I'll second Bob's comments regarding pots going high (resistance) when not
exercised. My Corsair-II which is used nearly every day for logging (and
occasionally working) PSK-31 DX, requires its pots and switches to be
exercised or the received signals or power out will be way down.
When I worked in telephony, I learned rotary switches, pots, relays, plugs,
and other devices need their contact oxide buildup cleaned by wiping action.
Most of the CAME CLEAR WHILE TESTING or TROUBLE GOOD LEAVING HERE were
largely due to (jack and plug) contacts being cleaned as tests were
performed. As a result of those experiences, one of the first things I try
when my Ten-Tec radios appear to be malfunctioning is to exercise the knobs,
switches, controls, etc. to clear the problem. Most of the time its just a
pot or rotary switch in the older equipment or a plug or cable connection in
the OMNI-VII which uses mostly digital encoders.
73 ES DX,
Gary -- AB9M
-----Original Message-----
From: Bob McGraw - K4TAX
Sent: Saturday, July 14, 2012 9:23 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Paragon Problem gets very odd
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@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@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@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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>>
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