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G8MNY  > TECH     01.12.18 09:00l 277 Lines 12107 Bytes #2 (0) @ WW
BID : 47396_GB7CIP
Subj: Autocaller with old Maplin kit
Sent: 181201/0752Z @:GB7CIP.#32.GBR.EURO #:47396 [Caterham Surrey GBR]

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By G8MNY                               (Updated Mar 17)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I had built a few of these Digital Record & Playback Modules kits from 1989 for
Contest calling, ATV repeater announcements & Commercial Radio use. So when saw
a new unbuilt kit at a junk sale I snapped it up. This new build came 2nd in a
construction contest.

Although with my IC735 HF rig there is a rear Aux socket with +13.8V, that has
all of the wanted signals, I use that for Demo station AF PA connection, so I
did not want use it here. I managed to used just the mic plug connection, the
max rating of the 8V @ 1A peak, incuding the radio! I found I had some
sensitive DIL package 12V 1K coil DIL reed changeover relays worked OK on 8V!
(but not all of them!)

旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴커
           /Repeat\ rep /Mess\                  IC735              
(Play)     Delay  쿗ED Time 납                                    
           \On Off/     \    /                                     
(Mem )  run        level       쳐캑PTT                               
        LED  ____  LED         쳐캑LS                                
            /MIC \             쳐캑+8V                               
(Rec )     쿞ocket      (H/P) 쳐캑0V                                
읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸
   Controls & Connection layout 

It consists of an Electret Mic, 2 dual op-amps LF442 IC1 & 2, a dedicated A-D-A
sound 40pin IC3 UM5100, logic IC4 74HC133, 256K memory Ram 62256 IC5, & 5V reg.
IC3 has clock output that is used to make -ve rail for the opamps. For fixed 
work, the ram can be an eprom, a seperate add on kit is an eprom programmer
(plugs into SK1) & banks of eproms can be use together for multi messaging etc.

P1 P2 P7 P8 P10 P12 P11 Mem Links
旼컴컴컴컴컴컴컴컴컴컴컴컴컴커    P1 Electret Mic
' '   '  '  '  '  '| | | 旼엿    P3 AF Output
     LED    旼컴컴| | |  납    P10 Play
쿝V1 TR1  TR2 IC4 넬컴컴엿 납    P11 Record
            읕컴컴冒    납S납    P5 +8-14V in
    旼컴컴컴컴컴컴엿    납K납    P7 +5V out
넬커    A-D-A     납RAM 납1납    P2,4,5,6,9,12 0V
납    SOUND IC3  납IC5 납 납                           旼LED
냅켸 읕컴컴컴컴컴컴冒    납 납    Gain IC1   ___  Data  TR1   ___
 IC1           RV2     납 납  Mic컨캑>캑>캑A>D쳐컴컴컴컨컴캑RAM
                   읕컴켸 납              쿔C3  Address   쿘EM
 旼풦C2        _旼쩡퓊eg  납   AF컴<쳐<쳐퀮<D쳐컴컴컴쩡컴캑IC5
             - 쿚     납         IC2     퀂top 旼좔커 읕컴
 읕. .   . .  ~읕좔    읕冒  play--------큀sc쳐TR2캑gate 旼컴
읕컴컴컴컴컴컴컴컴컴컴컴컴컴켸  rec---------읕쩡     읕컴켸 퀁eg
    P3 P4 P6 P5                             Speed      IC4   읕컴

The op-amps are used with the A-D-A input/output to generate the data, filter &
replay it. It is fairly flat 300Hz-3kHz with up to 40dB S/N, @ 10 seconds
message time. Up to 23 sec is usable, but quality is much reduced. For external
mic/AF use, I removed the mic's DC feed.

1/ Message time.
I extended the clock frequency preset RV2 to the front panel, to enable long or
short messages, & also variable speed on recorded items like CW.

2/ Status LEDs
I also extended the level LED & added a "4 Pulse" LED from a high order count
address line A12 on the programmer socket. This gives a simple end of message

          //  0V

With the later repeat toggle latch (/7), I also added a "Repeat On" LED too.

3/ Battery backup.
To store the message on power off a battery backup is needed to power just the
Ram to > 2.4V. Cut the 5V track feeding the Ram & add..

            __ 3x
Ram 28컴    __ 100mAH
             __ Nicads

4/ Second message Ram.
I piggy backed on a 2nd message Ram. I soldered the first directly into the
PCB with the Chip Select pin 20 track cut, & added a socket on top for the 2nd
ram, also with CS pin isolated. I use a locking push switch to select the RAM.

        100K  100K               雹賽賽
    Ram1        Ram2           賽賽賽-20
     20컴캑    쳐컴20       =====추賽賽======
          픬  o             cut PCB to pin 20
       mem1 \  mem2     
Battery Save \_________   By add this NPN the power off batt back-
    Earth   e/쿻pn          up current is reduced from mA to uA!

5/ Record Rx.
This uses a non locking double pole changeover push button, to trigger record
mode with a one shot C & a change over from mic to Rx LS record, when record
button is held in.

Ham MIC>컴컴컴컴컴쩡컴컴컴컴컴>Rig
                  o             Mic
AF in____________/REC
Module            o    旼100K<Rx LS
(mic DC)             Rx
(removed)         읕>Level
Rec     One shot  o    
(pulse)  10n    o    

6/ Mon LS.
I added an old LM386 360mW amp & 8R LS as monitor. But used an AF diode gate in
front of it to mute LS, unless it was playing or recording off the Rx LS line.

