Test Equipment Anonymous (TEA) group therapy thread

[Vince]

Yeah not much info on the web.... Google Images found me this pic of the original / vanilla type 870, no ".2" or ".3" suffix.

Got proper looking vintage decade knobs, looks much better, consistent vintage look.
Also the meter looks a bit different, also better looking to me.

Overall I find this vanilla 870 really nice looking, I would not mind having one 

Interesting the Rochar counter sitting atop a prescaler..

Some pictures from a brochure, which lists the AS870 model, rated at 30V 3A, only a lightweight at 15kg.







David

Thanks, nice brochure 

The PSU in this brochure looks even better than the Google pic : the meter bezel is mounted behind the face plate, seated flush with it, rather than bolted in front of it.  Looks much cleaner, better integrated.
Maybe the one on Google was messed with.

I will check the phone number on the brochure and give them a call to order one ! 

[tautech]

Yeah, I've seen that wooden crap, we called it 'cap and case' in Australia.
And with the Australian heat over a hundred-odd years, the india rubber they used for insulation is now like flakey chalk... An absolute pain to join to, requiring a very gentle touch and good amounts of heatshrink to encase the old insulation and hold it all together..

I mostly came across it when we were ripping it all out to replace with modern stuff though, so no care was required there.

Oh the old black rubber TPS ! 
Horrible stuff after decades and whom knows how many buildings burnt down because of it.
Found one circuit of it in my house not long after moving in which promptly got replaced. 

Far rather have the even older steel conduit circuits even with cotton covered conduit wire inside as it's properly contained and if annoying you can easily be replaced by drawing a modern PVC covered wire.
One need take care all steel conduits are properly earth/ground strapped as the steel tube is the PE conductor too !
Typically they are all covered in some manner so occupiers have no chance of contact with it.

[M0HZH]

Not much, but adds to the testing capabilities: Fluke 50D dual digital thermometer that needs a proper clean-up.

I don't like the rigid battery mount and there's some risk of damaging the precision resistor array when you pull it out, but overall good Fluke quality.

[tggzzz]

Yeah, I've seen that wooden crap, we called it 'cap and case' in Australia.
And with the Australian heat over a hundred-odd years, the india rubber they used for insulation is now like flakey chalk... An absolute pain to join to, requiring a very gentle touch and good amounts of heatshrink to encase the old insulation and hold it all together..

I mostly came across it when we were ripping it all out to replace with modern stuff though, so no care was required there.

Oh the old black rubber TPS ! 
Horrible stuff after decades and whom knows how many buildings burnt down because of it.
Found one circuit of it in my house not long after moving in which promptly got replaced. 

Far rather have the even older steel conduit circuits even with cotton covered conduit wire inside as it's properly contained and if annoying you can easily be replaced by drawing a modern PVC covered wire.
One need take care all steel conduits are properly earth/ground strapped as the steel tube is the PE conductor too !
Typically they are all covered in some manner so occupiers have no chance of contact with it.

There was some rubber crumbly cable under the floorboards of my parents' house, going to some round-pin 13A sockets. Not connected to the supply, of course. Those sockets were more or less obsolete in the 60s.

The house certainly hadn't been rewired since the 80s, didn't have an ELCB, and the new owner discovered it has a three-phase supply, for reasons unknown. The 3 phase cable becomes visible in the basement, in a hallway cupboard, surrounded by rooms with 3ft thick stone+rubble walls. I wonder what chance there is of them having a working smartmeter there!

[tggzzz]

Back to TE, for 240V electricity supplies....

There are many devices that plug into a socket, show whether each wire is connected correctly, and whether the "earth resistance" is red/amber/green.

How is the "earth resistance" measured?

[M0HZH]

...
How is the "earth resistance" measured?

I think there are at least 4 different things that are called "earth resistance":

- ground loop impedance, which is the impedance of the ground & live wires (from substation to socket) and typically is measured by putting a load from Live to Ground and measuring voltage drop (typically tens of amps which also trips fuses/RCDs, but modern meters can do it at a few tens of mA with reasonable accuracy)
- earth resistance or the typical resistance of the soil, measured with dedicated earth resistance meters that apply DC to 2 ground spikes and use other 2 spikes for measurement.
- grounding resistance, which is (on an appliance) the resitance from plug ground pin to the appliance metallic enclosure, typically measured with specialized equipment (like a PAT tester) that work similarly to an ohmmeter for this measurement
- ground circuit resistance, which is the resistance from socket to the actual earth

[factory]

...snip...

