Audio Altec Lansing MX 5021 Modding
- Thread starter cranky
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Re: MX5021 modding
Got it
Any siggestions on fixing the damamged holes?
Out of the 3 holes, One hole is totally gone. 2 more well, little bit of trace is left, can manage to fix it...only option now is wires?
Greenie, I'll be putting 8pin bases as well. I have a hunch I'll blow the opamps with my soldering gun, hence the bases.
Got it
Any siggestions on fixing the damamged holes?
Out of the 3 holes, One hole is totally gone. 2 more well, little bit of trace is left, can manage to fix it...only option now is wires?
Greenie, I'll be putting 8pin bases as well. I have a hunch I'll blow the opamps with my soldering gun, hence the bases.
Re: MX5021 modding
@ gannu. Check my first post in the thread, I have a suggested caps there itself. The thread continues with people offering what types are available in their local market. I prefer running the speakers in first so I get a good hang of the original sound, rather than dive into modding straight away.
I use a mix of Panasonic FC, locally available met/poly caps, and two Vishay MKP16 caps. FC and Vishay are not locally available, and no caps available locally work for this.
For Sunny's mods, I sent him all the caps from my excess lots, and he got the opamps locally.
Greenie: Good call on the sockets, except that the ones in the local market add too much stray impedance to be of any use. The leaf type sockets aren't as good as machined sockets which a) cost a bomb, more than most opamps and b) are difficult to find in the country.
Sunny. Use wire to the nearest contact point. It'll look messy but work fine.
@ gannu. Check my first post in the thread, I have a suggested caps there itself. The thread continues with people offering what types are available in their local market. I prefer running the speakers in first so I get a good hang of the original sound, rather than dive into modding straight away.
I use a mix of Panasonic FC, locally available met/poly caps, and two Vishay MKP16 caps. FC and Vishay are not locally available, and no caps available locally work for this.
For Sunny's mods, I sent him all the caps from my excess lots, and he got the opamps locally.
Greenie: Good call on the sockets, except that the ones in the local market add too much stray impedance to be of any use. The leaf type sockets aren't as good as machined sockets which a) cost a bomb, more than most opamps and b) are difficult to find in the country.
Sunny. Use wire to the nearest contact point. It'll look messy but work fine.
Re: MX5021 modding
When i enquired about MX in chennai, i got the quote as 7K :S . chennai guys where we can get MX at good price.
@sangaram: so the cross overs are of poor quality in the latest MX. I know a shop in ritchie street they provide diy kit and projects for engg students. Last year when i enquired about 2 way cross over they quote me Rs180. The coil is really huge with big capacitor. can we replace that.
When i enquired about MX in chennai, i got the quote as 7K :S . chennai guys where we can get MX at good price.
@sangaram: so the cross overs are of poor quality in the latest MX. I know a shop in ritchie street they provide diy kit and projects for engg students. Last year when i enquired about 2 way cross over they quote me Rs180. The coil is really huge with big capacitor. can we replace that.
greenhorn
Patron
Re: MX5021 modding
those are the bolton/dainty ones. They're for crossing over a tweeter and a (usually) midbass/woofer
the cutoff frequency will be different to what the MX needs. best route would be to replace the capacitor of the MX's crossover with a better one of the same value, and a good poly cap in parallel with it.
The inductor , maybe you can put in an air core one instead if it uses a ferrite one
question. what sort of PSU is it using ? is the amp section also regulated ? else putting in a regulated outboard PSU might help things ( a bit expensive though)
vijaycool said:
those are the bolton/dainty ones. They're for crossing over a tweeter and a (usually) midbass/woofer
the cutoff frequency will be different to what the MX needs. best route would be to replace the capacitor of the MX's crossover with a better one of the same value, and a good poly cap in parallel with it.
The inductor , maybe you can put in an air core one instead if it uses a ferrite one
question. what sort of PSU is it using ? is the amp section also regulated ? else putting in a regulated outboard PSU might help things ( a bit expensive though
)Re: MX5021 modding
You can't fit any crossover in any speaker and hope it'll work. It has to match the frequency and impedance of the drivers in use. The aftermarket crossovers are at best a stopgap arrangement, and cannot be used in this application.
