Help me repair Iwatsu SS-7821 200Mhz OSC

[chihaxinh]

Hi everybody

I have one Iwatsu SS-7821 OSC , similar SS-7804/06/10/11A Iwatsu OSC Series. One day when i using X-Y mode, Osc hang and i restart OSC . Boot hang and display only trigger led .

You can see service manual in link below
http://www.iti.iwatsu.co.jp/manual/pdf/SS-7810-05-04_ServManl.pdf

Ok, when have time i open OSC and checking .
- No display - Only have dot when press button Beam Find .
- All button front panel hang ( display only Trigger led )


Like troubleshot osc, i checking Horizon Amplifier and find out dont have ramp signal . And i follow in service manual , all signal grenarator Ramp control by TLC IC ( IC made by Iwatsu)

Sawtooth Buff

H&Z SW

Timming


I goto TCL module and check Crystal , it's ok , i have 19.9999Mhz clock



And some day thinking , and review OSC block . i go to check around CPU , and checking Serial Data because all block like timming, sawtooth, h&z sw , h output amp have controll by DA ( Analog Board 8bit D/A) . And i find out missing Serial Clock and Serial Data go to D/A board.

ANA Board Control


ANA 8Bit


I checking TLC and ANA Board Controll connect to one sub board ( only have in 7821 ) and i dont have schematics . Sub board connecting to TLC IC and have Print label ( Trig Sub G-K3653 D2). I see sub board have 3 IC logic . 2x 10HL131 (Dual D Type Master-Slave Flip-Flop), 1x 10HL107 (Triple 2-Input Exclusive OR) .

I think module it's frequency counter or frequency divider . and some transistor SOT-23 layout like Pushpull amplifier ( High requency transistor ).
I takeout all transistor and smd diode and checking, trans and smd diode dont broken or fail . It's OK.
I checking by multimeter have VCC and GND around 600R , and i takeout 3 IC logic and checking VCC-GND IC logic , it's ok .
I go back to subboard without IC and all transistor and diode ,and have same result , resistor between VCC-GND around 600R.



I dont know why missing Serial Data and Clock Data to ANA Ctr and ANA D/A 8bit . I replay IC IC6 74W32 in ANA board Control dont give back clock.

And i have one question, Serial clock and Data clock have 0.2V/div it's normanly ? Do you think CPU have problem ?

Many thank so much!
Nam Nguyen Hai