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zebble
Topic Author
Posts: 8
Joined: Tue Dec 05, 2006 6:48 pm

Speaker Amplifiers replacement and new power supply success!

Wed Nov 07, 2012 12:15 pm

Just thought I'd share that I was able to successfully replace the power supply using a universal notebook power supply @ 16V, along with the helpful instructions to build a 9.8V regulator circuit from http://freepdfhosting.com/9333705bcb.pdf

However, after replacing the power supply I was getting a LOT of noise coming from all 3 speakers (left, right, subwoofer). Things got better for a bit when they got up to temperature, but have progressively gotten worse since then.

So, I started searching for a way to replace the amplifiers for each speaker. After ripping out the subwoofer amp, and finding that it was based on an obsolete TI TPA3001D1 D-class 20W amp chip, I had a place to start looking for similar specs.

Digging further, I found that Maxim had alternative amplifiers, specifically the MAX9703 and MAX9704 http://www.maximintegrated.com/alternatives.cfm/part/TPA3001/pk/458.

Further searching, and found some dirt-cheap module-ized versions of the MAX9703 and MAX9704 sold through http://www.dx.com. These use the VMA2015 which is a simplified version of the MAX9703/9704.

DealExtreme also had pre-made boards with two of these chips on them, again for dirt-cheap http://dx.com/p/vma2015-15w-stereo-audio-amplifier-evaluation-module-evm-board-44125?item=2.

Ordered 4 of them the 2 R1000's I have, and just installed them, and everything sounds great! I have some re-assembly/cleanup/tuning to still do, but the whole setup has been running perfectly for a couple hours! Sounds better than I remember, but that could just be a "want" to hear things better after all my hard work. :o

If anyone is interested in a how-to, I can fully document things when I do the second one. Just let me know...
 
FrankB
Posts: 277
Joined: Mon Sep 19, 2005 8:16 am

Re: Speaker Amplifiers replacement and new power supply succ

Thu Nov 08, 2012 6:40 am

I would be interested in how you did it. They are two channel amps? So you used one for the front two speakers and one for the subwoofer in each R1000? How did you handle the control signals?

thanks,
Frank

PS: Matt Burkhard (burkhardi@hotmail.com) has exact replacement modules available.
 
zebble
Topic Author
Posts: 8
Joined: Tue Dec 05, 2006 6:48 pm

Re: Speaker Amplifiers replacement and new power supply succ

Thu Nov 08, 2012 10:58 am

Hi FrankB,

Yes, they are 2-channel amps. I used 2 of these boards, and used only one side for the subwoofer. They have a single-channel version of the same board available for $4 less, but I figured I'd get the dual-channels instead, just in case this mod didn't work and could then use the board elsewhere as a stereo amp. Now that I know things work, I'd probably go with the single channel for the subwoofer.

I used the TTL compatible control signal on the blue wire, and connected directly to the "EN" pin on the amplifer board. Works like a champ. Amps go silent when told to, and turn on when needed.

Found that I'll likely need to build a simple crossover for the subwoofer, as this is a full-range amp. I assume the old amps had a configurable crossover. Any ideas on a simple crossover I could fit into the subwoofer enclosure?

Was thinking about getting the replacement amp modules from Matt Burkhard, but I also figured they'd eventually fail again anyway, so looked for a permanent fix alternative. TI discontinued the TPA3001 on the original boards, so they must have discontinued them for a reason. ;)
 
FrankB
Posts: 277
Joined: Mon Sep 19, 2005 8:16 am

Re: Speaker Amplifiers replacement and new power supply succ

Fri Nov 09, 2012 7:25 am

zebble wrote:
I used the TTL compatible control signal on the blue wire, and connected directly to the "EN" pin on the amplifer board. Works like a champ. Amps go silent when told to, and turn on when needed.


