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Old 13th September 2015, 11:24 PM   #1
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Default Dynaco PAT 5 line cord caps/res

Can someone explain the purpose of C5/C6 to chassis across the ac power
cord of my PAT 5 BIFET? Also, the 56K res across the unswithed ac outlets?
I have a standing 58vac chassis to earth grd, even w/power sw off and the ac line fuse removed. Thks to all for any help, could not load the schematic. Dale
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Old 14th September 2015, 12:17 AM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by Stevens in SC View Post
Can someone explain the purpose of C5/C6 to chassis across the ac power
cord of my PAT 5 BIFET? Also, the 56K res across the unswithed ac outlets?
I have a standing 58vac chassis to earth grd, even w/power sw off and the ac
line fuse removed.
Those caps are noise filters, and are probably best removed, or replaced with Y rated caps.
The resistor is unusual, and it may be best to remove that as well.
Also check your other components for a similar chassis voltage, just in case.
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Old 14th September 2015, 01:19 AM   #3
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Rayma, thks for your response; I did all that and the vac went away. Just thought maybe all should check your eg to be sure. Also had a Dyna PAT 4 here and it has no such filtering. Again, thanks for your info. Dale
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Old 14th September 2015, 02:03 AM   #4
rayma is offline rayma  United States
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Quote:
Originally Posted by Stevens in SC View Post
Rayma, thks for your response; I did all that and the vac went away. Just thought
maybe all should check your eg to be sure. Also had a Dyna PAT 4 here and it has
no such filtering. Again, thanks for your info. Dale
Sure, probably those 40 year old caps having 120VAC across them constantly were getting leaky.
I built a fair number of Dynaco PAT-5s at that time, and it took an entire day for each one.

BTW, there's a simple upgrade for the PAT-4 to improve the phono stage. You replace the
electrolytic capacitor C3 (100uF) in each channel with a new one several times larger.

Last edited by rayma; 14th September 2015 at 02:13 AM.
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Old 14th September 2015, 10:21 PM   #5
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What's the value for "several times larger: ? Dale
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Old 15th September 2015, 12:27 AM   #6
rayma is offline rayma  United States
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Quote:
Originally Posted by Stevens in SC View Post
What's the value for "several times larger: ? Dale
A 470uF would be good.
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