Before it's put on a slow boat from China

Started by amdx in sci.electronics.design7 years ago 23 replies

I need a 2.7uf 63V non-polarized capacitor for a speaker crossover. It is a radial lead 10mm x 22mm cap. Ebay has them from China. (slow...

I need a 2.7uf 63V non-polarized capacitor for a speaker crossover. It is a radial lead 10mm x 22mm cap. Ebay has them from China. (slow boat) I've checked Digi-Key, Mouser, Allied, and Newark. I've also checked several speaker part sellers. I have found an axial lead cap, for $0.50 plus $6.95 shipping. But I'd prefer a radial lead. Have any other sources? Refoamed a set of Pione...


Tantalum Capacitors

Started by bitrex in sci.electronics.design7 years ago 88 replies

So I'm working on repairing a Korg MS2000B synthesizer for a friend with a dead power supply. Here's the service...

So I'm working on repairing a Korg MS2000B synthesizer for a friend with a dead power supply. Here's the service manual: http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf The first thing I notice when looking inside is that the small SMT 100uF 10V tantalum capacitor C109 has completely vacated - it appears to be gone, blown right off the board. There are some little fragment...


capacitor gets hot in a HF-HV resonant circuit

Started by blisca in sci.electronics.design7 years ago 28 replies

Hi i was asked to help some friends in a task that is unusual for me: I have to generate a 100 Vpp -150 KHz ringing on a single turn of a...

Hi i was asked to help some friends in a task that is unusual for me: I have to generate a 100 Vpp -150 KHz ringing on a single turn of a transformer secondary. I generate an adjustable PWM with a microcontroller,then a driver drives a N MOSFET connected to VDD via a couple of turns(the primary of the transformer),paralleled by a capacitor** With a pulse width of about 7us i have ...


USB CDC device works on laptop, but not on WinBook tablet

Started by P E Schoen in sci.electronics.design7 years ago 14 replies

I have a USB device that I designed several years ago, using the Microchip PIC18F2550, and it has worked mostly OK on various laptops. It has...

I have a USB device that I designed several years ago, using the Microchip PIC18F2550, and it has worked mostly OK on various laptops. It has four DC-DC converters driven by the USB 5V power and it is configured for the maximum 500 mA current draw. The actual current is 350 mA. The 5V USB supply connects to a 47 uF 16V aluminum electrolytic and a 1 uF 16V MLC capacitor. The 5V logic supp...


Q: 0-Nodes in .SUBCKT

Started by Johann Klammer in sci.electronics.design7 years ago 13 replies

The problem was simpulating with LTspice: I have this irl3103s.spi from the IR website. I am trying to use the MOSFET hi-side as a...

The problem was simpulating with LTspice: I have this irl3103s.spi from the IR website. I am trying to use the MOSFET hi-side as a sync-rectifier(backwards).... I am driving with IRL2110 (2Amps,15V). I sill get 200 Amp spikes that look like dv/dt turn on(when the lower FET(IRFZ44) switches on). I tried adding capacitor from gate to source. stopped(unsuccessfully) at around 100nF. looked at ...


This was a most unusual early radio design

Started by Anonymous in sci.electronics.design7 years ago 61 replies

This was a most unusual early radio design. Rather than change channels using a variable capacitor, they used variable inductors. Quite unique....

This was a most unusual early radio design. Rather than change channels using a variable capacitor, they used variable inductors. Quite unique. http://www.rexophone.com/?p=1319 On thing about those old radios, they always had HUGE coils. Even those that tuned using a capacitor. Apparently they would all coils by hand back then, and could not wind small ones like they used in later model ...


Why cap needed at Schmitt output?

Started by Terry Pinnell in sci.electronics.design7 years ago 27 replies

I've isolated the cause of the problem I described in my post 'Simple toggle circuit?' I'd either forgotten including one in previous...

I've isolated the cause of the problem I described in my post 'Simple toggle circuit?' I'd either forgotten including one in previous toggle circuits (about a decade ago) or I got away without doing so. But it's apparently essential to place a small capacitor at the output of a 4001 Schmitt. Without that there's hf noise, so the 4013 bistable obviously doesn't work properly. But why is it ...


Photoflash capacitor charger idea

Started by bitrex in sci.electronics.design7 years ago 4 replies

https://www.dropbox.com/s/yxnnefxugivhhe8/Photo%20Jan%2008%2C%2011 %2044%2052%20AM.jpg?dl=0 Charge big cap to dump thru strobe lamp --...

https://www.dropbox.com/s/yxnnefxugivhhe8/Photo%20Jan%2008%2C%2011 %2044%2052%20AM.jpg?dl=0 Charge big cap to dump thru strobe lamp -- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/


Audio transformer impedance

Started by bitrex in sci.electronics.design7 years ago 11 replies

I'm using one of these little PCB mount impedance matching transformers "backwards" in my junk box cap charger, and am trying to select a...

I'm using one of these little PCB mount impedance matching transformers "backwards" in my junk box cap charger, and am trying to select a value of DC blocking capacitor to put in front of it. I think I've been trying to use a value of a few nanofarads in the prototype and it's not right, there is a lot of ringing and nastyness coming out of the secondary. Here is the datasheet on th...


Transistor oscillator.

Started by Ian Field in sci.electronics.design7 years ago 56 replies

Is there a rock bottom oscillator that will free run at the frequency limit of whatever transistor is put in it? I was thinking of the common...

