FET Audio | Hi-End Audio & Electronics DIY Electronics & Repair

March 2, 2025

Boston Acoustics RV600 repair

Filed under: Speaker — Spencer @ 11:33 pm

This is a 22 yrs old subwoofer and got it for 20 usd.  Symptom is no power up.

Main issues are:

Capacitors on power all dried up except the signal path BP capacitors.  Action: changed

Transformer plastic crack and brittle.  Action: Put hot melt

Socket on amp board plastic crack and damage: remove socket and solder the wire direct on board, other side has socket and thus good enough.

A bit oscillation at the first J111 Q6 due to the volume wire is too long for the op-amp feedback path.  Add 250pF cap to ground at J111 Drain pin.

The speaker is re-cone but it still works.  Thus no need change or repair.

Since it only have one channel input for filter and I make it into left and right.  Add one more RCA for the LFE channel for AV amp output.  Disable the speaker input as it is not necessary or way to risky for the connection.

 

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January 29, 2025

SONOS SUB v1 Repair

Filed under: Speaker — Spencer @ 4:06 pm

Please watch the youtube for repair: https://www.youtube.com/watch?v=xdTP5gev3Ew

The failure mode is cannot power up.  Root cause is due to supply to digital board supply NG.  Changes D15, Q10, R77, R37 and Q16 (no need change as it still working). and set back to normal.

Note the cover is rusty and remove it and polish it to remove rust, then paint it with silver pen.

 

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Infinity SB28 Subwoofer repair

Filed under: Speaker — Tags: — Spencer @ 2:55 pm

This is a faulty subwoofer and need repair, after check the pcb, it has been repair trial and see regulator transistor poorly soldered and loose joint.  PCB trace on the pcb is weak and need careful repair and touch up all joints.  First attempt is power amp board working but oscillation after plug in the pre and crossover boards.  Later identified that the capacitors of +/-15V supply weak or not function properly.  Thus replace all the E-cap on this subwooder and all working fine.  Lesson learn is that Harman use cheap China capacitors and cause the problem not able to last.

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October 14, 2016

ProAc speaker repair

Filed under: Speaker — Spencer @ 11:18 pm

You can see from the photo the tweeter has damaged foam but it does not affect the function!  The the bass unit, the coil is open circuit and all 4 units (brought two more spare) are due to the corroded connection at the flex wire to the paper cone.  Thus this is not internal open circuit and thus I try to reconnect them using a wire as shown.  After repair, the driver can be used without any issue!

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October 14, 2006

ProAc 2.5 Clone

Filed under: Speaker — Spencer @ 9:19 pm

After I sold my Tannoy Turnberry, I buy a pair of smaller speaker from China.  It was a ProAc 2.5 clone.  The price is wonderful and I use this speaker till today!  I have modified the internal film capacitors (3.4uF and 4.7uF) to Rifa film capacitors and it seems improve a bit in the mid and high frequency.

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