[Drakelist] Drake PTO (Yet Again!)

Hi Guys, To-day I had occasion to take the top cover off of my T-4X transmitter, & examine the PTO mechanics a bit... Question: how "normal" is it for the frequency to "jump & jiggle" whenever even the lightest of physical force is applied to the yoke...? Is this expected, or should the freque

[Drakelist] FS: SPR-4 and MS-4

All; Thinning the herd a bit here at home and have an SPR-4 and MS-4 for sale. Both are in very good condition and work fine. The SPR-4 includes the original manual. $225 plus shipping for both. If interested respond by private e-mail. Pictures available on request. Tom -- Tom Swisher, WA8P

Re: [Drakelist] L75 What is the max grid current? (Correction)

This is what I get for staying up past my bedtime Correct Grid current for a single tube should be 1/2 of two tube current or _110 mA_. I don't know about the L-75, but it's a single 3-500Z. The L-4B uses a two 3-500Z tubes, and the recommended max Grid current is 220 mA for the pair. T

Re: [Drakelist] L75 What is the max grid current?

I don't know about the L-75, but it's a single 3-500Z. The L-4B uses a two 3-500Z tubes, and the recommended max Grid current is 220 mA for the pair. The Grids are pretty tough, dissipation is about 20W, so there is a little leeway, as opposed to external anode tubes which tend to 'poof' Grids

[Drakelist] L75 What is the max grid current?

I have finally found a L75 after a long search. I am driving it with my TR7. The manual gives maximum output on CW at .375 ma plate but no grid current value? Same for SSB, no grid value. RTTY and SSTV have values listed for both plate and grid. Any one have a L75 and can supply what plate and

Re: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")

Dennis - That's what I get for trusting memory.. :-) I thought they were opposite. The original is the DurMica, dipped brown epoxy. So it is/was silver mica. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Dennis Monticelli

Re: [Drakelist] R-4A PTO - more attempts

Try touching a hot iron briefly to the ends of the donut caps. Sometimes these joints crystalize. David Assaf, III W5XU From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Steve Wedge Sent: Sunday, July 31, 2011 4:51 PM To: drakelist@zerobeat.net Subj

Re: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")

Depending upon the maker and the value of capacitance, a SM will exhibit about +30 to 100PPM. Polystyrene is a little more consistant at around+125PPM. Both cap types are popular when combined with iron powder cores of low mu because they buck the mild negative TC of the core. Polystyrenes are ha

[Drakelist] R-4A PTO - more attempts

Did the braid addition and changed the zener. No joy yet - thinking more and more it's that capacitor - looking for local friends' junkboxes but will probably spend a little to order one. Lots of cheap ones on Fleabay, it turns out. Steve Wedge, W1ES/4 "I can't complain, but sometimes I stil

Re: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")

Steve - Stick with the 'dog-bone'. Hard to beat a silver mica for temperature stability. PLUS EVERY capacitor has 'some' temperature sensitivity, just a matter of how much, and _which way_! I'm going from memory here, but as I recall a silver mica has a very slight negative tempco

Re: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")

Articleseems to be aimed at lower frequency analogue use rather that free running oscillators. It doesn't mention temperature coefficient. On 07/31/2011 08:15 PM, Paul Christensen wrote: Steve, Analog Devices has produced a nice summary of capacitor dielectric types: http://www.analog.com/lib

[Drakelist] RCS-4

Anyone have any experience or insight into resurrecting an RCS-4. I haven't really looked at either piece yet. The control head has been sitting in my attic for abt 20 years and the remote antenna switch has been sitting outside in the elements. Off subject, I also have a Ham-II/CD44 rotor a

Re: [Drakelist] Capacitor type for PTO C146 ("The Dogbone")

Steve, I would make that decision once you get to the root cause of the PTO instability. Between now and then if you want to try a Polystyrene cap to simply rule out the dog-bone cap, I think it's fine. Both Polystyrene and silver mica are both highly temperature stable. Keep in mind that th

[Drakelist] Capacitor type for PTO C146 ("The Dogbone")

I'm looking at options for replacing the "dogbone" 3000 pF SM cap in the PTO. I've long heard the polystyrene caps are stable and of high quality. What's your opinion of using a polystyrene cap in place of the SM unit at C146? Steve Wedge, W1ES/4 "I can't complain, but sometimes I still do."