Yes, the vast reserves of NOS parts in China also look as if they were made only yesterday -, a little crude and marked by the wrong method and type face. Funny, that.
The approach we take, is that there still are reputable brands and if you stick to them, and only buy from authorised or reputable distros, you do get great quality so long as the type and brand selected is appropriate for the application. Caps from most manufacturers have improved quite a bit over the last 20 years and there's now little reason to look for a source of the obsolete ones.
However, from Ebay sellers, I see conspicuous junk caps that are often branded the same and in the same grade you want but some are like 30% smaller than spec. - wha?? The measured capacitance is OK but this is premium Elna 'for audio' product and you don't expect to be fooled by cleverly scaled down copies that pass photographic comparison. Otherwise, these products and the fakes look identical.
So, if you want genuine product, don't risk Ebay sellers as we say here over and over again, though it falls on deaf ears because lowest price is such an attractive lure to the unwary.
The approach we take, is that there still are reputable brands and if you stick to them, and only buy from authorised or reputable distros, you do get great quality so long as the type and brand selected is appropriate for the application. Caps from most manufacturers have improved quite a bit over the last 20 years and there's now little reason to look for a source of the obsolete ones.
However, from Ebay sellers, I see conspicuous junk caps that are often branded the same and in the same grade you want but some are like 30% smaller than spec. - wha?? The measured capacitance is OK but this is premium Elna 'for audio' product and you don't expect to be fooled by cleverly scaled down copies that pass photographic comparison. Otherwise, these products and the fakes look identical.
So, if you want genuine product, don't risk Ebay sellers as we say here over and over again, though it falls on deaf ears because lowest price is such an attractive lure to the unwary.
One of the problems I've been having is that the caps from the main suppliers are suspect as well, often their half the size of the original cap in the same values, even when their the same brand. I've got a bag of what is supposed to be original Panasonic caps in the 100uf/50v rating, which should match what's on this power board, but they're only 2/3rds the physical size. They came from a major supplier. They test fine but I'm leery about what's inside.
How important is it to stay with the exact same values on this power board?
Can I for example go with a larger value, maybe matching the original size and fit, would I be gaining anything or would I be changing the function or output voltages?
Capacitors being physically smaller nowadays is nothing to worry about. This is just down to improvements in manufacturing them - for example, the plates are often corrugated now which increases their effective area considerably.
Generally with power supply decoupling capacitors, more is better. So eg if youve got 3300uF dont be afraid to use 4700uF
Generally with power supply decoupling capacitors, more is better. So eg if youve got 3300uF dont be afraid to use 4700uF
Agreed, caps are smaller now anyway but be careful with your source who may be part of a supply chain exploiting those differences to pass off re-labelled junk, whether the seller is aware of it or not.
Check the manufacturer's datasheets for what you should be seeing and measuring. Either use the datasheet PDF link in the supplier's current on-line catalogue or search the manufacturer's product specifications/datasheets directly.
As an example, here's a current Panasonic full data listing of all their grades of aluminum electrolytics: https://industrial.panasonic.com/cdbs/www-data/pdf/RDF0000/DMF0000COL94.pdf
Check the manufacturer's datasheets for what you should be seeing and measuring. Either use the datasheet PDF link in the supplier's current on-line catalogue or search the manufacturer's product specifications/datasheets directly.
As an example, here's a current Panasonic full data listing of all their grades of aluminum electrolytics: https://industrial.panasonic.com/cdbs/www-data/pdf/RDF0000/DMF0000COL94.pdf
What worries me about these places is that they're not a very big store, and they have bins full of various caps as if they were nails at the home repair store. Their not packaged, just loose in the bins in huge quantities. I've been to five such places in the past few months. They all carry the same brands, plus the black, no name obviously Chinese brand caps that sell for cheap. They have Panasonic, Nichicon, Nippon Carbide, and Elna. They rarely have what you want in all one brand, only a few odd sizes in each brand, but in huge, bulk lots. Each bin probably had 5,000+ caps of one size. Then they have prepackaged assortments, in cheap plastic cases. These are the same parts and same values I see everyday on eBay as if they're buying from the same source as the eBay sellers. Worse, yet, they're charging full retail and more. The one place I called, about an hour from me, told me he only had the 330uf/50V axial caps in stock, they were unbranded, but he swore they were made by Panasonic and wanted $9.95 each. He had amplifier 'recap kits' too, for more than any of the amps they were for would bring fixed. I did buy a couple of transistors, a couple of 15011/12 pairs, out of the four only one tested good. They were dead on copies of the original Motorola parts but when I pried off the cap, the difference was obvious. Whether or not that dealer knows what he's selling remains to be seen but its my guess he's buying bulk from someone really cheap, even the big suppliers online don't have the quantities he's got on hand.
