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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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replacement cpacitors
When restoring the old tube equipment (tube receivers ) does it make any difference if the old paper capacitors are replaced iwth the ceramic disk or should another type be used ? I know for RF one needs to use capacitors that are rated for rf but in the audio stages does it really matter what kind of capacitor is used as long as it is the correct value ? Reason for asking is that I bought an old receiver that someone has replaced many of the capacitors. The book says pape capacitors for some but they have been replaced by the ceramic disk type. |
#2
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replacement cpacitors
On Wednesday, 10 October 2018 20:02:23 UTC+1, Ralph Mowery wrote:
When restoring the old tube equipment (tube receivers ) does it make any difference if the old paper capacitors are replaced iwth the ceramic disk or should another type be used ? I know for RF one needs to use capacitors that are rated for rf but in the audio stages does it really matter what kind of capacitor is used as long as it is the correct value ? Reason for asking is that I bought an old receiver that someone has replaced many of the capacitors. The book says pape capacitors for some but they have been replaced by the ceramic disk type. a lot of ceramic caps suffer severe loss of capacity once a few volts are applied. If it works fine, great. If the limited amount of original bass has vanished, that might be why. If rf drifts all over the place as mains voltage varies... It depends on the type of ceramic, some don't suffer this but most do. NT |
#3
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replacement cpacitors
Mylar and polyester film caps are better than ceramic disk type for most purposes. Ceramic disk types are better than foil and paper if the foil and paper caps are more than a few hours old.
This also applies to Russian PIO caps - the latest fad in boutique audio. They are no better than they should be, and, for the record, less safe and less reliable than their Mylar/polyester equivalents. What they 'sound' like is irrelevant as unless the initial quality is truly wretched, capacitors of any given class sound no different than other capacitors of that class, whatever the price-tag. Correct value is the key, and then the environment and requirement for precision. Modern Silver Mica caps are very precise, very stable and resist heat and accept harsh environments. Then down the line to mylar, ceramic disc, polyester. But the reality is that a consumer-grade receiver is a very gentle environment overall. Peter Wieck Melrose Park, PA |
#4
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replacement cpacitors
On Wednesday, 10 October 2018 20:55:39 UTC+1, tabby wrote:
On Wednesday, 10 October 2018 20:02:23 UTC+1, Ralph Mowery wrote: When restoring the old tube equipment (tube receivers ) does it make any difference if the old paper capacitors are replaced iwth the ceramic disk or should another type be used ? I know for RF one needs to use capacitors that are rated for rf but in the audio stages does it really matter what kind of capacitor is used as long as it is the correct value ? Reason for asking is that I bought an old receiver that someone has replaced many of the capacitors. The book says pape capacitors for some but they have been replaced by the ceramic disk type. a lot of ceramic caps suffer severe loss of capacity once a few volts are applied. If it works fine, great. If the limited amount of original bass has vanished, that might be why. If rf drifts all over the place as mains voltage varies... It depends on the type of ceramic, some don't suffer this but most do. NT it also can cause nonlinear distortion if C is changing as signal voltage changes. The other cap type to be a bit cautious of in valve kit is polystyrene, the dielectric has low melting point. The issues with electrolytics & paper are relatively well known. Oh, also beware of reduced voltage rails that go very high during warm-up. Caps there might need 400v+ rating despite running at 20v. NT |
#7
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replacement cpacitors
Ralph Mowery wrote:
When restoring the old tube equipment (tube receivers ) does it make any difference if the old paper capacitors are replaced iwth the ceramic disk or should another type be used ? I know for RF one needs to use capacitors that are rated for rf but in the audio stages does it really matter what kind of capacitor is used as long as it is the correct value ? Reason for asking is that I bought an old receiver that someone has replaced many of the capacitors. The book says pape capacitors for some but they have been replaced by the ceramic disk type. ** See: https://www.youtube.com/watch?v=67M7fsbLUIU The author use a 5 digit "Gen Rad" LCR meter to demonstrate differences in various types tempcos. ..... Phil |
#8
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replacement cpacitors
On Thu, 11 Oct 2018 15:38:08 -0400, Phil Hobbs
wrote: NB: the bar on Orange Drops is the side _away_ from the outside foil! CHeers Phil Hobbs WAAT! Why would they want to be different? -- Boris --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#9
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replacement cpacitors
On 10/12/18 4:13 AM, Boris Mohar wrote:
On Thu, 11 Oct 2018 15:38:08 -0400, Phil Hobbs wrote: NB: the bar on Orange Drops is the side _away_ from the outside foil! CHeers Phil Hobbs WAAT! Why would they want to be different? Dunno. I discovered this on Paul Carlson's YouTube channel--he made an outside-foil detector gizmo and tried it out. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com |
#10
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replacement cpacitors
On Friday, October 12, 2018 at 6:17:31 AM UTC-7, Phil Hobbs wrote:
Dunno. I discovered this on Paul Carlson's YouTube channel--he made an outside-foil detector gizmo and tried it out. It would have been a lot cheaper and more convincing to have sacrificed a capacitor and open it up. If it were important, I would pay this price before I put my faith in a claim of a non-standard marking on the part, based on the old adage that extraordinary claims require extraordinary proof. |
#11
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replacement cpacitors
On 10/12/2018 11:06 AM, wrote:
On Friday, October 12, 2018 at 6:17:31 AM UTC-7, Phil Hobbs wrote: Dunno. I discovered this on Paul Carlson's YouTube channel--he made an outside-foil detector gizmo and tried it out. It would have been a lot cheaper and more convincing to have sacrificed a capacitor and open it up. If it were important, I would pay this price before I put my faith in a claim of a non-standard marking on the part, based on the old adage that extraordinary claims require extraordinary proof. Suit yerself, or watch the video. You probably don't believe that tantalums are marked on the positive side either. Carlson wanted a test gizmo for many caps used in his antique radio and test equipment restorations. Some of them are fun, though a bit slow-paced for experts, of course. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com |
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