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I tell a client that the defect is corrected then if they want restoration, we can discuss it and specify what they want done to the working unit and set a price. It is habit to replace caps but most are not in need of it. There are measurements that would indicate whether there is an higher risk of failure and age is not a strong indicator alone. Just as in the case of preamp tubes, a high percentage of caps that are replaced where perfectly good and would continue to be for years to come.
Regarding the tape deck, there was a preventative maintenance schedule used for commercial tape decks in most studios, wear items that did wear based on hours of use such as pucks, guide bearings, tensioner bearings etc. Heads were not time replaced but performance and wear based. At $12000 for a head stack on a A800, it was not done so routinely, but as needed. Going into a studio with a deck with a performance defect and handing the manager a $25,000 bill would not go over too well unless you could prove they needed it.
The SV3700 did not get shotgunned in my shop and we did thousands of them. The parts that failed contribute to out of spec performance of the deck were replaced but not randomly. The source of the noise in the case you mention was easy to pinpoint due to its sonic finger print. The same way wear items in an analog deck were determined through the artifacts left in the wow/flutter signal analysis. The rotational period of a worn part showed in the frequency of the artifact. A take up tensioner versus capstan for example had quite different sonic impact on the wow/flutter measurements. The same method is used in determining wear items in many mechanical systems, from watches to race engines. In the case of a digital deck, using the wave analyzer on the acoustic sound of the transport could pin point worn parts by noise frequency and frequency variation, no two gears or cams had the same rotational speed so sounds created by each simultaneously could be separated and measured. After viewing known good units, there were benchmarks to compare to.
The reason Panasonic recommended replacing everything was that neither they nor most of their warranty stations had the test instruments to measure anything in the transport. A $100 surplus wave analyzer would have solved that problem. Tascam did the same thing with their DA-88 transports but the wear items were very different in terms of wear rate. One of their plastic cams was subjected to several times the stress by followers than the other two cams. Another effective tool was a lab type strobe to actually freeze the image of a moving part, with a distinct visual sign of vibration or wobble.
Panasonic made a device that aided alignment that was not used by Panasonic US and they gave me one that did not work. I figured out how it worked and repaired it. It was pretty cool, when connected to a scope it allowed a graphical representation of track position. It was used in final alignment at the factory but not in the service shops. All those transports of the DAT/DA88/ADAT era were very easy to repair once a tech had the right tools and a bit of experience. Seeing many of the same models over and over again really helped.
Regarding the tape deck, there was a preventative maintenance schedule used for commercial tape decks in most studios, wear items that did wear based on hours of use such as pucks, guide bearings, tensioner bearings etc. Heads were not time replaced but performance and wear based. At $12000 for a head stack on a A800, it was not done so routinely, but as needed. Going into a studio with a deck with a performance defect and handing the manager a $25,000 bill would not go over too well unless you could prove they needed it.
The SV3700 did not get shotgunned in my shop and we did thousands of them. The parts that failed contribute to out of spec performance of the deck were replaced but not randomly. The source of the noise in the case you mention was easy to pinpoint due to its sonic finger print. The same way wear items in an analog deck were determined through the artifacts left in the wow/flutter signal analysis. The rotational period of a worn part showed in the frequency of the artifact. A take up tensioner versus capstan for example had quite different sonic impact on the wow/flutter measurements. The same method is used in determining wear items in many mechanical systems, from watches to race engines. In the case of a digital deck, using the wave analyzer on the acoustic sound of the transport could pin point worn parts by noise frequency and frequency variation, no two gears or cams had the same rotational speed so sounds created by each simultaneously could be separated and measured. After viewing known good units, there were benchmarks to compare to.
The reason Panasonic recommended replacing everything was that neither they nor most of their warranty stations had the test instruments to measure anything in the transport. A $100 surplus wave analyzer would have solved that problem. Tascam did the same thing with their DA-88 transports but the wear items were very different in terms of wear rate. One of their plastic cams was subjected to several times the stress by followers than the other two cams. Another effective tool was a lab type strobe to actually freeze the image of a moving part, with a distinct visual sign of vibration or wobble.
Panasonic made a device that aided alignment that was not used by Panasonic US and they gave me one that did not work. I figured out how it worked and repaired it. It was pretty cool, when connected to a scope it allowed a graphical representation of track position. It was used in final alignment at the factory but not in the service shops. All those transports of the DAT/DA88/ADAT era were very easy to repair once a tech had the right tools and a bit of experience. Seeing many of the same models over and over again really helped.
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