[DSP-10] Re: heat problem? More data

Tue, 20 Aug 2002 00:08:09 -0000

Thanks for reading my plea!
Here is some data you asked for.   I am posting the reply to the list
as some one else may see the problem.

1.  The DC voltages (suggested)
U101-1       13.8v,  all regulator outputs were fine.
U14-2/13    6.84v (
U1-3          3.47v
U2-3          4.83v
R110         1.69v
U105-3       2.66v
U106-3       3.84v
R59            1.36v
U8              2.56v
U9              3.38v
Q106-1        9.74v
U10-3          4.5v
U109-6         2.4v

2. The RF board is in the box with the regulators attached to the box.
The box on the outside of the regulators gets very slightly warmer -
not much at all.  Touching the tabs on the inside - same thing -
hardly warm

3. The EZkit is mounted in its copper box.  The copper box cover is
off and the copper box is lying beside the bud box.  There is a ground
between the copper box and the bud box.  The bud box cover is also
off.

4. While receiving:
    The RF board and the EZkit lite together draw 550ma at 13.8v.
    The RF board alone (EZKit unplugged) draws 291 ma at 13.8v

5. Any frequency.  In fact, I can sort of hear the sound on the
speaker change (although in no so loudly) even with the dsp program
NOT loaded.

Additionally, I looked at the waveform of the audio on an
oscilloscope.  It looks like a few cycles at low amplitude and a
pulse, few cycles, pulse, and the pattern repeats regularly.

Thanks,
- -
Rajiv Dewan, N2RD
-----------------------
I regret that I do not accept any e-mail from:
 yahoo.com, msn.com, hotmail.com, lycos.com and excite.com
 because of excessive spam mail from these domains.
---------------------------

----- Original Message -----
From: "David Garnier" <[email protected]>
To: <[email protected]>
Sent: Monday, August 19, 2002 4:20 AM
Subject: Re: [DSP-10] heat problem?

> Rajiv,
>
> Congrads on getting as far as you have considering all things.
>
> I need to know a few more things before I start suggesting
> things.
>
> 1) What were your measured voltages and how did they compare
> to the suggested voltages?
>
> 2) Do you have the RF board mounted in the bud box with the
> regulators mounted to the box floor?  What is the temp of the
> regulators on the otherside of the box?
>
> 3) Is you a/d evaluation board mounted in it's copper box
> and installed above the RF board?
>
> 4) Can you make some current measurements?  Idraw on the
> dsp10 board receiving, (with and without measuring the a/d
> evaluation board?  Is that clear?
>
> 5) At what freq does the noisefloor go up?
>
> dave garnier - wb9own
>
> "Rajiv Dewan, N2RD" wrote:
>
> > I just finished assembling the DSP-10 unit.  It is in its box with
the
> > DSP unit in its box lying beside the dsp-10 box.  I have finished
the
> > serial and PLL tuning and that went fine.  I get a lock from 143
to
> > 148.2 and I am happy with that.
> >
> > As I listen with my unit, I note that when I start it from cold
with a
> > 50ohm resistor at anenna input, the noise floor is often better
> > than -144dbm.  This however, begins to deteriorate in short order,
at
> > the rate of about a db a minute till the unit ends up at -133dbm
with
> > lots of audible noise from the speaker.  This is when I feed the
unit
> > with 13.8V.  Even with 11v input, the noise floor does begin to
> > deteriorate, albeit at a slower rate.  A fan helps but does not
solve
> > the problem.  I felt around and the hottest components are those
> > around U8 and U9.  They are hot to touch but not uncomfortably so.
My
> > guess is that they are around 110 to 120F.
> >
> > Looking at the waterfal display (with brightness 65 and contrast
15),
> > it starts out with just a few dots every 5kcs, and soon it forms a
> > series of lines every five kc's or so.  The lines get thicker as
time
> > passes, and in about 4 to 6 minutes, the lines all merge into
solid
> > color.  I am attaching a jpeg image of the waterfall display.
> > It might be stripped by the list.  If you send me an email, I will
> > mail you a copy.
> >
> > As an aside, I noted that the unit is 8.8kcs too high.  I am using
the
> > TAPR supplied Epson crystal, and I haven't padded it with 10pf
> > capacitors yet.  I want to deal with the noise floor issue first.
> >
> > Any help appreciated.
> >
> > - -
> > Rajiv Dewan, N2RD
> > -----------------------
> > I regret that I do not accept any e-mail from:
> >  yahoo.com, msn.com, hotmail.com, lycos.com and excite.com
> >  because of excessive spam mail from these domains.
> > ---------------------------
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