Anyone have CorelDraw? I have a .cdr file I can send around (I don't own a license for the software anymore) with the original crossover schematic.
The MX already has the required capacitors for bypassing. These need not be replaced, they use ceramic SMD caps on the copper side, nearly as good implementation as any.
The PSU is the standard unregulated linear PSU. Regulated PSUs in power amps are generally not my cup of tea. They can provide excellent performance but for that they need to be very well-built and specced, upto 3x the power output of the power amp. Only recommended for the highest specification or if you have a very noisy power supply (mains) where you live. For the most part, an unregulated PS will provide more dynamic headroom than a regulated counterpart.
You can't fit any crossover in any speaker and hope it'll work. It has to match the frequency and impedance of the drivers in use. The aftermarket crossovers are at best a stopgap arrangement, and cannot be used in this application.
Anyone have CorelDraw? I have a .cdr file I can send around (I don't own a license for the software anymore) with the original crossover schematic.
The MX already has the required capacitors for bypassing. These need not be replaced, they use ceramic SMD caps on the copper side, nearly as good implementation as any.
The PSU is the standard unregulated linear PSU. Regulated PSUs in power amps are generally not my cup of tea. They can provide excellent performance but for that they need to be very well-built and specced, upto 3x the power output of the power amp. Only recommended for the highest specification or if you have a very noisy power supply (mains) where you live. For the most part, an unregulated PS will provide more dynamic headroom than a regulated counterpart.
greenhorn
Patron
Re: MX5021 modding
well, i had the idea of putting one in a PC speaker since they are lesser power then a typical power amp. I remember reading somewhere that Regulated PSU's give more controlled bass with better slam. Cant get toroidals here, and the transformers i get here have poor regulation
well, i had the idea of putting one in a PC speaker since they are lesser power then a typical power amp. I remember reading somewhere that Regulated PSU's give more controlled bass with better slam. Cant get toroidals here, and the transformers i get here have poor regulation
Re: MX5021 modding
The poor regulation of transformers is usually solved by over-speccing the transformer. If you cannot get custom transformers where you live (hard to believe), you can usually buy a transformer with 30% more rating than you need (current, not voltage), and loading the secondary. Wasteful, but easier to implement than regulators.
The poor regulation of transformers is usually solved by over-speccing the transformer. If you cannot get custom transformers where you live (hard to believe), you can usually buy a transformer with 30% more rating than you need (current, not voltage), and loading the secondary. Wasteful, but easier to implement than regulators.
Re: MX5021 modding
I dont want to put up a new thread for this silly question.
In my school and college days my friend made a custom amplifier with STK chip. The thump is floor shattering and cymbals are too crisp and clear. But why STK's are not much used now a days. He told me even the slightest voltage fluctuation will kill the chip. Are there any available replacement for STK's.
I dont want to put up a new thread for this silly question.
In my school and college days my friend made a custom amplifier with STK chip. The thump is floor shattering and cymbals are too crisp and clear. But why STK's are not much used now a days. He told me even the slightest voltage fluctuation will kill the chip. Are there any available replacement for STK's.
greenhorn
Patron
Re: MX5021 modding
nah, my trusty old panasonic Hi Fi uses an STK 435 (check rig gallery for pics) It's seen everything from 70 to 260 volts thanks to a stepup and varying voltages. But It's better you get a mosfet based AMP , which are better and cheaper these days
nah, my trusty old panasonic Hi Fi uses an STK 435 (check rig gallery for pics) It's seen everything from 70 to 260 volts thanks to a stepup and varying voltages. But It's better you get a mosfet based AMP , which are better and cheaper these days
Re: MX5021 modding
Been a long time since i posted here.
Sangram, Looks like I took out pin 2 of one opamp (inverting input A ). Just one lead gone, and I cant seem to trace it
Will solder 4 of 5 opamps today. will leave one for your opinion before trying soemthing on my own
Been a long time since i posted here.
Sangram, Looks like I took out pin 2 of one opamp (inverting input A ). Just one lead gone, and I cant seem to trace it
Will solder 4 of 5 opamps today. will leave one for your opinion before trying soemthing on my own
Re: MX5021 modding
Don't panic.
