Luxman L-430 Recap / Overhaul

[Trevor White]

Hi Trevor,

The Rubycon Baby Blue elco is not CE-W type. I believe the parts code is TWSS, a General Purpose elco not specifically designed for audio. The CE W designation, I believe is CE for European electricity certification and W refer to temperature rating, which is 85 degree Celcius.

This elco quirks me since there are plenty of them in Luxman C-02 and M-02 I have.

I find your trial with CDE 383LX series to be very interesting as I plan to replace the main filter capacitor in M-02 (Nichicon 15000 uF 70V) but most available audio elco (Nichicon LKG, LNR, LNT) is too long, the only possible fit is 383LX.

Cheers,

Hi there mate,

Yes, I worked out some time ago that the "CE" was a standards mark

As for the big filter caps I also found that none of the modern Nichicons were of the correct physical size. The Cornell Dubilier's are close to an exact match, certainly in height. Also they have the additional mounting lugs that the Luxman circuit board supports. All in all an excellent alternative. So far the performance of the amp has been outstanding. Lot's more bottom end. I use the amp with the 'Tone Defeat' switch enabled all the time and it sounds great!

Cheers, and thanks for the comment.

 

[Stereopal]

Thank you for this post, this L430 rebuild is SUPER USEFUL for me. The Luxmas L430 was my first amplifier, and I have owned it for nearly 40 yrs. After reading all of this, I have decided to rebuild my unit.

I just ordered $ 125 dollars worth of capacitors on Digikey and will embark on this project asap !

Thank you !

 

[Trevor White]

Thank you for this post, this L430 rebuild is SUPER USEFUL for me. The Luxmas L430 was my first amplifier, and I have owned it for nearly 40 yrs. After reading all of this, I have decided to rebuild my unit.

I just ordered $ 125 dollars worth of capacitors on Digikey and will embark on this project asap !

Thank you !

My pleasure mate. I'm very pleased that someone else may benefit from this thread.

Proceed carefully and you should end up with an outstanding result, just as I have.

Cheers!

 

[Binkman]

@Trevor White You'll be pleased to know I've booked and linked the thread 3 times, one l-430 and two other lux models just for all the cap type references.
Cheers
bink

 

[Trevor White]

@Trevor White You'll be pleased to know I've booked and linked the thread 3 times, one l-430 and two other lux models just for all the cap type references.
Cheers
bink

That's great bink.

Great to see others benefiting from the info!

 

[Trevor White]

Hello again everyone,

Normally when listening to my system I use a pair of KEF Q900's. But recently I decided to overhaul my lovely old pair of WIGO Acustic 4 way's which I purchased in 1984. The WIGO's had a set of three volume controls on the back that allowed you to modify the volume of the three smaller drivers, Tweeter, Paper Cone Mid-Range and a Horn Tweeter/Mid-Range. Anyway the old trim pots were unusable and would generally not allow the smaller drivers to function at all, which is why I retired them. So I dismantled the speakers and removed all the drivers and pulled out the crossover. Checked all the components and then thoroughly cleaned the trim pots with some Deoxit D5. After reassembly I was thrilled to find that all the drivers were now working and the old WIGO's sounded great.

However, as the WIGO's have a large Woofer I noticed that the right hand speaker was showing somewhat more excursion that the left speaker when playing strong bass notes, especially on drums etc. At first I thought this was probably something wrong with the old speakers so I simply hooked up my KEF's and very carefully studied their cone excursion when playing the same tracks. To my amazement the KEF's displayed exactly the same behavior with the right speaker cones showing quite a bit more excursion than the left. I had never noticed this before.

This leads me to suspect that the Luxman L430 may actually be at fault, but before trying to investigate and find out what might be going on I thought I would ask here to see if anyone has a suggestion on what might be wrong?

So far I have tried playing the amp in 'Mono' mode, and with the Tone Direct switch both on and off. With the Tone Direct off and additional bass added via the tone control then the right speaker excursion is even greater! The system sounds fine, but I suspect that the frequencies being affected are low enough not to affect balance or anything. But something would appear to be not right.

Can any of you suggest where I should be looking in the amp? Could it be the main output transistors? It only seems to affect low frequencies as the Mid-Range and Treble sound fine and are well balanced left to right. How could I test for a problem like this?

Many Thanks,
Trevor

 

[Binkman]

G'day mate;
Check the dc offset (though no adjustment). check the Bias. sm says 60ma +/-1.0ma . may have drifted after burn in time.

