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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


3 posters

    Carbon Resistors on Power Supply Caps replace or not

    bubbasweet
    bubbasweet

    Posts : 87
    Join date : 2016-03-14

    Carbon Resistors on Power Supply Caps replace or not Empty Carbon Resistors on Power Supply Caps replace or not

    Post by bubbasweet Tue Aug 17, 2021 2:46 pm

    When replacing the Multi Lug High voltage Can caps in PAMs, PAS2s and PS-1, do you guys replace the Carbon resistors at the same time on the HV multi lug caps with new, or move em over? Any pro or con to leaving them original? if they measure good?"
    peterh
    peterh

    Posts : 1581
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Carbon Resistors on Power Supply Caps replace or not Empty Re: Carbon Resistors on Power Supply Caps replace or not

    Post by peterh Tue Aug 17, 2021 3:49 pm

    bubbasweet wrote:When replacing the Multi Lug High voltage Can caps in PAMs, PAS2s and PS-1, do you guys replace the Carbon resistors at the same time on the HV multi lug caps with new, or move em over? Any pro or con to leaving them original? if they measure good?"
    I do not replace the "Multi Lug Cap". I install a new power board , one example of such a board
    is z-psu https://www.erhard-audio.com/Power_Supply_Kits.html
    or similar board. This way i get :
    - new B+caps of a modern model that can be substituted in the future
    - a completely new filament chain that replaces Se rectifier and 2 caps.
    all at a cost lower then a replacement of the multi cap costs

    bubbasweet
    bubbasweet

    Posts : 87
    Join date : 2016-03-14

    Carbon Resistors on Power Supply Caps replace or not Empty Re: Carbon Resistors on Power Supply Caps replace or not

    Post by bubbasweet Tue Aug 17, 2021 7:22 pm

    I have already done all the filament and rectifier etc in past. My question is really related to should these old carbon resistors be changed or if they measure OK should I use em and just re solder. I have already chosen to use the multi lug caps THX

    Is there any reason or benefit like noise or such that can require a change out to new resistors here?
    Bob Latino
    Bob Latino
    Admin

    Posts : 3074
    Join date : 2008-11-26
    Location : Massachusetts

    Carbon Resistors on Power Supply Caps replace or not Empty Re: Carbon Resistors on Power Supply Caps replace or not

    Post by Bob Latino Tue Aug 17, 2021 8:33 pm

    bubbasweet wrote:I have already done all the filament and rectifier etc in past. My question is really related to should these old carbon resistors be changed or if they measure OK should I use em and just re solder. I have already chosen to use the multi lug caps THX

    Is there any reason or benefit like noise or such that can require a change out to new resistors here?

    Carbon composition resistors tend to change their value over an extended period of time. Usually they will go UP in value over a LONG period of time (20 to 50+ years). Personally, I would change out all the carbon composition resistors in an older piece of audio gear. Any modern resistor like a metal film, metal oxide or carbon film resistor will hold their value much better than a carbon composition resistor. If you have a dual channel amp that is 50 years old, there is now a good chance that the two channels don't really match that well anymore because of carbon composition resistor value "drift".

    Bob
    peterh
    peterh

    Posts : 1581
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Carbon Resistors on Power Supply Caps replace or not Empty Re: Carbon Resistors on Power Supply Caps replace or not

    Post by peterh Wed Aug 18, 2021 4:51 am

    bubbasweet wrote:I have already done all the filament and rectifier etc in past. My question is really related to should these old carbon resistors be changed or if they measure OK should I use em and just re solder. I have already chosen to use the multi lug caps THX

    Is there any reason or benefit like noise or such that can require a change out to new resistors here?
    No there is no reason to keep old resistors. They have been subject to bending and soldering stress, better to use brand new resistors that could be formed perfectly.
    No need for CC here, but do check that the replacement resistors has equal or higher wattage rating.
    bubbasweet
    bubbasweet

    Posts : 87
    Join date : 2016-03-14

    Carbon Resistors on Power Supply Caps replace or not Empty Re: Carbon Resistors on Power Supply Caps replace or not

    Post by bubbasweet Thu Aug 19, 2021 10:41 am

    Finally got rid of the hum on my PAMs. It was the Cap in the PS-1. I replace with a new 30uF - 50uF 450V. Now it is silent. I had replaced these caps before but hum did not dissapear so I put the can cap back, which is why I was looking else-where. definitely a done PS cap so obvious but I had swapped em. THX Peter H for all your help in past.

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    Carbon Resistors on Power Supply Caps replace or not Empty Re: Carbon Resistors on Power Supply Caps replace or not

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