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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Old October 10th 18, 08:02 PM posted to sci.electronics.repair
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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but they have been replaced by the ceramic disk type.

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Old October 10th 18, 08:55 PM posted to sci.electronics.repair
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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but they have been replaced by the ceramic disk type.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
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Old October 10th 18, 08:59 PM posted to sci.electronics.repair
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Default 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
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Old October 10th 18, 10:25 PM posted to sci.electronics.repair
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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
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Old October 11th 18, 12:51 AM posted to sci.electronics.repair
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In article ,
says...

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.




Thanks, I may replace the 'replaced' capacitors with some of the 'Orange
Drop' ones I have if I ever pull the receiver back out of the case.

I am using it a boat anchor station from around the time I was born
along with a Johnson Viking ll transmitter. By the time I was old
enough to get into electronics much had switched to solid state, but I
did learn enough to do repair work but replace like parts with like
parts except the paper capacitors with the newer tublar type. As
mentioned electrolytics do tend to dry out after 50 years.




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Old October 11th 18, 08:38 PM posted to sci.electronics.repair
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On 10/10/2018 07:51 PM, Ralph Mowery wrote:
In article ,
says...

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.




Thanks, I may replace the 'replaced' capacitors with some of the 'Orange
Drop' ones I have if I ever pull the receiver back out of the case.

I am using it a boat anchor station from around the time I was born
along with a Johnson Viking ll transmitter. By the time I was old
enough to get into electronics much had switched to solid state, but I
did learn enough to do repair work but replace like parts with like
parts except the paper capacitors with the newer tublar type. As
mentioned electrolytics do tend to dry out after 50 years.


NB: the bar on Orange Drops is the side _away_ from the outside foil!

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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Old October 12th 18, 05:22 AM posted to sci.electronics.repair
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Default 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


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Old October 12th 18, 09:13 AM posted to sci.electronics.repair
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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

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Old October 12th 18, 02:17 PM posted to sci.electronics.repair
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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

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Old October 12th 18, 04:06 PM posted to sci.electronics.repair
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Default 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.



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