It would be more believable if there were local manufacturers using such parts which may have a surplus to be had but there is nothing of the sort here.
I did some digging through some of my boxes in the garage, I found several used STK chips, including a pair of 082 chips if it turns out I need them. They came out of a Realistic receiver. I also found a good D330 transistor out of another junk receiver.
If I can substitute caps, I should be able to hunt around and find some to fit either new or used. I have a box of fairly new PA amp boards, and a few boxes of caps that I'll have to test from long ago. I have boxes of caps from the late 80's or so but I've been told not to use them due to age, but I think an old cap that tests good is better than one that's shorted if its the only thing on hand. The bottom line is to justify fixing any old amp or receiver, it has to be done on the cheap to some degree. Its just not worth bringing one back from the dead if its going to cost $100 or more unless its a highly collectible model. Even then I don't think its necessarily worth it.
I just picked up a dead Onkyo TX8500 that won't even light up, it does nothing. I get no power anywhere in it as if the transformer was dead. All fuses are fine and the power cord checks out. Unless its something simple, its headed for the shelf in hopes I need it for parts one day I guess.
I'm still not 100% this Fisher won't be headed the same way.
Are the caps like these old units use still in production and use anywhere? Does any industry still use them? I can't figure why parts like this are so hard to come by these days.
25 years ago there were dozens of places to buy parts. Not any more.
It would be more believable if there were local manufacturers using such parts which may have a surplus to be had but there is nothing of the sort here.
I did some digging through some of my boxes in the garage, I found several used STK chips, including a pair of 082 chips if it turns out I need them. They came out of a Realistic receiver. I also found a good D330 transistor out of another junk receiver.
If I can substitute caps, I should be able to hunt around and find some to fit either new or used. I have a box of fairly new PA amp boards, and a few boxes of caps that I'll have to test from long ago. I have boxes of caps from the late 80's or so but I've been told not to use them due to age, but I think an old cap that tests good is better than one that's shorted if its the only thing on hand. The bottom line is to justify fixing any old amp or receiver, it has to be done on the cheap to some degree. Its just not worth bringing one back from the dead if its going to cost $100 or more unless its a highly collectible model. Even then I don't think its necessarily worth it.
I just picked up a dead Onkyo TX8500 that won't even light up, it does nothing. I get no power anywhere in it as if the transformer was dead. All fuses are fine and the power cord checks out. Unless its something simple, its headed for the shelf in hopes I need it for parts one day I guess.
I'm still not 100% this Fisher won't be headed the same way.
Are the caps like these old units use still in production and use anywhere? Does any industry still use them? I can't figure why parts like this are so hard to come by these days.
25 years ago there were dozens of places to buy parts. Not any more.
You answered your own question there but you can replace them with a little ingenuity. What you miss now are the old axial type (leads emerge either end) that you see on your power board. These could be hand fitted to anything, including tag board and wire-wrap terminals. Now, apart from legacy and low volume needs, electrolytic capacitors don't need leads at all. They either have short, snap-in prongs for the large caps or they're surface mount - the relatively new electronics you now find in every gadget, everywhere. No leads, just solder pads for fully automated assembly.
To circumvent this, I've occasionally drilled tiny holes through or next to copper traces to allow a new and smaller radial lead cap to fit the board neatly and securely. It's butchery sure, but if you can't buy acceptable obsolete parts, you won't have many options.
Electrolytic caps deteriorate even without use. As I checked my father's stock of unused caps, after 20-40 years many had very high ESR and weren't any good, even sealed in bags as new. Don't hoard them, buy fresh as needed plus a few more if they seem common types and there's a good price break.
The old caps I've got here were bought from a company not far from here that went out of business in the late 90's. I bought the 'contents' of the assembly shop. Which included 600 parts bins full of 1/4 to 1 watt resistors in every conceivable value, about 100 lbs of small transistors, and 40 or so 60 drawer organizers full of ceramic and poly type caps, plus a van load of misc IC chips that just got stashed away in the attic back then. Most of the caps were 100V, 3500uF or larger and a ton of 120v to 20v transformers. They were likely using these for power supplies. They were building control units for the swimming pool industry, not sure if they were timers for filters or if they were for lighting and such.
