30 Nov
2005
30 Nov
'05
6:31 p.m.
Hi
I looked at the schematic and the parts you'd indicated.
It looks like one of them was one off and was R55 and not
D11. From the looks, it might be that you have other failures
in the supply. You've indicated R11, R21 and R55. These
are all part of the circuit that drives the primary switcher
transistor through T3.
You might check D11 to make sure it isn't shorted. You
might want to run the supply separately to check outputs.
A short in T3 to the mains would also cause a lot of troubles
and burn these resistors( taking may other part with it ).
Other parts to look at would be:
Q2, Q3, Q4, E5 and D4
These are parts that could also be involved.
It does look like there is something other than the
resistors blown in the supply.
Dwight
30 Nov
30 Nov
7 p.m.
Okay, I'm sure that will help. I'm going to sit down and try to figure this
thing out after spending some time with this book. Again, this isn't a
hobby-crippling problem, as I'm using my VT220 right now in the VT100's
stead.
Actually, this is more a cleanup and cosmetic thing than anything else right
now - I really don't like having nonworking equipment lying around unless
the useful parts have been stripped out and put away and the excess thrown
away, and also, the VT100 looks so much better with my vintage setup than
the VT220.
I'll get back to you guys on this in a day or so. Thanks for everyone's
help so far!
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Dwight K. Elvey
Sent: Wednesday, November 30, 2005 8:32 PM
To: cctalk at classiccmp.org
Subject: Re: More parts I need to replace on the VT100
Hi
I looked at the schematic and the parts you'd indicated.
It looks like one of them was one off and was R55 and not
D11. From the looks, it might be that you have other failures
in the supply. You've indicated R11, R21 and R55. These
are all part of the circuit that drives the primary switcher
transistor through T3.
You might check D11 to make sure it isn't shorted. You
might want to run the supply separately to check outputs.
A short in T3 to the mains would also cause a lot of troubles
and burn these resistors( taking may other part with it ).
Other parts to look at would be:
Q2, Q3, Q4, E5 and D4
These are parts that could also be involved.
It does look like there is something other than the
resistors blown in the supply.
Dwight
1 Dec
1 Dec
3:04 p.m.
Hi
I looked at the schematic and the parts you'd indicated.
It looks like one of them was one off and was R55 and not
D11. From the looks, it might be that you have other failures
in the supply. You've indicated R11, R21 and R55. These
are all part of the circuit that drives the primary switcher
transistor through T3.
Having looked at the printset, the first thing that struck me is that
these are all high power resistors (2 or 3 watt rating). They would
naturally run hot, therefore, and may look discoloured without there
being anything wrong with them.
Before we dive into this PSU, I would be interested to know if the thing
produces any output voltage, and if those 3 resistors test bad on an
ohmmeter.
-tony
6742
days inactive
6742
days old
2 comments
3 participants
participants (3)
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