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

June 24, 2021

hp 3478A 5.5 digits DMM repair

Filed under: Test Equipment — Spencer @ 12:53 pm

In fact it is not a repair but try to open up to see if any thing need replacement after over 25 years of use! Very worry about the power leakage!

  1. The Y Capacitor is using RIFA PME271 again! This is a poor reliability filter capacitors (well know to me!) used in many equipment which will cause line voltage leakage to the ground point of the equipment! You can see the body is crack and swell a bit after used some times! My experience is that I brought replacement 5 years ago and put into my Lecroy Scope but is failed again (in fact the scope is idling most of the time) when I power up the scope early this year!
  2. The 3V lithium battery inside the two meters I have is still very healthy above 3V! Very surprise to know that but the battery size is BIG.

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BSS BLU-160 setup and upgrade

Filed under: Pro Audio — Spencer @ 12:30 pm

I acquired this set (total 3 sets and other 2 sold) from Singapore Cinema of 80 people as it need to upgrade the system and move to a bigger place. Changes as below:

  1. Add heatsink on those hot chips as seen in the photos. Reduce temperature and increase life time!
  2. Changed all power supply capacitors to Good brand like Nichicon and 105C long life type at the output sections. This supply is a standard stocked unit but use normal grade capacitors and become swelled after prolong use.
  3. I changed from two analogy IN and two analog Out card to 1 Digital IN, 1 Analogy IN, 1 Digital OUT & 1 analogy Out cards.
  4. Design a digital crossover for subwoofer below 100Hz and let the 100 to 20K Hz channel handle by FDA-1B and power amp. Subwoofer channel go to another Yamaha DA2X DAC and power amplifier DSi4000 to drive JBL 4642A (also acquired together with the BSS unit in special sales).
  5. My system is driven either by Raspberry PI + HIFI berry digital Pro or CD pro drive.
  6. Software is both Foobar or Volumio with Harman Motion Control Apps in PC, iPhone or iPad. All songs is kept in NAS Synology DS212J old unit. Volumio is more easy to use than Foobar but each has its good and bad! Of course the Rasberry Pi also allow Apply play from any device in the same network!
  7. The Raspberry Pi case cover cannot fit with the HiFiberry board and thus I need to drill, file and odd shape hole to make it fit so that it can protect the inside part to further corrosion by the Humid weather.

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NI PXI-6221 DAQ Analogy Output Repair

Filed under: Test Equipment — Spencer @ 11:51 am

Acquire that from eBay but the analogy output two channels is not working! Quick check on the power supply capacitors found that the one near the DACs is not connected to +Vcc. After trace through the path, it goes to the inductor L3. Checked one plated through hole is OPEN near C83 (as seen dented at the bottom). After discussion with the seller, I want to repair it myself and he agreed. So putting a jumper wire as shown, the card is working again. Another bonus is that the Seller refunded me US$25 and thus I am buying this card at 20% discount!

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Shure Condenser Mic Repair

Filed under: Pro Audio — Spencer @ 11:35 am

The problem is noisy and sometime signal weak. Open up (screw from bottom) the mic see nothing wrong with parts but after some searching around, found one yellow wire was broken, then the next one wire. As you can see the wire strand all oxidized and become poor connection! This is probably mic is not used in Studio environment and humidity weather cause the problem after 10 years use!

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