Test Equipment Anonymous (TEA) group therapy thread

[Cubdriver]

Very nice find  , I'm just happy to have found one over here, will probably never see another.

The serial number plate is inside in my 524B, if you remove the plug-in, it should be on the right (if it's the same as mine).


Nice to see you have an extra gate time multiplier option fitted to your 524B, never seen that before, then again these counters aren't exactly common.
Did they have any more plug-ins for them? I've only got the two frequency converters (525A & 525B) & the 540B transfer oscillator to use with one of then, still looking for some of the other plug-ins.

Looking forward to more on the early DVM too. 

David

I went down and took a look - the 524C is a post 1961 engineering rev, more exact date TBD once I open it up.


The 524B has a pre-1960 serial number.  I'm not sure if they transitioned everything to the 1960-style multipart S/N on everything in 1960, but going on the (possibly mistaken) impression that they did, it's 50s vintage.  Again, I'll be able to tell more once I open it up and see some component date codes.  I also think they likely had stopped making the 524B by 1960 as it only appears as an afterthought in a tiny blurb at the bottom of the last 524 page in the 1959 catalog.


-Pat

[tggzzz]

Well, that is a promising start, you can never be sure of what you are going to find when the seller does not show photos of them powered. So far you have an excellent score there, well worth the trip to collect them. N%*&s are sought after in meters these days.

Probably a promising finish too. I can't even find the weston standard cell in the schematics!

I haven't found a manual for the True RMS AC Unit, and I'm not sure I can be bothered to randomly twiddle pots without knowing what they do.

I've already flipped one n%*&e DVM and I'll probably flip these, leaving me only a Fluke 8300A

The Weston cell in the 1619 & 1620 is a tiny thing, in the 1619 it's hidden under a small cover behind the range switch, almost could be confused with a fuse, but it isn't one. And yes it's dead too. 

If you want to flip the 1420 DVM, then I would be very interested, I have to say they both look in much nicer condition then what I've found locally. 

I'll keep that in mind; what's your particular interest?

The inside is a bit messy, as you would expect with a grille top panel.

From the attached PDF, it seems it is actually an LM1420.2BA

To join my Solartron DVM collection, would be nice to have the extra AC option too, also need an input cable to test & repair the standard LM1420s I have, still need to locate a two terminal input cable for the LM1440, or convert it to the later three terminal connector used on the 1420.
Forgot to mention the 1420 has a counter mode, but frequency range is quite limited.

Some extra catalog data, must be older than the pdf you have, as there is no mention of the ohms addon. The paper LM1420 manual I have only covers the standard model, no options.


David

My pdf is marked "received 2 feb 1966". A quick AC frequency test made me think of the ~20kHz and ~100kHz figures. I saw the counter option, and it looks remarkably awkward to use. The whole thing runs from a 500kc/s oscillator.

My cable is in not wonderful condition by the plug, and has the worst 4mm banana plugs I've ever used. Neither is a real problem, of course.

I looked closer at the schematic and found the Weston cell where it ought to be, but marked as X1 not the expected B1. I delved into the instrument's entrails, and found the weston cell near the range switch, but fully encased in black plastic. I was able to measure the voltage, a remarkable 1.018725V at 25C. According to Conrad Hoffmann, the voltage should be 1.0190V @ 20C, decreasing by 5µV/C as the temperature rises, so if new my cell should be 1.018975V. Cells tend to decrease voltage by 25µV/year (with quite a wide range), so my 250µV fall equates to 10years. Not bad for something that is at least 50yo with a life expectancy of 7-14years, with 1.0183V being the endpoint!

The pictures below show a general view including internal dust, the rather strange back panel, and two of the Weston cell, DC range, and AC electronics. The yellow Wima caps next to the Weston cell are the switchable input RC filter, 3dB at 11Hz.

In deference to Vince, I'll leave you to expand them.

EDIT: added the last photo, showing details of the condition of some digital and display boards. All digital circuits circuits are classic 2 transistor 2 diode 6 resistor 4 capacitor multivibrators, or similar.

