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Off topic Hitachi v-152B help?

VK4AU
 

Sorry but in my defense I do have a Tektronix 465B as well.
This Hitachi has had me puzzling for some time,
The necessary technical undersanding, and reading of the schemaics eludes me but I am sure many on this list can direct me to the right path.


Channel 2 seems ok.

Channel 1
No wave form appears at any setting.

Trace (flat-line) appears only at Volt/Div setting of 5V, 0.5V, 5mV.
No trace visible at other Volt/Div,
However :-
Sweep visible at other Volt/Div settings when time sweep is set at low speed, but only as a vertical diffuse band (off screen?) best viewed in low light.

Volts/Division Var/Calibrate control can move vertical position of the trace 7 graticules up/down.

Vertical Position control cannot move trace above the position set by the Volts/Division Var/Calibrate control

At Calibrate position of Cal/Var , and with Vertical Position control at max height, trace is ~ 2 graticules above bottom of screen.

Rotation of Cal/Var counter clockwise moves trace up, and can go off top of screen.

Vertical Position control can then move trace up to, but not above the position set by the Var/Cal control

This unit has no “beamfinder” and no “Invert” control.
Can do Add/Diff modes, these have slight effect on trace position.

Schematics can be found at:
https://sonsofinvention.wordpress.com/2013/02/14/hitachi-v-152f-oscilloscope-operation-manual/ https://sonsofinvention.wordpress.com/2013/02/14/hitachi-v-152f-oscilloscope-operation-manual/
Good quality colour scan

http://electronicsandbooks.com/eab1/manual/Hardware/H/Hitachi/004_Oscilloscopes/V-152F-Operation_Manual%20c20020829%20[30].pdf http://electronicsandbooks.com/eab1/manual/Hardware/H/Hitachi/004_Oscilloscopes/V-152F-Operation_Manual%20c20020829%20%5b30%5d.pdf
Less quality, horizontal section schematic unreadable.


These are for the V-152F while mine is V-152B, Mine does not have the chanel 1 output at rear unfortunately.


Hoping this means something to somebody??
Any advice gratefully accepted.


Thanks


Mark

 

The input circuit around TR2 was probably burnt out by an overload. It
is less likely but possible that IC1 (a 741 operational amplifier) is
bad or C26 is shorted.

The input buffer can be checked by measuring the voltage at the base
of TR3 which should be within millivolts of 0 volts compared to
ground.

The ghosting you see when the trace is not visible is because it is
being driven off of the visible screen. At some attenuation settings,
there is enough attenuation in the second attenuation stage to allow
it to be visible.

VK4AU
 

Thanks for the advice. Unfortunately the components in question are in the most in accessible spot, between the Volt/Div switch and PCB and jammed in under the CRT. I had to think about disassembling the whole thing for a while before I dared do it! C26 is fine?, I took it out and it reads 11.5uF (nominally 10uF) and ESR admittedly an a cheapo ESR meter of 0.04. TR3 base however reads -6.8V compared to ground. I have not as yet found a data sheet for TR2 E412S-A. I would appreciate any advice.
Thanks
Mark