Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 1722273 times)

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Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11225 on: May 25, 2018, 01:01:56 pm »
They're quite easy to smoke. All you have to do is stick it across two phases on a three phase system, as our sparky did with a bus bar and a 240V drop a while back. Fecking eejit.
I'm guessing that he was getting on a bit and was forgetting the new three phase colours use black for a phase and blue for a neutral. We used to have them reversed, so a coloured cable used to mean a live cable and black was always nuetral. I always thought it was a dangerous move to change our colouring system.

From mobile device so predictive text might have struck again [emoji83]
« Last Edit: May 25, 2018, 01:03:46 pm by Specmaster »
Who let Murphy in?
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11226 on: May 25, 2018, 01:12:49 pm »
Shows how good the original design was if it survived that amount of overvoltage, even
 if they were a little bit quirky in areas, I like my couple of Heathkit item's and there is still loads on offer.

Indeed. I like Heathkit stuff generally. I've had a fair bit of it over the years. It mostly just works and stays working bar the usual age related problems of old equipment.

I'm guessing that he was getting on a bit and was forgetting the new three phase colours use black for a phase and blue for a neutral. We used to have them reversed, so a coloured cable used to mean a live cable and black was always nuetral. I always thought it was a dangerous move to change our colouring system.

Wouldn't surprise me if the guy is just dumb or colour blind. Ours is a very new installation (2015) with open channel bus bars above the racks which are properly labelled so this should not be rocket science. The tap off boxes are where the problem turns up...



^^ ours looks a bit like that. Not sure which vendor it is. It's mounted rails down though and you stuff the tap offs into it from below.
« Last Edit: May 25, 2018, 01:14:35 pm by bd139 »
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11227 on: May 25, 2018, 01:48:07 pm »
Shows how good the original design was if it survived that amount of overvoltage, even
 if they were a little bit quirky in areas, I like my couple of Heathkit item's and there is still loads on offer.

Indeed. I like Heathkit stuff generally. I've had a fair bit of it over the years. It mostly just works and stays working bar the usual age related problems of old equipment.

I'm guessing that he was getting on a bit and was forgetting the new three phase colours use black for a phase and blue for a neutral. We used to have them reversed, so a coloured cable used to mean a live cable and black was always nuetral. I always thought it was a dangerous move to change our colouring system.

Wouldn't surprise me if the guy is just dumb or colour blind. Ours is a very new installation (2015) with open channel bus bars above the racks which are properly labelled so this should not be rocket science. The tap off boxes are where the problem turns up...



^^ ours looks a bit like that. Not sure which vendor it is. It's mounted rails down though and you stuff the tap offs into it from below.
Yep, it would have to be a newish Installation. Either way it's easy to understand how it happened, probably used brown L1 and black L2 thinking of the colours in standard plug top. Mains wiring colours has always been an accident in waiting IMO. I expect its the old corporate cost cutting thing again, too expensive to go with red or brown as the phase colours with either a number or a coloured stripe to indicate L1, L2 etc. [emoji48]

From mobile device so predictive text might have struck again [emoji83]

« Last Edit: May 25, 2018, 05:32:07 pm by Specmaster »
Who let Murphy in?
 

Offline Brumby

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11228 on: May 25, 2018, 04:32:25 pm »
I come to admit my shame....  After dropping one too many things on the floor that scuttle under the workbench and flailing around trying to see, I have made an upgrade to my work area.

I fitted two LED strips rescued from a defunct TV to the underside of the bench top.  Powered by one of my PSUs (for the moment), I can now see perfectly.  Reaching the extremities is still fun - but if the item has some ferrous content, I use the magnetic pick up tool that seems to have permanently moved inside from the garage.

I know .... this is just throwing down the gauntlet to Murphy.  Falling things are going to perform additional gymnastics now - and will jump into corners never before explored.
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11229 on: May 25, 2018, 04:54:44 pm »
That’s a really cool idea. I like that.
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11230 on: May 25, 2018, 05:05:02 pm »
I come to admit my shame....  After dropping one too many things on the floor that scuttle under the workbench and flailing around trying to see, I have made an upgrade to my work area.