[tggzzz]

Mmmmm...  Nixie goodness!   

Yup; in two forms, filtered and unfiltered as per https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg4244440/#msg4244440



The more I use the the less I dislike them, which doesn't bode well for my flipping them

[vk6zgo]

33.5 ºC (93 frankenstein) in the shade outside here at the moment. I ought to go out and wash the (filthy) car, but that ain't happening, and I've got minced beef in the fridge that has to be cooked today. Cook? In this weather? Better go and get it started; at least it means tacos for tea.

That was the grumpy old man weather report. We now return you to your normal programming...

18C here, & it's supposed to rain like a bastard later in the day-----we'll see!

[Cubdriver]

Mmmmm...  Nixie goodness!   

Yup; in two forms, filtered and unfiltered as per https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg4244440/#msg4244440



The more I use the the less I dislike them, which doesn't bode well for my flipping them

Interesting how they filtered one to orange, and the other to red.  Is the red one a newer instrument?  Perhaps aiming to mimic red LEDs if they were contemporary to it?

And nixie gear should not be flipped - it should be treasured and used!   

-Pat

[vk6zgo]

ok, had some help of my friends today.
We had a look at some acoustics issue in my music room.
So a friend came over and brought his spectrum analyzer and additional equipment. Now we have an almost linear frequency response at the place where I usually sit. And the sound is about as expected. So the issue is fixed.
Then had a look at a pair of Montan speakers that were missing the upper (tweeter) frequencies.
It's the tweeters !
Nope, it's the crossover
Nope, it's the tweeters !
Nope, let's measure the tweeters (measured out ok)
swapped out tweeters (did not do the trick)
bypassed crossover and hooked up tweeters directly to the input -> tweeters tweeting the way they are supposed to
my friend was baffled. he took both crossovers for repair at his shop (he knows shitloads more about audio than I do ...
So when those are back: rebuild the other Quadral set to have another high end stereo set (this time in the living room). He also took along my Nakamichi OMS 7 Mk2 which had not survived moving. Let's see if he can fix it.
Next: continue sorting out stuff, sorting pinball parts, bring the dracula back to live.

Sounds a bit like when I worked at the Hearing place.
One of our jobs was to characterise the testing rooms, both ours, & other organisations.
We lugged a lot of gear along for the outside jobs & spent about an hour----dunno why, really, the rooms weren't going to change much, but those were the rules!

[vk6zgo]

oh beautiful torrential rains of Ferenginar ...

Hubby will hate me.
I won a auction for bagpipes 
Have a buyer for one of my compound manual stick accelerators, plus got a Nakamichi ST7E for old times sake.

If there' bagpipes, better be original jokes:
https://electricscotland.com/familytree/ceilidh/bagpipe.htm

I liked "Why did the bagpiper get mad at the drummer? Drummer moved a drone pipe and wouldn't tell which one.", but most of the others are fairly generic.

Pipers are very possessive of their pipes, & would not like anyone messing with them.
They also become adept at retuning the drones "on the day", as they drift quite a lot in tuning---the chanter* not so much.
Hmm, just a thought on the drifting-------did Marconi ever make bagpipes?

* I've only heard that bit referred to as a "chanter", though it promotes confusion with the recorder-like "practice chanter."

[tggzzz]

Mmmmm...  Nixie goodness!   

Yup; in two forms, filtered and unfiltered as per https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg4244440/#msg4244440



The more I use the the less I dislike them, which doesn't bode well for my flipping them

Interesting how they filtered one to orange, and the other to red.  Is the red one a newer instrument?  Perhaps aiming to mimic red LEDs if they were contemporary to it?

And nixie gear should not be flipped - it should be treasured and used!   

The LM1420 has nixies marked 69xx. I can't see the nixies in the other, nor any other datestamps.

I've so many DMMs that they the ones on the floor are preventing me fully opening the door to get into my workroom. Along with a dekatron based counter, a couple of Panaplex meters (which I prefer to look at), plus several VFD meters and LCD meters, I'm planning on keeping this nixie Fluke:

[mnementh]

Now now, bd... don't poke the frog with a stick. too hard.

