Modding the Altec Lansing MX 5021 for dummies!!

INTRODUCTION

The Altec Lansing MX 5021 speakers have been here for a while. Tauted to be one of the best speakers in the 2.1 genus second only to the legendary Klipsch Promedia 2.1, the Altec still packs a punch when it comes to performance. Audiophile grade music and one need not...

Can someone good with soldering in pune help me with modding mine . Volume cracks when i go over 3 dots

Hi to all modders,

I badly need your help… I have ruined my MX5021… i have scratched the PCB on the OPAMP at PIN #7 at U6… PLS CHECK LINK BELOW TO SEE PICS. cos im not an electronics geek... i use poor seoldering eqpt...



HERE IS THE OPAMP DIAGRAM: im not sure if PIN # 6 and 7 are connected at U6…. PLS GIVE ME A A GUIDE.. ELECTRONICS ISNT MY FIELD and i have a bad soldering iron that ruined this whole mod…



i dont know where it is connected. thats why i need your help or anyone who could give me a close photo of the circuit at the back of U6 would gladly appreciate that.. really need your help… the TDA7265 burnt and the technician where i sent my mx5021 said it was definitely shorted coz the fuse on the transformer also gets busted.. really had a hard time replacing the fuse since too little space inside and the transformer was somewhat like glued… now it is running again but the woofer is not doing well it was somehow bypassed by a jumper and the ST074C was suspected to be also burnt.. so i ordered a replacement but the available is TL074C.. would that be okay?



HERE’S THE PHOTO AT THE BACK WITH DETAILS AND MY QUESTION…

SEE LINK BELOW:

Pin #6 and #7 were not interconnected! Had that been the case they will not have routed the PCB tracing for #6 that way. De-solder the link between the two pins.

It appears that pin #7 has lost its trace on the PCB - solder a wire to pin #7 (this's going to be very hard! Esp. without making a contact with the adjacent pins so see if you can provide some sort of insulation like a small heatshrink) and the other end of the wire to a scratched part on the huge tracing. i.e anywhere on the green large area. Scratch the area, apply the solder in advance and solder the other end of the wire from pin #7 here.

Good luck!

hey thanks for the prompt reply...



do u mean (large green area) the circuit trace below that pin#7???? i will scratch it and make jumper to pin #7... did i get it right? i will find heatsrijnk so they wont get shorted again... could you edit the photo and mark where? coz im really not a geek with this stuff... thanks alot.. really apreciate your help..

Pin #7 is definitely not going to connect to the large green area, which is the ground plane. Pin #7 is the output of opamp and connecting it to GND will short circuit the opamp. Though the opamp is unlikely to burn, it most likely has short circuit protection, this is definitely not correct.

Please wait till someone can actually verify what the exact connection is. I will try to post it today.

Very well, from the photo he's posted and another photo it did seem to me that way or at least to me!

thanks gannu for that quick reply.. it really helped me.. i already made a jumper to the big copper trce without shorting other pins... but still my woofer isnt functioning... the sat works perfectly... the technician also suspected my 074C is defective.. he manage to bypass it but the woofer sounds pretty bad and awful... we have locally available TL 074CN a DIP type 14-pin quad opamp... can this be used as a substitute for that.. i mean they have different bend on the PINS.... the 074C installed on the PCB is SO type... while the replace is straight DIP type...

TL074 is fine, the one you are getting locally. You need an adapter for surface mount.

For USA buyers this is what you need: Digi-Key - 296-7199-5-ND (Manufacturer - TL074ID)

cranky, could you please pour your thoughts on his previous query? i.e does pin #7 connect to that large green trace on the board.

Raghu is correct. The pin is not a ground pin, it is a live trace. I have no clue where it is supposed to connect - the pics are simply not large or clear enough for me to see the original. If I knew, I would have replied. I don't. And I don't even have a piece with me to see (it's been five years since I had the MX, guys - I don't remember everything ).

Sorry.

@rayfloyd: Could you post a close-up shot of the pins of the IC in question?

Remove the connection ASAP. Thanks cranky for the confirmation.

Pin #7 connecting to Pin #6 is one of the most common configurations for an opamp - unity gain buffer. Its very likely that they are indeed connected. Im not having enough time to open up my MX5021. I would suggest you wait for me/someone to confirm the connections. I dont think any other component is blown, unless you had issues before this happened.

^Raghu was right. Dug this pic from one of my archives, zoomed it and took a screenshot.



There seems to be a connection between pin nos. 6 & 7 but not the GND. The rounded trace near pin no. 7 was pretty confusing!

Sincere apologies there!

anyway, thanks Gannu for that. i will remove them asap... but another question... what could possibly get wrong when my woofer wont sound at all? does 074C contribute to that coz the technician where i sent my mx5021 thought that is the culprit...




FOR THOSE WHO HAVE STOCK MX5021 BOARD, CAN YOU VERIFY IF PIN#7 and 6 and INDEED CONNECTED?




I HAVE 2nd THOUGHTS ABOUT IT SINCE THE OPAMP AT U12 HAS PIN#6 and 7 CONNECTED...