ONKYO M-5550 Stereo Power Amplifier

Onkyo M-5550 is a japanese stereo power amplifier manufactured in 1989-1991. It is identical to M-502, produced on the different market. Higher model M-504 it’s also the same construction, only huge VU meters was added. Also the highest M-508 is a very similar construction. These all means that M-5550 (M 502) is a beast, is the cheapest and sounds practically the same like his older brothers.

This amplifier needs (if it is in original state) some minor repairs. After 30 years several capacitors need to be replaced, especially these 330uF which are very close to resistors and work at the high temperature. In mine these capacitors had a half of their nominal capacitance and huge Vloss.The BIAS should be corrected too.

After small service Onkyo plays and sound beutifully – very good choice for a price.

SONY TA-F70 cleaning


YAMAHA NATURAL SOUND AMPLIFIER A-1020. Refreshing process.

SABA MI 215 – refreshing

This old SABA came to me a few days ago … It was planned to be my second – bedroom – system with self made speakers. After turning it on I was a little bit confused – SABA did not play as good as people said. Below slide show from refreshing proccess – after this operation SABA came back to alive – has its whole power and beat!

Philips FA960 – repair

Philips FA960 – came to me as broken. There was a try of repairing by someone else but with no success. Right channel played much worse than left one.



What was wrong?

  • STK3082III is in the place of original STK3102III
  • R732 – is burned
  • R734 – wrong replacement inserted, someone used 150ohm instead of 180ohm.



Amplifier has been cleaned – all switches and knobs –  and all electrolitycs capacitors has been measured – 24 of them need replacement. Here (->) the result of measuring main filtering capacitors – should have 6,8mF and after almost 30 years there is only 5,77mF 🙁 I have made also a modification from 220 -> 240V according to service manual guide.This Philips amplifier is a very near to Grundig A9000 and Marantz PM80. A big advantage of Philips is easy change to 240V what makes this one much safer in use. STK modules are very sensitive for voltage supply and life much longer in Philips.

All new capacitor are Nichicon Gold for Audio.
Below amplifier after repairing with new, original STK3102III.
Now amplifier plays like as new one – great 🙂

Technical specification (most important parameters):

Service manual available on https://www.hifiengine.com/manual_library/philips/fa960.shtml