old school rockford punch 40dsm messes up fm reception horribly. - Page 3 - diyAudio
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Old 20th April 2011, 12:25 AM   #21
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i don't know that amp specific, but should be the bigger ones connected to power/ground 12v circuits
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Old 20th April 2011, 07:04 AM   #22
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C9 and C10 are the primary filter capacitors.
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Old 22nd April 2011, 04:15 PM   #23
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Originally Posted by Perry Babin View Post
C9 and C10 are the primary filter capacitors.
i finally received the 1n5366 diode from mouser.com, replaced it, and the noise is still there (it needed replacing anyway, though. that eliminates that problem). upon closer inspection, the capacitors look like they have leaked in the past. you can see discoloration like some sort of liquid seeped between the translucent plastic covering and its metal case. do these caps commonly go out/leak in this model of amplifier?
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Old 22nd April 2011, 04:48 PM   #24
ppia600 is offline ppia600  United States
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Almost sounds like the amp case isn't shielded and the radio is picking up the toroid pulses.
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Old 22nd April 2011, 04:53 PM   #25
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Almost sounds like the amp case isn't shielded and the radio is picking up the toroid pulses.
how is the amp case shielded?
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Old 22nd April 2011, 04:58 PM   #26
ppia600 is offline ppia600  United States
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I believe one or more of the allen screws on the edge of the board tightens on a board trace that connects power ground. This makes the amp heatsink ground to keep the rf inside. Otherwise I would think your power and ground wires are radiating due to the amp having an internal problem in the power supply section.

Actually the screw that grounds to the sink may not be on the edge, I just found a pic of a 200dsm. Its been a while since I've seen the inside of a dsm.
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Last edited by ppia600; 22nd April 2011 at 05:02 PM.
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Old 22nd April 2011, 05:18 PM   #27
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Originally Posted by ppia600 View Post
I believe one or more of the allen screws on the edge of the board tightens on a board trace that connects power ground. This makes the amp heatsink ground to keep the rf inside. Otherwise I would think your power and ground wires are radiating due to the amp having an internal problem in the power supply section.

Actually the screw that grounds to the sink may not be on the edge, I just found a pic of a 200dsm. Its been a while since I've seen the inside of a dsm.
i dont see anywhere where the allen screws could ground any traces on this model. all of the screw holes on the pcb have no traces to touch the case.
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Old 22nd April 2011, 05:21 PM   #28
ppia600 is offline ppia600  United States
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Use an ohmmeter to check continuity between the heatsink and the power ground terminal on the amp, it needs to be connected for noise shielding. The trace may be on the bottom of the board surrounding a screw hole. Be sure there is not paint or anything keeping the trace from conducting to the sink.

Some of the older punch amps used a small jumper that connected the ground trace on the board to the heatsink
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Old 22nd April 2011, 05:45 PM   #29
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Originally Posted by ppia600 View Post
Use an ohmmeter to check continuity between the heatsink and the power ground terminal on the amp, it needs to be connected for noise shielding. The trace may be on the bottom of the board surrounding a screw hole. Be sure there is not paint or anything keeping the trace from conducting to the sink.

Some of the older punch amps used a small jumper that connected the ground trace on the board to the heatsink
my ohmmeter doesnt show any continuity. if there are any jumpers, was it one that physically screwed on to the heatsink on one end and a ground trace on the other? other than that, i dont see anywhere where the jumper/wire/etc could have attached to the pcb (either the bottom or the top of the board), since none of the screw holes are surrounded by any traces to connect to the case.

Last edited by thebestofall007; 22nd April 2011 at 05:53 PM.
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Old 22nd April 2011, 06:33 PM   #30
ppia600 is offline ppia600  United States
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There should be a jumper or trace ground. Can you see the bottom of the circuit board? Maybe post a pic of the top and bottom? The case needs to be connected to ground somehow.
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