Recent content by George S.

  1. G

    Need help verifying if the PL14_20 Control board kit will work in my 400S2

    Personally, I cut the wire right at the solder joint, then desolder, as it reduces the mass that needs to be heated. But then, I replace all wiring, none of the old gets reused.
  2. G

    Need help verifying if the PL14_20 Control board kit will work in my 400S2

    Nothing special about the solder on those. You just need more heat.
  3. G

    Need help verifying if the PL14_20 Control board kit will work in my 400S2

    All is not lost. If you do want to clean it up some then use a brass, not steel, brush, inline with the laminations. You'll find the following link to be very good news. https://www.mercurymagnetics.com/transformer-rust-friend-or-foe/
  4. G

    what are you listening to?

    Johnny Cash.....Rock Island Line
  5. G

    1RC 20 replacement

    Looks like a voltage regulator.
  6. G

    Any danger with increasing capacitance of main caps in old gear?

    Resistors, the old PL preamps have carbon resistors. I upgraded mine to 1% metal film. It's debatable if it makes a difference. Doing so on a receiver would be a massive job.
  7. G

    Any danger with increasing capacitance of main caps in old gear?

    My understanding is larger storage caps create a larger inrush of current when the unit is turned on. This creates a potential to burn out a switch. The design engineers have this all figured out when they spec the parts. I've read that some builders get around this by installing a soft start relay.
  8. G

    Any danger with increasing capacitance of main caps in old gear?

    Jim, something Joe taught me when I was upgrading the PL preamps was this. No ceramic caps allowed. Use silver mica caps wherever economically feasible, usually low values as they're expensive. Replace electrolytics with film caps, except where a film cap would be too large to fit, so use a...
  9. G

    PL 700 Pro Build

    Thanks Joe. I'm going to have to reread this several times and think about it to understand. I see I need to read up on capacitors and their effect on frequency. Thank you!
  10. G

    PL 700 Pro Build

    Joe, O.K., so increase capacitance value to improve low frequency performance. PL had two 2.2 uF electrolytics in series + to + on each output trace to create a bipolar. Per the photograph of the old test board, a jumper replaced one cap and a 4.7 uF film the other old cap. This is how both...
  11. G

    PL 700 Pro Build

    Using the simplest measurement scheme, of halfing the the unloaded voltage with a load on the decade box. At 50 Hz the impedance is 386 ohms. At 500 Hz the impedance is 38 ohms. Interesting how the factor of 10 appears. Time to do some more reading.
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    PL 700 Pro Build

    500 Hz sine wave 3 Volts peak to peak at input. Turned up the volume some to see 4 Volts peak to peak on the scope. Left it all on the bench so I can try some other frequencies today and make sure I'm not overlooking something like I always do. Seems like a relatively simple measurement. But I...
  13. G

    what are you listening to?

    Nazareth.....Hair Of The Dog
  14. G

    PL 700 Pro Build

    Been reading about preamp output impedance and how to measure it. Measured it two ways. One way gives me 33 ohms impedance using the calculation. The other way was to use a resistor decade box to exactly half the unloaded voltage seen on the scope. Unloaded the peak to peak was 4 volts. Loaded...
  15. G

    No more 60 Hz hum in a PL2000 preamp.

    Yup, the plastic jacks are crap. If you use through hole mounted ones, use stranded wire with a little extra for strain relief. Those old traces are very delicate. I'm going to find a better solution eventually. Lee has posted a few photos here...
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