Test Equipment Anonymous (TEA) group therapy thread

[worsthorse]

There are plenty for sale, none with a visible trace, and some with an entertaining price tag. The tunnel diodes are fragile (hence the strange shorting BNC) and notoriously difficult to obtain.

Be aware that the PSU is strange in the extreme: there's an off-24V switcher based around a PUJT and an SCR, and it attempts to keep a constant mean current going into the battery. They don't even switch on unless there is a working NiCd battery in them (or NiMH but watch the currents, especially for ~400ms after you plug in the mains).

Soooo... what appeared on my local CL today but a TDR 1503 that doesn't power up and, based on the photos, was probably dropped. 



Though I know fixing something like this is way above my pay grade, I am tempted to give it a go anyway, so I came back here to this post to remind myself why it is a terrible idea.

Not that it will stop me. *sigh*

[Carl_Smith]

mnem
Fortunately I keep my scales numbered, for just such an occasion...

[bitseeker]

Yeah, but we don't SEE him tearing it apart, so I expect the case is as others have suggested; that they sent a working unit AND whatever internal components they felt like allowing him to fondle onscreen. I can't see them allowing any third party to tear apart a working unit, especially one of such  stratospheric value. IIRC, the boards he's messing with are 4-Channel, however the working scope is clearly 2-Channel.

And they certainly don't want anyone having access to internal ports, headers, etc on a working unit such that a working copy of proprietary FW could conceivably be extracted by someone of his obvious skill.

Yes that is exactly what he said at the start of his video, he was supplied with the extra parts to enable him talk about them. He did not take it apart.

Yep, I should've rewatched rather than relying on my old memory and the "teardown" in the title.

[bitseeker]

Well if those LCD conversion kits from newscope were affordable that would be an option.

Look really cool though.

I recently came across this method that seems impressive with enhancing capabilities also with math functions and views.


He references his Github files in the description too.   I've seen these going for as low as $50 brand new.

This is the first I've seen such an upgrade for a 141. Hmmm... yes... TEA...

[bitseeker]

Hello TEA community - I have made a post under the wider 'Test Equipment' category, just to reach those too that do not dare come in here. Nevertheless, I would like to bring this to your attention, as I am suspecting that the answer might come from one of you - if any..
See here:
https://www.eevblog.com/forum/testgear/info-on-gouldsiemens-dso-demonstration-device-sought/msg2301666/#msg2301666

That's very considerate of you, Neomys. 

[bitseeker]

Hello TEA community - I have made a post under the wider 'Test Equipment' category, just to reach those too that do not dare come in here.

Hmmm. Perhaps we should work on being more welcoming?

I don't think it's a question of being welcoming. The real issues are that (1) not everyone would be coming into this thread to answer questions and (2) often, posts fill the thread so fast that most people would miss it. So, I think it was a good call to start a topic-specific thread.

[0culus]

I am amusing myself tonight (well, procrastinating real work) by making output pin traces on my FPGA boards into unintended transmission lines.  In reality, I'm playing with linear feedback shift registers and sending the relevant signals to the scope.

[bitseeker]

This question seems appropriate here.  Okay all, what is the one piece of TE that really got you started, the one piece that amazed you and made you want more.

My first piece of TE was an HP 6200B, but long before that, my dad had an analog multimeter (don't recall the brand and model anymore). Spectrum analyzers still amaze me and I still don't have one.

However, what captured my imagination were the Radio Shack catalogs and the Forrest Mims Engineer's Mini Notebooks. I used to read the catalogs when I was a kid to learn about various components, jacks, plugs, switches, ICs, etc. Later, I'd look at the various products and think about how I'd build and improve them using the parts from the catalog and the circuits described in the Mini Notebooks. Since buying parts to build so many things was out of reach, I'd scribble the circuits for my DIY creations on scratch paper.

Now, I can buy all kinds of parts, but the time to build things is often out of reach. How things change.

[0culus]

I am amusing myself tonight (well, procrastinating real work) by making output pin traces on my FPGA boards into unintended transmission lines.  In reality, I'm playing with linear feedback shift registers and sending the relevant signals to the scope.

