[Central-Electronics] Fwd: Re: 6550

Thu Jul 25 15:55:24 EDT 2013

Gordon,

  I see you were up late tinkering. So getting zilch to 75 watts is a big deal! You might want to enjoy the moment before proceeding. I bet that RF choke, RFC1 is damaged, and a vital part of the circuitry since it seems odd to me to use a choke that low in inductance. A quick scribble suggests that 23uh on 80M has about 550 ohms inductive reactance. Perhaps that amount of reactance compensates for something that the broadband couplers need.

  Maybe you can build up something with similar characteristics? A DC short in that output circuit might be required to make the power meter behave. Or possibly, the power you see with no drive could be the carrier null being a little off?

  I was hoping the 100V/200V guru's would jump in here...This 20A guy is getting out of his element..

Jim
WD5JKO

________________________________
 From: Gordon <gordon at n6wk.com>
To: central-electronics at mailman.qth.net 
Sent: Thursday, July 25, 2013 12:04 AM
Subject: [Central-Electronics] Fwd: Re:  6550

Jim,
  I removed RFC-1 and now I get 75 watts out on 75 meters. but as I go
higher, each band puts out a little less.
I think I should be looking for a bad Cap at this point, as removing the
inductance made more power.
Another Question, What is up with the little Coax Capacitor thing coming
off the Band coupler Wafer?
    I think Tomorrow, I am going to strip everything out from below the
Finals cage and replace each and every part.
Another clue might be that my Watts meter shows a reading in transmit,
even with the Carrier and Power control at fully counterclockwise, and
the Pot for the Watts turned down as far as it will go.
I should not be showing anything when there is No output and all
controls at minimum. I even get a Watts reading in SSB with No carrier
and no Mic connected...

73,
Gordon
N6WK

On 7/24/2013 7:23 PM, Jim Candela wrote:
>
> Gordon,
>
> "At first I thought it might be the RFC-1,  mine shows 2.3uH when measured out of circuit"
>
>    Looking at the schematic, RFC-1 says .022mh. This converted to uh is 22uh. I'd remove that part temporally and run up the drive. This might explain why you have more power output with increasing frequency.
>
> Jim
> WD5JKO
>
>
> ________________________________
>   From: Gordon <gordon at n6wk.com>
> To: central-electronics at mailman.qth.net
> Sent: Wednesday, July 24, 2013 6:25 PM
> Subject: Re: [Central-Electronics] 6550
>
>
> Hi George and the Group,
> George, I have double checked everything you mentioned..Same results.
>    I tried the new tubes, and as everyone said,  They are NOT the problem.
> I do have a question though. If I disconnect the Coax from the last
> wafer that goes to the RF Sampling circuit and the SO-239 connector,
> Connect my MFJ-259 to the loose end of the Coax  , with a 50 Ohm load in
> the SO-239, shouldn't the MFJ-259 show 50 ohms? Mine is no where near 50
> ohms. If I check the dummy load by itself, it is exactly 50 ohms.
> The only thing on that Coax is the Amps Sampler for the RF output and
> the SO-239. At first I thought it might be the RFC-1,  mine shows 2.3uH
> when measured out of circuit, So it appears to be good.
> I also noticed that the Neutralizing Cap is NOT shown on the 100V
> Schematic I have in front of me.
>
> Gordon
> N6WK
>
>
>
> On 7/24/2013 9:48 AM, George Maier wrote:
>> Hi Gordon:
>>
>> Great job on the 100V; glad to see so much enthusiasm for such a worthwhile
>> project.   Not sure why you are having the RF O/P problems, but your coupler
>> sequence is correct, and the voltages all seem within limits.  Not sure what
>> you've done electrically, but here are a few simple things you may want to
>> consider, if you have not already addressed them.  If you have, please
>> ignore my drivel:
>>
>> 1 - Remove each coupler and apply a high quality contact cleaner to the base
>> pins and the tap connectors; i.e. - Caig Pro-Gol applied with a q-tip or
>> Caig pen.
>> 2 - Same exercise for all of the of the lower stage coil banks, which are
>> all removable.
>> 3 - Be sure to replace the 100 mf - 15V cap (C418) across the PA screen over
>> current relay; they're almost always bad. Also, burnish the relay contacts.
>> 4 - Check the 10 Ohm resistor (R450) that is in series with the power
>> control,  to make sure it's not open., and also the rest of the surrounding
>> connections and circuitry.
>> 5 - Remove all of the chassis interconnecting plugs (carefully) and clean
>> them with Pro-gold also.
>>
>> Those steps should help to eliminate any flaky stuff, unless of course you
>> do have bad tubes along the line.  Generally, I agree with the other folks
>> here, that the PA tubes do not usually fail totally, but hey, it's certainly
>> possible.
>>
>> Keep chugging, Gordon; you'll get there!
>>
>> 73, George - W1LSB
>>
>>
>> -----Original Message-----
>> From: central-electronics-bounces at mailman.qth.net
>> [mailto:central-electronics-bounces at mailman.qth.net] On Behalf Of Gordon
>> Sent: Tuesday, July 23, 2013 9:02 PM
>> To: central-electronics at mailman.qth.net
>> Subject: Re: [Central-Electronics] 6550
>>
>> I am still fighting the no to Low output on my CE-100V.
>> I have ordered new 6550 tubes, but now I am thinking they are nt the
>> problem. The tube tester shows both as very strong I am now wondering if
>> someone has mixed up the Broadband output Coils.
>> Can anyone tell me what color is correct for each band?
>> I have Red for 80, yellow for 40, green for 20, blue for 15 and slate for 10
>>
>> Is this correct?
>> I have now discovered that I get more output as I move up in bands. I get a
>> whole 12 watts out on 20 and 15 meters..LOL Is there a way to test the
>> center Frequency of each of these broadband output coils?
>>
>> Thanks,
>> Gordon
>> N6WK
>>
>>
>>
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