Hello All.....
So I need some help with my 68-72 U69 7303211 Radio. Specifically, Connecting it correctly. Many of the connections are obious (like the amphenol type connector from radio to 7311911 amp, but there are 2 wires coming out of the amp (black and green with crimp on connectors ,gorund and hot. what do they connect to ? (Pic 2)

next the speaker connector is gone just baare wires so I assume they got to the 2 speaker wire connectors coming out of radio. (pic #7)

why are these wires bare or crimp on ?

Last, its mono so where is correct place for speaker to be mounted ?

 

That is a STEREO radio. The speakers were mounted in the kick panels, those are not the correct speakers

 

thx Ralph the wires coming out of the amp (green and black are leads from the coil on back of amp and there are only two wires going to the speaker connector on radio

i understood that if it was stereo there would be 3 wires in that connector

 

11VFM1
1 =1971 model year
1 = Chevrolet
V = Corvette
FM = AM/FM Stereo
1 = revision #1

 

What year C3 are you installing this into? For '72 that is the correct 4"x6" dash speaker design - on the right and left, mounted to the bottom side of the upper dash pad. There were no kick panel speakers for either the mono or stereo -- from what I've seen on my car and the '72 AIM. You might consider the radio & speaker harnesses from LectricLimited to get you back to square-one.

I'm stumped as to what the black rectangular box with bright red patch is... that's not factory to my knowledge.

 

Hey Jim,
The head unit in your pics is the U79 not the U69, so Ralph and Fred are both correct, that the 11VFM1 is a stereo unit. This tiny window lights up "STEREO" when you're tuned into a strong FM station.




And yes, the Red/Black box is definitely not part of the original system.


This is a U69 Mono system.


Also, 67:72 is correct, those are the right speakers for the original dash mount system.



Cheers, Greg

 

68 & 69 had the speakers in the kick panels poster has a 1968 also the ***** are not correct for a 68

 

Okay.. Lots of comments,First thank you all for taking your valuable time to help me. But come on Guy's the radio can not be both mono and stereo.... So which is it ?
I bought this for my 68 convertible, I know it is not "Correct" only to be used while I send original radio still in car out for rebuild.
My convector has only 1 transistor . telling me it's mono. FYI there were two versions of this radio mono and stereo
I do not understand what the Large box (Amp 7311911 ? is for see pic #2)

the black/red box is an aftermarket auxilliary antena so you can test radio on bench

Thanks
Jim

 

The other large piece with the black cable of wires is part of the STEREO radio You have a STEREO radio from a 1971 Corvette It is a rare radio 3,431 Corvettes were ordered with that option in 1971

 

Okay Ralph, thank you for your insight. would you have acess to a wiring or connection diagram.. ? if it is stereo then something is wrong with my speaker wiring. wires coming out of the amp 7311911 green and black connect to a coil must be for power. only other connection coming out is the multi pin amphenol style going to radio.
can I assume I need a wiring harness for the speaker leads coming out of radio ? only 2 wires coming out so how do I connect the 2 strereo speakers (look at pic #7 also how can it be stereo with only 1 transistor on the convector ?

 

Jim_A let me help clear up some confusion and misinformation.

As previously stated, your receiver is a 1971 Stereo unit.

The box with the heat sink and one power transistor with the tag 01VMPH1 is your Stereo Multiplex adapter, required for stereo service.


01VMPH1
0 =1971 model year
1 = Chevrolet
V = Corvette
MPH = Multiplex adapter
1 = revision #1

In addition, you have separate heat sink with a power transistor (AKA convector). This single power transistor convector is shared with all Mono radios. You have two power transistors total.



You have everything connected properly, as indicated by the green circles.


The red arrows/circles indicate the green wire and black wire for the speakers. The pair of green and black wires from the Multiplex adapter feeds one speaker, the other pair from the receiver feeds the other speaker. A previous owner cut the speaker wiring and added the red spade terminals. In addition, you have the proper 10 ohm speakers required for this radio. They are 4X6 dash speakers, not the 4X10 kick panel speakers correct for your '68. Use only 10 ohm speakers with this radio. I hope this helps.

 

Guy, thanks for the clarification.
The info I posted on the convector is not correct. I see the multiplex has the other transistor for this "stereo" system.

 

 

Ahhhh.... the light begins to shine.. I see how it works now. Thank you all for your help

One more question, To connect power for bench test this radio, I can use a 12v DC supply, power plug has 3 wires Pos Neg and brakelight, Do I need to connect the pos and lamp wires to +12 and the ground to ground ?

Ralph, Where did you source the manual ?

 

Manual was from an old Delco radio repair shop near me that closed up about 40 years ago

 

You appear to have a 1968 ONLY stereo radio, rather than a mono U69 radio. The '68 stereo system had a radio head unit AND a separate multiplex unit, AND the head unit (if I am not mistaken) had a convector device which was the final stage of amplification for the head unit. (The multiplex unit had its own final stage of amplification.) The stereo system for the '69-74 cars (I believe) had a head unit and a dual-transistor convector ONLY.

It will be a challenge to install the '68 stereo system into your later vinatge C3. I'm sure it can be done; but it will be difficult to find the room necessary. Your best bet (if you still want to install that unit) would be to purchase a copy of the 1968 AIM...or ask for someone to send you a copy of the stereo option pages from their's....so you can see how that unit was installed in '68.

But, back to your question: After installing the head unit, the multiplex unit and the single transistor convector, the pigtail from the multiplexer is plugged into the head unit: the cable from the convector is connect to the socket in the back of the head unit: the black and green wires from the convector go to the right side speaker (green +; black -) on the speaker terminals; the green and black wires from the multiplex unit go to the left side speaker. It is important the the speakers are IN PHASE. This means that the green wires go to the terminal that is painted (should be the same on both dash speakers).

P.S. A really good upgrade to your system is to ADD speakers in the kickpanel areas under the dash. KEEP the dash speakers where they are, but maybe upgrade them to better quality (IF you want to do the upgrade). If you decide to do this, purchase new 4 ohm, 4x6" speakers for the dash (30 watts or better is enough for that head unit; do NOT buy high wattage speakers!). Also purchase 4 ohm speaker for the kickpanels. two-way speakers (mid/woofer) are best, as the dash speaker provide the high frequencies. Then wire each pair of speakers (left and right side) in SERIES. This will provide speaker impedance of 8 ohms to each side of the system. It is designed for 10 ohm impedance, but 8 ohms will work fine with no problem...even at full volume. Less than 8 ohm speaker impedance is too little for the GM radio system.

This mod makes a WORLD of difference in the sound quality of the stock radio system. Good luck with the change.

 

Charley, you're pretty well versed in these radios.
I'm reading Jim's Service Model Number 01VMPH1 as 1970, Chevrolet, Stereo Multiplex Adapter, Revision 1
Does that sound correct to you?

 

From what I see you have a 71 Stereo radio. Here are a few pics from my 69 radio to give you some info. The 9 in the 91VFM1 means 1969. The back of the radio shows what the wires coming out of the radio should look like. The picture of the pass side of the dash shows how they mount. The drawing is something I found on the internet showing all wire connections. There are three wires on the power connector, BLACK is ground, YELLOW is power for the radio and GREY is power for the light. The speakers must be 10-ohm and since this is a 71 radio the speakers mount up under the dash and the one appears to be the correct size. In 69 they used a 10-ohm 4x10 speakers in the kick panels.

 

Did you mean dash light? I have see that feature on some older radios.