[AMRadio] Suggestions for restoring a DX-100
john_walker_beasley
jbeasley at earthlink.net
Wed Apr 3 20:46:53 EST 2002
Thanks everyone !
One more question.
What is an acceptable amount of leakage ? Less than 1ma?
What latency should I expect, for example, less than 1ma after
5 minutes under voltage ?
I know these questions are stupid to someone who is
knowledgeable with the procedure. I'd rather sound stupid than
flame this rig !
Thank You
John, WAØSTX
----- Original Message -----
From: "George Pritchard" <gpritchard at comtechpst.com>
To: <amradio at mailman.qth.net>
Sent: Wednesday, April 03, 2002 2:16 PM
Subject: RE: [AMRadio] Suggestions for restoring a DX-100
> Reforming caps, or verifying leakage on them is easy if you have one of
> those older 0-400 VDC high voltage variable supplies (heathkits $10 at
> fests). I used it to verify leakage on "New Old Stock" caps and noticed
very
> high leakage, >10 mA at only 100 Volts! I'd leave them at 100 volts until
> leakage dropped to < 1 mA... then go up slowly to 200 volts, and wait
again.
> Repeat the process untill you get to 400 volts on the 450 volt rated caps
> with less than 1 mA current. I did this for the replacement caps on my
> DX-100. Guess what... They only lasted two weeks and shorted again anyway!
I
> ended up with big oil types mounted where the HV 5U4s used to be before I
> solid-stated the supply. The oils will never fail. BTW... I used the
> Heathkit supply to verify the shorted capacitors in the first place. It
> saves fuses and possible the transformer!!! Good luck.
> George AB2KC
>
> -----Original Message-----
> From: amradio-admin at mailman.qth.net
> [mailto:amradio-admin at mailman.qth.net]On Behalf Of Bill Smith
> Sent: Wednesday, April 03, 2002 2:52 PM
> To: amradio at mailman.qth.net
> Subject: Re: [AMRadio] Suggestions for restoring a DX-100
>
>
> Don't turn it on and expect the electrolytics to survive the shock. Bring
> up line voltage slowly with a variac, or light-bulbs in series with the
> power line.
>
> Start with about 60 volts. Just enough to light the filaments in the
> rectifier and feed voltage into the power supply. Ramp it up slowly from
> there, over the next several minutes. It should begin to operate at about
> 90 volts. Play it at 110 volts for a while (ten or so minutes) before
> giving it the full gas, watching for trouble.
>
> If you go through this simple procedure, you may recover all the
> electrolytics. If you don't, you'll be sure to replace at least one can.
> Look at the circuit to see how B+ is switched, and see if there is some
way
> to reform any cans that are switched on only during transmit.
>
> Unfortunately, there is no recourse to tubular paper caps, they become
leaky
> over time and will likely need replacement. They may seem "ok" when you
> first use the equipment, but will quickly degrade with use.
>
> 73 de Bill, AB6MT
> billsmith at ispwest.com
>
>
> ----- Original Message -----
> From: "russ dworakowski" <wb3fau at hotmail.com>
> To: <amradio at mailman.qth.net>
> Sent: Wednesday, April 03, 2002 11:35 AM
> Subject: Re: [AMRadio] Suggestions for restoring a DX-100
>
>
> > John, what to do with your DX-100 has a lot to do with how it has
> been
> > stored. Transformers are not a common problem in the DX 100 as
they
> > are the potted type and less subject to moisture damage.
> > Replacement of power supply electrolytiics is most common problem.
> > These rigs sit around not in use for long periods causes the
> > capacitors to go bad. There are a few in the audio section to
check
> as
> > well. Good luck and have fun! Russ
> >
> >
> > >From: "john_walker_beasley" <jbeasley at earthlink.net>
> > >Reply-To: amradio at mailman.qth.net
> > >To: "AM Radio Reflector" <amradio at mailman.qth.net>
> > >Subject: [AMRadio] Suggestions for restoring a DX-100
> > >Date: Sun, 24 Mar 2002 11:43:38 -0600
> > >
> > >Gentlemen:
> > >
> > > I have a DX-100 and I am looking for any tips or advice
> > >before I begin working on it. It is in good cosmetic condition
> > >and the quality of the soldering looks good.
> > >
> > > I am familiar with the replacement of electrolytics, however,
> > >my expertise with aging components pretty much stops here.
> > >
> > > What I am mostly concerned about is trying to avoid the
> > >problems some people talk of such as losing mod transformers
> > >from the failure of other aging components.
> > >
> > > What precautions should I be taking? What other components
> > >should be scrutinized. ?
> > >
> > > Any suggestions or links that may be good reading on this
> > >topic ?
> > >
> > > Thank You
> > >
> > > --... ...--
> > > John WAØSTX
> > >
> > >
> > >
> > >
> > >
> > >
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