Jaycar Playmaster Subwoofer Amp Kit
Hey guys.
This would be my first post/thread in this forum and hopefully not the last.
I purchased, a few years ago, one of these amps and have had it connected to a single 4 ohm Rockford Fosgate 18in sub. It has been working perfectly since I built way back when.
That was until the other day when I moved it and touched the RCA input leads whilst it was on. It made a VERY loud buzz and then nothing. All it does now is blow fuses.
I have basic knowledge on electronics but that would be the limit. I have ever-so-slowly pulled out/replaced basic parts (e.g. resistors, diodes and caps) with no luck.
My question to you all knowing Gurus
is how to test the power mosfets? The amp uses three 2SK1058 and three 2SJ162.
Please help - DVDs are just not any good now without it.
Thanks, Liam.
Hey guys.
This would be my first post/thread in this forum and hopefully not the last.
I purchased, a few years ago, one of these amps and have had it connected to a single 4 ohm Rockford Fosgate 18in sub. It has been working perfectly since I built way back when.
That was until the other day when I moved it and touched the RCA input leads whilst it was on. It made a VERY loud buzz and then nothing. All it does now is blow fuses.
I have basic knowledge on electronics but that would be the limit. I have ever-so-slowly pulled out/replaced basic parts (e.g. resistors, diodes and caps) with no luck.
My question to you all knowing Gurus
is how to test the power mosfets? The amp uses three 2SK1058 and three 2SJ162.Please help - DVDs are just not any good now without it.
Thanks, Liam.
Sorry guys I did a further search and found a link to a really good site - bcae1.com and found out how to test the FETs.
Whilst I still have your attention; I won't be able to test these for a couple of days so I'd like to hear your opinion on what might be wrong with the amp other than the FETs.
Whilst I still have your attention; I won't be able to test these for a couple of days so I'd like to hear your opinion on what might be wrong with the amp other than the FETs.
I don't know how to check the mosfets, but I'd be looking for a short on the output.
If it's a classic playmaster design it will have an RLC ciruit on the speaker output (a cap and a coil). Check the cap and make sure that it hasn't gone short circuit. also look for any loose wires that may be shorting (at the speaker).
I've blown the fuses in my playmaster 200 a number of times when I've had a short on the speaker terminals (even a single strand of speaker wire will do it).
Tony.
If it's a classic playmaster design it will have an RLC ciruit on the speaker output (a cap and a coil). Check the cap and make sure that it hasn't gone short circuit. also look for any loose wires that may be shorting (at the speaker).
I've blown the fuses in my playmaster 200 a number of times when I've had a short on the speaker terminals (even a single strand of speaker wire will do it).
Tony.
I have found some time and pulled a couple of the suspect Trannys out and as per the "Output Transistor Failure" guide on http://www.bcae1.com It seems all of them are faulty. They are all reading shorts, or near enough, between pins two and three (with metal back facing away)
You might want to read these two links as well.
http://www.tpub.com/content/neets/14193/css/14193_65.htm
http://www.uoguelph.ca/~antoon/gadgets/mostest.htm
The second one suggests that the drive transistors may also be blown, since they will likely be much cheaper than the mosfets would probably be a good idea to replace them as well. At $18 a pop for the mosfets, it could get very expensive trouble shooting this amp!
Tony.
http://www.tpub.com/content/neets/14193/css/14193_65.htm
http://www.uoguelph.ca/~antoon/gadgets/mostest.htm
The second one suggests that the drive transistors may also be blown, since they will likely be much cheaper than the mosfets would probably be a good idea to replace them as well. At $18 a pop for the mosfets, it could get very expensive trouble shooting this amp!
Tony.
SkinnyBoy said:
Hey skinny boy, the second site I linked to pretty much says that if one goes it usually takes the rest with it, and often the stage before the outputs too! Nasty stuff. I too at first thought maybe the test methodology was dodgy, but both the sites I found had pretty much the same test as Liam found. And the first sites test I think has been sourced from the Military!
Tony.
You probably still need to determine what caused them to blow in the first place! You don't want to replace them all and have them blow again!!!
touching the inputs wouldn't IMO be enough to blow the output mosfets, sure it will cause hum, and maybe you will act as an arial for RF but....... I assume that the fuses that are blowing are in the + and - rails of the actual amp, and not in the AC before the power supply. Generally speaking I think that the fuses should blow before any damage to the output devices occurs (assuming it's designed properly).
I'm no expert on this BTW, maybe you should seek another opinion! And maybe even see if you can find someone who's willing to test your mosfets for you.
