Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 8919451 times)

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120425 on: May 23, 2022, 07:01:02 am »
Ok, have just got around to rebuilding the computer monitor power supply, to reassemble and power it up to see if it goes flash bang wallop again  :-DD Now, do I bring it up slowly on a variac or do I use the dim bulb method  :-//

Am I right in thinking that a SMPS won't power up on a variac or not  :-//

SMPSs are constant power output devices. Low input voltage => high input current, which the diodes/transistors might not like.
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120426 on: May 23, 2022, 08:02:27 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

As for Kingston, there's a guy selling all sorts of weird meat in there still to this day. You can get ostrich burgers, zebra steaks and alligator meat for example.

Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120427 on: May 23, 2022, 08:09:55 am »
Ok, have just got around to rebuilding the computer monitor power supply, to reassemble and power it up to see if it goes flash bang wallop again  :-DD Now, do I bring it up slowly on a variac or do I use the dim bulb method  :-//

Am I right in thinking that a SMPS won't power up on a variac or not  :-//

SMPSs are constant power output devices. Low input voltage => high input current, which the diodes/transistors might not like.
Although modern SMPS use UVLO to protect themselves from such operating conditions however you are correct in that you need know you patient before exposing them to operating conditions they might object to.
This is easier than most think, id the controller and download its datasheet, check a few specs and most important the Typical Application schematic which in many cases is closely replicated by manufacturers and then the rest is shit easy.
However there are exceptions with some older TE and I well remember bd139 warning against using a dim bulb tester with some Phillips scopes as you will hurt these early implementations of SMPS.
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120428 on: May 23, 2022, 08:12:15 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

If it's good, it's really good.

Better than the "adolescent bull" meat they're selling us here as the only available beef. Calves born as a by-product of breeding milk cows, driven down to Spain to have them fattened for a few months and then slaughtered. Tastes and chews like leather.
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120429 on: May 23, 2022, 08:16:15 am »
Ok, have just got around to rebuilding the computer monitor power supply, to reassemble and power it up to see if it goes flash bang wallop again  :-DD Now, do I bring it up slowly on a variac or do I use the dim bulb method  :-//

Am I right in thinking that a SMPS won't power up on a variac or not  :-//

SMPSs are constant power output devices. Low input voltage => high input current, which the diodes/transistors might not like.
Although modern SMPS use UVLO to protect themselves from such operating conditions however you are correct in that you need know you patient before exposing them to operating conditions they might object to.
This is easier than most think, id the controller and download its datasheet, check a few specs and most important the Typical Application schematic which in many cases is closely replicated by manufacturers and then the rest is shit easy.
However there are exceptions with some older TE and I well remember bd139 warning against using a dim bulb tester with some Phillips scopes as you will hurt these early implementations of SMPS.

When I fixed the blown SMPS in my old Tek 2232 scope (blown MOSFET and surrounding components), hence early SMPS, I used a Dim Bulb Tester to power it up after the repair. The scope would not power up and the light bulb would blink, literally, at a very regular pace, a bit less than one Hertz. It was like clock work... ON.......... OFF.......ON......OFF.....

I thought fuck me the SMPS is having problems again... but I decided to show some confidence in my repair, tried my luck and removed the DBT.... scope fired right up and worked just fine, it was the DBT causing the problem  ! :-DD

 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120430 on: May 23, 2022, 08:27:02 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

As for Kingston, there's a guy selling all sorts of weird meat in there still to this day. You can get ostrich burgers, zebra steaks and alligator meat for example.

Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:
Yes, that Salmonella scare is not only confined to M&S, it is reported on many websites as also being Asda, Tesco, Aldi, Sainsbury, Morrisons and Lidl and its not just sandwiches  that are affected, many other products are also being recalled, including Kindar Eggs. In fact there have been a number of similar such recalls over the last few months, which are now happening at an alarming rate since B day, welcome to the Sunny Up Lands  :palm: :scared:
Who let Murphy in?

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120431 on: May 23, 2022, 09:05:09 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

As for Kingston, there's a guy selling all sorts of weird meat in there still to this day. You can get ostrich burgers, zebra steaks and alligator meat for example.

Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:
Yes, that Salmonella scare is not only confined to M&S, it is reported on many websites as also being Asda, Tesco, Aldi, Sainsbury, Morrisons and Lidl and its not just sandwiches  that are affected, many other products are also being recalled, including Kindar Eggs. In fact there have been a number of similar such recalls over the last few months, which are now happening at an alarming rate since B day, welcome to the Sunny Up Lands  :palm: :scared:

To be fair this has always happened here periodically. I don't think Brexit made it much worse.

The issue is our food supply chain is cost optimised. Every time you buy a "meal deal" at the local supermarket, the thing that is being cost cut is the quality somewhere. That's going to be the sandwiches, which are marked up pretty high to start with. To cut costs they buy cheaper ingredients and use cheaper staff. At some point there is an optimisation point where cost is low, profit is acceptable and quality is not scandalous enough to get them in the press (until it isn't). Same with Kinder.

The best thing to do is to avoid the hell out of low ball processed and pre-packaged foods and snacks if you can. It'll do you some good anyway and cost balances out about the same if you think and plan up front.

On TE, CPC fucked up. Apparently they didn't get the PayPal transaction whereas PayPal said they did. Argh.
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120432 on: May 23, 2022, 09:07:17 am »
Ok, have just got around to rebuilding the computer monitor power supply, to reassemble and power it up to see if it goes flash bang wallop again  :-DD Now, do I bring it up slowly on a variac or do I use the dim bulb method  :-//

Am I right in thinking that a SMPS won't power up on a variac or not  :-//

SMPSs are constant power output devices. Low input voltage => high input current, which the diodes/transistors might not like.
Although modern SMPS use UVLO to protect themselves from such operating conditions however you are correct in that you need know you patient before exposing them to operating conditions they might object to.
This is easier than most think, id the controller and download its datasheet, check a few specs and most important the Typical Application schematic which in many cases is closely replicated by manufacturers and then the rest is shit easy.
However there are exceptions with some older TE and I well remember bd139 warning against using a dim bulb tester with some Phillips scopes as you will hurt these early implementations of SMPS.

When I fixed the blown SMPS in my old Tek 2232 scope (blown MOSFET and surrounding components), hence early SMPS, I used a Dim Bulb Tester to power it up after the repair. The scope would not power up and the light bulb would blink, literally, at a very regular pace, a bit less than one Hertz. It was like clock work... ON.......... OFF.......ON......OFF.....

I thought fuck me the SMPS is having problems again... but I decided to show some confidence in my repair, tried my luck and removed the DBT.... scope fired right up and worked just fine, it was the DBT causing the problem  ! :-DD

Oh the power supplies in those are absolute wankers. I actually turned down a 2235 yesterday because I couldn't face the damn thing again. Here's my thread on the last exploding bastard: https://www.eevblog.com/forum/testgear/tektronix-2235-repair-thread/

Also my hearing is actually really good for my age so I can hear the power supply switching. Annoys the hell out of me.
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120433 on: May 23, 2022, 09:37:02 am »
Ok, have just got around to rebuilding the computer monitor power supply, to reassemble and power it up to see if it goes flash bang wallop again  :-DD Now, do I bring it up slowly on a variac or do I use the dim bulb method  :-//

Am I right in thinking that a SMPS won't power up on a variac or not  :-//

SMPSs are constant power output devices. Low input voltage => high input current, which the diodes/transistors might not like.
Although modern SMPS use UVLO to protect themselves from such operating conditions however you are correct in that you need know you patient before exposing them to operating conditions they might object to.
This is easier than most think, id the controller and download its datasheet, check a few specs and most important the Typical Application schematic which in many cases is closely replicated by manufacturers and then the rest is shit easy.
However there are exceptions with some older TE and I well remember bd139 warning against using a dim bulb tester with some Phillips scopes as you will hurt these early implementations of SMPS.

When I fixed the blown SMPS in my old Tek 2232 scope (blown MOSFET and surrounding components), hence early SMPS, I used a Dim Bulb Tester to power it up after the repair. The scope would not power up and the light bulb would blink, literally, at a very regular pace, a bit less than one Hertz. It was like clock work... ON.......... OFF.......ON......OFF.....

I thought fuck me the SMPS is having problems again... but I decided to show some confidence in my repair, tried my luck and removed the DBT.... scope fired right up and worked just fine, it was the DBT causing the problem  ! :-DD
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120434 on: May 23, 2022, 09:38:26 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

As for Kingston, there's a guy selling all sorts of weird meat in there still to this day. You can get ostrich burgers, zebra steaks and alligator meat for example.

Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:
Yes, that Salmonella scare is not only confined to M&S, it is reported on many websites as also being Asda, Tesco, Aldi, Sainsbury, Morrisons and Lidl and its not just sandwiches  that are affected, many other products are also being recalled, including Kindar Eggs.

The trouble with salmonella in various Kinder products has been traced to a Ferrero factory in Belgium. Meanhile in France, the sales of deep-frozen pizza have nose-dived after a renowned brand over there had probs with norovirus.

So, post-Brexit Britain has no monopoly on this kind of problems.
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120435 on: May 23, 2022, 09:48:01 am »
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.

I do believe we did. Another one of the infernal constraints of the universe come to bugger up our engineering attempts.

The killer was if you don't drive it hard enough and quick enough, then it exceeds the SOA while temporarily in the linear region resulting in what sounds like it firing a shotgun at you. I have ear protectors and safety glasses when dealing with SMPS now  :-DD

I think on the 22xx supplies it's not actually sourcing electrons into the gate that was the problem though which came from the TL494, it was getting rid of them afterwards hence the 2n2907 sitting in front of it...



This is of course why it blew the 2n2907, the diode and the MOSFET during the failure cycle  :-DD
« Last Edit: May 23, 2022, 09:55:33 am by bd139 »
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120436 on: May 23, 2022, 10:01:50 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

As for Kingston, there's a guy selling all sorts of weird meat in there still to this day. You can get ostrich burgers, zebra steaks and alligator meat for example.

Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:
Yes, that Salmonella scare is not only confined to M&S, it is reported on many websites as also being Asda, Tesco, Aldi, Sainsbury, Morrisons and Lidl and its not just sandwiches  that are affected, many other products are also being recalled, including Kindar Eggs. In fact there have been a number of similar such recalls over the last few months, which are now happening at an alarming rate since B day, welcome to the Sunny Up Lands  :palm: :scared:

To be fair this has always happened here periodically. I don't think Brexit made it much worse.

The issue is our food supply chain is cost optimised. Every time you buy a "meal deal" at the local supermarket, the thing that is being cost cut is the quality somewhere. That's going to be the sandwiches, which are marked up pretty high to start with. To cut costs they buy cheaper ingredients and use cheaper staff. At some point there is an optimisation point where cost is low, profit is acceptable and quality is not scandalous enough to get them in the press (until it isn't). Same with Kinder.

The best thing to do is to avoid the hell out of low ball processed and pre-packaged foods and snacks if you can. It'll do you some good anyway and cost balances out about the same if you think and plan up front.

On TE, CPC fucked up. Apparently they didn't get the PayPal transaction whereas PayPal said they did. Argh.
CPC deliver tomorrow now??

I disagree on the food issue however, as this has happened now on a fairly regular basis, especially since Jan this year, I'm seeing these recalls on numerous products and its not just low ball processed, pre-packaged or snacks either, sometimes it is fresh meat, chicken for example, tinned goods etc, even nuts I've seen.  I think it is a direct result of Brexit where the usual supplier is unable to continue and the wholesalers / importers / producers are attempting to source ingredients from wherever they can. In order to fool us into believing Brexit is not having any impact on the country, the Government are allowing foodstuffs in particular into the country with zero quality checks. The same way that they are denying there is any issue with exporting, especially to the EU. Take a drive to Dover and the surrounding areas and see the huge great traffic parks of lorries, both on the roads to Dover and in of site parks. That we did used to see from time to time when bad weather, or the French were blockading their ports in some protest, but that is not the current reason.
Who let Murphy in?

Brymen-Fluke-HP-Thurlby-Heathkit-Thander-Tek-Extech-Black Star-GW-Advance-Avo-Kyoritsu-Amprobe-ITT-Robin-TTi
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120437 on: May 23, 2022, 10:08:12 am »
Yeah, I noticed that too.   ::)


I wonder what the number would be if he hadn't taken that sabbatical.
#2 behind Dave by now for sure.

Dave will soon reach the 16th, the unsigned old level.

BTW,
slim DMM with GP-IB from Germany, Systron Donner 7344A
https://www.ebay.com/itm/394077544776

BTW2,
Element14, an order of 2 desoldering tips.
A postwoman, with other mail, delivered a desoldering tip, with UPS saver tag.
A moment later, an UPS woman, delivered a desoldering tip.
Aneng-Appa-AVO-Fluke-General Radio-Heathkit-Herbert Arnold-HP-Kaise-Kyoritsu-Mastech-Simpson-Tektronix-YFE
(plus lesser brands from the work shop of the world)
 
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120438 on: May 23, 2022, 10:08:17 am »
Eating horse is a cultural no-no in the UK.

