Hey, Garey - I guess we got tripped-up over terminology. Yeah, the "kidney bean" is the only 3000 pf cap on the PTO board.
Looks like I'll put that tubular one back in tonight. I have only a ceramic 3000 pf right now but at least that will give me proof-of-concept. When working on old stuff without exact replacements on-hand, I'm always careful to get the part out without damaging it if possible. I should be able to get that cap back in with almost exact duplication of lead dress. Replacing the 3000 pf should be a breeze by comparison. 73 and thanks for your help. I'm hoping the B-Line I bought that I'm waiting for will have fewer problems ;-) Steve, W1ES -----Original Message----- >From: Garey Barrell <[email protected]> >Sent: Aug 11, 2011 10:19 AM >To: Steve Wedge <[email protected]> >Subject: Re: [Drakelist] Okay, so what IS the big brown thing? > >Steve - > >No, the 'long tubular' cap is another style of t/c cap. I've only seen those >in two PTOs over the >years, I suspect it was a 'fill-in' or a special value that wasn't available >in glass. The cap I've >been referring to is what you are calling a 'kidney bean' is the Dur-mica >silver mica that has been >an occasional problem, either the cap developing internal 'whiskers' of silver >forming intermittent >paths, or even just poorly soldered leads. It's not a common failure, but >we've pretty well >eliminated all the 'common' problems!! :-) > >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 ><www.k4oah.com> > > >Steve Wedge wrote: >> I think we're talking about two different components. >> >> There is a 3000 pf, normal-looking "kidney bean" SM cap near one of the rear >> corners of the board. It is soldered to the board in classic manner with >> short leads. >> >> The one I've been assuming is the "dog-bone" is the longish, tubular, light >> brown with some waxy coating. One lead is soldered to a normal land on the >> PCB, the other passes through a solderless hole and is soldered to the >> eyelet in the phenolic where the front end of the inductor is also soldered. >> >> Should I not bother tryint to replace the longish, tubular cap that has the >> flying lead to which the glass caps are attached? I may have misinterpreted >> what people call a "dog-bone". That large one that I removed is unlike any >> other capacitor I've seen. >> >> One good thing about this whole thing, Garey, is that I'm getting wicked >> good at removing/installing the PTO assembly ;-) >> >> Steve, W1ES >> >> -----Original Message----- >>> From: Garey Barrell<[email protected]> >>> Sent: Aug 11, 2011 9:33 AM >>> To: Steve Wedge<[email protected]> >>> Subject: Re: [Drakelist] Okay, so what IS the big brown thing? >>> >>> The tubular, white painted 'glass' caps are NOT silver mica. They are >>> generally small value caps >>> formed by metal flashed in the inside and outside of the glass tube. SOME >>> are temperature >>> compensation types, some are not. They should NOT be changed except as a >>> very last resort, as they >>> will almost certainly affect the t/c and/or linearity of the PTO. Their >>> value, t/c and placement >>> are all part of the original setup of the PTO. They ARE extremely stable >>> over time because of the >>> glass dielectric. They WILL also break! >>> >>> I have never been able to locate the code for this type of cap, it isn't >>> the old "Body-End-Dot" >>> style, and apparently hasn't been made since the 60's. This type of t/c >>> cap is now made in the >>> typical tan ceramic disc form. >>> >>> The only cap to change is the 3000 pF brown epoxy dur-mica. Be sure the >>> leads are well soldered, >>> they are a little larger than the rest and take a little more heat. 'Cold' >>> solder joints are a >>> problem here because of this. >>> >>> 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 >>> <www.k4oah.com> >>> >>> >>> Steve Wedge wrote: >>>> Sorry - I meant dur-mica and not glass. Am I correct that its value is 80 >>>> pf? I'm trying to get the code online but haven't found it yet. >>>> >>>> SW>> >>>> >>>> -----Original Message----- >>>>> From: Garey Barrell<[email protected]> >>>>> Sent: Aug 10, 2011 10:15 PM >>>>> To: Steve Wedge<[email protected]> >>>>> Cc: Drake List<[email protected]> >>>>> Subject: Re: [Drakelist] Okay, so what IS the big brown thing? >>>>> >>>>> Steve - >>>>> >>>>> No, that is a glass cap. Painted white with marks of color coding. The >>>>> numbers refer to the >>>>> capacitance AND the temperature characteristic. These hardly EVER go >>>>> bad. The large, brown cap is >>>>> the Dur Mica silver mica cap and is the one that we are trying to >>>>> eliminate as the problem. Try to >>>>> not disturb the arrangement of the leads of these 'flying' caps as they >>>>> are part of the t/c and >>>>> affect the temperature compensation. Others are just small value >>>>> trimming caps to fine tune the >>>>> coil and affect the linearity of the PTO. >>>>> >>>>> 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 >>>>> <www.k4oah.com> >>>>> >>>>> >>>>> Steve Wedge wrote: >>>>>> I was assuming that the "dogbone" cap in the PTO was the one that goes >>>>>> to the front of the >>>>>> inductor, has two white "dumb-bell" caps connected to that lead and then >>>>>> connects at the other end >>>>>> to what is actually the 3000 pf SM. It appears to be some sort of >>>>>> ceramic and is marked (from the >>>>>> end) BRN-WHT-ORG-BLK-RED, which, if normal colour codes were used would >>>>>> be 1-9-3-0-2 or >>>>>> 2-0-3-9-1. It seems to correspond in placement to C143-144-145, except >>>>>> that the two dumb-bells >>>>>> aren't in parallel. >>>>>> Isn't this the capacitor that has gone funky on a few PTO's? >>>>>> >> _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