After a bit of tinkering (12 MHz clock instead of 100 MHz and using a 1x probe terminated into 50 ohms for the LFSR's serial data out), I got a much cleaner eye pattern than my prior attempt.

[tggzzz]

There are plenty for sale, none with a visible trace, and some with an entertaining price tag. The tunnel diodes are fragile (hence the strange shorting BNC) and notoriously difficult to obtain.

Be aware that the PSU is strange in the extreme: there's an off-24V switcher based around a PUJT and an SCR, and it attempts to keep a constant mean current going into the battery. They don't even switch on unless there is a working NiCd battery in them (or NiMH but watch the currents, especially for ~400ms after you plug in the mains).

Soooo... what appeared on my local CL today but a TDR 1503 that doesn't power up and, based on the photos, was probably dropped. 



Though I know fixing something like this is way above my pay grade, I am tempted to give it a go anyway, so I came back here to this post to remind myself why it is a terrible idea.

Not that it will stop me. *sigh*

Just get it.

The 1502 is squaddie proof. One of mine had a 3cm "hole" (case material still present, so welded back into place) plus longer cracks on the rear case, and still worked. ISTR the CRT is shock mounted.

They won't turn on unless there is a functional battery installed, but there is a quick test trick. The battery pack uses 4mm banana plugs/sockets, so simulate the battery with a bench PSU and flying lead with 4mm sockets on the end. Getting the correct polarity helps

Other thing to check is that the tant caps haven't spewed acid over the tracks.

[PrecisionAnalytic]

Well if those LCD conversion kits from newscope were affordable that would be an option.

Look really cool though.

I recently came across this method that seems impressive with enhancing capabilities also with math functions and views.


He references his Github files in the description too.   I've seen these going for as low as $50 brand new.

This is the first I've seen such an upgrade for a 141. Hmmm... yes... TEA...

So I thought I had to replace the CRT on the TDS-520 and have like a handful of LCD's to interface because I didn't like the fit... and why not. 

Then that changed into how can I interface the data more and display more information without the GBIP and maybe an analog signal on the circuit somewhere and process more effectively the display so I have more options.  Then I started progressing with the repairs and got the CRT working and gone was the motivation to do anything other than make a VGA output, Battery operation option, maybe the 1M option memory upgrade since just seems like a fun challenge and seems like there was one or two more mods that I'm forgetting.   Then I saw that display and am thinking why not try that on a TDS-520 to have an improved math and display capabilities... maybe even on one of the PM systems.  Eventually I'll invest in a spectrum/signal analyzer that is more modular I'm thinking even if the typical more cost effective HP's and I'll have this extra vision of enhancement as a great exercise.  Definitely on the want list if even for the HackRF or SDRplay, et.al. SDR's or module analyzer kits.

[nixiefreqq]

what?  how can you not have a spectrum analyzer?

sdr play is only 120 bucks at hro.

here are some return loss screen shots of a home brew 222 Mhz ground plane vertical with mine.  (got tired of fixing the power supply in my 141T twice a month).

[bd139]

Next restoration project arrived today.

Thing is nearly the size of my DS1054Z. It's huge. I like it. Much better than the vertical format VTVMs. Fluke 87V for scale too.



This one sort of works but is in excellent condition and was assembled very well. No sign of battery leak either. I am very impressed:



Going to take a lot more than a GDO to refurb this though. Looks like we have many possibly drifted carbon composition resistors, dirty pots, hunts horrible bastard film capacitors, waxies, selenium death rectifier etc.

Also these things are floating metal case so there's the "shall I ground it" decision to be made as well. It's not double insulated so it's about trading off the mortality risk here

I'm in heaven again 

Edit: also got another GDO in the post. The variable capacitor is much much better in this one so I'm going to do swapsies. Comedy gold though - someone got half way through refurbishing this one and gave up by the looks after a 100v electrolytic capacitor blew up in their face. FFS it has 145V+ in there 

[PA0PBZ]

Pots with balls… interesting construction!