Most of the IC chips were power supply related and from the 80's or older. There's also a few cases of early Texas Instruments chips and a few Intel chips. I didn't intend to save them all but they just never got sold or moved.
The only thing I've never found very useful out of the whole lot is the transistor assortment, I've not once found a single one out of maybe 1000 part numbers that crossed over to anything I needed in audio. The resistors were stocked in packs of 1000 in each value and wattage. The same with the ceramic caps, but most of the ceramics are too small to be of use in most audio circuits I've run across. The real find in that buy was the shop equipment and benches, all of which is mostly gone now but it filled a 53' box trailer twice. I had a partner in the deal, he only wanted the warehouse equipment, an electric forklift, a small overhead chain winch, and the loading dock plates. The rest was mine to do what I wanted with.
Most of the electrolytic caps were Elna or Toshiba branded in that lot.
What generally fails in the cheap Chinese caps? Do they short of leak? Or are they just made of such junk they never function properly? I've got a few here that I know were from eBay I removed from a badly repaired pair of speaker crossovers, they test fine, but who ever replaced them used the wrong type and values in the wrong places. I replaced them with caps audio caps from Parts Express. (They had polarized caps in the crossover with no regard for the correct or original values needed).
They test fine for what they are marked, but have no branding or info on them. Just a value and voltage. I'm pretty sure that the person who recapped those speakers bought the caps from the one supplier I mentioned earlier with the bins full of no name caps for cheap.
I have seen a few caps that have split open on top, one case was on a Harmon Kardon integrated amp that had recently been recapped. The guy had a nephew of his do it in tech school as a project, just about every cap had swollen and split open within two years. I bought it for cheap and recapped it using all gold Nichicon caps I bought off eBay not knowing any better back then but its been fine ever since.
The two axial caps used on the power board on the Fisher here are likely of that style because the board is mounted too close to the bottom panel, there would be no room for a cap that size to stand up on that board, the cap would hang downward under the chassis and contact the bottom of the wooden cabinet. If I can use a larger value there, I may well have something here I can use. I've got a bag of Nichicon axial 470uF caps I bought last year for another project where I only needed two of them but had to buy 12. A buddy who lived in Japan sent them to me, he bought them there at a repair shop near the base where he was stationed. (That's no longer an option since he moved back to the states last fall).
Looking at the traces on the power board, the two 330uf caps and the D330 transistor are in line with the outgoing power to the tuner board, the two orange leads run to the preamp and the small board connected to the phono jacks. The pink also appear to go to the preamp alone. The light bulbs appear to be wired direct to the power switch through a ceramic cap and two 2 watt resistors. The dial bulbs are the type that look like fuses. I haven't been able to check them yet, I've yet to power this up all the way.
Does anyone have a simple resistance test chart for the STK modules? (STK082 and 086) I have several here and they don't all ohm out the same out of circuit and I'm not sure where they came from.
Most of the IC chips were power supply related and from the 80's or older. There's also a few cases of early Texas Instruments chips and a few Intel chips. I didn't intend to save them all but they just never got sold or moved.
The only thing I've never found very useful out of the whole lot is the transistor assortment, I've not once found a single one out of maybe 1000 part numbers that crossed over to anything I needed in audio. The resistors were stocked in packs of 1000 in each value and wattage. The same with the ceramic caps, but most of the ceramics are too small to be of use in most audio circuits I've run across. The real find in that buy was the shop equipment and benches, all of which is mostly gone now but it filled a 53' box trailer twice. I had a partner in the deal, he only wanted the warehouse equipment, an electric forklift, a small overhead chain winch, and the loading dock plates. The rest was mine to do what I wanted with.
Most of the electrolytic caps were Elna or Toshiba branded in that lot.
What generally fails in the cheap Chinese caps? Do they short of leak? Or are they just made of such junk they never function properly? I've got a few here that I know were from eBay I removed from a badly repaired pair of speaker crossovers, they test fine, but who ever replaced them used the wrong type and values in the wrong places. I replaced them with caps audio caps from Parts Express. (They had polarized caps in the crossover with no regard for the correct or original values needed).
They test fine for what they are marked, but have no branding or info on them. Just a value and voltage. I'm pretty sure that the person who recapped those speakers bought the caps from the one supplier I mentioned earlier with the bins full of no name caps for cheap.