Good to know. I was concerned about the audio disable signal but now that I think about it, it's off by default and must be asserted by the amp, so disconnecting the amp asserting the signal allows the rest of the system to work.

zebble wrote:
Found that I'll likely need to build a simple crossover for the subwoofer, as this is a full-range amp. I assume the old amps had a configurable crossover. Any ideas on a simple crossover I could fit into the subwoofer enclosure?


I have not had the sub-woofer disassembled, only the front speakers. Did the old amp board have a cross over?

Frank
 
DJans
Posts: 122
Joined: Tue Jun 20, 2006 7:06 am
Location: Germany

Re: Speaker Amplifiers replacement and new power supply succ

Sat Nov 10, 2012 1:50 am

zebble wrote:
If anyone is interested in a how-to, I can fully document things when I do the second one. Just let me know...


Zebble, great work and very interesting. :D Im am interested in a more detailed ducumentation, please.

Thanks!
 
Limeybrit
Posts: 15
Joined: Sun Mar 06, 2005 7:03 pm
Location: A mostly harmless planet

Re: Speaker Amplifiers replacement and new power supply succ

Sat Feb 01, 2014 3:46 pm

I've an R1000 with a dead front-right speaker & noisy woofer for which I'd like to try the amplifier board replacement suggested, but I can't work out the wiring config used for the connectors - does anyone here know?

zebble stated that the blue wire was to control muting and 3 connections must be for GND/+12v/audio signal, but what are the other 2 wires on the 6-pin connectors used for?

(Apologies for resurrecting a thread from 2012, but it seemed more sensible than duplicating the existing info in a new thread.)
 
chuck2
Posts: 2
Joined: Thu Mar 06, 2014 4:49 pm

Re: Speaker Amplifiers replacement and new power supply succ

Thu Mar 06, 2014 5:02 pm

I decided to bring back to life my 2 R1000, both of which quit just after the warranty expired. I have replaced the PS but need to replace the three speaker amps. However I cannot determine the signals on the 6 pin connectors. Using a DVM, I have determined which pins are 19V and GND but cannot determine the signal on the other pins. Can anyone help? Thanks. :?:
 
Limeybrit
Posts: 15
Joined: Sun Mar 06, 2005 7:03 pm
Location: A mostly harmless planet

Re: Speaker Amplifiers replacement and new power supply succ

Fri Mar 07, 2014 6:41 pm

chuck2 wrote:
I decided to bring back to life my 2 R1000, both of which quit just after the warranty expired. I have replaced the PS but need to replace the three speaker amps. However I cannot determine the signals on the 6 pin connectors. Using a DVM, I have determined which pins are 19V and GND but cannot determine the signal on the other pins. Can anyone help? Thanks. :?:


Are you sure all 3 amps are bad (ie: either dead, or noisy)? Sometimes an amp baord failure invokes muting on all three channels (see http://forums.roku.com/viewtopic.php?f=16&t=31008&p=299775&hilit=amp#p263702).

Can't help with the wiring, as I haven't figured it out myself yet & the OP doesn't appear to be active on this topic anymore.
 
chuck2
Posts: 2
Joined: Thu Mar 06, 2014 4:49 pm

Re: Speaker Amplifiers replacement and new power supply succ

Sat Mar 08, 2014 9:05 am

All speakers are noisy and crackling. Short of having a scope it appears these devices are headed for the trash . I have requested a schematic from ROKU.
 
DJans
Posts: 122
Joined: Tue Jun 20, 2006 7:06 am
Location: Germany

Re: Speaker Amplifiers replacement and new power supply succ

Sun Mar 23, 2014 2:17 am

You wrote "I decided to bring back to life my 2 R1000", so you have 2 R1000. Remove the front speaker modules of both units and test them module by module to check which modules are working. Often one faulty module generates a crackling sound or muting on all channels.

If you have dismounted the small amplifier boards, you will see that there is some kind of yellow glue on the side where the cables are soldered and on the side the small single wire is soldered. The problem is that this kind of glue becomes electrically conductive over the time. The result is crackling sound, muting on all channels or a low amp output volume.
Take a toothpicker and remove carefully all of the yellowish glue from the amp boards and your radio will be back to life.

