Test Equipment Anonymous (TEA) group therapy thread

[worsthorse]

Finally some time for TEA indulgence.  At a hamfest a few months back, I found a B+K 501A curve tracer. The seller had no idea if it worked and gave it to me for twenty-five bucks.  I put it on the shelf when I got home, lured by the siren call of some of the more complex gear in the repair queue. I pulled it out tonight to see if it worked (and if I could remember how to set up a scope in XY mode)...



[snip}

I am going to snuggle with the manual and get reacquainted with how these things work. After I do that, I will decide if I want to tear it completely down, and check to see if all the parts are still in tolerance given that the caps and carbon comp resistors are, I dunno, forty-five years old. 

Oh, one neat feature... the 501A has two sets of sockets so you can match transistors, whether of the same type or complementary.  And the sweep voltage goes up to 100V, so it will handle power transistors.

That was a very good price, I paid quite a lot more for my Heathkit IT-1121.
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1766804/#msg1766804

Very handy for testing/comparing old obsolete components to find more readily available ones, also great for checking unusual parts such as tunnel diodes.

David

P.S. I'm curious to see what is inside the Leader LTC-905, which is the only other small vintage curve tracer I've seen for sale in the UK.

Leader LTC-905 photo as per requested 

Just catching up again, thanks for those pictures of the Leader curve tracer, looks much easier to service the PCB than with the Grief-kit, I really ought to check how many components are past their use by date or drifted out of tolerance.

David

I have it open on my bench, waiting for capacitors to arrive from mouser. And yes, it is pretty easy to service: single-sided PCB, silkscreened component designators, etc. One weird thing, the user manual BOM doesn't include most of the capacitors, just the electrolytics.

I was able to get the step voltage output better than spec using the manual calibration procedure, even with the wonky carbon trimmer pots. But there's some noise and a bit of distortion in a couple of other places that I think the capacitor change out will fix.  It ain't a 576 but then I don't need a 576... 

[syau]

I have another question for the TEA hivemind.

I want to buy/build a shielded low-ish Thermal EMF cable with banana jacks at each end. Nothing to volt-nuttery, but something better than a couple multimeter leads.
I have seen Pomona make individual low EMF leads, but nothing as a single shielded cable (that I can see).

Anyone got any suggestions?

Use a triaxial cable (if not metrology grade, maybe 1553B cable), or a nice flexible shielded, twisted pair like MIL-W-22759. You can select from bare, tinned, or silver-coated wire and various insulation variants.
Add good plugs and give it a try.

Good banana jack with low emf cost a fortune, the cheapest way is using some shielded network cable hook up to the binding posts. Every time just trim the open end a little bit will get you fresh copper. 

[worsthorse]

The 485 cover is off.  Not quite ready to tackle the capacitor redo. First I have to figure out problems with the channel one vertical position pot and the channel push buttons (CH1 CH2 ALT CHOP ADD).  So, Tekheads here are my questions:

The CH1 vertical position pot is hard to turn. There's no visible damage to the front of the 485. This is one of the pots that is mounted halfway back in the box, so it has a shaft coupling. From what I can see inside the box, there's no damage.  Any idea why the pot would be resist turning through its whole range of motion?

The channel selection buttons, which are deep in the middle of the box, seem to have aa problem. They all latch but sometimes need an extra push to cause the mode to switch.  Again, no visible damage to the buttons or the front panel around them.  Is this a switch cleaning issue? I haven't dug into the schematics yet?

Asking because I am in touch with the ebay seller, as it was listed in working order and I can probably get a price adjustment.  I'd like to settle that before I start taking it apart, which as you all know, is not the simplest task.


-

[beanflying]

In Other News...

The new MB is in the box and cables made up; it POSTs and boots to BIOS. BUT... The damn USB ports are now all flaky as hell; mouse freezes up and keyboard acting like there’s a key pressed and held most of he time.    This after it performed flawlessly on the bench for more than an hour while I puttered around setting up the fans and CPU pump and stuff.    It took half an hour of unplugging/replugging mouse/KB to complete a BIOS update... I can’t even get into the “Tweak” submenu to tune the OC.    Done all the usual troubleshooting; new mouse/KB, different PSU...

