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 Post subject: 1978 Dodge Radio Schematic Spkr Impedance Needed, Questions
PostPosted: Dec Fri 22, 2017 5:20 am 
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hello folks.

back in the day, my dad bought a 1978 Dodge Ramcharger, took the utmost care of it, and had it for darn near 30 years. it was his icon throughout the family, friends, work, and neighborhood.

he would always comment (in as many words and such) on 'how the radio will pull in stations from all over the place so clearly and sound so great".

the radio really was a top performer, I must say, and I loved doing daytime and nighttime parking lot "dx'ing" when I was a kid and teenager while mother was shopping.

I walked into a local junk shop the other night and this minty radio was sitting up on a shelf with a $10 price tag on it.

it will be the perfect "gag" gift for my dad since he would always comment on the radio in his Ramcharger. he will be extremely surprised and happy with this gift.

after the holidays, I want to mount it to a custom homemade finished oak shelf type thing with a power supply and speaker under it and mount an antenna to it as well so he can use it (and he will too :lol: ).

in the classifieds, I posted a WTB for the dial lamp assembly that was on the dash light bus.

viewtopic.php?f=15&t=332803

so in the meantime while the holidays pass and and I perhaps find an original dial light assembly, I have a few questions:

1. does anyone know where I can get an original dial light assembly ? is there a "car" forum that I might try ? is there a place on the internet who might have one ? if so, what are they ?

none of the salvage yards around here can help.

2. does it take a "wedge" bulb ? if so, i can solder wires to it, make a "tight-fit" slide in bushing with some heat shrink tubing.

3. what bulb does this radio take ? will any common "wedge" dash bulb from the local auto parts store that is sold now work ?

4. the model number is badly faded and not legible at all. can anyone ID the radio and help out with a schematic/service info for my files ?

5. original speaker impedance ?

the radio works great and pulls in stations extremely well, but I will replace the 5 electrolytic capacitors in it and give it an alignment anyway.

dad is really going to be surprised and love this gift. he will like it even better when I build a mount for it with a speaker and a power supply so he can use it...and he definitely will use it too :D

this here folks is completely unchartered territory for me. I have never worked on a car radio. any help on the bulb type, finding a socket assembly, and any 'heads-up' or tips [if there are any out of the ordinary to help] with the restoration. all thoughts will be greatly appreciated.

thanks,

steve


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Last edited by Dutch Rabbit on Jan Fri 19, 2018 5:50 am, edited 1 time in total.
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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Fri 22, 2017 10:04 am 
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This is a 1978. I've worked with a couple radios of this era, but only a couple, and it has been years ago. Early 70's yes, but not late 70's. I would suspect this radio was either made by Bendix or Philips.

This seems like a really weird place to put a lamp, on the left between the controls. Usually the lamp is mounted on a stem, from the far right, so the lamp itself would sit behind the dial. Typically it's a bayonet bulb, #1893.

You're right, these AM car radios of the 1970's had some very strong tuners. I remember my sister's Duster; in DC I could get WABC New York easily by skip at night, and in my 66 Dodge I could pick it up during the day, but barely audible. That Duster set would pick it up like it was a local station!

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Fri 22, 2017 3:05 pm 
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There may have been a light in that opening to light area around knobs but I'd bet the actual dial lamp is mounted inside behind dial scale... Of course there is possibility there is a light beam director that is lighted by that lamp, but by '78 most dial lamps were buried inside radio...

Bayonet bulbs would have been #1891 or maybe 1893, wedge probably #194, or 161... In later years Chrysler was in love with the miniature wedge #37 bulbs... Anyway all are 14v bulbs and would care less about what they are lighting...

Edit

part numbers per Hollanders interchange

3501766 - '74-'78 2 watt unit
3837190 - '74-'78 4 watt
4048602 -'79-'80
4048862 -'81

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Fri 22, 2017 10:19 pm 
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I have a radio illumination lamp assembly for you if you would like. Your blue-green light diffuser should still be in place behind the faceplate. Let me know if it isn't. PM me.
They are the automotive style wedge-base bulb like a #194 or #168.
I worked at a Chrysler dealer for 30 years and the AM radios were basically throw-aways when customers upgraded their audio. I knew that they would come in useful one day, so I saved a few.
Huntsville also made Chrysler radios, but they were the more premium models like the Quartz-Lock and SearchTune ETRs.
The factory 40-channel CB option is rare and went where the tape deck would go. The CB module was made by Panasonic and was a quality unit. The factory tri-band antennas (AM/FM/CB) with the xmit signal splitter are practically non-exsistant now.
I would park on a hilltop in the evening and listen to a different station every 10 kHz, it seemed. I agree, amazing DX. :D
I also have a couple of the Mopar 3-section 76.5" mast antennas for AM-DX. I put one of them on the Caliber. These were a popular option in rural, hilly country like Appalachia. Google: Mopar 2889934.


