Dead Filter Capacitors, Marantz PM-8 Restoration

Just a short post here while I am in the middle of repairing / restoring an absolutely massive Marantz PM-8 integrated amplifier.

These main filter capacitors sit in the power supply and do all the ‘heavy lifting’ required to make the power supply smooth and quiet. All four 15,000uF capacitors have literally spewed their contents all over the insides of this beautiful amplifier.

The repair involves removing these dead capacitors, cleaning the chassis and installing new parts. I’m using higher capacity, higher spec Illinois Capacitor (IC) parts in place of these original Matsushita caps. It’s astonishing that this amplifier was even working with this level of damage to the power supply!

I wrote another piece on dead caps in a lovely Pioneer SX-1250 and on the complete overhaul of this SX-1250.

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At first glance, I could see lots of dust, but not much else

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After thoroughly washing the whole chassis, this was revealed – the corrosive mess on the bottom panel, underneath these capacitors.

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Obviously, they had to come out and be replaced…

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So here they are. Note the electrolyte residue and crust aroun each vent hole, a sure sign that they all must be changed. This venting happens when the internal pressure builds up, due to resistive heating. The reason for the resistive heating is the deterioration of the electrolyte over time. The cap starts to flow DC, which its not meant to do. As current flows through the capacitor, it heats, and this is the result.

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All four are dead, completely, totally dead. No option here but to throw them away. New parts are on their way!

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New parts next to old. Here you’ll note that I’ve specified uprated replacement parts, but they are still smaller than the originals.

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Very high-quality parts from Illinois Capacitor, these have proper hex nut fasteners to really provide low impedance connections.

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New capacitors in the original brackets. I carefully selected the new parts to ensure they would fit, and look factory.

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Perfect fit, and the look is very much similar to the factory parts. This is an excellent improvement on what was in there and will sound far better than the original parts.
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Time for the bin!

2 thoughts on “Dead Filter Capacitors, Marantz PM-8 Restoration”

  1. Unfortunately you are not living in Portugal, otherwise I would ask you to repair one of my two Shanling CD-T80 cd player, as well as other of my poswer amplifiers…

    I believe you usually do a very good job for your customers.

    Best regards,

    A. Cerqueira

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