[TenTec] Paragon Problem gets very odd

[Bob McGraw - K4TAX]

I'll chime in here.,

Likely the driver bias pot or  PA bias was open due to it sitting in one 
place for years.  Not unusual.  No bias, maximum PA current.  Then moving 
things around caused it to make contact and all started working.

I suggest noting the physical positions of the pot adjustments and then 
exercising the pots to the extremes several times.  Apply a very small 
amount of contact cleaner and then exercise again.  Set them to the original 
physical position and then with an amp meter in the red lead, adjust for the 
correct current draw.  I do recall the procedure and current values are in 
the manual. {mine is at the shop}

The clue to no bias was the test at about 4.5 volts when the supply went 
into current limit.

73
Bob, K4TAX



----- Original Message ----- 
From: "wade staggs" <tvman1954 at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, July 14, 2012 12:51 PM
Subject: Re: [TenTec] Paragon Problem gets very odd


> *Amazing,*
> *                That cap could have been breaking down under load. You
> could have bad connections. I would look at ALL of the connections very
> closely. Maybe, it saw you Armed with the proper service info and you
> scared it into working ;) I am really glad that you are on the air. If, it
> fails again, shake the service manual at it and give it a good cursing. 
> You
> may need to scare it some more.. Just Joking...*
> *                                                    73 de Wade/KJ4WS*
>
> On Sat, Jul 14, 2012 at 12:43 PM, Ben Hall <kd5byb at kd5byb.net> wrote:
>
>> Morning all,
>>
>> An update.  So I got the power amp out of the Paragon, took it all
>> apart, and inspected it.  I found no obvious damage - no swollen caps,
>> no burn marks, etc...
>>
>> I did remove C25 (which was a 33uF, 35V, 105 deg C unit) and couldn't
>> find a replacement in my supply.  C25 tested fine.  I ran it up to
>> nearly 30 VDC and it did not short, did not leak, etc...
>>
>> But I could find nothing wrong, so I put it back together minus C25.
>> With just the power amp on the bench, I hooked up 13.8VDC to the red 
>> lead.
>>
>> Everything was fine.  No power draw.  (insert head scratching here)
>>
>> So I put it back into the radio, hook up the RF output.  Apply power.
>> No power draw on the red wire into the power amp.
>>
>> So I reattached the blue "11" plug and repeat.  No power draw.
>>
>> So I reattached the RF Input and repeat.  No power draw.
>>
>> So at this point, everything is hooked up minus the red power wire.  So
>> I resolder it to the power board and apply power to the radio.
>>
>> It POWERS UP FINE.  Hooked it up to the dummy load, hooked up my mic,
>> and it makes output power just fine.  Voice peaks into the dummy load
>> easily hit nearly 100W.
>>
>> SoooOOOOooo!  I am now totally confused as to what's going on.  Best I
>> can figure was maybe a loose connection from the bias board to the power
>> amp?  VERY ODD.
>>
>> I am ordering some replacement caps from Mouser - will replace that 33uF
>> and the 10uF ones with 50VDC, 105 deg C replacements...
>>
>> thanks much and 73,
>> ben, kd5byb
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