Test Equipment Anonymous (TEA) group therapy thread

[med6753]

Attached my findings here.

@med6753: can you take a good hi-res picture of your 547 in a similar style like the ones shown below?

Edit: The pictures of the scopes are taken from this site: https://w140.com/tekwiki/wiki/Main_Page

Found a better picture of the Sisyphus:

I don't have a hi-res camera. Just this crappy Nokia 925 phone.

It really doesn't matter if the pix is a 535, 545, or 547. They all look similar.

I do really like the 535 because of all those nice red knobs. 

Fine with me. 

[AaronLee]

I do really like the 535 because of all those nice red knobs. 

Oh, yes, lots of red knobs with the black secondary knob behind it. I just love that look. The first Tek scope had all black knobs though. Lots of other manufacturers' scopes from the era have a similar look to the Tek scopes with red/black knobs. Does anyone know the history of that? Which manufacturer was first to use red/black knobs on their scopes, and did they get that idea from other test equipment already in existence with that color scheme, or was it first done on scopes?

[med6753]

So earlier this evening I give the Type 547 a routine power up, as I've done several times over the past few days. Basically part of my burn in and test process. Only this time I'm greeted with no trace and the smell of something getting hot. Not again!  Quickly shut it down. Yep, the +100V indicating an overload. I think this time I got it shut down before the 6080 regulator tube destroyed itself. Did a DC resistance check of the +100V bus and no short indicated.  Same sort of problem seen several times before.

My initial temptation was to get out the BFH and start swinging. This has been one frustrating restoration. After I cooled down I decided for the time being, at least a week or perhaps more, to put it aside. It's obvious I'm going to have to put the external supply back on to troubleshoot this latest fail. But there's other things I want to do like build up the 2nd scope cart. So button it back up and into the corner of bench 2. And let it mock me, I'll just ignore it.     

Well, not everything is bad, some good came from it, you can now discount those two bare wires coming into contact with each other as being the problem.

True, but it's a small consolation after all the hours I put into it to get it to come up, and stay up, for many hours.

Welcome to the world of fixing obscure faults in CRO's. 
Learnt a lot but never made much dosh doing it such was the time spent of some of them. 

Still, I well get your passion for such things as the old classic Teks. 

I fully accept that when dealing with 50 - 60 year old equipment you are going to run into numerous issues. You've seen on some of my prior restorations several set backs and frustrating moments but eventually they get sorted out. This Type 547 however is proving to be a real challenge. This is at least the 4th time I've taken one step forward and two steps back. 

Edit.....Later today I'll forget all about my troubles. Lady Cop will be coming up this afternoon. 

[FransW]

HR only does the work for one level above the.
They, HR, do the dirty work with elephant skin.

[xrunner]

... Only this time I'm greeted with no trace and the smell of something getting hot. Not again!

Enabler mode: ON - you need an IR camera ... 

[nixiefreqq]

... Only this time I'm greeted with no trace and the smell of something getting hot. Not again!

Enabler mode: ON - you need an IR camera ... 

that is an excellent suggestion.

but for entertainment value the BFH would be better.

[Zucca]

https://portland.craigslist.org/mlt/ele/d/portland-tektronix-529-oscilloscope/7362452602.html

Is craigs horror list still a thing in USA? I had some success in evil bay.com lately but everybody is telling me to go to facebook marketplace.

I miss my ebaykleineanzeige from Germany......

[Specmaster]

@bd139 You asked what it is like as a multimeter, well as you can see from the photos, it does acquit itself pretty well if you can live with it limited voltage capability of 250V, which should be fine for most solid state projects. As with all of these types of devices that I have looked at, some compromises have to be made, the voltages are always measured using the probe on channel 1 and has settings for X1 and X10 probes.

There is an extensive onboard help menu and will present you with error messages when you go into overload situations. It even has a continuity setting, handy that, I often find myself using that option on meters.

