Simple, no-math transformer snubber using Quasimodo test-jig

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#2,701
jminassi said:
Ok, after twirling the controls on my Hantek DSO2D15 I get what I think are reasonable wave forms. I have a pair of Antek-0218 transformers that I intend to use in a balanced Zen Mod Preamp yet to be built. These are 25 VA transformers with dual 18 V secondaries. I am getting a Rs reading of about 24 ohms on one of the transformers and 88 ohms on the second transformer. This seems to me to be too big of a difference.

I am using one probe and triggering on the falling edge. Does it make sense that the two transformers could measure that differently? The pictures below show one transformer with R5 trimmer out of the circuit and then in circuit. Both secondaries on both transformers measure close to each other, but the difference between the two transformers is making me wonder.....

John
Click to expand...
There should be a “delay trigger” function on your scope so that you can see the entire ripple as it dissipates
 
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#2,703
Jack, on digital scopes like the DSO2D15 you simply twirl the horizontal position knob. The digitized waveform data is stored in (digital) memory, and the horizontal position knob just slides the display window left and right across the stored data.

The trigger delay function of old analog CRT scopes, is effectively superseded by very deep waveform memory + horizontal position knob in current day digital scopes.
 
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#2,704
It 'verks!

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#2,707
Hey Folks,
Probably a dumb question, but when searching on Digikey for Quasimodo parts, I don't find IC sockets in the appropriate layouts. I only come up with a 2X2 socket. Can these be snapped apart and "made to work?"
I'm probably missing something obvious here, but wondering what others have done. A secondary search on Mousers website didn't yield great results either. Thank you in advance for any insights you may have.
Dave M.
 
#2,711
UncleMud said:
Hey Folks,
Probably a dumb question, but when searching on Digikey for Quasimodo parts, I don't find IC sockets in the appropriate layouts. I only come up with a 2X2 socket. Can these be snapped apart and "made to work?"
I'm probably missing something obvious here, but wondering what others have done. A secondary search on Mousers website didn't yield great results either. Thank you in advance for any insights you may have.
Dave M.
Click to expand...
Dave, try p/n 437-4108720641001101 for 6 position 2 row socket and p/n 437-4108720841001101 for 8 position 2 row socket. P/N 437-3108310341001101 for 3 position single row. These are Mouser part numbers.

John
 
#2,713
The official parts list for Quasimodo V4 is an Excel spreadsheet, found within the Quasimodo ThruHole .zip archive. That .zip archive is attached to post #1 of the Quasimodo thread. Part numbers for the solder tail sockets are contained in spreadsheet cells H22 and H23. They are DigiKey part number 1212-1157-ND and DigiKey part number 1212-1114-ND .

Those DigiKey parts are 64-position breakaway strips, allowing you to break off a piece having as many terminals as you like. The Quasimodo parts list calls for {two pieces having 3 rows of two pins}, and {two pieces having 4 rows of 2 pins}. You'll use less than half of the 64-position strips, leaving you with plenty of spares for other electronics projects.

If you wish, you can copy the manufacturer's part number from DigiKey's site over to Mouser's site, and find out what number Mouser assigns to them. I did this; the Mouser part numbers are 437-4108726441001101 and 437-3108716441001101 . These are 64-position breakaway strips.
 
#2,715
The LMC555 timer/oscillator chip, the MCP1407 gate-driver chip, and the DIPswitch module, all fit into the "DIP-8" pinout with two columns 0.300" apart and with four rows at 0.100" row-to-row spacing.

If you like, you can use sockets for some or all of them; but the V4 build guide and photos (post #103 in this thread) does not suggest using DIP-8 sockets. And in fact, I have actually recommended against socketing the MCP1407 back in post #286:
Mark Johnson said:
But I'm not sure it's such a good idea to socket the MCP1407 gate driver IC. With Iout = 6 amperes, its dI/dt has got to be incredibly large, so you want the minimum possible inductance in its I/O pins & supply pins. Sockets increase, rather than decrease, inductance.
Click to expand...
Still, if members want to purchase DIP-8 sockets: I had a good experience buying them from Amazon.com in the US {for use in non-Quasimodo projects!}. I purchased 50 pieces three years ago, unfortunately that particular seller has disappeared. However here are a couple of Amazon sellers that I found today (2025 May 29). Amazon Prime shipping is a lot cheaper and also a lot faster than Mouser or DigiKey shipping, in my experience.

Amazon Prime / USD 0.25 per piece / not gold

Amazon Prime / USD 0.45 per piece / gold

MJ
 
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