[car] one Transformer warm, one cold - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

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 4th December 2004, 08:58 PM   #1
andey is offline andey  Germany
diyAudio Member
 
Join Date: Nov 2004
Location: germany
Question [car] one Transformer warm, one cold

Good evening,

After (successfully??) repairing my burnt car amp JBL GTO 6000, i am not sure if everything is fine again.

It has 2 SMPS, one driven by 4, the other one driven by 6 MOSFETS. All Mosfets were shorted. 4 Driving transistors and the TL494 also were dead.

The unit has 2 ring core transformers, the one is about 80% in size of the other one.

Now it runs again, sounds nice and has power, but i am not sure if its fine yet.

The smaller Transformer, driven by the group of 4 Mosfets, gets warm in idle (no speakers/ no cinch connected), the other one stays colder. The warm one goes up to about 50°C (120°F).

Please have a look at the picture. It shows the driving of the 4 fets and the smaller transformer.

I separated the connection at the red A and measured a current of 500mA. The Whole amp is taking 1100mA in idle, so this should be fine 60 to 40 %

Or is 1 Amp too much for idle? I have never measured before


Can anyone tell me if the thingy is fine or i have done crap in my repair?

Thanks very much from germany
andy
Attached Images
File Type: jpg fet2.jpg (31.3 KB, 297 views)
  Reply With Quote
Old 5th December 2004, 09:59 PM   #2
sdoom is offline sdoom  Germany
diyAudio Member
 
Join Date: Mar 2004
Location: Heidelberg
hi


hast du die original MOSFETs und Treiber genommen oder Ersatztypen ? Normal bleiben die Trafos selbst nach ner halben std noch handwarm, 50° ist etwas hoch ohne Last, im Betrieb mit hoher Last werden Sie dann schon noch wärmer. Wie gesagt, ein halbes Ampere pro Netzteil sollte ok sein, viel weiter runter bekommt man den Ruhestrom nicht. Kann aber auch so dimensioniert sein, würde das mal testen wie sich das Netzteil unter Last verhält.



____________ in english _____________________________

Did you use the orig. MOSFET and driving transistors or replacement types ? Usually the transformer cores doin´t get 50°C when idling, only with higher load they get hotter. Idle currents around 0.5A / SMPS is ok.



Steph
  Reply With Quote
Old 6th December 2004, 10:23 AM   #3
andey is offline andey  Germany
diyAudio Member
 
Join Date: Nov 2004
Location: germany
Sdoom,

ich habe Ersatztypen, Original waren FQP 50n06, mein Ersatz ist IRFZ46N.

Unter Last bleibt es weiter so, der kleine Trafo wird viel heißer als der große.

Ein Kollege meinte, eventuell hat der Trafokern einen Riss, da die Endstufe einen Schlag auf die Scheibe abbekommen hat und danach die FETs abgeraucht sind.
Werde mal einen neuen Trafo besorgen, kostet nur ca 10 Euro

english: I replaced Fairchild FQP50n06 with IRFZ46N.
Under loaded condition the smaller transformer also gets much warmer than the large one.

A Friend of mine told me the Ringcore could be broken, which causes the heat. The Amplifier got knocked onto the window, and then the mosfets burnt.

I'll try to get a new transformer which is about 10 bucks.
  Reply With Quote
Old 6th December 2004, 10:42 AM   #4
sdoom is offline sdoom  Germany
diyAudio Member
 
Join Date: Mar 2004
Location: Heidelberg
Hmmm, könnte auch sein, dass die MOSFET´s damit zu tun haben . Wieso hast Du nicht den 48N genommen, der ist meist unkritischer , mit den 46N hatte ich auch schon Probleme .Werden auch die Elkos auf der Primärseite heiss ? Dann ist wahrscheinlich der Tausch der FEt schuld, weil der Ripple current auch zu hoch wird. U.U. musst Du die 22Ohm Widerstände noch austauschen weil die FET zu schnell/langsam schalten. Dass der Kern einen Riss hat wage ich mal zu bezweifeln, normal sind das Presseisenkerne, also ziemlich robust. Hatte schon mehrere Endstufen aus Unfallautos die ziemlich demoliert waren (gebrochene Platine usw), aber die Kerne waren noch nie hops. Hab nur mal einen magnetisch/elektr.(Funken durch Kurzschluss) zerstörten gesehen, und das sieht man auf alle Fälle, der ist voll zerbröselt.

