F5 power amplifier - Page 511

jleaman · 7th October 2009, 04:46 AM

Quote:

Originally Posted by thanh1973

Two Pack Epoxy

no work,

NOT GOOD EITHER!

Melon Head · 7th October 2009, 06:11 AM

Have you tried it?
This is what all the manufacturers use.

If you want better then polyurea or polyurethane would be better. If you want to improve on that then fill it with very dense pigments.

bobodioulasso · 7th October 2009, 08:47 AM

I have poted one into an aluminium pan using silicone. That made it silent but i do not know about the long time.

Melon Head · 7th October 2009, 09:58 AM

Silicone has some nice properties, as good as or possibly better than polyurethane

bobodioulasso · 7th October 2009, 10:09 AM

Heat sinking might be an issue?
It coud become a torrid transformer.

AuroraB · 7th October 2009, 10:13 AM

For potting a transformer, use the special compounds developed for potting- available from most professional parts suppliers, an nusually not more expensive than the amount of epoxy required.

Vacuum impregnating the core/windings of a trafo is something else - this is done with very low viscosity laquers to get into the windings. Can't be done with normal potting compounds....

scranton · 7th October 2009, 03:35 PM

Labjr: Which transformer are you using?

Hi

The Avel 250va 18v + 18v dual secondaries. It had been working fine. The same transformer in the other monoblock is working. I do have a very slight hum in that speaker, but it doesn't change when the transformer starts making the noise. Thanks for your repllies. Even with this problem the F5 is performing very nicely.

labjr · 7th October 2009, 07:30 PM

Does one chassis buzz more than the other one if you put your ear to it?

I don't know if a noisy transformer will make a hum through the speaker. Maybe someone else can answer this.

scranton · 7th October 2009, 07:43 PM

Just the one transformer buzzes. I can hear it faintly from 3 feet away. And that unit's speaker has a very minor hum that I can only hear withmy ear on the thing and I hear it from start up. The transformer develops the buzz an hour after startup. The other monoblock makes no chassis noises and the speaker is perfectly quiet.

About this time I did do a mod on my cd player. Bypassed the output caps per Kit Ryan's .
suggested mods in Audio xpress. Could this be related? Cd is attached to B1 that is attached to F5. Thanks for help.

tinitus · 08:35 PM

You could try disconnect your signal/B1, to see if it still hums
Or reverse channels from your signal/B1, to see if it follows signal
Also examine if wireing is slightly different on left/right channel

Your hum and buzz might still be two different things
Nelson have said that hum might be an indication of minor instability
And that it may be related to signal wire/grounding

As said earlier, even the slightest transformer buzzing can be "amplified" by the enclosure, and sound much worse
Without the box you might not hear anything

edit, do your supply caps get hot ?

7th October 2009, 10:13 AM	#5106
AuroraB diyAudio Member Join Date: May 2001 Location: Norway, -north of the moral circle..	For potting a transformer, use the special compounds developed for potting- available from most professional parts suppliers, an nusually not more expensive than the amount of epoxy required. Vacuum impregnating the core/windings of a trafo is something else - this is done with very low viscosity laquers to get into the windings. Can't be done with normal potting compounds.... __________________ While the Lie leapt from Bagdad to Constantinopel, the Truth was still looking for it's sandals!

7th October 2009, 08:28 PM	#5110
tinitus diyAudio Moderator Join Date: Nov 2005	You could try disconnect your signal/B1, to see if it still hums Or reverse channels from your signal/B1, to see if it follows signal Also examine if wireing is slightly different on left/right channel Your hum and buzz might still be two different things Nelson have said that hum might be an indication of minor instability And that it may be related to signal wire/grounding As said earlier, even the slightest transformer buzzing can be "amplified" by the enclosure, and sound much worse Without the box you might not hear anything edit, do your supply caps get hot ? Last edited by tinitus; 7th October 2009 at 08:35 PM.

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7th October 2009, 06:11 AM	#5102
Melon Head Formerly Thanh1973 Join Date: Nov 2006	Have you tried it? This is what all the manufacturers use. If you want better then polyurea or polyurethane would be better. If you want to improve on that then fill it with very dense pigments.

7th October 2009, 08:47 AM	#5103
bobodioulasso diyAudio Member Join Date: May 2008 Location: On the moon.	I have poted one into an aluminium pan using silicone. That made it silent but i do not know about the long time.

7th October 2009, 09:58 AM	#5104
Melon Head Formerly Thanh1973 Join Date: Nov 2006	Silicone has some nice properties, as good as or possibly better than polyurethane

7th October 2009, 10:09 AM	#5105
bobodioulasso diyAudio Member Join Date: May 2008 Location: On the moon.	Heat sinking might be an issue? It coud become a torrid transformer.

7th October 2009, 03:35 PM	#5107
scranton diyAudio Member Join Date: Jun 2005 Location: Massachusetts	Labjr: Which transformer are you using? Hi The Avel 250va 18v + 18v dual secondaries. It had been working fine. The same transformer in the other monoblock is working. I do have a very slight hum in that speaker, but it doesn't change when the transformer starts making the noise. Thanks for your repllies. Even with this problem the F5 is performing very nicely.

7th October 2009, 07:30 PM	#5108
labjr diyAudio Member Join Date: Apr 2003 Location: MA	Does one chassis buzz more than the other one if you put your ear to it? I don't know if a noisy transformer will make a hum through the speaker. Maybe someone else can answer this.

7th October 2009, 07:43 PM	#5109
scranton diyAudio Member Join Date: Jun 2005 Location: Massachusetts	Just the one transformer buzzes. I can hear it faintly from 3 feet away. And that unit's speaker has a very minor hum that I can only hear withmy ear on the thing and I hear it from start up. The transformer develops the buzz an hour after startup. The other monoblock makes no chassis noises and the speaker is perfectly quiet. About this time I did do a mod on my cd player. Bypassed the output caps per Kit Ryan's . suggested mods in Audio xpress. Could this be related? Cd is attached to B1 that is attached to F5. Thanks for help.

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