Alec,
Finally got around to making some preliminary measurements on my
Paragon's heat sink temperature. The following data was taken
from my Paragon 585 running key down as noted with no cooling
fan. As you can see the sink heats up rather quickly at 100%
duty cycle - 8 minutes to go from room temp (25 deg C) to +70 deg C
(160 deg F). At this point (t=+8 minutes), I switched to a 50% duty
cycle (1 minute TX/1minute Rx), and the temperature stabilized at
~69 deg C. Tx collector current was maintained around 20 amps which
corresponds to ~90 watts RF output. Cool down appears to be rather
slow (10 minutes = 25 deg C), but am sure that a small cooling fan
would improve things drastically. I should note that I had to manually
back off the RF drive to keep the Paragon's internal 25 amp fuse from
blowing, as the collector current tends to increase significantly with
device temperature.
Do you have a transistor data sheet for the MRF458? I was wondering
what the thermal resistance (junction-to-case) and Tjmax is for this
device. BTW, you appear to be correct that this transistor is no longer
in production - I couldn't find it on the Motorola website.
Cheers,
Mike, W4EF..................
Elapsed Heat Sink
Time Temperature
(min) (deg F) (Deg C)
0:00 77.6 25.33 Ic=20 amps
0:01 83.8 28.78 Ic=20 amps Had to backoff drive to
maintain constant Ic
0:02 95.9 35.50 Ic=20 amps " "
0:03 109.1 42.83 Ic=20 amps " "
0:04 120.8 49.33 Ic=20 amps Ic starting to stabilize
0:05 131.8 55.44 Ic=20 amps
0:06 141.2 60.67 Ic=20 amps
0:07 150.2 65.67 Ic=21 amps Same drive setting
0:08 157.8 69.89
0:08 160.4 71.33 Turned Off Tx
0:09 156.8 69.33 Tx On
0:10 156.8 69.33 Tx Off
0:11 155.2 68.44 Tx On
0:12 156.2 69.00 Tx Off
0:13 155.7 68.72 Tx Off
0:14 149.8 65.44 Tx Off
0:15 143.7 62.06 Tx Off
0:16 138.5 59.17 Tx Off
0:17 133.4 56.33 Tx Off
0:18 130.8 54.89 Tx Off
0:19 126.8 52.67 Tx Off
0:20 123.6 50.89 Tx Off
0:21 120.6 49.22 Tx Off
0:23 115.6 46.44 Tx Off
0:25 110.9 43.83 Tx Off
----------
From: promedia[SMTP:promedia@itnet.com.pl]
Sent: Monday, January 04, 1999 10:09 AM
To: Michael Tope; tentec@contesting.com
Subject: [TenTec] Paragon
Mike,
you are great !! Thanks for the message and suggestions.
Well, the fact is, I 'm somewhat fed up with all that.
I have a full bag of blown transistors and, just after
the last failure, I've encountered really big problems
with buying the replacements as Motorola stopped
producing them... I had enough,
especially that ten-tec's help cost me really much
and left in nothingness...
Probably, the bias problem means there's no
thermal compensation, as the protecting diodes
are located in the midair actually.
When using even the minimum power,
with processor on (SSB) or RTTY,
the heatsink temperature goes so high
one couldn't believe to happen with a properly
designed module. Probably, also, that is
the moment the bias protection fails.
Implementing, under such circumstances,
a heatsink with horizontal fins,
without a fan,
tell me it's rethoric, calls for someone
to be sent back to primary school lessons in phisics.
Anyway, despite the fact I operated
the paragon with my hand on the heatsink
thus controlling the temperature, I wasn't
able to avoid the next transistor set
failure as well as a tremendous impact
on my budget which followed....
Since I'm running my rig barefoot,
as it's common in this part of the world,
factory shouldn't be surprised I want to
get every watt out of it.
Implementing the FSK possibility with
this particular design seems really odd...
As in my case, it means implementing
instantaneous PA damage facility...
Could you, please, tell me,
how does the PA behaves in your case
regarding its temperatures, etc ?
All the happiness to you all
for the New Year....
