Hi all.

I’ve replaced all of the electrolytic capacitors on the akai am-u1. And left the original films and ceramics in place.

Some had made it to the age of 40 and others like to low leakage orange 1uf 50v nippons hadn’t.

It doesn’t sound to bad considering. Not quite up there with the Cambridge audio axa25, but not bad.

The only thing that made me pause before was the woofers moving out, slightly back in, out and then fully back in on power up.

I’m measuring a few milli volts occasionally at the speaker outputs but other than that nothing.

I assume there’s 2 film capacitors near the outputs on filtering duty.

Is this a normal occurance on budget 80’s gear?.

  • dirttraveler@alien.topBEnglish
    1·
    1 year ago

    Hmm. You checked DC at the speaker outputs? Moving in and out slightly is normal for non-relay units but all the way in and out? That’s what you’re saying?

    • wima1972@alien.topOPBEnglish
      1·
      1 year ago

      Don’t think that’s all the way in and out. I’m assuming that’ll be output from the stk461 module. Reading up it’s as you say, normal for non relay amps without a delay on startup.

  • wima1972@alien.topOPBEnglish
    1·
    1 year ago

    Hi. I’ll be back going to check with no volume. There’s no relay in there.

  • Space_Man_Spiff_2@alien.topBEnglish
    1·
    1 year ago

    Some movement would be normal in a system without speaker protection relay. I 2nd checking for any significant DC voltage on the speakers. Do you have the service manual?

  • Space_Man_Spiff_2@alien.topBEnglish
    1·
    1 year ago

    I found the schematic. The STK 461’s are directly coupled to the speakers. It looks like that there is a feed back cap and RC noise filter on the outputs (C124 & C125) Diagram shows 0V DC on the STK output. (Pin 11) It’s possible that you are getting a DC pulse on the output as the power comes up.

      • Space_Man_Spiff_2@alien.topBEnglish
        1·
        1 year ago

        I suspect that you really don’t have an issue with the amp. It’s just a normal power up effect. On the other channel it’s C224-C225. You could replace the 2 electrolytic caps, but it’s probably not going to change anything.

        • wima1972@alien.topOPBEnglish
          1·
          1 year ago

          Thanks bud. I replaced the nippons with new nichicons after the pic was taken.

          It’s the yellow 0.1uf’s at c125 and c225 I haven’t touched.

          I’m assuming they’re polyester film and two mks 0.1uf wimas would be a more modern replacement?.