 

[Trevor White]

G'day mate;
Check the dc offset (though no adjustment). check the Bias. sm says 60ma +/-1.0ma . may have drifted after burn in time.

Thanks Bink,

I'll check those settings first. DC offset was very good I think on this unit, although it is not directly adjustable. I spent some time on the Bias, but as you say perhaps it has drifted.
Would an uneven Bias setting impact the output in the way I have observed?

Cheers,
Trevor

 

[Binkman]

Would an uneven Bias setting impact the output in the way I have observed?

It could. I should think your massive rebuild with modern components your amp is running more efficient over orig. but drift is pretty common. It's also common for techs to have to cut back on bias after rebuilds.

 

[Trevor White]

Well, I spent a lot of time today going over the Lux, again!

The Bias settings were out of whack slightly at 41mA left channel and 49mA for the right. I reset these to 60mA plus or minus 10mA after 3 minutes from power on, as per spec. This did not make any difference to the amps performance.

Those of you that may have followed this thread from the beginning may recall that after completing the rebuild I did note that the amp seemed to have a lot more bottom end. Eventually I changed out the Elna Silmic II caps I had used and exchanged them for Nichicon UFG's. I also changed the big filter caps to Cornell Dubilier 15,000uf/80V items, which did seem to tone down the bass a bit.

In the end the amp still had noticeably more bottom end than original. I never really followed this up any further, just listening to the amp and enjoying it. But I have now determined that all that extra bass/bottom end seems to be concentrated mostly on the right channel. Interestingly the frequencies involved do not seem to affect the overall balance of the music (left to right balance that is). I had never bothered to closely watch the speaker cones, but now having done so I can clearly see that the right hand drivers and being 'driven' a lot harder at the bottom end. The rest of the audio spectrum seems fine, the amp sounds great and the left/right balance is well centered. It just seems to be at the very bottom end.

So here we go again I really need to try and track down just where in the amp this additional 'power' is being generated. I always run the amp with the 'Tone Direct' switch 'ON', so the tone control circuits are not in use. It must be something in the amplification section somewhere?

Can anyone offer a suggestion of just where I should look, or what kind of thing I should be looking for?

Many thanks in advance for any suggestions,
Trevor

 

[Binkman]

60mA plus or minus 10mA

Perhaps your input device is off balance? did you try other input devices?
bias I wouldn't exceed 60ma and try to get as close as possible. did you check dc offset?
How is right channel with tone direct off and tone controls @ neutral?

 

[Trevor White]

Perhaps your input device is off balance? did you try other input devices?
bias I wouldn't exceed 60ma and try to get as close as possible. did you check dc offset?
How is right channel with tone direct off and tone controls @ neutral?

Hi Bink,

Yeah, I tried multiple inputs, same result. I set the Bias to around 58mA, it varies slightly each time I measure it.

DC Offset was good, 13.0mV left channel and 1.9mV right channel.

I tried with the tone controls in and out of circuit. Same behavior in all cases. If I bump the bass control up when the tone controls are enabled then the right channel speaker excursion gets even more alarming!
I also tried swapping the speaker cables, in that case the extra bass appears on the left speakers.

I really need to try and identify just what might cause this sort of behavior. It must be something to do with the re-cap, but I just don't know where to look?

Cheers,
Trevor

 

[Binkman]

I also tried swapping the speaker cables, in that case the extra bass appears on the left speakers.

That's it ! Almost positive your amp is compensating for ohm's. Speaker excursion with that little bit of of Offset? NIL!
----
have read quite a few custom bundled threads and they get down to meat of ohm's load. Worn cables? If I'm right that puppy amp is quite responsive. could drive any quality speaker made in performance range. (IMO )

 

[Trevor White]

That's it ! Almost positive your amp is compensating for ohm's. Speaker excursion with that little bit of of Offset? NIL!
----
have read quite a few custom bundled threads and they get down to meat of ohm's load. Worn cables? If I'm right that puppy amp is quite responsive. could drive any quality speaker made in performance range. (IMO )

Hi Bink,

So, are you saying that the low offset of 1.9mV on the right channel is responsible for the apparent extra power??? Sorry but I can't quite follow the reasoning behind your comment?

