Re: TM500 Plug-in Extention

Chuck Harris

There is some discussion in the FG504 manual that suggests
that many TM50X frames were built with one of the power
transformer windings out of proper phase for the FG504 to
work well.

I would guess that the windings, being AC were just a pair
of unmarked wires, and the assemblers didn't know that they
needed to pay attention to which wires went to which pad.

It wouldn't be a problem most of the time, but in some of
the many possible configurations it could result in issues.

Perhaps now?

-Chuck Harris

Harvey White wrote:

interleaved responses

On 8/10/2020 4:13 PM, Stephen wrote:
I figured that the plugins that were not working before but are now were the ones
needing the NPN transistor.
The PS503 probably needs the PNP only.
Actually, looking at the TM503A manual gives you an idea of the reason.  The outputs
of the supplies go through the frame transistors.  However the drivers for those
transistors also provide a path for the regulated output.  It's a very "weak" current
limited output, which would show up with a good meter, but the supply would not
provide anything near full current.  The 5 volts uses a 7805 regulator, hence the 1
amp current limit.

Now that all my plugins are powering on, I have to figure out 2 things.  Not that
the 1st is a real issue, but I’m just trying to understand the concept.

1- While the unit is inside the 506, and when my DMM ground lead is connected to
ANY of the ground banana plugs can I measure the +/- 20VDC as well as the 5VDC. 
But when the plugin is connected To the extender, I have to switch the ground lead
to the appropriate one on the PS to be able to read the voltages
The DC503A 5 volt ground is common to all modules.  The common lead for the +/-
supply is floating.  I'd measure from the frame to frame of the power supply to see
what's going on there. However, a possible suggestion is to look on the backplane to
see if there any added wires.

2- I still don’t get why the DC503 shows only 1 digit or nothing at all when
plugged in directly into the 506, but is showing every single one, albeit some are
missing a segment, when used with the extender...  A mystery to me.  But I’ll
follow up on this in the appropriate thread I started on troubleshooting it.
I'd suggest backplane wiring, as in there shouldn't be any.  If someone used this
with backplane wiring, then the slots become dedicated to a particular module.  You
didn't connect the additional wires to bring out the plugin signals, where in the
frame, they're connected.


Join to automatically receive all group messages.