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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sat 03, 2018 2:15 am 
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Joined: Feb Mon 26, 2018 10:09 pm
Posts: 24
I've attached a pdf of the schematic for this '66 mustang radio. I appreciate all the forum experts taking the time to share knowledge and educate me.

I really want to get the original radio back into the dash. The car is a base 6 cylinder coupe, original and unmolested. Just one repaint in original candy apple red. I want to keep it like a time capsule and just drive it for pleasure and maybe occasional show. I've had much nicer 60s muscle cars in my youth, but this car is just elegant in its simplicity.


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66 mustang radio.pdf [129.79 KiB]
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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sat 03, 2018 2:25 am 
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Okay I've scanned and uploaded the pdf. Seems like it sent okay but please let me know if not.


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sat 03, 2018 2:26 am 
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Joined: Feb Wed 07, 2018 6:52 pm
Posts: 326
Location: Stone Mountain, GA
Those two transistors are powered through a resistor in module K5. It could be open. The modules are a common failure.

Measure resistance between pin 3 and 5, you should get ear 1000 ohms. Also check for 10V on pin 3.

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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sat 03, 2018 2:38 am 
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Location: Indianapolis, IN
Schematic came through fine and would check what Shenion suggested---if the 10V is present and resistance is not, you could cut pin 5 to disable module and connect a 1K (1000 ohm) resistor between pin 3 and pin 5 PCB pads.

Hope that's it !


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sat 03, 2018 2:46 pm 
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Okay, thanks! I'll check it out this weekend and reply.


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sat 03, 2018 3:59 pm 
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Also check c24 for leakage,


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sun 04, 2018 10:02 pm 
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Location: Lakewood, California
Good I agree with suggestions concerning 1 kΩ resistor at pin 3 and 5 of the printed circuit K5. Notice that pin 3 is also the 10 volt source for other parts of the radio. A working 6TPZ does have the indicated voltage on X4 collector and base of X5. I have a working 6TPZ that I can put on the bench for more measurements if necessary.

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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Mon 05, 2018 3:20 am 
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Joined: Oct Mon 26, 2009 10:02 pm
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Location: Indianapolis, IN
Glad you jumped in Meade !

Been out of town, but checking in periodically hoping Dels had success with resistor...

John


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Mon 05, 2018 3:41 am 
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Joined: Feb Mon 26, 2018 10:09 pm
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Well, I'm stuck and really hope someone can help me with the testing recommended in the latest posts. Specifically, the testing of 1 kΩ resistor between pin 3 and 5 of the printed circuit K5.

As confessed earlier, I am not experienced in reading schematics. I do see the subject resistor illustrated there, between points 3 & 5, but need help actually locating it on the board. I do not see a 1 kΩ resistor listed as an item number on the (attached) parts list, so there is no item/balloon with arrow to help point it out on the picture of the board in Sams Photofacts (also attached). I've also attached a photo of the actual board for reference. Can someone help guide me to find the 1 kΩ resistor? In the illustration I see a R13 that is underneath the large can of 3-in-1 capacitor C2 (now replaced with 3 new individual caps) but it's not listed on the parts list. It's stenciled on the board as R3. Is that the 1 kΩ resistor in question?

Once located, do I need to lift one end so it is disconnected from the circuit in order to properly test resistance?

Finally, if all is well, it sounds like I should find 10V at pin 3 of the resistor. I'm not sure how to find pin 3, but I can check to see if there is 10V at one end of the resistor or the other, once I find it!

Thanks to all for the guidance. It's a real learning experience for sure!


Attachments:
partslist1.pdf [144.3 KiB]
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partslist2.pdf [171.2 KiB]
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photofact illustration.jpg
photofact illustration.jpg [ 120.52 KiB | Viewed 879 times ]
my board.jpg
my board.jpg [ 153.5 KiB | Viewed 879 times ]
my board zoom.jpg
my board zoom.jpg [ 151.74 KiB | Viewed 879 times ]
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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Mon 05, 2018 3:51 am 
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Joined: Feb Wed 07, 2018 6:52 pm
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Location: Stone Mountain, GA
The resister is between pins 3 and 5 of K5. It is inside the module.
K5 is right between C23 and R14

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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Mon 05, 2018 4:27 am 
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Okay, duh, now I get it!

