[TowerTalk] Fwd: TowerTalk Digest, Vol 180, Issue 26

[Hans Hammarquist]

 No really. Yes, if they all are connected in serial or parallel you get a total of 31,200 pF. If you, on the other hand make two seril chains and parallel then you get the 1950 pF mentioned. They probably used enough in serial to get the needed voltage rating and/or two in parallel to get the needed current rating. Not uncommon to do. I would believe one cap of 2000 pf would be much more expensive than the 8 used. 



I don't know what voltage or current rating is required but I have used the parallel/serial trix in other applications. Worked great. In one of my applications I had to use sixteen (16!) 0.1 uF caps to get the right current rating. One 1.5 uF cap burnt up.



73 de,


Hans - N2JFS

 

 

-----Original Message-----
From: Wilson Lamb <infomet at embarqmail.com>
To: towertalk <towertalk at contesting.com>
Sent: Sun, 17 Dec 2017 12:24
Subject: Re: [TowerTalk] TowerTalk Digest, Vol 180, Issue 26

There's a math problem here too....
WL

> 
>    1. MFJ-998 autotuner problem (Roger D Johnson)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Sat, 16 Dec 2017 15:10:03 -0500
> From: Roger D Johnson <n1rj at roadrunner.com>
> To: Towertalk Reflector <towertalk at contesting.com>
> Subject: [TowerTalk] MFJ-998 autotuner problem
> Message-ID: <4944bc09-0723-5f26-bbcc-e18002def723 at roadrunner.com>
> Content-Type: text/plain; charset=windows-1252; format=flowed
> 
> I recently discovered a problem with my MFJ-998 tuner that might also be a 
> problem with other tuners.
> 
> There are two banks of series/parallel capacitors that are switched on the input 
> side of the L network to
> 
> match low impedance loads. One bank consists of (8) 3900pf capacitors that total 
> 1950 pf. In my tuner
> 
> these caps were only 390pf!!
> 
> If these PC boards were populated using a machine getting parts from a reel, 
> there are probably more
> 
> tuners out there with the wrong caps.
> 
> 73, Roger N1RJ
> 
> 
> 
> 
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> Subject: Digest Footer
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> ------------------------------
> 
> End of TowerTalk Digest, Vol 180, Issue 26
> ******************************************

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