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  1. T

    NAD 3150 "buzzes"

    The transistors are amplifying an AC signal which is your audio signal so as long as it's in the millivolts that is normal. This is an older NAD amplifier. I'm afraid it's entirely useless looking for faults before the entire thing has been recapped. These days, I find almost every single...
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    Motorola MJE243/ 253 in NAD 3140

    I'm working on a NAD 3140 integrated that uses these transistors as drivers for the power amplifier. Some of its outputs have failed and, while the drivers test well and consistently on an atlas DCA, I'm weary as I don't have a curve tracer to fully verify their operation in circuit. I've heard...
  3. Random tech pics

    Random tech pics

  4. Board back.jpeg

    Board back.jpeg

    SL-1510 board solder side post restore
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    Hitatchi HT550

    You have to make some sort of jig that elevates the turntable while allowing access to the underside, so you can access the adjustment pots while the turntable is rotating.
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    Hitatchi HT550

    The main issue with these is the use of 2SC458 transistors. The HT-550 is full of them. Use the KSC1815Y to replace them. The speed selector switch will also require attention. It's a wafer switch type most commonly seen in Technics SL-1500 and SL-20/ 23 turntables and is bound to need...
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    Transistors Technics SU-C04

    For 2SA1123/ 2SC2631 use KSA1013Y/ KSC2383Y
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    Repairing Run Away Speed Problem on Technics SL-5300 series Turntables

    The leaking electrolytic capacitors in the drive circuitry should worry you as well FYI
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    Can I replace this 3.3µF electrolytic capacitor with a 1µF film?

    I would like to keep the original values but I don't currently have any 3.3 films. It looks like I'll have to just postpone this and order some. I do have Panasonic SU bipolar electrolytics (same components as original), but they are measuring high at 3.8µF ish. The signal goes into a low pass...
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    Can I replace this 3.3µF electrolytic capacitor with a 1µF film?

    I'm recapping a Technics SL-P555 CD player and I've run out of 3.3µF WIMA MKS2 film caps for C809 and C810. However, I have most values 2.2µF and under as either MKS2 or R82. As C809 and C810 are in the audio path, might the better dissipation factor and DC leakage specs of film permit using a...
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    Repairing Run Away Speed Problem on Technics SL-5300 series Turntables

    It's more than likely the speed select and quartz/ adj switch. It's a classic 1970's slide switch with small contacts that sit on a rail and these often need cleaning. It will need to removed from the unit, disassembled, cleaned and relubricated. I did precisely this job for an SL-5300 a couple...
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    Repairing Run Away Speed Problem on Technics SL-5300 series Turntables

    Well done. There's every chance that this fault occurs in this motor due to ageing and leaking electrolytic capacitors causing vibrations. I worked on one recently where almost every electrolytic had leaked and was EOL. When certain electrolytic caps get bad enough in these motor controllers...
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    Looking for current substitutes for 2sa953 and 2sc2002

    KSA1013/ KSC2383 should work for these.
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    Technics SA 300 stumped

    Really got to pay a lot of attention to solder in vintage Technics equipment. If you're working on your own and don't have to pay for the time, it's best to resolder as many active devices, connectors, user controls, ribbon cables and whatever else you can find. The 80's stuff is worse than the...
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    2SA1306/ 2SC3298 replacements required. No dice...

    Following up on this after finally obtaining KEC Semicon KTC4370/ KTA1659 from LCSC. Turns out these are perfect replacements. I think they are very good parts as outside of them working very well, when I blew some up by haphazardly testing a shorted SVI4003 in a Technics SU-V40, only 1 failed...
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    Technics SVI4003/ SVI4004 production change causing failure?

    I've seen around 10 examples of amps using SVI4003 and SVI4004 'current drive' power amplifier chips, a number of which having severe damage with transistors blown apart and resistors burnt to crisps etc, which I believe are cascading failures originating with shorts inside the SVI IC's...
  17. V45A.png

    V45A.png

    SU-V45A power amp
  18. V40.png

    V40.png

    SU-V40 power amp
  19. Schematics

    Schematics

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    Vintage CD players are a pain

    Vintage CD players are such a pain in the a$$. I've sold a good number over the years after servicing them and they're the only type of equipment I've ever had complaints about, weeks or months after initial satisfaction from the buyer or owner. Only a few, but that's enough for me given the...
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    PCB connector help

    Thanks for the suggestion. I actually found this - https://www.digikey.co.uk/en/products/detail/wago-corporation/233-404/15575052
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    PCB connector help

    I have a 4 terminal PCB connector from a 1990's Technics CD player that requires replacing. Can anybody advise a suitable replacement available on DigiKey preferably? The original part number is RJS1A1704. It accept bare wire and has a bracket that clamps down on the wire and has to be pushed...
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    Shure M35X broken body?

    I would have posted a picture but I figured this is a semi-popular DJ cartridge and somebody would have had the same issue. I found some old Gorilla epoxy to stick these back together with and it seems to be holding up well. It all appears self-explanatory really. I just can't fathom why...
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    Shure M35X broken body?

    I have 2 Shure M35X cartridges here that have separated into 2 pieces. Upon first glance it seems like the cartridge is merely glued into a plastic shell. I have already glued them once but they have broken again after a couple of months sitting on the shelf. The first attempt was with hot...
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    2SA1306/ 2SC3298 replacements required. No dice...

    Are there any readily available substitutes for this pair? They have a very high fT. The datasheets boast this as a primary feature, but simultaneously state the part is designed for power and driver amplifier applications. Why would such a high fT be necessary for a power amplifier...
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