Patch the signal input (should be the negative lead of one of the input caps) straight to the control chip, it should work fine. You can pull the input signal off the input jack, just use a cap so any DC will be blocked.
The chip is the TDA 7433, and the pin to which the output is routed is Pin 2 and pin 5. It's a surface-mounted chip on the back of the board.
Static is usually a sign that one of the opamps is mounted in reverse. That usually kills it.
You have to go over the circuit very carefully. IIRC the opamps were not super-critical to correct operation, and can bypassed through to the control chip.
Which opamps did you change?
Don't panic.
Patch the signal input (should be the negative lead of one of the input caps) straight to the control chip, it should work fine. You can pull the input signal off the input jack, just use a cap so any DC will be blocked.
The chip is the TDA 7433, and the pin to which the output is routed is Pin 2 and pin 5. It's a surface-mounted chip on the back of the board.
Static is usually a sign that one of the opamps is mounted in reverse. That usually kills it.
You have to go over the circuit very carefully. IIRC the opamps were not super-critical to correct operation, and can bypassed through to the control chip.
Which opamps did you change?
Re: MX5021 modding
For some very strange reason this thread does not show up in my new post search.
In any case, I'll wait for your pictures. Do mark out which pin/trace is missing.
If you leave the negative input open, the amp will operate in open loop mode, which for the 5532 is a gain of ~1000. The only output will be white noise., and all stages after it will only output exactly the same thing.
Again, IIRC all opamps faced one direction. It's a pity I don't have the speakers anymore, else I could've walked you through the troubleshooting.
For some very strange reason this thread does not show up in my new post search.
In any case, I'll wait for your pictures. Do mark out which pin/trace is missing.
If you leave the negative input open, the amp will operate in open loop mode, which for the 5532 is a gain of ~1000. The only output will be white noise., and all stages after it will only output exactly the same thing.
Again, IIRC all opamps faced one direction. It's a pity I don't have the speakers anymore, else I could've walked you through the troubleshooting.
Re: MX5021 modding
It connects to R92, actually. One side of R92 is connected to the output pin, the other needs to go to the negative input (pin 2).
However, you should not be getting white noise on all three channels, that is a sign of some other issue. This defect can only cause white noise on one channel.
You could have bypassed the opamp, but it looks like the next opamp has not been installed. So that's not an option right now.
On the affected opamp, pin 5 needs to connect to R95. That joint looks suspect and I would do it again.
Lastly, looks like you have quite a few dry joints. Use a hot iron and redo them - just apply flux with a brush and touch a hot iron for 5 seconds (count 'em) to reflow the solder on all joints you did. Don't use any more solder.
It connects to R92, actually. One side of R92 is connected to the output pin, the other needs to go to the negative input (pin 2).
However, you should not be getting white noise on all three channels, that is a sign of some other issue. This defect can only cause white noise on one channel.
You could have bypassed the opamp, but it looks like the next opamp has not been installed. So that's not an option right now.
On the affected opamp, pin 5 needs to connect to R95. That joint looks suspect and I would do it again.
Lastly, looks like you have quite a few dry joints. Use a hot iron and redo them - just apply flux with a brush and touch a hot iron for 5 seconds (count 'em) to reflow the solder on all joints you did. Don't use any more solder.
Re: MX5021 modding
Will do
The noise existed only with 4 opamps. As soon as I soldered the 5th opamp, there was no noise. First thoughts could hear the sub booming a bit ( hadnt closed the connections) then connected right speaker, could hear sound
The R95 trace is fine...it has lifted up from the PCB, but the connection is intact. Only bother was the Pin 2 on the opamp. SO I should solder it to R92? Precisely which side of R92?
Can you just point out which pins need
EDIT : Never mind, I got it. Its funny how high res pics tell a tale that naked eyes cant see
Will do
The noise existed only with 4 opamps. As soon as I soldered the 5th opamp, there was no noise. First thoughts could hear the sub booming a bit ( hadnt closed the connections) then connected right speaker, could hear sound
The R95 trace is fine...it has lifted up from the PCB, but the connection is intact. Only bother was the Pin 2 on the opamp. SO I should solder it to R92? Precisely which side of R92?
Can you just point out which pins need
EDIT : Never mind, I got it. Its funny how high res pics tell a tale that naked eyes cant see