[GreenKeys] Schematic needed for Dovetron MPC1000T II

[John Spigel]

Thanks for all the responses. I've been able to look through the offered 
references and can see that there is quite an evolution for the Dovetron 
T. And amen to Jim. I can easily believe no two are alike with much 
disagreement between schematics, drawings and instruction manuals. I'm 
beginning to believe the engineers involved must have been one 
frustrated crew. The unit I have is missing much of what is described in 
the E Instruction manual, Including a Duplex/half duplex switch with no 
wires, missing pots for adjusting fsk audio tone keyer frequencies etc. 
Board components with values not on schematics, no auto start, etc. I 
haven't been able to get some functions to work yet such as the signal 
loss indicator or some of the built in self testing functions assuming 
they are really there. The loop LED flashes but very dimly. Will there 
be afsk audio output resulting from an RS232 level polar input?

However! I was able to trace an audio input signal problem to a bad 600 
ohm transformer. Removing from the circuit and replacing temporarily 
with a .1ufd cap immediately brought the unit to life! I am able to 
adjust the SSD cross display and see that the two polar outputs do 
respond to the audio input driven from MMTTY. That's enough success for 
today! Tomorrow I expect parts for a HAL ST-6000 that looks like a winner.
73, John W1AN

On 07-Feb-24 21:56, Jim Haynes wrote:
> I've never seen two Dovetron sets that are alike.
>
> Whenever I hear of someone having a Dovetron I send the following note
>
> The note is:  If you have the Binary Bit Processor BBP-100 Mark II as 
> shown on drawing 75349 then inspect the bottom side of the PC board to 
> see if there is an extraneous trace connecting the top ends of R21 and 
> R22. By top ends I mean the ends that are on top if you hold the 
> drawing vertically so it reads right side up.  The bottom ends are 
> supposed to be connected together and to pin 6 of U11. The top ends 
> are not supposed to be connected together.  If they are the threshold 
> voltage will stay at
> 0 volts so the threshold correction circuit is inoperative.  Cut the
> extraneous trace.  You can verify by looking at the schematic that those
> two resistor ends are not supposed to be connected together.
>
> Then look at resistors R24 and R25.  These are supposed to be 10K
> resistors.  You may find they are 100K, because 1% resistors have
> an extra digit in the value.  If the colors are brown-black-black-orange
> you have 100K resistors and the unit will hardly work at all after the
> extraneous PC trace is cut.  Replace with 10K resistors, and they
> probably don't need to be 1%.
>
>
>     ---
>
>     "Ya can argue all ya wanna, but it's dif'rent than it was."
>     "No it ain't! No it ain't!  But ya gotta know the territory."
>         Meredith Willson, The Music Man