Tracking somewhere to Hijack audio - Panasonic RX-ED77

samuelellis

New Member
HI, i just picked up a Panasonic RX-ED77 basically for free. I know its not got the 80's cool but i remember wanting one when they came out due to the look of it.

The problem is apparently like all RX-ED77's the tape decks dont work and from what i can see on this one someone has basically been in and tried badly to fix it. I have missing parts/damaged parts/damaged tape door mech so its not really worth fixing the mech, I have some better tape players.

What i want to do however is add an Aux in so i need somewhere to inject the audio in. I have found a service manual and found a few potential options. Im just curious if anyone has taken one of these apart and has any recommendations

Wire the audio into the tape head input on the board. This is something that may work but am i right in thinking that it will only pass audio if it thinks the tape is playing? Im going to tape apart one of those cassette to cd adaptors from years ago to put its head next to the decks play head to see if it passes audio.

I can see on the wiring diagram it looks like the radio tuner could be on a separate board so I could tap into it there as i assume that once radio is selected it will just pass whatever is on the channels to the amp.

The CD was a possibility but i dont know of this unit has the logic to ignore audio on the cd input unless it knows the cd is spun up and playing

Anyone have any thoughts or does it look like im on the right path with the work ive done so far?
 

goodman

Member (SA)
HI, i just picked up a Panasonic RX-ED77 basically for free.
What i want to do however is add an Aux in so i need somewhere to inject the audio in.
I can see on the wiring diagram it looks like the radio tuner could be on a separate board
so I could tap into it there as i assume that once radio is selected it will just pass whatever is on the channels to the amp.
This is the best option for an aux input.
 

samuelellis

New Member
Thanks, Now i have the unit in pieces I can see the tuner is probably the best input I can tap into. I was able to get to what was left of the tape mech and the previous person who tried to fix it has ruined it so the plan now is to replace where the tape deck is with a touch screen connected to a raspberryPi
 

samuelellis

New Member
TBH im using the Pi, as I have built a few streamers around it and i know it reasonably in and out.

I disconnected the tuner board and connected a line level feed to left, right and ground. I got some audio out of the boombox speakers but it was really quiet and distorted So i attempted to feed the audio into where the tape heads would have connedted - same thing.

I did try the analogue audio in from the cd player but that had zero output so i suspect that is a no go

 

goodman

Member (SA)
Yes, sometimes it's very easy, but sometimes it doesn't work...
I looked at the diagram and in theory it should work.
I don't have that Panasonic, but I found this for you:

All you need to do is find R503 and R403 on the board,
disconnect them from the common point, and feed them an input stereo signal.
Resistors that need to be unsoldered on one side and a cable soldered to them.

open this page in google translate to english:

 

samuelellis

New Member
Thank you, that is really really helpful!

I was starting to get a bit desperate and was looking at soldering direct to the input of the pre amp
 

caution

Member (SA)
Doing it this way disconnects the mic input, not sure if that was obvious or not from the link.
 

samuelellis

New Member
Yes, i tested that last night and it works. I originally discounted the Mic in as it looked like it combined the stereo feed into Mono but these two resistors are further down the chan where it splits it back to a stereo feed

The good news now is i can start on the rest of the work for on this. Like i said i know its not got that 80's cool vibe but hopefully its modifications should be interesting