Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Instruments and Amps Everything that makes music, Especially including instrument amps.

The dumbest thing I've ever seen in amp construction....
The dumbest thing I've ever seen in amp construction....
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 16th May 2019, 06:44 AM   #21
dreamth is offline dreamth  Romania
diyAudio Member
 
Join Date: Nov 2010
I bet that this amp worked for a long time with no problem and many artists were delighted using it...
  Reply With Quote
Old 16th May 2019, 11:18 AM   #22
Tubelab_com is offline Tubelab_com  United States
diyAudio Member
 
Tubelab_com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
I thought the dumb thing was how close the two power tubes are to each other.
That was my first thought as well and probably contributed more problems than the transformers.

GE routinely welds their cores to the frame in many of their Industrial Control Transformers. Yes, they run hot since their core is barely sized big enough for the power rating. The welding may contribute a percent or two to the total losses in the transformer, but it cuts down on the buzzing from the core.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 16th May 2019, 11:41 AM   #23
Kay Pirinha is offline Kay Pirinha  Germany
diyAudio Member
 
Kay Pirinha's Avatar
 
Join Date: Oct 2011
Location: Somewhere in Germany
Due to cost cutting, welding transformers instead of screwing has become very common during the last decades. Even most of the laminations' alloys are composed to be welded nowadays. Transformer manufacturers even don't swap the E I arrangement with every single lamination when assembling the core, instead they put all the E's from one side and the I's to the other, just to ease welding.

I don't see a significant issue with this. Yes, the lam's still are isolated, preferably by oxide surfaces. Now it is your's to imagine how the flux travels through the core: Isolated lam's instead of a solid iron core has the huge advantage that there isn't closed circle, i.e. a virtual short widing perpendicular to the flux. This remains even with welded cores, as the welding just forms an open straight line instead of a circle. Hence, losses caused by the weldings can be neglected.

One could suspect, though, that weldable laminations are of inferior quality when compared with GOSS, for instance. Hence, increased losses were a matter of laminations quality, not of the welding process per se.

Best regards!
__________________
"Bless you, Sister. May all your sons be bishops." (Brendan Behan)
  Reply With Quote
Old 16th May 2019, 01:27 PM   #24
cmjohnson is offline cmjohnson  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Florida
What some of you are missing is that the location of the weld across the laminations isn't important. The fact is that the laminations are ELECTRICALLY shorted and as current always follows the easiest path, welding across the laminations means that any current within the lamination is going to flow through the weld.

It reduces efficiency and creates unnecessary heating. If the designer is willing to accept that compromise and has sized the core to withstand the additional heating, that's his choice.

But I'm not under any sort of mistaken impression that Peavey's designers knew what they were doing.

When I see a welded transformer in a Peavey amp I do the only thing that is appropriate: Shake my head and walk away laughing.
  Reply With Quote
Old 16th May 2019, 10:14 PM   #25
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
Welding on the outside of the laminations creates no current loops, so not a problem. If you welded on the inside _and_ outside of the core, that would be a shorted link and the core would overheat and possibly melt. Flux has to cut a full loop to cause any current to flow.

This is the same as when aluminium voice-coil formers have a slit - not a complete loop so no current flows in the former.

Its also why having bolts going through the lam stack isn't a problem.
  Reply With Quote
Old 17th May 2019, 12:37 AM   #26
Printer2 is offline Printer2  Canada
diyAudio Member
 
Join Date: Apr 2010
I have seen transformers welded across the laminations, I think it was for a microwave. I found it odd the first time I saw it but thought it might be for vibration. Might be around here somewhere yet. As said, if it does not make a complete loop it is an unshorted conductor.
  Reply With Quote
Old 17th May 2019, 12:40 AM   #27
Tubelab_com is offline Tubelab_com  United States
diyAudio Member
 
Tubelab_com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Most microwave oven transformers are welded.....makes them nearly impossible to take apart......bummer. The way the bobbins are made would make for an easy rewind.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 17th May 2019, 12:46 AM   #28
dreamth is offline dreamth  Romania
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by trobbins View Post
if anything it is leakage flux from air returning to the core in that location.
Well spoken Sir!
There are lots of designs that look flawed yet there's no problem with them.
  Reply With Quote
Old 17th May 2019, 01:33 AM   #29
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
The dumbest thing I've ever seen in amp construction....
some explanations in this old thread: Welded transformer stack- good, bad?
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 17th May 2019, 03:15 AM   #30
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
As mentioned earlier, many problems arise from mutually excluding black-white thinking, while Reality is made out of all kinds of grey.

"transformer laminations are isolated" .... well, yes and no
If you measure resistance pressing both probes on a lamination surface, whether same side or opposite ones, you will *generally* measure lack of continuity.
Yes, all varnish and most oxide treatments are insulating and are applied for that reason.

BUT

if you have an assembled transformer and measure resistance from one lamination to another in the stack, whether itīs the next one or they are at opposite sides of it, you will usually measure continuity
Such a low value of resistance that it approaches a short

I guess our friend has never made that simple test which I suggest he carries on for his own peace of mind

and the reason for that is that EI laminations are punched out of a sheet of surface treated steel , so surface is insulating, BUT edges are sharp, *naked* and happily touch each other so all laminations in a stack are connected/shorted by the edges.

But then, whatīs the point of insulating them at all?
Or even using stacked laminations instead of a solid core?

Point is, and here lies the key, that there are "shorts" and "SHORTS" and everything in between.

Consider a stack of laminations: IF they are unvarnished, lamination to lamination across the full stack resistance may be 0.0001 ohm ... but if they contact just by the edges, same stack resistance is WAY higher, say 0.01 ohm.

Are both the same?
YES to Black/White mentality
NO to a realistic one.

As different as one having 100 times more losses than the other

---------------------------------------

As of welding across laminations, corners are almost/practically outside of the magnetic lines path, so welding "short" is not a game changer.
Specially considering lamination sharp edges/burrs are already connected to each other ... with little negative effect.
__________________
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
  Reply With Quote

Reply


The dumbest thing I've ever seen in amp construction....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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Maybe the dumbest question of all-time. If an amp relay is bad, is it really bad?? joeljoel1947 Solid State 20 9th October 2017 06:09 PM
No such thing as a 32-bit DAC! stephensank Digital Line Level 62 16th December 2015 11:05 AM
dumbest question ever i.e. equipment sequence rmcelroy Everything Else 3 27th July 2010 02:44 PM
Is this the dumbest question? duderduderini Tubes / Valves 2 6th May 2008 04:00 PM
dumbest question eV4R! Hybrid fourdoor Chip Amps 2 14th September 2003 11:22 AM


New To Site? Need Help?

All times are GMT. The time now is 11:43 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki