Test Equipment Anonymous (TEA) group therapy thread

[Tomorokoshi]

HP 120B update

So I stole a 6AQ5 and 12AU7 from on of the type 515.

Result : no HV ! I used my HV probe and probed directly at the connector that plugs at the back of the CRT. I get ZERO. No HV-ing going on, not a sausage 

Bad tubes ? As I said it's not like I have a zillion to try out ! 

So that's were I am now, trying to probe on that HV board to see if I can troubleshoot it, hoping my tubes are good and there is something else wrong with it... hopefully not a burned HV transformer 
Problem is that access to that board is not ideal. I can get to its bottom because of the way it's installed in the chassis. I can only probe the top, and that's not easy as most interesting components are by the read panel. Hard to get probes down there, or see what you are doing really. Also, the caps mostly can't be probed as they sit flush on the board, their terminals are not exposed 

You could swap the HV control tube with one of the others in the 120B, the other might be a problem as it's the oscillator tube. Also check the solder joints on the tube sockets, had many bad joints from thermal cycling, more of a problem with the higher power tubes.

David

Swapped the contorl tube / 12AU7 no luck.

Swapped the oscillator tube / 6AQ5 ... well no I can't. Both the one in my second type 515 and my type 310A which I resorted to opening up out of desperation, are cooked... 100% black inside. I tried them anyway, no luck.

So basically the 6AQ5 I pulled from my first 515 is the ONLY such tube I have here that's not black... it's crystal clear and I can see that at the very least, it lights up. Better than nothing I guess.

So I will or a new tube or two very soon but of course that will take time to get to me. So in the mean time I will pretend that my tube works and try trouble shooting the board.

- I checked all power supply going to that board, board does get all the supplies it needs, so that's good. That includes the unregulated 420V that goes to the primary of the HV tranny. Yes tranny again, transformer this time not transistor 

- Zero oscillation going on : HV probe says zero volts on the secondary side, and when I scope the board, I see only DC voltages, zero sign of activity.

- I measured DC voltages as indicated on the schematic below, around the 2 tubes, i.e 3 elements : pentode and x2 triodes.  DC levels are 100% completely wrong. See measured levels indicated in red. So if we look at the two triodes : both are fed with 300V, and both are supposed to have about 90V on their anode. But, in my case not at all. Get near zero (2.8V) and the other near B+ (300V and the rail is at 304V).
So one Triode is conducting like mad, and the other is not conducting at all, and it sits like that, stable.
As for the Pentode / oscillator tube, it's control grid sees 0.8V instead of negative 123V !
so no wonder it does not work... now the problem of course is that it's a close-loop system, so no way to know what element in the loop is causing the entire loop to fail.


So now what to do...

Checking solder joints yes but not easy as pulling the board from the chassis looks like it will be a major tear down, looks quite involved....

Short of having another oscillator tube to swap, I will make the hypothesis that it's either bad joint as you said, or some passive component that just died.
One thing that might point in that direction is that now I think of it, the brightness control used to have bugger all effect on bruightness. It had as I said effect on the pitch and loudness of the arcing sound if that's what it was, but it did not have much effect on brightness.. it was always very bright.
So right there, we can say that some component or joint in the HV board was not good...

Wish me luck.....

Check:
1. Resistance across R304.

2. Resistance from V301 #1 to V301 #6.

[mnementh]

That, and the fact you can't just ignore the fuel delivery system for the life of the vehicle like most folk do with gasoline powered vehicles;

Your situation may differ but in most of the civilised world, motorcars have to undergo regular inspections, usually at 1 or 2 year intervals, by authorised organisations. This includes a thorough check of LPG or CNG systems and tanks.

Thankfully, this kind of event is quite rare but if vehicle fuelled by LNG / CNG catches fire, you need to get plenty of cooling water squirted over the tank and the fire knocked back quickly to prevent a bleve from happening.

Belgium and the Netherlands have large numbers of privately owned LPG vehicles on their roads. Many French towns have been operating fleets of busses running on natrual gas for decades. I've never heard or read of any BLEVE over there.

