VU Meter Repair

A volume unit (VU) meter is a moving coil device calibrated to display the audio signal level in dB units. In hi-fi systems, the purpose of the meter is for setting the input signal level so that the needle does not exceed 0 dB. This optimum signal level prevents the oversaturation of the ferromagnetic particles on the tape when recording, and therefore prevents audio clipping. A moving coil meter has an axially mounted pivot around which the coil moves, and there is usually a return spring, which gently brings the needle back to the home position. It is very common for VU meters to fail, and on this one, the left channel meter had stopped working.

From the profile, you can see that it is just a pair of standard size meters that are joined together to make one large meter. Hence, you could use two half-sized meters in the same place.

Marantz make some of the best high-end audio equipment, and they usually carry stocks of components.

Replacement meters are available from places such as eBay but they will not have a scale that is identical to the original meter. Marantz also supply spare parts and components, and this is the first place to start your search for replacement meters.

Dual VU Meters

The original has a colourful dial and the replacement meter dial will not look as nice, so I decided to repair the broken meter. On this one, the spring contact had detached from the solder point. You can see here, I have soldered it back on and it is working fine now. The spring is a different metal and does not solder well which is why it detaches over time. This may be a typical fault of these meters.

Here you can see the coiled spring, which is responsible for returning the needle back to the -20 position on the dial. One easy way to tell if the spring is faulty is by seeing if the needle moves only up but never returns to home position. On these Marantz, it is the spring that usually detaches from one end.

Unfortunately, repair of the meter involves having special equipment such as a microscope to look at the extremely tiny spring. Usually, clock and watch repairers are the best places to take these for repair as they are used to working with small microscopic size components.

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