Having said that, I remember a butcher that sold horse meat for human consumption in Kingston-upon-Thames market place. Can't find any reference to it, though

It's not a particularly nice meat.

As for Kingston, there's a guy selling all sorts of weird meat in there still to this day. You can get ostrich burgers, zebra steaks and alligator meat for example.

Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:
Yes, that Salmonella scare is not only confined to M&S, it is reported on many websites as also being Asda, Tesco, Aldi, Sainsbury, Morrisons and Lidl and its not just sandwiches  that are affected, many other products are also being recalled, including Kindar Eggs.

The trouble with salmonella in various Kinder products has been traced to a Ferrero factory in Belgium. Meanhile in France, the sales of deep-frozen pizza have nose-dived after a renowned brand over there had probs with norovirus.

So, post-Brexit Britain has no monopoly on this kind of problems.
TBH, I understand that, we used to have these things before Brexit was even a word, but as far as UK is concerned, I do think it has got much worse since.
Who let Murphy in?

Brymen-Fluke-HP-Thurlby-Heathkit-Thander-Tek-Extech-Black Star-GW-Advance-Avo-Kyoritsu-Amprobe-ITT-Robin-TTi
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120439 on: May 23, 2022, 10:12:14 am »
Yeah, I noticed that too.   ::)


I wonder what the number would be if he hadn't taken that sabbatical.
#2 behind Dave by now for sure.

Dave will soon reach the 16th, the unsigned old level.

BTW,
slim DMM with GP-IB from Germany, Systron Donner 7344A
https://www.ebay.com/itm/394077544776

BTW2,
Element14, an order of 2 desoldering tips.
A postwoman, with other mail, delivered a desoldering tip, with UPS saver tag.
A moment later, an UPS woman, delivered a desoldering tip.

Now that is as thin as the old Sinclair DM325 
Who let Murphy in?

Brymen-Fluke-HP-Thurlby-Heathkit-Thander-Tek-Extech-Black Star-GW-Advance-Avo-Kyoritsu-Amprobe-ITT-Robin-TTi
 
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Offline m k

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120440 on: May 23, 2022, 10:13:30 am »
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.

I do believe we did. Another one of the infernal constraints of the universe come to bugger up our engineering attempts.

The killer was if you don't drive it hard enough and quick enough, then it exceeds the SOA while temporarily in the linear region resulting in what sounds like it firing a shotgun at you. I have ear protectors and safety glasses when dealing with SMPS now  :-DD

I think on the 22xx supplies it's not actually sourcing electrons into the gate that was the problem though which came from the TL494, it was getting rid of them afterwards hence the 2n2907 sitting in front of it...



This is of course why it blew the 2n2907, the diode and the MOSFET during the failure cycle  :-DD

Or you finally don't have an OC situation since the faulty OVP crowbar is putting the thing to OC situation.
Aneng-Appa-AVO-Fluke-General Radio-Heathkit-Herbert Arnold-HP-Kaise-Kyoritsu-Mastech-Simpson-Tektronix-YFE
(plus lesser brands from the work shop of the world)
 
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120441 on: May 23, 2022, 10:26:56 am »
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.

I do believe we did. Another one of the infernal constraints of the universe come to bugger up our engineering attempts.

The killer was if you don't drive it hard enough and quick enough, then it exceeds the SOA while temporarily in the linear region resulting in what sounds like it firing a shotgun at you. I have ear protectors and safety glasses when dealing with SMPS now  :-DD

I think on the 22xx supplies it's not actually sourcing electrons into the gate that was the problem though which came from the TL494, it was getting rid of them afterwards hence the 2n2907 sitting in front of it...



This is of course why it blew the 2n2907, the diode and the MOSFET during the failure cycle  :-DD
No not that one but a Tek repair thread Vince did where member Per Hansson gave us lessons about Miller capacitance:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401
Well worth a read.

Unfortunately also the thread where helpful member oldway crossed swords with Simon and despite it being a private slanging match oldway is with us no more.  :(
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120442 on: May 23, 2022, 10:45:23 am »
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.

