Hi all, I have a Denon DRW-585 twin cassette deck which I bought a couple of years back for the purpose recording some computer game tapes. I bought it unseen/untested on ebay and unfortunately when testing it the right channel was recording very badly distorted and cutting out, I put it in the cupboard and forgot about it. I thought I'd try and get it going again and try to learn something.
I have access to a DMM and a scope however I'm no expert and have been trying to diagnose the issue. I thought I tracked it down to the bias circuit and could see the bias on the right channel jumping up and down in voltage and was trying to pin down the specific component when playback on deck B went completely distorted, however it does still record. Deck A still play but now seems to have some glitches with the levels dropping and the meter going full on sometimes that requires me to turn the machine on and off.
Looking at the schematic both playback decks go through an TC4053BP multiplexer at the beginning of the playback path so I'm suspecting I somehow damaged that probing the board on deck B but deck A is less affected. However there is some arrangement of transistors beforehand on deck B that I don't understand. My thought it if was a component later on in the chain it would affect both A and B equally hence suspecting this section of the circuit?
So far I started with 1 fault and now have 2 faults! If anyone has any pointers or is able to help me with fault finding that would be grand. I've attached a circuit diagram which hopefully will show ok.
I have access to a DMM and a scope however I'm no expert and have been trying to diagnose the issue. I thought I tracked it down to the bias circuit and could see the bias on the right channel jumping up and down in voltage and was trying to pin down the specific component when playback on deck B went completely distorted, however it does still record. Deck A still play but now seems to have some glitches with the levels dropping and the meter going full on sometimes that requires me to turn the machine on and off.
Looking at the schematic both playback decks go through an TC4053BP multiplexer at the beginning of the playback path so I'm suspecting I somehow damaged that probing the board on deck B but deck A is less affected. However there is some arrangement of transistors beforehand on deck B that I don't understand. My thought it if was a component later on in the chain it would affect both A and B equally hence suspecting this section of the circuit?
So far I started with 1 fault and now have 2 faults! If anyone has any pointers or is able to help me with fault finding that would be grand. I've attached a circuit diagram which hopefully will show ok.