I have seen a few caps that have split open on top, one case was on a Harmon Kardon integrated amp that had recently been recapped. The guy had a nephew of his do it in tech school as a project, just about every cap had swollen and split open within two years. I bought it for cheap and recapped it using all gold Nichicon caps I bought off eBay not knowing any better back then but its been fine ever since.
The two axial caps used on the power board on the Fisher here are likely of that style because the board is mounted too close to the bottom panel, there would be no room for a cap that size to stand up on that board, the cap would hang downward under the chassis and contact the bottom of the wooden cabinet. If I can use a larger value there, I may well have something here I can use. I've got a bag of Nichicon axial 470uF caps I bought last year for another project where I only needed two of them but had to buy 12. A buddy who lived in Japan sent them to me, he bought them there at a repair shop near the base where he was stationed. (That's no longer an option since he moved back to the states last fall).
Looking at the traces on the power board, the two 330uf caps and the D330 transistor are in line with the outgoing power to the tuner board, the two orange leads run to the preamp and the small board connected to the phono jacks. The pink also appear to go to the preamp alone. The light bulbs appear to be wired direct to the power switch through a ceramic cap and two 2 watt resistors. The dial bulbs are the type that look like fuses. I haven't been able to check them yet, I've yet to power this up all the way.
Does anyone have a simple resistance test chart for the STK modules? (STK082 and 086) I have several here and they don't all ohm out the same out of circuit and I'm not sure where they came from.
It doesn't matter who makes it or where an electrolytic cap is made. The best quality mass produced types in the widest range are probably still Japanese brands but they have been outsourcing too, for decades. If someone does the job just as well for cheaper, we're not going to last long in business if we don't take advantage and soon.
Elna's manufacturing process showing how caps are assembled is here: Aluminum electrolytic capacitors - Reliability | ELNA
For interest, there are a lot of details explained simply in topics like "Failure modes of electrolytic caps" An easy read.
No simple seal is perfect or everlasting, particularly not when the temperature cycles beyond its working comfort range. So the electrolyte escapes first as vapour and later liquid, extremely slowly but surely between the case, terminals and rubber seal. When it does, ESR rises and the capacitor then heats up in normal duty which just speeds up the process and could even end in a short, perhaps the safety cuts in the can top opening and spilling what remains of the foils over the rest of the electronics, otherwise it could explode like a little bomb. There are less common failure modes but the point to this is that there is a guaranteed minimum life but its not as long as many people assume.
The specification of a capacitor includes the working life at full rated duty which, as a power supply smoothing cap, would mean at its rated working voltage with a certain maximum amount of ripple current (essentially the work rate of the cap) for so many hours use. Typical electrolytics of 3,300uF might be rated for only 1,000 hours @ 50V with a ripple current of 2A. A premium grade cap might be good for 3A and last for 3,500 hours or even longer, so minimum capacitor lifetime is quite predictable and you guessed it, so is the premium for longer-life products.
Elna's manufacturing process showing how caps are assembled is here: Aluminum electrolytic capacitors - Reliability | ELNA
For interest, there are a lot of details explained simply in topics like "Failure modes of electrolytic caps" An easy read.
No simple seal is perfect or everlasting, particularly not when the temperature cycles beyond its working comfort range. So the electrolyte escapes first as vapour and later liquid, extremely slowly but surely between the case, terminals and rubber seal. When it does, ESR rises and the capacitor then heats up in normal duty which just speeds up the process and could even end in a short, perhaps the safety cuts in the can top opening and spilling what remains of the foils over the rest of the electronics, otherwise it could explode like a little bomb. There are less common failure modes but the point to this is that there is a guaranteed minimum life but its not as long as many people assume.
The specification of a capacitor includes the working life at full rated duty which, as a power supply smoothing cap, would mean at its rated working voltage with a certain maximum amount of ripple current (essentially the work rate of the cap) for so many hours use. Typical electrolytics of 3,300uF might be rated for only 1,000 hours @ 50V with a ripple current of 2A. A premium grade cap might be good for 3A and last for 3,500 hours or even longer, so minimum capacitor lifetime is quite predictable and you guessed it, so is the premium for longer-life products.