I do believe we did. Another one of the infernal constraints of the universe come to bugger up our engineering attempts.

The killer was if you don't drive it hard enough and quick enough, then it exceeds the SOA while temporarily in the linear region resulting in what sounds like it firing a shotgun at you. I have ear protectors and safety glasses when dealing with SMPS now  :-DD

I think on the 22xx supplies it's not actually sourcing electrons into the gate that was the problem though which came from the TL494, it was getting rid of them afterwards hence the 2n2907 sitting in front of it...



This is of course why it blew the 2n2907, the diode and the MOSFET during the failure cycle  :-DD
No not that one but a Tek repair thread Vince did where member Per Hansson gave us lessons about Miller capacitance:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401
Well worth a read.

Unfortunately also the thread where helpful member oldway crossed swords with Simon and despite it being a private slanging match oldway is with us no more.  :(

Ah yes - miller plateau is part of the linear region transition i.e. when it's not on or off. Objective is to reduce dT there and eliminate that as quickly as possible by sourcing and sinking more electrons per second. The important thing is really gate charge there: the lower the better!  I notice another MOSFET appeared in there which is nice and all that but you tend to have to grab whatever is cheap that will work. When I did the change I optimised for gate charge (related to integral of current into and out of the gate) and SOA rather than gate capacitance. The problem with the Tek design was the SOA rather than the gate capacitance which I ran in LTspice against a few MOSFETs and there was marginal difference. The IRF820 had a higher pulse current and a little more voltage headroom but sacrificed a little bit of gate capacitance and not much gate charge.
 
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120443 on: May 23, 2022, 10:51:51 am »
Did have some time to finally frickledoodle that nomoreprivatecustomersexAgilent PSU...
At least the Datatecwechargeyoutosendyouthemissingpartssothatyoucanuseyourpurchase module apparently works.
Fluke 179 measured 35V output sharp.

 
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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120444 on: May 23, 2022, 11:23:23 am »
Edit: oh meant to mention something grim I saw on the way to Dunstable. So there's an M&S at Acton on the North Circular. Every single sandwich was removed from the shelves due to Salmonella. Big sign up saying what had been taken off the shelves :scared:

"There's food poisoning and then there's M&S food poisoning."*


* For those not exposed to UK media: Parody of M&S's current ad campaign slogan.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
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Online Vince

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120445 on: May 23, 2022, 11:30:40 am »
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.

I do believe we did. Another one of the infernal constraints of the universe come to bugger up our engineering attempts.

The killer was if you don't drive it hard enough and quick enough, then it exceeds the SOA while temporarily in the linear region resulting in what sounds like it firing a shotgun at you. I have ear protectors and safety glasses when dealing with SMPS now  :-DD

I think on the 22xx supplies it's not actually sourcing electrons into the gate that was the problem though which came from the TL494, it was getting rid of them afterwards hence the 2n2907 sitting in front of it...



This is of course why it blew the 2n2907, the diode and the MOSFET during the failure cycle  :-DD
No not that one but a Tek repair thread Vince did where member Per Hansson gave us lessons about Miller capacitance:
https://www.eevblog.com/forum/repair/tektronix-2215-scope-repair/msg1824401/#msg1824401
Well worth a read.

Unfortunately also the thread where helpful member oldway crossed swords with Simon and despite it being a private slanging match oldway is with us no more.  :(

Oh yeah I remember IOldway... what a jerk he was when he posted on that 2215 topic to complain about my long posts. I wish him a long and painful death.

I am still waiting for the replacement brass collet you said you would turn on a lathe with your friend Dubbie, to fix the broken one on the time base know ! Kiwis are all show and no go, promise just promises ! :-DD

Been 4 years now so I gave up on it  >:D 

But that's fine, because I gave on the scope altogether, it's hopeless. This erratic auto-brightness feature I could never figure out how to fix despite great efforts. That alternate sweep daughter board is not meant to be desoldered, butchered it. Tried to fix t.. butchered it even more... Can't socket it to work on it as the connectors with the proper pitch just don't exist.

I apid 40 Euros for it, no power. These days with the shit economy old analog scopes or worse nothing and right now there is a WORKING 2215A for... 40 Euros, what I paid  ofr my broken one.
There is routinely 2000 seires Tek scopes in excellent cosmetic and working condition, showing traces on the screen, for 50 Euros.

