[1000mp] Mark V turn-on, power-up issue

[Phil Mills]

Perhaps the rig lights up but the display is dead......

Try using the rig from a computer connection.

I have some personal experience from this  perspective
in that I thought I had a dead unit but it was probably
only the hv unit powering the  display...there is a separate
hv unit for the front display..

good luck, 73,
Phil
W5BVB


----- Original Message ----- 
From: "Glenn Rattmann" <k6na at cts.com>
To: <1000mp at mailman.qth.net>
Sent: Monday, February 16, 2009 3:21 PM
Subject: [1000mp] Mark V turn-on, power-up issue


> List,
>
> I've had an intermittent turn-on issue with one of my Mark V 200-Watt
> radios, where it won't light up at all.  I have two rigs and two
> FP-29 (and two cables), so I have definitely isolated the problem to
> the one radio.  The radio also more than once has just gone black
> unexpectedly while in use, and won't restart when this happens.  If
> it sits cold for a week or two, it might come back up normally, only
> to fail again later.  Lots of wiggling around with the DC cable/FP-29
> hasn't fixed it.  I searched the 1000mp archives for FP-29 or other
> power-up issues and didn't see anything exactly like this.
>
> I've got this radio spread all over the bench now.  The DC cable
> comes to the rear apron and meets a Molex-type bulkhead mount 6-pin
> connector there.  I've removed the connector from the rear
> apron.  The six conductors in the harness go almost to the front of
> the radio, under the fan, where four of them curve back to the power
> input board accessible by removing the fan and the heatsink/amplifier
> module.  The other two conductors (light gauge) terminate in a little
> connector mounted to a bracket near the power-on switch, but
> interestingly there is no mate to that connector-- it's just floating 
> there.
>
> The four other wires terminate on the DC power board in lugs bolted
> to the board.  The board has a few capacitors and a couple of relays,
> and the heavy output wires then lead from the board into the RF power
> amp module.
>
> I'm thinking of replacing the relays on the board as a shot in the
> dark.  Or, the intermittent may be caused by either poorly crimped
> lugs on the high current leads (at least one looks insufficiently
> crimped, but it's a guess), OR poorly mated pins inside the
> Molex-type connector (I assume it is not a true USA Molex-- it's not 
> marked).
>
> Before putting the radio back together, I will improve the crimping
> on all the DC lugs, and add solder to them so I can rule out this as
> a possible problem source.
>
> Second, I want to pull the pins out of the DC connector, examine the
> pin-crimping, and perhaps solder them, too.  I know Molex has a
> series of pin-removal/install tools for their various connectors, but
> has anyone identified the correct tool for this particular Molex-like
> connector?  FYI the pins are not round, they are hollow square, or
> perhaps rectangular, in section.  I want to obtain the tool if
> possible (have not started a search with vendors yet, because the
> connector mfr. is unknown).
>
> I will also go into the amp module to inspect how the DC voltage
> leads terminate in there, and inspect everything.
>
> When this radio lights up, it works perfectly in all respects,
> usually for hours at a time, so I don't really suspect the amp-output
> devices-- but I am open-minded.
>
> By the way, I know of two people who after difficult troubleshooting
> did eventually learn that they suffered from improperly crimped pins
> in the Molex connectors of the power supply leads in their kw RF
> amplifiers (the connector between the removable power transformer and
> the amp wiring harness).  This led to intermittent filament
> voltage.  So, these types of connectors are not always perfect, and
> if intermittent, can be a bear to discover and fix!
>
> Any ideas on this issue are appreciated... thanks!
>
> --Glenn K6NA
>
>
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