All the cables are new and so are the KEF Q900's. The KEF's have a nominal load of 8 ohms, but in reality are probably more like 6. The WIGO's are old but the crossovers were in good condition The WIGO's are also 8 ohm but much less efficient than the KEF's.

I'm sure this amp did not display this behavior before I re-capped it, and now that I have noticed the unusual channel 'imbalance' I really want to try and find the culprit! I''m hoping someone with way more electronics experience than me can chime in with a suggestion of what might be causing this, or at least where I should be looking in the circuit.

Thanks for your responses,
Trevor

 

[Binkman]

But you said that when you swap cables left/right the speaker woofer 'excursion' moves to the left.. you would need hell of a lot more dc offset to affect that. I'm not 'chiming' in' but that cable swap is the most apparent 'clue' you have offered. okay try the old cables and see if a difference. Eliminate that and then tie into amp again.
--------worked your ass on that sucker so basics first, mate.

 

[Trevor White]

But you said that when you swap cables left/right the speaker woofer 'excursion' moves to the left.. you would need hell of a lot more dc offset to affect that. I'm not 'chiming' in' but that cable swap is the most apparent 'clue' you have offered. okay try the old cables and see if a difference. Eliminate that and then tie into amp again.
--------worked your ass on that sucker so basics first, mate.

Ummm, yeah. I swapped the cables left to right at the back of the amp. So surely that is indicating that it is the right channel of the amp that is misbehaving. That is, when powering the right speaker from the right channel, there is excessive excursion. When powering the left speaker from the right channel, there is excessive excursion on the left speaker. I can't see how the cables would affect that??? It appears that the additional bottom end occurs irrespective of which cable set is in use and follows the right channel of the amp.

Or am I missing something entirely here?

Cheers,
Trevor

 

[Binkman]

Okay.. just confirming. throwing darts pays off sometimes . So low frequency issue.. but might consider preamp stage v's to output amp. you have a "tight" channel on the left to compare. I don't think it's caps as prob. all same lots but a faulty transistor or good just pumps out too much?
(10pm here mate later.. bink)

 

[Trevor White]

Okay.. just confirming. throwing darts pays off sometimes . So low frequency issue.. but might consider preamp stage v's to output amp. you have a "tight" channel on the left to compare. I don't think it's caps as prob. all same lots but a faulty transistor or good just pumps out too much?
(10pm here mate later.. bink)

Thanks for your thoughts mate, I appreciate it.

Right from the outset, following my overhaul, the amp seemed to have too much bottom end. It would now seem that this is all down to the right channel. As you say, the left channel seems lovely and tight, whilst the right has just too much bass. My problem is going to be trying to identify just where in the circuitry there could be a component that might cause this. I had always suspected the caps as the amp did not behave this way prior to the recap. But I just don't know how to go about trouble shooting this.

All the best, and thanks,
Trevor

 

[Trevor White]

Hi everyone,

So, I am now on the hunt for why my lovely old L430 seems to producing too much bass but only from the right channel.

In an attempt to try and isolate where in the amp the problem might lie I first got out my old Technics SU-8022 integrated amp. I have also recently overhauled the Technics and it performs very nicely.

I removed the Lux and hooked up the Technics. Playing my 'sample' tracks I was first surprised at just how good the old SU-8022 sounded, considering it is only about 30W RMS per channel. Anyway, the important test was that the Technics drove all the speakers evenly. The bass output was nice and even on both channels, and nice and tight as well. The speaker cone excursions were very even.

I then put the Lux back in place, but this time I switched ON the Signal Processing switch and ran an RCA cable to the AUX input of the Technics from the Pre-Out connectors on the Lux. With the speakers still being driven by the Technics I was able to verify the output of the Luxman's pre-amp circuitry. Once again the speakers were all driven very evenly with good tight bass on both channels. I think that this indicates that the Luman's pre-amp output seems to be OK.

I then removed the Technics and reset the Lux back into 'Integrated' mode by setting the Signal Processing switch to OFF. After reconnecting everything I once again played my sample tracks. Right away I could tell that the right channel had a lot more bass output with the speaker cone excursions being a lot bigger than the left channel.

So, this would seem to point the finger at the Power Amp side of the Luxman's circuitry, but just what should I be looking for in trying to sort this out?

Can anyone offer any assistance?

Cheers,
Trevor

 

[Binkman]

G'day.. Does appear to be the output amp. stage. You have a good side to compare to.
You found two output transistors bad? What channel?