Test Equipment Anonymous (TEA) group therapy thread

[Specmaster]

That just looks like the perfect time to stay inside and tinker with electronics while your boatanchor of a scope keeps you warm.

That's when you want a modern DSO the size of portable radio 

[bd139]

So much this.

I'd love boat anchors but only during the winter

[Specmaster]

Amen to that, my 3390B is so bloody hot in comparison to the Iwatsu SS 5710 thats sits beneath it.

Be interesting comparing the heat given off from a TDS210 against that.

[bd139]

Feels slightly warm on the top after about 20 minutes and that’s it. Also 100% silent!

[Specmaster]

Hmm, 3390B is neither silent or cool, after 20 minutes you really would not want to be in the same room with it in this heat and you wouldn't want to touch it for long

[mnementh]

HP 643932-001 750W PSU


Just making a little hot water for my TEA... 


mnem
"More POWER!!! Waugh! Waugh!! Waugh!!!"

[bitseeker]

Mo' powah, and bigger coils!

[bitseeker]

And some more shiny:

[mnementh]

Dell 1100SA-L0 1100W PSU


I drank all my TEA...need more.  FAST.


mnem
*Juicy*

[bitseeker]

Load testing is hard, hot work.

[mnementh]

Heh...

Once things settle down I'll have those two HP PSUs in series for a LiPo chargery array. That should be interesting.


mnem
Yes, you may touch it.

[bitseeker]

That's mo' powah!

[med6753]

Here's a better picture of the 465 channel 2 leaf switches (Sorry, but my phone does not do good close ups so bear with me). The pair of leaf switches under that shield with the one on the right is the one that is open.



On the schematic with the coupling switch in DC and the Volts/Div switch set to 5mv the attenuators are completely bypassed and there should be continuity (0 ohms) between R51 and R65. There wasn't. It was open. Position 6 is the culprit.



I decided to go for broke and carefully pry the leaf switch from under the shield. Here is what I found. Not burnt but completely mangled!  How in the hell did that happen? That leaf switch is completely protected by that shield. The only thing that makes some sense is that it was damaged at the factory, QC missed it because it's under the shield, and at some point it did make contact but no longer does.



I carefully straightened out the 2 prongs. The center prongs must be completely folded under or are missing. I couldn't tell. Carefully put it back under the shield.



Result after reassembly of the switch deck. It worked! Now have continuity. And I verified that it drops in and out with the rotation of the switch the same as channel 1. I think I finally nailed all the issues with this Vertical board.



Here's the Vertical board and the Switch board assembled and ready to install. I also fixed the BNC's. When it's complete I'll show the results. If all that's left is to completely calibrate the vertical section because I jack assed so much stuff around I'll be happier than a pig in shit. 

[tggzzz]

I decided to go for broke and carefully pry the leaf switch from under the shield. Here is what I found. Not burnt but completely mangled!  How in the hell did that happen? That leaf switch is completely protected by that shield. The only thing that makes some sense is that it was damaged at the factory, QC missed it because it's under the shield, and at some point it did make contact but no longer does.

Unlikely, unless the first owner never used that channel!

More likely is that a previous owner tried to clean the switch by sticking paper under it, and moving the paper sideways.

Or maybe there was a significant electrical discharge - which seems unlikely but can't be ruled out from the photo.

[med6753]

I decided to go for broke and carefully pry the leaf switch from under the shield. Here is what I found. Not burnt but completely mangled!  How in the hell did that happen? That leaf switch is completely protected by that shield. The only thing that makes some sense is that it was damaged at the factory, QC missed it because it's under the shield, and at some point it did make contact but no longer does.

Unlikely, unless the first owner never used that channel!

More likely is that a previous owner tried to clean the switch by sticking paper under it, and moving the paper sideways.

Or maybe there was a significant electrical discharge - which seems unlikely but can't be ruled out from the photo.

Never used channel 2? Maybe.

Improper cleaning? Again maybe.

A discharge? Very unlikely or I would have seen evidence of FET's Q70A & B being changed. Although the "no trace" issue that cropped up a 2nd time was due to an open Q92. But that just happen a week ago and I certainly didn't blast the inputs with HV.

[bd139]

Looking at that, improper cleaning. What happens, and I have seen this happen, is the equipment flakes out and then some random lab tech gets assigned to review it. Then they crack it open, trace it out and then try and clean it with a cotton bud causing massive buggery. Then this doesn't work or they realise they made it worse so they shrug, chuck it on the BER pile and it eventually ends up in a skip. Then a recycler buys the skip, sells it on to some ham who uses it for 15 years or leaves it in a shed for that time and drops dead. Then it gets SK sale and ends up on ebay or local sale groups. And then into the hands of the first person who cares about it 

Sometimes the recycler is replaced with employees skip diving. My last 475 was a skip dive from the seller. He just chucked it in his garage for 20 years.

