My Gemsound 4505 is BUSTED!
Anyone around the Newcastle area able to take a look at my 4505. I had been using for around 2 months as my main amp with out any issues. It pretty much got daily usage. So i packed it up because i got a new setup.
Unpacked it Saturday night at a gig. Wired it up flicked the switch and POP. Brief blue spark was seen in the front of the unit and both fuses were blown. I unplugged everything from the amp and switched out the fuses with new ones which also blew.
So yeh if someone can recommend someone around the Newcastle area that would be great.
Anyone around the Newcastle area able to take a look at my 4505. I had been using for around 2 months as my main amp with out any issues. It pretty much got daily usage. So i packed it up because i got a new setup.
Unpacked it Saturday night at a gig. Wired it up flicked the switch and POP. Brief blue spark was seen in the front of the unit and both fuses were blown. I unplugged everything from the amp and switched out the fuses with new ones which also blew.
So yeh if someone can recommend someone around the Newcastle area that would be great.
Sorry DJ I can't help you out there mate... I don't know how much your knowledge is when it comes to amplifiers etc... But when you do get it fixed, I STRONGLY encourage you to have the serviceman insall another pair of Output transisters... It is a bit more work, but these amps are designed on absolute limits of the component ratings (probably not even sufficient) and a bit more load sharing of the OPT's will add to the reliability... Notice I did call this amp 'Nosound' NOT Gem sound in an earlier thread...
Goodluck....
Ed.
Goodluck....
Ed.
Eddie Wolve said:
Just make sure you put in the emitter and base stopper resistors for the extra OPT pairs, or the extra expense will be for nothing.
An older QSC of similar rating (400/ch, 8 ohms) with the same supply rails uses 8 pairs of MJ15024/5 outputs. Those will almost never blow outputs, even when running 2 ohms, but the associated heat produced will cause them to cut out in the middle of gigs and have electrolytic cap failures.
The amp lasting only 20 seconds with only 5 pairs is par for the course.
Nordic said:
Wouldn't expect it to. With only +/-38 volt supplies you could use 2N3055's and it would hold up. Distortion might be a little higher than with the better transistors, but the SQ of "blameless" amps tends to be more a function of the front end and proper layout techniques.
type of OPT's
Hi Eddie, I've got a mate looking at my amp whose a bit of guru when it come to these things. What do u think of the idea of putting higher rated OPTs rather than the extra ones? Exactly whats involved in adding the extra pair? Also what kind did u replace yours with? And how's it testing up?
Hi Eddie, I've got a mate looking at my amp whose a bit of guru when it come to these things. What do u think of the idea of putting higher rated OPTs rather than the extra ones? Exactly whats involved in adding the extra pair? Also what kind did u replace yours with? And how's it testing up?
Hi DJ.
There are probably plenty of others in this forum more qualified than me on that topic, but I also considered replacing the OPT's with higher rated ones, but at the end of the day, there are not many 'off the shelf' OPT's here in Oz that are actually more rugged than the 5200's and 1943's, and reasonably priced. At the end of the day, the original circuit was designed for these OPT's (ie power supply voltage, protection circuitry etc).. Plus it saved me having to replace 24 pairs of OPT's...
All I did was replace those horrible mica washers, cleaned the heatsink up, (got rid of all the burrs etc -), added the extra components to the Power Amp main PCB (ie Emitter and Base resistors) and added the extra OPT's. I also slightly increased the quiescent current to account for the extra OPT's... (I had the 2nd channel to determine what the bias current was and just increased the fixed channel to suit).
So far it has run OK, on 4 ohm loads, but I haven't pushed it that hard (ie clip leds just flashing sometimes) and it has not missed a beat (So far....) It does get very warm however...But I would NEVER run it in Bridge mode...
ALSO, check the main supply fuses.... Mine had 2 x 15Amp fuses...out of the box, so was probably ment for 110V supplies.. I changed them to 7 amp and they have not blown yet...
Good luck and let me know how you went...
There are probably plenty of others in this forum more qualified than me on that topic, but I also considered replacing the OPT's with higher rated ones, but at the end of the day, there are not many 'off the shelf' OPT's here in Oz that are actually more rugged than the 5200's and 1943's, and reasonably priced. At the end of the day, the original circuit was designed for these OPT's (ie power supply voltage, protection circuitry etc).. Plus it saved me having to replace 24 pairs of OPT's...
All I did was replace those horrible mica washers, cleaned the heatsink up, (got rid of all the burrs etc -), added the extra components to the Power Amp main PCB (ie Emitter and Base resistors) and added the extra OPT's. I also slightly increased the quiescent current to account for the extra OPT's... (I had the 2nd channel to determine what the bias current was and just increased the fixed channel to suit).
So far it has run OK, on 4 ohm loads, but I haven't pushed it that hard (ie clip leds just flashing sometimes) and it has not missed a beat (So far....) It does get very warm however...But I would NEVER run it in Bridge mode...
ALSO, check the main supply fuses.... Mine had 2 x 15Amp fuses...out of the box, so was probably ment for 110V supplies.. I changed them to 7 amp and they have not blown yet...
Good luck and let me know how you went...
Thanks heaps for all your help Eddie. Just wondering where you sourced your 2SC5200's from and how much you paid?
Hi DJ..
I have a trade account with Wes Components, but they have a retail store here :
http://www.wagner.net.au/
As far as I know, they stock the real Toshiba OPT's, not cheap copies.... The trade list price is $6.45 each, so you might pay a bit more...
Regards,,
Ed
I have a trade account with Wes Components, but they have a retail store here :
http://www.wagner.net.au/
As far as I know, they stock the real Toshiba OPT's, not cheap copies.... The trade list price is $6.45 each, so you might pay a bit more...
Regards,,
Ed
A diode also blew. Does it matter what type i use to replace it? I know it has to be heavy duty. Just wondering if there is a difference.
That's a really hard question to answer without knowing what diode it actually is..!
If you read my earlier posts in this thread, you will find I had one go pop too, that was just a standard rectifier type diode... a 1N4007 from memory.... It has a rating of 1 amp.. I would not change this, as it turns out, it acts as a type of protection when it goes 'pop' (ie shorts out causing fuses to blow) from memory...
If you 'up-rate' the diode it may cause other (more expensive) components 'down circuit' to blow if you have a similar fault occur in the future..
Read the markings on the diode, if that's what it is, I would replace with the same one... If you want to up-rate it, go for a 1N5408 (3 amp) one..
Regards,
Ed.
If you read my earlier posts in this thread, you will find I had one go pop too, that was just a standard rectifier type diode... a 1N4007 from memory.... It has a rating of 1 amp.. I would not change this, as it turns out, it acts as a type of protection when it goes 'pop' (ie shorts out causing fuses to blow) from memory...
If you 'up-rate' the diode it may cause other (more expensive) components 'down circuit' to blow if you have a similar fault occur in the future..
Read the markings on the diode, if that's what it is, I would replace with the same one... If you want to up-rate it, go for a 1N5408 (3 amp) one..
Regards,
Ed.