Alec/SP2EWQ
Michael Tope wrote:
> Hi Alec,
>
> Sorry I have taken so long to reply, but I have thousands
> of messages in my inbox here. Interesting problem with
> your PA - I have a Paragon here which I have operated on and off
> but relatively trouble free for about 7 years. The only problem
> I had with the PA was a blown electrolytic capacitor - it went
> off like a shotgun one evening while I was tuning up. Scared
> the hell out of me. At first, I thought my downstairs neighbor was
> retaliating for the loud music from my stereo - grin grin.
> When I opened up the PA module, I found pieces of electrolytic
> strewn all over the inside of the PA module. I promptly removed the
> debris and replaced the blown cap with one from my junkbox. The PA
> has worked trouble free since that time, including a little contest
> duty and RTTY at 100 watts.
>
> Sounds like fundamentally you have a bias problem. Have you checked
> the bias circuit in the PA against the schematic? Assuming your
> circuit
> and mine are similar, I suspect a bad component(s) as opposed to a
> flawed design. Have you made the bias current adjustment (this is a
> very simple procedure)? Worst case, have you considered buying a
> new PA module.
>
> Don't rule out operator error either. About two years ago, I was
> cursing
> my Paragon to high heaven and was ready to leave it for the garbage
> man.
> The microprocessor kept locking up or getting into weird states where
> the
> QSK wouldn't work properly when running split frequency. I almost took
>
> a sledge hammer to it during the 96 SS CW. After several calls to
> Ten-Tec
> and countless hours inside the microprocessor section adding bypass
> caps
> and chokes, I came to my senses and measured the input voltage under
> trasmit
> conditions. Turns out that I was losing 2 volts across a resistive
> fuse
> holder. When I replaced the fuse holder, everything started working
> perfectly. Lesson learned - don't always look for the complicated
> solution
> first!
>
> As a final note, I would suggest for your own sake to keep the
> inflammatory
> rhetoric to a minimum. People don't respond well to that sort of
> thing, and
> its usually counterproductive when it comes to solving technical
> problems. As I
> learned from my faulty fuse holder experience, all the cussing and
> swearing
> in the world didn't make my radio work properly - only careful and
> deliberate
> troubleshooting.
>
> Good Luck,
>
> Mike, W4EF......
>
> ----------
> From: promedia[SMTP:promedia@itnet.com.pl]
> Sent: Tuesday, December 08, 1998 12:20 PM
> To: Michael Tope
> Subject: Re: [TenTec] on ten-tec's primitivy...
>
> Hi Michael,
>
> thanks.
> I'm just abt starting believing it's more my problem
> than paragon's. Everybody's so happy...
>
> Since the beginning paragon delivered no more than 50W
> output. I wouldn't care much abt it if it only stayed that way.
> But, there must be something really fishy. I've got already
> a full bag of burnt PA transistors which are extremely difficult
> to buy here.
>
> The module was sent to ten-tec for the repairs. They kept it
> for ages there, and sent back in the same condition.
> As not to reach bancrupcy, I had to detach the PA.
>
> There were other failures in the meantime too, but I could cope
> with them myself somehow. I think, PA is areally badly designed module
>
> there and using radiator with horizontally placed ribs shows
> a kind of ignorance in basic phisics. Especially, they don't install
> any
>
> fans with it.
>
> When it worked, I used to operate with one hand on PA radiator
> and even that way I couldn't prevent the transistors from damage.
>
> I gave up, Michael.
> I thought I was buying something America's Best.
> I really did.
>
> Yours,
>
> Alec/SP2EWQ
>
> Michael Tope wrote:
>
> > Alex,
> >
> > I have only casually following this thread. I am having
> > a hard time understanding exactly what is wrong with
> > your Paragon. I am correct that you have a problem with
> > the RF module? Is this low output power, intermittent
> > operation?
> >
> > Just curious, I am also a Paragon owner.
> >
> > 73 de Mike, W4EF.......
> >
> > ----------
> > From: promedia[SMTP:promedia@itnet.com.pl]
> > Sent: Monday, December 07, 1998 10:07 AM
> > To: pcuellar@bright.net
> > Cc: 'seweber@netnitco.net'; tentec@contesting.com
> > Subject: [TenTec] on ten-tec's primitivy...
> >
> > <<File: ATT00001.html>>
> > Hi to all, and you Phil,
> >
> > Well, it seemed to me what I bought it WAS a proffessional Radio.
> > I paid, at least, for such.
> > I didn't want and don't want anything for free. Some of you are
> > heavenly
> > praising the fact
> > you were given anything. Maybe there must be some Alexes first for
> > some
> > Bills, Phils
> > and similar to exist later.
> >
> > What I certainly found I am talking colours to some who are
> completely
> >
> > blind.
> > You should well accept the fact, that what you get for a
> proffesional
> > money is a kind
> > of an amateurish device. Designed in that manner and manufactured
> in
> > that mannner.
> > It's primitivity is shown right from the front panel, through that
> > what's inside, to the last screw
> > supposed to keep the speaker in place, instead protruding from upper
>
> > cover and getting
> > in direct conflict with the rear panel.
> > If you cannot see well enough use a magnifying glass. And accept the
>
> > fact.
> >
> > The problem simplicity or primitivity doesn't mean a good
> operational
> > quality in this case.
> > It's simple for you there, to send the rig for repairs, and get it
> > free.
> > And I understand why.
> > For such a factory as ten-tec is simpler not to charge a customer
> for
> > the repair
> > because he or she might ask some "trivial" questions afterwards. One
>
> > who's not blind might find out
> > it was factory to blame for that what'd happened. Some might even
> get
> > a
> > bit angry....
> >
> > Since I had enough of that ten-tec's proffesional beating around
> > bushes,
> > when I asked them
> > for help, I've decided to maintain paragon's usefulness myself
> > spending
> > a lot on modifications.
> > Accept the fact, too.
> >
> > Ten-tec must first knuckle well over their designing desks to
> produce
> > something up to present
> > standards. It's going to take some time, however.
> > I wonder if they can at all having such a "good" support on the
> > rubbish they are
> > filling their boxes with now.
> > Besides, Primitivity must take its origin from somewhere, too. In
> this
> >
> > case it's not so difficult
> > to point the source.
> >
> > Anybody who's considering buying ten-tec's must expect and be
> prepared
> >
> > for
> > a lot contacts with ten-tec afterward his "pride and joy" will have
> > arrived.
> > Best you could move closer to a post office.
> > Some will fruit with something free (shipping excluded).
> > Remember Alec then, your sponsor...
> >
> > Yours, as always,
> >
> > Alec/SP2EWQ
> >
> > Phil Cuellar wrote:
> >
> > > >
> > > > > {snip} Besides.
> > > >
> > > > >I'm not happy with the results.
> > > >
> > > > >With some rig really being working properly, I would have
> > > >
> > > > >doubled the final score, AT LEAST.
> > > >
> > > > >See you all..
> > > >
> > > > >Stay happy, but still, remember, think twice,
> > > >
> > > > >before you start reading ten-tec commercials.
> > > >
> > > > >Learn from the mistakes committed by others.
> > > >
> > > > >It's a part of a universal wisdom, guys...
> > > >
> > > > >>Alec/SP2EWQ
> > > >
> > > Considering his score and his feelings that he should have been
> able
> >
> > > to at
> > > least double it, maybe Alec needs a PROFESSIONAL radio, he is
> > > obviously too
> > > "good" an operator to use a radio designed well enough for us
> lowly
> > > bumbling AMATEURS! I wish him luck in his search for a better
> radio.
> >
> > >
> > > 73 de KB8TRK - Phil
> > >
> > > --
> > > FAQ on WWW: http://www.contesting.com/tentecfaq.htm
> > > Submissions: tentec@contesting.com
> > > Administrative requests: tentec-REQUEST@contesting.com
> > > Problems: owner-tentec@contesting.com
> > > Search:
> http://www.contesting.com/km9p/search.htm
--
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Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
Search: http://www.contesting.com/km9p/search.htm
--
FAQ on WWW: http://www.contesting.com/tentecfaq.htm
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
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