The house certainly hadn't been rewired since the 80s, didn't have an ELCB, and the new owner discovered it has a three-phase supply, for reasons unknown. The 3 phase cable becomes visible in the basement, in a hallway cupboard, surrounded by rooms with 3ft thick stone+rubble walls. I wonder what chance there is of them having a working smartmeter there!

We have always had four separate meters, a trio of them for 3-phase (previous owner used workshop space for their business) and a separate one for the house, trouble is we couldn't get them to fit a 3-phase meter that sends the usage data to the mothership, the single one for the house wasn't a problem. It's very frustrating to get the estimated bills corrected, as at least one meter isn't currently being used, all fuses pulled from the dis-board. External cables have since been replaced with that bundled alu stuff, by the electric company.

P.S. Smart  , I really hate this word being used to describe electrical/electronic equipment, it needs to stop.

[tggzzz]

P.S. Smart  , I really hate this word being used to describe electrical/electronic equipment, it needs to stop.

I find it quite useful. For the same reason, I also find "de luxe" "designer" "exclusive" and company/brand names including "Royal" as being useful 

EDIT: add "ultimate".

[m k]

Don't forget super.

[TERRA Operative]

So, besides cleaning up the TDS540 scope (capacitor replacements ahoy!) I've been poking away at the LCDs for the THS720 scope.

The first LCD I bought from Aliexpress had a backlight that while it worked, it would not illuminate the screen... After getting a refund for a defective product, I decided to open it up and see what was going on.

Turns out the manufacturer put the foil layer on the back of the panel for a reflective type LCD, rather than leave it out as for a backlit type!
Peel off that layer and now it lights up nice and bright!

Next problem, the polarisers are oriented such that the screen is normally transparent and the pixels go dark to show the graphics. Unfortunately I need the opposite. An opaque screen and the scope provides a negative image so everything except the graphics shows up as transparent...

Problem is, the polarisers are stuck to the panel, so rotating them to invert the display is not possible. Removing them means replacing with new, and getting polarisers for FSTN or STN screens is proving difficult (I need some for some other TDS200 series scopes that have burnt polarisers...). If I use normal polarisers, the screen goes blue/yellow instead of black/white.


Is there any way to easily invert the signal going to an LCD panel like this? I have another screen on the way that looks like it will be the correct configuration, but if I can get this one working, that would be perfect.

[wkb]

Back when I was a sparky in Australia I would sometimes come across the single-pair version of that cable in older houses.

Still worked fine, and I guess the outer sheath provided pretty good shielding from interference, and gamma radiation.

Oh yes. Our house is built in 1930 and previously my VDSL2 line on a single pair, lead shielded cable gave me 100Mbits/s down. I admit I was quite flabbergasted at the time.

Wilko

[Robert763]

Back when I was a sparky in Australia I would sometimes come across the single-pair version of that cable in older houses.

Still worked fine, and I guess the outer sheath provided pretty good shielding from interference, and gamma radiation.

Oh yes. Our house is built in 1930 and previously my VDSL2 line on a single pair, lead shielded cable gave me 100Mbits/s down. I admit I was quite flabbergasted at the time.

Wilko

My previous home was built in the 70's and had aluminium telephone cables. They struggled to do 56k 

[factory]

In one of Daves recent videos there was one of those Thandar scopemaster oscilloscopes, but rebranded by Hitachi, didn't know they were rebranding British TE, oddly someone has bought it since last night, hope they didn't pay too much, $400 was a stupid price. 
https://www.ebay.com/itm/394521640580



David

[TERRA Operative]

Looks like crap. That screen would be terrible to use....

[factory]

Almost certainly, I can't remember who had one on here, the listing doesn't even give the screen size.
I guess probably not many custom bits in it, but I rather have something like a Tek THM.

In other news I've bought a test & measurement manual/book on ePay.com, only it's made of plastic, metal & components.  Postage very low, I can see this going badly wrong, will update if it makes it, or gets stolen by ePay.

David

[factory]

Found a litte box on my door step today.... a friend who works in a Telco, maintains the phone / fiber / ADSL network in the area, so every time he obsoletes some old piece of gear, or it's broken and replaced, instead of stuffing it in the trash container at work... he brings it to me. 