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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 4:25 am 
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hi guys,

thanks for the info.

this radio has the light that mounts into the hole as seen in the pic. it goes into a blue "shell" and the dial is illuminated when the light is put into this blue "dome" that is inside the radio.

i had the radio apart already before i wrapped it for dad and there is no way to mount/have a bulb inside the radio.

also, it only illuminates the little dial with no backlight on the knobs, push buttons, or any other lettering on the radio.

wally, pm has been sent.

many thanks for all the bulb specs too. this will certainly help when i make a nice finished "gig" for this radio with a power supply and speaker for dad this winter.

thanks again.

steve

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 4:29 am 
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what would the speaker impedance be ?

4 or 8 ohms ?

thanks.

steve

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 8:37 am 
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Chrysler generally used 8Ω speakers and non-floating grounds in this era.
Non-floating meant that the speaker return circuit (-) could be returned through the common vehicle ground path (body sheetmetal) to the radio chassis in order to complete the speaker circuit.
The higher powered amplifiers in the more premium radios required a floating ground and a dedicated return wire back from the speaker.


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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 1:23 pm 
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Just out of interest, as it is said to be such a good performing radio, is there a link to a schematics? I would like to see what makes it such an exceptional radio.
Also, what is the model number?

All the best for the Holiday Season!

Peter


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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 3:19 pm 
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orbanp wrote:
Just out of interest, as it is said to be such a good performing radio, is there a link to a schematics? I would like to see what makes it such an exceptional radio.
Also, what is the model number?

All the best for the Holiday Season!

Peter

Anything this late will probably be mostly IC, Sams may cover it in their auto radio series...

I doubt it's any better or worse than 99% of other car radios, careful tuning of antenna trimmer cap makes a world of difference...

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 3:38 pm 
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hi guys,

this radio uses two wires to the speaker.

IDK if one automatically goes to the chassis ground, but the wiring to the spkr is two leads and the spkr had two terminals to where the socket pushed to connect.

i replaced the spkr in dad's ramcharger in the early 90's. despite the utmost care that dad took of this vehicle, the speaker dried out around year 15.

as for original impedance, i believe 8 ohm is correct.

jogging the memory...

when i was searching for a replacement speaker in my stash of a few hundred raw ones at that time, 4x10 was one size of which i only had two NOS. they were for the rear deck of early 70's impalas, and they were 16 ohms. it worked fine and the impedance difference was hardly noticeable.

i would have never used a 16 ohm spkr if the original was 4 due to output mismatch and damping factor. the radio really sounded good for what it was and dad did like to 'turn it up' here and there. if it were a 4 ohmer, we would have purchased an original or gone on a quest to find one.

the model number is completely faded. only a few numbers are legible.

would it help if i listed the ones in the middle that are ?

(can't do it now, the radio is wrapped.)

i'd like to see the schema of things as well for this piece.

:arrow: this radio was over the top in sensitivity and selectivity and way above average for the standard "AM car radio".

grandpap had a monster 72 chevy impala. the radio only received the three local stations. for a beautiful loaded car and how well the radio did sound, it was a POS for AM and FM reception.

steve

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 3:54 pm 
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Having owned close to 200 cars in my lifetime, I'd still bet antenna was most of why it was a hot performer... Common for water to enter coax, more or less grounding antenna, that along with mistuned antenna trimmers were the usual reception issues...

The '60s/'70s GM windshield antennas were poor at their best...

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 4:10 pm 
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that '72 chevy impala had one of those "windshield in glass T" antennas in it.

i was too young to be able to remove the radio and adjust the trimmer.

how did those in-glass T shaped windshield antennas perform with a properly calibrated radio ?

pap's was the only one i ever encountered.

steve

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 5:27 pm 
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It's hard to beat a mast (Marconi) antenna for auto radio reception.
The permeability tuning and high stage gains make many car radios a hot DXer when stationary. There is an antenna trimmer to adjust to max gain at 1400 kHz.
There were many different part numbers for matte or glossy black face or silver faceplates. Standard, chrome or woodgrain insert knobs. Non-fader for single speaker or fader for front/rear speaker.
The Chrysler AM radio circuit up until 1983 is discrete transistors, except for U1, the 4 watt? audio output IC.
A typical Mopar part # for a 1982 AM radio w/o fader is 4048861.
I do have a copy of a Sams photofact schematic for a 'typical' Chrysler AM radio. They didn't change much for a few years:
https://i.ebayimg.com/thumbs/images/g/l ... s-l225.jpg
In 1984, the base radio went to a digital AM ETR/clock with different rear panel connectors, but the same mounting ears:
https://ssli.ebayimg.com/images/g/R4QAA ... -l1600.jpg