Vince is coming around, I think... as he is exposed to better and better gear with a little help from his friends, it's pretty clear that his definition of what actually qualifies as an oscilloscope, etc is also being readjusted a wee bit, and he's realizing that a lot of those units he's been "gonna get round tuit" really aren't worth the "round tuits" they'll cost him.

Remember, I've also had to reevaluate similarly... it's a painful reckoning, to be sure. 

mnem
*tinker-tinker... putter-putter*

No not quite.... I didn't say I was seeking "better" and better gear, as in "moder modern and capable "...  though it's nice as well.

No I meant I was getting more critical in the sense that my "taste" for OLD stuff  is evolving, but it's still old "junk" in the grand scheme of things...

Out of my 40/45 scopes, the vast majority are scopes I REALLY like, and that I am extremely unlikely to ever part with.
Point is, these old scopes aren't plentiful nor cheap. Modern stuff is disposable :  want one ? Just spend the money and go on-line to get one, job done, a few clicks away.
Not so with older stuff. So every time I manage to lay my hands on some old piece gear that I like, it makes no sense to sell it later, because it's worth much more to me, as an emotional object, and the history behind it, and the fun I get out of playing with it, the joy of simply being able to look at it in the flesh up close... than the few bucks I could get, if at all, from selling it.

Half of my scopes are the glowing Tek scopes, they aren't going anywhere.  A third will be restored, the rest are invaluable as parts mules. Infinitely more useful to me for parts than the few bucks I would get from selling them.

There are only a very few scopes I would be OK to get rid of, and only a couple that I actually WANT to get rid of, because I don't like them and only bought them because they were cheap and I am hoping to make 50 Euros of profit once fixed. 

So the plan is to try to contain my scope "collection" / inventory to the current level, possibly lower it a bit by 3 or 4 maybe, but I don't see how it could ever get much lower than that.
All the parts mules are very valuable to me, bang for buck, so the plan I think, what makes most sense, is to keep them all for as long as technically / practically possible, and resort to selling as few as possible of them, only when I really, really need the space for something else. But for now I just keep gathering them.

Am I horrible in that I hear all of that being sqweeked by this little guy now...? 



I'm sorry V... I can't help it... 

mnem
*tries to bite tongue* "mmmnmmmblmmmph...mmmnmmmmblmmmmph-ba-wa-ha-ha-ha-ha-ha-ha-ha!!!"

[nixiefreqq]

just wanted to say thanks to vince and mnem for providing information and motivation to help investigate the hp 54657a measurement/storage module.

noodled around with my hp 54601a and found the following:

the time and date functions work fine when the scope is powered up but get scrambled after powering down and restarting.

conclusion -  the battery in U7, a dallas ds1244y-120 (32k x 8 and clock) .......is dead. (1992 date code)

the 99 waveform trace and set up memories work fine when the scope is powered up but are all gone after powering down and restarting.

conclusion -  the battery in U8, a dallas ds1245y-120 (128k x 8 )........ is dead. (1992 date code)

all of the fancy measurement and waveform math features to include fft are still working.

conclusion -  the firmware for those features is in the am27c2048 rom (128k x 16).

so am i gonna' mess with the nvram chips just to timestamp and store waveforms inside the box?  hell no.

the thing i like most about this piece is that it does the best X-Y mode of any dso in the basement, and works great with my homebrew curve tracer.
i have used it to save curves from different transistors and then step between them for comparison.  always assumed that those memories were volatile because the manual says "the two trace memories built into the basic unit are volatile".  the spec sheet below (provided by vince) made me go back and check the manual, and sure enough it says that with the interface module added you get 99 nonvolatile traces. 

so now with dead dallas batteries i have 99 volatile traces.  that's good enough for me.