===22u    100K    AF   100K    
               Gate       3\6
Play AF>캑쳐좔>쳐쩡<쳐좔캑쳐퀽M\  5         +220u FB _/
         u1              u1  386'>컴컴컴컴쩡컴늘컴早  쿘on
Rx               100K      旼캑  /8컴10u  ===u1     渼_ 쿗S
Rec >컴컴컴<쳐컴캑         2/ 1 ===               \
                            4 픭ot+    10R       
Relay >컴컴<쳐컴켸       컨컴컨컴컴컴컴컴컴좔컴컴컴컨컴0v
Play                        Pot 47K= preset Mon Vol

7/ Repeat timer.
I was going to use a 555 timer. But close investigation I saw an easy solution,
just an NPN & zener with a CR in front of it. Although this worked well, I soon
realised a toggle flip flop bistable was needed too, for ease of operation.

                Repeat On off with Delay control (a switched vol control pot)
Repeat__    \_/             旼<Play button (earth)
 ON  =\ /     쳐컨캑>쳐)컴컴컴쩝컴컴컴컴>Module Play (CMOS logic)
 LED  컫                   
               旼>쳐)컴컴컴)>Mic PTT stop  _
      1K            10K                     /|
                    쳐캑<쳐)컴컴컴컴컫1M Delay커
       쳐100K캑  쳐22K캑                Control  
              \/             \          /              mic relay
     T1 \_____/\____/ T2   T3 쳐>쳐컫좔컴컴>쳐컨33K컴<+8V on Rx
       e/           \e      e/ 5V' +                    0V on play
          Flip Flop                ===22u
      On  = repeat =  Off             Repeat Delay CR

The 33K sets the min delay to about 1 second Rx, & +1M to >60 seconds. Turning
the delay timer on (or rig power up), turns on T2 via u1. This ensures the 22u
can't charge up.

Pressing the Play button fires the module to play & also turn off T2 that flips
the toggle. T1 now on, lights the Repeat LED. T2 off lets 22u charge up when
the play has finished, from the 8V via the Mic relay coil. When > 5V, T3 is
turned on initiating another play.

Pressing the Mic PTT puts a good earth via diode to T1's base turning it off, &
flipping the toggle into not repeat mode. So does the intial power on pulse via
u1 & diode with C charging 100K R.

This was not straight forward! The kit does not have an ON PLAY line, so I
detected the fastest run clock A0 on S15 to generate a PTT line.

mic AF>컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴훟
                      bead   10n         \컴컴>Rig mic
      Module Play AF>컴RFC컫컴늘47k컴컴o mic
                               preset    relay
         Headphone relay<컴 play level

mic PTT>컴쩡컴캑<쳐컴컴컴컴컴컴컴컴컴컴컴컴컴커
Kill                      +8V                
Run <캑>쳐             ________             
(TR2 Base 10k)         쿺ic relay            
(Fed via diode)        읕컴컫컴컴    o Play  
                            쳐컴컴쩡컴o<컴컴컴좔컴컴컴>Rig PTT
WE Ram27컴컴<쳐               __  Push held
0V record pulses               /_\  in stops Tx
A0 Run        +          \e     
clock      4u7===                

As I did not want the PTT or mic relay (mic powered from rig) operated on
record I used the 0V Write Enable pulses to discharge the 4u7 to defeat the

B/ Headphones.
The last op-amp IC2 is just powerful enough to give playback headphone level
with cap changed & a NFB gain pot added, to the last unit gain amp. So I added
another reed relay changeover for the headphone feed.

                      旼>Mic playback gain
Headphone_ o컴컴컴컴컴좔훀FC컴<Playback Module AF (modified louder Op-amp cct)
     Relay\o            bead
           읕150컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴<Rig LS
To Rec<컴컴컴>Rec level      ________
Button        47K pot       쿓/P relay
                         u1    쳐컴컴쩡컴> LS amp mute
                          === /     __
S15컴컴컴컴컴47K컴)컴컴컴컴컨컴퀯C182 /_\
Run pulse                     \e     
The 150R in the headphone feed is selected to give suitable level from the
rig's LS line.

With all these mods the unit is quite complex, but I managed it with just 1
additional vero PCB & loads of coloured wiring, CAD documenting it as I went.

One thing I did miss was tefect of the LS magnet on the nearby reed relays,
once the lid was on! A tin can cover glued/soldered over the magnet was needed!

There are several pots in the system, a bit of a round ribbon to get right
straight away, some need to be set first, before the others are adjusted.

1/ Set the original mic in gain RV1, to "just distort" if shouting into the mic
   (Level LED flashes brightly).
2/ Set added Playout gain level on IC2, to give adequate headphone level.
3/ Set Playout level mic feeding preset to give same Tx level as the live mic.
4/ Re check 1 2 & 3 for best results.
5/ Set Rx LS vol to typical level on a Rx signal. Set Rx Rec pot for same
   flashing LED level as with mic record.
6/ Set Mon LS play level to a comfortable background check level.

In use the controls make it very easy to use. With headphones on you can hear
the Rx, pre-recorded messages, Tx or not depending on keeping the play button
pressed. A stab of the record button, records the mic for the 4 LED flashes, or
keeping the button pressed, it records the Rx AF, were the rig Volume control
setting the level all heard in the headphones.

Without the headphones you just hear playouts on the LS. but not when recording
the mic. Pressing the mic PTT kills the player & the repeat toggle.
Recordings should be made with little/no AGC action & "repeat" set to OFF!
Replay of Rx recordings come over best if the rig's mic processing is "OFF"!

See my other tech bul on "PA instability in ICOM IC735" & "IC 735 No RF Output

Why Don' U send an interesting bul?

73 De John, G8MNY @ GB7CIP

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