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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 9:34 pm 
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yes, mine is similar to that one as pictured.

mine is the 'no fader' type and there is no option for a rear speaker.

wally, you have my email. can you send PDF or whatever of the schema of things for this radio ?

if it is hard copy to mail or a payment is necessary, pls let me know.

thanks.

steve

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 10:06 pm 
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Dutch Rabbit wrote:
that '72 chevy impala had one of those "windshield in glass T" antennas in it.

i was too young to be able to remove the radio and adjust the trimmer.

how did those in-glass T shaped windshield antennas perform with a properly calibrated radio ?

pap's was the only one i ever encountered.

steve



Steve,

There's nothing that beats the good old fashioned external antenna on an automobile but there is nothing wrong with the original GM windshield antenna. "Poor at best" couldn't be further from the truth. GM and Delco Radio spent a lot of of time money and research into those before implementing them across various model lines.

My Dad ordered his brand new 1970 Chevelle Malibu coupe with factory am radio and 1970 was the first year of windshield antenna in Chevrolet division vehicles. Like many here I grew up DXing on the radio--like all the early Delcos, a great performer. BTW I still have this car and have been slowly restoring it.

When I restored my Friend's radio in his original 1970 Chevelle SS 396--again with factory windshield antenna --a great performer.

Key being a properly trimmed antenna via the padder cap behind the tuning knob and a properly functioning radio and grounding/electrical system.

Even the later Chevy "square body" trucks continued using windshield antennas.

Your 72 impala used new technology with more integrated modules and a redesigned tuner assembly (started in '71 for the Chevy full-size line). You may have had a bad unit or some new bugs that hadn't been worked out yet. I bet it could have been brought up to snuff with little effort.

The vast majority of issues I have found is with components, not the design itself, even the windshield sealing compound can play a role if it traps moisture and shunts the signal to ground between the connection plate at the base of the windshield and the small lead-in pigtail to the cowl antenna plug.


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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sat 23, 2017 11:05 pm 
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Regarding sensitivity and performance, all car radios are NOT the same! Some definitely outperformed others.

In my opinion, for overall sound quality of an AM radio, I think the late 40's through mid 50's Buicks are hard to beat. They just plain sound good.

Another AM radio that sounds surprisingly good, considering it's a basic radio, is the 1963 Falcon. Simple set, but listen to it.

As for sensitivity, as well as power, there were a couple of dilemmas when switching from tubes to transistors. The first was noise. Transistors made considerably more noise than tubes, which was the biggest reason why many late 50's-early 60's sets were hybrids. Replacing the audio tubes with transistors allowed for elimination of the 250 volt power supply, meaning no expensive transformer and no troublesome vibrator. This greatly reduced the cost of the radio, while making it more reliable. But tubes remained in the front end, for sensitivity sake. When sets became all-transistor in the early 60's, the cost, reliability, and power drain improved again, but the reception went slightly downward. Tune in a weal station on a tube set, and compare it to an early 60's transistor set. The tube set pulls the station out of the air, while the transistor set brings in the station in between the noise. Yes, AVC is a factor, but you can tell the difference. By the 1970's, transistors had improved, and many tuners utilized FET's which improved things even more.

As for antennas, a lot of people complained about the windshield antennas in GM cars. No matter how well designed, such an antenna is not as sensitive as a whip. Remembering that FM at the time was still in the development stages (good FM reception in a car was not easy), people noticed the difference. In modern times GM has again gone back to the windshield (or rear window) but the sensitivity of the radio is enough to overcome whatever loss this provides.

As for 8 ohms, most car speakers have historically been 8 ohms. However, getting rid of that vibrator meant having only 12 volts DC available. The maximum audio signal is 12 volts peak-to-peak without clipping. Do the math, this equates to about 3 watts. If you cut the impedance to 4 ohms you get 6 watts. Stereo you get 12 watts total. Still not great but definitely better. That's why more modern stereos use 4 ohms. Amps can be combined or bridged together, and you can get 24 watts, 44 watts, or whatever -- but when you do this, you can't ground a speaker wire -- it has a DC voltage on it. That's why premium stereos have floating speaker wires.