54657a features:

* Full Programmability.
• Hardcopy output.
• Three additional automatic voltage measurements (amplitude,
preshoot, and overshoot).
• Two additional automatic time measurements (delay and phase
angle). User defined measurement thresholds of 10%/90%,
20%/80%, or selected voltage levels.
• Two additional cursor measurements (voltage in percent and time
in degrees).
• Two additional cursor measurement sources (math function 1
and 2).
• Waveform math functions (addition, subtraction, multiplication,
differentiation, integration, and FFT)
• Time and date tagging of hard copy and and nonvolatile memories.
Three uncompressed nonvolatile trace memories.
• Additional 64K of nonvolatile trace memory (with data
compression) for up to 97 more trace memories..
• Unattended waveform monitoring by use of mask templates.
• Built-in automatic mask generation and mask editing capabilities.


edit  the unit shown is mnem's, because his pic was a lot better than mine.

[mnementh]

just wanted to say thanks to vince and mnem for providing information and motivation to help investigate the hp 54657a measurement/storage module.

noodled around with my hp 54601a and found the following:

the time and date functions work fine when the scope is powered up but get scrambled after powering down and restarting.

conclusion -  the battery in U7, a dallas ds1244y-120 (32k x 8 and clock) .......is dead. (1992 date code)

the 99 waveform trace and set up memories work fine when the scope is powered up but are all gone after powering down and restarting.

conclusion -  the battery in U8, a dallas ds1245y-120 (128k x 8 )........ is dead. (1992 date code)

all of the fancy measurement and waveform math features to include fft are still working.

conclusion -  the firmware for those features is in the am27c2048 rom (128k x 16).

so am i gonna' mess with the nvram chips just to timestamp and store waveforms inside the box.  hell no.

the thing i like most about this piece is that it does the best X-Y mode of any dso in the basement, and works great with my homebrew curve tracer.
i have used it to save curves from different transistors and then step between them for comparison.  always assumed that those memories were volatile because the manual says "the two trace memories built into the basic unit are volatile".  the spec sheet below (provided by vince) made me go back and check and sure enough it says that with the interface module added you get 99 nonvolatile traces. 

so now with dead dallas batteries i have 99 volatile traces.  that's good enough for me.


54657a features:

* Full Programmability.
• Hardcopy output.
• Three additional automatic voltage measurements (amplitude,
preshoot, and overshoot).
• Two additional automatic time measurements (delay and phase
angle). User defined measurement thresholds of 10%/90%,
20%/80%, or selected voltage levels.
• Two additional cursor measurements (voltage in percent and time
in degrees).
• Two additional cursor measurement sources (math function 1
and 2).
• Waveform math functions (addition, subtraction, multiplication,
differentiation, integration, and FFT)
• Time and date tagging of hard copy and and nonvolatile memories.
Three uncompressed nonvolatile trace memories.
• Additional 64K of nonvolatile trace memory (with data
compression) for up to 97 more trace memories..
• Unattended waveform monitoring by use of mask templates.
• Built-in automatic mask generation and mask editing capabilities.


edit  the unit shown is mnem's, because his pic was a lot better than mine.

LOL.... that's EXACTLY why I posted those pics; so they could be a resource for anybody who bothered to search for 54657A on eevBlog.

Your logic seems impeccable... makes me hope the NVRAM on the bottom of my 54645A & 54600A are similarly used to store setups, etc. and not mission critical for daily use.

I DO wish I had access to a dental X-ray now tho... 

mnem
 

[mnementh]

I stopped by a clearance place that had these Fluke laser distance measurers listed for sale on the way to football practice yesterday afternoon and picked one up:

   This should be fun to play with.  I'm going to take it outside and do some measurements in the back yard later once the sun's set and it'll be easier to see the marker dot.

This was a total dead on arrival dud.

The laser would come on and then I'd push the measure button to take a reading and it would throw error 255.  According to the manual, that indicates the reflected signal off the surface you're measuring from is too low or it's taking too long.  One side of the living room to the other is well within the 50m range of the device and then the laser quit entirely so I thought even when the beam was visible, maybe the batteries that came installed in it were on their last legs and the return power from the laser it was too low for the device to work with before it stopped shining entirely.