[med6753]

Looking at that, improper cleaning. What happens, and I have seen this happen, is the equipment flakes out and then some random lab tech gets assigned to review it. Then they crack it open, trace it out and then try and clean it with a cotton bud causing massive buggery. Then this doesn't work or they realise they made it worse so they shrug, chuck it on the BER pile and it eventually ends up in a skip. Then a recycler buys the skip, sells it on to some ham who uses it for 15 years or leaves it in a shed for that time and drops dead. Then it gets SK sale and ends up on ebay or local sale groups. And then into the hands of the first person who cares about it 

Sometimes the recycler is replaced with employees skip diving. My last 475 was a skip dive from the seller. He just chucked it in his garage for 20 years.

Your explanation makes sense. But if that did happen the tech did a damn good job in putting it back together. Because I saw no tell tale signs that this Vertical board has ever been removed before I got my grubby hands on it. And the only thing I did to clean it was hose the whole thing down with a spray bottle of 100% IPA then use a blow dryer but I wasn't anywhere near that leaf switch. 

[bd139]

Yeah I doubt you did that.

It’s possible that it was assembled like that as well and passed the test process purely by conincidence. I’ve found missing screws and unsoldered joints on new equipment before from tek.

[VK5RC]

Re Probable Initial manufacturing/ QA failures;  I had an old HP 6632 PSU that would go into over voltage protection mode every time you enabled the output, It's a really difficult unit to work on as the manual covers 4 or 5 different models, the schematic covers 2-3 models and you have to refer to the part list to see what parts on the schematic belong to your model. Even the PCB has the same issues with about 20-30% of the PCB unpopulated!!! 
I finally (don't ask how long it took) realised that the virginal PCB (clearly had never been touched till I got there) , never had an output capacitor installed - did that and it worked fine!!!!!!!

[bd139]

Hahaha that doesn't surprise me in the slightest. Had that on a TTI power supply as well. An early PL320 (brown one).

Decided to make some test gear today. I scoffed at the thought of paying for a return loss bridge so I knocked one up quickly with some crap I had lying around. Unfortunately I lost my bag of M3 nuts/screws somewhere so no lid! Works nicely though to at least 21MHz. Not bothered about higher hence the slightly not VHF friendly construction.

@Specmaster: another use for those resistors!



Edit: and a return loss sweep for a reference 50 ohm impedance (grey) and a random transmission line (20m of RG8). DG1022Z+TDS210+RLB = poor man's antenna analyser. You can sweep the marker across to measure a frequency. Return loss is 25mV/dB on vertical (measure using cursors). Response is low here because it's not an actual antenna

[Specmaster]

Hahaha that doesn't surprise me in the slightest. Had that on a TTI power supply as well. An early PL320 (brown one).

Decided to make some test gear today. I scoffed at the thought of paying for a return loss bridge so I knocked one up quickly with some crap I had lying around. Unfortunately I lost my bag of M3 nuts/screws somewhere so no lid! Works nicely though to at least 21MHz. Not bothered about higher hence the slightly not VHF friendly construction.

@Specmaster: another use for those resistors!



Edit: and a return loss sweep for a reference 50 ohm impedance (grey) and a random transmission line (20m of RG8). DG1022Z+TDS210+RLB = poor man's antenna analyser. You can sweep the marker across to measure a frequency. Return loss is 25mV/dB on vertical (measure using cursors). Response is low here because it's not an actual antenna

Need to make a few to chew through 14,000 resistors I think, best order up some ferrite cores etc. [emoji38]

[bd139]

I’ve used nearly 500 of them already

[Specmaster]

I’ve used nearly 500 of them already

Blowing them up eh[emoji6]
You only had 4,000 of them, I had shit loads more then that.

[bd139]

Hahaha only a few by accident

I had 8000.  Sold 4000. Used 500. Got 3500 left. Should be good ‘til I’m dead.

Most of the used ones ended up being convenient leg donors for other things.

[Specmaster]

Hahaha only a few by accident

I had 8000.  Sold 4000. Used 500. Got 3500 left. Should be good ‘til I’m dead.

Most of the used ones ended up being convenient leg donors for other things.

[emoji848] I think I got about 20,000 of em, sold 100 and like you used some for legs, so still got most of.