Regards
Dirk
 
Limeybrit
Posts: 15
Joined: Sun Mar 06, 2005 7:03 pm
Location: A mostly harmless planet

Re: Speaker Amplifiers replacement and new power supply succ

Wed May 21, 2014 6:10 pm

After poking around with a multimeter/connectivity tester, I've concluded what the pinout assignments appear to be - with the front part of the R1000 opened & observing the connector pinouts for the Right, Sub & Left channels from the rear:

Top
------------------------------------------------------------
  R  S  L     Color       Purpose
  1  1  1     Black       Audio
 --2--2--2     Brown       Gnd
| 3--3--3     Red         ? Standby perhaps (reads 1.8v powered)
| 4--4--4     Blue        Mute
 --5--5--5     White       Gnd
  6--6--6     Yellow      +12v (+19v on original power supply)
------------------------------------------------------------
Bottom


On rows 2-6, the pins on each connector are common across each of the rows, with the Gnd on rows 2 & 5 also being common to each other.
Since I'm using a 12v supply for both the original 19v & 9.5v supply rails, the yellow wire is +12v, meaning I can run 12v amp boards off it too.

Since I have 3 bad channels over 2 units (2 front lefts & one sub), I tried hooking up a really cheap 15w amp board to one of the front speakers (~$4 from http://www.dx.com/p/jtron-tda7297-dual-channel-15w-15w-amplifier-board-green-dc-12v-266124 ) and did get audio out of the speaker, but with a lot of distortion on the base frequencies - swapping the front speakers connectors around also swaps the distortion, so either the speaker itself is bad, or perhaps the speaker is being overdriven by the lack of a crossover circuit, or this particular amp just isn't up to the job.

I may now need to try a bass filter of some sort, or one of the originally suggested vma2015 boards (though these are now $20 each, which adds up when you need 3 of 'em). {Or see if Burkhardi still has some spares, but I learn more this way.)

As ever, the above is merely what I found with my units - I take no responsibility if you use the info here & immediately burst into flames or whatnot...

ps: @DJans, I did wonder if the gloop over the solder points had gone conductive & since wanted to see if anything useful was written on the PCB underneath, I carefully scraped 99% of it off - in my case, this didn't help, but that's not intended to invalidate your observation.
 
DJans
Posts: 122
Joined: Tue Jun 20, 2006 7:06 am
Location: Germany

Re: Speaker Amplifiers replacement and new power supply succ

Tue May 27, 2014 4:06 am

I have fixed a lot of Radios over the time and the main problem was this kind of glue that became conductive. After removing it a lot of the amplifier modules work.
I also tried to connect several amplifier modules I had (DIY kits or whatever) to the internal ROKU connector but I did always get a distorted sound.

The worst unit I used had a faded display and a really worn housing but 2 good amp modules that I removed to fix other units. In this worn unit I used the headphone connector to get a signal for a 2 x 10 W stereo amplifier module that I had as an old DIY kit. The unit is good enough for my home working shed and works without subwoofer, but it sounds really OK.

If somebody really did a succesful replacement of the ROKU amplifier modules by 3rd party modules some details would be great how to connect using the internal ROKU connectors.

Regards
Dirk
 
Limeybrit
Posts: 15
Joined: Sun Mar 06, 2005 7:03 pm
Location: A mostly harmless planet

Re: Speaker Amplifiers replacement and new power supply succ

Tue May 27, 2014 11:21 am

DJans wrote:
I also tried to connect several amplifier modules I had (DIY kits or whatever) to the internal ROKU connector but I did always get a distorted sound.


Hi Dirk,

Were these all replacing satellite (L/R channel) amps, or for the Subwoofer too? Zebble's original report of success was for the Sub, so I'm wondering if this the only one that can take the full frequency range without distortion? When I get a spare half-hour, I'll crack open the R1000 back section I have with a suspected bad Sub amp & see if the replacement amp distorts there also.

