DIY UcD thermal tracking circuit

oldmaelstrom2 · 24th April 2006, 08:56 AM

Hi to all. Anyone have ideas about thermal tracking in DIY UcD?
Best regards.

classd4sure · 24th April 2006, 06:38 PM

Hi.

With respect to what?

Nice work.

oldmaelstrom2 · 24th April 2006, 06:44 PM

After power up swithing frequency slowly decrease, then stop. After few minutes it goes up. I think is thermal unstability.

classd4sure · 24th April 2006, 06:52 PM

What's the frequency variation like? How long before it settles?

Have you measured it again after it's been loaded down?

Have you further tried to narrow down the offensive part by say.. applying cold spray.. or hot air?

Something so simple as a better selection of input pair transitors (lower parasitics) could possibly help minimize this.. if they're to blame, even epoxying them together perhaps. Find the guilty party first though.

Might check out the components in the feedback loop as well.

Neat problem

oldmaelstrom2 · 24th April 2006, 06:56 PM

Thanks I try your recomendations.

oldmaelstrom2 · 24th April 2006, 06:59 PM

Ok. If its not thermal unstability, what this may be?

classd4sure · 24th April 2006, 07:04 PM

Quote:

Originally posted by oldmaelstrom2
Ok. If its not thermal unstability, what this may be?

Why have you given up on the idea so soon?

oldmaelstrom2 · 25th April 2006, 05:03 PM

Hi. I try worm air upon a pcb - result: the swithing freq. is increase.
Then i glue together transistors in diferential amplifier all work fine. The freq is changing from 350 khz to 348khZ, then increasing to 352khz, so i have +/- 5 khz unbalance. Its normal or not. How is fixed in original UcD modeles from HYPEX?
Best regards.

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24th April 2006, 06:38 PM	#2
classd4sure Account Disabled Join Date: Feb 2004	Hi. With respect to what? Nice work.

24th April 2006, 06:44 PM	#3
oldmaelstrom2 diyAudio Member Join Date: Nov 2005	After power up swithing frequency slowly decrease, then stop. After few minutes it goes up. I think is thermal unstability.

24th April 2006, 06:52 PM	#4
classd4sure Account Disabled Join Date: Feb 2004	What's the frequency variation like? How long before it settles? Have you measured it again after it's been loaded down? Have you further tried to narrow down the offensive part by say.. applying cold spray.. or hot air? Something so simple as a better selection of input pair transitors (lower parasitics) could possibly help minimize this.. if they're to blame, even epoxying them together perhaps. Find the guilty party first though. Might check out the components in the feedback loop as well. Neat problem

24th April 2006, 06:56 PM	#5
oldmaelstrom2 diyAudio Member Join Date: Nov 2005	Thanks I try your recomendations.

24th April 2006, 06:59 PM	#6
oldmaelstrom2 diyAudio Member Join Date: Nov 2005	Ok. If its not thermal unstability, what this may be?

25th April 2006, 05:03 PM	#8
oldmaelstrom2 diyAudio Member Join Date: Nov 2005	Hi. I try worm air upon a pcb - result: the swithing freq. is increase. Then i glue together transistors in diferential amplifier all work fine. The freq is changing from 350 khz to 348khZ, then increasing to 352khz, so i have +/- 5 khz unbalance. Its normal or not. How is fixed in original UcD modeles from HYPEX? Best regards.

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