I think these photos are pretty much self-explanatory, but sadly because this unit is in such perfect condition, the screen makes it almost impossible to get a really clear photo as it is angled upwards and as such things get reflected on it and these are not normally detected by the naked eye, but a camera just seems to amplify the problem.

[Zucca]

Fixed for you.

[ch_scr]

Here we have first tests - in principle it is working. We can see gain going up around 900MHz, and resonance might come after that - future measurement might tell.
But principle works 
Gain:

Loading with 1.2pF is not stellar but still better than usual probe:

Ok, now I had time for a play around. The DG-Mosfet I used are of the "integrated bias network" type. Vishay-Telefunken calls that "MOSMIC". No need for a 10Meg resistor with these. I found a few NOS BF1009 and used these at first. In my "recycled" container especially for DGMOS some S886T turned up, I did keep an eye out for these in the RF input cans on VCR, TV/SAT receivers, etc.
Finally time to shine, it's not hoarding if you end up using some 
Also on my board the gate 2 that sets the gain is not tied to drain but to an voltage set by a 431 type "zener replacement" reference, partially because the BF1009 has a V-G2 of 6V and a V-D of 9V, partially because I wanted the option to see the influence on gain. The reduced attenuation above 900MHz is caused by passive coupling through the circuit and is even there without powering it (sadly no picture of that) - an output filter might remedy that.
On all the pictures only the red line is relevant, the S11 also measures its termination into the T and the loading from that. Loading in all cases is ~1.2-1.3pF
BF1009 G2@ 5.5V

BF1009 G2@5V

BF1009 G2@6.3V

S886T with G2@6.3V and long output cable (these tolerate 9V@G2)

[bd139]

@bd139 You asked what it is like as a multimeter, well as you can see from the photos, it does acquit itself pretty well if you can live with it limited voltage capability of 250V, which should be fine for most solid state projects. As with all of these types of devices that I have looked at, some compromises have to be made, the voltages are always measured using the probe on channel 1 and has settings for X1 and X10 probes.

There is an extensive onboard help menu and will present you with error messages when you go into overload situations. It even has a continuity setting, handy that, I often find myself using that option on meters.

I think these photos are pretty much self-explanatory, but sadly because this unit is in such perfect condition, the screen makes it almost impossible to get a really clear photo as it is angled upwards and as such things get reflected on it and these are not normally detected by the naked eye, but a camera just seems to amplify the problem.

Thanks for this. Much appreciated. That’s really neat actually. I am impressed 

[med6753]

https://portland.craigslist.org/mlt/ele/d/portland-tektronix-529-oscilloscope/7362452602.html

Is craigs horror list still a thing in USA? I had some success in evil bay.com lately but everybody is telling me to go to facebook marketplace.

I miss my ebaykleineanzeige from Germany......

Yes, CL is still a thing here. I've actually had good luck with it. Never used Facebook Marketplace.

[bd139]

Ugh some hell here. Bought a tinySA from Mirfield here who are apparently an official reseller of genuine units. Turns up and won’t calibrate. Posted on tinySA group and designer says it’s a clone 

Fortunately via ebay so disputes are easy to handle. I will just return as cal failed.

TinySA dude has marked them as shipping clones.

 

[med6753]

Ugh some hell here. Bought a tinySA from Mirfield here who are apparently an official reseller of genuine units. Turns up and won’t calibrate. Posted on tinySA group and designer says it’s a clone 

Fortunately via ebay so disputes are easy to handle. I will just return as cal failed.

TinySA dude has marked them as shipping clones.

 

As if they didn't know they were selling fakes and passing them off as genuine. 

[bd139]

Indeed. If I was selling shit I'd at least run the self test before I sold it. They clearly didn't check their supply chain, don't care or didn't do it intentionally. Any way you look at it it's wrong

Edit: I've attached the self test failures. They are actually marginal failures rather than complete shitcan job which makes me wonder if it's not a fake but just a borderline unit. Either way seller should have checked it first.