I t makes absolutely zero financial sense for me to keep trying to fix it. Much easier and valuable and useful to me as ... as parts mule. For one, it will donate a few of its knobs to fix the broken ones on my 2232. The small ones for vertical and horizontal position control, that kind. They break, shatter like glass when you  try to remove them...

 

Offline Neper

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120446 on: May 23, 2022, 12:12:44 pm »
"There's food poisoning and then there's M&S food poisoning."*


* For those not exposed to UK media: Parody of M&S's current ad campaign slogan.

From an article in Belgian newspaper La Meuse: "If you have eaten these sausages and suffered from fever, stomach cramps and diarrhea within the following 48 hours, take them back to the store for a refund."

https://lameuse.sudinfo.be/896896/article/2022-01-21/attention-si-vous-avez-mange-ces-saucisses-le-produit-ete-retire-de-la-vente?from_direct=true

Haven't seen anyone approaching an Aldi store with a bucket, though.  :-DD
« Last Edit: May 23, 2022, 12:22:05 pm by Neper »
 
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120447 on: May 23, 2022, 12:24:49 pm »
Holy crap. I sleep late today and the thread has exploded. I'm struggling to catch up.  :o

One comment then I need coffee. Unique food consumption. George Carlin once said: Americans will eat anything. If you served sauteed raccoon's asshole on a stick they would eat it. Especially dipped in butter.

Carry on.....need more caffeine then I gotta check my blood sugar and take my shot.  ;D
An old gray beard with an attitude.
 
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Offline dl6lr

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120448 on: May 23, 2022, 12:33:52 pm »
"There's food poisoning and then there's M&S food poisoning."*


* For those not exposed to UK media: Parody of M&S's current ad campaign slogan.

From an article in Belgian newspaper La Meuse: "If you have eaten these sausages and suffered from fever, stomach cramps and diarrhea within the following 48 hours, take them back to the store for a refund."

https://lameuse.sudinfo.be/896896/article/2022-01-21/attention-si-vous-avez-mange-ces-saucisses-le-produit-ete-retire-de-la-vente?from_direct=true

Haven't seen anyone approaching an Aldi store with a bucket, though.  :-DD

Similar to one experience with a local market here. We bought frozen trouts just before weekend and found out that they where probably off, so we discarded them immediately. And mentioned it to the market on Monday. Reply was we had to bring them in to get a refund   :wtf: :-// Needless to say we were not there to get a refund, but to warn for possible food poisoning. And we promised to bring in any rotten fish the next time it would occur...

 

Online mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #120449 on: May 23, 2022, 12:37:55 pm »
Yep the Tek prereg SMPS is pretty well behaved except when it isn't.
IIRC didn't you and I discuss MOSFET gate Miller capacitance some while back which is the trap when repairing the Tek prereg as often what looks like a compatible MOSFET for their repair has too much gate capacitance and the switching is troublesome as the driver hasn't sufficient grunt to overcome the gate capacitance.

I do believe we did. Another one of the infernal constraints of the universe come to bugger up our engineering attempts.

The killer was if you don't drive it hard enough and quick enough, then it exceeds the SOA while temporarily in the linear region resulting in what sounds like it firing a shotgun at you. I have ear protectors and safety glasses when dealing with SMPS now  :-DD

I think on the 22xx supplies it's not actually sourcing electrons into the gate that was the problem though which came from the TL494, it was getting rid of them afterwards hence the 2n2907 sitting in front of it...

   This is of course why it blew the 2n2907, the diode and the MOSFET during the failure cycle  :-DD
EDITED TO CLARIFY

That's the FET in the prereg bolted to the side of the chassis, with the legs plugged directly into a MOLEX connector, right?

I over that one on my 2230 after rebuilding the HV multiplier section when I first got it; replaced it with exact same part, new from either SPHERE or NIP ECG/NTE with the same part number on the transistor off eBay. About every 3rd power-up, it would go into tic-tic failure mode; noodling around in one of the Tek groups yielded advice to replace with STF9NM60N (specifically plastic package TO-220, not the regular tab) and cut the legs short & solder/shrinkwrap the wires. Scope worked perfectly for nigh on a decade after that.

That was when I decided to go back to tinkering on my old analog schizz... between that circle-jerk and the unobtanium pot the thing used for menu navigation, I decided there was just too much fucking voodoo in digital scopes of that era. :-DD

mnem
« Last Edit: May 23, 2022, 02:09:28 pm by mnementh »
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