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  1. wattsabundant

    Another Phase Linear 400 Series one rebuild thread

    That board is one of the better ones I've seen. The amp must be all original as the board doesn't appear to have been worked on.
  2. wattsabundant

    Dynaco VTA ST 70

    Who/what is a ST120 monoblock? I have 2 ST120's from an abandoned conversion to a mosfet amp.
  3. wattsabundant

    Greetings from the far north

    I can count about a dozen paper mills I've worked at from Maine to Louisiana. One time I went straight to the airport after leaving the plant. Stunk up the plane with the stench from the plant. Everyone was looking around for the offender. Kept my head down. As for the amp, the issue is...
  4. wattsabundant

    Lost ball in the tall grass

    My weekly broken record comment: Use the light bulb test set. Read the service manual cover to cover before doing anything. Re-read the section on troubleshooting. Read for a third time how to test transistors. Replace only confirmed failures. Check R101, 7.5K/2W on driver board.
  5. wattsabundant

    PL400 glad I found this forum.

    The original R/C networks are removed along with the original output binding posts. The relay board mounts on the new output binding posts. As Lee said the new R/C network is on the board. The resistor between binding post and input jacks is cut out, at the body of the resistor. This leaves...
  6. wattsabundant

    PL400 glad I found this forum.

    I don't see a fuse on the fan. Those heaters can get quite hot and possibly melt the the AC wiring. I don't think the box is big enough for extended testing. Attached are photos of a loadbank I built for testing inverters at the day job. The wiring is transformer magnet wire with high...
  7. wattsabundant

    Power switch mod?

    The thread is unobtanium power switch. I haven't looked at it in a few years. I just breceived an updated PCB that will allow multiple triac packages to be used. Stay tuned.
  8. wattsabundant

    Wood transistor

    Taking this sideways, does Nav have anything to say about wood?
  9. wattsabundant

    PL400 glad I found this forum.

    400 manual attached. If there is substantial DC on output and no failed drivers or outputs, check Q1-Q5 and associated diodes. If the leads of Q1-Q4 have turned black, change them out. See service bulletins for differences in transistor pinouts. Bias is last thing to check and only after...
  10. wattsabundant

    Audio Research sold by McIntosh Group to former sales director

    Wow, I've been out of the tube scene for 25 years. Didn't know ARC was still around.
  11. wattsabundant

    PL400 glad I found this forum.

    Attached is the 400 manual read it cover to cover. Re-read the troubleshooting sections and service bulletins. See the bulletin that suggests only certain transistors (RCA 410) for the drivers. The channel will oscillate at high frequency with with Motorola MJXXX and 2SD555 used as drivers...
  12. wattsabundant

    PL 3300 Series II rebuild/upgrade

    Whether the pot reads zero ohms or 10 ohms when at minimum position it doesn't matter. You would likely see about the same thing on every pot. For the regulators look at my post #55. On my 3300 I found that the raw voltage from the rectifier at 120 VAC input was 18 VDC. At 110VAC the...
  13. wattsabundant

    Motorola SJ5744-2 TO3 style transistor ID/Info

    They are showing 1985 date codes, if you believe that. I would say it's not very likely they are counterfeit. Probably an OEM's part number. I have a late 70's D.A.T.A. book for bipolar transistors I can check in a few days.
  14. wattsabundant

    PL 700 Series ii power switch

    Yes, I've sold a few here and there but haven't really pushed them. I have a new board being made that will accept 3 different cases. Attached are some photos. The triac mounts on the bottom of the board and connections on the top. The board uses standoffs and the lower screw that the...
  15. wattsabundant

    PL 700 Series ii power switch

    BTW, Mouser sells the mounting bracket. I did some testing a few years back. When the AC switch closed, I recorded inrush currents up to 145 amps. I developed a PCB and a solidstate switch (triac) to do the heavy lifting. The triac has a max input current rating much higher than anything...
  16. wattsabundant

    PL Similar to Dynaco - Is The Transformer The Real Basis For WOPL Rebuilds?

    This thread started out with a mention of Dynaco transformers which is my direction here. My first real job in 1978 was at Custom Coil in Zanesville, Ohio. I was more or less an engineering tech. I learned a lot about transformers that I never wanted to know. It was BORING. I did a lot of...
  17. wattsabundant

    Phase Linear 400 Series II Input Sensitivity Question

    It seems to me that Wombat is drawing a correlation between the maximum output level of the preamp and the maximum output power of the amplifier. According to his statement, the amp only needs 1 volt from the preamp to achieve maximum output, about 210 watts. Any further increase in the...
  18. wattsabundant

    Mark goes at it again... just bought a PL700/II!

    has anybody tried the generic stuff on Amazon? Since I bought a Hakko desolder gun I don't used much wick any more.
  19. wattsabundant

    To ground or not to ground?

    Does anybody know what the National Electric Code (NEC) says about a 3 wire receptacle that leaves the ground pin floating? Is it a code violation? One of the conclusions of the app note reads as folows: NEVER, NEVER DEFEAT THE SAFETY GROUNDING of any device having a 3-prong power cord. The...
  20. wattsabundant

    Power transistor help

    First you have to adapt the transformer to the chassis which likely means a pieced of sheet metal. It may not be relevant, but the C500 inverts one channel and then reverses the polarity of the binding posts. Using the Carver transformer in a 700 chassis will reduce transistor heat dissipation.
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