Test Equipment Anonymous (TEA) group therapy thread

[0culus]

I would work from the shutdown /fault circuitry back here. If you look at the bottom right hand bit of the primary SMPS portion in the service manual, there's a voltage sampling network that should reveal some clues. I haven't LTspiced it but it looks like it's a divider that sums to zero if it's working properly. Anything that doesn't add up trips the fault sense on U1275. You should be able to work back from that to a rail.

If that's fine then the problem may be on the primary side of the SMPS.



Edit: sums to something other than zero by the looks or it's a current summing junction.

Edit 2: I was right. If fault input to U1275 is >200mV for more than 10ms it will shut the supply down. Start there and work back. Read fault protection section 3-55. Interesting design.

My head is spinning from trying to make sense of the schematics on a screen...I need a break...

[med6753]

I would work from the shutdown /fault circuitry back here. If you look at the bottom right hand bit of the primary SMPS portion in the service manual, there's a voltage sampling network that should reveal some clues. I haven't LTspiced it but it looks like it's a divider that sums to zero if it's working properly. Anything that doesn't add up trips the fault sense on U1275. You should be able to work back from that to a rail.

If that's fine then the problem may be on the primary side of the SMPS.



Edit: sums to something other than zero by the looks or it's a current summing junction.

Edit 2: I was right. If fault input to U1275 is >200mV for more than 10ms it will shut the supply down. Start there and work back. Read fault protection section 3-55. Interesting design.

My head is spinning from trying to make sense of the schematics on a screen...I need a break...

You and me both.  This 485 has got my panties in a knot and I need to break away and continue tomorrow. 

[bd139]

Dang it’s 00:30 here and I’m still going strong 

[med6753]

Dang it’s 00:30 here and I’m still going strong 

So what do you want? A metal? 

Edit....going to chill out with some Netflix.

[0culus]

I would work from the shutdown /fault circuitry back here. If you look at the bottom right hand bit of the primary SMPS portion in the service manual, there's a voltage sampling network that should reveal some clues. I haven't LTspiced it but it looks like it's a divider that sums to zero if it's working properly. Anything that doesn't add up trips the fault sense on U1275. You should be able to work back from that to a rail.

If that's fine then the problem may be on the primary side of the SMPS.



Edit: sums to something other than zero by the looks or it's a current summing junction.

Edit 2: I was right. If fault input to U1275 is >200mV for more than 10ms it will shut the supply down. Start there and work back. Read fault protection section 3-55. Interesting design.

My head is spinning from trying to make sense of the schematics on a screen...I need a break...

You and me both.  This 485 has got my panties in a knot and I need to break away and continue tomorrow. 

I'm just going to print the relevant portions of the manual to make my life easier.

[mnementh]

It's been a bit of a wringer, but I've completed my Tune & benchmarks; the full article is up here.   I ramble a bit & lots of pics, so I'm just gonna post the chart & synopsis here.

The TL/DR: Some decreased small file read performance and med-small file write performance and longer RAID Boot times compared to single-channel connected. Otherwise, these $59 SSDs produced very comparable numbers to premium PCIe3.0 drives costing 2x as much, and in RAID, comparable to (In some cases, far exceeding) PCIe4.0 drives costing 5x as much. Definitely a worthwhile experiment.

mnem

[worsthorse]

I would work from the shutdown /fault circuitry back here. If you look at the bottom right hand bit of the primary SMPS portion in the service manual, there's a voltage sampling network that should reveal some clues. I haven't LTspiced it but it looks like it's a divider that sums to zero if it's working properly. Anything that doesn't add up trips the fault sense on U1275. You should be able to work back from that to a rail.

If that's fine then the problem may be on the primary side of the SMPS.



Edit: sums to something other than zero by the looks or it's a current summing junction.

Edit 2: I was right. If fault input to U1275 is >200mV for more than 10ms it will shut the supply down. Start there and work back. Read fault protection section 3-55. Interesting design.