Aaaand now we've gone recursive; right back to my arguments a while back saying that hydrogen as a motor fuel was just like CNG, in that aside from a few statistical outliers, it really is only appropriate for fleet use as safely fueling a vehicle requires training to use a high pressure coupler carrying a highly explosive gas, and requires an operator who isn't a complete moron like at least 50% of the motoring public.

The same argument I just made a moment ago. 

And that's EXACTLY what I'm talking about. I've worked as a mechanic in 3 different states; aside from making sure the gas cap works properly, THE FUEL TANK AND PLUMBING ARE NOT AN INSPECTION ITEM. And I wouldn't be surprised if that was the case where you are as well.

Yeah, sure if you notice something egregiously dangerous, like fuel lines dripping fuel, you fail it. But it is not an item you specifically inspect like tire tread, brake linings or windshield wipers.

CNG is inherently more dangerous, and your safety oversight organizations know it. Why are we even arguing this... AGAIN...?

mnem
 

[mnementh]

@Vince: Luck!

mnem
 

[Saskia]

lng, cng and lpg systems are subject to very regular and thorough inspections and leakage checks.
filling up is really not difficult, if you are not a complete dumbass. don't talk about the theoretical problems if you have zero real life experience with that one.
can we skip that topic  now ?

[TERRA Operative]

This just in!

Contained energy is explosive and dangerous if not handled properly!

More at 6, now the weather.

 

[Saskia]

with the energy contained in a cat you could heat Norway for a year. Theoretically
cats are dangerous, they plan to dominate the planet by purring us into submission.
point proven.

[TERRA Operative]

And a Mars Bar contains about five times the energy of a hand grenade, but most people would rather chew on a Mars Bar.

[Robert763]

if none of them were from CNG then why do you quote them ? CNG tanks have a service life of 15 years which may be extended with proper inspection to 20.  biannual inspection is mandatory.
I had a petrol car ( Audi)) explode from under me, barely made it out. no LPG or CNG car has done this to me.

None of the BLEVEs are from CNG because you can't get a BLEVE from CNG. The L in BLEVE is LIQUID. CNG is not liquid.
LPG BLEVEs are pretty impressive though...

EDIT. You can of course get a BLEVE with petrol or Diesel if it is heated in a sealed container.
One advantage of CNG and Hydrogen is that leaks dissipate naturally. They don't collect in low lying areas waiting to catch you out and in the case of petrol and diesel contaminating the ground, killing flora and fauna.

[med6753]

Mini-BLEVE 

[Specmaster]

with the energy contained in a cat you could heat Norway for a year. Theoretically
cats are dangerous, they plan to dominate the planet by purring us into submission.
point proven.

LMAO Nooooo everyone one knows its not cats but Pinky and the Brain who are trying to dominate the world 

[Specmaster]

Mini-BLEVE 

Nah, that is just a PRV venting to the outside world. 

[Saskia]

with the energy contained in a cat you could heat Norway for a year. Theoretically
cats are dangerous, they plan to dominate the planet by purring us into submission.
point proven.

LMAO Nooooo everyone one knows its not cats but Pinky and the Brain who are trying to dominate the world 

I do know the Pinky and the Brain, need to get my inspiration from somewhere.
Problem is: to release the vast energies contained in a cat, an anti-cat won't do. you need a portable spinning singularity. Having that nearby does not sound as a feasible or desirable idea.

Some mixed news:
Fever is down, inflammation slowly subsiding, blood sugar level dropping. Skin itching like eff though. I'll spare you the details.
NMR revealed no prolapsed disc (good), but a worn vertebra joint which is swollen and impinching.  No surgery indication though. Still on sick leave, checkup on Monday. Swell. Not taking the cortisone pills due to high blood sugar levels (Doc said: if you cannot bear it, but measure blood sugar. If blood sugar too high, don't take cortisone if possible ...)


Keithley 7001 arrived. front in very nice condition, handle and feet missing, rear frame slightly effed.
Did not power it on yet. Question: do Keithleys have multi range PSUs ? Or do I have to set something ?
I would of course be able to search for a manual, but if someone knew the answer right away, that would be perfect.

[Specmaster]

if none of them were from CNG then why do you quote them ? CNG tanks have a service life of 15 years which may be extended with proper inspection to 20.  biannual inspection is mandatory.
I had a petrol car ( Audi)) explode from under me, barely made it out. no LPG or CNG car has done this to me.