I pulled the batteries and measured them out at 1.3V open circuit so I replaced them with new which I double checked and measured at 1.56V.  The laser is still dead and it's still throwing error 255 which would be correct since the signal is low, because it isn't supplying one.  I guess I need to deal with the clearance store that sold me this last week, Fluke, or the credit card company.  Even at clearance prices, this wasn't cheap enough for me to be willing to write off.

Aside from this specific example not working, the build quality and feature set are disappointingly lacking.  Granted, it was the base model Fluke, but I would have expected better from the brand and there is definitely a hefty price premium for the name.  But the lack of a tripod socket really surprises me.

Perhaps a Chinesium counterfeit...? 

mnem
 

[mnementh]

oh beautiful torrential rains of Ferenginar ...

Hubby will hate me.
I won a auction for bagpipes 
Have a buyer for one of my compound manual stick accelerators, plus got a Nakamichi ST7E for old times sake.

If there' bagpipes, better be original jokes:
https://electricscotland.com/familytree/ceilidh/bagpipe.htm

I liked "Why did the bagpiper get mad at the drummer? Drummer moved a drone pipe and wouldn't tell which one.", but most of the others are fairly generic.

Pipers are very possessive of their pipes, & would not like anyone messing with them.
They also become adept at retuning the drones "on the day", as they drift quite a lot in tuning---the chanter* not so much.
Hmm, just a thought on the drifting-------did Marconi ever make bagpipes?

* I've only heard that bit referred to as a "chanter", though it promotes confusion with the recorder-like "practice chanter."

Wait... what...? A bagpipe is supposed to be tuned...? 

You mean like with new points & condenser, occasionally some new HV wires attached to the poor animal being tormented inside that sac, right?

mnem
*tzzzzt-howwwwlll!!!*

"Nay, clip it on a bit lower; 'es a little flat..."

[Saskia]

if the marten which sneaked in howls in agony and leaves, then it was tuned quite right.

[TERRA Operative]

just wanted to say thanks to vince and mnem for providing information and motivation to help investigate the hp 54657a measurement/storage module.

noodled around with my hp 54601a and found the following:

the time and date functions work fine when the scope is powered up but get scrambled after powering down and restarting.

conclusion -  the battery in U7, a dallas ds1244y-120 (32k x 8 and clock) .......is dead. (1992 date code)

the 99 waveform trace and set up memories work fine when the scope is powered up but are all gone after powering down and restarting.

conclusion -  the battery in U8, a dallas ds1245y-120 (128k x 8 )........ is dead. (1992 date code)

all of the fancy measurement and waveform math features to include fft are still working.

conclusion -  the firmware for those features is in the am27c2048 rom (128k x 16).

so am i gonna' mess with the nvram chips just to timestamp and store waveforms inside the box.  hell no.

Nope, sorry, that's completely unacceptable!

You are supposed to poke at it to fix it until you proper break it, then spend inordinate amounts of time and effort to eventually fix it properly! And only after giving up at least once to let it mature on the shelf for a few months until you forget the initial pain from the first go you had at it....   

(story of my TEA life..  )

[Wolfgang]

oh beautiful torrential rains of Ferenginar ...

Hubby will hate me.
I won a auction for bagpipes 
Have a buyer for one of my compound manual stick accelerators, plus got a Nakamichi ST7E for old times sake.

Even bagpipes can be used for good music:

[mansaxel]

You are supposed to poke at it to fix it until you proper break it, then spend inordinate amounts of time and effort to eventually fix it properly! And only after giving up at least once to let it mature on the shelf for a few months until you forget the initial pain from the first go you had at it....   

(story of my TEA life..  )

That's about right.

All this talk of Solartron made me go and fire the old one up. This is in as-received condition; I only fitted a Bulgin Horror-Plug and twiddled the trimpots a bit.



I'm feeding it a 10vpp 400 Hz AC sine.


$ dc
5k
10
2/
2v
/p
3.53554


Apparently needs Work(tm).

