Hi Bob,
I think you've hit the nail on the head! When I got this set, it had
been idle for several years. I inherited from my father-in-law when he
passed on and he had bought it used from the original owner. Many of
the front panel pots had the same problem - until I gave them some
rotation, they didn't want to make contact or were very scratchy.
FWIW, I did open the set with my can of DeOxIt at the ready, but the
pots appeared to be sealed, so I never did use any of it on them.
For the most part, I've not been on the air much this Summer. Standard
excuses - yard, work, family. So the Paragon had been idle for maybe a
month.
The discussion on telco troubleshooting is very interesting. Several
years ago I was following the design of a multicoupler than used relays
to switch the RF. The designer had designed it such that there was
about 3mA or so of DC current across the contacts when closed. This
kept them clean. I think he called it "wetting current."
When I was taking the PA module apart, I did think to myself "better not
bump the bias pots". But I'm sure that even being careful, I probably
did jostle them a little bit.
When the new caps come in and I take it apart to replace them, I will
use some DeOxIt on the bias pots and reset them.
Anyone have the adjustment procedure handy?
I have the little bottle with the needle applicator, so a tiny amount
will not be difficult. I'll admit, once of the things I hated about the
spray can was that it tended to go EVERYWHERE. :(
Thanks much to all for the great help and encouragement!
thanks much and 73,
ben, kd5byb
On 7/14/2012 9:23 PM, Bob McGraw - K4TAX wrote:
> 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
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>
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