None of the BLEVEs are from CNG because you can't get a BLEVE from CNG. The L in BLEVE is LIQUID. CNG is not liquid.
LPG BLEVEs are pretty impressive though...

EDIT. You can of course get a BLEVE with petrol or Diesel if it is heated in a sealed container.
One advantage of CNG and Hydrogen is that leaks dissipate naturally. They don't collect in low lying areas waiting to catch you out and in the case of petrol and diesel contaminating the ground, killing flora and fauna.

Technically, you are right, it is the liquid that in a fire situation could possibly boil (this would to a large extent depend on where the fire was in relation to tank position) and release more gas as a result of boiling, increasing the pressure to such an extent that it could rupture the tank, thus spilling out high pressure gas and hot liquid fuel, making air-fuel bomb which explodes with tremendous force. I suppose you could consider it similar to the Thermobaric bombs (vacuum bombs) that Russia is said to have been using in its war with Ukraine.

But equally nobody would want to in the way of the blast of fire that comes from the pressure release valve when it happens to open to reduce the internal pressure, it becomes a high pressure flamethrower as witnessed in the first video posted earlier and is capable of destroying anyone or thing in its path.

Petrol (gas for the Americans) and diesel are not contained in a sealed container on a vehicle as there are special vapour locks / vents to allow a certain amount of breathing, plus there is on all the fuel systems I have ever soon some plastic / rubber flexible tubing in the pipeline and filler neck which would melt and vent long before the tank would rupture. Added into this, most fuel filler caps these days also made of plastic and would melt as well. So a Bleve from a petrol or diesel powered vehicle's fuel tank I should think are extremely unlikely. Fuel carried in a steel unvented can is of course is another thing, but who in their right mind would keep cans of fuel in their vehicle these days.

[Saskia]

been there had that with a petrol Audi. so much for the extreme unlikelihood.

[Peter_O]

Some months ago I rescued this litte guy.
Now I want to bring it up to speed.



The friction wheel is missing at the frequency dial.
I'm searching for clear pictures. Best I could find so far is the video of Curious Marc:
[url]https://youtu.be/4TFSBH4AEmg?t=797]https://youtu.be/4TFSBH4AEmg?t=797

From That it seems to be just a disk with some kind of rubber at the front that presses against the scale wheel from behind.
I plan to print a wheel, cut a rubber disk from 'something' and glue it.

Any better ideas or better pictures?

[TERRA Operative]

Looks similar to the setup on my 334A Distortion Analyzer. I'll take some pictures later.

[HighVoltage]

Opportunity called and I did it again.... this time 4 broken 34401A.
All without case cover, no display window and not working, but cheap !

 

[HighVoltage]

... and one broken Keysight branded 34410A was also part of the haul.
This one is working alright in DC but not AC, never had that problem before.

 

[factory]

Looks similar to the setup on my 334A Distortion Analyzer. I'll take some pictures later.

They are moulded onto the shaft, with a spring pushing it against the main dial, this is from my 333A distortion anaylzer, the one with the smashed meter.


Could also have a look at the 3310A here, that one is probably slightly smaller than the wheel on the 333A.

David

[Tomorokoshi]

Any better ideas or better pictures?

Those are useful. I used mine in VCO mode to simulate part of a 4-20mA device.

Try plumbing washers or o-rings.

Note that the rubber washer is behind the wheel. Make sure both knobs spin freely, or the washer won't have enough friction to move the main control.

[tggzzz]

The friction wheel is missing at the frequency dial.
I'm searching for clear pictures. Best I could find so far is the video of Curious Marc:
[url=https://youtu.be/4TFSBH4AEmg?t=797]]https://youtu.be/4TFSBH4AEmg?t=797]https://youtu.be/4TFSBH4AEmg?t=797

From That it seems to be just a disk with some kind of rubber at the front that presses against the scale wheel from behind.
I plan to print a wheel, cut a rubber disk from 'something' and glue it.

Any better ideas or better pictures?

That is basically correct.

