Vestax pcv-002 clone

[allachikatillo]

Hi!

I'm trying to clone vestax pcv-002 from original circuit. Made the PCBs, but it doesn't work properly. The volume is low, pots doesn't much effect the sound (completely turned down pots still sending signal) and phones doesn't work as well.

I've checked the pcb and everything is connected right. But I find out that semiconductor 2sc1627 is to weak to supply U19 and phones pcb part. This gonna make me crazy about this circuit.

What should I check or re-check, to find the problem?

[Mick Bailey]

What voltage are you getting on the 2SC1627 collector and emitter pins, measured to ground, both with and without the 'To Phones' load connected, and the voltage from base to emitter?

Also, are you certain that all the polarized caps are correctly oriented?

If the pots still send a signal when turned down, either you have some signal leakage due to perhaps a bridged solder joint, or there could be a grounding problem.

[allachikatillo]

What voltage are you getting on the 2SC1627 collector and emitter pins, measured to ground, both with and without the 'To Phones' load connected, and the voltage from base to emitter?

Also, are you certain that all the polarized caps are correctly oriented?

If the pots still send a signal when turned down, either you have some signal leakage due to perhaps a bridged solder joint, or there could be a grounding problem.

Hi Mick!

Its about 1,2V on the E, C is 15V measured to ground, B to E is 9V, E to C is 14V. No matter with or without "To Phones" load connection. U7 V+ pin is 1,2 V. Every Cap is wright oriented, and PCBs is without solder bridges.

I surmise thats its all about GND or supply in general. I have 2 PCBs with separated ground planes with single point ground connection for GND, GND1 and GND2 (the second PCB). Maybe I misread the schematic and make a mistake with layout?

UPD: Strange thing happen - if i totally disconnect GND2 point on H2C/CN2J the LED11 (Power Led) is still working (while the pwr is on). How it can be explained, there is no any GND connection on this board.

[Mick Bailey]

Your transistor voltages are way out. It looks to me like there may be an excess load pulling the emitter voltage down. Because you've eliminated the 'to phones' connection then the next thing is to also lift one end of R194. If the output voltage is still low you've probably got a damaged transistor because a 9v base-emitter reading could mean the transistor is shorted. It should read about 0.7v.

If this is the case, then you need to find out if excessive load has damaged the transistor.

The LED has to have a voltage drop across it - it cannot run off just a positive supply. Measure the resistance of the cathode to ground.