Test Equipment Anonymous (TEA) group therapy thread

[Specmaster]

It must be an omen or something, I posted earlier about our christmas tree stopped lighting up, only to find that a wire had come off and then that the because I was trying to power the base up from a bench PSU, the colour wheel motor stopped working, only to finally discover after a long time the motor needed AC to run  , well today the bleeding light failed again. I now have to go Mother-in-Law's and rehome one of her 12v 20V Dichroic bulbs and strip the tree down again with all of its extra decorations, in order to fit it.

I also went out to get some more last minute shopping to ensure that we had fresh food in for the festive days and seeing photos on line of how London and Manchester was supposed to ghost towns with hardly anyone about, well....... Chelmsford was nothing at all like that, everyone and their bleeding dog seemed to out. I pulled into the local Tesco's carpark, 30 minutes to find a parking space that I could get into because the carpark was rammed with people trying to get out onto the road. Did the shopping I wanted, got into the carpark, still as rammed as it was on the way, this time it took 1hr and 25minutes before 1 had 1 wheel on the roadway again, geez. Tempers were flaring up everywhere I looked and hardly a face mask in sight.

[med6753]

Last week New York State re-instituted face masks in all public places and everyone seems to be adhering to it. I fully expect another shutdown pretty quick if numbers keep going up as they have recently. 

[mnementh]

mnem

[factory]

Update on the hp 5340A.

Found everything I need to bodge together some replacements for the expired Sprague 602D screw terminal can capacitors, I gave up on the idea of using the base from the old caps, as the terminals are alu.


First was to modify the brass M4 hex spacers I found, these were partially drilled & tapped for the #10x32 screws from the old caps. Then I used a cap clamp to hold the replacement Nichicon BT series caps in place, the leads were formed & joined together.


An offcut of alu strip was used to hold the hex spacers in place & the whole lot soldered together,  I will remember to miss out the washers next time when soldering, as I had to redrill & tap one spacer due to the solder inside.
This is the completed prototype, only another five to make. The ripple current of the three Nichicon BT caps exceeds the current rating of those puny rectifiers I fitted the other day.


David

[Martin.M]

is there anybody out there?


daddy, the anode plugs become a blue lightning?

yes son, they make connection to walhalla 










  401, ssb

[mansaxel]

EDIT: Oh, I see; the problem is my TI-8x are too smart. Just checked the supplies list; they specify the TI-30XS II as it is current, cheap ($12 at Target) and non-graphing/non-programmable. Jeebus.

Your 8x' en  indeed are way too helpful. I assume the hp-35s would be too. 

Best part with RPN is that math teachers not always grok the calculator. I had friends back in the 80s who snook programs past the usual "OK, hand in your calculator for erasing" call at the start of a test.

[Neomys Sapiens]

EDIT: Oh, I see; the problem is my TI-8x are too smart. Just checked the supplies list; they specify the TI-30XS II as it is current, cheap ($12 at Target) and non-graphing/non-programmable. Jeebus.

Your 8x' en  indeed are way too helpful. I assume the hp-35s would be too. 

Best part with RPN is that math teachers not always grok the calculator. I had friends back in the 80s who snook programs past the usual "OK, hand in your calculator for erasing" call at the start of a test.

With the HP28S, that should not be a problem. You could put a little add-on in front of a program which would say 'This is not an executable program! Please hit 'ON' to continue', which would abort the program. And I think that there is also a way to keep it in the memory without it BEING a program.

[Neomys Sapiens]

Does anyone know under which COMMERCIAL other designation the Wayne Kerr 2400L signal generator does appear and from which company? That it is also an SG-1207A/U I do know. But I am also sure that I did see in in another guise. Maybe that one was indeed the OEM.

[Vince]

Update on my newly acquired Metrix Type 920 HF generator.... making good progress ! 

I fixed it ! Yes.... was very difficult but you know how good I am. Was very difficult.... the super low output voltage was solved by.... pressing the probe tip more firmly into the output coax connector... yes, it's all it was ! It's an old style " TV " socket. The inner part is split in two halves. One of the two halves gives zero signal no matter how hard you press on it. The other half, if you press firmly, you get a good and strong signal !    LF / Modulation signal, no less than 3Vpp !!
So clearly the LF tube is not dead at all !    And the signal looks like a very nice / clean sine wave ! I thought these old tube generators output super ugly highly distorted signals, somehow... nope, looks like a beautiful sine wave, like I bought one !