I’m on the road doing family stuff; when we get home I’ll  strip it down to RAM & CPU... again.

mnem
   Okay... I think I’ve bled enough for this bleeding edge.

It was the effing nvme/M.2 drives. Either slot occupied makes it do this. 

Oklay... must be some conflict on the PCIE bus.     I wonder what stupid setting they left on by default that I missed the first time I read TFM.

mnem
Nice pants.

The B450 Manual  I have specifies which SATA ports are blocked when you plug in NVMe drives. Even with two NVMe's on mine I still have a couple of free SATA connections.

[TERRA Operative]

For the cable, I would go after something like this:

https://www.ebay.com/itm/273799295024

For the Banana plugs I would take these:
MC (MultiContact) Stäubli 4mm banana plugs
Example:
https://www.ebay.com/itm/202689458387

the hollow version of them:
https://au.rs-online.com/web/p/banana-plugs-connectors/0531453/

Looks doable. I guess any decent shielded PTFE cable would do the trick?

Are those banana plugs known to be good, or can I use any decent quality plug I like?

CAT6 network cables are cheap and working well.

I actually have a roll of Cat6A cable here that I wired my house in, but it is solid so not very flexible at all...
Maybe I should look for some stranded stuff. Is there any particular wiring method (Like keep the pairs connected only to themselves, or connect the white wires together, and the coloured wires together)?

Use a triaxial cable (if not metrology grade, maybe 1553B cable), or a nice flexible shielded, twisted pair like MIL-W-22759. You can select from bare, tinned, or silver-coated wire and various insulation variants.
Add good plugs and give it a try.

I'd have to see if I can get that stuff in Japan, is it expensive? I just need it 'good enough' for my voltage and current standards so the last few digits are as stable as possible and free from outside influence etc.
Triax is interesting, I've never worked with it. I'll have to see where I can source it by the meter here, and figure out how to terminate it...

Good banana jack with low emf cost a fortune, the cheapest way is using some shielded network cable hook up to the binding posts. Every time just trim the open end a little bit will get you fresh copper. 

Some of my gear only has shielded banana sockets (like my 34461A), hence wanting to use banana plugs, unless there is another option?
Do you have any links to the low EMF banana jacks?

[beanflying]

For the cable, I would go after something like this:

https://www.ebay.com/itm/273799295024

For the Banana plugs I would take these:
MC (MultiContact) Stäubli 4mm banana plugs
Example:
https://www.ebay.com/itm/202689458387

the hollow version of them:

Looks doable. I guess any decent shielded PTFE cable would do the trick?

Are those banana plugs known to be good, or can I use any decent quality plug I like?

CAT6 network cables are cheap and working well.

I actually have a roll of Cat6A cable here that I wired my house in, but it is solid so not very flexible at all...
Maybe I should look for some stranded stuff. Is there any particular wiring method (Like keep the pairs connected only to themselves, or connect the white wires together, and the coloured wires together)?

Use a triaxial cable (if not metrology grade, maybe 1553B cable), or a nice flexible shielded, twisted pair like MIL-W-22759. You can select from bare, tinned, or silver-coated wire and various insulation variants.
Add good plugs and give it a try.

I'd have to see if I can get that stuff in Japan, is it expensive? I just need it 'good enough' for my voltage and current standards so the last few digits are as stable as possible and free from outside influence etc.
Triax is interesting, I've never worked with it. I'll have to see where I can source it by the meter here, and figure out how to terminate it...

Good banana jack with low emf cost a fortune, the cheapest way is using some shielded network cable hook up to the binding posts. Every time just trim the open end a little bit will get you fresh copper. 

Some of my gear only has shielded banana sockets (like my 34461A), hence wanting to use banana plugs, unless there is another option?
Do you have any links to the low EMF banana jacks?

