Todd wrote in message
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On Jun 16, 12:13 am, "N_Cook" wrote:
Todd wrote in message

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On Jun 15, 12:28 am, "N_Cook" wrote:





Todd wrote in message

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On Jun 14, 12:31 am, "N_Cook" wrote:

Todd wrote in message


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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

+++++

It was often a fudge/kludge to use a resistor as a former for winding the
coil on ,and nothing electrical in purpose- Hide quoted text -

- Show quoted text -

Ok will be a few days till I get back to it. Still not sure why there
is inductors there. Just for a temp repair I replaced with a jumper
and everything seemed to operate correctly then. Need to find a
replacement for the inductor Tenma doesn't have them any longer.

Todd

+++++


scrape off the lacquer/coating to inspect why it failed mainly. If you
cannot find a replacement, count turns and rewind it yourself