[Premium-Rx] Watkins Johnson DRO-333 reprogramming

[Ray Robinson]

Hi John,

It has more than 6 digits displayed,
but I think it only loads offsets for 4 of the counters.
tens of mhz
units of mhz
hundreds of khz
tens of khz

The PCB tracks connect 4 columns of modules 
in parallel to 4 counter ICs.
There are 6 common tracks for the rows of modules.
These go off board and dissappear into cable looms.

The front panel switch has 3 positions,
and the rear switch has 2 positions,
so it selects a set of 3 I think.
I could be wrong.

I orginally thought they might be pull-up resistors,
but they measure like diodes.

73 
Ray vk2ilv

> 6 rows with 4 modules each, and it's a 4 digit display?
> The yes, your reasoning would be correct, there would
> be 6 possible offset selections.  Depending on the diode
> polarity, and the required sense of the preset inputs of
> the digital divider IC's, the common node of the diode
> module would be tied to Vcc or gnd to make that module
> active.  The diodes provide isolation, allowing a logic true
> to be applied to some preset inputs without it coupling
> to other inputs.
> 
> I used a somewhat similar scheme on the digital displays
> I used to sell.
> 
> John
> KK6IL
> 
> At 10:21 PM 3/4/2009, you wrote:
> 
> >Hi Gang,
> >
> >The early WJ and CEI receivers had analog tuning and analog dials.
> >A later option was a 19" rack mounted digital readout,
> >called the DRO-333.
> >It used the local oscillator of the receiver
> >then added the IF offset,
> >to give a digital readout of the received frequency.
> >These are fixed.
> >It works fine on my RS-111,
> >and gives accuarate readings from 30 mhz to 1000 mhz.
> >
> >I have looked at the counter board,
> >and there are 4 modules which look like large SIP resistors,
> >and each has 2 coloured dots on it,
> >like a resistor colour code.
> >They are arranged in 6 rows.
> >I therefore deduce that there are 6 offsets,
> >that preload the 4 counter ICs.
> >They are selected by the front panel switch,
> >and the rear toggle switch.
> >I have measured one module,
> >and it appears to be 4 diodes connected to a common,
> >and this is used to program the decimal counter.
> >
> >Does anyone know if this reasoning is correct?
> >or has anyone reprogrammed one before?
> >or does anyone have a circuit or manual.
> >
> >Regards
> >Ray vk22no
> >______________________________________________________________
> >Premium-Rx mailing list
> >Home: http://mailman.qth.net/mailman/listinfo/premium-rx
> >Help Page: http://mailman.qth.net/mmfaq.htm
> >Post: mailto:Premium-Rx at mailman.qth.net
> >Help Contact eMail:  paul at 8zo.com
> >Home Page:  http://www.premium-rx.org/
> >
> >
> >--
> >Internal Virus Database is out-of-date.
> >Checked by AVG.
> >Version: 7.5.552 / Virus Database: 270.11.3/1967 - Release Date: 
> >2/23/2009 7:17 AM
> >
> >
> >
> >
> >--
> >Internal Virus Database is out-of-date.
> >Checked by AVG.
> >Version: 7.5.552 / Virus Database: 270.11.3/1967 - Release Date: 
> >2/23/2009 7:17 AM
> 
> 
> 
> -- 
> Internal Virus Database is out-of-date.
> Checked by AVG. 
> Version: 7.5.552 / Virus Database: 270.11.3/1967 - Release Date: 2/23/2009 7:17 AM
> 
> 
>