So I need to replace that bastard of a coax connector. No idea where I can get one of these. Panel mount of course, screw type. The body is threaded and there is a big retaining nut at the back to hold it onto the face plate of the instrument. A pig to get to as well : it's inside the attenuator assembly, a big machined metal cylinder / housing as you can see, which is in two parts.  First need to desolder a wire, then remove the 4 studs that hold the cylindrical assembly together. This lets you pop the first half of the cylinder housing to the side. This reveals one of the two wafers of the attenuator switch. Pull the second part of the assembly, wafer comes off of its shaft, but don't I panic, it's keyed, phew.
Then you get to see the other wafer of the switch, and the output coax connector.

So since I got a super good strong signal, I proceeded to test the HF output as well. Works very well too ! Again clean nice sine wave. Tested methodically all frequency ranges, sweeping from min to max freq on every band. All bands work just fine, from the 50-150kHz up to the 15-50MHz range !
The dial is also super accurate, on every band, from end to end, top notch ! 

It's incredible, I can now generate a nice sine wave at up to 50MHz, using this ancient minimalist tube instrument... when my only sig gen so far, my old '70s Philips can go only up to 1MHz !!!   How paradoxical, how funny... and how cool ! I can do 50MHz now ! What a thrill !   

Tried modulated RF as well, works fine 

Then I checked the power supply to see how it was doing, and if the extensive rework it had endured by the previous owner, was working or not.

See schematic below.

So as you can see we have two filter caps, both 8uF, but not in parallel. They are separated by a big dropper resistor.
The cap that got replaced was the first one in line, right at the output of the rectifier tube (which has been bypassed by a solid state diode...)
It was replaced by a 47uF so A LOT bigger than the original 8uF one !  Still, it's not very big.

So DC voltage at this cap is measured at 248V for 240V nominal, good enough. ripple OK-ish at 1,1V (AVG DMM not RMS).
However the second cap I get too high of a voltage, 157 for 135 nominal. Probably because the beefy dropper resistor is supposed to be 10K but got replaced with a 8.2K !!    Going back to 10K should fix that I think. Ripple on that cap is about 45mV (AVG again, Fluke 11).

As for the LF and RF output,  if I wanted to make it perfect, here is what I could turn my attention to :

- LF / modulation signal. Its frequency is a bit off. 360Hz instead of 400. Specs say +/- 5%, so should be at least 380Hz not 360. Have a look at the schematic, what resistor or cap do you think are involved in determining that 400Hz freq ? There are a few caps in there, could be off. Resistors could be off as well... anything could be off ! 

- HF level : according to the manual, output level should not drop with frequency. Supposed to be determined solely by the attenuator setting. Of course output is not leveled on such a basic instrument, so you can expect some variations, manual says it can vary up to +/- 30%.  Problem is that I observe a lot more than that.. I get almost an order of magnitude difference between lowest and highest ! Highest attenuator setting is 100mV (but I don't know if that's peak, peak-to-peak or RMS. Manual does not say ! ). Anyhow. Strongest signal is at lowest frequencies, I get 250mVpp or so, for 100mV selected.
Then as I go higher and higher in frequency, the amplitude progressively drops more and more. At Fmax, 50MHz, the 250mVpp are loooong gone and I get only 30mVpp !!!     So I guess the most likely cause is, the HT tube is tired / weak ? It's not like that would be far fetched... the very manual itself tells you that the HF tube WILL weaken and need replacing... so I guess if it was to be expected to replace this tube even back in the day when the instrument was new... not really a surprise to have to replace it 60 years later ! 

- Modulated HF : modulation factor seems too high. Supposed to be 30% according to manual, but looks more like 50+ % to me   I guess that's determined by some resistive divider somewhere. Resistors must have drifted and modified the modulation factor. Don't know what resistors are involved though.


So that's it !  Bloody thing does work after all ! That's old French engineering for you !    Französiche Qualität ! 

So I need a replacement tube for the HF oscillator, a 6L6 tube. Then check all resistors hoping to find some that have drifted.
Then need to find a new " TV " style coax socket. Could fit a more modern BNC connector I guess, but I prefer to leave the instrument original and use an adapter instead.

Very happy with this little generator, especially for only 30 Euros ! 

[Vince]

...

[Specmaster]

mnem

Yesterday we had 106,122 new cases and 146 deaths and no restrictions in place until 28th Dec, which may be then a lockdown. Meanwhile, people are free to party, families getting together over Christmas becoming superspreaders  Hell I even have a niece flying in from Australia with her newborn son into this shitstorm to see her parents  . I, for one, will be refusing to see her, her husband and son, I just don't want to risk passing anything in either direction. Just hoping that they will be able to return home safely and avoid the virus while here

I mean, it's awful when 15 friends go out for a meal, all passed a lateral flow test before going, and then 2 days later 14 of the 15, tested positive. My oldest Son's partner's brother and mum tested positive last week, 1 day later her dad was as well.

I certainly have not slammed the door shut and become a hermit, but I do refuse to take any unnecessary risks, valuing the lives of my immediate family and mine too highly for that. 

