Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 14552909 times)

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Offline Wolfgang

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20050 on: November 20, 2018, 07:05:22 pm »
In this case it was a bit of shitty engineering. 2A IRF710 with 400V ceiling on mains. Idiots. Looks like it had actually nuked the heatsink compound on it and had exited the SOA which was tight anyway. Kaboom!

Testing all surrounding bits now... took a diode with it by the looks. Main IC appears to have some activity and it didn’t take the primary of the transformer out thank fuck.

Finding a 6A part with 500-600V headroom next...

I prefer linear supplies with standard transistors to switchers. Less explodey :)

... if its running in linear mode, you need a wide FBSOA type. In switchmode, old ones are often more robust than new ones. NOS rulez !!  >:D
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20051 on: November 20, 2018, 07:06:37 pm »
2235. I have replaced all the RIFAs!

Sounded like a short arc. May have just been a shitty old fuse as well.

Found it. Stuffed a new fuse in and looked for the explosion. Main switching MOSFET  :--
There's some good reading on those pre-regs and SMPS here:
https://www.eevblog.com/forum/repair/tektronix-2232-scope-in-need-of-a-doctor/
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/
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Offline URI

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20052 on: November 20, 2018, 07:55:21 pm »
Oops! I did it again...

I was watching an auction (mistake #1) for one of those new-fangled rubber-buttoned HP 3456A that URI corrupted me with (thanks, URI).
Pleasure on my side having been helpful.   >:D


It's supposedly a for-parts unit, and the price was still increasing with 18 watchers standing by for a snipe-o-rama tomorrow. :o Then, I saw a new listing for one that has rack ears and handles instead of feet, but is guaranteed to be working for a few bucks more, BIN. So, I bought it now. :-DMM

Yepp, also saw that one. So you bought it. Congrats.  :)
Hopefully it's in the state described be the seller, it looked good on the photos.


Of course, it goes without saying that I don't really need more voltmeters. However, I have to keep my TEA membership valid somehow. :-DD

One can never have too many voltmeters to cross check..   :-DD
A life without TEA is possible but pointless.
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20053 on: November 20, 2018, 08:25:48 pm »
There's some good reading on those pre-regs and SMPS here:
https://www.eevblog.com/forum/repair/tektronix-2232-scope-in-need-of-a-doctor/
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/

Thanks for this - much appreciated. I went through those I think (a few different pages).

Quick diary of events for the sake of recording annoyance.

First thing, ripped out all the old stuff that was suspect. Here's what got replaced. Quite a bit:



Turned it on, worked straight up. Did a little dance. Was checking calibration then kaboom and fuse went. Followed by much swearing. Took it to bits and couldn't find anything wrong, then saw a singed bit on the edge of the main MOSFET. Took that to bits and found this hiding:



Turns out it's a 2A IRF710 MOSFET at 25oC. AT 100oC it's a 1.5A 400V MOSFET. Mains here peaks at up to 370V peak which is VERY close to the edge of the SOA of that part. Also I may have knocked it when replacing a cap underneath it. Ah well it's dead.

Found and read the following: http://www.hakanh.com/dl/docs/troubleshooting_tips_on_2200_ps.pdf ... followed by an hour of pull and test.

I have lost Q9070, Q908 and CR907. Shopping time.

Bodies:



Q9070 was an IRF710. Will replace with something a bit meatier, perhaps IRF820 as Tek used that as a sub and has 500V Vds without too much gate capacitance. 2.5A.

CR907 was a BYD73G which is made of unobtainium. Substitutes are MR856 / MUR460.

Q908 is an MPS2907A which is sub of 2n2907a. I already have a bag of them. Phew.
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20054 on: November 20, 2018, 08:38:25 pm »
There's some good reading on those pre-regs and SMPS here:
https://www.eevblog.com/forum/repair/tektronix-2232-scope-in-need-of-a-doctor/
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/

Thanks for this - much appreciated. I went through those I think (a few different pages).

Quick diary of events for the sake of recording annoyance.

First thing, ripped out all the old stuff that was suspect. Here's what got replaced. Quite a bit:



Turned it on, worked straight up. Did a little dance. Was checking calibration then kaboom and fuse went. Followed by much swearing. Took it to bits and couldn't find anything wrong, then saw a singed bit on the edge of the main MOSFET. Took that to bits and found this hiding:



Turns out it's a 2A IRF710 MOSFET at 25oC. AT 100oC it's a 1.5A 400V MOSFET. Mains here peaks at up to 370V peak which is VERY close to the edge of the SOA of that part. Also I may have knocked it when replacing a cap underneath it. Ah well it's dead.