I need to grab some 5 or 6 core Shielded most likely Teflon 1kV rated cable if you come across any. I need to build an external box for my 740B Diff Voltmeter.

Low EMF usual suspects are Pamona, Hirschman (I know they have shrouded) Tellurium Copper

[mnementh]

In Other News...

The new MB is in the box and cables made up; it POSTs and boots to BIOS. BUT... The damn USB ports are now all flaky as hell; mouse freezes up and keyboard acting like there’s a key pressed and held most of he time.    This after it performed flawlessly on the bench for more than an hour while I puttered around setting up the fans and CPU pump and stuff.    It took half an hour of unplugging/replugging mouse/KB to complete a BIOS update... I can’t even get into the “Tweak” submenu to tune the OC.    Done all the usual troubleshooting; new mouse/KB, different PSU...

I’m on the road doing family stuff; when we get home I’ll  strip it down to RAM & CPU... again.

mnem
   Okay... I think I’ve bled enough for this bleeding edge.

It was the effing nvme/M.2 drives. Either slot occupied makes it do this.  Oklay... must be some conflict on the PCIE bus.     I wonder what stupid setting they left on by default that I missed the first time I read TFM.

mnem
Nice pants.

The B450 Manual  I have specifies which SATA ports are blocked when you plug in NVMe drives. Even with two NVMe's on mine I still have a couple of free SATA connections.

Yeaaahhh. NO. SEE ABOVE. I have yet to install ANY SATA drive in this machine.

It appears the BIOS on these boards places ALL nvme management under the NVME RAID Management console. You can manage SATA drives from the regular settings menu; but to manage even a SINGLE nvme drive you have to ENABLE the nvme RAID Controller and force it to rescan the physical drives. Until you do, it continues to be this kind of totally flaky whenever there's a nvme drive attached (even though it auto-detects the damned things and shows them right on the dashboard), and of COURSE the nvme RAID Controller is turned OFF by default. 

I only found this out by accident while noodling around in the BIOS; NONE of this "nvme RAID Controller" config is outlined in TFM; it's not even MENTIONED.  I think this manual is primarily drafted from the X470 manual with very little modification.

mnem
*trailblazing* 

[syau]

Good banana jack with low emf cost a fortune, the cheapest way is using some shielded network cable hook up to the binding posts. Every time just trim the open end a little bit will get you fresh copper. 

Some of my gear only has shielded banana sockets (like my 34461A), hence wanting to use banana plugs, unless there is another option?
Do you have any links to the low EMF banana jacks?

Get some cotton bud, cut it into halve, push the copper wire through the hollow plastic stem and wrap it on top of the cotton will make a good connection on shielded jack. 

[TERRA Operative]

Good banana jack with low emf cost a fortune, the cheapest way is using some shielded network cable hook up to the binding posts. Every time just trim the open end a little bit will get you fresh copper. 

Some of my gear only has shielded banana sockets (like my 34461A), hence wanting to use banana plugs, unless there is another option?
Do you have any links to the low EMF banana jacks?

Get some cotton bud, cut it into halve, push the copper wire through the hollow plastic stem and wrap it on top of the cotton will make a good connection on shielded jack. 

Bodge it 'till it works, I like it.

[mnementh]

Bitch Lives.

mnem
I'm goin' to bed.

[TERRA Operative]

Hmmm, what is the consensus on a bodge for these low Temp EMF leads if I were to use the premade Pomona ones with the banana jacks, but then slip some tinned copper braid over both of them and then some nylon braid with heatshrink at each end to keep it neat, then break out the braid to a banana jack for guard connection?

I got both types of braid from Akihabara today for only a few $$$.

Reckon it's enough of a bodge to maybe work?

