Test Equipment Anonymous (TEA) group therapy thread

[factory]

Quick update.

Tek 475. Spoke to the seller who's response was basically "you're probably holding it wrong"  .

Will you be revealing the ebay seller name, so that we can give him a "Patronising Dickhead" award?

Doesn't need to reveal it, as the username can easily be found under sold listings for the DMM he got with the Tek scope.

Edit: I think you've already found the seller, as it's the same one with the £120 400MHz HP scopes.

David

[factory]

Who wanted a LCD 'scope?
www.ebay.co.uk/itm/203537268248?

Dang... 100 quid...? Even I would buy that just to see what makes it tick...

mnem
 

Bugger, has that been pulled? or was it ending tonight & I just missed it?
The redesigned ePay bidding page doesn't give a start date anymore. 

David

[Specmaster]

Quick update.

Tek 475. Spoke to the seller who's response was basically "you're probably holding it wrong"  .

Will you be revealing the ebay seller name, so that we can give him a "Patronising Dickhead" award?

Hmm, obviously a iPhone user, because that was the excuse given for the failure of iPhone 4 and poor reception. 

https://edition.cnn.com/2010/TECH/mobile/06/25/iphone.problems.response/index.html

[mnementh]

Thanks for the link. It's actually cheaper if I design my own and get it shipped from JLCPCB 

So I did a quick ripple check with DMM And the 110V has 12V RMS ripple on it. All the other rails are good. Culprit found 

OK, if you can that route go for it. If you recall I used those adapters when I re-capped a 465B a few years ago. Worked great. 

   Yea, 12V RMS ripple on the 100VDC is NFG. 

Yeah; we had to badger you into it, but you did finally see the light.   

And good on ya for proselytizing it forward!

mnem
 

[mnementh]

Nothing like a food bargain as well. You will find me regularly in Asda just before closing. Got me 500g 5% mince for today’s dinner yesterday for 20p.

Looking for "yellow labels" has several advantges apart from cost:

• speed: fewer things to look at, fewer choices to make
• serendipity: you look at things you wouldn't normally see, maybe even liking them so much you buy them again

Thats much the same thing with that app as well, you get no guarantees as to what you will be given, apart the approx value is going to 3 to 4 times the price paid. On one occasion, I grabbed a bargain from Gregg's and was given 2 bags for the price of 1. Simply stick what you can't eat that day in the freezer, job done.

I don't have a "smart"phone. My daughter has tried such things with sushi; the result was only "OK".

Personally, I wouldn't go near sushi. I've had excellent results with Gregg's and also Country Bakers, the latter gave my first taste of sourdough bread and other specialities 

Sushi close to its "best by" date...? Ummm... yeah, that does set off alarm bells, even if I didn't generally dislike most of what it's made of.

mnem
But a nice crispy beer-battered Haddock fillet...

[Specmaster]

Who wanted a LCD 'scope?
www.ebay.co.uk/itm/203537268248?

I did but I have one inbound, not as small however but I can live with that as it is the same size as my 1906 DMM and TF930 counter and will form a nice stack, all in working condition and half the price.

[capt bullshot]

Thanks to Capt'n Bullshot, my fire for time difference measurements has been rekindled.
I present: a DMTD based soley on (select) "logic" devices. Well it's all 74 series at least. Design exploits hopefully as much of the "analog" behaviour these can give.
Unbuffered inverter (74VHCU04) in self biased configuration make an ac-coupled input stage that should have a wide input power range. XOR as mixers as per Capt'n Bullshots example.
"Single-Bit Dual-Supply Bus Transceiver" (74LVC1T45) to give the XOR a (hopefully) more graceful output from a independent stabilized rail.
For output comperators after the LPF: Schmitt trigger buffers (74AHC1G17). For the hell of it, didn't have another comperator handy and these jumped me in a moment of overconfidence.
At least that's my defence if they turn out as single point of major performance degradation.
Mostly star-power-point layout and ample decoupling and ferrite beads. Logic lines feature series termination to take the edge off. LPF includes a ferrite bead to reduce fast edges going through.
This either works or it doesn't  Place your bets if this is a good idea, and if it breaks: where? 

I believe all the ferrite beads are neither harmful nor useful in this circuit, so I'd skip them. But I'm a strong believer in decoupling capacitors and ground planes. I'd place at least one electrolytic cap per power rail in addition to the ceramics. Otherwise, yes I'd expect it to work, and I'd agree the weak point are the 1G17 schmitt triggers used as comparators.

Looking forward to see your results. What kind of TIC do you plan to use?

[mnementh]

Who wanted a LCD 'scope?
www.ebay.co.uk/itm/203537268248?

Dang... 100 quid...? Even I would buy that just to see what makes it tick...

mnem
 

Bugger, has that been pulled? or was it ending tonight & I just missed it?
The redesigned ePay bidding page doesn't give a start date anymore. 