[bd139]

Yes a bit weird indeed but they're actually a reduction drive which is pretty cool.

[med6753]

Later versions of same VTVM did ground the case and sillycon diode for power supply. Here's how it was done....   

[mnementh]

This question seems appropriate here.  Okay all, what is the one piece of TE that really got you started, the one piece that amazed you and made you want more.

For me, I was 10 years old and met a local HAM (Peter Griesbaum, WA7IFZ) who I would chat with on 10m SSB.  He heard me complain about the Heathkit 0-12 scope that I could not get to work and offered me an HP 175A scope.  The HP had the same 2 channel 40MHz vertical plug-ins and sweep delay shown in this photo (not my old scope).  I was not able to carry it by myself, had my mom drive me by a strangers house after school to pick up this beast and put in the back of her 1982 Toyota corolla.  We became very good friends and he was the one who taught me electronics.

  Woooh... tough question. I was the weird kid who took everything apart using whatever tools came to hand; butter knives, steak knives and spoons suffered greatly at my hand. Starting when I was 8 or so, no small piece of machinery was safe from me; my grandmother would pick up broken alarm clocks from wherever to give me so I'd leave the working ones in the house alone. 

When I was 10 or so, I started putting things back together... I made one working clock and another that kept time but the alarm didn't ding from the collection of parts that had survived in a shoebox in the back of my bedroom closet. When I showed grand-dad, he was dumbfounded.

All he could say was "I thought I cut the cords off of those..."    He had, but I scrounged cords elsewhere. 

   A year or two later, I'd found an old multimeter of his that the movement had frozen up on. I remember it being a Simpson 160, but that's wrong; it had a horizontal layout with movement on the left and knobs/jacks on the right, so  . By this time, the huge chest freezer in the back room of the old farmhouse was my "workbench" whenever grandmother didn't have a dog grooming appointment; one afternoon he came up behind me and watched over my shoulder without making a sound for close to an hour as I found the bit of rust that had jammed up between magnet & coil in the movement, then fiddled with a safety pin straightening the hair-fine clockprings so they didn't rub.

I didn't even realize it was him there, and I forgot about the presence behind me until I had finished adjusting the jewels so the movement was smooth and I could make it fully deflect with a puff of breath. "Good work, boy..." he said, startling me. "Oh, Bah-Bah... I'm sorry. I know you said no, but I had to try and fix it for you..." I stuttered. "Don't worry about that..." he answered. "Let's see if we can find a battery for you to test it with."

He rummaged around in one of the drawers built into the cupboard wall between the kitchen and back room an produced a 9V battery; licking the terminals, he pronounced it "Good enough..." and handed it to me. I checked the meter over one last time; stopping to fit the lens back over the movement and zero the needle before installing the battery. A bit of clear tape over the cracked lens corner that had allowed rust to get in, and I was ready to test it.

With deliberate care, double-checking the range, I set it to DC 10V range & tested the battery he'd given me; 8 1/2 ish volts looked okay.  I moved the leads and installed the battery to test the ohmmeter functions. Everything appeared in order as I shorted the leads; I was able to zero out in each range with little adjustment.

"I think it's gonna work." I finally declared, handing him the probes. He handed them back. "No... you fixed it; it's yours. How did you know how to set it up like that ?" he asked.

"I read the instructions." I smiled with no small measure of satisfaction, glancing over at the meter's storage case.

"Good... Good." he said, patting my shoulder with the faintest smile. Just then, grandmother called us to dinner.

"Come on; let's eat."

*mnemories*
*sigh* No, I don't still have it. 

[Mr. Scram]

People putting serious time limits on something, then making themselves unavailable. Lots of fun.

[PA0PBZ]

Yes a bit weird indeed but they're actually a reduction drive which is pretty cool.

Yes, I remember those from 'old' tuning knobs, the arrangement was more or less the same although the knobs didn't have a position indicating line as this VTVM clearly has, that is the weird part.

[mnementh]

Next restoration project arrived today.

