One thing to note about calibrating the sg503. If you are going for the
best accuracy you will need the special cable.
In general use this is not critical but it can have a 1 to 2% effect on the
pk to pk output. So for dial accuracy this is a just be aware of it. Using
a non special cable will not effect flatness which is good.
The special cable is 50 ohms 1% if I remember the spec correctly
Eric
On Fri, Feb 23, 2024, 12:52 PM Adam R. Maxwell via groups.io <amaxwell=
[email protected]> wrote:
On Fri, Feb 23, 2024 at 07:12 AM, Frank Mashockie wrote:
I'd still be curious to know what voltages are typical at the -22V and
5.2V
rails for this SG503 powered via a TM5000 (not TM500). Because I am
still
measuring ~4.7V at the 5.2V rail even with it working. If anyone would
be
willing to measure that and share with the group, I would appreciate it!
Could save someone else from going down the same rabbit hole that I did
(if in
fact this is normal).
Curious whether you scoped your 5.2V rail and checked the voltage drop
across
R624? My 5.2V test point is at 5.2V until things warm up for a minute or
two, and
then starts wandering from 4.7-4.9 or so on my DMMs. The scope shows a
square
wave on the 5V test point that I think is due to the current limiter
kicking in, but
which the DMM averages out.
When the voltage drop across R624 goes below 0.6V, I'm back up to 5.2V. My
plan now is to replace the hottest ICs on the board and see if I can get
the current
down closer to the level Albert Otten reported, as I can't find any shorts
or bad
transistors.
Mine currently has no oscillator output unless I replace Q300 with a 2k
pot, per
the Wizard Workshop suggestion, so I'm afraid I've killed Q190 or U225. I
soldered
the grounded stud on the back of Q190 to the wrong point, so that's my
next stop.
Congrats on fixing your SG503. This is the plugin from hell as far as I'm
concerned.
Adam
