Spot the Design Error 2

Started by Phil Allison in sci.electronics.design3 years ago 34 replies

Hi to my many admirers, see schem for tube instrument amplifier, the famous Fender "Bassman 50"....

Hi to my many admirers, see schem for tube instrument amplifier, the famous Fender "Bassman 50". https://schematicheaven.net/fenderamps/fender_bassman50.pdf Thousands made and sold, yet it has a fatal design flaw. Owners can, in a single step that they would never imagine was hazardous, instantly damage or destroy output tubes and/or the output transformer. This during ...


Is there a "name" for each Leg in AC voltage"

Started by Anonymous in sci.electronics.design7 years ago 7 replies

The typical U.S. home has 240v coming from the power pole, with a neutral, which is the center tap of the pole transformer. Thus there are two...

The typical U.S. home has 240v coming from the power pole, with a neutral, which is the center tap of the pole transformer. Thus there are two 120V supply lines. Each of these supply lines are called "Legs". This all makes sense, and with my electrical background I fully understand how it all works. However, I have always wondered if there are names for each of these legs. For example...


Transformer questions

Started by Anonymous in sci.electronics.design5 years ago 17 replies

If we take a big pile of random laminated EI core mains transformers with no known manufacturer specs other than output VA & voltage... When...

If we take a big pile of random laminated EI core mains transformers with no known manufacturer specs other than output VA & voltage... When powering them on 220-240v, how much VA can safely be drawn from the halfway primary tapping? What are the effects of exceeding manufacturer power output ratings? What temperature cutout stuck to the outside of the EI core would protect these transfor...


transformer design for smps

Started by panfilero in sci.electronics.design11 years ago 20 replies

I have a couple questions, one is about identifying smps topology and the 2nd is about the 3rd winding in an example I found. I need to design a...

I have a couple questions, one is about identifying smps topology and the 2nd is about the 3rd winding in an example I found. I need to design a smps that can take Vin: 70V to 105V and output 5V at 1A I've chosen to use the mic9130 http://www.micrel.com/_PDF/mic9130.pdf On the front page of the datasheet there is a "Typical Application" schematic, which is not to far off from what I ne...


custom transformers from China

Started by Winfield Hill in sci.electronics.design3 years ago 20 replies

There are custom transformer companies in China, with their pages on AliExpress, seeking orders for making custom transformers. Pick from...

There are custom transformer companies in China, with their pages on AliExpress, seeking orders for making custom transformers. Pick from their standard frame types and sizes, fill out a form, maybe get a quote first, or not, place an order. Some seem very experienced, highly-skilled and competent, such as Ranlo. Has anyone had experience doing such a thing? In the old day...


dumb design, happy ending

Started by John Larkin in sci.electronics.design8 years ago 7 replies

I designed a 48-channel optoisolated digital input module, something having to do with a submarine. The customer wanted built-in-self-test,...

I designed a 48-channel optoisolated digital input module, something having to do with a submarine. The customer wanted built-in-self-test, so I did this: https://dl.dropboxusercontent.com/u/53724080/Optos/V280_channel.JPG The idea is to transformer-couple in a positive pulse and force the opto on, then a negative pulse to force it off, and check those in the FPGA. The original pulse ...


"regular" dimmer switches and transformers

Started by Tim Wescott in sci.electronics.design9 years ago 45 replies

I've heard over and over again that dimmer switches don't like inductive loads, but in the background of that is the occasional refrain "oh,...

I've heard over and over again that dimmer switches don't like inductive loads, but in the background of that is the occasional refrain "oh, it's not so bad". I've never analyzed the usual dimmer switch circuit but -- what would happen if you connected a dimmer switch to a transformer that had a resistive load on it? Would you just not have full range, would the switch or the transfo...


Cascode emitter follower

Started by Tim Williams in sci.electronics.design6 years ago 45 replies

What think ye? Purpose: increase the output voltage range of an emitter follower. Like, the complementary follower in the output of an audio...

What think ye? Purpose: increase the output voltage range of an emitter follower. Like, the complementary follower in the output of an audio amp. But maybe not for audio, but for 50 ohm loads, hence the need for high voltages. Since, obviously(?), no 500V+ RF transistors exist*. And of course, doing it straightaway means possibly DC coupling, no need for a matching transformer. ...


Z source inverter question

Started by Anonymous in sci.electronics.design6 years ago 1 reply

Could some electronics guru please shed some light on this ? For a Z source inverter, with capacitor and inductor values of C and L, powered...

Could some electronics guru please shed some light on this ? For a Z source inverter, with capacitor and inductor values of C and L, powered by a DC source Vdc, what would be the output current, when driving one side of a transformer. Basically, I am looking for some pointers to any source (online preferably) that can provide sone analytical expressions for the instantaneous current. Tha...


Why does it work so well?

Started by Piotr Wyderski in sci.electronics.design6 years ago 8 replies

I have the following simple converter: CD4093 drives the power logic shift register's NPIC6C596A OE pin with 500kHz square wave signal...

I have the following simple converter: CD4093 drives the power logic shift register's NPIC6C596A OE pin with 500kHz square wave signal with duty cycle 40%. Both chips are powered from 5V, the shift register is set to all ones. Hence I have 8 modulated open drain channels, everything works as expected. Now I connect a 1:1 transformer wound on a PC40 6mm toroid (AL=2300), 16 turns each. The p...


LT spice, leakage inductance

Started by John Larkin in sci.electronics.design5 years ago 227 replies

I'm simulating a flyback switcher and noticed that any K < 1 in the transformer radically slows down the sim, which is annoyingly...