I wasn't understanding what the "module" was (obviously) and was looking for a single resistor. The module pins are well labeled and I checked resistance between 3 & 5 at 1K ohm, so not open, that's good!

I repossessed my battery and took the car out for a spin this afternoon, so I will need to get the battery back on the bench tomorrow, check for the 10V at pin 3 and post results.

Thanks!


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Mon 05, 2018 8:32 pm 
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Joined: Feb Mon 26, 2018 10:09 pm
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Okay, I've checked and confirmed that there is 10V on pin #3. That's good. I do not have the skills or equipment to perform leakage testing that was suggested.

Does this narrow-down the amplification problem to the transistors mentioned, X4 & X5, the 1st and 2nd AF Amps?

Thanks everyone!


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Tue 06, 2018 12:10 am 
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Joined: Feb Wed 07, 2018 6:52 pm
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Location: Stone Mountain, GA
If you have 0V on the collector (C) of X4 and near 1 V on the collector of X6 then X4 is shorted.

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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Tue 06, 2018 1:01 am 
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Joined: Feb Mon 26, 2018 10:09 pm
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Okay, that's what I'm seeing. I have ordered a few X4s and should receive them in time to replace next weekend. I'm visualizing success and will post results!

I must say that I'm surprised how easy it is to find replacement components. They're relatively inexpensive too. Nice.

Thanks for all the help!


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sun 11, 2018 2:47 am 
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Okay, I replaced the X4 (identified as the 1st AF amp) and was careful to make connections to correct E, B, C points as labeled on the board. Now I have no stations/volume at all. I had hoped replacing the X4 was the solution but no. Any ideas? I will probably try reinstalling the old one just to see if it still works at low amplification, or if something else is wrong now.

I replaced the original type AR107 NPN using the Sams replacement data showing; Delco DS46 or GE-10 or RCA SK-3020 to aid selection and purchased NTE123AP (listed as a replacement for GE-10 on Talon website). Was this the wrong choice?

Any help greatly appreciated!


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Sun 11, 2018 2:49 am 
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Joined: Feb Mon 26, 2018 10:09 pm
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Forgot to mention, I do still hear the speaker pop a little and feel the cone move when I switch on the radio, so getting power.


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Tue 13, 2018 1:52 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 5467
Location: Indianapolis, IN
What are the voltages at pins of new transistor ? Did you retry old part ?

Just wondered if you damaged a circuit board trace or pad during replacement...

John


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Mar Tue 13, 2018 3:05 am 
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Joined: Feb Mon 26, 2018 10:09 pm
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I will measure voltages at transistor and inspect traces/pads. They seemed okay. I will also repeat the test or resistor between pins 3 & 5 in module K5 and ensure 10V at pin 3. All before I reinstall the old transistor.

Thanks for the reply.


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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Apr Thu 05, 2018 9:07 am 
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Posts: 117
dels, is there a trimmer capacitor to adjust the radio to the antenna, possibly hidden behind the radio's bezel? All the older car radios I've had in cars or used as a shop radio had one, and its adjustment (or misadustment) will have a huge effect on reception. Especially when using alternative antennas and or original antennas not mounted on the car's body. I would look for one and if present tweak it with a nonmetalic adjustment tool. It won't make anything worse and does have the potential to cause reception problems as severe as you describe, Good luck!

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 Post subject: Re: 1966 AM radio repair - mustang
PostPosted: Apr Thu 05, 2018 4:35 pm 
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Joined: Feb Mon 26, 2018 10:09 pm
Posts: 24
Okay thanks. I saw the trim adjust but was afraid to mess with it. Good to know to use a non conductive tool. I've had family from the cold North (MI) visiting for the last few weeks, so had to shelve the project for awhile. I'll post a reply when I've tried a few things that have been suggested.


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