In Search Of… (post the obscure parts you need help finding)

Bricksnbeatles said:
Might as well have an “In Search Of” thread for posting about the obscure and hard to find parts we need, and hopefully someone else knows of a source for em.

Obsolete ICs and transistors? Specific hardware desires? Weird cap values? Whatever you can’t find, ask about it, and we can help each other out in our searches!


I’ll start:

  1. Large bat toggle switches (just like this) in SPDT and on-on-on DPDT forms
  2. Any resistors that are BLACK in color, and are roughly the size of standard 1/2W resistors.
    • I’ve found a few mil-spec ones on digikey that might be correct, but it’s just a stock image in black and white so they might not actually be black, and the price X min-quantity is too high to jump blind on.
    • I’ve seen black Carbon Comps, but they seem to be 1/2w and bigger, which are equivalent to 1w film resistors in size, so too big.
  3. Good quality spst arcade-style momentary pushbuttons that are aluminum/steel, not plastic
Click to expand...
Sorting some components from my recent estate haul and found some black/ dark colored stuff. Not sure what’s there for values, but if you’ve got a list I’d be happy to check and drop some in the mail if I’ve got em.

477EB40A-5BA1-43D3-9D2A-8E38C7F25774.jpeg
 
jwin615 said:
I may have these in AliAlphas. Still need them? I'll give em to you if so.
Click to expand...
Thank you for your offer. I use A25k quite frequently so I'm looking for a constant supply, preferably in EU. I recently bought A22k and some of them are over 23k. I measured several Alpha A25s and some were 23k... so I think I have a temporary solution.
 
In search of a buck regulator (DC-DC step-down) that's at least 80% efficient with light loads (1 to 2mA) while switching at a constant, fixed frequency outside the audio band. I'll be in my room, waiting...
 
I was actually looking for these КТ3102E I always been fond of, ran out a few years back and sellers on eBay are asking for an amount I'm not ready to pay for.. I ended up getting in touch with Yuriy from zahidprylad and he was able to find a thousands in their warehouse, just received enough supplies for a lifetime 🙃
 

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JTEX said:
In search of a buck regulator (DC-DC step-down) that's at least 80% efficient with light loads (1 to 2mA) while switching at a constant, fixed frequency outside the audio band. I'll be in my room, waiting...
Click to expand...

Whats your Vin, Vout and any quiescent current requirements? The LT3470 might hit that efficiency depending on Vin and Vout but I can’t remember the switching frequency range
 
Last edited:
finebyfine said:
Whats your Vin, Vout and any quiescent current requirements? The LT3470 might hit that efficiency depending on Vin and Vout but I can’t remember the switching frequency range
Click to expand...
Vin 9V, Vout 3V, 1 to 2mA load.

I looked at LT3470 among many others. No good. At light loads, it operates in burst mode (like most of them). It's on for a few switching cycles, then shuts down to save power for a few dozen or hundreds of cycles, rinse, repeat. Those on/off bursts have their own frequency which falls in the audio band regardless of the actual switching frequency. The output inductor will inductively couple that audio band noise into anything nearby, including the ground plane. Low level enough not to be a problem for many unity-gain (or even attenuation) circuits (headphone amp in a phone for example), but becomes audible for low signal level with tens of dB of added gain.

I need continuous switching, no interruptions, at above 30kHz or so, so any switching noise can never drop within the audio band.

MAX17555 comes closest to what I need, but it's a nightmare to hand solder... 2x2mm package.
 
JTEX said:
In search of a buck regulator (DC-DC step-down) that's at least 80% efficient with light loads (1 to 2mA) while switching at a constant, fixed frequency outside the audio band. I'll be in my room, waiting...
Click to expand...
Vin and Vout needs?
Nm missed info in last post
 
JTEX said:
Vin 9V, Vout 3V, 1 to 2mA load.

I looked at LT3470 among many others. No good. At light loads, it operates in burst mode (like most of them). It's on for a few switching cycles, then shuts down to save power for a few dozen or hundreds of cycles, rinse, repeat. Those on/off bursts have their own frequency which falls in the audio band regardless of the actual switching frequency. The output inductor will inductively couple that audio band noise into anything nearby, including the ground plane. Low level enough not to be a problem for many unity-gain (or even attenuation) circuits (headphone amp in a phone for example), but becomes audible for low signal level with tens of dB of added gain.

I need continuous switching, no interruptions, at above 30kHz or so, so any switching noise can never drop within the audio band.

MAX17555 comes closest to what I need, but it's a nightmare to hand solder... 2x2mm package.
Click to expand...

Have you looked at products from Diodes inc?
 
finebyfine said:
Have you looked at products from Diodes inc?
Click to expand...
Yup.
TI has a new thing called OOA, which guarantees out-of-audio band switching at any load, but the few parts with OOA are all targeted at much higher output currents than what I need. So, not particularly efficient at 1mA.
 
JTEX said:
Vin 9V, Vout 3V, 1 to 2mA load.

I looked at LT3470 among many others. No good. At light loads, it operates in burst mode (like most of them). It's on for a few switching cycles, then shuts down to save power for a few dozen or hundreds of cycles, rinse, repeat. Those on/off bursts have their own frequency which falls in the audio band regardless of the actual switching frequency. The output inductor will inductively couple that audio band noise into anything nearby, including the ground plane. Low level enough not to be a problem for many unity-gain (or even attenuation) circuits (headphone amp in a phone for example), but becomes audible for low signal level with tens of dB of added gain.

I need continuous switching, no interruptions, at above 30kHz or so, so any switching noise can never drop within the audio band.

MAX17555 comes closest to what I need, but it's a nightmare to hand solder... 2x2mm package.
Click to expand...
LTC3256
LTC3255

Can you run the rest of the circuit at bipolar +/-5v?
Maybe could use a LTC3260 to go 9v to +/-4.5?

2mA load is tough. So many will want to shutdown there
 
jwin615 said:
LTC3256
LTC3255

Can you run the rest of the circuit at bipolar +/-5v?
Maybe could use a LTC3260 to go 9v to +/-4.5?

2mA load is tough. So many will want to shutdown there
Click to expand...
I looked at switched capacitor stuff too. Not efficient enough (50% to 70%, depending on vin vs vout, which varies as the battery runs down. So sometimes 50%...). I'm already getting close to 60% with a MAX17550.

4.5V won't do, I need to run some parts at 3V to get their lowest quiescent.

I ordered a MAX17555 eval kit, but for now MAX17550 will have to do.
 
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