David

At the time I commented, there was like 39 minutes left on the listing. I suspect it'll be back.

mnem
 

[Specmaster]

You really can't fix stupid, they clearly have zero respect for the rest of society. They are almost a ticking time bomb, only caring about their own liberty, the sensible double vacced people have to either suffer them or stay at home 

[bd139]

Ok 475 progress. Discovered a couple of things.

Firstly the cap across the 50-110v rails was open circuit. I removed it courtesy of the metcal tips AVGresponding pointed out a few weeks back. It went through those joints like butter! Rather than order a replacement mount and stuff I have temporarily bodged 2x 220uF 100v caps in as I had them in stock.

Secondly while I was moving it around a square nut fell out. After spending a few minutes in the service manual I found it was the one securing the tube shield to the back bulkhead plastics. The whole tube shield is loose.  Well that explains why the horizontal deflection wires were shorting. So I’ve got to find the screw now which is on the inside of the tube shield and reinstall it in case it falls out somewhere and shorts something. That possibly means removing the tube 

Ah well I wanted a project. Nice to be back in the trenches!

Capacitor bodge attached.

[ch_scr]

Thanks to Capt'n Bullshot, my fire for time difference measurements has been rekindled.
I present: a DMTD based soley on (select) "logic" devices. Well it's all 74 series at least. Design exploits hopefully as much of the "analog" behaviour these can give.
Unbuffered inverter (74VHCU04) in self biased configuration make an ac-coupled input stage that should have a wide input power range. XOR as mixers as per Capt'n Bullshots example.
"Single-Bit Dual-Supply Bus Transceiver" (74LVC1T45) to give the XOR a (hopefully) more graceful output from a independent stabilized rail.
For output comperators after the LPF: Schmitt trigger buffers (74AHC1G17). For the hell of it, didn't have another comperator handy and these jumped me in a moment of overconfidence.
At least that's my defence if they turn out as single point of major performance degradation.
Mostly star-power-point layout and ample decoupling and ferrite beads. Logic lines feature series termination to take the edge off. LPF includes a ferrite bead to reduce fast edges going through.
This either works or it doesn't  Place your bets if this is a good idea, and if it breaks: where? 

I believe all the ferrite beads are neither harmful nor useful in this circuit, so I'd skip them. But I'm a strong believer in decoupling capacitors and ground planes. I'd place at least one electrolytic cap per power rail in addition to the ceramics. Otherwise, yes I'd expect it to work, and I'd agree the weak point are the 1G17 schmitt triggers used as comparators.

Looking forward to see your results. What kind of TIC do you plan to use?

Yeah I'll bodge in some smd tants    The pcb is designed with a ground layer on top.
There is also one used inner layer to mark where isolated jumpers on top are to be installed.
The 1G17 have a hefty 0.5V - 1.65V hysteresis tolerance. Maybe I find some work better than others?
As a digitizer I plan to use a scope. I also have a PM6670 with TCXO option, but no digital readout.
If I get some signs of life, I plan to do the test 5065AGuru recommended:

...wrapped 4 feet of RG58C/U around a coffee cup and measured the delay at ambient and then poured boiling water into the cup.

The cable delay changed by 40 PicoSeconds.

Resolution is 2 FemtoSeconds but noise level is in the 20 to 50 FemtoSecond range.

[capt bullshot]

First 24h measurement with the new frequency difference meter:

First graph: my GPSDO vs. the FRS rubidium (rc-frs)



Second: my GPSDO vs. the TruePosition GPSDO (rc-tp)



Third: the difference of the above - FRS vs. TruePosition (frs-tp)



And the ADEV graph by TimeLab:



1sec ADEV apparently is dominated by FRS noise. Looks my GPSDO is somewhat better in the short term (10s ... 300s), medium term (1000s ... 10000s) the TruePosition wins. Long term should be defined by the FRS, but I can't see the trend yet. Of course, this is somewhat comparing apples to oranges, they have different antennas with different view of the skies.

[mnementh]

...Capacitor bodge attached.   

mnem
 

[Robert763]

Who wanted a LCD 'scope?
www.ebay.co.uk/itm/203537268248?

Dang... 100 quid...? Even I would buy that just to see what makes it tick...

mnem
 

Bugger, has that been pulled? or was it ending tonight & I just missed it?
The redesigned ePay bidding page doesn't give a start date anymore. 

David

Ended on schedule no bids.
Looks OK to me seller is a house clearence type
Watch for relist.

[capt bullshot]

One more graph:



Doesn't have any more information as the rc-frs from above, but looks nice

[Robert763]

So Pictures of the £40 HP 8640B
Shown at 100MHz -20dBm. All attenuator steps OK. Measured with 8568B. AM mod shown, FM is OK too. Very clean, late build.
Can I self declare jammy git?

[mnementh]

...So I’ve got to find the screw now which is on the inside of the tube shield and reinstall it in case it falls out somewhere and shorts something. That possibly means removing the tube 

Ah well I wanted a project. Nice to be back in the trenches!

