Test Equipment Anonymous (TEA) group therapy thread

[med6753]

I'm putting my 4070A in the Cupboard of Doom.[/i] I've managed to toast CAD$34 worth of AD811AN op-amps and still no closer to grokking its major malfunction.     Maybe I'll buy a big bag of cheap AD811s from China; maybe I'll look for a cheaper and/or more durable alternative part.     

Someday. For now it's time to put the ol' icebag on my junk and move on with my life.

mnem
 

Only a cupboard of doom? Amateur. I have a closet of doom. 

News flash: If I crank the Hakko up to a Venusian surface temperature of 825 degrees F (440 C) it easily works Tek ceramic strips. But at that heat level I don't expect the tips to last very long. 

[AVGresponding]

heard one today for your scrabble fans:
Musikpodcastschlummertastenabschaltautomatik.

Scrabble games in German must be a high scoring affair!   

Maybe I'll buy a big bag of cheap AD811s from China; maybe I'll look for a cheaper and/or more durable alternative part.     

mnem

You know perfectly well that if you do that, you'll receive a big bag of reject LM741s marked as AD811s, or worse...



Sorry I missed Discord, sounds like it was a laugh riot...   

As I mentioned in a previous post I was engaged in a Star Trek binge, in amongst guild activities in the shitshow that is PWI, and running ludicrous but essential errands in Elite - Dangerous.

I already had the bad karma from non-attendance; my takeaway was an hour late and not great...

[bd139]

Yeah I’d just buy the ones from mouser. About £8 a pop but will actually work.

As for discord non attendance that sounds like a glorious evening apart from the takeaway problems. I nearly forgot myself. I was busy whining to my eldest about how crappy London looks in Watchdogs Legion. They compressed it terribly.

[Saskia]

apologizings for not being as entertaining as usual. I will try to improve.

Today is:
last day out to that burger joint in Wiesbaden before they are forced to close.
grab another streacom case to build audio streamer from parts I still have lying around.
clean up bench
lug 12 of those raaco thingies up the stairs.

[med6753]

Boy did I need this victory after some recent Fubar's. The HV issue on the Type 310A is FIXED!  I changed the four .01uf/2KV caps on the secondary side of the HV transformer and bingo....now works. In fact, I had TOO much HV. Was sitting at -2200V. I was able to adjust it down to spec -1675V.

These are the 4 suspects.



So, which one is bad? This one. Has leakage of 9.05MEG. First time I've seen a ceramic capacitor develop leakage.



Looking good! 



But I do have a new issue. On lower vertical ranges and no signal I have this ripple on the trace. Should be straight forward to track down.

[bd139]

Not the first time I've seen that. They had those capacitors in the very early 465 HV circuits, shortly replaced by the red shiny ones. One of the very first ones I had ended up with them replaced.

[Specmaster]

apologizings for not being as entertaining as usual. I will try to improve.

Today is:
last day out to that burger joint in Wiesbaden before they are forced to close.
grab another streacom case to build audio streamer from parts I still have lying around.
clean up bench
lug 12 of those raaco thingies up the stairs.

I don't understand what you mean, I enjoyed myself last night, enjoy chatting with you. The problem was I think that it was just so quiet on discord generally last night, with more participants on it, there is nearly always something to talk about, humour bounces of different people in different ways, so stop thinking that you were not entertaining or else I'll be forced to popping round and taking those raaco thingies off you 

[Specmaster]

Not the first time I've seen that. They had those capacitors in the very early 465 HV circuits, shortly replaced by the red shiny ones. One of the very first ones I had ended up with them replaced.

Strange, I've thought of ceramics as being infallible and normally do not even bother to check them.

[med6753]

Not the first time I've seen that. They had those capacitors in the very early 465 HV circuits, shortly replaced by the red shiny ones. One of the very first ones I had ended up with them replaced.

Definitely the first time I've seen it. Surprising that 9MEG of leakage was enough to kill the HV.

Going to let the scope cook for a while before going after that ripple issue. After fixing that I should be able to do a final calibration.

[Robert763]

That's 9 Meg of leakage at a couple of of volts. At a kV or more the leakage is likely to be much higher. Need a Megger or Genrad Megometer to tell.