I fitted two LED strips rescued from a defunct TV to the underside of the bench top.  Powered by one of my PSUs (for the moment), I can now see perfectly.  Reaching the extremities is still fun - but if the item has some ferrous content, I use the magnetic pick up tool that seems to have permanently moved inside from the garage.

I know .... this is just throwing down the gauntlet to Murphy.  Falling things are going to perform additional gymnastics now - and will jump into corners never before explored.
Murphy says challenge accepted [emoji48]

From mobile device so predictive text might have struck again [emoji83]

Who let Murphy in?
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11231 on: May 25, 2018, 07:55:58 pm »
I just fought Murphy and won. D83 power supply now in spec and rock solid. TR408 had gone low beta and couldn’t fight the pass transistor.
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11232 on: May 25, 2018, 07:58:47 pm »
Good news, soon have it all back together and working now then  :-+
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11233 on: May 25, 2018, 11:05:03 pm »
This one is hard work ... this evening's shenanigans...

Firstly I transplanted the backplane out of the good scope into the new chassis. This was one of those moments where you think "will this thing ever end up back together?" and wish you never started the job. Found a couple of wiring errors which I corrected. No functional difference just the wrong numbered points used compared to the schematic.



Then the top chassis was reassembled into the bottom half. If you were a scope it looked like a horror movie around my corner. This is the next moment of regret where you think seriously about just buying a damn Keysight unit and leaving all this stuff in the garden and hoping by the morning someone had magically made it go away. Either that or you NEVER go in the garden again. I call it "repair regret" (why did I buy this pile of s**t; what was I thinking?)



Back together and powered it up. HT is still wonky but I expect that. This is just the first stage of the rebuild. After arguing with it a couple of times until the HT decided to wake its shit up, vertical is working. There is no horizontal sweep yet as the plugin has been bodged by the previous owner and doesn't work unless the rails are way off which they aren't now! It does sweep with the cal plugin.

Now one really cool thing is the trace is crispier than a crispy thing from planet crisp. Shot in X-Y mode. Not bad for a 42 year old scope:



Motivation returned. Never give up!
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11234 on: May 25, 2018, 11:20:06 pm »
Excellent work, you will be so proud once you have this completed. Do you think this is one that your Mother might have worked on?

I also secured this just a few minutes ago, of to Clacton tomorrow to collect it, never seen one before but seller swears it works OK.
Who let Murphy in?
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11235 on: May 25, 2018, 11:46:21 pm »
This one is hard work ... this evening's shenanigans...
You know it'll be worth it !


Quote
Now one really cool thing is the trace is crispier than a crispy thing from planet crisp. Shot in X-Y mode. Not bad for a 42 year old scope:


Some centralization adjustments needed.  ;)
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11236 on: May 26, 2018, 12:22:35 am »
Ok regulators are shot, caps are shot, half the diodes are shot in the power supply.

So I bypassed the power supply, which is neatly possible due to two links on the board, and chucked a bench power supply on it.

And you know what? It only still works perfectly. I am extremely surprised!

It pulls a monster current of 40mA per rail and the supply appears not to require tracking so I'll just knock up a LM317/337 type supply, stick and IEC socket and fuse holder on and rip the old ICs and caps out. Phew!

Wouldn't it be easier to just clean up and recap the original board with the bodge wire?  |O

[EDIT]

D'oh!  Or is that what you did?

[/EDIT]


mnem
 :-//
« Last Edit: May 26, 2018, 12:27:50 am by mnementh »
 

Offline Brumby

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11237 on: May 26, 2018, 05:51:49 am »
My under bench lighting has revealed something I didn't want to think about .... The dust collection in the far corners looks like there was an explosion in a felting class.

