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JDW

HD20SC SONY PSU Schematic for Recapping, ESR

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I'm in the planning process to recap the SONY PSU housed inside my Apple HD20SC external hard drive enclosure.  (I might make a video.)  I've got a Mouser cart filled with mostly Organic Polymer Aluminum Electrolytic capacitors for that PSU (see below), which have very low ESR down to between 12mΩ and 43mΩ.  There are many benefits to low ESR capacitors, and the life rating on them is very high compared to regular aluminum electrolytics.  But my concern is that the output of some switch-mode (switching) power supplies can ring if the ESR of the output capacitance is too low (as per the data sheets of many switch mode controllers), so do any of you have a schematic?  If not, have any of you used a large number of Organic Polymer capacitors in your vintage Mac PSU recap jobs with success?  (I'm asking about power supplies here. Non-PSU applications don't matter much.  Mostly those cases are a decoupling/bypass caps which hold up the voltage in times of voltage dips, and those caps benefit from very low ESR.)

 

Here's my Mouser list of mostly polymer caps:

 

C226: 22uF 35V, D=5.2mm -- (Mouser: A759BQ226M1HAAE075)

C202: 47uF 25V, D=5.2mm -- (Mouser: A750EK476M1EAAE040)

C222: 47uF 25V, D=5.2mm -- (same as C202, so get 2pcs)

C109: 150uF 400V, H=32mm, D=25.8mm -- (Mouser: 860021383023)

C110: 4.7uF 350V H=32mm, D=12.8mm -- (Mouser: UPM2G4R7MHD)

C210: 330uF 16V, D=8.1mm -- (Mouser: RL81C331MDN1KX)

C215: 470uF 10V, D=8.1mm -- (Mouser: RNE1C471MDN1)

C213: 22uF 100V, D=10.2mm -- (Mouser: A759MS226M2AAAE045)

C124: 2200uF 10V, D=12.7mm -- (Mouser: UHE1C222MHD)

C209: 2200uF 16V, D=12.7mm -- (just buy the same as C124, so get 2pcs)

 

CR-35 daughter card:

C181: 100uF 10V, D=8.1mm, H=13.5mm -- (Mouser: RNS1A101MDN1KX)

C182: 100uF 10V, D=8.1mm, H=13.5mm -- (same as C181, so get 2pcs)

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Hmmm...  Only 6 views and nary a reply.  Well, I shall talk to myself then...  (Assuming @trag or @Bolle or @joethezombie or @techknight don't wish to join in.)

 

Why consider recapping with solid organic polymer aluminum electrolytic capacitors?  Because in addition to low ESR (which is sometimes very beneficial), they also offer longer life than fluid-filled electrolytic capacitors (in addition to the fact that the solid electrolyte of polymer caps won't leak).  Have a look at this life chart:

 

Table_1_Lifetime_overview_with_different_ambient_temperatures.jpg.a421f60af757ce3e81ece75d58f3f3ae.jpg

 

I suspect the ambient internal air temperature of even our upgraded Compact Macs won't exceed 65°C, hence the stark contrast between the expected life of polymer caps versus fluid-filled electrolytics.

 

The main downside to polymer caps is their leakage current, which is often on order of a couple hundred microAmps to even just over 1mA.  Most fluid-filled caps have leakage currents far lower -- maybe 20uA or less.  But since we are not recapping battery powered machines here, the detrimental effects of polymer capacitor leakage is not so significant.

 

Again, I look forward to hearing your thoughts.

 

Thanks.

Edited by JDW

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