Ceramics do fail. Many years ago I repaired boards with hundreds of TTL chips and a 0.1uF ceramic per chip. Used to get those go short and were a bugger to find.   

[med6753]

Not the first time I've seen that. They had those capacitors in the very early 465 HV circuits, shortly replaced by the red shiny ones. One of the very first ones I had ended up with them replaced.

Strange, I've thought of ceramics as being infallible and normally do not even bother to check them.

Yea, me too. But I guess when you're dealing with HV EVERYTHING can be suspect.

[bd139]

Never underestimate ceramics. They are temperature and moisture sensitive and sometimes microphonic. I've noticed as well that the NP0 ceramics can degrade over time as well 

[med6753]

That's 9 Meg of leakage at a couple of of volts. At a kV or more the leakage is likely to be much higher. Need a Megger or Genrad Megometer to tell.

Ceramics do fail. Many years ago I repaired boards with hundreds of TTL chips and a 0.1uF ceramic per chip. Used to get those go short and were a bugger to find.

Yea, after I wrote that I came to the same conclusion. That's 9MEG of leakage at a few volts and most likely much higher leakage (lower resistance) in circuit. I don't have a megger so I can't verify it. 

[shakalnokturn]

I've seen a few, the most obvious being the blue ones that would have a brown burn on the side in Philips CRT TV's.
The hardest ones to suspect are when things still work although not quite right.
Recently one of my head lamps kept discharging its 18650, it was a leaky 10μF MLCC, also a 3kV disc in a Hameg scope that would mess the blanking up, only within a certain temperature range.

[Specmaster]

Never underestimate ceramics. They are temperature and moisture sensitive and sometimes microphonic. I've noticed as well that the NP0 ceramics can degrade over time as well 

I did have a microphonic one years ago but nothing since. The only time I start to check them is once I think that I've eliminated everything else to no effect.

[med6753]

Never underestimate ceramics. They are temperature and moisture sensitive and sometimes microphonic. I've noticed as well that the NP0 ceramics can degrade over time as well 

I did have a microphonic one years ago but nothing since. The only time I start to check them is once I think that I've eliminated everything else to no effect.

That's basically what brought me to that point. It was either those capacitors or the HV transformer was NG. I had checked everything else.

Edit.....it was C722, C731, C732, C733

[mnementh]

I'm putting my 4070A in the Cupboard of Doom. I've managed to toast CAD$34 worth of AD811AN op-amps and still no closer to grokking its major malfunction.     Maybe I'll buy a big bag of cheap AD811s from China; maybe I'll look for a cheaper and/or more durable alternative part.     

Someday. For now it's time to put the ol' icebag on my junk and move on with my life.

mnem
 

Only a cupboard of doom? Amateur. I have a closet of doom. 

News flash: If I crank the Hakko up to a Venusian surface temperature of 825 degrees F (440 C) it easily works Tek ceramic strips. But at that heat level I don't expect the tips to last very long. 

I think you're forgetting the 32' long Trailer of Doom. 



Ummmm... the whole point of the silver solder is that it works at a lower temperature; this prevents thermal fracture of the ceramic strips, and it prevents the copper doping in the ceramic strip which you're soldering to from burning off and ruining the strip.   

What you need to work with this stuff safely is more heat (higher wattage, more thermal mass, larger tip with larger covalent area), not higher temperature.

Think the difference between a propane rosebud torch and this:   

mnem
 

[mnementh]

Not the first time I've seen that. They had those capacitors in the very early 465 HV circuits, shortly replaced by the red shiny ones. One of the very first ones I had ended up with them replaced.

Strange, I've thought of ceramics as being infallible and normally do not even bother to check them.

Intermittent or weird HV problems, they're the FIRST thing I look into. Too many crunked-out HV doubler/tripler circuits under my belt, I suppose. 

I've resurrected a few old TVs/scopes by taking all the doubler caps & diodes out, washing the nicotine coating off with alcohol, and reinstalling. Just that amount of leakage was enough to FUBAR the whole thing.

mnem
tzzzt.

[med6753]

Ummmm... the whole point of the silver solder is that it works at a lower temperature; this prevents thermal fracture of the ceramic strips, and it prevents the copper doping in the ceramic strip which you're soldering to from burning off and ruining the strip.   

