Test Equipment Anonymous (TEA) group therapy thread

[0culus]

My newest toy arrived the other day.  It's displaying the dreaded YTO unlock error that is apparently common to the breed, but some online searching indicates that this is often a result of bad caps causing the YTO drive voltages to be out of spec.  I'd initially wondered why the spec an section was made 'upside-down, but now realize that's so it can be operated on while both pieces are still attached to one another.

Unfortunately, I need to deal with a broken ball joint on my friend's car tomorrow, so lord only knows when I'll get to this...

Fun, fun!!!

-Pat

Awesome! If you go search on youtube there are a couple of different people showing the repairs. I want to get a really nice 66B...I have a 66A but it's severely gimped in terms of GPIB functionality compared to the 66B. Yours looks to be in great shape! 

Thanks!  I got it from an ebay vendor in New Hampshire that I've had good luck with.  Their shipping, while not dirt cheap, is fast, and the items are very well packed.

The video I watched the other night was put up by a guy named Kerry Wong.  My fingers are crossed that this will be something relatively minor.  I may need to do some monkeying with the display, too, as the text seems dim relative to the rest - I need to turn the brightness up to the point where the trace starts blosing out before the text shows up.  I figure there is likely a balance or separate brightness control hidden in it somewhere that needs a tweak.  Will need to dig further into the display before tweaking anything, though, so as not to knock things out of whack with ham-fisted twiddling.  The YTO repair will be the first order of business, though.

-Pat

When you open the display unit (top cover; the entire unit was designed so it can be serviced on it's side with the two halves attached together!), there will be a long PCB (or multiple PCBs, depending on revision; they combined the amplifiers into one board later on) along the left hand side of the chassis along the CRT housing. On this will be all the CRT adjustment pots. 

[0culus]

"Jammy Git" -hp- 3400A. I did a rough adjustment as it was pretty far off (cal sealed and dated due in 2004  ). Still need to work on flatness over the passband, but it's usable now.   

Bonus absolutely gratuitous RPN porn just to tweak certain people who know who they are.   





 

[tautech]

"Jammy Git" -hp- 3400A. I did a rough adjustment as it was pretty far off (cal sealed and dated due in 2004  ). Still need to work on flatness over the passband, but it's usable now.   

Bonus absolutely gratuitous RPN porn just to tweak certain people who know who they are.   

 

Shouldn't that moving coil meter be doing this:     

[xrunner]

"Jammy Git" -hp- 3400A. I did a rough adjustment as it was pretty far off (cal sealed and dated due in 2004  ). Still need to work on flatness over the passband, but it's usable now.   

Glad it worked out! 

[worsthorse]

med, what’s the sn on yours? mine is very early. i noticed the hat sink on yours is “manufactured” for example, while mine is clearly an addition.

003983.

i think mine is 000415 but i will check in the morning. i just got home from the airport and finding my bed is the first thing on my to do list. 

[mansaxel]

just to tweak certain people who know who they are.   

 

Do not forget that you've also added an iteration of "firing bd137's desire for a 427A"; with that subtle inclusion in the just-enough-focus-to-identify background. 

[Specmaster]

Something in my 7854 has decided to take an occasional dump to ground, and I've only managed to notice because the case shocked me earlier. As far as I can tell, there's no other faults occurring when this happens. It's only a mild shock as one would expect from an otherwise functioning device.  The fault exists regardless of what plugins I've got installed, so it's definitely in the mainframe itself. It does take around 30 minutes of operation before the fault manifests itself, and it's doing so fairly consistently.

I've never had to track down a "mild" fault such as this.  Anyone have any suggestions on how to tackle tracking down the bugger?

The power supply voltages and ripple were good last I checked, but I'll be checking them again at startup and once the fault manifests.

As for tracking down the fault to a particular board, I'm considering using a 7A22 in another mainframe with the negative input probe attached to the ground at the mains input and move the positive input probe around each board's ground test points to narrow the fault down to the board, then continue from there to find the bastard.

Does anyone have any ideas?

Am I reading this right? You're getting a shock off a supposedly grounded chassis? Correct??   

If yes you need to determine why your scope isn't grounded. Is there a problem chassis to ground prong on the power plug? Or do you have bigger problems with the lack of a ground on your mains wiring? You need to figure this out first.