Would it too include some Poisonous Electrick-Chemistry?

[tggzzz]

You are supposed to poke at it to fix it until you proper break it, then spend inordinate amounts of time and effort to eventually fix it properly! And only after giving up at least once to let it mature on the shelf for a few months until you forget the initial pain from the first go you had at it....   

(story of my TEA life..  )

That's about right.

All this talk of Solartron made me go and fire the old one up. This is in as-received condition; I only fitted a Bulgin Horror-Plug and twiddled the trimpots a bit.



I'm feeding it a 10vpp 400 Hz AC sine.


$ dc
5k
10
2/
2v
/p
3.53554


Apparently needs Work(tm).

Would it too include some Poisonous Electrick-Chemistry?

If you press the "CAL 10192" button you will find out if the hazmat still contains sufficient electrickery.

Before spelunking, let it warm up, input a known DC voltage, and twiddle the two front panel trimpots. RTFM to find whether the input should be shorted or open.

My new treasure takes a long time to settle on the AC ranges, and you have to use intelligence to estimate whether th RMS circuit is overloaded. The hint for that is that there are many more AC ranges than DC ranges.

[mansaxel]

If you press the "CAL 10192" button you will find out if the hazmat still contains sufficient electrickery.

Before spelunking, let it warm up, input a known DC voltage, and twiddle the two front panel trimpots. RTFM to find whether the input should be shorted or open.

My new treasure takes a long time to settle on the AC ranges, and you have to use intelligence to estimate whether th RMS circuit is overloaded. The hint for that is that there are many more AC ranges than DC ranges.

If I push that button, the voltage comes up, and can be poked at with the trimpot. I can get it up to 1,02V, at least. It screams bloody murder and overload on any DC range except the last two. Perhaps not when shorted. I suspect a silly high input impedance. And contact cleaner deficiency.

[tggzzz]

If you press the "CAL 10192" button you will find out if the hazmat still contains sufficient electrickery.

Before spelunking, let it warm up, input a known DC voltage, and twiddle the two front panel trimpots. RTFM to find whether the input should be shorted or open.

My new treasure takes a long time to settle on the AC ranges, and you have to use intelligence to estimate whether th RMS circuit is overloaded. The hint for that is that there are many more AC ranges than DC ranges.

If I push that button, the voltage comes up, and can be poked at with the trimpot. I can get it up to 1,02V, at least. It screams bloody murder and overload on any DC range except the last two. Perhaps not when shorted. I suspect a silly high input impedance. And contact cleaner deficiency.

Contact cleaner helped me.

If the reference is too low, then the cal tweak will add too much gain which might lead to internal overload. If you twiddle the CAL until the display reads the same as a decent voltmeter, does it still overload?

The "tweak until the neon voltage plus gain leads to the right display" always was a horrible hack based on available technology.

[factory]

If you press the "CAL 10192" button you will find out if the hazmat still contains sufficient electrickery.

Before spelunking, let it warm up, input a known DC voltage, and twiddle the two front panel trimpots. RTFM to find whether the input should be shorted or open.

My new treasure takes a long time to settle on the AC ranges, and you have to use intelligence to estimate whether th RMS circuit is overloaded. The hint for that is that there are many more AC ranges than DC ranges.

If I push that button, the voltage comes up, and can be poked at with the trimpot. I can get it up to 1,02V, at least. It screams bloody murder and overload on any DC range except the last two. Perhaps not when shorted. I suspect a silly high input impedance. And contact cleaner deficiency.

Yes it has high input impedance on all DC ranges, apart from 100V & 1kV, those are 10MΩ. AC is 10MΩ or 1MΩ depending on range.




A couple more below from the same catalog, for the LM1440/1480, I've got the 1440.

