Test Equipment Anonymous (TEA) group therapy thread

[TERRA Operative]

Aaanndd I just won myself a HP 8347A 100kHz - 3GHz RF amplifier for a little over 10,000yen. Should be fun to play with and help me run performance verifications on some of my other gear.

[d-el]

Successfully repaired Keithley 2001.
Several JFETs in the input section failed.

[wkb]

....

Speaking of which, I sent my Siglent arb gen back under warranty as the touch screen wasn't working and was causing random presses during operation. Not great when it randomly decides to go to full output on a sensitive circuit......
Hopefully it won't be gone too long, I kind of need it relatively regularly.

That is what you get for engaging in heresy: stepping away from the classic T&M kit to the Dark Side... 

 

[KungFuJosh]

That is what you get for engaging in heresy: stepping away from the classic T&M kit to the Dark Side... 

 

Yeah, because classic T&M kit never fails. 

[Martin72]

That reminds me of something a comedian here once said:
Not everything was better in the past; in the past, everything was earlier.

[wkb]

That is what you get for engaging in heresy: stepping away from the classic T&M kit to the Dark Side... 

 

Yeah, because classic T&M kit never fails. 

Fortunately it does fail, where would the fun in TEA be if it did not? 

Many a pleasant hour was spent poring over the supurb service manuals of the golden age of T&M 

[Robert763]

At least you can fix classic T&M kit

[tautech]

At least you can fix classic T&M kit

About your Tek P6022 current probe, can you check something for me please ?

The Tek P6022 PDF instructions lists cap A2C26 as 33pF yet the one in mine measures 235 pF at 1 kHz. 

To further confuse things the passive termination circuits in the Tek Probe circuits book for these 50t probes shows it as 270 pF.

A2C26 33pF (in the P6022 book) is in parallel with A2R37 33 Ohms marked and measured (30 in the P6022 book) and A2L26 17.5 uH

Which is right ? Did Tek attempt to mislead any copiers ?
TIA

[rdenney]

The latest acquisition of the T&M variety was an HP350D attenuator. USPS claims it was delivered last Thursday. I'm sure the are right, but I'm also sure that where they delivered it was not at my address.

Aaaaand, of course, USPS doesn't even allow one to open a tracking request until 7 days after the promised delivery data, notwithstanding that a package claimed as delivered might be far more easily found if sought after immediately. I'm going to try to reach the local postmaster today by actual telephone to see if he can at least look up the GPS location where the package actually was located when it was scanned at delivery.

All the delivery services truly do suck at one time or another, but there's something to be said for the UPS habit of photographing the item at the delivery location. USPS could learn a thing or two from that.

Rick "usually USPS doesn't report delivery when it wasn't delivered--they just lose it and go silent" Denney

[Robert763]

At least you can fix classic T&M kit

About your Tek P6022 current probe, can you check something for me please ?

The Tek P6022 PDF instructions lists cap A2C26 as 33pF yet the one in mine measures 235 pF at 1 kHz. 

To further confuse things the passive termination circuits in the Tek Probe circuits book for these 50t probes shows it as 270 pF.

A2C26 33pF (in the P6022 book) is in parallel with A2R37 33 Ohms marked and measured (30 in the P6022 book) and A2L26 17.5 uH

Which is right ? Did Tek attempt to mislead any copiers ?
TIA

I'll dig mine out later and have a look. How are you measuring it? Measuring in circuit or out? Has it nay markings?

[Robert763]

Tea arrived. I was wondering how they were going to deliver the lot I won. Cost of delivery, £90, indicated a pallet but there seemed to be too much kit to fit a pallet.
They went vertical:

That is about 6ft high  Very little packing. Some stuff in boxes but basically everything just piled in 
Fortunatly all the important stuff seems undamaged.
A few bits that were not clear in the picture included a NI USB to 4 serial port interface. This box costs over £1200 from Farnell.  Who pays that much for effectively a USB hub and 4 FTDI chips? There is over £15,000 (current new price) of NI kit in there.
I'm scrapping out some of the useless lab kit before I start playing with the toys...

[tautech]

At least you can fix classic T&M kit

About your Tek P6022 current probe, can you check something for me please ?

The Tek P6022 PDF instructions lists cap A2C26 as 33pF yet the one in mine measures 235 pF at 1 kHz. 

To further confuse things the passive termination circuits in the Tek Probe circuits book for these 50t probes shows it as 270 pF.

A2C26 33pF (in the P6022 book) is in parallel with A2R37 33 Ohms marked and measured (30 in the P6022 book) and A2L26 17.5 uH

Which is right ? Did Tek attempt to mislead any copiers ?
TIA

How are you measuring it? Measuring in circuit or out? Has it nay markings?

You have a bit on with your pallet of gear so no hurry.

Measured after removal with ST42 smart tweezers in C mode.
Hollow tubular cap ~9mm long marked brown, brown, red, yellow, brown, green.

I found a possible replacement amongst some scavenged stuff, orange, orange, white, black, green which should be 33 pF and measures 38 pF @ 10kHz

I saw some weird current probe results so went investigating and wound up testing termination components and found these weird cap values......235 pF when it should be 33 pF.
These are old school hollow tubular caps 600V rated and I struggle to imagine how they might have been damaged in a current probe termination.

[Robert763]

So in my compensation box there is a capacitor the same as yours see below.
Ignoring the brown  mark on the end I make it 240pF which ties with your measurements. 
Maybe there was a change that didn't make it to the manual.
It's only in circuit for the 1mA/V range so switching range should allow it to be ruled out.

Robert.

[tautech]

So in my compensation box there is a capacitor the same as yours see below.
Ignoring the brown  mark on the end I make it 240pF which ties with your measurements. 
Maybe there was a change that didn't make it to the manual.
It's only in circuit for the 1mA/V range so switching range should allow it to be ruled out.