Last edited:
When I put some of the new old stock caps I have here from the 90's they show to have far more capacitance then they are marked? For example, a Rubicon axial cap marked 1000uF/35v tests at 1483uF. with an ESR value of .83Ω. This is using an Atlas ESR+ ESR70 handheld tester. I've got a bag of newer, maybe two or three year old Nichicon radial caps which all read less than the rated capacitance, these are mostly all small caps. They were bought from online, they are all burgundy in color. I bought them to replace all the exploded caps on the sound card in my computer a few years ago. (All the caps burst open all at once, no clue why but they all got replaced and its been fine ever since).
What I did when I replaced those caps was to match tested values with the board specs and didn't go by marked ratings on the caps. I found that caps with the same marked ratings to the original caps were much smaller, when I simply started testing various values in the same voltage, the caps I ended up with were mostly the same size as the one's I replaced. Some were off as much as 25%. At the time I had just figure they were Chinese knockoffs but they've been fine in service since then. I only fixed the sound card as an experiment to see what had failed. The company who made the card refunded the purchase price due to so many failures due to bad caps. I guess I just wanted to know if the issue was really just bad caps, and apparently it was.
I just chocked the fact that the new smaller caps were mislabeled since those with the proper value turned out to be the same size as the originals.
I relabled the caps as I tested them and those that I marked then, still read the same today, three years later.
The old caps on that sound card had blown the tops off, I never heard anything or saw any leakage. Just one day the card was dead. When I opened the computer up, I couldn't help but notice all the caps split open on top. The sound card was only a year old when that happened. I had replaced it at the time but fixed it later for use in another machine. I eventually put it back into my main computer.
If testing a cap, how do I know what the ESR should be? I don't see it listed in the catalog pages.
What I did when I replaced those caps was to match tested values with the board specs and didn't go by marked ratings on the caps. I found that caps with the same marked ratings to the original caps were much smaller, when I simply started testing various values in the same voltage, the caps I ended up with were mostly the same size as the one's I replaced. Some were off as much as 25%. At the time I had just figure they were Chinese knockoffs but they've been fine in service since then. I only fixed the sound card as an experiment to see what had failed. The company who made the card refunded the purchase price due to so many failures due to bad caps. I guess I just wanted to know if the issue was really just bad caps, and apparently it was.
I just chocked the fact that the new smaller caps were mislabeled since those with the proper value turned out to be the same size as the originals.
I relabled the caps as I tested them and those that I marked then, still read the same today, three years later.
The old caps on that sound card had blown the tops off, I never heard anything or saw any leakage. Just one day the card was dead. When I opened the computer up, I couldn't help but notice all the caps split open on top. The sound card was only a year old when that happened. I had replaced it at the time but fixed it later for use in another machine. I eventually put it back into my main computer.
If testing a cap, how do I know what the ESR should be? I don't see it listed in the catalog pages.
Pass DIY Addict
Joined 2000
Paid Member
IMHO, the caps in this unit are so old that they are not worth testing. I recommend replacing ALL electrolytics with new caps of similar uF and voltage ratings equal to or higher than original. That power supply board has been slow cooked for a while - my guess is that the caps started drying out and began to short - placing heavy strain on the large power resistors and the power regulator over time. Eventually, the caps completely shorted, thus your blown fuses.
I would not recommend trusting NOS caps from the 1990s - they are approaching 30 years old and should be tossed. New caps are cheap.
My recommendation would be to replace ALL caps and then power up the amp with a light bulb tester or a variac and a current meter to see what happens. If you are lucky, only the caps are bad and they didn't cause much down-stream damage.
I have repaired a ton of electronics over the years and the culprit has ALWAYS been old/dead caps. See here for more details.
I would not recommend trusting NOS caps from the 1990s - they are approaching 30 years old and should be tossed. New caps are cheap.
My recommendation would be to replace ALL caps and then power up the amp with a light bulb tester or a variac and a current meter to see what happens. If you are lucky, only the caps are bad and they didn't cause much down-stream damage.
I have repaired a ton of electronics over the years and the culprit has ALWAYS been old/dead caps. See here for more details.
Last edited:
Most ESR meters come with a table of ESR versus capacitance, based on typical typical capacitor grades. This is often part of the meter's front panel artwork. There is a problem though, in that different grade caps have different ESR so you need to learn a little about the grades used and get some testing experience to know what is acceptable by comparison with similar caps, new and old grades, if you can. It's not an exact science but a bad cap is real bad, and that becomes obvious.
