Another 2285B, this one has problems.

Discussion in 'Marantz Audio' started by 1978_DREAMER, Jan 29, 2018.

  1. Jailtime

    Jailtime Standin' on a corner Subscriber

    Messages:
    11,348
    Location:
    Velva ND
    So that 1.08V is your DC offset, and you can't adjust that? Waaaay too high.

    Have you checked the power amp connectors to make sure they're plugged in right? Sounds silly, but back when I did an 1180DC, I managed to get the connectors offset by a pin so one of the pins wasn't getting power at all. Took me a while to figure out why my rebuilt 1180DC was only making 72 WPC. :idea:
     

     

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  2. 1978_DREAMER

    1978_DREAMER AK Subscriber Subscriber

    OK, I put the main amp back into the circuit and made sure the pins connected correctly. The right channel (which plays), DC offset floats from zero +/- 0.010V, Idle Current does not register on the meter. The left channel (doesn't play), DC offset floats worse at zero +/-0.100 but the Idle Current can be set to 30mV. After I messed with this for a while I hooked up some test speakers and gave it a music feed through the AUX terminals. The right channel plays the left is dead for both 1&2 speaker outputs. Jumping the Pre-In and Main-Outs yielded no difference no left channel. The right channel had some static. I pulled the jumper back out. I tested the filter switches, the 9KHz didn't seem to cause anything but the 15KHz forced the speaker relay to kick out with a snap and the dim bulb tester lit up. All push switches have been cleaned twice.

    Tonight the speaker relay kicks in and out about every 10 seconds, with no speaker connections and volume all the way down and no push switches engaged. When I test for sound the left channel is dead and the right channel is strictl

    This unit looks like it has been messed with by possibly more than one person.

    Its serial number has an XP in it and what I was able to find was that this is a military unit. It has a voltage selector but it also has the switched and un-switched receptacles. The input voltage is currently set at 110V and my available house voltage is about 119V. The other input options are 120V, 220V & 240V. I'm wondering if my low voltage readings can be caused by this setting. I pulled the selector and tried to set it to 120V but the pin connections were rattle loose in this position. That's probably why it's set to 110V.

    I'm going to keep exploring, there are probably multiple gremlins. I may put the original 2SA798s and trimmers back in to see if I can get back to some output. Any tips are welcome.

    Jerry
     

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