Test Equipment Anonymous (TEA) group therapy thread

[bd139]

So I guess the question that pertains is... were you able to successfully mod it to the broader frequency range as you were talking about earlier?   

Nope. I just released the magic smoke out of the PA. It lasted 3 minutes before it went bang. Widlarized the entire fucker.

The LO worked pretty well. The PA was a pile of shit. 1960 style here:



D was marked as 0.5-1.5mA which LTspice agrees with, however the first transistor load hogs and you end up with 250mA going through it followed by interesting smoke signals. Woosh. Tried a couple of 2n2222a's in it as well and it went fizz and pop.

[nfmax]

I took a relative to watch the last flight past W-s-Mud; he was delighted since he was an apprentice at Filton in the 60s. Watching a heavy bomber stand on a wingtip ought to be impossible, but we saw it that day.

I've seen quite a lot of footage from that flight and it's obvious that the conversation in the cockpit went something like: "OK, boys. It's her last ever flight, let's get creative and see what she'll do".

Of course, Avro's have form. Eric Brown rolled a Lancaster on 16th May 1947.

[Specmaster]

So I guess the question that pertains is... were you able to successfully mod it to the broader frequency range as you were talking about earlier?   

Nope. I just released the magic smoke out of the PA. It lasted 3 minutes before it went bang. Widlarized the entire fucker.

The LO worked pretty well. The PA was a pile of shit. 1960 style here:



D was marked as 0.5-1.5mA which LTspice agrees with, however the first transistor load hogs and you end up with 250mA going through it followed by interesting smoke signals. Woosh. Tried a couple of 2n2222a's in it as well and it went fizz and pop.

Interestingly these are sold by Aliex from a few traders and it seems from the feedback that nobody has yet built one but most give it 5 stars out of 5, how the fuck does that work then, clearly as you have discovered it doesn't and its a big turd pile.

I'd give it 5 out 5 for comedic value 

[bd139]

Yep. I think most aliexpress purchases are "it arrived, 5 stars but I haven't rate the product yet".

I just built it on the bench standalone. There is no way this works. There needs to be some sort of degeneration on the emitters to stop thermal runaway. There's a positive feedback loop which when the top transistor starts heating it knocks the Vbe drop down, this causes base current to rise, causes Vce to rise proportionally and this causes Pd to rise (Pd=IcVce) which causes Vbe to drop and so forth.

If I stick a 10 ohm in series with the emitters of the transistors it will stabilise quite happily. That should be there. But it kills the gain.

I'll never whine about an LM386 again.

[Specmaster]

Yep. I think most aliexpress purchases are "it arrived, 5 stars but I haven't rate the product yet".

I just built it on the bench standalone. There is no way this works. There needs to be some sort of degeneration on the emitters to stop thermal runaway. There's a positive feedback loop which when the top transistor starts heating it knocks the Vbe drop down, this causes base current to rise, causes Vce to rise proportionally and this causes Pd to rise (Pd=IcVce) which causes Vbe to drop and so forth.

If I stick a 10 ohm in series with the emitters of the transistors it will stabilise quite happily. That should be there. But it kills the gain.

I'll never whine about an LM386 again.

Now this one however has been built and reportedly works well and sounds good? How can a tiny speaker like that sound good?

https://www.banggood.com/AM-FM-Radio-Electronics-Kit-Electronic-DIY-Learning-Kit-p-946145.html?gmcCountry=GB&currency=GBP&createTmp=1&utm_source=googleshopping&utm_medium=cpc_elc&utm_content=zouzou&utm_campaign=pla-uk-ele-pc&gclid=CjwKCAiAn5rUBRA3EiwAUCWb28mWwbrLfoXztrlRYF1Zx3Ep1yFiWNhAbMWXxMUoaryvCY_azebnCxoCzZYQAvD_BwE&cur_warehouse=CN

[Specmaster]

Here is the same set that you got, but from Banggood and people have built it got it to work but their comments make good reading...

https://www.banggood.com/3Pcs-Seven-AM-Radio-Electronic-DIY-Kit-Electronic-Learning-Set-p-1156059.html?gmcCountry=GB&currency=GBP&createTmp=1&utm_source=googleshopping&utm_medium=cpc_elc&utm_content=zouzou&utm_campaign=usc-gb-test-pc&gclid=CjwKCAiAn5rUBRA3EiwAUCWb2-GZza8-Ss0zTuuZMI2pCLSUgobprRiIk0zbWOhtmsMPHjRVhI5zwxoCTOAQAvD_BwE&cur_warehouse=CN

[bd139]

Those are subtly different. One has an extra IF stage and an interstage transformer.  The other one is a digital tuner.

