Lanzar Opti Drive Plus 100 - diyAudio
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Old 1st September 2012, 05:06 PM   #1
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Default Lanzar Opti Drive Plus 100

Hi all. First post here. I was told over at diyma to post about my amp over here, so here it goes.


I got my old Opti Drive Plus 100 from a buddy a few weeks back. This was mine back in HS. I powered it up and saw that it starts out in protection mode for a couple seconds, comes out of protection mode for a couple seconds, and goes back into protection mode again. It does this with nothing connected. If I hook it up to speakers and an audio source it plays loud and clean for those 2 seconds it is not in protection. It won't come out of protection mode the first time I connect it to a power source. Only every time after. A good Opti Drive will go green immediately no matter what.

So..I decided to take it upon my novice self to figure this out.

I remembered that back in the day a couple diodes in the power supply section got hot and unsoldered themselves from the board. I soldered them back in and did not have an issue after that. I went ahead and pulled them to check them. They are fine.

The big caps in the power supply had scorch marks on them from my solfering iron (I was a teenager when I did that). I replaced them. No luck. While checking continuity I noticed that the ground side on one of the biggest caps was not connecting to the trace, which was common ground. After a couple attempts to fix this, I ended up just running a lead from the cap to the ground to see if that was it. Nope.

I pulled the mosfets off the board and checked them. One had leads that were about to break and another would keep losing resistance when I checked the closed circuit after closing the gate. I bought new mosfets and that did not help.

I pulled the output transistors and checked them too. They all test out identically.

There are no scorch marks on this board.

I tested all the little caps on the board and they all seem to at least be functional. None are shorted or open.

My next step was going to be to replace all the little caps hoping that one is dried out and cannot hold a charge. Am I heading in the right direction, or am I missing something?
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Old 1st September 2012, 05:12 PM   #2
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Here are pics. I forgot to mention that I tested the thermistor and it is fine.
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File Type: jpg lanzar2.JPG (216.2 KB, 116 views)
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Old 1st September 2012, 08:48 PM   #3
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Whats the DC voltage on each set of speaker terminals when its out of protection?
I would connect a DC volt meter to each channel one at a time and see what DC output the amp makes when it drops out of protection on fire up. Above a certain level the protection circuitry will re-trigger, so I would check that next.

Also I remember these amps suffering from opto-coupler failues so I would check those and the associated circuitry driving them. These amps were called OPTI drives because they used opto-couplers to completely decouple the audio side from the 12 volt side like PG and others did back then, so as to prevent ground loop noise issues. hope this helps some...
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Old 1st September 2012, 11:19 PM   #4
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The circuit boards on these amplifiers are VERY easy to damage. I wouldn't recommend only removing parts when you absolutely have to. It's possible to damage the vias that connect the top traces to the bottom pads. If they are damaged, when you reinstall the parts, you may not have a good connection to the trace on top and that can make the amp very difficult to troubleshoot/repair.
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Old 1st September 2012, 11:28 PM   #5
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Ok, dumb question. What are the opto couplers? I will check for dc voltage on the channels and report back in a few days.

Thanks for the advice on the board. I have checked all the traces on everything I have replaced so far. I can see how the pads can come off with too much heat.
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Old 2nd September 2012, 04:00 AM   #6
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Your pic blurs up when I blow it up to full screen but look at the center of the amp for the 6 legged devices black in color rectangular in shape. I see two at least and a possible third under the brown wire unless that's a voltage comparator which is common to this design.

If either of those opto-couplers are not working or they have bad signals from the amp your amp will drop offline into protect mode. not much other can do that on this amp since these represent the decoupled feedback from the amp back to the power supply to shut down or stay online..Really simple after you see a free hundred of this basic design. lots of name brand amps do this exact same thing. lanzar decided to use it as marketing and a product name...

And Perry is very much correct about the PCB being damaged easily you might have to hard wire thru the hole to correct for such issues if they happen...hope this helps some
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Old 2nd September 2012, 04:33 AM   #7
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Makes sense. I noticed that there were traces from the mosfets and the Thermistor that ran back to those guys. Thanks so much for all the advice.
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Old 4th September 2012, 06:53 AM   #8
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Quote:
Originally Posted by 1moreamp View Post
Your pic blurs up when I blow it up to full screen but look at the center of the amp for the 6 legged devices black in color rectangular in shape. I see two at least and a possible third under the brown wire unless that's a voltage comparator which is common to this design.
The one under the brown wire is 8 legged and different from the other 2. Those are actually 5 legged. They look like they are supposed to be that way. The same leg is missing frm both and it appears that the spot on the board where the missing leg would connect to goes nowhere. There are no marks that would lead me to believe that they were burned off. I will get out the multimeter tomorrow and check DC volts on the channels as well as verify that there are in fact no traces coming off the solder points where the missing legs are.

What amount of DC voltage would be an issue and do I test with or without an input source? I'm assuming it doesn't matter since it goes into protection with nothing connected.
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Old 4th September 2012, 07:05 AM   #9
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Adding to this. Those are 4N25 Octocouplers. Pin 3 has no connection, so the fact that it is missing on these is ok. So, based on the link below that diagrams these out, how do I test these?

Learning to Use an Optocoupler or Optoisolator
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Old 4th September 2012, 09:00 PM   #10
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Quote:
Originally Posted by Buickmike View Post
Adding to this. Those are 4N25 Octocouplers. Pin 3 has no connection, so the fact that it is missing on these is ok. So, based on the link below that diagrams these out, how do I test these?

Learning to Use an Optocoupler or Optoisolator

I would have checked for DC offset on the outputs first. Have you looked for any DC on the speaker terminals of the amp yet? No RCAs and no Speakers connected turn on the amp and use a meter to read any DC voltage on the speaker terminals. Let me know what you find there first.

Then i worry about the opto's being functional. The link you sent shows the basic operation of them so it should be simple to check the output of the opto to see if its giving you proper output . You will have to track down where each opto connects to the PWM chip to decide weather or not the signal is correct for that pin.
Those opto's are the usual culprits when one of these amps is not latching online. but you must also check the things that the opto's are connected to also to make sure they are not just being tripped by some over looked symptom.
They may be 100% functional and doing there job correctly due to uneven rail supply, DC offset on the speaker terminals, uneven lower rails, etc....
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