Not that any of it could be reused of course, but it's always cool to see how professional Telecom gear was made some decades ago, and salvage some parts.

So today he gave me some rack mount board from the mid '70s, no idea what it does of course. It looks like it's made of two symmetrical parts.

It's got cool  metal can IC's. I have got x2 SFC 2307 and x2 LM301.
Both are op-amps apparently.
Nice and original looking resistor trimmers., 4 of them, cubic shaped..



...snip...

This delightful entertainment was provided to you by ElectroFrog, Inc.

A useful databook for the Thomson CSF linear components, if you didn't already know about it;
http://www.retronik.fr/Composants/THOMSON-CSF/1982_THOMSON_CI_lineaires_professionnels.pdf

The SFC 2307 translates into an LM307 or one of it's clones, the DVM part of the HP 5326B/27B uses the LM301.

David

[factory]

A quick HP 5327B update, I found the A18 500MHz prescaler boards were defective in both of these.

There are some bias voltages for the U2 & U3 custom amplifier & schmitt trigger ICs, pin 3 of U2 should be 0.65V, pin 3 of U3 should be 0.9V (tolerance of ±0.05V for both).



The first 5327B I bought, the complete one, both ICs are dead, U2 bias is stuck at 1.8V, can adjust to 1.83V, U3 bias was 1.72V, can only adjust between 1.55V & 2.2V. The pot for the zero adjust is broken too, adjuster is snapped.



The 5327B that was missing the DVM control board (replica made a while back) & both top/bottom covers, is slightly better, U2 bias is working & can be adjusted in the range required, U3 bias is again faulty, can be adjusted between 1.32V & 2.6V.



Today I tried changing the transistor arrays, just in case they were defective and causing the odd readings, Mr Peak DCA said they were all fine, I fitted sockets as they were a pain to remove from the multilayer board, had to use bare pin sockets due to limited width between other parts. Also tried some CA3046 from a scrap Tek 24xx board, they made no difference, I didn't expect them too.

I've ordered the only 1826-0085 I can find in the world, will update if/when it turns up, hopefully can get one board working, the 1826-0084 is complete unobtainium.

Interesting there were two previous versions of the A18 prescaler board, the older ones look to have a hybrid of similar size to that used in the 5340A, no idea if it's the same part,I haven't checked.





David

[Vince]

Found a litte box on my door step today.... a friend who works in a Telco, maintains the phone / fiber / ADSL network in the area, so every time he obsoletes some old piece of gear, or it's broken and replaced, instead of stuffing it in the trash container at work... he brings it to me. 

Not that any of it could be reused of course, but it's always cool to see how professional Telecom gear was made some decades ago, and salvage some parts.

So today he gave me some rack mount board from the mid '70s, no idea what it does of course. It looks like it's made of two symmetrical parts.

It's got cool  metal can IC's. I have got x2 SFC 2307 and x2 LM301.
Both are op-amps apparently.
Nice and original looking resistor trimmers., 4 of them, cubic shaped..



...snip...

This delightful entertainment was provided to you by ElectroFrog, Inc.

A useful databook for the Thomson CSF linear components, if you didn't already know about it;
http://www.retronik.fr/Composants/THOMSON-CSF/1982_THOMSON_CI_lineaires_professionnels.pdf

The SFC 2307 translates into an LM307 or one of it's clones, the DVM part of the HP 5326B/27B uses the LM301.

David

Thanks for that ! 

No I didn't have that book... 725 pages of vintage IC goodness, can't hurt.

So these SFxxxx IC's are Thomson stuff then.... good to know.
... and they are just clones of existing ICs... why... oh why.... just brings bloat and confusion for... nothing.  They were trying to save money on licensing or what ?

[factory]

There is actually quite a lot of databooks on that website; http://www.retronik.fr/Composants/

The Thomson CSF & Sescosem are all related.
Some parts could be clones, or relabelled from other brands, same reason as always, to make them appear locally made, even if they aren't.