Found and read the following: http://www.hakanh.com/dl/docs/troubleshooting_tips_on_2200_ps.pdf ... followed by an hour of pull and test.

I have lost Q9070, Q908 and CR907. Shopping time.

Bodies:



Q9070 was an IRF710. Will replace with something a bit meatier, perhaps IRF820 as Tek used that as a sub and has 500V Vds without too much gate capacitance. 2.5A.

CR907 was a BYD73G which is made of unobtainium. Substitutes are MR856 / MUR460.

Q908 is an MPS2907A which is sub of 2n2907a. I already have a bag of them. Phew.
They appear to be a right bitch to get right sometimes and IMO component substitution is critical to success otherwise they can be whiny beasts which again IMO is indicative the pre-reg or SMPS is running on the edge of its comfort zone. You probably read my opinions on that.
Member Per Hansson had some valuable input about these.
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20055 on: November 20, 2018, 08:43:42 pm »
Yeah this one just about dropped down into audible range just before it exploded. Was interesting to hear. Until it exploded  :-DD

Only problem I'm finding with this is finding somewhere suitably cheap to get the bits from that doesn't have any stupid min order quantities or rip off prices.
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20056 on: November 20, 2018, 08:52:52 pm »
Yeah this one just about dropped down into audible range just before it exploded. Was interesting to hear. Until it exploded  :-DD

Only problem I'm finding with this is finding somewhere suitably cheap to get the bits from that doesn't have any stupid min order quantities or rip off prices.
Pre-reg right ?

It might be worth powering the SMPS remotely to ensure there's not too much current being drawn that could put the pre-reg in an unhappy mode.
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20057 on: November 20, 2018, 09:00:28 pm »
Yes pre-reg. There's a PTC in there which will have to do the job. I only have kit to do this on line unfortunately  :--
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20058 on: November 20, 2018, 09:04:01 pm »
Yes pre-reg. There's a PTC in there which will have to do the job. I only have kit to do this on line unfortunately  :--
IIRC you need an amp or two @ ~42V, surely you have something to cobble together that can do ?
A couple of linear PSU's in series ?
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Offline bitseekerTopic starter

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20059 on: November 20, 2018, 09:16:54 pm »
It's supposedly a for-parts unit, and the price was still increasing with 18 watchers standing by for a snipe-o-rama tomorrow. :o Then, I saw a new listing for one that has rack ears and handles instead of feet, but is guaranteed to be working for a few bucks more, BIN. So, I bought it now. :-DMM

Yepp, also saw that one. So you bought it. Congrats.  :)
Hopefully it's in the state described be the seller, it looked good on the photos.

Will let you know when I get it. It has to be good. My repair queue is tooooooooo long. ;D
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20060 on: November 20, 2018, 09:35:54 pm »
Yes pre-reg. There's a PTC in there which will have to do the job. I only have kit to do this on line unfortunately  :--
IIRC you need an amp or two @ ~42V, surely you have something to cobble together that can do ?
A couple of linear PSU's in series ?

I’ve got a 30V 1A and 15V 4A so no  :--
 

Offline tautech

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20061 on: November 20, 2018, 09:42:58 pm »
Yes pre-reg. There's a PTC in there which will have to do the job. I only have kit to do this on line unfortunately  :--
IIRC you need an amp or two @ ~42V, surely you have something to cobble together that can do ?
A couple of linear PSU's in series ?

I’ve got a 30V 1A and 15V 4A so no  :--
You need more gear !  :P

Might I suggest SDP3303X-E that when series'd can offer 60V @3A !
And the X-E has been cracked......simple FW mod to make it an X with 1mV/mA resolution !

OK, I'll get my coat and hat, catchya.  :)
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Offline Neomys Sapiens

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20062 on: November 20, 2018, 09:58:12 pm »
Just looked it up and found out that the only TO-220 Mosfet over 200V that I have in stock is the STP20NM50FP, which is far above in current, but also in gate charge. Not much slower, though. Also nil on the diode. sorry.
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20063 on: November 20, 2018, 10:13:04 pm »
Yes pre-reg. There's a PTC in there which will have to do the job. I only have kit to do this on line unfortunately  :--
IIRC you need an amp or two @ ~42V, surely you have something to cobble together that can do ?
A couple of linear PSU's in series ?