Robert.

Mystery solved, thanks very much !

[Zephyr]

At least you can fix classic T&M kit

Tek, at least, made that rather difficult with their tendency to make their own custom ICs and then sprinkle them around inside their gear in the oddest places (a custom IC to light up the probe multiplier LEDs on the Tek 485 'scope, for example. It's just a resistor in the probe indicator circuit, why not just use a regular comparator!).

Bill

[Robert763]

I wonder if the current bidders on these two Rubidium standards have noticed the the FRK rubidiums have been removed?
https://auctions.ramco.uk/auctions/9456/ramco-11453/lot-details/2565ce1a-9f23-4540-9dbb-b384009214d4
https://auctions.ramco.uk/auctions/9456/ramco-11453/lot-details/a7afc95f-c6ac-405b-976a-b3840092153e

They look like a lot of scrap.

[Peter_O]

I always wanted an old school linear dual channel PSU and identified the TTi ones to be kind of classic.
Now a TTi Thurlby Thandar Instruments PL330QMD has found a way into my collection.
Believing the transformer stickers it is built in 1998 which makes it a later one.



I really like these big LED displays. In reality they shine evenly bright with a rich red.

The PSU is relatively clean, especially inside, but definitely could use some front cleaning.
(Any hint how to remove the "1." and "2." writings? IPA or benzine didn't work.)



The PSU shows basic function. It delivers 3A without magic smoke. It reaches the 32V maximum voltage.

But there are some odds. I.e. in CC mode the voltage regulation is very slow. It slowly pumps between 0V and the right voltage.
And when changing the load resistance in CV mode, the ampmeter sometimes is normally fast, but sometimes it creeps to the right value within a minute or so.

Definitely a candidate to dig in and repair. I might start a thread. 

[AVGresponding]

Might be as simple as a bad connection for the sense wire(s).

Don't have a good suggestion for the ink, if it's seeped into the plastic it might not come back out... you could try acetone or brake cleaner, but test it on a non-visible bit of plastic first as it can be very aggressive as a solvent

[themadhippy]

Any hint how to remove the "1." and "2." writings? IPA or benzine didn't work

if  a chemical attack fails maybe some fine sandpaper

[Robert763]

A "Magic Eraser" cleaning sponge can work well on this sort of mark. They are made from melamine thermosetting plastic foam. Use it wet with solvent. I'd start with IPA. Lots of light rubbing is better than hard scrubbing.
They are available as expensive "brand name" items or much cheaper as unbranded or bargain brand items.
If you have to use a more agressive solvent start with a 70-30% mix of IPA and acetone. The front lanels on these are a reverse printed plastic and are pretty solvent resistant. Keep it away from the edges were it can get to the adhesive and don't leave pools of solvent to soak on the surface.

[watchmaker]

VNA vs Spectrum Analyzer with Tracking Gen for amateur

I doubt I will ever become a threat to the RF community.  I purchased the VNA (HP 8712ET) before I really thought thru my goals.  Then I found the Anritsu MS2670A which is a custom variant of the MS2664/2668 heterodyne family; with an NSN (Naval Stock No.) tag.

I now realize the Anritsu suits my needs best since it has a tracking generator has a range of 100 Hz to 1.8 gHz.  I am convinced (via comparisons with my scope and SDG1022x) that the Anritsu is accurate "enough".  I doubt I will ever get past standard radio frequencies.  No cell, no wifi, etc.

BUT, are there reasons I may regret selling it?  Other than Smith Charts, can it do anything the SA can do?  I paid little money for either and so there is no need to sell the VNA (other than shelf space).  I should add I have a Digilent AD3.  But I always had a thing for precision stuff in good condition; much to my wife's chagrin.

THANKS!

Price is what you pay; value is what you get.  W.B.

[44kgk1lkf6u]

Do you have a return loss bridge or does the spectrum analyzer have 1 built in?

A scalar network analyzer can't measure phase.  So it can't transform the measurement into the time domain.  And since there is no way of knowing the magnitude of the difference of 2 numbers based on their magnitudes, it can't compensate for the cables either.

[vk6zgo]

Do you have a return loss bridge or does the spectrum analyzer have 1 built in?

A scalar network analyzer can't measure phase.  So it can't transform the measurement into the time domain.  And since there is no way of knowing the magnitude of the difference of 2 numbers based on their magnitudes, it can't compensate for the cables either.

Substitution allows for cable characteristics, as the things that show up with a VNA also have secondary effects that are manifested in the Scalar realm.
Much of the "day to day" stuff done in the past involved measurement of return loss in dB.

Back in the day, VNAs were quite expensive, & a lot of good work was done with Scalar Network Analysers like the R&S  SWOB Polyskop.

I have but a poor nanovna & if I had a tracking generator to go with my 7L12 Tek Spec An plugin, I would probably use the latter more often.

Yes, it is nice to have a VNA & silly to not keep it, but I would not discount the versatility of Scalar Network Analysers.

[44kgk1lkf6u]

Substitution allows for cable characteristics, as the things that show up with a VNA also have secondary effects that are manifested in the Scalar realm.

I am interested.  Please elaborate.

[watchmaker]

Do you have a return loss bridge or does the spectrum analyzer have 1 built in?

A scalar network analyzer can't measure phase.  So it can't transform the measurement into the time domain.  And since there is no way of knowing the magnitude of the difference of 2 numbers based on their magnitudes, it can't compensate for the cables either.

Is that the same as normalization where I connect the TG and RF input, set my freqs and push the normalization button and then add my DUT  I am trying to find a manual on Anritsu TGs to understand their approach, but no joy.  I do get filter responses which agree with expected (as far as I can tell).