[Specmaster]

Ooh headshot. Yes we are indeed 

When talking of redheads you should be wearing a tin hat to take care of the odd headshot, but women in general can be pretty deadly to both your heart and pocket, law has their back over yours [emoji83]

Sent from my POT-LX1 using Tapatalk

[beanflying]

Hmmm, what is the consensus on a bodge for these low Temp EMF leads if I were to use the premade Pomona ones with the banana jacks, but then slip some tinned copper braid over both of them and then some nylon braid with heatshrink at each end to keep it neat, then break out the braid to a banana jack for guard connection?

I got both types of braid from Akihabara today for only a few $$$.

Reckon it's enough of a bodge to maybe work?

The biggest issue is the '1kV' insulation on the cable and can it be believed initially and going forward. Tinned copper braid is fairly goo btw I have used it on pesky CNC leads for shielding. Low EMF is only Voltnut feel good for most but when you get to counting sub 10PPM or worse sub PPM it becomes needed.

[VK5RC]

How hard can it be to modify a 5221 (usually counts using 60Hz line freq as reference) to take any frequency line input. The 5221 has an option to do that - the board is a simple Xtal and 7 series divider.
I build the Xtal and divider before I RTFM, - the mod also needs a new HP only ASIC!  FFS.
So how hard can it be to emulate the 17Vpp AC the unit uses!
So I get a 6MHz Xtal, rebuild the divider, I need some higher volts - the only convenient way was to rectify the 17V - gives 8.5V - not enough to drive the gate (of course!) so I bodge in a ICL7660 voltage doubler.
The unit can handle extra digits, so I thought I would push it as far as I could. By pulling off a 100x faster clock, ie 6kHz, not 60Hz, the unit now counts reliably to 9MHz, needing about 100mVpp min to count. A new switch at the back , switches in the 100x 'feature'. I have left a note inside about how to undo it.
It can now come off the 'repair stack'
I need psychotherapy though!
Rob

[TERRA Operative]

The biggest issue is the '1kV' insulation on the cable and can it be believed initially and going forward. Tinned copper braid is fairly goo btw I have used it on pesky CNC leads for shielding. Low EMF is only Voltnut feel good for most but when you get to counting sub 10PPM or worse sub PPM it becomes needed.

Yeah true, I would usually be using it up to 100v, except when I crack out the 332D once the restoration is complete..

Only one way to find out though, bite your tongue, close your eyes and flick the switch!

[tggzzz]

The CH1 vertical position pot is hard to turn. There's no visible damage to the front of the 485. This is one of the pots that is mounted halfway back in the box, so it has a shaft coupling. From what I can see inside the box, there's no damage.  Any idea why the pot would be resist turning through its whole range of motion?

I can't remember the details, but I would conservatively start by investigating mechanical stickyness outside the pot. So I'd divide and conquer the mechanical path, and   see   feel what happens.

The channel selection buttons, which are deep in the middle of the box, seem to have aa problem. They all latch but sometimes need an extra push to cause the mode to switch.  Again, no visible damage to the buttons or the front panel around them.  Is this a switch cleaning issue? I haven't dug into the schematics yet?

Solved for a 475: https://www.eevblog.com/forum/repair/renovating-an-early-tektronix-475-oscilloscope-a-few-random-hints-and-tips/msg1438311/#msg1438311

[bd139]

How hard can it be to modify a 5221 (usually counts using 60Hz line freq as reference) to take any frequency line input. The 5221 has an option to do that - the board is a simple Xtal and 7 series divider.
I build the Xtal and divider before I RTFM, - the mod also needs a new HP only ASIC!  FFS.
So how hard can it be to emulate the 17Vpp AC the unit uses!
So I get a 6MHz Xtal, rebuild the divider, I need some higher volts - the only convenient way was to rectify the 17V - gives 8.5V - not enough to drive the gate (of course!) so I bodge in a ICL7660 voltage doubler.
The unit can handle extra digits, so I thought I would push it as far as I could. By pulling off a 100x faster clock, ie 6kHz, not 60Hz, the unit now counts reliably to 9MHz, needing about 100mVpp min to count. A new switch at the back , switches in the 100x 'feature'. I have left a note inside about how to undo it.
It can now come off the 'repair stack'
I need psychotherapy though!
Rob

Nice work on the mod 

[BU508A]

Hmmm, what is the consensus on a bodge for these low Temp EMF leads if I were to use the premade Pomona ones with the banana jacks, but then slip some tinned copper braid over both of them and then some nylon braid with heatshrink at each end to keep it neat, then break out the braid to a banana jack for guard connection?

