[DSP-10] EZ Lite CPU Replacement

[Paul Breed]

I use a weller pyro pen with the hot air tip.
About $100.00, but it makes SMT real easy.

I believe it is even better than an expensive SMT air gun.
A SMT hot air gun blows air, the pyro pen blows oxygen depleted air.

For real high quality reword i've seen hot air guns hooked to dry
nitrogen bottles, so the solder does not oxidize, the pyro pen does that
automatically.

Using the pyro pen, some solder paste, tweezers and a jewelers magnifying visor
I've done a lot of SMT removal and replacement.

Paul (Kl7JG)


At 05:55 PM 8/25/02 -0500, you wrote:
>Jess,
>
>Good job on replacing that guy, it always helps to have reasonably good
>tools for the job.  When needed at work I can change out 208 pin flatpacks
>but I have stereo microscope and a small tip weller iron.  I have seen
>various techniques used at work -any way that does lift pads or many of
>them- is good!  You don't need an IR station for removal of these kinds of
>parts.  One of the techs in manufacturing would use a utility knife (!) and
>score/shear-cut the leads off the body of the 208 pin chip without lifting
>pads, Pete was good.  After he lifted the body out he would slip his hot iron
>under the pin's (waiting for the solder to reflow) and lift the pins out.  He
>could change out one of these 208 flatpacks under 15 minuets.    Again,
>the whole idea here is not to lift pads and damage the board, even if you
>have to add a jumper - it's no big deal.  I seen more boards come back from
>the field due to unsolded/unflowed pins (board assembly vendor problems)
>than board rework, duplicating field problems on return boards sometimes is
>a different story...  I hope my ramblings will give others encourangement to
>do smt.  ;-)
>
>73's es Cul
>
>dave garnier - wb9own
>
>
>W4mvb@cs.com wrote:
>
> > Good Evening To the Group,
> >
> > Thanks to the info from the users manual that Paul, HB9OMQ sent to me 
> and to
> > the advice and encouragement I received from Dave, WB9OWN, I was able to
> > diagnose and replace the failed CPU in my original EZ Lite unit.
> >
> > I have about half the parts necessary to build another unit.  The LMX1501AM
> > is no longer available from Digi Key.  Is there sub for this part or 
> another
> > source perhaps?
> >
> > Since 432 is included in the software as a possible transverter is anyone
> > using (planning to use) a DSP-10 for that purpose?  If so, what frequency
> > conversion scheme is anticipated (or used)?  It seems to me that the 
> obvious
> > harmonically related 144/288/432  scheme would be a no-no.
> >
> > One more question if I may?  I have used the 90 mhz oscillator circuit from
> > the no tune transverter designs for several units and I have always 
> bought my
> > crystals from Down East Microwave since they use the same oscillator 
> circuit
> > in their transverters.  I went to the DEM website last week looking for a
> > 93.6667 mhz crystal for an AO-40 L Band transmit converter and was 
> surprised
> > to find that DEM has apparently replaced all their 90 mhz crystals with 180
> > mhz units.  Has there been a circuit for these crystals published anywhere?
> > I would guess that the basic circuit is the same but with some changed 
> values
> > for components in the oscillator circuit.
> >
> > Thanks for all the help.
> >
> > 73 de Jess - W4MVB
> >
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