Jim,

I would rate them as the best DMM test leads I have. They have a lot of nice screw on tip accessories too...won't fall off on you (looking at you Fluke). Definitely worth a look.

I'm also thinking of getting a pair of their passive oscilloscope probe kits for my 1727A storage 'scope.

Good company.

Sean

On Sun, Mar 29, 2020 at 05:29 PM, Jim Ford wrote:
Hey, if you can't seriously injure yourself by misusing them, they aren't sharp enough! Gotta be able to poke through those oxides, flux residue, etc. Not to mention high enough spatial resolution not to short out a bunch of pads at once.

I bet those are better than the Pomona Electronics ones I recommended, because of the silicone leads on the Probemaster ones. Thanks, Sean. Won't melt if you hit 'em with a soldering iron. Why no, I've never done that before; why do you ask? ;)

Jim Ford

On Apr 3, 2020, at 16:39, [email protected] wrote:

?Stephen,

1855-0082, TRANSISTOR:FIELD EFFECT P-CHANNEL

Sean

On Fri, Apr 3, 2020 at 04:28 PM, Stephen Hanselman wrote:

Seam,

?

Please send the p/n I’ll check stock

Regards,

?

Stephen Hanselman

Datagate Systems, LLC

?

?

?

?

If you need that FET, I can send you one...

Dan in Chandler, AZ

Well, to have an S parameter set, a TR set and an ISM band antenna range.

Do I really need all that? No. But what else am I going to do? Watch TV? Not something that appeals to me.

Have Fun!
Reg

Seam,

?

Please send the p/n I’ll check stock

Regards,

?

Stephen Hanselman

Datagate Systems, LLC

?

?

?

?

On Apr 3, 2020, at 13:53, [email protected] wrote:

?Hi Chuck,

Good point. So far it's stable. I aligned it as best I am able for now, and it's working in all modes with reasonable accuracy. If it becomes intermittent, looks like it is still possible to obtain these FETs, though it will probably cost.

Seam

On Fri, Apr 3, 2020 at 01:33 PM, Chuck Harris wrote:

Just a repair note:

I have seen a lot of TO92 packaged transistors where
one or more lead has become intermittent. I believe
this is caused by fiddle fingered folks that just have
to push the transistor around to match their ideal of
position, or to read the number.

It always seems to happen when the transistor is mounted
with the leads in a tripod position with the base lead
bent forwards, or backwards.

Touch, or otherwise move the transistor, and it quits...
touch it again, and it works.

-Chuck Harris

The "Preflight Checkout" diagram is clear about where things go, but it presents every variant on the same diagram with cryptic notes. so deciphering the connections for a specific set of modules is difficult.

The application note for using multiple test sets on the 8515A page is a broken link, but I was able to verify from the 8512A operation and service manual that option 001 is needed on all but the last test set in the chain. Unfortunately, neither of mine has that marked on the label. From the 8512A manual it is the A2 board, 08513-60004 (new) or 08513-69004 (rebuilt) and 15 cables.

At present it appears I need:

4x 08512-20019 port extension jumpers or suitable substitutes

2x 08510-60102 test set interconnect cables

08513-6x004 with internal cables

8511A

3x BNC cables for TRIGGER, STOP SWEEP and 10 MHz

a ST3P relay good to 26 GHz and 4x 3.5 mm cables good to 26 GHz.

The BNC cables should not be a big deal so far as I can see. I can live with 18 GHz max if I have to, but it would be nice to get it all up to 26 GHz.

Please send me PM if you have any of this for sale.

Thanks,
Reg

Hi Andy,
I asssume you sorted this out after all this time, but if not, I can send you the wiring details. And it's just a very ordinary PSU.? 5V 1A and +/-15V 0.5A.
Look on EEVBLOG and you will find various comments about psu replacement.
-Jeremy
_._,_._,_

Just a repair note:

I have seen a lot of TO92 packaged transistors where
one or more lead has become intermittent. I believe
this is caused by fiddle fingered folks that just have
to push the transistor around to match their ideal of
position, or to read the number.

It always seems to happen when the transistor is mounted
with the leads in a tripod position with the base lead
bent forwards, or backwards.

Touch, or otherwise move the transistor, and it quits...
touch it again, and it works.

-Chuck Harris

Joel,

Thanks for the detailed steps on that.

I believe I found the smoking gun, a cold solder joint. I removed A1Q1 to test it out of circuit, which really didn't lead to anything. But it started working when I re-soldered it. I'm going to carry out more testing now and see if I can do the alignment (as best I can anyway, as I don't yet have the standard cap and inductor that are called for.) I think it makes sense now...if this FET wasn't switching correctly I think it would impact the operation of the oscillator.

Sean

On Fri, Apr 3, 2020 at 12:39 PM, Joel Setton wrote:

Sean,

I think we're making progress !

In Capacitance mode, the oscillator should run at 100 kHz in the left-hand
side of the range switch, and at 1kHz on the right-hand ranges. The
frequency switch is driven by relay K1.
Your voltage measurements on both sides of R25 show that when the
oscillator is stopped, the AGC loop (IC2, IC3, Q1) is rightly "attempting"
to restart it by increasing the gain of IC1, i.e. driving A1Q1 to a low
resistance. But A1Q1 is in variable-resistance mode only if its gate
voltage is positive, hence the 2.4V ideal value.

One thing that's puzzling me is that the oscillator should run at 1kHz or
100 kHz, but never at 12 kHz.Your measurements show that it runs at 12 kHz
when it should be doing 1kHz, on the "right-hand" C ranges. Let's see what
failure could increase frequency from an ideal 1kHz to 12 kHz. The 1kHz
frequency is set by R2, R3, C3 and C5. Testing the resistors should be
easy with an ohmmeter, and I would think they are OK, because if one of
them had failed the oscillator would still work OK on 100 kHz, using R1
and R4 (but it doesn't).
Testing the capacitors is more difficult. I would think that C3 and C5 are
suspects. You may want to try this: set the meter in Capacitance mode to
the "right" ranges, when the oscillator runs at 12 kHz. Then shunt C3 with
a 1nF capacitor and look at the output frequency (12kHz or 1 kHz ?). Then
remove the 1nF shunt capacitor across C3, and put a 10nF capacitor across
C5. Again, look at the oscillator frequency (12 kHz or 1kHz ?). That will
tell us something.

If one of capacitors C3 or C5 has failed in "open" mode, it would explain
why the oscillator runs at 12 kHz instead of 1 kHz. It would also explain
why it doesn't run at all on the "left-hand" ranges because while it can
do 100kHz, it can't run at 1 MHz. IC1 and IC2 are just too slow for that.

And, as before, DO keep me posted !

Joel