[ch_scr]

Indeed. If I was selling shit I'd at least run the self test before I sold it. They clearly didn't check their supply chain, don't care or didn't do it intentionally. Any way you look at it it's wrong

It's a real "big brain" move. Pay some royalties, get listed as genuine reseller, then start shifting to clones and make the big $$$ £££. Really nothing could go wrong...

[med6753]

In my mind a "clone" means identical to the original. You wouldn't be able to tell the difference. Since these "clones" don't work as the originals call them what they really are. Fakes. 

[bd139]

Some good points.

I contacted Mirfield and they have already replied saying they will send another unit out and to keep this one. They think that their supplier has thrown a few bad ones in to make up numbers. They apologised and are running self tests before sending them out now apparently. Now I know there is a probability, based on reading the group, that there are ones with modified firmware to pass the self tests so I will DFU the official firmware without such mods onto it and check it works then to make sure I'm not getting screwed. This might be a genuine issue at this point. Time will tell.

I do have to give a thumbs up to Erik at tinySA who has quite frankly amazing support and so far the Mirfield turnaround is minutes 

[McBryce]

In my mind a "clone" means identical to the original. You wouldn't be able to tell the difference. Since these "clones" don't work as the originals call them what they really are. Fakes. 

Fakes can work too sometimes and clones may not be identical to the trained eye. I produced a batch of devices where I used a row of 10 SMD resistors to hide a serial number. The resistors were a required part of the circuit, but I used there orientation to create a binary serial number (right way up=1, upside-down=0).
As soon as clones started appearing I could easily tell whether it was one of mine or not.

McBryce.

[bd139]

That's very sneaky that. I like that 

[McBryce]

That's very sneaky that. I like that 

Erik may be using some similar trick to identify them.

McBryce.

[Specmaster]

Some good points.

I contacted Mirfield and they have already replied saying they will send another unit out and to keep this one. They think that their supplier has thrown a few bad ones in to make up numbers. They apologised and are running self tests before sending them out now apparently. Now I know there is a probability, based on reading the group, that there are ones with modified firmware to pass the self tests so I will DFU the official firmware without such mods onto it and check it works then to make sure I'm not getting screwed. This might be a genuine issue at this point. Time will tell.

I do have to give a thumbs up to Erik at tinySA who has quite frankly amazing support and so far the Mirfield turnaround is minutes 

DFU both units and then you might end up with 2 working ones 

[mnementh]

Just like my WaveTek BNC 630 arb mocks me from under the desk... Welcome to the club, buddy. 

mnem
Here, lemme buy you a brew.

Not one of these by any chance ?
https://www.eevblog.com/forum/repair/wavetek-2025a-0-2-2-200mghz-rf-sig-gen-repair/

Oh, sonuvacrap... no. It's a B&K 4070A/rebadged Berkeley Nucleonics Model 630. I had a total brain-fart and for some reason misremembered it as being rebadged WaveTek.

That guy in Orilla, ON has a 2020A for $300... it was one of the items I was thinking "might make it worth the trip".

https://www.ebay.com/itm/324608786118

mnem
  was I thinking...?

[med6753]

That guy in Orilla, ON has a 2020A for $300... it was one of the items I was thinking "might make it worth the trip".

https://www.ebay.com/itm/324608786118

mnem
  was I thinking...?

"Orilla" sounds too much like "Gorilla". I would avoid. 

[Cerebus]

Can anyone recommend a 4-wire kelvin leads/clips set with banana (safety OK) plugs? Looking for something dirt cheap, around USD25.

My experience when I wanted some was that I couldn't find fully assembled leads that were "cheap enough" by my criteria. I ended up making my own up come ça:



The Kelvin clips I used were cheap Chinese ones and although they don't look much in either this photo or the vendor's photos they are reasonable quality. Ditto the dual banana plugs. Add a bit of silicone test lead (yes, our friends in the Middle Kingdom again), some nylon expandable sheathing and some heatshrink and they're served me well for a couple of years now.