I the three Tek 453 scopes. Two are MOD703K, one is 703H.
I find the docs that show some differences, along with changes.
In the family, I find these variants
453 SN < 20,000
453 SN 20,000+ Major change seems to be nuVistors are changed out for FET's
453 MOD703H (see below)
453 MOD703K (see below)
453-A Larger CTR, 60 mHZ
453-A Later SN, many changes
453A-1 Uncalibrated delay of the delayed sweep
453A-2 Calibrated delay time
435A-3 Calibrated sweep delay and mixed sweep
454A-4 Single time base
453A-5 No documentation found, X-Y mode
The 453 MOD703K seems to have more in common with the 453A-5. They share most of the same boards, larger CRT.
The docs I have show MOD703K includes:
1. SAWTOOTH OUT facility has been added to the rear panel via BNC connector.
2. CH 1 OUT connector has been moved on the front panel, Amplitude is 200 mV for each division of CH 1 deflection,
3. A GATE and B GATE facilities have been added to the rear panel,
4, The Calibrator Current Loop has been added to the front Panel, and the 1 V CAL connector has been moved
5. A TRACE FINDER control has been added to the front panel.
6. The HORIZ DISPLAY switch has an added position providing XY.
7. The light on the RESET control has been deleted.
8. TRIGGERING (DELAYED SWEEP); COUPLING and SOURCE functions, have been added including an EXT TRIG INPUT or EXT HORIZ connector,
9. Special accessories in lieu of standard are provided, See parts list.
Mod 703H includes:
1. A SAWTOOTH OUT facility is added with its BNC connector mounted on the side panel.
2. Amplitude of CH 1 OUT signal is increased to 200 mV for each division of vertical deflection.
3. The CRT is replaced with a CRT having a special internal rise~time graticule.
4. Two. probe tip adapters, two banana plug tips, and a 13.5" BNC to BNC 50 Ohm coaxial cable are added to the standard accessories.
I have compiled a type study showing the board part number designations that were used in all the variants, compiled from docs and compared to the ones I own. The doc I find for changes to the 703H and 703K shows changes for 703H after serial number 60777. They do not agree with the one I have that is 60794. The board numbers listed for the 703K agree with what I find in the two scopes I have. The 703H has a couple of boards that have 703H silk-screened on them, and there is a small daughter board (670-704-00) attached to the A Sweep board, missing on the 703K's