Tony.
edit: Maybe you could ask the mods to change the title of the thread to Help finding fault with Playmaster Sub AMP. Might get more (of the right) people reading it.
touching the inputs wouldn't IMO be enough to blow the output mosfets, sure it will cause hum, and maybe you will act as an arial for RF but....... I assume that the fuses that are blowing are in the + and - rails of the actual amp, and not in the AC before the power supply. Generally speaking I think that the fuses should blow before any damage to the output devices occurs (assuming it's designed properly).
I'm no expert on this BTW, maybe you should seek another opinion! And maybe even see if you can find someone who's willing to test your mosfets for you.
Tony.
edit: Maybe you could ask the mods to change the title of the thread to Help finding fault with Playmaster Sub AMP. Might get more (of the right) people reading it.
Just my opinon. Which is why I said maybe you should get a second one I just personally wouldn't be forking out $100+ unless I was 100% sure that they weren't going to blow again!
I have a playmaster series 200 amp (100W/channel intergrated amp 1986 vintage). It doesn't actually have a fuse before the power supply (which Is probably bad), but it has four fuses in the amp itself, one each between +ve and -ve rails and mosfets in each channel. The docco with the kit says that they are "to protect against catastrophic device failure"
see circuit diagram here http://www.diyaudio.com/forums/showthread.php?postid=228803#post228803
I've always assumed that meant protect the mosfets, but maybe it means protect the rest of the amp! especially since there are no fuses anywhere else, probably something I should do something about!
The RLC network I mentioned earlier is the coil, resistor and capacitor on the speaker output. Apparently the caps on my amp were prone to failing if you didn't use the right ones.
Tony.
edit: I posted in the modeating thread in the everything else forum asking the mods if that can tack (help needed finding fault) on the end of your subject. Hope you don't mind.
I just personally wouldn't be forking out $100+ unless I was 100% sure that they weren't going to blow again!I have a playmaster series 200 amp (100W/channel intergrated amp 1986 vintage). It doesn't actually have a fuse before the power supply (which Is probably bad), but it has four fuses in the amp itself, one each between +ve and -ve rails and mosfets in each channel. The docco with the kit says that they are "to protect against catastrophic device failure"
see circuit diagram here http://www.diyaudio.com/forums/showthread.php?postid=228803#post228803
I've always assumed that meant protect the mosfets, but maybe it means protect the rest of the amp! especially since there are no fuses anywhere else, probably something I should do something about!
The RLC network I mentioned earlier is the coil, resistor and capacitor on the speaker output. Apparently the caps on my amp were prone to failing if you didn't use the right ones.
Tony.
edit: I posted in the modeating thread in the everything else forum asking the mods if that can tack (help needed finding fault) on the end of your subject. Hope you don't mind.
I'd love to get a second opinion but it seems I'm not worthy
On this Amp there isn't an RCL network, well kinda. It does have a resistor and cap but no coil. These parts test ok anyway.
I don't mind if the title is changed at all. It prolly would have been a smart idea to put that there in the first place.
On this Amp there isn't an RCL network, well kinda. It does have a resistor and cap but no coil. These parts test ok anyway.
I don't mind if the title is changed at all. It prolly would have been a smart idea to put that there in the first place.
I hate fixing this kind of fault
If I had to, here's how I'd do it:
If the output stage has many parallelled devices, just fit one pair*, and new drivers.
Check, with a meter, all small resistors in the output and driver stages (even if they look perfect).
Disconnect the load (speakers) and connect a high resistance load (1K resistor or so).
Use a Variac to gradually wind up the mains voltage, and see that the centre voltage stabilises.
Once it works well in this mode, leave it running a few hours before fitting more output devices.
Check into 1K load first as well, before connecting speakers.
Make sure there is no possible short circuit on the speaker wiing.
*If it's a BTL (Bridge Tied Load) design, you'll need to fit 2 in each side.
If I had to, here's how I'd do it:
If the output stage has many parallelled devices, just fit one pair*, and new drivers.
Check, with a meter, all small resistors in the output and driver stages (even if they look perfect).
Disconnect the load (speakers) and connect a high resistance load (1K resistor or so).
Use a Variac to gradually wind up the mains voltage, and see that the centre voltage stabilises.
Once it works well in this mode, leave it running a few hours before fitting more output devices.
Check into 1K load first as well, before connecting speakers.
Make sure there is no possible short circuit on the speaker wiing.
*If it's a BTL (Bridge Tied Load) design, you'll need to fit 2 in each side.
I have removed and checked all resistors in this kit. I have checked all wiring, especially on the output side. The fuse still blows with the volume down and no speaker attached - no load or input (this was when the FETs where in) Unfortunately I don't have a Variac. Thanks for the suggestions. Here is the schematic if it helps.
Liam.
Liam.
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