I got both types of braid from Akihabara today for only a few $$$.

Reckon it's enough of a bodge to maybe work?

If you are really going after low thermal EMF then avoid any plating, tinning etc. Use just pure copper. Nothing else. That is the advise you'll get, when you are asking in the Metrology section of the eevblog forum.

Examples:
https://www.eevblog.com/forum/metrology/possible-low-thermal-emf-connectors/

https://www.eevblog.com/forum/metrology/diy-low-emf-cable-and-connectors/


And just for the records: those MultiContact Stäubli plugs I've mentioned are high quality ones.
They are playing in the same league (or even better) than Pomona.
Sadly, years ago they stopped producing the real low thermal emf binding posts and banana plugs.

Edit:
Link to their website, if you are looking for specs etc.
https://ec.staubli.com/products/productline/6

[BU508A]

The biggest issue is the '1kV' insulation on the cable and can it be believed initially and going forward. Tinned copper braid is fairly goo btw I have used it on pesky CNC leads for shielding. Low EMF is only Voltnut feel good for most but when you get to counting sub 10PPM or worse sub PPM it becomes needed.

Maybe RG316U can be used for this. the inner insulation is PTFE and should widthstand 1000V without any hassle.

https://www.koax24.de/en/product-info/coaxial-cable/koaxialkabel-50-ohm/24-32-mm-size2/rg316-u.html

[Kosmic]

Man i'm definitly down with TEA 

There's a Datron 1281 multimeter (8.5 digits) on ebay this morning for only 3k. Andddd I was actually considering buying it for at least 30 seconds.

https://rover.ebay.com/rover/0/e11021.m43.l1120/7?euid=6fc69918822448c9b1f517aa42b03c0b&bu=43194197782&ut=RU&loc=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F293177550373&sojTags=bu=bu,ut=ut

[BU508A]

Man i'm definitly down with TEA 

There's a Datron 1281 multimeter (8.5 digits) on ebay this morning for only 3k. Andddd I was actually considering buying it for at least 30 seconds.

Probably you are in a similar position as Mr. Data was. 

[Kosmic]

 

[med6753]

I'm knee deep into the 485 trying to track down the +15V short. I pulled the Sweep Board and the short is still there. The +15V on the Sweep board reads normal so that rules out the +13V derived on that board thru R965 and C911. The short is somewhere on the main supply board and so far been unsuccessful in finding the source. I've tried isolating the board as much as possible and no dice. So next step is pulling that board completely off. I am liking the modular construction of this scope. Much better design than the 465/475.

Now going in chest deep. 

[worsthorse]

The CH1 vertical position pot is hard to turn. There's no visible damage to the front of the 485. This is one of the pots that is mounted halfway back in the box, so it has a shaft coupling. From what I can see inside the box, there's no damage.  Any idea why the pot would be resist turning through its whole range of motion?

I can't remember the details, but I would conservatively start by investigating mechanical stickyness outside the pot. So I'd divide and conquer the mechanical path, and   see   feel what happens.

The channel selection buttons, which are deep in the middle of the box, seem to have aa problem. They all latch but sometimes need an extra push to cause the mode to switch.  Again, no visible damage to the buttons or the front panel around them.  Is this a switch cleaning issue? I haven't dug into the schematics yet?

Solved for a 475: https://www.eevblog.com/forum/repair/renovating-an-early-tektronix-475-oscilloscope-a-few-random-hints-and-tips/msg1438311/#msg1438311

Thanks... I hadn't considered looking for other tek scope threads for ideas. I will deal with the pots and switches when I take boards out for the recap.

[med6753]

485 supply board on the bench. The short is definitely on this board. Closing in...