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-   -   75+ watts the easy way, JBL retrofit (http://www.diyaudio.com/forums/subwoofers/160908-75-watts-easy-way-jbl-retrofit.html)

Zero Cool 9th February 2010 02:00 AM

75+ watts the easy way, JBL retrofit
 
So I picked up a broken JBL PSW-D110 subwoofer the other day that was going to get tossed out. after a bit of googling i found these things use the AMI S53 S64 power modules that are problematic and as they are epoxied into an aluminum case, pretty hard to repair.

After looking at the specs a bit closer. the claimed 150 watts of the sub is really 75 watts RMS and the jbl driver is 4 ohms. 75 watts isn't really much and a LM 3886 will almost do that, and a pair should easily surpass it. the supply voltages are +/- 43V

But that got me thinking. Is there an easier way? what would be the least expensive option to produce at least 75 watts at 4 ohms? and preferably using the stock +/-43V rails???

I see that Apex Jr has some nice 150watt plate amps for $89 that the power section could be retro fitted from. but frankly if i am going to spend $100 with shipping, i might as well just buy another used sub that works.

I also saw a schematic in a JBL service manual for a switching amp using a pair of IRF 600 series mosfets and a IR2111 IC that looked pretty simple to build. so that got me thinking that maybe with 43V rails that maybe more power could be had with few parts? maybe 100 watts?? if the transformer has the current.

I have parts on hand. so if i can build a cheap option and save this sub from the scrap heap. cool. suggestions on the cheapest easiest power? I would be willing to spend up to say $40-50


Zc

jbell 9th February 2010 02:32 AM

NHT drivers and electronics surplus sale

Zero Cool 9th February 2010 03:10 AM

OOOOOOOOHhhh mmmmm Interesting! Thanks for that link. I may have to get one of those to play with.


Zc

Zero Cool 9th February 2010 05:21 PM

After looking over that Foster amp a bit closer I see that the amp section is just a conventional class AB amp that runs on 50V rails.

I don't want to try and retrofit an entire plate amp. but if i could remove the amp section from that Foster system and retrofit it onto the JBL plate with an added heatsink that would be ok. that is if that Foster amp will run on 43V rails? it would obviously make less power but that's ok.

I still keep wondering about a pair of LM3886 IC's on a heatsink. seems that 35-38V is about the max they like to run on. but the data sheets say they will run on much higher voltages. I wonder if they would run OK on 43V rails? Otherwise a couple mosfets and zeners and i bet i could step that voltage down and provide some regulation as well... more work but i have all the parts on hand....but we are still dealing with having to add a large heatsink. I still haven't found any sort of cheap Class-D type module.


Zc

powerflux 9th February 2010 05:56 PM

on 43v rails a P3A from esp would fit perfectly. also very cheap and simple..

http://sound.westhost.com/project3a.htm

i've built them with
3055/2955
mj15003/mj15004
2sa1943/2sc5200
mjl21193/mjl21194

as the power pairs

and a lot of different small signals for the bias/small signal part. you could even use MPSA43/92 for the small signals for the higher voltage :)

always worked flawless

sregor 10th February 2010 10:59 PM

As you were at apex jr., they also have a 220 volt 150 watt plate amp which people have been putting in their own transformers. He posts a link to one project and gives pinouts for all the connections. Also, for chips their is a TDA7293 which will run up to +-50 volts. There probably are STK modules around, but I'm not familiar with them.

Zero Cool 15th February 2010 12:29 AM

I managed to get the S53 amp module to work. Just re-soldered the module to the main PCB per the service manual, paying close attention to apply the heat to both the module tabs and the main PCB. that seems to have got it working again. if it dies im just going to chunk it and buy something else. it's just for the living room surround sound system.

amp_guy 15th February 2010 01:33 AM

I went through a similar experiance with a jbl psw1000, that I picked up to repair and re-sell which I have done and no longer have in my possesion.
I found that below about 60hz it could not deliver anywhere close to it's potential becuse of a woefully inadequate power supply. After nearly tripling the filter caps and replacing the transformer with the same voltage but about 2.25 times the current it finally didn't become severely modulated by ripple currents at lower freq's. Only to find it would no longer fit into the space alotted in the box. So after another mod this time to the box, the new owner is happy and Iam happy to be on to projects with more potential.
Lesson learned, mass market subs aremostly a waste of time.

Zero Cool 15th February 2010 04:02 PM

I am very dissapointed with the performance of the sub thats for sure. My Dell/Altec ADA995 computer sub with 2x 6.5" woofers actually out performs it mostly! LOL! that's sad! But maybe the Dell sub has some bass boost in it or something....


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