[Boatanchors] Johnson Invader 2000 Help Needed

[Mark Bell]

Hi Al --

Well, what really tics me is that I have +300V handwritten on the line above
R104, which leads right to R88, and missed it.   Grrrrr.

Thanks for the resistance check;  at least now I won't be unsoldering the
large voltage divider caps to segment the 300V circuit.    I'm not sure if
R61 was the problem, or an effect.

Mark K3M SB


----- Original Message ----- 
From: "Al Parker" <anchor at ec.rr.com>
To: "Mark Bell" <bell at blazenet.net>; "Boatanchors List"
<boatanchors at mailman.qth.net>
Sent: Monday, May 16, 2005 9:33 AM
Subject: Re: [Boatanchors] Johnson Invader 2000 Help Needed


> HI Mark,
>     Sorry to hear that you let the smoke out.
>     I first looked at the skem, as that was the easiest, and see one path
> to gnd thru R88, an 82k res. at the relay amp tube, V-5B.  So that's half
> of what you're seeing.  I then finally got into mine & I measure 38.9k
> from V-7 pin 5 to gnd, ~same as you do.
>     So, it looks like you don't have a problem in the exciter chassis, at
> least not there.
>     Let me know when you get yours on the air, maybe we can get 2 talking
> to each other.  I haven't used mine for several months, and was initially
> startled when I opened the lid and it was warm in the 0A2 area - the
> heater resistor on the VFO chassis had been keeping things warm thru the
> Winter, I still had the 240vac plugged in.  The Invader 2000 shares a
> 240vac outlet with the URT-23B, so I guess that's been idle longer than
> the INV2000.
> 73,
> Al, W8UT
> New Bern, NC
> BoatAnchors appreciated here
> http://www.thecompendium.net/radio/
> http://www.hammarlund.info
>
> ----- Original Message ----- 
> From: "Mark Bell" <bell at blazenet.net>
> To: "Boatanchors List" <boatanchors at mailman.qth.net>
> Sent: Monday, May 16, 2005 12:15 AM
> Subject: [Boatanchors] Johnson Invader 2000 Help Needed
>
>
> > Gang --
> >
> > Bad news -- Initial smoke test of my Invader produced.....smoke!
> >
> > I popped the fuse on the LV Power Chassis and had some smoke coming from
> the
> > compartment housing R61 on the Invader.   R61 look cracked, but not
> burned,
> > and I replaced it.  The sniff test indicated this was not the culprit,
> but
> > it ohmed out at 33 ohms, not the 1K it was supposed to be.
> >
> > The 300V line on the LV supply was blown, and I tracked it down to the
> > 5U4 -- it tested dead on both sides.  I performed voltage check on the
> LV
> > supply before installing another tube, and all was OK.  After the new
> 5u4
> > was installed, all voltages from the LV chassis was good (high, but I
> didn't
> > have a load on it).
> >
> > I then proceeded to do the resistance checks as per the manual.  Every
> > measurement associated with the 300 / 150V circuit was really high.   By
> > removing the 0A2, I was able to check the 150V circuit and the dropping
> > resistors associated with it are good.
> >
> > My problem is the 300V circuit.  With the 0A2 out of the circuit, and
> all
> > cables removed from the Invader chassis,  I should see essentially
> infinite
> > resistance between the 300V supply of the LV cable connector (J3 pin 5)
> and
> > ground.   I'm measuring about 33K ohms.  I get about 39K from 0A2 pin 5
> > (with the OA2 removed); again, I expect to see almost an open.
> >
> > I need some help in understanding what could be causing this in order to
> > know what to look for.
> >
> > I think there are a few Invader 2K owners on the group;  if so, can you
> do a
> > check on the 0A2 pin 5 and let me know what you getting?
> >
> > Thanks
> >
> > Mark K3MSB
> >
> >
>
>
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