David

[Swainster]

Got a 'new' counter shipped over from Canada... HP 5315A with the good options (i.e. OCXO, Channel C) and the price was right. Possibly the only thing that I can complain about is that there is nothing wrong with it, so no troubleshooting fun. Fancied one of these (or its half rack relative) for ages, however by strange coincidence, there is now another one of these going on a local classifieds site, also for a pretty good price, especially considering there wouldn't be any shipping charge... absolutely no reason to get another, though... right?

[AVGresponding]

In one of Daves recent videos there was one of those Thandar scopemaster oscilloscopes, but rebranded by Hitachi, didn't know they were rebranding British TE, oddly someone has bought it since last night, hope they didn't pay too much, $400 was a stupid price. 
https://www.ebay.com/itm/394521640580



David

Looks like crap. That screen would be terrible to use....

It's effectively a bench-form scopemeter, and can run on a battery iirc. The small screen size would be how they made it for a fraction of the price of a Fluke or Tek scopemeter of the time. The $400 price is indeed ridiculous; it would probably have been not very much more than that when new.

Almost certainly, I can't remember who had one on here, the listing doesn't even give the screen size.
I guess probably not many custom bits in it, but I rather have something like a Tek THM.


David

It is Specmaster who has one, and he rather likes it, and he certainly paid way less than $400.

[Robert763]

A quick HP 5327B update, I found the A18 500MHz prescaler boards were defective in both of these.

There are some bias voltages for the U2 & U3 custom amplifier & schmitt trigger ICs, pin 3 of U2 should be 0.65V, pin 3 of U3 should be 0.9V (tolerance of ±0.05V for both).



The first 5327B I bought, the complete one, both ICs are dead, U2 bias is stuck at 1.8V, can adjust to 1.83V, U3 bias was 1.72V, can only adjust between 1.55V & 2.2V. The pot for the zero adjust is broken too, adjuster is snapped.



The 5327B that was missing the DVM control board (replica made a while back) & both top/bottom covers, is slightly better, U2 bias is working & can be adjusted in the range required, U3 bias is again faulty, can be adjusted between 1.32V & 2.6V.



Today I tried changing the transistor arrays, just in case they were defective and causing the odd readings, Mr Peak DCA said they were all fine, I fitted sockets as they were a pain to remove from the multilayer board, had to use bare pin sockets due to limited width between other parts. Also tried some CA3046 from a scrap Tek 24xx board, they made no difference, I didn't expect them too.

I've ordered the only 1826-0085 I can find in the world, will update if/when it turns up, hopefully can get one board working, the 1826-0084 is complete unobtainium.

Interesting there were two previous versions of the A18 prescaler board, the older ones look to have a hybrid of similar size to that used in the 5340A, no idea if it's the same part,I haven't checked.





David

Capacitive decoupled heatsinks on the ICs are unusual. I wonder if the heatsinks are internally connected. If so an accidental contact can cause damage?

[Vince]

There is actually quite a lot of databooks on that website; http://www.retronik.fr/Composants/

David

Thanks for the link, a little gold mine ! 

This website rings a bell... maybe you or someone else linked me to it a while back.

[TERRA Operative]

there is now another one of these going on a local classifieds site, also for a pretty good price, especially considering there wouldn't be any shipping charge... absolutely no reason to get another, though... right?

Shut up and buy it.

[factory]

A quick HP 5327B update, I found the A18 500MHz prescaler boards were defective in both of these.

There are some bias voltages for the U2 & U3 custom amplifier & schmitt trigger ICs, pin 3 of U2 should be 0.65V, pin 3 of U3 should be 0.9V (tolerance of ±0.05V for both).



The first 5327B I bought, the complete one, both ICs are dead, U2 bias is stuck at 1.8V, can adjust to 1.83V, U3 bias was 1.72V, can only adjust between 1.55V & 2.2V. The pot for the zero adjust is broken too, adjuster is snapped.

Capacitive decoupled heatsinks on the ICs are unusual. I wonder if the heatsinks are internally connected. If so an accidental contact can cause damage?

Several HP counters of this vintage use these type of ICs, in the 5327 the heatsinks of U2 to U5 are connected to the IC substrate and -5V via the tabs, top layer of the board is +5V, I found it easier to hook up the test leads to the sockets on the PCB back. There is also a warning of damage from excess heat.

I'm not the first to attempt diagnosis of one of them, two of the ICs (U2, U4) have been out at some point, as has the U1 limiter, also the broken pot was on this board.  Think I have a better chance of fixing the other.



David