Dilshan R Jayakody’s Web Log

A few months ago, I received this Onkyo PE-C50 stereo graphic equalizer from a friend because it was not working. He gave me this equalizer for free because he was planning to discard it due to some problems with its controls. Front panel of the Onkyo PE-C50. The Onkyo PE-C50 is a vintage, 7-channel, stereo digital graphic equalizer. This unit is manufactured in Japan and operates on 110V AC power only. Front panel controls allow me to adjust each channel separately or simultaneously. This unit also got 5-channel preset memory to save graphic equalizer settings. Besides a graphic equalizer, it comes with an attractive 2×7 channel spectrum analyzer. At initial testing, I found that the unit's controls and spectrum analyzer would randomly stop working. After controls at the front panel freeze, I have to restart it to get it back in working condition. PCB of the Onkyo PE-C50 graphic equalizer. To troubleshoot, first, I try to find the service manual for this equalizer, but I couldn...

Few weeks back I got Victor SEA-50 stereo graphic equalizer from one of my friend. This is 10 band stereo graphic equalizer manufactured by Victor Company of Japan (now JVC Kenwood ) around 1970 - 1980. SEA-50 consist with 63 transistors and it provides ±12dB control range for 32 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 12 kHz / 16 kHz / 20 kHz center frequencies. The SEA-50 which we got is not working properly and most of its controls may generate distortion above +8dB and below -8dB. Apart from that left channel of this receiver has low volume and distortion. Defective transistors in control board (next to 2SA493). After few hours of checkup we identify few defective transistors ( 2SC982 ) in control board and we replace those with 2N3904 NPN transistors. Subsequent to this fix, all controls of SEA-50 start to work again on its full range (±12dB) by without producing any distortion or clipping.