I’ve got a 30V 1A and 15V 4A so no  :--
You need more gear !  :P

Might I suggest SDP3303X-E that when series'd can offer 60V @3A !
And the X-E has been cracked......simple FW mod to make it an X with 1mV/mA resolution !

OK, I'll get my coat and hat, catchya.  :)


Honestly I'd buy an SDP3303X-E in a snap if I was running a more professional outfit, but I'm not.

To cover the gap, I do have a TTi PL330 on the watch list. That'd give me 30V @ 3A + 15V @ 4A, totalling 45V @ 3A peak for less money and no bloody fan ;)

That might go on the backburner though as the dryer blew up a couple of hours back. Smells like SMPS again  :-BROKE

Just looked it up and found out that the only TO-220 Mosfet over 200V that I have in stock is the STP20NM50FP, which is far above in current, but also in gate charge. Not much slower, though. Also nil on the diode. sorry.

Have ordered bits for CPC now.

IRF820PBF
MUR460RLG

2 each £2.33 total

Have added some zener diodes I was missing and some batteries and knocked it over the £8 free delivery limit ;)
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20064 on: November 20, 2018, 10:18:12 pm »
There's some good reading on those pre-regs and SMPS here:
https://www.eevblog.com/forum/repair/tektronix-2232-scope-in-need-of-a-doctor/
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/

Thanks for this - much appreciated. I went through those I think (a few different pages).

Quick diary of events for the sake of recording annoyance.

First thing, ripped out all the old stuff that was suspect. Here's what got replaced. Quite a bit:

      

Turned it on, worked straight up. Did a little dance. Was checking calibration then kaboom and fuse went. Followed by much swearing. Took it to bits and couldn't find anything wrong, then saw a singed bit on the edge of the main MOSFET. Took that to bits and found this hiding:

Turns out it's a 2A IRF710 MOSFET at 25oC. AT 100oC it's a 1.5A 400V MOSFET. Mains here peaks at up to 370V peak which is VERY close to the edge of the SOA of that part. Also I may have knocked it when replacing a cap underneath it. Ah well it's dead.

Found and read the following: http://www.hakanh.com/dl/docs/troubleshooting_tips_on_2200_ps.pdf ... followed by an hour of pull and test.

I have lost Q9070, Q908 and CR907. Shopping time.  Bodies:

Q9070 was an IRF710. Will replace with something a bit meatier, perhaps IRF820 as Tek used that as a sub and has 500V Vds without too much gate capacitance. 2.5A.

CR907 was a BYD73G which is made of unobtainium. Substitutes are MR856 / MUR460.

Q908 is an MPS2907A which is sub of 2n2907a. I already have a bag of them. Phew.

Yeah... like I was saying earlier; I went through all of this more than 10 years ago on anatek and alt.sci.repair when I first resurrected my 2230. The consensus then was that C907 and CR907 get leaky with age and cause this very failure. When C908 (220Pf/250v) on pin 10 of T906 arced intermittently on mine, it would drop into the audible range as you're describing.

Q9070 survived on mine; I'm still using the original. If it had been running on 240VAC like yours, might very well have kakked.

Too bad you're on the other side of the pond... I'd send you my 2230 as a guinea pig; I still have the schematics blown up to 18" x 24" from back then. I'd still be willing to split shipping if it's worth it tooya.

Cheers,

mnem
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20065 on: November 20, 2018, 10:20:19 pm »
Talking of which, it's getting a bit cold here finally. I was in Machine Mart yesterday to buy a TX7 Torx (I only have TX6 and two TX8 in my set :palm: ) and there was a crazy person buying a 25KW space heater to heat up their living room because their heating had broken down. Think they'll set fire to the walls with it!
What? Was it one of those paraffin heaters with a stocking great fan in a case sort of torpedo shaped? Those things are fecking lethal, the outlet glows red hot on them and will burn anything put in front of it after a few minutes.  :-DD

Looked it up. Gas fired!

https://www.machinemart.co.uk/p/clarke-devil-900-propane-fired-space-heater/

 :palm:

 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20066 on: November 20, 2018, 10:28:08 pm »
Yeah... like I was saying earlier; I went through all of this more than 10 years ago on anatek and alt.sci.repair when I first resurrected my 2230. The consensus then was that C907 and CR907 get leaky with age and cause this very failure. When C908 (220Pf/250v) on pin 10 of T906 arced intermittently on mine, it would drop into the audible range as you're describing.