I'm simulating a flyback switcher and noticed that any K < 1 in the transformer radically slows down the sim, which is annoyingly slow already... 90 seconds to sim 60 ms of startup and a little pulsed load blip. Maybe 6:1 slower with a little leakage inductance. So I only include leakage inductance to tweak the snubber. -- John Larkin Highland Technology, Inc picosecond


Old-timey design from not too long ago

Started by bitrex in sci.electronics.design6 years ago 17 replies

The Yamaha TX81Z, circa 1986: http://i254.photobucket.com/albums/hh102/gjm_photo/TX81Z1.jpg Big transformer, linear regulators, two-sided...

The Yamaha TX81Z, circa 1986: http://i254.photobucket.com/albums/hh102/gjm_photo/TX81Z1.jpg Big transformer, linear regulators, two-sided board, bunch of DIPs. Looks like the power switch is on the left at the back, and they've routed some long piece of metal around the regulator heatsinks all the way to the front panel. Anyone know why they'd do that? The ICs seem scattered all ov...


Fixing the alien translators mistake

Started by Jan Panteltje in sci.electronics.design11 years ago 70 replies

Now the alien translator wrote the PMTs I am using needed 500 V. But deciphering the documents that came with the PMTs revealed those need 1750...

Now the alien translator wrote the PMTs I am using needed 500 V. But deciphering the documents that came with the PMTs revealed those need 1750 V. The avid reader of this newsgroup will have noticed I made a nice 500 V design, stabilised, and all that, tested too, used little power, see thread little 'audio transformer'... So could I 'push up' that design to say 2 kV? (seems a safe value ...


Microwave transformer inrush current solution?

Started by Richard Rasker in sci.electronics.design9 years ago 26 replies

Hello, I've been asked to look into a problem with an industrial installation with 3 kVA HV magnetron (microwave oven) transformers, where...

Hello, I've been asked to look into a problem with an industrial installation with 3 kVA HV magnetron (microwave oven) transformers, where mains fuses keep tripping due to the inrush current. Normally, I'd look into NTC's or power resistors with bypass relays; however, those solutions are useless in this case, because the magnetron units are switched off and on very frequently (up to...


8086 powered IBM PC compatible

Started by XT.8086 in sci.electronics.design11 years ago 95 replies

Could someone design for me a 8086 powered computer which is IBM compatible requirement: 1. using toroidal transformer as power supply...

Could someone design for me a 8086 powered computer which is IBM compatible requirement: 1. using toroidal transformer as power supply instead of SMPS 2. using SRAM instead of DRAM 3. using super I/O chip this is to replace aging 8088 system, and also used to teach pure 16 bit design. thank you


I'm looking for plans for an Electric Chair

Started by Unlisted in sci.electronics.design4 years ago 36 replies

Over the decades. many people had met their death by Electric Chair. The law enforcement people seem to be the only ones who have...

Over the decades. many people had met their death by Electric Chair. The law enforcement people seem to be the only ones who have Electric Chairs. But I'm sure these can be built at home. My guess is to use a transformer that applies 1000 or more AC Volts at a high current. Then take a wooden chair, and put metal pads on different parts of the chair. Some get connected to one side of the t...


PCB transmission line transformer

Started by John Larkin in sci.electronics.design8 years ago 54 replies

We've used transmission-line transformers to drive mosfet gates. We've wound them from micro-coax on ferrite toroids, with the shield being...

We've used transmission-line transformers to drive mosfet gates. We've wound them from micro-coax on ferrite toroids, with the shield being the primary and the inner conductor the secondary. Sub-ns speed and low leakage inductance. But it's labor intensive. So I was thinking about doing it on a multilayer PCB, like a 6-layer. Layers 1/3/5 could be one to three layers of spiral trace, pr...


transformer, 4 Times rule for multiple of reactance to resistance being transformed

Started by amdx in sci.electronics.design1 week ago 2 replies

I have this graph showing the 'Z_Normalized sub i' vs the multiple of reactance to resistance needing transforming. I don't know what the...

I have this graph showing the 'Z_Normalized sub i' vs the multiple of reactance to resistance needing transforming. I don't know what the 'Z_Normalized sub i' means. Or, how I could use it to calculate input resistance, current, voltage or what I can do with it. Can someone explain it to me? > https://www.dropbox.com/s/fwfzwrjxg9e7ayo/4%20Times%20Rule%20Graph.png?dl=0          


ohm meter battery

Started by Anonymous in sci.electronics.design9 years ago 13 replies

I found this circuit somewhere, (I can't remember) to replace the 1.50 volt= battery in a VTVM. I have an RCA WV98C Senior Voltohmyst VTVM that...

I found this circuit somewhere, (I can't remember) to replace the 1.50 volt= battery in a VTVM. I have an RCA WV98C Senior Voltohmyst VTVM that is in p= erfect condition but doesn't get used very often. This battery retrofit cir= cuit takes power from the 6.30 volt filament transformer and is built aroun= d an LM317. With a trim pot you set it for 1.55 volts and you never have to= change a ...


Some oscilloscope pictures

Started by Sylvia Else in sci.electronics.design1 year ago 25 replies

Shows how the power transformer is directly wired to two separate boards. Not sure how, or why, they'd want to do that. Shows the...

Shows how the power transformer is directly wired to two separate boards. Not sure how, or why, they'd want to do that. Shows the hole through which the transistor has to be soldered. Note the two resistors in plastic tubing that have one end so