Thing is nearly the size of my DS1054Z. It's huge. I like it. Much better than the vertical format VTVMs. Fluke 87V for scale too.

      This one sort of works but is in excellent condition and was assembled very well. No sign of battery leak either. I am very impressed. Going to take a lot more than a GDO to refurb this though. Looks like we have many possibly drifted carbon composition resistors, dirty pots, hunts horrible bastard film capacitors, waxies, selenium death rectifier etc.

Also these things are floating metal case so there's the "shall I ground it" decision to be made as well. It's not double insulated so it's about trading off the mortality risk here

I'm in heaven again 

Edit: also got another GDO in the post. The variable capacitor is much much better in this one so I'm going to do swapsies. Comedy gold though - someone got half way through refurbishing this one and gave up by the looks after a 100v electrolytic capacitor blew up in their face. FFS it has 145V+ in there 

Delicious! I look forward to seeing it in all its hollow-state glory once repaired and re-cal'd! 

mnem
*big fan of old-school*

[mnementh]

Yes a bit weird indeed but they're actually a reduction drive which is pretty cool.

Yes, I remember those from 'old' tuning knobs, the arrangement was more or less the same although the knobs didn't have a position indicating line as this VTVM clearly has, that is the weird part.

Yeah, those are Radidio Shack replacement knobs that were subbed later on in its life; probably when the aluminum insets fell off, making the original knobs look skeevy.

mnem
 

[mnementh]

I am amusing myself tonight (well, procrastinating real work) by making output pin traces on my FPGA boards into unintended transmission lines.  In reality, I'm playing with linear feedback shift registers and sending the relevant signals to the scope.

   After a bit of tinkering (12 MHz clock instead of 100 MHz and using a 1x probe terminated into 50 ohms for the LFSR's serial data out), I got a much cleaner eye pattern than my prior attempt.

I quite liked the first one better; much more organic-looking. Made me imagine a fluoroscope image of some alien cyborg creature's spine... or maybe one of Doc Oc's tentacles. 

mnem
Don't try to get in my head; it's dark and dangerous in here.

[mnementh]

mnem
Fortunately I keep my scales numbered, for just such an occasion...

You know it... givin' props to the greats. 

mnem

[worsthorse]

Soooo... what appeared on my local CL today but a TDR 1503 that doesn't power up and, based on the photos, was probably dropped. 



Though I know fixing something like this is way above my pay grade, I am tempted to give it a go anyway, so I came back here to this post to remind myself why it is a terrible idea.

Not that it will stop me. *sigh*

Just get it.

The 1502 is squaddie proof. One of mine had a 3cm "hole" (case material still present, so welded back into place) plus longer cracks on the rear case, and still worked. ISTR the CRT is shock mounted.

They won't turn on unless there is a functional battery installed, but there is a quick test trick. The battery pack uses 4mm banana plugs/sockets, so simulate the battery with a bench PSU and flying lead with 4mm sockets on the end. Getting the correct polarity helps

Other thing to check is that the tant caps haven't spewed acid over the tracks.

Yeah, I am going to make an offer on it today. Just figuring out how it works will be fun, even if I never get it working. Thanks for the tips. I was going to ask you about subbing an external supply for the battery as a way to test it.

[0culus]

I am amusing myself tonight (well, procrastinating real work) by making output pin traces on my FPGA boards into unintended transmission lines.  In reality, I'm playing with linear feedback shift registers and sending the relevant signals to the scope.

   After a bit of tinkering (12 MHz clock instead of 100 MHz and using a 1x probe terminated into 50 ohms for the LFSR's serial data out), I got a much cleaner eye pattern than my prior attempt.

I quite liked the first one better; much more organic-looking. Made me imagine a fluoroscope image of some alien cyborg creature's spine... or maybe one of Doc Oc's tentacles. 

mnem
Don't try to get in my head; it's dark and dangerous in here.

Haha, good point.  I agree for the most part, except I’m pretty the first one was caused by transmission line problems @ 100 MHz. The LFSR is supposed to generate a clean eye diagram like the one from last night.

Sometimes the problem child is better