> Any suggestions? Nothing revolutionary, just replace paper with plastic, ceramic with ceramic, mica with mica. Especially in the latter case use brand-new, not old or even NOS unless tested good in every possible way.
Dave Wise PS - Any message I send that contains Larry H's email address - even in the message body - gets rejected as spam. ________________________________ From: [email protected] <[email protected]> on behalf of Larry H <larry++41gm++@++gmail.com> Sent: Saturday, May 4, 2024 4:57 AM To: R-390 Forum <[email protected]> Subject: Re: [R-390] R-390 Q of Caps and tuned circuits Wow, this is a lot of great posts about the Q of caps. And it is all very good to know. But, my original hope in posting on this subject was to try to find a simple answer that would work all of the time to prevent using the wrong cap in critical circuits. It looks like it isn't going to be easy. Perhaps a list of caps that have a high enough Q is necessary as a guideline. As I noted previously, the MIL-C-5 spec requires the Q to be above 1,333. Is this a good starting point? I have seen a lot of new ceramic caps mentioned that have a high Q, but some of them are surface mount only, no wires attached. Dave, The Q info I referred to came off of the manufactures spec datasheets, I didn't do any measurements. Your post from Apr 30, 2024, 5:30 PM has a lot of great info in it. There are a lot of 390 users/owners worldwide, about 700 unique users per month on our website last year (with June having 897). I suspect that most of them have faced or will face a bad SM cap in a high Q circuit, as SM caps will continually go bad. It would be nice to come up with an easy way to determine if a cap is an acceptable substitution or not. I hope something easy is possible. Any suggestions? Regards, Larry ------------------------------------------------------------------------------------------------------------------------------------------------------- On Wed, May 1, 2024 at 6:28 PM David Wise <[email protected]> wrote: > That 3kV cap is definitely Type II since its capacitance changes as DC > bias is applied. I didn't see before, it has the circled-2 shorthand mark > for Sprague. > > Dave Wise > ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