Mmmhmmm... have you tried *gulp* shaking it out...?   
mnem
Hold onto your butts...

[tautech]

So Pictures of the £40 HP 8640B
Shown at 100MHz -20dBm. All attenuator steps OK. Measured with 8568B. AM mod shown, FM is OK too. Very clean, late build.
Can I self declare jammy git?

Here you go:

[factory]

...So I’ve got to find the screw now which is on the inside of the tube shield and reinstall it in case it falls out somewhere and shorts something. That possibly means removing the tube 

Ah well I wanted a project. Nice to be back in the trenches!

Mmmhmmm... have you tried *gulp* shaking it out...?   
mnem
Hold onto your butts...

I had a similar thought, to turn it upside down to hear it rattling about, if it's still in there.

My hp 180A has few missing screws for the CRT shield too, but it doesn't seem loose and as the holes don't line up I wondered if they were ever fitted, or if it a was a problem with the early production run. 


David

[Specmaster]

Ok 475 progress. Discovered a couple of things.

Firstly the cap across the 50-110v rails was open circuit. I removed it courtesy of the metcal tips AVGresponding pointed out a few weeks back. It went through those joints like butter! Rather than order a replacement mount and stuff I have temporarily bodged 2x 220uF 100v caps in as I had them in stock.

Secondly while I was moving it around a square nut fell out. After spending a few minutes in the service manual I found it was the one securing the tube shield to the back bulkhead plastics. The whole tube shield is loose.  Well that explains why the horizontal deflection wires were shorting. So I’ve got to find the screw now which is on the inside of the tube shield and reinstall it in case it falls out somewhere and shorts something. That possibly means removing the tube 

Ah well I wanted a project. Nice to be back in the trenches!

Capacitor bodge attached.

Just a thought, but seeing as you replaced that open circuit cap on the 50-100v rail, have you rechecked the ripple at all?

[bd139]

Yeah .2v which is in spec now 

Have fixed the loose CRT and var knobs now as well. Reassembly in progress.

Robert deserves the jammy git award for that 8640B 

[bd139]

...So I’ve got to find the screw now which is on the inside of the tube shield and reinstall it in case it falls out somewhere and shorts something. That possibly means removing the tube 

Ah well I wanted a project. Nice to be back in the trenches!

Mmmhmmm... have you tried *gulp* shaking it out...?   
mnem
Hold onto your butts...

I had a similar thought, to turn it upside down to hear it rattling about, if it's still in there.

My hp 180A has few missing screws for the CRT shield too, but it doesn't seem loose and as the holes don't line up I wondered if they were ever fitted, or if it a was a problem with the early production run. 


David

That’s “interesting”. HP clearly designed that on a Friday afternoon 

[mansaxel]

Yeah .2v which is in spec now 

Have fixed the loose CRT and var knobs now as well. Reassembly in progress.

Robert deserves the jammy git award for that 8640B 

And my eternal envy -- for I desire a 8640B. Or any boat anchor RF gen. When I've got that, all i need is a SA. Or so I think.

Meanwhile, neither the repair queue nor the project stack are shrinking, but it is funnier to put them off and dream of gear...

Did a somewhat deep dive (deep since it did require me swimming in pretty uncharted waters of knowledge) into a 3-phase motor yesterday, for my neighbour. He's had it rewound by a winding shop but it does not work. We tried to find out if the winding shop had put it together correctly or not.

At any rate, it was moot, because something he's done to it -- perhaps as a consequence of faulty rewinding, perhaps not, it is thoroughly roasted. Again. We first tried to make sense of it by measuring ohms, but that did not help. Then I tried inductance (DE-5000  ). Made more sense, but not enough.  Finally, cracked it open, just to reveal a blackened winding.

[bd139]

Back at proper computer now. Some horrible things to scare you. mnem vomiting earlier will persist 

Quick test to see if the caps would do the job. Dodgy prototype soldering 



I was going to use the original CRT nut and screw but I didn't like it. It required (a) screwing on from the inside and the tube removing and (b) didn't have a locking washing of any sort on it. So I used some M3 stainless hardware instead. This is less likely to fall off again.



All assembled and tested. The only remaining issues appear to be that the beam finder switch is a bit dirty which I don't care about and the disintegrated knob (366-1280-00) at the top right, which I'm also not that bothered about as it's only the B trigger control.



Currently burning in for an hour before bed. Hopefully the god of tants will not smite me 

[med6753]

...So I’ve got to find the screw now which is on the inside of the tube shield and reinstall it in case it falls out somewhere and shorts something. That possibly means removing the tube 

Ah well I wanted a project. Nice to be back in the trenches!

Mmmhmmm... have you tried *gulp* shaking it out...?   
mnem
Hold onto your butts...

Can't tell you how many times I dropped a screw into the bowels of a 400 series and I had to resort to shaking, turning, and lots of cursing until it finally dropped onto the bench. 

The transistors for the Type 547 showed up but too late in the day. Tomorrow's activity.