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Marantz 400 series AV Amplifiers - DSP Problem

Discussion in 'Receivers and amplifiers' started by Oriphus, Mar 11, 2004.

  1. Oriphus

    Oriphus Senior member

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    Anyone who has a Marantz SR4400, SR5400, SR6400, SR7400 and SR8400 and are experiencing Audio Drop-outs (the audio disappears for less than a second and then comes back), this is a problem with the new Cirrus DSP chip in the units. Marantz is aware of the problem and are offering a fix for it under warranty. This problem is also related to an overheating problem with the amplifiers.

    I have a Marantz SR5400 and will be doing a review on it in this section for those who might be interested. Need to spend some quality time with it first.
     
  2. Oriphus

    Oriphus Senior member

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    On a follow up, its not just Marantz 400 series that have this problem, other machines such as NAD, etc. also have the audio drop out with early models using that Cirrus DSP chip. The problem has been rectified by all manufacturers and if you notice the problem, your supplier should be able to fix it for you under warranty...
     
  3. jeff-o

    jeff-o Member

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    Hi, I've been having the same problems as you've described, has the problem since been resolved?
     
  4. Oriphus

    Oriphus Senior member

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    Yeah, it has been resolved now. I was talking to a technician at Marantz UK and he was explaining that the faulty Cirrus chips were also linked to the systems running hotter than normal. I PM's you with the number to contact Marant direct in the US, as well as the UK number, though i believe you are US...
     
  5. macmante

    macmante Member

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    I just bought a pre-owned SR6400 and it doesn't have the dropout problem but did have the overheating issue. I noticed one of the two large power supply capacitors (15000 uf) was bulging on top so ordered new ones and replaced them. The bulging one rattled when shaken. This wasn't part of the overheating though. I brought it home (was working on it at work) and decided to check the amplifier adjustments as noted on page 59 in the service manual. The manual says to adjust them to 4.9 mV (plus or minus 0.05 mV) for each channel. Some of mine were many times higher, 39, 27, 25 and so on. After adjusting to 4.9 the amps immediately began running much much cooler. After sitting on with no input at minimum volume and no speakers connected for 15 minutes the heat sink is now room temperature with no sign of any warming at all. Before performing the adjustment (with the case cover on) after 20 minutes at moderate volume you could not keep your hand on the case above the heat sink! It was running THAT hot. Marantz provides little sockets for making the DC voltage measurement. We have a plug at work very similar only longer with more pins and I managed to cut an old one down to just two pins then filed the plug to fit into the socket.

    As has been noted elsewhere on the web, it seems all manufacturers are on a quest to find and use the cheapest pots for these critical adjustments. Those cheapies don't hold steady over time and the voltage drifts (seemingly always upward). Some people actually replace the factory pots with high precision 40-turn types that can and do hold this adjustment steady. If the overheating slowly returns I'll be swapping mine out for precision types as well.
     

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