~Limeybrit~
 
ntpntpntp
Posts: 4
Joined: Tue May 22, 2012 11:31 am

Re: Speaker Amplifiers replacement and new power supply succ

Fri May 30, 2014 6:09 am

Keep us posted on your progress please?

I've just sorted out the power supply on my SBRadio using a 14V brick plus a regulator board from ebay. I've cleaned off a lot of the brown gunk from the three amp boards, but the sub-woofer amp is really securely stuck to the case with a big gloop of hard yellow stuff, I haven't managed to release it and clean this all off for fear of damaging something. I'm getting some hiss and crackling at first power up, though it seems to die away after a while. I've had the box running all afternoon at 75% volume and its been fine.

Just in case I need to replace the amps I've ordered a couple of vma2015 boards from dx.com

Nick (in the UK)
 
Limeybrit
Posts: 15
Joined: Sun Mar 06, 2005 7:03 pm
Location: A mostly harmless planet

Re: Speaker Amplifiers replacement and new power supply succ

Fri May 30, 2014 11:06 am

ntpntpntp wrote:
Keep us posted on your progress please?

I've just sorted out the power supply on my SBRadio using a 14V brick plus a regulator board from ebay. I've cleaned off a lot of the brown gunk from the three amp boards, but the sub-woofer amp is really securely stuck to the case with a big gloop of hard yellow stuff, I haven't managed to release it and clean this all off for fear of damaging something. I'm getting some hiss and crackling, though this sometimes dies away after a while.

Can't seem to find the vma2015 modules easily available in the UK, but there are plenty of other class D amp boards in ebay around the 20W mark which might be worth a try I guess? Not sure if any of these have an Enable pin which seems to be a requirement according to the previous posts?
<edit>have ordered a couple of vma2015 boards from dx</edit>


Well, yesterday I replaced the Sub amp board with another of the el-cheapo amps I had - works, but still no cigar - I still get distortion on this, although it is less than that for the Satellite I did earlier. Again, swapping the L/S/R channel connectors around also swaps the distortion, so I know that the input signal is otherwise OK. Seems like both replacement amps are being overdriven in some way & maybe need attenuation. I also found that the distortion lessened after leaving the radio running for a while, but not by enough to be satisfactory. I might try hooking an amp board up to the earphone jack (as DJans did) just to verify that the replacement amp boards work there, but I really would like to use the proper setup.

Since the mute/enable pins are common across the 3 channels, I found that you don't need to worry about this on the replacement amps, provided that you have at least one working original amp board (or 1 replacement that does assert the signal) hooked up. I've replaced 2 bad amps with amps that don't have the blue mute/enable wire connected on my radio & the 1 remaining original amp asserts the mute/enable signal. I did notice a slight pop on power-up, so I suspect that the Red wire is indeed a Standby signal, as its not connected to the replacement amps either.

DX is the only english language site where I've seen the vma2015 boards for sale, but their shipping times have become pretty atrocious recently - my most recent order from them took > 8 weeks to arrive. Since Zebble indicated that he was able to hook one of these up without distortion, I may yet have to try one. One of the other class-D boards you see on ebay and the like may be worth a punt, but you do need to consider the physical dimensions because of the tight spaces they'll have to go into (esp. for the satellites) - a lot of the boards I looked at just wouldn't fit.

Regarding removal of the existing amp boards - I'd leave them in place until you know that the replacement board works, or unless they're already dead. The gloop used for the satellite board I replaced had become brittle so I was able to carefully chip it away with a jewelers screwdriver until I could coax it out. The one in the sub turned out to be much harder since there was more gloop & the plastic supports pressing against the board were more extensive - in the end I used a Dremel drill to cut away enough of both the plastic supports & the gloop around them, to be able to pull out the board. This is quite tricky to do without damaging the board, or accidentally drilling through the case, so go slowly & carefully.

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