What you need to work with this stuff safely is more heat (higher wattage, more thermal mass, larger tip with larger covalent area), not higher temperature.

Think the difference between a propane rosebud torch and this:   

mnem
 

Yes, I understand all that and I'm willing to accept the risks of what I'm doing. I try to limit soldering DIRECTLY to the ceramic strip by cutting out the old component leaving a short lead length and then hook and secure new component and then solder the leads. But where I have gone directly to the strip so far it's golden.   

[mnementh]

Maybe I'll buy a big bag of cheap AD811s from China; maybe I'll look for a cheaper and/or more durable alternative part.     

mnem

You know perfectly well that if you do that, you'll receive a big bag of reject LM741s marked as AD811s, or worse...

In all honesty, I did toy with the idea of buying a bag of cheap LM741As as sacrificial elements to use until I figure out the thing's major malfunction; just keep the frequency low until I find the actual problem. Higher voltage differential tolerance, higher TDP within operating envelope. And I've already socketed the damn thing for troubleshooting purposes.

But the difference in slew rate and nonlinear gain of the 741... thing would probably self-oscillate until it caught fire. 

Hey... there's more than one way to Widlarize a piece of equipment. 

mnem
hmmmm...   

[Kosmic]

They fucking canceled Halloween. The boi dressed up as Ichigo from Bleach; did a damn fine job too. But not even a trunk or treat nor nuthin' fer him ta go to. 

mnem
*p00t!*

Did you really think trick or treating was gonna happen? 

Did happen over here. I had around 75 kids coming I think. Distributed all the candies I had anyway.

I had to improvise a setup though. I tie-wrapped my fishing rod case (Big plastic tube) on the handrail to slide the candies to the kids. Also, since I'm a lazy bastard, I extended my rigging bell near the candy slide. So I spent the evening drinking Smithwick's beers and watching a movie. Only had to go outside when a kid was actually there 

[bd139]

741 wouldn't work. AD811 is current feedback.

[med6753]

Not the first time I've seen that. They had those capacitors in the very early 465 HV circuits, shortly replaced by the red shiny ones. One of the very first ones I had ended up with them replaced.

Strange, I've thought of ceramics as being infallible and normally do not even bother to check them.

Intermittent or weird HV problems, they're the FIRST thing I look into. Too many crunked-out HV doubler/tripler circuits under my belt, I suppose. 

I've resurrected a few old TVs/scopes by taking all the doubler caps & diodes out, washing the nicotine coating off with alcohol, and reinstalling. Just that amount of leakage was enough to FUBAR the whole thing.

mnem
tzzzt.

My father owned a TV repair shop in the early 1950's and his experience was most HV failures occurred during the humid Summer months which makes perfect sense. Back then you made house calls so he would show up with his tube caddy and Heath M-1 VOM. Open up the HV cage and observe the light show (arcing). Clean all the dust/dirt out and change out the 1B3GT HV rectifier toob. Done. Quick profit. Every once in a while it would also take out the driver Horizontal Output Tube. Back then that was one of the most expensive tubes in the TV. More quick profit. And on very rare instances would take out the flyback transformer. That meant pulling the chassis and back to the shop for replacement. And for the 1950's a big bill.

The Heath M-1 VOM is still in existence. My middle brother has it.

   

[mnementh]

741 wouldn't work. AD811 is current feedback.

Oh yeah... it has to regulate the gain response somehow, doesn't it...? 

mnem
 

[med6753]

They fucking canceled Halloween. The boi dressed up as Ichigo from Bleach; did a damn fine job too. But not even a trunk or treat nor nuthin' fer him ta go to. 

mnem
*p00t!*

Did you really think trick or treating was gonna happen? 

Did happen over here. I had around 75 kids coming I think. Distributed all the candies I had anyway.

I had to improvise a setup though. I tie-wrapped my fishing rod case (Big plastic tube) on the handrail to slide the candies to the kids. Also, since I'm a lazy bastard, I extended my rigging bell near the candy slide. So I spent the evening drinking Smithwick's beers and watching a movie. Only had to go outside when a kid was actually there 

I have no idea what happen here, nor do I care, because I never get any T/T anyway.