Carver PM-1200 Service Manual

Instructions for replacing the 50/80 V Capacitors in the Carver M-1.5(T)

Before you Start:

STRONG WARNING!!! Carver amplifiers have high voltages of 120 VAC and +/- 120 VDC present during operation. They have capacitors that can store potentially deadly charges even after power is disconnected from the amplifier. Repairs to be made by qualified service personnel. We do not want you to get hurt, and we don't want you to hack up these classic amps!!! If you need assistance with a repair, we can do it at our facility, or refer you to another qualified repair facility.

Warning # 2: Solder contains LEAD. No eating in the area, and wash your hands when youre done.

Warning # 3: Make sure your bench has adequate ventilation. Youll be creating smoke (mainly from the flux), which isnt great to breathso dont.

Warning # 4: Wear eye protection when soldering.

Warning # 5: Soldering irons are hot. Take appropriate precautions to NOT get burned. While youre at it, take precautions to NOT start a fire.

Encouragement #1: Youre working on a great piece of audio gear. Work carefully and youll end up with a fantastic result! The replacement capacitors have far better performance and reliability than the originals.

If we left anything out, or if some part of the instructions is unclear, if you want additional parts, or if you have some great product idea, please feel free to contact us at [email protected] .

Tools and supplies you will need:

Soldering Iron (I have a Hakko pencil-type iron adjusted to 725 deg F that does a great job)

Solder wick 3/16 or vacuum de-soldering tool Solder (I prefer rosin core) Denatured alcohol or other solvent Cotton swabs (Q-tips)

Carver M-1.5 Capacitor Replacement Rev 110102 [email protected]

Get Started: Make sure you have plenty of room on your bench, some decent background music and have minimized distractions. Make sure the amp is unplugged before removing the cover. In the time it takes to remove the cover, the caps should have time to discharge to safe levels. Now you can remove the cover. Double check that the amp is unplugged. With the cover removed, you will see the 50/80 V capacitors at the right rear of the amplifier. Tip the amp up on its right side and rotate the unit so you have a view of the wires shown in Photo 1.

Photo 1

Clip and remove the tie wrap bundling the red, orange and yellow wires. Heat the solder joint and remove each red wire from the power supply circuit card and tie back out of the way.


Heat the solder joint and remove each orange wire from the power supply circuit card and tie them back out of the way. The board will now look like Photo 2. Heat and remove the black wires from the power supply circuit card and tie them back out of the way.

Photo 2

Using a soldering iron with solder wick or a vacuum de-soldering tool, de-solder the capacitor connections and supports from the power supply board. Each original capacitor has 4 electrical leads and 4 support connections, for a total of 16 solder joints. Take your time with this operation. The positions of the 16 solder connections are shown in Photo 3. Make sure you remove the solder to completely free each lead (if you dont, you risk tearing the trace from the board). Also, take care to avoid touching and burning wires, components, fingers etc with the soldering iron.


Photo 3

IMPORTANT NOTE: This is a good point to evaluate the project. If the project is beyond your skills, or youre simply not enjoying the process, PLEASE CONTACT US. For $100.00 (price includes return shipping in the US) we will complete the repair and return the unit (price includes capacitor replacement only, additional repairs, if needed, will be quoted separately).


Photo 4

My technique for removing solder from leads is shown in Photo 4. I place solder wick (about an inch from the end) over the solder joint to be de-soldered. I then press the side of the soldering iron near the tip on the solder wick. When the solder in the joint begins to flow, I pull the wick under the iron, which draws the solder from the joint. When all 16 solder connections have been removed, clean the board with solvent (de-natured alcohol, etc), then re-inspect and re-work as needed. Make sure there are no solder bridges on the diode pads where the wires will attach to the board.


Photo 5

Remove the screws that go through the bottom plate of the amp that secure the aluminum bracket that supports the 50/80 V capacitors and remove the bracket. The bracket is shown in Photo 5. The capacitors are attached to the plate with double-sided tape. The plate can be discarded or recycled. The 50/80 V capacitors can be removed at this point. As the capacitors are removed, watch the pins on the solder side of the power supply board to assure they are free of solder. Remove any additional solder as needed to assure pins can be removed with no damage.


Photo 6 Re-Assembly Align the pins of replacement capacitor assembly with original capacitor holes in the Carver power supply board. Take care to assure the large capacitors are on top and the FRONT and BACK designators on the PCB silkscreen correspond to the front and back of the amplifier.


Photo 7 The replacement capacitor assembly has 8 circuit connection pins and two support pins. Carefully feed the capacitor assembly leads into the corresponding power supply holes and check the solder pads to assure all leads protrude through the Carver power supply board. The capacitor assembly should sit about 0.1 above the Carver power supply board. Solder all 10 connections. Trim the long leads flush to the top of the solder joints. Solder the black wires to the Carver power supply board. Refer to Photo 2. Solder the orange wires, then the red wires to the diode leads on the Carver power supply board. Be VERY careful not to let solder bridges or whiskers short across any of the red or orange wires. When black, orange and red wires are in place, clean the flux from the board with solvent and swabs. Now, do a thorough visual inspection with a magnifying lens to make CERTAIN there are no solder bridges across the wire connections and that the wires are in the correct locations. Place a tie wrap around the black, orange and red wires to secure them. If the amplifier is to be used in a mobile application, add dots of epoxy as needed to secure the capacitors to the board and amplifier case.


Photo 8

Heres how the capacitor adaptor should look when the soldering has been completed. Now, its time to test the amp. Take one more look at the installation to assure there are no solder bridges, the leads are trimmed, there is no debris in the amp, etc. Don your safety goggles and apply power to the amp. If the amp comes up in protection mode, there are probably solder bridges across the transformer inputs. Supply Voltage Adjustment Adjust the supply voltages per the instructions in the service manual, using extreme caution, as high voltages are present: Power up the amplifier with no input and no speaker connections and let it idle for at least 15 minutes. Set your DMM or VOM to the 200vdc scale. Connect the BLACK lead to the common connection between the two large power supply caps.



Connect the RED lead to the post on the power supply cap where the RED wires attach. Adjust RP1 on the Power Supply PCB so that the voltage reads 122vdc. Warning, make SMALL adjustments on RP1. NEVER allow voltage to exceed 140vdc

Idle Bias Adjustment Adjust the Idle Bias voltages per the instructions in the service manual, using extreme caution, as high voltages are present: Power up the amplifier with no input and no speaker connections and let it idle for at least 15 minutes (or simply keep it powered from the power supply adjust). Set the DMM/VOM to the 200mvdc scale. Connect the leads across R87 (large block resistor to the right of RP1 on amp PCB). Adjust RP1 to read 4 mV +/- 0.5 mV. Again, make very small adjustments!!! Repeat steps on the second amp PCB. Final Assembly Replace the cover on the amplifier. Your Carver repair is now complete. Happy Listening!!!

Carver PM-1200 Service Manual

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