Q9070 survived on mine; I'm still using the original. If it had been running on 240VAC like yours, might very well have kakked.

Too bad you're on the other side of the pond... I'd send you my 2230 as a guinea pig; I still have the schematics blown up to 18" x 24" from back then. I'd still be willing to split shipping if it's worth it tooya.

Cheers,

mnem
*wibble*

I actually pulled C907 out and measured it and checked leakage. Bang on 1uF. Used a cheap Chinese tube transformer, 1n4007, left over caps and voltage doubler (on solderless breadboard) to get 300v across it and measured leakage and it was 30uA which is bugger all fortunately.  CR907 went totally short though.

I'll give it it's due; it fails safe. That's more than a lot of designs.

Thanks for the offer - will see how far I get with these bits first. I reckon I can solve it. The only parts which are end game are T906 and T948 and they seem to check out ok.

Bits arriving in 3-5 days.

Next in the repair queue: bulging battery in eldest's iPhone... probably explode in my face based on how this week is going  :-DD

On a positive note I just snagged a whole stack of lucrative amateur radio books!
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20067 on: November 20, 2018, 10:40:20 pm »
Yeah... like I was saying earlier; I went through all of this more than 10 years ago on anatek and alt.sci.repair when I first resurrected my 2230. The consensus then was that C907 and CR907 get leaky with age and cause this very failure. When C908 (220Pf/250v) on pin 10 of T906 arced intermittently on mine, it would drop into the audible range as you're describing.

Q9070 survived on mine; I'm still using the original. If it had been running on 240VAC like yours, might very well have kakked.

Too bad you're on the other side of the pond... I'd send you my 2230 as a guinea pig; I still have the schematics blown up to 18" x 24" from back then. I'd still be willing to split shipping if it's worth it tooya.

Cheers,

mnem
*wibble*

I actually pulled C907 out and measured it and checked leakage. Bang on 1uF. Used a cheap Chinese tube transformer, 1n4007, left over caps and voltage doubler (on solderless breadboard) to get 300v across it and measured leakage and it was 30uA which is bugger all fortunately.  CR907 went totally short though.

I'll give it it's due; it fails safe. That's more than a lot of designs.

Thanks for the offer - will see how far I get with these bits first. I reckon I can solve it. The only parts which are end game are T906 and T948 and they seem to check out ok.

Bits arriving in 3-5 days.

Next in the repair queue: bulging battery in eldest's iPhone... probably explode in my face based on how this week is going  :-DD

On a positive note I just snagged a whole stack of lucrative amateur radio books!
Hmmm... wonder if maybe intermittent dielectric breakdown on C907. I can tell you that I was warned several times from different sources that cap was not to be trusted under any circumstances.  ;)

Good hunting,

mnem
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20068 on: November 20, 2018, 10:51:40 pm »
Possibility. Worth changing it anyway. And C908. I will order some. Have to do those on Farnell and get buggered for the low value order charge :--
 

Offline Brumby

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20069 on: November 21, 2018, 01:36:21 am »
Talking of which, it's getting a bit cold here finally. I was in Machine Mart yesterday to buy a TX7 Torx (I only have TX6 and two TX8 in my set :palm: ) and there was a crazy person buying a 25KW space heater to heat up their living room because their heating had broken down. Think they'll set fire to the walls with it!
What? Was it one of those paraffin heaters with a stocking great fan in a case sort of torpedo shaped? Those things are fecking lethal, the outlet glows red hot on them and will burn anything put in front of it after a few minutes.  :-DD

Looked it up. Gas fired!

https://www.machinemart.co.uk/p/clarke-devil-900-propane-fired-space-heater/

 :palm:

The first place I ever worked full time at used to sell this sort of thing - the Master Heater range, IIRC.  They had models that could heat a Costco.
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20070 on: November 21, 2018, 01:56:43 am »
Talking of which, it's getting a bit cold here finally. I was in Machine Mart yesterday to buy a TX7 Torx (I only have TX6 and two TX8 in my set :palm: ) and there was a crazy person buying a 25KW space heater to heat up their living room because their heating had broken down. Think they'll set fire to the walls with it!
What? Was it one of those paraffin heaters with a stocking great fan in a case sort of torpedo shaped? Those things are fecking lethal, the outlet glows red hot on them and will burn anything put in front of it after a few minutes.  :-DD

