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

March 3, 2025

Pioneer DV-733A repair

Filed under: Others — Spencer @ 12:22 am

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I nice gentleman give me this player for free.

The issue is can power up but take 15-20 mins to warm up and then work for CD.  Oh another supply issue for pioneer?  It is.

After open up, check the supply board and it is a little bit sicky and seems like ecap leakage.  Thus take out few and measure and conformed the issue.  Thus change all the caps 100% except the high voltage cap is using Japan brand.  Also touch up all the solder joints and paint the casing at rusty locations besides cleaning.  

Lesson learnt: Pioneer is a good product but many model buy a cheapy power supply from somewhere which use cheapy non Japanese capacitors to make the product to last 5-10 years!

One more problem, the FWD button become STOP button, checked resistors on the control board is fine.  Later found the 5V is a bit low and thus modify one resistors to bring up the voltage to 5.2V, now the FWD button function without issue.  Reason is that the keyboard use resistors to set the input voltage for the MCU ADC to measure and determine what button is pressed. 

Good design product and easy to disassembly for service.

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Arcam DV78 repair – no disc

Filed under: Uncategorized — Spencer @ 12:11 am

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Is it laser issue?  Not really.  It is a good build DVD player by Arcam but use a Korean DVD rom with poor components – capacitors.

The main board and power supply board all use Japanese capacitor and audio grade!  What a waste for this WM8740 DAC also.

I take out the dvd rom and use a USB to parallel connector to put that into my computer but the rom cannot detect CD or DVD.  I am think it is the laser issue.  Later I observed one capacitor body a bit dirty and looks like chemical contamination.  I take it out and measure it, oh it cannot be measure at all!  totally dead.  Thus I start to take out few more capacitors and found most of them are almost dead or left 10-20% of capacitance value with high internal resistance.  So action is to change all the smd capacitor on the dvd rom.  After that the computer connector is able to read CD and DVD disc!!!

As usual, do clean up and touch up with paint pen on any rusty casing on the set.

Lesson Learnt, do not use Korean made spare part in your high end product!  they all use cheapy capacitors which can last 5-10 years only.

Still have a bit issue as some CD cannot be read when power up.  Only able to read after playing for 15 mins.  Anyway I have order a laser head for this CD rom drive and will replace it to see if better.

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March 2, 2025

D1V2 Zen use PMD100 digital filter

Filed under: DAC — Spencer @ 11:57 pm

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Use the old PMD100 to SM5842 board as I still have it on hand.  But need cut trace as what is 

For PMD100 converter board, cut trace between pin 12 and 13.  Short the pin 13 to pin 14 (ground) – PMD100 set to 16 to 24 bit input mode with Left Justified 24 bit.

If you want to change the PMD100 converter board to 24 bit ouput mode (for PCM1704), you have to set pin 10 from L (ground) to H (5V). Short pin 10 to pin 11 if you can isolated the ground connection on pin 10.  Then you have 24 bit output mode.

I use a new converter board so that cutting the ground connection for pin 10.  It is a bit difficult as need to do on both side of trace, after then put a smd 0 ohm resistors for pin 11 and pin 10.  

For WM8804, also need to set to L justified mode by putting the two 10k ohm resistor to the correct position as in photo (R214 and R215).

PMD100 sound very different from DF1704 and DF1706.  It is more clear and also smooth in mid and thus more musical feels.  I think it sound better!!!  Some people say PMD200 is even better!  Need to try in future.

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Boston Acoustics RV600 repair

Filed under: Speaker — Spencer @ 11:33 pm

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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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