On Jun 15, 12:48*pm, Todd wrote:
On Jun 15, 12:28*am, "N_Cook" wrote:



Todd wrote in message

....
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 Tenma came thru with a schematic :-) Looks like I have a open 820uh
inductor that explans the low voltage on the one side. Now to try and
find one.

Thanks again for the help

Todd

+++++

You have to find why the inductor failed, maybe has a secondary function as
a fuse.

Ok I guess I should check the current on the 2 transistors to make
sure they are close to the same then? One of the inductors has a
resistor across it for some reason, is this to prevent a oscilattion
like on my vacuum tube rf amp?

Todd

I was given a Tek 453 some years ago with this problem. It turned out
to be as a previous poster suggested one of the X drive transistors. I
wonder if you have a similar problem that may have caused the choke to
open as well. Lenny