It's something I just can't unsee ...  :(

I'm just wondering what will travel up the hose if I get the vacuum out......
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11238 on: May 26, 2018, 08:28:39 am »
Excellent work, you will be so proud once you have this completed. Do you think this is one that your Mother might have worked on?

I also secured this just a few minutes ago, of to Clacton tomorrow to collect it, never seen one before but seller swears it works OK.

Quite possible actually. There’s no signatures on the QA sticker though. Unlike tek :(

Last cal date on this was 1983!

Those are really nice. My father had one. He left the C battery in it though and it dissolved everything.
« Last Edit: May 26, 2018, 08:35:47 am by bd139 »
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11239 on: May 26, 2018, 08:29:50 am »
This one is hard work ... this evening's shenanigans...
You know it'll be worth it !


Quote
Now one really cool thing is the trace is crispier than a crispy thing from planet crisp. Shot in X-Y mode. Not bad for a 42 year old scope:


Some centralization adjustments needed.  ;)

The cal is completely shagged to be honest. Mr helpful who fixed it last time decided to just twiddle until it showed something about right  :palm:
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11240 on: May 26, 2018, 08:32:27 am »
Ok regulators are shot, caps are shot, half the diodes are shot in the power supply.

So I bypassed the power supply, which is neatly possible due to two links on the board, and chucked a bench power supply on it.

And you know what? It only still works perfectly. I am extremely surprised!

It pulls a monster current of 40mA per rail and the supply appears not to require tracking so I'll just knock up a LM317/337 type supply, stick and IEC socket and fuse holder on and rip the old ICs and caps out. Phew!

Wouldn't it be easier to just clean up and recap the original board with the bodge wire?  |O

[EDIT]

D'oh!  Or is that what you did?

[/EDIT]


mnem
 :-//

I thought about that but the original board actually had electrolyte soak into it and it was oozing out of the sides as well. I think that one is a write off. The other board was in perfect condition just a bit dusty. Also it was attached to the chassis that had an IEC socket instead of the weird as hell 1970s proprietary inline thing they the other one had. Ergo I decided to take the hard road and make a frankenscope!

Edit: plus I actually enjoy doing things the sick twisted and hard way
« Last Edit: May 26, 2018, 08:33:59 am by bd139 »
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11241 on: May 26, 2018, 08:37:13 am »
Haha, Mr Helpful  :-DD I reckon that could be who a certain Cal lab is employing and when he couldn't find anything on the 3478 to twiddle, scratched his head for a bit and put aside for a while, the following week, picked it up and he'd look again for trimmers etc and gave up and then returned it to me claiming it was uneconomical to repair  :-DD
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Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11242 on: May 26, 2018, 08:41:35 am »
This one is hard work ... this evening's shenanigans...
You know it'll be worth it !


Quote
Now one really cool thing is the trace is crispier than a crispy thing from planet crisp. Shot in X-Y mode. Not bad for a 42 year old scope:


Some centralization adjustments needed.  ;)

The cal is completely shagged to be honest. Mr helpful who fixed it last time decided to just twiddle until it showed something about right  :palm:
Don't you hate it when some muppet just has to fiddle with the internal trimmers.  :scared:  :horse:
Oh bugger it's gunna be a bit of a long road but at least the manual is well documented to do a full alignment and when it's done you'll have the satisfaction of having a perfect instrument. The voltage references aren't too hard but the mark time generator can be tougher if you haven't got access to one.
The buddy that gave me my D83 had a 100 MHz Tek mark time gen and I borrowed that to check mine. These days any reasonable AWG should do the trick for timebase adjustments.
If you have all the gear on hand you'd do it in an evening I reckon excepting if you find further faults.

