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Replacing the amplifier module in a Summit

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Craig

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The following are step-by-step instructions for replacing the amplifier module in a Summit speaker. I discovered that my system wasn't sounding quite right one day and upon further examining I discovered the woofers on one of the speakers was not playing at all. In addition the indicator light on the back of the speaker was displaying red instead of yellow or green. The constant red indicates something amiss with the amplifier. Martin Logan Service Dept was very responsive and we agreed that I would swap the amp in the speaker rather than ship the speaker to ML. Doing this saved weeks of downtime and was actually pretty easy to do. I thought I would share the process if anyone ever has to replace a Summit amp.

The process is relatively simple and can be performed by the user who is armed with some basic mechanical skills. If you don't feel confident then you may want to hire a skilled audio electronics service person. the job can be performed in less than 20 minutes and that's taking your time. Martin Logan is very response to customer service requests and provided me with a replacement amp in minimum time. They also provided instructions with some photos but I included my own in this thread since they provide a little more detail. I recommend following the instructions provided by Martin Logan and using this as supplemental information.

The 400w (200w X 2) Summit Amplifier. A powerful cool running little beast! It's made of 3 boards. The top 2 boards are the actual amps, one for the front woofer and the other for the rear woofer. At the rear corner (nearside) of each board is the two-pronged connector to the woofer. One on each board. As you can see, the amplifier is mounted directly to the rear panel and integrated with the control knobs. The assembly work is very good and well built.
 

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Craig

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Here are the tools that are required to do the job. No rocket-science slide rule needed but a good quality pair of needle nosed pliers, a 1/2" wrench as well as a 2mm and a 3mm allen wrench is required. It's important to use the right tools and the exact size so you don't distort the allen head screws or 1/2" nuts. Also shown are the printed instructions provided by ML.
 

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Craig

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The first step is to remove the top panel. This is the panel that sits on the top of the bass module that houses the light strip. It's held in place by the two small 2mm allen screws on at the top of the rear panel. Once these screws are removed you lift the rear of the top panel. the front of the panel is held in by a lip.
 

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With the panel removed you can see that the light strip is a row of leds and covered by a type of plastic film that gives it a cool blue color.
 

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Craig

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Now remove the six 3mm allen screws on the rear panel. These are the larger screws and are layed out as 2 vertical rows of 3 on the rear panel. The top panel will be off at this stage (not as shown in the photo).
 

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The rear panel is removed and you can see the bottom woofer and that the speaker cabinet is filled with batting material. Now you can disconnect the wires to remove the amplifier. I recommend using masking tape to label the wires before removing them to positively identify where they go on the new amplifier module. This is a critical step but fortunately a simple one. The worst thing you could do is reverse the power leads when you reconnect them. I don't know what would happen if you did and wouldn't want to find out.
 

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Craig

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Here is the amplifier with the + and - power supply leads attached. Note which side the + and - go to. Use a 1/2" wrench to remove the nuts attaching the leads. It's important to use the lock washers as they will help prevent the leads from vibrating loose. By the way a 1/2" socket will work instead of a wrench. Be careful not avoid touching the transistor components on the circuit board when remove and installing the leads.
 

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All necessary wires are removed. There are a total of 6.

1. Red power lead (with round eyelet)
2. Black power lead (with round eyelet)
3. Green/Yellow wire (with slip-on connector) You may need to use the needle nosed pliers to remove this lead.
4. Small red and black wire bundle with a 5-pin connector
5. Red/Black wire for front woofer with 2 pin connector
6. Red/Black wire for bottom woofer with 2-pin connector

These wires have different connectors so it there is minimal chance of making a wrong connection. The only possibilities are reversing the power leads and connecting the wrong woofer to the wrong amp I.E. front woofer to the bottom amp. However, I don't see how there could be any sonic effects from doing that. I marked one of the woofer leads with tape to be sure which amp it belong to. In addition one of the leads is shorter. be sure to refer the to the provided ML instructions just to double check when reconnecting wires to the new amp.
 

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Once you have the wires connected to the new amp is simply a matter of reversing the order for reassembly. The ML instructions recommend using locktite thread locker on the rear panel screws for insurance that they don't come loose from vibration. Personally, I don't think that step is necessary but be sure to apply a little torque on the screws but DO NOT overtorque. Snug is good. If they did come loose then you retighten or apply a thread locker if needed. My speakers are sounding really great and this was actually much easier and simpler than it looks.

Undergoing the critical Woofer Test!
 

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