What's the circuitery after the I/V converter?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi!

I recently purchased a Philips CD150 for no money at all, and it had a few problems, the tray wouldn't open properly, and it would randomly refuse to play cds.

The tray problem was easily solved as it was purely mechanical, just a lack of lubrication.
For the rest, I changed all the caps, in both the dac board and the drive board. I was inspired by this blog: Inside Classic Audio: Philips CD150
Everything now works and it sounds great!

Looking at the service manual, I was wondering about a certain part of the output circuit. Please see in the attached schematic, I understand it is a classic I/V amplifier and a low-pass filter after the DAC, but I wonder what the circuitery I've marked (with all the transistors) is, and what it does.

Thanx in advance!
 

Attachments

  • Ska?rmavbild 2018-01-02 kl. 09.25.03.png
    Ska?rmavbild 2018-01-02 kl. 09.25.03.png
    485.5 KB · Views: 158
Last edited:
Not an expert in electronics but I think they are muting circuits. You can try to bypass (in parallel with) the 100 µF electrolytic capacitors (2384/5) with small value film capacitors. You can also replace them with OS-CON polymer capactiors.
For the re-caping I did stick to the original values and sorts, except for the couplings ones you mention. Although I didn't want to go too low on the value, so I used polypropylens, 10uf, which seems ok since my amp's input has an impedance of 50Kohms.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.