Is there a rock bottom oscillator that will free run at the frequency limit of whatever transistor is put in it? I was thinking of the common base job with a capacitor strapped from collector to emitter, but am unsure what to use as a collector load. Basically for testing how good are a collection of vintage germanium transistors. Thanks for any help.


Ttally confused by AC capacitor narkings -- help please

Started by Anonymous in sci.electronics.design7 years ago 12 replies

Could some electronics guru please help ? I am totally confused by markings on polystyrene AC capacitors. Unlike electrolytic capacitors which...

Could some electronics guru please help ? I am totally confused by markings on polystyrene AC capacitors. Unlike electrolytic capacitors which have their capacitance and voltage values very clearly printed, the ones on AC capacitors is very cryptic. For example, a 0.1 uF 100V AC capacitor has the marking: "28 104J" What does this mean ? Does the "J" indicate some multiplier -- as 10^-6 ?...


Inverter input current

Started by Yzordderrex in sci.electronics.design7 years ago 2 replies

I am curious if there any guidelines or rule of thumb for inverter input current. I can design an inverter with a very small DC link capacitor...

I am curious if there any guidelines or rule of thumb for inverter input current. I can design an inverter with a very small DC link capacitor and control the current going into the inverter to a high degree with a full-bridge converter. Essentially this current will mimic the output current so the capacitors see little ripple current. This will of course result in a large 120Hz


Bridge rectifier question

Started by bitrex in sci.electronics.design7 years ago 16 replies

Forgive me, my power supply topology-fu is a little rusty. Still mucking around with my junk box flash capacitor charger. So if I have a...

Forgive me, my power supply topology-fu is a little rusty. Still mucking around with my junk box flash capacitor charger. So if I have a surplus tranny with a 1:12 step up ratio that I'm feeding through a cap with a 10 volt P2P square wave with a +5 volt DC offset, that gives me +5/-5 into the tranny. 1:12 step up ratio plus bridge voltage doubler gives me about 120 volts out if I'm...


Hybrid Dielectric in Capacitors

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

If a capacitor has two layers of dielectric, one with a high dielectric strength and high dielectric constant, the other air with a much lower...

If a capacitor has two layers of dielectric, one with a high dielectric strength and high dielectric constant, the other air with a much lower dielectric strength and dielectric constant of 1. My understanding is that the single capacitor would be the equivalent of two capacitors in series as if there were a plate between the two dielectrics... in some respects. If the air gap is sma...


How yo detect capacitive power coupling

Started by Anonymous in sci.electronics.design6 years ago 8 replies

Could some electronics guru please help ? Suppose a high frequency(approx. 30 - 40 Mhz) oscillator connected across a aimple 1 cm x 1 cm plate...

Could some electronics guru please help ? Suppose a high frequency(approx. 30 - 40 Mhz) oscillator connected across a aimple 1 cm x 1 cm plate area parallel plate capacitor, with a 1 mm thick dielectric plate in between, material FR4. Now how do I detect that indeed the signals are being transmitted between the plates, given that a capacitor is a short to AC. Also, if I connect a sim...


Filtering switcher noise

Started by bitrex in sci.electronics.design6 years ago 15 replies

I'm putting together a little 4-> 1 active audio mixer circuit for a friend of mine. The circuit is basically just RC RF filter on the...

I'm putting together a little 4-> 1 active audio mixer circuit for a friend of mine. The circuit is basically just RC RF filter on the input, dc blocking capacitor, potentiometer, then into an active summer and a "zero impedance" output stage for driving cable that has a capacitive feedback loop to keep the opamp stable and then a second feedback loop around the output resistor for st


Supercapacitor backup ?

Started by mkr5000 in sci.electronics.design6 years ago 12 replies

Tell me why please using a capacitor like this (.047f) 5.5v is either perfectly fine or not a good idea on the output of a +5v power supply that...

Tell me why please using a capacitor like this (.047f) 5.5v is either perfectly fine or not a good idea on the output of a +5v power supply that powers a Raspberry PI ? The PI draws around 500ma and doesn't like power outages (just had a corrupted sd card because of one -- not fun). In my mind, I see no problem and at least it would give me a few seconds of backup which may help.


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...


Protection of 1uF capacitor against short circuit

Started by John Nagle in sci.electronics.design6 years ago 24 replies

I'm looking for a component to protect against overcurrent if the output of my Teletype current loop driver is shorted. The output end of...

I'm looking for a component to protect against overcurrent if the output of my Teletype current loop driver is shorted. The output end of this system is a 1uF aluminum electrolytic capacitor charged up to 120VDC, with the output switched by an Omron G3VM401E optoisolator. Normally, this drives an electromagnet with 55 ohm resistance and 4 H inductance. With that load, the maximum current...


How is voltage rating on capacitor determined ?

Started by Anonymous in sci.electronics.design6 years ago 25 replies

Could some electronics guru please shed some light on this ? How is the voltage rating on a capacitor calculated, at design time. For any...

Could some electronics guru please shed some light on this ? How is the voltage rating on a capacitor calculated, at design time. For any capacitor, the capacitance is the ratio of charge stored to maximum voltage across the terminals. By measuring the the discharge current and time for a fully charged capacitor to discharge, the total charge stored can be calculated. But that is pos...