[AVGresponding]

said i never had much use for rpn.

never said i didn't know how to use it.

Haha, Quigley...

[Specmaster]

Today is going a massively busy day for me, so I may not the chance to log and catch on all the news here, so I think I'll say this to everyone now, have yourselves a jolly good Christmas, have a great time and above all stay safe out there.

[Zucca]

I'm very happy with my SwissMicros DM42. A very good calculator, that.

That SwissMicros  calc is a piece of cake, still I can't approve it since I have my Free42 App which is serving me well.

Anyway holy shit you are right Mansa, I was bitten by the RPN spider when I was 39.
Truly no come back.

[GreyWoolfe]

Merry Christmas to all across the pond that are a day ahead of us.  Took time to prep this evening as family is coming to stay tomorrow.  Made Momma's meatballs and have the mixture for the 8 cheese stuffed shells setting up in the fridge for a traditional Italian Christmas dinner that I grew up with.  The smells in the house take me back 55 years to wonderful memories.  Even with all that is going on, I am very thankful this year.  I remained employed through covid last year and this year.  I am going through chemotherapy treatments but I am curable and not terminal.  I may have aches and pains when I get out of bed in the morning but I am grateful that I am not confined to bed.  I have gotten a good enough handle on my type 2 diabetes that I have already had my meds reduced and they will be reduced again in January when I see my Primary Care.  I am not like my son in law who is losing toes and vision because he is in denial and a dear friend who has vision and kidney issues because she can't cure her hand to mouth disease.  I am thankful for the 105 pounds that I have lost so far thanks to healthy eating and exercise which has helped dealing with the side effects of the chemo and looking forward to losing the next 90 in the coming year.  I am thankful for food in the fridge, bills paid and money left over.  I am blessed to own my home, not a house, a home that is calm, peaceful and covered in dog hair but all are welcome to come for a visit and put your feet up.  I officially become a senior citizen in 5 days, somewhat surprised that I actually made it and happy I got here.  I may not be a millionaire but I am rich beyond the measure of kings for the friends and family I have, squirrelly as they are.

It's not the big things.  It's all the little wonders and things that add up to something huge.  We all have much to be thankful for if we just take the time to reflect.  So once again, Merry Christmas and a Happy New Year.  I hope and pray that the new year will bring great joys and blessings to everyone.

[Zucca]

https://youtu.be/Rh1Z1jhk6nY?t=132

Merry XMas!

[cyclin_al]

I am from Verona Italy.
Mansa your last post went straight to my heart.

If you are planning to come down in my Verona let me know, with my dialect I can open secret doors there.

I became a man drinking "Bardolino", but the "Valpolicella Superiore" is surely a gentleman wine. Not too expensive but it makes you so so happy.
It is basically a 34401a, not for beginner for sure and about the best bang for the bucks.
Always a joy to deal with, you can't be disappointed with such a wine.

Don't get me wrong it is still a easy (to understand) wine, you do not need gloves to touch the bottle.
Just sit down, open the bottle. Let it breath at least two hours if <2019. And drink it slowly.
Close your eyes and picture something like this:



Then we could talk about "Amarone"... which is a different beast.

Ah, I am sure it is a very beautiful area.  I checked, and I have not had the pleasure to visit there.  The name sounded familiar, but I was in fact remembering Varena, Trentino.
Back in my competitive skiing days I spent a week in Predazzo, a bit further north.

I learned about that secret dialect and some amazing hospitality.  The man working at the front desk of the family-run hotel in Predazzo was also a skier.
With that in common, he directed me to some amazing culinary treats in places that I am certain the locals otherwise keep secret. 
He admitted that he never competed in his own country's race, the Marcialonga.  Unfortunately for him, that was the most lucrative time for the hotel and required him to be at work.
However, he did admit to winning 3rd place a week earlier in the Dolomitenlauf race in Austria.    That race had some world cup and olympic athletes...  I finished a few (hundreds of) places further back in the results in a field of over 5000 entries.

EDIT: I also got a hard lesson in activity at high altitudes at a smaller Lavazaloppet race in Passo Lavazè!

[Zucca]

oh I miss home now....

[tonyalbus]

Does anyone has a service manual for The Rohde & Schwarz NGPS is a precision fully programmable Dual Voltage Source
NGPS 192.0061.02
one is coming my way, but i can't find anything.

(i have sent 3db a DM, i found a post he also found one and thought he had the manual)

Great! Thanks BU for the link and also many thanks to Alan (3db) who send me all the links to the manual!
Thanks guys!
 

[med6753]

All those procrastinators (99% men) wandering the stores today like lost sheep trying to get that "perfect" gift for the SWMBO which she'll hate anyway but will smile and say thank you. But under her breath you're an asshole.   