My head is spinning from trying to make sense of the schematics on a screen...I need a break...

You and me both.  This 485 has got my panties in a knot and I need to break away and continue tomorrow. 

I have to say that tracking this conversation has not made me any more enthusiastic about cracking open the 485 I have sitting in the repair queue.   

[0culus]

I don't know what I did, but something I did while fiddling with it fixed whatever was shorted...pointed to something mechanical maybe?

[mnementh]

You stopped drooling on it.

mnem
*agitating-ily*

[0culus]

You stopped drooling on it.

mnem
*agitating-ily*

I don't know what I did, but something I did while fiddling with it fixed whatever was shorted...pointed to something mechanical maybe?

Yep, confirmed. Almost has to be mechanical. Started ticking again when I reinstalled the SMPS.

[mindcrime]

I like to keep my background music a little more sedate:

[mnementh]

mnem
*sedated*

[0culus]

I massaged the placement of the fan power...and we are alive!   

[mnementh]

You mean you "nudged" the "fanatic" who was slobbering all over the insides and making all the pixies angry...?

mnem
 

[0culus]

You mean you "nudged" the "fanatic" who was slobbering all over the insides and making all the pixies angry...?

mnem
 

That fanatic you speak of touched the HV supply and is now dead. 

[mnementh]

Well, that would definitely make him stop slobbering all over the insides of your Tek. Unless it was med; not sure even THAT would stop HIM... 

mnem
*tzzzt*

[med6753]

Well, that would definitely make him stop slobbering all over the insides of your Tek. Unless it was med; not sure even THAT would stop HIM... 

mnem
*tzzzt*

Bite me! 

[0culus]

I guess if you get zapped enough you become immune...or a comic book character. 

Was able to verify that the crt shutdown circuit works correctly. This is a great 'scope, though decidedly a bit more specialized than my 7904A which will continue to sit next to it and see use.

[mnementh]

Well, that would definitely make him stop slobbering all over the insides of your Tek. Unless it was med; not sure even THAT would stop HIM... 

mnem
*tzzzt*

Bite me! 

Not even with rented fangs!!!      Also, I notice you are NOT in any way denying... 

mnem
*the human cartoon*

[beanflying]

Cheap USB data logging high Temperature TEA  #nobodge

[VK5RC]

A great melody. A real war tune.
https://youtu.be/vTkGNcntD7s
've heard them liltin'
At the ewe milkin'
And I've heard them liltin'
Before light a-day
Now they are mournin'
For all time a-liltin'
The flowers of the forest
Are all a' wede away
Sad they for the order
That sent them to the border
The English by guile
For once won the day
Now they are mournin'
For all time a-lilting
The flowers of the forest
Are all a' wede away

[Cubdriver]

A few pictures of the Dana 5330.  It definitely needs some work - applying an input voltage gives no corresponding reading, and it randomly drifts around.  It's mid-late '72 vintage, so it may well need filter caps for starters.  It's a bare bones version, DC voltage measurement only.  The AC and resistance selectors are locked out and there is no AC/ohms circuitry in the measurement section.  At least all the nixies appear functional.  Into the queue it goes.

Lab Cat has brushed upon it and granted his purr of approval:








-Pat

[bd139]

Some good stuff on this thread this week 

Getting fired up to refurb the 6286A metering circuit this morning ... heathy (hahaha) breakfast first

[BU508A]

Some good stuff on this thread this week 

Getting fired up to refurb the 6286A metering circuit this morning ... heathy (hahaha) breakfast first

(Attachment Link)

Seems, you've recovered well from the flu?    Well, then go ahead with you breakfast, it is all yours. 

[bd139]

Bingo. Feeling much better. Dismayed at the things I missed on eBay though 

On positive note, credit card balance is zero now 

Thinking of going for the 34401A with the bust AC listed on eBay here.