Adding MPX out to the R3

[CJVx]

I would like to add a multiplex output from the R3 chassis so I can run it to a standalone multiplex unit (Eico MX99$ into my integrated amplifier. I read a very old article a while ago about performing this basic task, but I can't seem to find it anymore. Where would I attach the output and also I'm assuming I would need some sort of coupling capacitor. Can anybody point me in the right direction? Thanks

 

[dcgillespie]

If you've got a schematic, we can show you.

Dave

 

[larryderouin]

Dave; Check your Email. Manual sent for the R-3. You'll recognize it.

Larry

 

[dcgillespie]

Thanks Larry -- I looked back in my files and noted where you had already sent it to me once before.

CJ -- The multiplex take off point will be at the junction of where R27, R28, C30, C31, and C33 all join together. At that point, attach one lead of a .05 uF (or .047 uF ) preferably ceramic cap. If not ceramic, then a small, low voltage mylar cap. The point is to keep the cap physically small so as to not have a large surface area cap that would act to bleed off the upper side bands of the stereo difference signal. No big boutique caps here please. The other lead of this cap will be the multiplex take off point to your adapter. Keep the interconnect between the new MPX output of the R3 and your MPX adapter as short as possible, and in no case longer than 3 feet.

While you will in fact get reasonable FM Stereo MPX performance from this arrangement (assuming your MPX adapter is up to snuff), you won't get the very best performance due to the restricted bandwidth of the IF "strip" in the R3. Still, it should be a very worthwhile effort to perform.

Let us know how it turns out!

Dave

 

[CJVx]

Great thanks for the info! Will work on this during the week and post a video when it all works out.

 

[CJVx]

Success! Working really well it seems. Added the MPX tap right where Dave stated, shown in the picture, the blue cap being the .047, tried to keep it small.

 

[dcgillespie]

Great job! Glad it work out so well for you!

Dave

 

[larryderouin]

CJVx; How about some pictures of your Coronet. From the video it looks like the cabinet is possibly a Warwick, so the Model # would be WR-11 if it is. Also can you get the Serial # off the main chassis (on the FISHER Sticker on the back), and get a picture and information off the speaker. In the case of a JENSEN DoubleHump, the info is stamped on the perimeter of the frame. Should be a G-510 or H-510. If it's a Stephens Tru-Sonic, the info will be on a tag on the magnet housing or cover.

I've got a '51Coronet in the Warwick cabinet. Serial 6873.

 

[CJVx]

Hey Larry, this my other thread.

http://audiokarma.org/forums/index.php?threads/1951-fisher-coronet-warwick-console-new-to-me.805187/

 

[larryderouin]

DAMN! I forgot all about that one. The memory is definitely going faster than another part.