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Re: Power Can Not Be Turned On

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  • karla_803
    Thanks John. Last November I tried the int/ext configuration and external long wire with no apparent differences in speaker hisses (AM - light, intermittent
    Message 1 of 11 , Mar 2, 2013
      Thanks John. Last November I tried the int/ext configuration and external long wire with no apparent differences in speaker hisses (AM - light, intermittent hiss; FM - heavy, fine hiss; LW - similar to AM; SW - light, periodic hiss; no LED light up). Interferences from, eg., house light switches were picked up weakly on AM. The radio also responded weakly to a 27MHz radio control unit placed close by; the working DX-440 had a much, much better response.

      Anyway, after one or two further attempts early this year a decision was taken to cease troubleshooting the 803A and it was junked.

      The DX-440 PSU jack was accidently knocked out last night and the radio would not switch on. The LCD showed garbage, something like "301C" - which looked familiar! The AA batteries were removed and it was left overnight. A replacement PSU was used and it would still not switch on, giving more LCD garbage. The batteries were removed for 2-3 minutes and replaced - and this time it switched on OK. The normal PSU jack cover was re-screwed on tightly and it now powers the DX-440 again.

      --- In Sangean803@yahoogroups.com, JOHN NORTH <johnpnorth@...> wrote:
      >
      > Correction...The RF GAIN does work with the INT Antenna SW on...I needed to put
      > my hand on the telescopic antenna!
      > John
      >
      >
      >
      >
      > ________________________________
      > From: karla_803 <donlavelle@...>
      > To: Sangean803@yahoogroups.com
      > Sent: Fri, November 23, 2012 1:06:21 AM
      > Subject: [Sangean803] Re: Power Can Not Be Turned On
      >
      >  
      > Still trying to fix the '803A from time to time. I compared voltages with the
      > '440 during a couple of troubleshooting sessions but found nothing obvious to
      > me. Even though the voltages of both Q110s were similar I strongly suspected a
      > blown front end and purchased a substitute FET (2N5485 from Littlediode Ltd UK)
      > and installed it. No luck - but at least the symptoms haven't got worse.
      >
      >
      > (This thread should probably be re-titled, because the power is now available
      > but no stations can now be heard).
      >
      > --- In Sangean803@yahoogroups.com, "karla_803" <donlavelle@> wrote:
      > >
      > > Thanks ws8e, I've checked the power switch itself many times (many many times)
      > >and circuits nearby. Lately I thought that Q205-7 from the block diagram is a
      > >form of transistorised switching circuit and checked that against my working
      > >DX-440. No luck. Also retried PCB B voltages (especially Q307-9) on both radios.
      > >No Joy. I've also tried many other ideas/inspirations and illogical checks
      > >without any success - even put the radio in deep freeze overnight to, maybe,
      > >unscramble IC402.
      > >
      > > Anyway the radio is now back in one piece - and - the power switch circuit is
      > >currently working! However the speaker just gives the charactistic hiss of
      > >different wavebands but no stations. At least I'm a little better off than
      > >before.
      > >
      > > I'll put the radio away for a spell and maybe look at it again but, in the
      > >meantime I'll use the DX-440.
      > >
      > > Thanks to everyone for trying to help me with this.
      > >
      > >
      > > --- In Sangean803@yahoogroups.com, WS8E <de.ws8e@> wrote:
      > > >
      > > > Karla - I think the "power switch circuit" is the on/off switch and maybe
      > > > electrically near by circuitry.
      > > >
      > > >
      > > >
      > > > On Sun, Sep 9, 2012 at 10:41 AM, karla_803 <donlavelle@>wrote:
      > > >
      > > > > **
      > > > >
      > > > >
      > > > > Thanks John. The Lock Switch has been checked over a couple of times with
      > > > > multimeter. PCB-B has been checked kunder a magnifying glass. Indications
      > > > > are that this board is the culprit but I'm still trying to track it down.
      > I
      > > > > still don't understand what the Power Switch Circuit is exactly. I guess
      > it
      > > > > is Q208-9 Regulator circuit on PCB-B. Or is it the Q205-7 Part of the
      > > > > circuit. Why is called Power Switch Circuit in the Service Manual?
      > > > >
      > > > > Anyway, latest checks include: power jack plug connections, S201as above,
      > > > > and 3v trace from L7, B2 to R208.
      > > > >
      > > > > A test was carried out at a time when the radio appeared to be working.
      > > > > 2xAA batteries were inserted and the 9vDC PSU was plugged and unplugged
      > > > > until I got a hiss from the speaker ie. the radio was activated to an
      > > > > extent. Service Manual fault finding was followed for "Power Can Not Be
      > > > > Turned On" and IC402 pin 15 was reading 2.75v - call it 3v, Q203 collector
      > > > > was 0.13v - less than 0.2v, Q305 collector was 7.5v - let's say 8v [I'm
      > not
      > > > > sure of the accuracy of my multimeter]. These results indicated all was
      > > > > well. These readings were not given when the speaker did not hiss.
      > > > >
      > > > > I'm studying the block diagram of the circuit at present and am homing in