I think, but not sure, that the EMI filter has capacitors in it tied between hot and ground. If you don't have the chassis grounded these caps could cause the chassis to elevate to a fairly high potential, sometimes as high as 80 to 90 volts. The current is real small but you might feel it. And if the caps are going leaky then the current will go up. And also this leakage current could damage other equipment.

Be safe. If you are getting a shock off the chassis of your equipment something is seriously wrong and you need to shut it down and determine ASAP what's going on. 

I agree 100%, somewhere you have lost the ground connection. In what manner are feeling this leakage, is it from the case of the scope or is it via the ground lead on the probe when connecting to the DUT?

If it’s the latter then you have still got a problem with the scope, possibly a bad connection between the BNC socket and scope chassis if so then the problem exists on the DUT.

If it’s not the filter caps going bad in connection poor grounding, then you need several meters connected the various supply rails with a min/max recoding ability to which rail is being dumped to the chassis periodically and go on a hunt to track down the part on that rail. This testing could be applied to both scope and the DUT but only the DUT would only be suspect if the shock is only felt on the probe lead.

[0culus]

just to tweak certain people who know who they are.   

 

Do not forget that you've also added an iteration of "firing bd137's desire for a 427A"; with that subtle inclusion in the just-enough-focus-to-identify background. 

 

Anyway, I couldn't sleep so I opened up the 3400A and did another adjustment pass. Since I don't have the recommended meter calibrator device, I substituted my HP 3325B, which is well adjusted and has an excellent OCXO installed. In order to get it to come in, I had to modify the cal procedure slightly and use the feed thru termination for the entire process due to the impedance characteristics of the 3325B. After making that change, the 3400A came right into adjustment. It's bang on in all the ranges I am able to test without a HV ac supply. 

[nfmax]

Nice collection there  . Plenty of HP goodies 

OK so it's not all HP - some of it is Agilent or Keysight...

[EV]

More HP PRN! 

[VK5RC]

Ooooooooooh, I like it!

Edit, here is some of my rpn stash, I have a 41C collection - printers, wand, plug ins. HPIB IF.
Quite a few 41s with the battery connection roo**d but most work.

[tggzzz]

Ooooooooooh, I like it!

Edit, here is some of my rpn stash, I have a 41C collection - printers, wand, plug ins. HPIB IF.
Quite a few 41s with the battery connection roo**d but most work.

I like the concept of including slipsticks in an RPN collection

[bd139]

Ahh the seeds of discord have been sewn 

Thanks for all the RPN porn 

[VK5RC]

I wish I had my father's wooden sly-drool, it got tossed in the 80s unfortunately. But I have some of his circular calculators for fluids/gas - he was a civil engineer.

[EV]

Ooooooooooh, I like it!

Edit, here is some of my rpn stash, I have a 41C collection - printers, wand, plug ins. HPIB IF.
Quite a few 41s with the battery connection roo**d but most work.

Nice collection! I found more HP stuff.

[med6753]

Nixiefreqq is gonna have a stroke when he sees all this. 

[tggzzz]

I wish I had my father's wooden sly-drool, it got tossed in the 80s unfortunately. But I have some of his circular calculators for fluids/gas - he was a civil engineer.

I have my plastic one from the early 70s, contemporary with this construction. Both are still in working order

I even made a wooden one, from wood moldings and the scale from log graph paper

[tggzzz]

Nixiefreqq is gonna have a stroke when he sees all this. 

I bagsie first dibs on his test equipment

[beanflying]

Posing RPN twaddle is starting to look like the next Planking fad ....... Stop it before you go blind 

[med6753]

Posing RPN twaddle is starting to look like the next Planking fad ....... Stop it before you go blind 

 

[med6753]

I know it's a lost cause but at least put on a brave face before being shot down in flames. 

[VK5RC]

I have dibs on b-f's gear, he is in the same country. But I am way too lazy to roast my own coffee - I will pass on that!  "Enter"

[EV]

My fist calculator was like this:
https://dopecc.net/calculators/ime/ime86s/

It had 16 nixie digits, 4 memory places and square root. 

[tggzzz]

I know it's a lost cause but at least put on a brave face before being shot down in flames. 

Not to worry, I've solved your problem...

[beanflying]

I have dibs on b-f's gear, he is in the same country. But I am way too lazy to roast my own coffee - I will pass on that!  "Enter"

All things should be = and in balance. Enter is not a logical operator 

Being LAZY is using commercial wraps in tonight's dinner instead of making my own dough for the Souvlaki's . BURP 

Healthy 'junk food'