Hi Guys
I have replaced all the capacitors on the read/write and digital boards and it is now playing DCC and analogue tapes on both channels as you can see it on the display but only the Left channel is coming out the machine any idea what’s going on
Thanks
Stephen
If it shows audio on the vu meters but you can’t hear it from both the analog outputs, it’s getting lost between the PASC decoder and the outputs. Chances are that this is a very simple problem to fix. It could be a bad capacitor in the signal path, it could be a bad solder connection, it could be a connector that’s not making contact.
Starting with the output connectors and going backwards over the schematic towards the PASC decoder, try using a wire to short the right channel to the left channel. Every time you do this, you should start hearing the left side audio from the right side speaker. As soon as you get to a point where shorting right to left doesn’t give you audio on the right channel, you know you went past the point where the signal is cut off. And obviously if it doesn’t work to do this at the analog output connectors, you know the problem is outside the recorder.
=== Jac
Hi thanks for the response. Which board is the pasc decoder
Stephen
I had a quick look at the service manual. The analog outputs are on page 60. There, one of the mute transistors could be shorted but that’s very unlikely. If you short the left and right line output together and both channels go quiet, it’s the mute transistors. If both channels start playing, it confirms that the signal path between recorder and amplifier is okay. If shorting left and right doesn’t make a difference, there’s something else wrong. Try the headphones and/or the variable line outputs.
The signal comes from the left side of page 59, which takes you to the ADC/DAC board on page 91. It’s possible that C348 is open; bridge it with another capacitor of the same value to check it. If C348 is open, replace C347 and C348 both (you probably want to do that anyway because they’ll eventually fail).
If that doesn’t help, check what happens when you short pin 5 of Q305 with pin 5 of Q306. If that makes no difference, the problem is in Q306. Try the same with pin 2 of Q305 and Q306.
Then try connecting pin 6 of Q303 and pin 6 of Q304. If that doesn’t make a difference, the problem is Q304. Try the same with pin 2 of Q303 and Q304.
By now, you should have hopefully found the problem simply by trading through the schematic. If shorting pin 2 of Q303 and Q304 makes the right channel work, there is a problem with the SAA7350 DAC (sorry i mentioned the PASC decoder, i was wrong). Everything in front of the DAC (including the DAC itself) has digital signal coming in in multiplexed form, so if there would be something wrong there, both channels would be out.
=== Jac
Ok I’ll have a look next week as we’re going away in 2 days and I’ll let you know what happens
Stephen
Hi Jac
Managed to do some basic testing and I only have left channel on variable output aswell as fixed output also checked the headphone jack and it sounds like an untuned radio. Also when you say short left to right do you mean bridge them with wire just behind the sockets
Thanks
Stephen
Yes, I mean bridge them. If you tried the headphones and the have the same problem, the problem is probably on the DAC board or in the connection from the DAC board.
===Jac
Is the DAC board the board behind the Digital board as I can’t find it on the schematic
Stephen
I don’t own a DCC900 and I’m not thoroughly familiar with it. The schematic is on page 91 in the service manual.
===Jac