It is a hard plastic, as shown below and in factory's picture. The "ledge" looks as if it aligns with the edge of the dial, but I'm not convinced of that, neither am I convinced it is important.

Internally a bronze leaf spring gently pushes the knob's stem outwards to provide gentle pressure against the dial. The light pressure ensures it slips easily when the main dial is rotated. That might not work as well if it was "sticky" rubber.

Looking at your picture, it might be worth considering seeing if a thick rubber tap washer would fit into the knurled recess visible in your stem, e.g. https://www.amazon.co.uk/Assortment-Rubber-Washers-Basin-Shower/dp/B07Q3WZQHK

[Brumby]

I'll only make this one comment on the subject...

The "flamethrower" bus demonstrated a properly functioning safety feature: the pressure relief valve.  This is to ensure overheated vessels release their contents in a controlled manner - not explosively.  You get a flamethrower, not a mushroom cloud.  Comparisons to completely sealed containers is completely irrelevant.

Motor vehicle LPG tanks in Australia also have such a valve, for exactly the same reason.  I know - I've worked on them.

[mnementh]

lng, cng and lpg systems are subject to very regular and thorough inspections and leakage checks. filling up is really not difficult, if you are not a complete dumbass. don't talk about the theoretical problems if you have zero real life experience with that one.
can we skip that topic  now ?

It is inherently more dangerous because it is under pressure. No matter what you say to the contrary, the fact that all these systems have to be frequently inspected, and that you have to have training to operate the filling station by definition proves that point.

You just stated the point I'm making: The average motorist IS a complete dumbass; or at least enough of them that you don't dare allow any fueling station be operated unattended. Imagine the corner gas station in the US with a safety-trained attendant for every fuel pump. The notion is ludicrous. 

I do have real-life experience with more than one kind of pressurized fuel. I have worked in a bus garage where they ran CNG and LPG, and actually know the LPG hardware pretty well. I have have done several LPG conversions, and I took the training to operate their backfill LPG filling station. I also know the difference between high-pressure, low-pressure and non-pressurized fuels.

I have also worked the cascade systems filling air tanks for our Scott packs at the Fire Dept; these operated at 4500PSIG, but newer systems operate at 5,500 PSIG to give the firefighter a few more minutes air. We also had Dräger rebreather packs, but those tanks were managed by an outside vendor. I was, however, trained and certified to service and maintain the Scott SCBA system while I was at the Dept.

Working steel, I have handled high-pressure 0₂ and low-pressure acetylene on a daily basis. I have seen first-hand the amount of energy just the pressures involved can deliver: An 0₂ K tank knocked over in my high-school metal shop by a vendor operating a forklift hit just right to snap the valve off; the pressure in that tank was enough to propel it through a sand-casting pit, across the shop and embed itself 6 inches into a concrete wall. Old man Kirsch made sure every student got to see the damage as a warning before they cleaned up the mess.

CNG tanks operate at ~3600PSIG; almost twice that of a welding O₂ tank. And the fuel is highly volatile. LPG is dangerous enough; it is low-pressure, just enough to keep it in a liquid state, but CNG is exponentially more dangerous because of the pressures involved. I certainly don't trust the average motorist to safely handle either.

I spent my time searching for "the better fuel" to make ICEs safe for people and safe for the future. There isn't one.

Seriously... the way you talk about it, you simply have not got appropriate respect for just how dangerous this stuff is, and the bottom line is it's all still fossil fuel, and is still burning stuff to make our energy, so it cannot be sustained.

mnem

[Saskia]

well, the training you need for pumping cng is about the same as lift handle, put gizmo over filling gizmo, turn lock push button.the filling stations are unsupervised credit card driven terminals without any staff.if lifting the handle and putting it over the nozzle plus pushing a button is too complicated the folks in  question should not be driving.
I had 80 l of petrolexplode in that Audi I was referring to.  ai don't t see the point you are trying to make. there are more petrol cars burning than lpg/cng cars burning  so what is the hubbub about ?

[paschulke2]

Any better ideas or better pictures?

Two pics of my 3310A are attached. The plastic is the same as the plastic of the knob itself. No rubber. The shape is slightly conical and the complete axis is spring-loaded to push the disk of the fine tuning knob against the dial.