BA283AV - oops!

jrmintz · Jul 2, 2004

Hi All,

In a moment of stupidity I fired up my imitation 1290s with the BA283 cards in backwards. It's not hard to do (for me anyway). Am I likely to have toasted anything? I can't tell from the schematics and they work, but the distortion is too high.

Thanks :sad:

CJ · Jul 2, 2004

Check the circuit for a protection diode in series with the pwr supply.
Usually a 1N4xxxx or something.

jrmintz · Jul 2, 2004

Thanks, CJ.

jrmintz · Jul 2, 2004

I think my cards are OK. The problem I have is a 60-cycle hum, I guess from a ground loop somewhere. Here is the schematic I've been using:

http://www.jlmaudio.com/Schematic.htm

Click on 'JLM module and BA283'. What I'm wondering is, is it safe to lift one end of the 12 ohm/1 watt resistor or the 270 ohm resistor? Any other ideas?

Thanks

peter purpose · Jul 3, 2004

Seth,
Are you only taking 0V to chassis at one point only (including the power supply)?

peter

jrmintz · Jul 3, 2004

Hi Peter,

Joe Malone figured it out - I never would have gotten it. I used an 18-0-18 transformer without realizing it and Joe said that would let the hum through the regulator. Gotta get a 24-0-24.

Thanks!

:guinness: :sam: :guinness: :sam:

Ian MacGregor · Jul 3, 2004

Let the hum through the regulator?? Wow, I've never heard of that. Is that because there isn't enough headroom with the 18-0-18??

Ian

Tekay · Jul 3, 2004

You need atleast 3-4V differens between in and output to get good regulation! I did the same mistake with my first 1290 unit!

BA283AV - oops!

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