Which is out, the timebase or the vertical amp ? Both ?  :scared:
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11243 on: May 26, 2018, 08:48:02 am »
Everything is off. I haven’t found anything that is near on :)

I’m going to use my Si5351 synth breakout board for X cal and FG for Y cal on this. I’ll do frequency comp by hand afterwards. The Si5351 you basically tell it a frequency and it generates a clean square wave at that frequency. Once you’ve entered the right calibration constant it’s accurare to 1Hz over the entire range. Neat little IC for £3.
« Last Edit: May 26, 2018, 08:49:37 am by bd139 »
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11244 on: May 26, 2018, 08:49:26 am »
Excellent work, you will be so proud once you have this completed. Do you think this is one that your Mother might have worked on?

I also secured this just a few minutes ago, of to Clacton tomorrow to collect it, never seen one before but seller swears it works OK.

Quite possible actually. There’s no signatures on the QA sticker though. Unlike tek :(

Last cal date on this was 1983!

Those are really nice. My father had one. He left the C battery in it though and it dissolved everything.
With the possibility that your Mother may have worked on it, whats the plan its finished, retain it as family heirloom?
Who let Murphy in?
 

Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11245 on: May 26, 2018, 08:57:05 am »
Yep keep and use. These when they are working have the best display quality of any analogue scope IMHO.

Also I have a cunning plan. I’ve been working on a spectrum analyser for about 2 years on and off. This conveniently will fit inside a vertical plugin. So I will disassemble the duff one and reuse it then be able to slide the SA into the vertical slot, plug the sweep out from the timebase plugin into that and use that as the sweep gen for the SA.

The SA is a pretty dumb one btw. It’s basically a dual conversion receiver with two IF’s. The first LO is voltage controlled. Mix with minicircuits DBM. Second mix is SA612. The output is an AD8307. With some cal and praying this gives around 90dB of dynamic range and a sweep span of about 500KHz to 200Mhz and switchable bandwidth of 1MHz for a band scope of 1Khz for measurements which is perfect for HF. Capability is all based on the only helical filter I could get my mucky fingers on.
« Last Edit: May 26, 2018, 09:00:10 am by bd139 »
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11246 on: May 26, 2018, 09:11:23 am »
Yep keep and use. These when they are working have the best display quality of any analogue scope IMHO.

Also I have a cunning plan. I’ve been working on a spectrum analyser for about 2 years on and off. This conveniently will fit inside a vertical plugin. So I will disassemble the duff one and reuse it then be able to slide the SA into the vertical slot, plug the sweep out from the timebase plugin into that and use that as the sweep gen for the SA.

The SA is a pretty dumb one btw. It’s basically a dual conversion receiver with two IF’s. The first LO is voltage controlled. Mix with minicircuits DBM. Second mix is SA612. The output is an AD8307. With some cal and praying this gives around 90dB of dynamic range and a sweep span of about 500KHz to 200Mhz and switchable bandwidth of 1MHz for a band scope of 1Khz for measurements which is perfect for HF. Capability is all based on the only helical filter I could get my mucky fingers on.
Interesting project.  :-+
I'll keep my eyes open for news of its arise from the ashes of a D83.  :o
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11247 on: May 26, 2018, 09:14:57 am »
If I ever get it working. VCO is unusably unstable at the moment and the crystal filter I built was shit because I had no idea what I was doing when I built it.

There’s a similar design here (which mine is not based on but the topology is about the same) for the interested. They’re not all that complicated :)

http://www.hanssummers.com/spectrumanalyser.html
 
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Offline AF6LJ

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11248 on: May 26, 2018, 12:46:28 pm »
Ant free running VCO that runs at more than a few MHZ is a real challenge to stabilize, without incorporating some form of closed loop frequency stabilization scheme.
Sue AF6LJ
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #11249 on: May 26, 2018, 01:08:04 pm »
Indeed. Also linearity is a problem when the tuning is a varactor.  To be honest it doesn’t require masses of long term stability as I will use a marker generator to align it periodically.

At 200Mhz it drifts up to 1MHz/min though which is shit. Haven’t had time to fix this as I keep buying broken test gear :D
 


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