The one with the interstage looks pretty good if I'm honest. I might grab that on next month's aliexpress crap cycle.

As for the speaker sounding good, when you're receiving AM, it always sounds like shit

[Specmaster]

Those are subtly different. One has an extra IF stage and an interstage transformer.  The other one is a digital tuner.

The one with the interstage looks pretty good if I'm honest. I might grab that on next month's aliexpress crap cycle.

As for the speaker sounding good, when you're receiving AM, it always sounds like shit

You can get AM to sound pretty good, listen to it on an old Hacker or HMV Diplomat set and you would be surprised at the quality of sound. It just needs a better designed radio to extract it. I have both those sets and while they are not FM or DAB quality, there really listenable to.

[bd139]

I've been listening to CDs for too many years to like AM. It's fine (SSB) for voice comms etc but that's about it if you ask me.

Also AM broadcast skips so if you tune to 7019KHz at the moment you'll get Chinese AM station shit here in the UK instead of the CW that is supposed to be there 

Open: http://hackgreensdr.org:8901/ , hit 40m, select AM mode and tune to 7019KHz. Grr.

[Specmaster]

I've been listening to CDs for too many years to like AM. It's fine (SSB) for voice comms etc but that's about it if you ask me.

Also AM broadcast skips so if you tune to 7019KHz at the moment you'll get Chinese AM station shit here in the UK instead of the CW that is supposed to be there 

Open: http://hackgreensdr.org:8901/ , hit 40m, select AM mode and tune to 7019KHz. Grr.

I'll try that later. I also listen to CDs and I agree the audio quality is good however, you still require the audio amplifier and speakers to be equally as good if not better.

Those small cheap AM radios cannot do justice to a decent audio input.

[Neomys Sapiens]

I took a relative to watch the last flight past W-s-Mud; he was delighted since he was an apprentice at Filton in the 60s. Watching a heavy bomber stand on a wingtip ought to be impossible, but we saw it that day.

The only thing about seeing that flight that didn't make me happy, apart from the obvious "last flight" nature of it, is that someone really ought to have got a couple of English Electric Lightnings out of mothballs as a fighter escort. 

Errr....please no! While I'm totally with you on the topic of the Vulcan (and the eternal grace of the Hunter, and the ingenuity of the Harrier, and the TSR.2), the Lightning goes definitely into the OTHER category of british planes...with the Shackleton, the Seamew, the Fairey Gannet, the Blackburn Beverley, the Libellula, and some others. I mean, did you have specialists for plug ugly over there?
Blackburn was certainly leading the field in this category snout, ears and tail; with Handley-Page a close runner-up.

Look at that midriff...it looks like some big bad airplane humped it some months before! Fuh!

[Specmaster]

I took a relative to watch the last flight past W-s-Mud; he was delighted since he was an apprentice at Filton in the 60s. Watching a heavy bomber stand on a wingtip ought to be impossible, but we saw it that day.

The only thing about seeing that flight that didn't make me happy, apart from the obvious "last flight" nature of it, is that someone really ought to have got a couple of English Electric Lightnings out of mothballs as a fighter escort. 

Errr....please no! While I'm totally with you on the topic of the Vulcan (and the eternal grace of the Hunter, and the ingenuity of the Harrier, and the TSR.2), the Lightning goes definitely into the OTHER category of british planes...with the Shackleton, the Seamew, the Fairey Gannet, the Blackburn Beverley, the Libellula, and some others. I mean, did you have specialists for plug ugly over there?
Blackburn was certainly leading the field in this category snout, ears and tail; with Handley-Page a close runner-up.

Look at that midriff...it looks like some big bad airplane humped it some months before! Fuh!

It was designed for performance and having personally witnessed it flying along a runaway, then pulled vertical and I mean vertical. Opened the throttle and it did a perfect imatation of a rocket, you gain a respect for the plane and it was years ahead of the rest.

