Re: [volt-nuts] EPROM Programmer

[Todd Micallef]

Randy,

I use the GQ-4X from mcumall.com. It works great and I have had no problems
with it. I have bought a few adapters to support PLCC and SOIC packages.

For the NVRAM, don't overlook the STMicroelectronics memory. I have used
the M48Z12 as a direct replacement.with no issues. The only thing I didn't
like was the date code format on the part. They only list the last digit of
the year and week. I guess if you replace it every 10 years it is not an
issue.

Todd.

On Tue, Nov 7, 2017 at 10:08 PM, Randy Evans 
wrote:

> Can someone recommend a good low-cost method to program the DS1220 and
> DS1230 NVRAMs for the HP-3458A?  I downloaded the CAL contents and I need
> to program new NVRAM chips to replace the older (very old) NVRAMs still in
> the unit.
>
> Also, will the DS1220AD and DS1230AD chips work in place of the
> existing DS1220Y
> and DS1230Y NVRAMs in the HP-3458A?  The AD versions have different timing
> "power good" specifications and they don't work as a plug-in substitute in
> all cases.  I assume some 3458A users have changed out the NVRAMs with the
> new Dallas parts ( Dallas no longer makes the DS1230Y NVRAM, but does still
> make the DS1230Y NVRAM, according to their data sheet).
>
> Thanks,
>
> Randy Evans
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[volt-nuts] EPROM Programmer

[Randy Evans]

Can someone recommend a good low-cost method to program the DS1220 and
DS1230 NVRAMs for the HP-3458A?  I downloaded the CAL contents and I need
to program new NVRAM chips to replace the older (very old) NVRAMs still in
the unit.

Also, will the DS1220AD and DS1230AD chips work in place of the
existing DS1220Y
and DS1230Y NVRAMs in the HP-3458A?  The AD versions have different timing
"power good" specifications and they don't work as a plug-in substitute in
all cases.  I assume some 3458A users have changed out the NVRAMs with the
new Dallas parts ( Dallas no longer makes the DS1230Y NVRAM, but does still
make the DS1230Y NVRAM, according to their data sheet).

Thanks,

Randy Evans
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[volt-nuts] Solartron 7081

[Alexander Kokorin via volt-nuts]

Hi All,
FYI, Solartron 7081 is on Ebay.
Best regards,Oleksandr Kokorin
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Re: [volt-nuts] 3420B chopper drive problem

[David C. Partridge]

Well that would explain a lot!  Both diodes are wired with the cathode to the 
neon!  

Does it matter which one I reverse?

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Dr. Frank
Sent: 07 November 2017 16:32
To: volt-nuts@febo.com
Subject: [volt-nuts] 3420B chopper drive problem

Hello Dave,

in the schematic, the polarity of the diodes in series with the neon bulbs is 
definitely wrong.

If you compare with the 3420A on page 7-7 (29), but also with the Fluke
845 which is similar, both neons have to be switched at 180°.

Maybe someone else has erroneously reversed one of the diodes in your unit 
before?

If both neons are really firing in phase, instead, that could explain this 
non-symmetric waveform, which you observe.

Frank

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[volt-nuts] 3420B chopper drive problem

[Dr. Frank]

Another probable error in the manual, on page 5-8 (80), diagram, which 
shows the monitoring of the neon currents:


That diagram is ok for the A-version, as both neon currents are measured 
with the same polarity in its oscillator circuit.


The B-version anyhow should look different, as the currents should be of 
different polarity, so a positive pulse with about +150mV, and a 
negative pulse with -75mV (or vice versa, depending on the polarity of 
the diodes), always a signal pause at 0V.


One neon current is monitored over 51 Ohm, the other one over two 51Ohm 
reistors in series, therefore these different amplitudes.


Frank

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[volt-nuts] 3420B chopper drive problem

[Dr. Frank]

Hello Dave,

in the schematic, the polarity of the diodes in series with the neon 
bulbs is definitely wrong.


If you compare with the 3420A on page 7-7 (29), but also with the Fluke 
845 which is similar, both neons have to be switched at 180°.


Maybe someone else has erroneously reversed one of the diodes in your 
unit before?


If both neons are really firing in phase, instead, that could explain 
this non-symmetric waveform, which you observe.


Frank

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[volt-nuts] 3420B chopper drive problem

[David C. Partridge]

I'm trying to resurrect a 3420B.

I'm looking at the waveform at TP1 on the A2 board.  This is supposed to be
a square(ish) wave, but within a 6mS period, there should be two cycles of
the signal, one with an amplitude of (say) 150mV, and the next cycle only
100mV.   I think that  the larger should be symmetric about 0V, and the
other only somewhat above 0V at the peak.

What I actually observe is a square wave with all cycles the same amplitude
and only -ve going.  I can adjust the amplitude using A2R10 up to about
250mV p-p. 

The chopper neons are part of this circuit, and I'm having problems getting
my head round what could be wrong.

Both neons appear to be firing.

The schematic is page 7-15 in the manual (which for some reason is on page
37 of the scan on the Keysight website):



Any help in understanding what's wrong will be most gratefully received.

Thanks
Dave



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