F5 power amplifier - Page 512 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th October 2009, 02:49 AM   #5111
Variac is online now Variac  United States
diyAudio Editor
 
Variac's Avatar
 
Join Date: Dec 2001
Location: San Francisco, USA
To repair rotted wood in boats we use something called "Penetrating Epoxy"
It flows like water. I don't know if it would damage the insulation on transformer wires (I doubt it ) West Marine has it.
  Reply With Quote
Old 8th October 2009, 07:14 AM   #5112
Banned
 
Join Date: Nov 2006
This perfectly illustrates one reason why not to use an under rated transformer.
The time, cost an effort to fix a buzzing transformer is a lot more than forking out a few more dollars for a higher rated transformer, which would avoid the problem all together in the first place.
  Reply With Quote
Old 8th October 2009, 09:51 AM   #5113
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Quote:
Originally Posted by Variac View Post
something called "Penetrating Epoxy"
Mark,

whether it's West or any other brand, penetrating epoxy is the plain deal with two shots of extra solvent.

For transformers and all other coils : 3M Scotchcast 280
Best way to use is with vacuum injecting and autoclave curing.
For the autoclave thing, just bang it in the oven at 120C or build a fancy DIY one, lots of examples on the web.
Same story for vacuum injecting, it is easier than one might think.
(long time ago me had a sabbatical at an airplane factory where they did prepreg resin/kevlar cure stuff in huge autoclaves)
  Reply With Quote
Old 8th October 2009, 10:19 AM   #5114
diyAudio Member
 
Join Date: Jun 2006
Quote:
Originally Posted by scranton View Post
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.
could you replace transformers and see
  Reply With Quote
Old 8th October 2009, 02:12 PM   #5115
labjr is offline labjr  United States
diyAudio Member
 
Join Date: Apr 2003
Location: MA
Quote:
Originally Posted by thanh1973 View Post
This perfectly illustrates one reason why not to use an under rated transformer.
The time, cost an effort to fix a buzzing transformer is a lot more than forking out a few more dollars for a higher rated transformer, which would avoid the problem all together in the first place.
250 VA per monoblock doesn't seem like under-rated transformers. The stereo F5 has a 300VA transformer. Though this seems like a reason to choose a brand of well-made transformers. I would think Avel transformers are good quality.
  Reply With Quote
Old 8th October 2009, 03:26 PM   #5116
Banned
 
Join Date: Nov 2006
I am not suggesting that in this specific case that an under rated transformer was used.
But this is exactly what will happen if you use an under rated transformer.

Hi scranton what voltages and bias current are you using in your F5 amp?
  Reply With Quote
Old 8th October 2009, 04:44 PM   #5117
Renron is offline Renron  United States
diyAudio Member
 
Renron's Avatar
 
Join Date: Jan 2007
Location: Sacramento
Quote:
Originally Posted by jacco vermeulen View Post
Mark,

whether it's West or any other brand, penetrating epoxy is the plain deal with two shots of extra solvent.

For the autoclave thing, just bang it in the oven at 120C or build a fancy DIY one, lots of examples on the web.

Great idea, great results too. But.....
DON'T USE YOUR HOUSEHOLD OVEN FOR THIS! Toxic fumes result and will contaminate the interior of the oven. An excellent alternative would be a small toaster oven or a DIY oven as Jacco suggested.
Your "other half" would be P!ssed.


Quote ""an amp so simple, even a cave man could build it"
I screwed mine up and am getting help on the rebuild from Steve Eddy. Thanks Steve!

Ron

Last edited by Renron; 8th October 2009 at 04:51 PM. Reason: "an amp so simple, even a cave man could build it"
  Reply With Quote
Old 8th October 2009, 04:59 PM   #5118
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by labjr View Post
Though this seems like a reason to choose a brand of well-made transformers. I would think Avel transformers are good quality.
Very true
But having hum in one speaker indicates there may be another small problem as well
Significant or not, I dont know
It plays fine as is
Good
Though I have had one experience with a certain amp
It sounded fine, and I had no idea that it was unstable and unreliable
But when the printboards on one channel was literally on fire, I knew
Unreliable amps can be very dangerous

Last edited by tinitus; 8th October 2009 at 05:07 PM.
  Reply With Quote
Old 8th October 2009, 07:23 PM   #5119
diyAudio Member
 
Join Date: Jun 2005
Location: Massachusetts
Thanks Tinitus and others: I reversed channels and disconnected signal and output and the transformer still buzzed after warmup. With no load, I did the adj again and I see the DC offset more unstable than before, fluctuating 8-10 mv around zero (Is negative DC offset an issue?) The voltage on R11 and 12 is steady at .585v which I adjusted slightly to keep offset above zero. I do think I have two problems: instability due to earlier mistakes and a transformer.
The heatsink comment earlier struck home. AT 6X9X3 per amp I was concerned about using them in 2 converted Bogen PA chassis(pl). For a novice it works so well. I assumed they would get hot as hell if inadequate. I can touch both of them as long as I want. Does the heat instead get absorbed/dissipated by the mosfet and source resistors? R11 and 12 look overheated. I used the fabric-like insulators.
Thanks for all the tips/ With a set of great PD boards and parts I am going to rebuild and get another transformer and contemplate Conrad heatsinks. Thanks
I don't think I will repot the transformer
But if it can be done, whatever it is, someone here will know.
  Reply With Quote
Old 8th October 2009, 07:29 PM   #5120
daly41k is offline daly41k  United States
diyAudio Member
 
Join Date: Feb 2007
Location: Phillipsburg, New Jersey
Default 5 channel F-5

I was thinking of building a five channel F-5 for a home video application, has anyoned done this? I have a couple of 2kva @ 45 volt trannies left over from another project. I could use one and of course I would have to step down the voltage but I can do it. Feed it multiple power supplies for each channel and I think the 25-50 watts would be enough. The speakers already have powered subs so I am just pushing the tweeters and mids in the front and the back speakers don't need much power. As always the case and heatsinks are the big issues. I have a couple of AX140's I built based on the AX100 thread but these are way toooooo big and run too hot for a living room application. Actually too good to waste on home video. Just curious as winter is coming up and I have to stay busy. dave
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Rockford Fosgate Power 20001 bd amplifier power rating?? pachoorion Car Audio 8 8th May 2011 10:49 PM
Power transformers versus amplifier output power..what is your option? destroyer X Solid State 38 9th May 2009 05:23 PM
McIntosh Power Amplifier Power Guard johnnyrt Solid State 2 23rd August 2007 10:22 PM
Output power for a power amplifier Progg70 Solid State 33 10th September 2006 08:44 AM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality MARAVILLASAUDIO Class D 1 5th November 2004 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 07:04 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2