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*FORUM GUIDELINES* Please make the 'Subject' line reflective of the content of the message, especially if you are answering a digest mode post. Members are asked to make sure that they "sign" their

Last call for my last Rhode and Schwarz polyscop. Only ?20. If no takers, I'll scrap it for the valves (EL84's) and metal for my friends machine shop Collection Hampshire UK 73, Martin M0MGA

Hi, A little more detail. Using the variac to bring up the HT slowly is good. Probably best to put the system switch in Standby as this puts a fixed load on the HT line and isolates the rest of the

You have the best means of powering-up after a long period already. . . Capacitor electrolyte in high capacity smoothing power supplies in particular are notorious for being ineffective: possibly

My RA17 has been in storage unpowered since 2006. Prior to that it was in tip top condition having been serviced by Rob Filby in December 1999. I know it was unwise and neglectful of me not to power

Craig further to 40Mhz BPF: I had a grest interest in filters many years ago and at that time used Terman as the main reference source. The most comprehensive full mathematical analysis of filters in

Hi folks - The mesh covers appear to have been factory fitted from roughly mid-1969 in both RA17s and 117s. I currently own at least two RA17s with them (#12681 not dated but appears to be early 1971

A sensible replacement would be a good thing. I've rivetted a few finger strips back onto their cover plates, but individual fingers are prone to snap off after a few cycles. Colin mm1aps.

Thanks Craig, You must have a seriously detailed archive library on Racal ... :-) The number of Racal equipments of that era that I have seen or worked on is not a large number and not in any

Hi Douglas A few posts ago, in a long meandering thread, I made an assertion that Racal introduced a mod to replace the spring edged covers with knitted mesh versions. You said you'd never seen any.

Its not hard ... as I said, i did it. You don't need to make special covers. I just used two pieces of circuit board, positioned with a tiny slot, a bit away from the coil under test, with just enough

Many thanks for the very detailed post Douglas. Although Zverev's seminal filters book, difficult to get a grip on, was only published in 1967 - and hence post-dates the RA17/117 etc series. Although

Craig, Re, 40Mhz BPF covers. I have seen a number of Ra17 and Ra117 series, and the MA79 too based on the same circuitry, but never come across filter covers with mesh. They all possessed the

Douglas Quizzing David in more detail, it looks like a pair of sacrificial covers is needed, with additional small holes through which a single exciting loop from a sig gen and single spectrum

Craig, This Zverev reference is very interesting indeed. A completely new angle on filters for me. I must look more into it. I'm still dubious about the practical application for alignment with the

A similarly surprising to me filter (when I first saw it without the background of why it works) is the crystal ladder filter (e.g.

Douglas This is a compedium of the mails on this topic from UK Vintage Radio ( https://www.vintage-radio.net/forum/index.php ), David is a list admin, with the handle "Radio Wrangler" Craig "There is

Craig, Thanks for your interesting reply. The method you described shorting of the 40Mhz resonators in turn surprises me that it is reported to work, but admit I fail to understand it at all. If it

I tried that method as most of the caps had to be replaced.. Apparently only the two adjacent coils need be shorted.I did discover upon sweeping that the center was a bit off, so I redid it with the

I'm lucky enough to have a R&S Swob II that I bought from Rob Filby donkeys years ago (fully functional with all the probes) and a CT501 that I bought for a bewilderingly low ?40 maybe 10 years ago -