Test Equipment Anonymous (TEA) group therapy thread

[med6753]

First look inside the 485 PSU. This is the Inverter board. And guess what....there IS life in the supply. Now that I have the covers off I can hear the supply "ticking" and a little neon bulb in the lower left is flashing. That means there's a short in one of the supply voltages. I may get lucky. Good chance it's a shorted tant.

More later.

[Brumby]

And now what comes is all your fault, you gave me the idea for a TEA hymn!

There were probably several members who have had passing thoughts about this song where a certain appropriateness was felt, but it was officially adopted as the TEA Anthem a few months ago.  (Refer to the original post of this thread.) 

I was toying with the idea of writing some custom lyrics, but was dissuaded.  Now you've done it, they will probably find their way up to that first post if there is sufficient approval.

[med6753]

Can I really be this lucky? I'm hot on it's trail.

Supply voltage resistance readings:

-9V   156 ohms
-15V  138.78 ohms
-5V    217 ohms
+50V 1.64K
+15V 0.57 ohms 

The +15V is shorted somewhere. Now I just gotta find it. Looking more and more like a shorted tant.

[TERRA Operative]

I have another question for the TEA hivemind.

I want to buy/build a shielded low-ish Thermal EMF cable with banana jacks at each end. Nothing to volt-nuttery, but something better than a couple multimeter leads.
I have seen Pomona make individual low EMF leads, but nothing as a single shielded cable (that I can see).

Anyone got any suggestions?

[tggzzz]

The +15V is shorted somewhere. Now I just gotta find it. Looking more and more like a shorted tant.

RTFM and pull the relevant combs. Don't pull those that will lead to rapid disappointment.

[Specmaster]

@BU508A That's really good, well done.

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[BU508A]

There were probably several members who have had passing thoughts about this song where a certain appropriateness was felt, but it was officially adopted as the TEA Anthem a few months ago.  (Refer to the original post of this thread.) 

I was toying with the idea of writing some custom lyrics, but was dissuaded.  Now you've done it, they will probably find their way up to that first post if there is sufficient approval.

Thanks, I wasn't aware of this, but it is quite obvious that somebody else had the same idea much earlier. 
Anyway, I had a lot of fun playing with all the words and learnt something new. 

Cheers,

Mounty (now playing lots of rock songs from the 70s and 80s)

[Specmaster]

No hypocrisy; I just MADE one of them 

Philips power supply for reference. Rather nice bit of kit. Literally everything on the board is made by Philips !



Edit: not once did I have to take the timebase out to get at the caps 

That is a thing of beauty, but cap is not a tant, and really doubt that you needed to make that spacer board because the new cap will be considerably smaller so a small dab of hot snot will be sufficient to support it [emoji848]

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[BU508A]

I have another question for the TEA hivemind.

I want to buy/build a shielded low-ish Thermal EMF cable with banana jacks at each end. Nothing to volt-nuttery, but something better than a couple multimeter leads.
I have seen Pomona make individual low EMF leads, but nothing as a single shielded cable (that I can see).

Anyone got any suggestions?

For the cable, I would go after something like this:

https://www.ebay.com/itm/273799295024


For the Banana plugs I would take these:
MC (MultiContact) Stäubli 4mm banana plugs
Example:
https://www.ebay.com/itm/202689458387


the hollow version of them:
https://au.rs-online.com/web/p/banana-plugs-connectors/0531453/

[bd139]

No hypocrisy; I just MADE one of them 

Philips power supply for reference. Rather nice bit of kit. Literally everything on the board is made by Philips !



Edit: not once did I have to take the timebase out to get at the caps 

That is a thing of beauty, but cap is not a tant, and really doubt that you needed to make that spacer board because the new cap will be considerably smaller so a small dab of hot snot will be sufficient to support it [emoji848]

Sent from my POT-LX1 using Tapatalk

It’s getting a direct descendent put in it which is a Vishay/BC 056 series. About same size and the best part of a tenner. Didn’t want to cut corners here.

Also can’t use hot snot in power supplies as it melts at a relatively low temperature.

ESR is way high on that as well which probably explains why the transformer is getting annoyed with it. Transformer has a thermal fuse in it which can be problematic. This is an artifact of the design because the entire rectifier and filter part of the unit is powered up the entire time it is plugged in as it is required for the battery pack option

[med6753]

The +15V is shorted somewhere. Now I just gotta find it. Looking more and more like a shorted tant.

RTFM and pull the relevant combs. Don't pull those that will lead to rapid disappointment.

I've already determined by pulling the appropriate combs that it is not the Sweep Board. And I've discovered that someone has been in here and determined same as me that the +15V is shorted. The filter caps and the tants in the supply itself show unmistakable evidence of being pulled and resoldered. So there was a Gorilla on the loose which figures.

Now I just have to determine where the +15V splits at the test point on the supply board and trace it out.

[bd139]

Good luck.

[med6753]

Yep, it's turning into whack a mole. 

[mnementh]

Damn unobtainium capacitors are causing me grief today. Got a weird ass 4 pin Mullard thing in this PM3217 that needs replacing. Decided to proceed with refurbing it anyway... thus:

   £14 for 50 off. Tempted to sell them over this side of the pond 

You’re wellll-commmme!!! 

Pikey capacitor adapter done. Kicad -> print on paper -> glue on PCB -> cut out -> mark holes with punch -> clean -> etch resist pen -> bake with heat gun -> etch resist pen -> bake with heat gun -> etch -> clean -> drill holes -> clean again -> solder on wires. I haven't put the actual capacitor on it yet as that doesn't arrive until Tuesday but the thing looks respectable so far I think. Copper wire was from some 450 ohm ladder line. Need to get some tinning crystals at some point.
These boards look less horrible when you tin them.         A lot for a single capacitor? Probably!