      > > > > on PCB-B and will test out voltages from power jack socket onwards [but
      > > > > must check out the multimeter calibration first].
      > > > >
      > > > > > On'.
      > > > >
      > > > > --- In Sangean803@yahoogroups.com, JOHN NORTH <johnpnorth@> wrote:
      > > > > >
      > > > > > Hi Karla,
      > > > > > I assume you verified the LOCK switch is turned OFF? I would look very
      > > > > closely
      > > > > > at the 9 vdc JACK soldered on the circiut board. These radios are
      > > > > notorious for
      > > > > > broken solder joints on the circuit board. That's what I found once when
      > > > > the
      > > > > > radio fell over. Power circuit is on the PCB that the 9dvc jack lives
      > on.
      > > > > > Good Luck
      > > > > > John
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > > ________________________________
      > > > > > From: karla_803 <donlavelle@>
      > > > >
      > > > > > To: Sangean803@yahoogroups.com
      > > > > > Sent: Thu, September 6, 2012 12:46:17 PM
      > > > > > Subject: [Sangean803] Power Can Not Be Turned On
      > > > > >
      > > > > > Â
      > > > > > My set failed when the external 9vDC power jackplug was knocked
      > > > > sideways;
      > > > > > internal 2xAA in use.
      > > > > >
      > > > > > The power plug was repaired but the radio failed to start.
      > > > > >
      > > > > > Used another 9vDC PSU; the radio still failed to start.
      > > > > >
      > > > > > Checked power jack socket.
      > > > > >
      > > > > > Checked input voltages.
      > > > > >
      > > > > > After visual examination, multiform wire K3 was soldered back in circuit
      > > > > but the
      > > > > > radio failed to start.
      > > > > >
      > > > > > Have no D cells so clipped external 9vDC input to battery contacts.
      > > > > >
      > > > > > Checked power switch contacts.
      > > > > >
      > > > > > Obtained Sangean ATS 803A Service Manual from http://www.mods.dk/
      > > > > >
      > > > > > Started to follow Troubleshooting Flowchart Section 3: 'Power Can Not Be
      > > > > Turned
      > > > > > On'.
      > > > > >
      > > > > > Removed PCBs B, A1 and A2 for access to PCB-C.
      > > > > >
      > > > > > With 9vDC PSU on, checked pin 15 of IC402 = no voltage. Couldn't access
      > > > > pin 58;
      > > > > > pins 5 and 8 had resistors in the way. Difficult PCB for access.
      > > > > >
      > > > > > Random tinker with grey multiform wires to see if any loose connections.
      > > > > >
      > > > > > Radio working.
      > > > > >
      > > > > > Next day - radio failed to start again.
      > > > > >
      > > > > > Tried reset of IC402 by removing batteries and shorting 3v battery
      > > > > terminals;
      > > > > > radio failed to start.
      > > > > >
      > > > > > Checked integrity of multiform wires A, B, E, F, J and especially G-2.
      > > > > >
      > > > > > Removed and replaced multiform wires for power switch, J and K. Radio
      > > > > worked
      > > > > > then failed after switch off, pause and switch on. Sometimes the radio
      > > > > would
      > > > > > almost start. Once the display was correct, tuning appeared to be
      > > > > working but
      > > > > > there was only hiss from the speaker and no reception - even with BFO.
      > > > > >
      > > > > > Checked voltages of Q207, 8, 9 with analogue multimeter = voltages at
      > > > > > approximately half value on emitters and bases with collector voltages
      > > > > appearing
      > > > > > about right.
      > > > > >
      > > > > > Obtained Realistic DX-440 Service Manual from this site (thanks).
      > > > > >
      > > > > > The failure appears to be related to the upD7503G-701 / A65 processor:
      > > > > > The clock works with 2x AA batteries. Clock stays on when 9vDC PSU
      > > > > plugged in
      > > > > > but clock display fades slowly when PSU is switched on. Switching the
      > > > > power
      > > > > > button sometimes activates the electronics and generates a hiss noise in
      > > > > the
      > > > > > speaker. The LCD display light always works. However, the radio won't
      > > > > work
      > > > > > properly - the display sometimes has broken segments in the display or
      > > > > is partly
      > > > > > correct or, once, showed "IC30C" which may have been an low-level fault
      > > > > message
      > > > > > for IC301. Very occasionally the clock stays on when the PSU is switched
      > > > > on and
      > > > > > the radio works - in fact it has done this three times in over 50 tries.
      > > > > >
      > > > > > The Service Manuals advise "check the power switch circuit" - but I am
      > > > > unsure
      > > > > > where this is.
      > > > > >
      > > > > > In the meantime, I'll try opening it all up again and follow message
      > > > > #1652 for
      > > > > > an alternative IC reset method. I will update when I've done this and
      > > > > anything
      > > > > > else.
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > > [Non-text portions of this message have been removed]
      > > > > >
      > > > >
      > > > >
      > > > >
      > > >
      > > >
      > > > [Non-text portions of this message have been removed]
      > > >
      > >
      >
      >
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      >
      > [Non-text portions of this message have been removed]
      >
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