[tautech]

It was designed for performance and having personally witnessed it flying along a runaway, then pulled vertical and I mean vertical. Opened the throttle and it did a perfect imatation of a rocket, you gain a respect for the plane and it was years ahead of the rest.

20+ odd years back the Yanks were here for exercises with a couple of F14's.
It was all over TV and news and as I'm not far from the flight path for the military runway in NW Auckland so I witnessed the mock raids they did as they came in LOW over the high part of my property. I was up there at the time and it was truly a sight with our outdated Skyhawk'ssparrow's trying to defend their home base from F14's. 
I can still sense the hairs raising on my neck just thinking about it. 
It was all quite enough to put a horn on a jellyfish. 

Well we got well and truly whipped. 

Anyways, the day the F14's left I'll never forget.....one sedately lifted off with a steady rate of climb and passed by and disappeared from sight on it's way to OZ. The other however left with a bit more speed and when he was still within sight of the airbase gave it a FULL boot full and disappeared vertically into a perfectly clear blue sky. Wow, just wow that thing had some balls !

The stuff we'll take to our graves..... 

[bd139]

The finest aircraft never made it past prototype, sometimes not even that far. There is a whole section dedicated to them in the book "My Tank Is Fight" by Zack Parsons. This includes such joys as backpack helicopters, Nazi space bombers, tanks with wings and on land hardware, stupidly large tanks.

[Vtile]

Does anyone have experience of Racal-dana multimeters? They seems to have been on the high end of the spectrum, but information is really scarce.

[bitseeker]

I don't have any Racal-Dana multimeters, just some universal counters. Something happen to yours or are you looking to acquire some?

[Vtile]

I don't have any Racal-Dana multimeters, just some universal counters. Something happen to yours or are you looking to acquire some?

Let say I did found one covered in dust in old measurement instrument stash. R-D microprocessing multimeter 6000, 6½ digits, seems still be more stable than 'most' (take with grain of salt 15minutes used for googling) low to medium priced 6½ meters today.  It does seems to have interesting resistance guard post (beryllium copper btw) as standard.

[tggzzz]

I restrained myself to buying a ridiculous quantity of wire-ended neon bulbs, a big bag of bigger-than-normal resistors, six 50ohm SMA terminators, and a Tek 475 which sort-of-works but has 2 6062B probes, the service manual and a front cover.

Total cost including entry was £29

Progress with the 475; it looks like it is repairable so that it can be flogged.

The initial assessment was: timebase intermittent to the point of being buggered, ditto ch1 and to a lesser extent ch2.

Currently the timebase is fixed, and ch1/2 are reliable, but ch1's HF performance is poor; 1.8ns risetime on both of them.

Components changed: big fat zero. No caps, nothing. Wow.

Components cleaned: lots. Internally it was pretty clean albeit with a little dust. Dust removed with handheld Dyson and a small paintbrush. But the switches were a pain, all of them, since I've had to remove 3 boards. Where possible, the gold finger cam switches had the usual paper-soaked-in-IPA treatment. The conventional rod-operated multipole push switches had some DeOxit squirted in.

The timebase was more interesting; the unreliability was cured by cleaning the front panel dual timebase rotary knob, not the cam switches. The problem was that the b-timebase is engaged by a microswitch; that microswitch pushes up on a white nylon bushing which in turn pushes on a free-floating spike inside the rotary knob. The microswitch didn't give enough push to move the spike reliably, so it was touch and go whether the a/b/neither timebase would run. Flushing the spike and its channel in the knob with IPA allowed the spike's position to be restored by the microswitch. I'd have taken a photo, but by the time I knew that really was the problem, I'd reinserted the timing board (ugh) and then put the sweep board back on top of it.

Quite frankly that's a foul mechanical bodge; there should have been a spring pushing the bushing to restore the spike. Relying on the strength of a microswitch is tacky tacky tacky.

The ch1/ch2 is less interesting but still annoying. The attenuator gold finger cam switches are easily accessible and were cleaned in the usual way, but the other ones are deeply buried; fortunately they can be tested (and are OK) without removing that board. OTOH the Trig view/bandwidth cam switches are more accessible, except that full access is impossible since they are held in place by melted plastic switch casing supports. Cleaning them with IPA was much better, but not perfect; a tiny amount of DeOxit was needed for proper contact, and the switch body needed a tinu amount of oil (ugh) to move smoothly.