The link is to another forum thread and shows several ESR tables, all different and the following discussion makes the point clear. ESR Values for Electrolytic Caps - Page 1
Pass DIY Addict
Joined 2000
Paid Member
Maybe I'm oversimplifying things in my approach, but ESR measures may or may not reveal a bad cap - it is not always obvious at all. Caps may measure as good in a battery powered meter that applies microvolts and millliamperes of test current, only to fail when an actual working voltage and/or several amps of current are applied to them in circuit. Since most meters require you to remove at least one leg of the cap to test it, go the little bit of extra and just REPLACE the cap. ALL of them. This is a nice Fisher amp, it's not a rare or exotic piece of esoteric audio heritage that should be carefully preserved with original parts.
New caps are both inexpensive and easy to find, it just isn't worth the time and trouble to fiddle with the old ones and the possibility of overlooking a bad cap that measures as good. Ditch 'em all...
New caps are both inexpensive and easy to find, it just isn't worth the time and trouble to fiddle with the old ones and the possibility of overlooking a bad cap that measures as good. Ditch 'em all...
That's what I was looking to see, something to give me a ballpark idea where things should be not having anything to go on.
Now on this Fisher power board, I get the following readings: (all are Nichicon 50v rated caps):
100uF 173uF .02Ω ESR
100uF 9983pF 55Ω ESR
220uF 197uF 22Ω ESR
330uF 333uF .49Ω ESR
330uF 790uF 66Ω ESR
(The way I see it, only the one 330uF cap tests okay).
I tested each cap several times on both testers I've got here and got the same readings give or take a point or two. I had little doubt these would be bad, just due to the burn marks and heat they've seen let alone age.
The problem will be finding a source that can supply all of them for a fair price. What I'm running into is that each supplier has only one or two sizes, and shipping from four or five suppliers adds up to far more than the parts. I have five amps here that I need parts for and have lists compiled but the parts so far are all over the place.
Size wise, I'm seeing that the new caps will be about 30% of the size of the originals too. This makes me think I should be looking to increase the values and voltages a bit on this board?
Pass DIY Addict
Joined 2000
Paid Member
Not knowing exactly what function each cap performs in the circuit, I would recommend replacing it with a new cap that is as close to the original uF value as possible (+ or - 10% won't make a difference). It is perfectly fine to use any cap with a higher voltage rating that originally specified. Physical size is irrelevant, provided new caps are same or smaller size.
Replacing 4 out 5 original caps is a bad plan. If the others have failed due to old age, what makes you think the last one is not on the verge of failing, too? Replace ALL caps.
Replacing 4 out 5 original caps is a bad plan. If the others have failed due to old age, what makes you think the last one is not on the verge of failing, too? Replace ALL caps.
I don't understand how you can't find common replacement parts together in one supplier's lists. Are you being too picky over the value, voltage rating or dimensions when, as Eric points out, 10% will be fine? These components generally have at least a 20% tolerance, so precise matches won't help.
I'd agree that buying caps in the quantities you need for a one-off refurb will be expensive, wherever you look. This often escapes the pro. repairers, who mostly buy in cheap, re-stock quantities. Have a look at MCM/Newark or Jameco. Here's Jameco's passive components, just select capacitors and refine if need be: Passive Components | Jameco Electronics.
I'd agree that buying caps in the quantities you need for a one-off refurb will be expensive, wherever you look. This often escapes the pro. repairers, who mostly buy in cheap, re-stock quantities. Have a look at MCM/Newark or Jameco. Here's Jameco's passive components, just select capacitors and refine if need be: Passive Components | Jameco Electronics.
I looked at Jameco, out of the caps I need for the power board alone, they only have two listed that match specs, I don't see a 330uF 50v radial, or anything close to that in any voltage. The stated sizes are less than 1/4 the size of the originals.
How do I determine the value of some of the smaller caps that are only marked with a temp rating? There's also a bunch of caps marked only 1/16, and they're all different physical sizes. Some have no markings on them at all, especially on the tuner board.
There's also a huge range of voltage ratings on the caps on the amp board, most are 50v, but some of the tiny caps are 16v and 100v. Most of the caps in this Fisher are Nichicon, the orange caps have no brand but have the Chem-Con logo on the side. Nearly all the smaller caps have no value, only a few on the amp board have the value and voltage listed on the side. Most have only the temp rating, 85°C or 105°C, down one side and the black polarity stripe down the other.