My gifts were purchased weeks ago and only after careful understanding of what she would like.

I do have to go out later and mingle with those lost sheep in traffic to pick up the Lady Cop at the train station.

[Peter_O]

Of course one needs a calculator, and once bitten by the RPN bug, there's no turnin' back. Am planning to buy [hp] 35s to the younger children as they reach a stage in school where they need one.  I'm very happy with my SwissMicros DM42. A very good calculator, that.  nixiefreqq just helps to remind people how a proper one looks.

I had a TI 58C in the 80s which died with keyboard problems as most of the TIs. Schortly after I bought that one, HP came up with the voyager series and I envied my school friend, who got an 11C. CR2032 cells instead of akku, LCD display instead of LEDs, ...

Meanwhile I had some AOS type calculators.

Finally - that was the idea - I bought a HP35S. Fine machine, but overall it feels like a simulation of what was original those days.
So I sold it and got an used 11C "USA 2547A ...". Now I'm happy.
Get the real thing!   

[Vince]

Metrix type 920 RF generator


Just worked a bit more on it, now reporting. Had a Eureka moment that might well explain why the output amplitude was dropping progressively, and so much, as frequency increases.... I mean other than a weak RF tube.

I realized that it was most likely operator error (again... again.). Originally, since I saw bugger all signal out of this instrument, I obviously cranked the attenuator all the way up to get as large a signal as I could, and switched the probe (x1/x10 100MHz Tek probe) to x1 of course, and checked the modulation signal alone, as it was supposed to be 10 times stronger than the RF signal, and very low frequency so most likely to be strong and not affected by the x1 probe impedance...  I wanted to do all I could to maximize my chances of actually distinguishing some signal on the scope.

However once I saw that the problem came from a bad connection due to the crappy coaxial RF connector, I should then have thought of switching the probe to x10 ! But I didn't think of it !    So obviously, past a few MHz, of course the probe would quickly attenuate the signal !

So, switched it to x10 and checked again... now much better ! 

I get 200 to 300mVpp, depending on the particular frequency and particular band used. 300mVpp is pretty consistent with  a 100mV RMS... so I decided that the attenuator was labelled in RMS...
200mV is 30% down from 300mV... which is perfectly consistent with the specs of the instrument which allow for a 30% variation in amplitude.

Then I checked the highest Frequency band.... 15-50 MHz.. will I get good amplitude at 50MHz ?? YES I DO !!! about 200mV !! 
I get about 200mV all across this band [1] , lovely. So the RF tube is not even weak, 200mV is within spec ! Maybe I could get 300mV with a new tube, don't know... not gonna buy one just to confirm or deny that. It's within spec, so good enough for me...

Note [1] : well at first I did not... I had a weird, huge, narrow "spike" of amplitude somewhere around  23MHz, 400mVpp, way ABOVE spec !!  .. then it quickly went into a deeeeeep dive, down to 70mVpp or so, so way UNDER spec ! Then it settled back to 200mV for the remainder of the band.
So basically I had my 200mV or so across the band, but with this weird, localized "ripple". Looked too weird for me to think it could come from the instrument. Looked more like a probing problem, the kind of weird stuff a badly compensated probe could induce, some resonance ? So I checked the compensation of that probe, and indeed it was off. Not by much, but enough that it was obviously visible. Corrected compensation as best I could, then measured again that band.... hey presto problem fixed ! I get my 200mV all across the band, no "accident" to be seen any more !

Of course you don't have to believe me... so attached is a screenshot showing pretty much 200mV at 50MHz, max freq for the instrument. 

So basically this generator works just fine, and is healthy, does not even need new tubes ! 

All it really, really needs, is a new coax socket for the output, as the present one is just unusable, I have to keep the scope probe firmly pressed onto it to get a signal... not very practical....
So need to get a new one, as well as a BNC adapter to go with it. Hopefully Farnell or RS have that, will check.

So now I can turn my attention to the smaller details. Fix that power supply so I get 135V DC instead of 157V. Likely cause is the dropper resistor that's been replaced with 8,2K instead of 10K. Will replace that. This voltage feeds the modulation / LF tube, so might explain the issues I am having in this department, at least to some extent... modulation ratio is too high, and modulation frequency is a bit too low at 360Hz for 400Hz.

[tautech]

Merry Christmas to our TEA friends...yes its well into the early hours of Xmas day here in NZ.

https://www.timeanddate.com/worldclock/fullscreen.html?n=264

[Brumby]

Merry Christmas from the east coast of Oz .... now a bit over an hour now.

[mnementh]

   (Skip to 2:10)

Merry XMas!

    BWAHAHAHAHA!

We been RickRolled!

mnem