Re: Tek 310 and Looking for Advice


Stan & Patricia Griffiths <w7ni@...>
 

OK Stan,

I have inserted some more comments below:

----- Original Message -----
From: "stan mcintosh" <mcintosh@triad.rr.com>
To: "Stan & Patricia Griffiths" <w7ni@easystreet.com>; "TekScopes"
<TekScopes@yahoogroups.com>; <morriso@vifm.org>
Sent: Tuesday, November 04, 2003 6:11 PM
Subject: Re: [TekScopes] Tek 310 and Looking for Advice


I have one more in a box, but I decided that an 83.5 volt drop
tube would work for checking out a few of the other items.
***That's probably close enough to make it work . . . I have a bunch of
5651's if we need one that's closer.

Are the power supplies "regulating"? That is, do the voltages remain
the
same as the line voltage is varied from 105 to 125 VAC? If you don't
have
a
metered variable line voltage source, now is the time to get one.
Here is where we see some differentiation. From 105-125VAC input: the
+100
V regulates right at 59V, the -150 regulates at -139, and the +300 swings
from 270 to 290. I don't have a metered line voltage source, but I do
have
a voltmeter for making such measurements when using a Variac input.
***A Variac with an outboard meter attached is good enough. You can vary
the line voltage and you know about how much it is. That's all you need.

How much "ripple" is on each supply? Is is about the amount stated in
the
manual calibration procedure? (10 millivolts)
The ripple values in the +300, +100, and -150 are 3 mV, 1 mV, and 3 mV,
respectively.
***Wow! That's pretty low ripple but the lower the better. It seems a
little strange to me that you could have such low ripple on the +300 supply
and it still varies from 270 to 290 when you vary the line voltage from 105
to 125 VAC . . .

As you try to set the -150 volt power supply on -150, can you vary it at
all
with the adjustment control or is it just at -140 all the time?
The adjustment does affect the -150 output voltage.
***But apparently you can't bring it up (or down) to -150. The next thing I
would check are the precision resistors on both ends of the -150 adjustment
pot. This would be R609 (56.5K) and R611 (68K). These need to be close to
those values. You should also check R669 (1meg) and R670 (490K) in the +300
supply for 1% accuracy and they need to be right on.

Bear in mind that the -150 and +300 supplies depend on each other and they
must both work for either one of them to work. Concentrate your efforts on
these two supplies and make them both work before you look anywhere else for
other problems. The +100 will not work unless both the -150 and +300 are
working but the +100 does not need to work for the -150 or +300 to work.

I'm going to have a cold one and pore over the power supply schematic,
again. However, I'm hoping that you'll effortlessly say, "Ah-Ha! You
obviously failed to check ..."

Again, thanks for all of the help. If this scope didn't have so much
character, and if I didn't really want it to be part of my bench, I'd go
back to working on my superhet.

Sincerely,
stan
***Well, Stan, the 310 and 310A are both gems in my opinion and well worth
the trouble to make them work.

Stan
w7ni@easystreet.com

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