And the portable LM1240, which also uses the obsolete PH163 mains connector, the inlet is moulded into the case, I think it's a rebadged Weston 1240 as shown here; http://madrona.ca/e/edte/Weston1240/index.html



David

[Saskia]

ok, had some help of my friends today.
We had a look at some acoustics issue in my music room.
So a friend came over and brought his spectrum analyzer and additional equipment. Now we have an almost linear frequency response at the place where I usually sit. And the sound is about as expected. So the issue is fixed.
Then had a look at a pair of Montan speakers that were missing the upper (tweeter) frequencies.
It's the tweeters !
Nope, it's the crossover
Nope, it's the tweeters !
Nope, let's measure the tweeters (measured out ok)
swapped out tweeters (did not do the trick)
bypassed crossover and hooked up tweeters directly to the input -> tweeters tweeting the way they are supposed to
my friend was baffled. he took both crossovers for repair at his shop (he knows shitloads more about audio than I do ...
So when those are back: rebuild the other Quadral set to have another high end stereo set (this time in the living room). He also took along my Nakamichi OMS 7 Mk2 which had not survived moving. Let's see if he can fix it.
Next: continue sorting out stuff, sorting pinball parts, bring the dracula back to live.

Sounds a bit like when I worked at the Hearing place.
One of our jobs was to characterise the testing rooms, both ours, & other organisations.
We lugged a lot of gear along for the outside jobs & spent about an hour----dunno why, really, the rooms weren't going to change much, but those were the rules!

not quite. we derived a crossover mapping which was programmed into the system based on the spectrum analysis at the listening position.it was worth every penny.

[Vince]

just wanted to say thanks to vince and mnem for providing information and motivation to help investigate the hp 54657a measurement/storage module.

noodled around with my hp 54601a and found the following:

the time and date functions work fine when the scope is powered up but get scrambled after powering down and restarting.

conclusion -  the battery in U7, a dallas ds1244y-120 (32k x 8 and clock) .......is dead. (1992 date code)

the 99 waveform trace and set up memories work fine when the scope is powered up but are all gone after powering down and restarting.

conclusion -  the battery in U8, a dallas ds1245y-120 (128k x 8 )........ is dead. (1992 date code)

all of the fancy measurement and waveform math features to include fft are still working.

conclusion -  the firmware for those features is in the am27c2048 rom (128k x 16).

so am i gonna' mess with the nvram chips just to timestamp and store waveforms inside the box.  hell no.

I beg to disagree ! 

As you saw my serial // module does NOT have an EPROM, only the two NVRAM chips and that's it ! Yet as the manual states, all modules give access to 100% the same extra features.

So as was discussed earlier here, the F/W must be in one or two of the NVRAM, unlikely as it's silly from an enginerring point of view + yo need that RAM space to store all the waveforms and their metadata like time stamps. Need space for the mask feature if you use that.  So the most likely solution here as as suggested is that the code for these extra features is already in the scope itself, on the main board, and the module NVRAM chips just provides the RTC and user data storage space.

So, the EPROM chip in the GPIB module is most likely there to support the GPIB stuff itself.. probably because there was enough ROM space left on the scope mainsboard because... they filled it to the top in order to cram the extra module features into it.

That's my best guess so far.

Once my lab is computerized + chip programmer + desoldering gun ... I will start playing this thing. Remove the two NVRAM chip to read them to confirm there is no code in there.
I bet if you read that EPROM in your GPIB module you would see only GPIB related stuff, but nothing about all the extra features that all these modules implement...

[tggzzz]

Edit: Different version of Muirhead miniature standard cell used in some of these DVMs. Picture from here http://dexterslab2013.blogspot.com/2015/10/teardown-vintage-solartron-lm1619-volt.html

That's the same as mine, but the Muirhead designation isn't visible.

[tggzzz]

I'll keep that in mind; what's your particular interest?

To join my Solartron DVM collection, would be nice to have the extra AC option too, also need an input cable to test & repair the standard LM1420s I have, still need to locate a two terminal input cable for the LM1440, or convert it to the later three terminal connector used on the 1420.

All good solid defensible TEA/GAS reasons

Here's a picture showing details of the condition of some digital and display boards; nothing too surprising.

All digital circuits circuits are classic 2 transistor 2 diode 6 resistor 4 capacitor multivibrators, or similar.