____________________in english______________________

Maybe it´s the MOSFETs switching too fast/slow so you would have to change the resistors. Usually the cores don´t break. I had several amplifiers taken out off accident-cars that really looked wrecked and had broken PCB, but the transformer cores had all been ok. I had only one broken core and that had a magn. problem or the wires had been burned (DC short) , there was a big part missing that had been exploded.
  Reply With Quote
Old 6th December 2004, 11:05 AM   #5
andey is offline andey  Germany
diyAudio Member
 
Join Date: Nov 2004
Location: germany
i think we understand ourselves when we write everything in english.

would you have a look at the datasheets of my parts? One is available at irf.com, the other one at fairchildsemi.com

i didnt pick irfz44n because of the lower pulse current, and i didnt pick the 48n because of the high input capacitance, and someone here told me they have more heat loss, as higher their nominal current is.

Which gate resistors should i use?
do you need the voltage on the gate transistors measured to tell me that?

i also had to change driving transistors. the 1266s are hard to get here so i just used BC640 because they have the same pinout. I didnt check the parameters 1266 vs 640 really deep. Could there be a problem with them?

As said i changed all 10 mosfets, but the trnsformer driven by the 6 mosfets runs fine and cold.

I have a scope at home atm, so i could check things if you want.

Can the TL494 be ran with a fixed pulsewidth?
the pulsewidth does not change, no matter how i load the amp. Always the same width.

I can send you pics of the pcb if you want, perhaps we could also continue our discussion on icq. get me a private message if you want so.

thanks a lot
andy
  Reply With Quote
Old 6th December 2004, 12:59 PM   #6
sdoom is offline sdoom  Germany
diyAudio Member
 
Join Date: Mar 2004
Location: Heidelberg
hi

kannst mir mal ne mail schicken, bin nicht zu hause momentan.

sdoom@freenet.de
  Reply With Quote
Old 6th December 2004, 01:12 PM   #7
sdoom is offline sdoom  Germany
diyAudio Member
 
Join Date: Mar 2004
Location: Heidelberg
Hmm, from what I have seen on the datasheets the IRFZ46N has higher capacities, so you should try to make the resistors smaller, maybe around 10-15Ohm. Try the "hot transformer" first. Man could assume, that due to the higher capacities, the IRFZ46N is switching slower causing the small core to run instable and therefore generating more heat...

but it could also be that everything is fine and the core is a cheap one and JBL just didn´t care if it gets hot , or not ;o)
  Reply With Quote
Old 2nd October 2005, 09:07 AM   #8
diyAudio Member
 
Join Date: Oct 2005
Hi
Got some problems with my JBL GTO 6000; it pulses on and off about 1 sec between. Do you have the diagrams or repair instructions for this amp?

Oddmundb
  Reply With Quote
Old 2nd October 2005, 09:39 AM   #9
sdoom is offline sdoom  Germany
diyAudio Member
 
Join Date: Mar 2004
Location: Heidelberg
Hi

If your amp stays in protect mode and tries to turn on every second there´s most likely a short in one ore more off the output power transistors. Those should be the 2SB688 and 2SD718 power transistors mounted onto the heatsink.

get an Ohmmeter and check each leg of the power transistor . You will probably find a 100% short at one ore more power transistors. If you find it , cut the transsitor out.

Then look for the driving transistors. Those are smaller ones , should be KTA1023 and KTC1027 . Those drive the big power transistors. Again check those smaller transistors for a short but usually those stay ok. If so, get a replacement for the big power transistor. if you cannot find the 2SB688 or 2SD718 you can use the KTB778 and KTD998 as a direct replacement. If you cannot find those use a TIP35C and TIP36C (=BD249C and BD250C in Europe) .


But remember , even if there is just one transistor burned, e.g. the SB688 you have to replace both transistors !!!



Steph
  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
Should the sound be warm or cold? michaelpage26 Multi-Way 14 31st December 2005 08:39 PM
Electronics in the cold leadbelly Everything Else 0 31st January 2004 07:42 PM
bias amp while hot or cold? nicksmurf Solid State 5 28th June 2003 07:56 AM
How Cold Is it? kelticwizard Everything Else 17 18th February 2003 04:30 PM


New To Site? Need Help?

All times are GMT. The time now is 05:01 PM.


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