency interference and to ensure safety from shock and fire.
> ...


Looking at their web site, it does not look to me that The Tube Store carries this important type of capacitor, but email them and ask.


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## nonreverb (Sep 19, 2006)

WannabeGood said:


> I've opened up the back of my Silvertone 1471 (1960's) amp to do a power cord and fuse holder replacement and am thinking that I should probably replace the caps while I have it disassembled. Is the aqua/teal colored cap an electrolytic? I ask because it doesn't look like the ones available from the Tube Store and I want to be sure before I order anything. If they're not do they need replacing anyway? There are four of these. Assistance requested.
> 
> 
> 
> ...


Hope, that's a coupling cap. Non polarized. might be a Cornell Dubilier brand.


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## keeperofthegood (Apr 30, 2008)

Yea really hard to tell in the photo, looks like the top end to the fuse and the bottom to the chassis where the two resistors are connecting.


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## Wild Bill (May 3, 2006)

WannabeGood said:


> I've opened up the back of my Silvertone 1471 (1960's) amp to do a power cord and fuse holder replacement and am thinking that I should probably replace the caps while I have it disassembled. Is the aqua/teal colored cap an electrolytic? I ask because it doesn't look like the ones available from the Tube Store and I want to be sure before I order anything. If they're not do they need replacing anyway? There are four of these. Assistance requested.
> 
> 
> 
> ...


Why not get rid of the cap entirely? And make things safer yet?

First, clip out the cap. Then install a modern 3-wire cord, making sure to put the green ground wire under one of those nuts on the power trannie bolts.

This amp has a power transformer so the cap in question is really only there for hum minimizing. With a 2-wire cord you had a 50/50 chance of putting the right wire to the power transformer to the ground or neutral side of the line. If it was the wrong way around the cap would then bypass the hum instead.

With a 3-wire cord, you have a hard ground at all times with the extra ground prong! So who needs the cap?

Please note that this is only safe to do when your amp has a power transformer. Smaller amps with no power transformer are wired differently and the cap is absolutely necessary unless you provide an isolation transformer.

WB


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## dwagar (Mar 6, 2006)

regarding brand, that would be a Sangamo.


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## nonreverb (Sep 19, 2006)

dwagar said:


> regarding brand, that would be a Sangamo.


Good call, that would've been my next guess


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## WannabeGood (Oct 24, 2007)

Thanks for the help folks............... Unless I'm not reading correctly then I'm understanding that: 1) Yes the caps, although they are not the electolytic type, are well beyond their shelf life and should be replaced and 2) the pictured one is not required when I install a 3 wire cord. Correct? Question..........If the paper caps are "Not a good idea" then are there better/more reliable types that would be recommended? Attached is the wiring schematic for this particular amp.










The pictured one in the original post is the C5 on the schematic (arrow) the other similar ones are the C1, C2 and C3 (asterisk) on the schematic. Thanks again.

Regards,


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## nonreverb (Sep 19, 2006)

WannabeGood said:


> Thanks for the help folks............... Unless I'm not reading correctly then I'm understanding that: 1) Yes the caps, although they are not the electolytic type, are well beyond their shelf life and should be replaced and 2) the pictured one is not required when I install a 3 wire cord. Correct? Question..........If the paper caps are "Not a good idea" then are there better/more reliable types that would be recommended? Attached is the wiring schematic for this particular amp.
> 
> 
> 
> ...


I don't know where this change every cap I see idea came along but here's the scoop. Yes, wannabegood, there are paper/wax coupling caps in really old amps and yes they are pretty well garbage now. The great thing is that in the '60's they began producing much better types made from various other materials like Mylar and styrene. These caps don't suffer the same problems as the earlier types because, for one they are sealed units (unlike the wax type) and the materials and manufacturing techniques were better.
There is no reason to replace them if it's not needed. In the Hammond organ world any organ made from 1964 on is considered more desirable. One of the reasons why is that the company changed from wax/paper caps to red mylars in the generator and vibrato line box. The effect of this was, that after over 40 years, these caps are almost exactly the same value as new.
So if you do indeed have any wax/paper caps in your amp, change 'em but if they look like the one you have pictured you don't bother.
There, that's my 2 cents worth.....


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## keeperofthegood (Apr 30, 2008)

@[email protected] Ok nonreverb, whacking that cap with a hammer, inside, paper or other? If paper, I would replace them. If they are not paper, I would leave them too.

Wild Bill has been reported as using a meter and finding where old caps have drifted to and using modern caps of those values where tone would be affected.

Yup, I have a 1950 Marconi TV, the paper caps I can see through the HV section are all split in half and I know once I get the CRT off (dangerous buisness that) that what I will find underneath will not be any much better. And yes, once you go past paper caps, or silver mica caps, what you find failing are electrolytic. Those have a shelf life or use life of about 10 years on average (100,000 hrs mean time before failure is what I recall back in the 80's and I don't think they have gotten better since). Electrolytic are made of water and aluminum, and over time, the water does dry out because no seal is ever perfect, though sometimes the oddities of physics an electrolytic an conceivably work for 70 years, its been known to happen. Of the other capacitor materials, well tantalum has a reputation for sudden failures but other than that the rest all seem to have a fairly overall good performance over time report.


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## greco (Jul 15, 2007)

Not wishing to derail the OP...but while we are on the topic of caps (especially electrolytics) *what brand name(s) of caps do you typically buy?*

I am sure that someone mentioned (maybe nonreverb... IIRC) that you really take a chance with imported caps as they tend to leak and/or fail.

Thanks

Dave


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