On Jun 14, 12:31*am, "N_Cook" wrote:
Todd wrote in message

...

Anyone have a source for a service manual for a Tenma 72-905 O'scope?
I have one that the horizontal trace stays on the left side of the
tube only. Figure it's a problem with the sweep circuit. Anyone seen
this?

Todd

With the power off check cold, initially, for differences between the 2
final X-drive transistors, usually long-tail paired.

Ok messed with it today some. DC wise one of the transistors has a cap
that slowly charges with the ohm meter hooked up..
Checked the 2 power resistors on each curcuit and they measured ok.

With power turned on on of the transistors will vary its voltage
between 171 and 36 with the horz pos knob.
The other one will only change between 18.7 and 20.4 volts.
pulled the transistor that was no varying much and checked it with a
ohm meter it looks good.

Is there a generic schmetic I could look at to see how this curcuit
should work?

thanks for the help.

Todd