At 09:01 -0700 7/7/11, Jeff Walther wrote: >On Jul 6, 3:01 pm, "Nico Vanden Eynde" <[email protected]> wrote: >> Hi, >> >> I'm afraid both of them are not suitable to replace the original 3.9uf BP HF >> capacitor. >> You really need both Bi-polar and Highfrequency since the capacitor is in >> the video circuitry to the tube. >> >> I'm using this one to replace the original capacitor: Digikey part >> PF2395-ND, a Panasonic 3.9UF 250V Metal Polypro cap. > >How do you specify "high frequency" in terms that capacitor >manufacturers use? For example, I don't think it's one of the filter >boxes on Digikey's selection tool for capacitors. > >Tom Lee suggests using four 1uF 50V (or higher V) ceramic capacitors >in parallel in place of C1. It makes a lot of sense. >
I have in my hands: 7 plastic, probably polycarbonate, capacitors PN PM155J/250V-T. I believe they are 250 volt 1.55 microfarad with good AC performance and more voltage than you need.They measure 25 mm X 18 mm X 9 mm 1 very similar PMS225J/250V-T 2.25 microfarad measures 22 mm X 20 mm X 13 mm I also have some tiny 35 V tantalum electrolytic capacitors with wires that might be usable as a series pair connected minus to minus. You would want double the capacity to get a match with the parts in series. They're hard to see and read the part numbers so I'm quite sure they would fit anywhere. But the voltage is a gamble. What is really inside the part that failed is two aluminum oxide capacitors connected that way. The application probably needs a whole lot less capacity with either a ceramic, tantalum, or plastic film. The aluminum oxide dielectric jobs exhibit a fairly high effective series resistance at the low RF frequencies I'm pretty sure you're dealing with. Heating due to that is one of the reasons they fail. If it were me and if it will fit I'd try that 2.25 microfarad job by itself. You can have any one or pair you choose. The last time I did that it went to Belgium - Hi Nico - first class mail without complaints about possible explosives by the US Post Office. -- --> From the U S of A, the only socialist country that refuses to admit it. <-- -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