Looked it up. Gas fired!

https://www.machinemart.co.uk/p/clarke-devil-900-propane-fired-space-heater/

 :palm:


Arh so,, The ones I remembered are ones that we had in our bus garage when I was doing my apprenticeship, similar to the one in the attached pic and they did throw out a hell of a lot of heat but also bloody scary  :scared: I can tell you, loads of engineers got their overalls singed or even burned by standing too long in the front of them, even at a range of 3 to 4 feet such was the ferocity of heat they produced and they sounded just like a doodlebug flying around (V1 rocket)  >:D

In other news, I got myself a mini video camera today, this is the first dedicated one I have had, only a cheap one for now, 720P but reasonably capable. If I can get on with it and make some reasonable videos, I'm thinking of upgrading later to something a bit more special, at least 1080p with add on mics, lights etc,
« Last Edit: November 21, 2018, 02:08:38 am by Specmaster »
Who let Murphy in?

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Offline Neomys Sapiens

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20071 on: November 21, 2018, 02:17:59 am »
Talking of which, it's getting a bit cold here finally. I was in Machine Mart yesterday to buy a TX7 Torx (I only have TX6 and two TX8 in my set :palm: ) and there was a crazy person buying a 25KW space heater to heat up their living room because their heating had broken down. Think they'll set fire to the walls with it!
What? Was it one of those paraffin heaters with a stocking great fan in a case sort of torpedo shaped? Those things are fecking lethal, the outlet glows red hot on them and will burn anything put in front of it after a few minutes.  :-DD

Looked it up. Gas fired!

https://www.machinemart.co.uk/p/clarke-devil-900-propane-fired-space-heater/

 :palm:


Arh so,, The ones I remembered are ones that we had in our bus garage when I was doing my apprenticeship, similar to the one in the attached pic and they did throw out a hell of a lot of heat but also bloody scary  :scared: I can tell you, loads of engineers got their overalls singed or even burned by standing too long in the front of them, even at a range of 3 to 4 feet such was the ferocity of heat they produced and they sounded just like a doodlebug flying around (V1 rocket)  >:D
Actually, there are heaters working to a principle closely related to the Schmidt-Rohr (Pulsejet) of the V1. They are fanless, but also quite scary. In German, they are called Schwingfeuerheizung (oscillating flame heater). You had to prime them by pumping hard on a lever, then press the ignition button. If you goofed up during the start procedure once or twice, they could have a small explosion on retry.

You can see the priming handle to the left, the ignition button is on top of it. The monster needs 12V or 24V only for starting. Hot air exits at the flange to the rear, not the end.
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20072 on: November 21, 2018, 02:22:51 am »
That looks quite lethal, did the end glow red hot, the ones I show do.
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Offline 0culus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20073 on: November 21, 2018, 02:42:34 am »
I've seen drywall and paint guys use similar propane heaters for drying things out after the inside of a new house is freshly mudded/primed/painted.
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #20074 on: November 21, 2018, 03:40:59 am »

Over here those are call a "Torpedo heater or a "Salamander" heater, after the the first commercial variant sold since the '40s or so. Those models were a deathtrap; they'd rattle apart, and the guts would set fire to anything they came in contact with. These are intended to warm large spaces, or even to warm open construction sites.

They are literally just a jet engine bolted to a fuel tank; they have a compressor section, a venturi section, and a fuel rail/ignition section, and they even run on the same fuel oil jet engines do.  :-DD

What makes them a heater instead of a propulsion mechanism is the fact the venturi dead heads against the radiant cone; this causes a rolling effect in the airflow similar to how you blow a smoke ring. The air passes over the cone several times before it reaches escape velocity and is blown out around the perimeter.

None of these are what you can call safe; they are meant only as temporary heat in a well-ventilated area and never for unsupervised operation. The last couple decades have improved a lot, though... they're mandated to have a mechanical tip-over safety that shuts off fuel flow instantly if the unit even comes close to COG, and they now use a smart ignition system with a flame detector just as modern oil-fired furnace does, so it doesn't just keep pumping fuel if it doesn't ignite or if ignition fails.

Typically these things are good for 80-250K BTU as you'd buy from the local Homeowner Hell; but I've worked on sites with 850K BTU units bigger than a refrigerator.

As you might imagine, they tend to burn pretty sooty... any breathing problems whatsoever and they'll set you off.

mnem
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