That is some proper ghetto-fab right there! I give it two claws up; waaaay up! 

mnem
*TnkerDwagon-approved*

[mnementh]

Hold it. Back up the bus.    Am I sensing some hypocrisy here??  I was advised NOT to recap the PSU on the 465B unless I obtained these:     I even had the peanut gallery (mnem) join the fray and dumbassery remarks were exchanged. So I was persuaded (shamed) into obtaining these spacers.

So........wut's the deal???   

Nope. You got it right; especially after my hearty approval of the “pikey capacitor disc”. 

But in my defense; I would STILL like to see the ones he designed produced properly with mask, etc.

However, it is unreasonable to expect him to do a whole run, even a small one, for a single unit.

It’d be different if you could just click on a kit for $10 like your case; would you really make 5 of those by hand when somebody else already did the thinking and all the hard work for $2 each?

mnem
 

[bd139]

Indeed I’d have liked to have done a run for this but I worked out that I’ll just end up with more crap in a box somewhere and a 20 day wait.

Also on a positive note I may have managed to find a PM3215 parts mule. This is the same scope but without the DTB. Attenuators are the same. On this one the power supply switching transformer is toast. Only problem: it’s in bloody Ipswich, a 250 mile round trip, and no delivery possible.

[Kosmic]

I have another question for the TEA hivemind.

I want to buy/build a shielded low-ish Thermal EMF cable with banana jacks at each end. Nothing to volt-nuttery, but something better than a couple multimeter leads.
I have seen Pomona make individual low EMF leads, but nothing as a single shielded cable (that I can see).

Anyone got any suggestions?

CAT6 network cables are cheap and working well.

[tggzzz]

+15V 0.57 ohms 

The +15V is shorted somewhere. Now I just gotta find it. Looking more and more like a shorted tant.

Those blue electrolytics aren't original.

Look at c911 and the (two?) other 15V tants on the 13V rail, and look at the 86ohm resistor. That resistor is the only thing separating the 13V rail from the 15V rail, and I've seen it become untenably hot.

[med6753]

I'm at a temporary impasse with this 485. I'm going to have to pull this Sweep board in order to figure out the +15V distribution. Unlike the manuals for the 465/475 there are NO instructions for isolating the supply voltages from each board to assist in short determination. And the +15V runs all over the place. So I'm going to have to physically trace it out. But one thing in FAVOR of this 485 is the boards are modular. So pulling the sweep board is going to be a pretty simple task. But I have other things I need to do today so this is getting put aside for now. But I'm confident I'll snag it. 

   

[Kosmic]

I'm at a temporary impasse with this 485. I'm going to have to pull this Sweep board in order to figure out the +15V distribution. Unlike the manuals for the 465/475 there are NO instructions for isolating the supply voltages from each board to assist in short determination. And the +15V runs all over the place. So I'm going to have to physically trace it out. But one thing in FAVOR of this 485 is the boards are modular. So pulling the sweep board is going to be a pretty simple task. But I have other things I need to do today so this is getting put aside for now. But I'm confident I'll snag it. 

So many components! I'm going to have tons of fun fixing mine I'm sure

On the bright side look like sourcing replacement parts should be easy. Is there a lot of custom parts in the 485 ?

[bd139]

Need a Fluke 8012A in low ohms mode. That is great for hunting tants. 2 ohm FSD.

[med6753]

I'm at a temporary impasse with this 485. I'm going to have to pull this Sweep board in order to figure out the +15V distribution. Unlike the manuals for the 465/475 there are NO instructions for isolating the supply voltages from each board to assist in short determination. And the +15V runs all over the place. So I'm going to have to physically trace it out. But one thing in FAVOR of this 485 is the boards are modular. So pulling the sweep board is going to be a pretty simple task. But I have other things I need to do today so this is getting put aside for now. But I'm confident I'll snag it. 

So many components! I'm going to have tons of fun fixing mine I'm sure

On the bright side look like sourcing replacement parts should be easy. Is there a lot of custom parts in the 485 ?

Yea, it's definitely busy in there. Haven't really paid much attention to individual parts yet but I think it's a safe assumption that the vertical board has lots of custom parts.

I just found in the manual a schematic of the total power distribution. That is going to be a big help in tracking down the +15V short. 

[med6753]

Need a Fluke 8012A in low ohms mode. That is great for hunting tants. 2 ohm FSD.

No, what I really need is my head examined. 

[bd139]

I think we all need that 

[worsthorse]

There's a reason I still have an old CF-29 Toughbook under the bench. XP stable like the rock of Gibraltar, serial and parallel built-in, backlit keyboard and touchscreen. Yeah, the screen's a little dim and yellow... but If I can't fix whatever I'm connecting to with it, I can beat the damned thing to death with it. 

mnem
*toddles off to ded*

They sure don't make stuff like they used to....for me the sweet spot with Windows was 7 Pro. Ran that for years on my now-dead gaming rig, till new games demanding new directX versions appeared.

I wish Thinkpads were actually as nice as they were when IBM owned the line.  This one is pretty much ok, but it's a shadow of the old ones.

Since my need for speed wrt computing power is rather low, and lots of software I run was written in the win7 era, I have four Dell business class machines I use for radio and electronics related tasks. Windows 7 Pro is reliable, not overburdened with "improvements" and does not participate in the "you will update your computer os now or you will stop using your computer" paradigm that Microsoft insists is for my own well-being.  I am not quite sure what I am going to do when official support stops next year but for now, good enough!

And oh yeah, there's the CF25 running DOS 6.22 and WfW for the really old software that I still keep handy.