Tomorrow's job is to investigate and tweak the ch1 bandwidth; I hope that's all that is necessary.

[bitseeker]

Let say I did found one covered in dust in old measurement instrument stash. R-D microprocessing multimeter 6000, 6½ digits, seems still be more stable than 'most' (take with grain of salt 15minutes used for googling) low to medium priced 6½ meters today.  It does seems to have interesting resistance guard post (beryllium copper btw) as standard.

Sounds pretty nice. Post pics. I think I may have seen one a couple years ago. Someone here may know more about them.

[Cubdriver]

Let say I did found one covered in dust in old measurement instrument stash. R-D microprocessing multimeter 6000, 6½ digits, seems still be more stable than 'most' (take with grain of salt 15minutes used for googling) low to medium priced 6½ meters today.  It does seems to have interesting resistance guard post (beryllium copper btw) as standard.

Sounds pretty nice. Post pics. I think I may have seen one a couple years ago. Someone here may know more about them.

A quick search returned this:
https://archive.org/details/racal_Racal-Dana_6000_Digital_Multimeter_Operation_and_Service_Manual
though I can't vouch for the site as I've never downloaded anything from them.

And this one:
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Racal/Racal-Dana_6000_Digital_Multimeter_Operation_and_Service_Manual.pdf
immediately downloaded a PDF operating/service manual that appears at a cursory glance to be pretty readable...

Beyond that I don't know much as the Dana meters I have predate their association with Racal.

-Pat

[tautech]

I restrained myself to buying a ridiculous quantity of wire-ended neon bulbs, a big bag of bigger-than-normal resistors, six 50ohm SMA terminators, and a Tek 475 which sort-of-works but has 2 6062B probes, the service manual and a front cover.

Total cost including entry was £29

Progress with the 475; it looks like it is repairable so that it can be flogged.

The initial assessment was: timebase intermittent to the point of being buggered, ditto ch1 and to a lesser extent ch2.

Currently the timebase is fixed, and ch1/2 are reliable, but ch1's HF performance is poor; 1.8ns risetime on both of them.

Components changed: big fat zero. No caps, nothing. Wow.

Components cleaned: lots. Internally it was pretty clean albeit with a little dust. Dust removed with handheld Dyson and a small paintbrush. But the switches were a pain, all of them, since I've had to remove 3 boards. Where possible, the gold finger cam switches had the usual paper-soaked-in-IPA treatment. The conventional rod-operated multipole push switches had some DeOxit squirted in.

The timebase was more interesting; the unreliability was cured by cleaning the front panel dual timebase rotary knob, not the cam switches. The problem was that the b-timebase is engaged by a microswitch; that microswitch pushes up on a white nylon bushing which in turn pushes on a free-floating spike inside the rotary knob. The microswitch didn't give enough push to move the spike reliably, so it was touch and go whether the a/b/neither timebase would run. Flushing the spike and its channel in the knob with IPA allowed the spike's position to be restored by the microswitch. I'd have taken a photo, but by the time I knew that really was the problem, I'd reinserted the timing board (ugh) and then put the sweep board back on top of it.

Quite frankly that's a foul mechanical bodge; there should have been a spring pushing the bushing to restore the spike. Relying on the strength of a microswitch is tacky tacky tacky.

The ch1/ch2 is less interesting but still annoying. The attenuator gold finger cam switches are easily accessible and were cleaned in the usual way, but the other ones are deeply buried; fortunately they can be tested (and are OK) without removing that board. OTOH the Trig view/bandwidth cam switches are more accessible, except that full access is impossible since they are held in place by melted plastic switch casing supports. Cleaning them with IPA was much better, but not perfect; a tiny amount of DeOxit was needed for proper contact, and the switch body needed a tinu amount of oil (ugh) to move smoothly.

Tomorrow's job is to investigate and tweak the ch1 bandwidth; I hope that's all that is necessary.

This gem  ^^^ of Tek 475 repair experience deserves its own thread or at least be tacked onto a 475 repair thread.....NOT buried in the TEA thread !
Thanks for sharing.

[mnementh]

So I guess the question that pertains is... were you able to successfully mod it to the broader frequency range as you were talking about earlier?   

Nope. I just released the magic smoke out of the PA. It lasted 3 minutes before it went bang. Widlarized the entire fucker.