I only need three values/sizes for the power board but I figured that if I'm going to replace those, I might as well do them all, but its those unmarked or oddly marked caps that stump me. Plus what to do with the 330uF axial caps. I can find axial caps in the right value but that company has only that one size. They don't carry any of the other values.
I looked at mouser and as I go through the long list of caps I need for this and a few other projects, I find that they have only a couple of the values too, (one of the values I need for another amp is 100uF/100v. The original caps are huge, 50mm tall, 16mm wide. When I compare the originals to the new parts, the size is less than 1/8 the original size, which becomes a big problem when it comes to mounting them on the board which has holes that are too wide for the leads to reach. My thought was to go higher in voltage but I don't see any listed higher than 100v in that value or anything close. The specs on that amp list two specs for that location, they list a 100uF to 220uF value, most were built with 100uF caps. Even if I go to the max value the caps are still way too small to span the pin holes in the board.
The 220uF 50V caps on the Fisher power board measure 32x 18mm. The replacements today would be 16 x 10mm from Jameco. Roughly half the original size with the same voltage. My first thought would be to go to a higher voltage since I have the space but they don't list a higher voltage anywhere close in value.
I agree that the right answer is to replace all the caps, it appears that none are likely to be usable, if those on the power board are bad, those on the other boards are likely to be in the same shape. A few of the 220uF caps on the other boards are leaking just like those on the power board. What ever leaked out of them, did so then dried up. It looks like road tar.
The leakage is more obvious on caps that sit upside down. I had thought at first it was some sort of glue but its not on the boards, just the cap itself when the cap is upside down.
So far all the caps with the oily tar on them have been way off in spec with high resistance.
How do I determine the value of some of the smaller caps that are only marked with a temp rating? There's also a bunch of caps marked only 1/16, and they're all different physical sizes. Some have no markings on them at all, especially on the tuner board.
There's also a huge range of voltage ratings on the caps on the amp board, most are 50v, but some of the tiny caps are 16v and 100v. Most of the caps in this Fisher are Nichicon, the orange caps have no brand but have the Chem-Con logo on the side. Nearly all the smaller caps have no value, only a few on the amp board have the value and voltage listed on the side. Most have only the temp rating, 85°C or 105°C, down one side and the black polarity stripe down the other.
I only need three values/sizes for the power board but I figured that if I'm going to replace those, I might as well do them all, but its those unmarked or oddly marked caps that stump me. Plus what to do with the 330uF axial caps. I can find axial caps in the right value but that company has only that one size. They don't carry any of the other values.
I looked at mouser and as I go through the long list of caps I need for this and a few other projects, I find that they have only a couple of the values too, (one of the values I need for another amp is 100uF/100v. The original caps are huge, 50mm tall, 16mm wide. When I compare the originals to the new parts, the size is less than 1/8 the original size, which becomes a big problem when it comes to mounting them on the board which has holes that are too wide for the leads to reach. My thought was to go higher in voltage but I don't see any listed higher than 100v in that value or anything close. The specs on that amp list two specs for that location, they list a 100uF to 220uF value, most were built with 100uF caps. Even if I go to the max value the caps are still way too small to span the pin holes in the board.
The 220uF 50V caps on the Fisher power board measure 32x 18mm. The replacements today would be 16 x 10mm from Jameco. Roughly half the original size with the same voltage. My first thought would be to go to a higher voltage since I have the space but they don't list a higher voltage anywhere close in value.
I agree that the right answer is to replace all the caps, it appears that none are likely to be usable, if those on the power board are bad, those on the other boards are likely to be in the same shape. A few of the 220uF caps on the other boards are leaking just like those on the power board. What ever leaked out of them, did so then dried up. It looks like road tar.
The leakage is more obvious on caps that sit upside down. I had thought at first it was some sort of glue but its not on the boards, just the cap itself when the cap is upside down.
So far all the caps with the oily tar on them have been way off in spec with high resistance.
You need to go through the selection process more carefully. Here is what I found for the above item:
RA330/50-R: Jameco Valuepro : Capacitor Electrolytic Radial 330 uF 50 Volt 85c 20% 10x16x5mm : Passive Components
As discussed earlier, new axial caps are few and far between. The type is obsolete in all but a few applications where point-to-point wiring still exists. That means adapt the PCB to suit radials or use a higher capacitance value. Up to 50% higher capacitance or 2 smaller caps in parallel should not be a problem in a power supply. So, if you can't find 330uF use 470uF, adapt a radial type or parallel some smaller value axial types. Your option.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.