You can connect an 8 ohm speaker to a 4 ohm radio output and not hurt anything. You just won't get as much power. Chances are you don't even notice the difference. However I would not recommend connecting a 4 ohm speaker to an 8 ohm output. This increases the current drain on those power transistors.

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sun 24, 2017 12:14 am 
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Dr. Radio wrote:
Dutch Rabbit wrote:
that '72 chevy impala had one of those "windshield in glass T" antennas in it.

i was too young to be able to remove the radio and adjust the trimmer.

how did those in-glass T shaped windshield antennas perform with a properly calibrated radio ?

pap's was the only one i ever encountered.

steve



Steve,

There's nothing that beats the good old fashioned external antenna on an automobile but there is nothing wrong with the original GM windshield antenna. "Poor at best" couldn't be further from the truth. GM and Delco Radio spent a lot of of time money and research into those before implementing them across various model lines.

My Dad ordered his brand new 1970 Chevelle Malibu coupe with factory am radio and 1970 was the first year of windshield antenna in Chevrolet division vehicles. Like many here I grew up DXing on the radio--like all the early Delcos, a great performer. BTW I still have this car and have been slowly restoring it.

When I restored my Friend's radio in his original 1970 Chevelle SS 396--again with factory windshield antenna --a great performer.

Maybe I'm a little harsh saying poor but for AM, the WS antennas couldn't touch a whip... In early '70s I used to go down to Nags Head NC on most weekends, at that time there were zero stations in area(Elizabeth City closest)... I knew folks with GM products that mostly listened to their 8-Track as they couldn't get good reception from stations in Norfolk...

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sun 24, 2017 12:53 am 
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there is a lot of good information here, guys.

i appreciate it and i'm sure i speak for others as well.

steve

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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Sun 24, 2017 12:32 pm 
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I seem to have misplaced my Sams for the Chrysler 4048362 AM radio. The attic got badly rearranged. It is in folder AR-290. If anyone has a scan available, I would sure appreciate it.

I have a couple of the mid-'80's Chrysler radios that have the Motorola C-QUAM AM stereo. At night, I could pull in stereo clear-channel stations from 2-3 states away with no problem. I could also hear the 'platform motion' distortion that was cited as one of the disadvantages of C-QUAM.
The Kahn would have been a better AM stereo system, but the FCC let the market (and money) decide the winner out of 4 or 5 AM stereo system contenders. AM stereo made a limited foray into home stereo systems, but not as widely used as automobile audio systems. I don't think that many AM stereo stations still exist around here.
http://www.amstereo.org/history.htm

Last year, I purchased a BST-1 shortwave adapter for the Caliber and upgraded to an RAK radio so I could get the RDS option. The RDS allows the BST-1 to display text on the radio display, like the module version, frequency and signal strength. Otherwise it will provide that information by Morse code over the car speakers which is fun and good code practice. The BST-1 needs an FM radio to work.
Shortwave programming is a lot of religion and politics, but sometimes you can find good music, news or other interesting fare in English.
http://carshortwaveradio.com
http://www.wkjeeps.com/wk_radios.htm#RAK

At home on the bench, a basic AM car radio has little difficulty driving a home stereo 3-way speaker with respectable fidelity.

I also have a couple of Bendix and Delco hybrid AM radios. The tubes are used in the RF and IF stages and the audio output is solid state Germaniums. The tubes run on 12 volts as a 'space charge' tube with no vibrators or step up transformers. The sensitivity is decent. The Delco is in the '62 Lark.
A friend gave me a Stromberg-Carlson hybrid AM car radio with an isolated chassis that can be switched to either positive or negative car grounds. I think that negative car grounds are a standard now. Some say that positive ground cars rusted out too fast, but that may be one of those myths.
http://www.junkbox.com/electronics/lowv ... ubes.shtml

During extended power outages, I run a 12 volt car radio and a small headlamp pointed at the ceiling in the house. Handle car batteries with care and respect. Even with the new sealed batteries, outgassing and some seepage can occur. Keep them in a plastic bucket with good ambient ventilation and away from open flame/ignition. They can be rotated back to the car for charging.


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 Post subject: Re: Late 1970's Dodge Radio Questions
PostPosted: Dec Wed 27, 2017 5:23 am 
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dad absolutely LOVED it and was so very much surprised :!:

one has to love it when they find "that gift" that puts the recipient over the top with excitement, happiness, and surprise.

now, to get a little jig made to mount/display the radio and house a power supply for home use.

I will get the whole 5 or so electrolytic capacitors replaced some wintry Saturday afternoon in the near future.

the jig/box will be a nice spring/summer project.

steve

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