The LO worked pretty well. The PA was a pile of shit. 1960 style here:



D was marked as 0.5-1.5mA which LTspice agrees with, however the first transistor load hogs and you end up with 250mA going through it followed by interesting smoke signals. Woosh. Tried a couple of 2n2222a's in it as well and it went fizz and pop.

Interestingly these are sold by Aliex from a few traders and it seems from the feedback that nobody has yet built one but most give it 5 stars out of 5, how the fuck does that work then, clearly as you have discovered it doesn't and its a big turd pile.

I'd give it 5 out 5 for comedic value 

Empirical Engineering at it's terminus; when you realize the project is a time sink you can't just put back in the parts bins and forget about it, the best thing to do is to evac and nuke the site from orbit. It's the ONLY way to be sure you won't be sucked back in. 

Don't forget to [SHIFT-DEL] the schizzmatics and burn the paper "documentation"; bad ideas are one of the hardest things to kill. Just look at Supply Side Economics. 

I restrained myself to buying a ridiculous quantity of wire-ended neon bulbs, a big bag of bigger-than-normal resistors, six 50ohm SMA terminators, and a Tek 475 which sort-of-works but has 2 6062B probes, the service manual and a front cover.

Total cost including entry was £29

Progress with the 475; it looks like it is repairable so that it can be flogged.

The initial assessment was: timebase intermittent to the point of being buggered, ditto ch1 and to a lesser extent ch2.

Currently the timebase is fixed, and ch1/2 are reliable, but ch1's HF performance is poor; 1.8ns risetime on both of them.

Components changed: big fat zero. No caps, nothing. Wow.

Components cleaned: lots. Internally it was pretty clean albeit with a little dust. Dust removed with handheld Dyson and a small paintbrush. But the switches were a pain, all of them, since I've had to remove 3 boards. Where possible, the gold finger cam switches had the usual paper-soaked-in-IPA treatment. The conventional rod-operated multipole push switches had some DeOxit squirted in.

The timebase was more interesting; the unreliability was cured by cleaning the front panel dual timebase rotary knob, not the cam switches. The problem was that the b-timebase is engaged by a microswitch; that microswitch pushes up on a white nylon bushing which in turn pushes on a free-floating spike inside the rotary knob. The microswitch didn't give enough push to move the spike reliably, so it was touch and go whether the a/b/neither timebase would run. Flushing the spike and its channel in the knob with IPA allowed the spike's position to be restored by the microswitch. I'd have taken a photo, but by the time I knew that really was the problem, I'd reinserted the timing board (ugh) and then put the sweep board back on top of it.

Quite frankly that's a foul mechanical bodge; there should have been a spring pushing the bushing to restore the spike. Relying on the strength of a microswitch is tacky tacky tacky.

The ch1/ch2 is less interesting but still annoying. The attenuator gold finger cam switches are easily accessible and were cleaned in the usual way, but the other ones are deeply buried; fortunately they can be tested (and are OK) without removing that board. OTOH the Trig view/bandwidth cam switches are more accessible, except that full access is impossible since they are held in place by melted plastic switch casing supports. Cleaning them with IPA was much better, but not perfect; a tiny amount of DeOxit was needed for proper contact, and the switch body needed a tinu amount of oil (ugh) to move smoothly.

Tomorrow's job is to investigate and tweak the ch1 bandwidth; I hope that's all that is necessary.

This gem  ^^^ of Tek 475 repair experience deserves its own thread or at least be tacked onto a 475 repair thread.....NOT buried in the TEA thread !
Thanks for sharing.

Ditto. This isn't resurrecting a boat anchor; this is restoring a steam engine salvaged from the Titanic so it runs.     


mnem
Jeebus. Now I know what to do with my "2230 in a bin" if I ever get tired of stubbing my toes on it... 

[beanflying]

Employing a new security device to keep the test gear safe  Stumpy turned up last week around the yard but put his nose inside the shack today.

[Brumby]

Nice specimen.

I just realised I left out the blue-tongue in Australia's list of "interesting" creatures.  Just remember to keep your fingers and toes out of the way - and don't feed him after midnight.

[tautech]

Employing a new security device to keep the test gear safe  Stumpy turned up last week around the yard but put his nose inside the shack today.

<blue  >