BIll Ezell | 26 Apr 18:11 2016
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Re: PCB fasteners for Datron meters (David C. Partridge)

I've tried finding a US distributor. Same story, the only one that 
claims to sell them has no inventory. Not very useful.

On 4/26/2016 12:00 PM, volt-nuts-request@... wrote:
>   Re: PCB fasteners for Datron meters (David C. Partridge)
> So far I’ve not found anyone who actually stocks them

--

-- 
Bill Ezell
----------
The day Microsoft makes something that doesn't suck
will be the day they make vacuum cleaners.
Or maybe Windows 10.

David C. Partridge | 24 Apr 16:33 2016
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PCB fasteners for Datron meters

I think I've managed to identify the fasteners used to secure the PCBs in
Datron meters and other test equipment.

I've sent an email to the suppliers to see if I can order in smallish
quantities.

Is anyone interested to tag along?

Dave

Four Designs Company | 22 Apr 18:19 2016
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Re: volt-nuts Digest, Vol 80, Issue 14; Solratron cal issue

It has been some years since I last worked on a 7081, and I don't have 
the manuals at hand..
Is there a way to clear the EAROM contents and perhaps load starting cal 
constants? I think the EAROM data is corrupt or so far off that it 
cannot compute new values.

Bob

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> Today's Topics:
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>     1. Solartron 7081 calibration problems (David C. Partridge)
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(Continue reading)

David C. Partridge | 21 Apr 21:52 2016
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Solartron 7081 calibration problems

I spent some of today attempting to calibrate a 7081 that has had the EAROM
chip (ER3400) on the in-guard (floating) logic board replaced.

For each calibrate command issued I get a "Cal Incomplete" message rather
than a "Cal OK" message (this *may* be OK, or *may* be a fault).

When I try to issue calibrate, reference, 10.00000 I get a message "Factor
out of range" (all other VDC, VAC, and KOHM calibrate commands worked apart
from the Cal Incomplete message).

Does anyone know what the problem is, or have any thoughts as to what the
probable cause might be?

On a very related point, how do you calibrate the Ratio calibration constant
(there's nothing in either the Service manual or the Test Specification
about this other than item 21 in the automated  checks section on page 16
which says:

22. Ratio - ratio is calibrated.

Dave

BIll Ezell | 19 Apr 18:19 2016
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Re: Replacement displays for Solartron 70x1 meters

The FG209 VFDs came in about 6 or so variants, mostly having to do with whether or not it had decimal points,
+/- signs, etc.
The M2 variant is the exact replacement for 7081's, 71's and 61's, and that's the one on EBay.
I've also used the C2 variant in my 7081.
I was looking for my Noritake datasheet to find out the differences, but I apparently didn't save it and now
it seems impossible to find. Sigh.

----------
I was just pointed to eBay listing 271905098924 (thank you Peter) which has
some of the Noritake FG209 VFDs that I am pretty sure fit the Solartron 70x1
meters, should anyone need one.

--

-- 
Bill Ezell
----------
The day Microsoft makes something that doesn't suck
will be the day they make vacuum cleaners.
Or maybe Windows 10.

David C. Partridge | 19 Apr 10:47 2016
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Replacement displays for Solartron 70x1 meters

I was just pointed to eBay listing 271905098924 (thank you Peter) which has
some of the Noritake FG209 VFDs that I am pretty sure fit the Solartron 70x1
meters, should anyone need one.

Dave

David C. Partridge | 17 Apr 16:05 2016
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Datron-Wavetek group created on groups.io

To add to the fun I've also created a Datron-Wavetek group on Groups.io to
discuss Datron and Wavetek test equipment including, but not limited to,
meters and calibrators.

Cheers

Dave

BIll Ezell | 14 Apr 18:31 2016
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Re: Solartron 7081 randomly re-initialises


Repost from my response in the new Solartron group, :

 >I assume you've eliminated obvious things like power-line spikes? One 
other thing comes to mind, the power-up reset logic for the CPU, the 
RESET >signal. My schematics are so bad it's hard to tell for sure, but 
it looks like that's generated by R6 and C2, along with IC4 on the 
earthy board. I'd check >C2, if it's very leaky, could be pulling IC4-1 
down enough to give random triggering. IC6 is a possibility also, IC6-6 
is used to also trigger a reset by >pulling C2 to ground.

I'd think if there was enough ripple on the 5V supply to trigger a 
reset, you'd be seeing other bad things.

Regading the nvram, the comments on that are dead-on, my cross post 
about that:

 >The cal constants are in a non-volatile ram, it's possible you'll need 
to replace that. I've never seen a failure, but I've heard anecdotally 
that they can >fail. It's also possible that your meter has been sitting 
unused for so long that the nv-ness of the ram has leaked away.
 >They work by injecting a stored charge into effectively a 
well-insulated gate. Over many years, the charge can leak away. That's 
why there's a rewrite >cycle the meters can do.

I forget what the nvram refresh command is, but it's in the manual. 
Also, the nvram keeps two separate copies. I thought it would 
automatically try to read the second copy if the first was bad, and 
automatically rewrite the bad one. But, if enough charge has leaked, 
there could be multiple errors across the entire nvram.
(Continue reading)

David C. Partridge | 14 Apr 11:45 2016
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Solartron 7081 randomly re-initialises

One of my 7081s will occasionally re-start from running in TRACK mode,
ending up with the INITIALIZED message on the display.

Does anyone have any thoughts as to likely faults that would cause this?

Dave

David C. Partridge | 13 Apr 01:01 2016
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New group for discussion of Solartron and Schlumberger Test and Measurement Equipment

I've just created a Groups.io group called Solartron_Schlumberger_Equipment
for discussion of Solartron and Schlumberger Test and Measurement Equipment.

All are welcome to ignore this or to join as they please J

Dave

BIll Ezell | 12 Apr 22:27 2016
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Yet another sub-nanosecond pulse generator thread

(cross-posting to time-nuts)
After paying only limited attention to this topic, I suddenly have a 
need for a pulse generator that has <150 ps risetime and a pulse width 
of at least 2 ns. I've looked at the classic Jim Williams avalanche 
generator, but I don't want to have to deal with the (relatively) high 
voltage source needed.

I've done microwave design using Gunn diodes, so I'm drawn to using a 
step-recovery diode. The topology seems very straightforward, and I can 
build it right onto a BNC connector, no PCB.

I'm thinking using an SMD835 diode, biased at ~1ma. The (sketchy) 
datasheet claims a T of 20 nsecs and a Tr of 85 ps, Cj of 0.4 to 0.8 pf.

Questions:

The obvious, is it reasonable?

Is the bias current reasonable? I'm assuming the bias current is 
actually dependent on the repetition rate, you need enough current to 
replenish the charge within one pulse cycle. I suppose I could compute 
it from the stated junction capacitance, but I'm not sure that's the 
only factor

Will the stored charge actually give me the desired transition rate into 
50 ohms? Hmm, again I should be able to compute this, but any other 
factors ignoring the non-diode ones like cap inductance?

How should I compute the coupling cap from the diode to the load? Use 
the impedance at the pulse rep rate? Seems reasonable. BTW, I don't care 
(Continue reading)


Gmane