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Hi guys I have a hktg pushbutton radio. It only has one yellow wire coming from the rear right corner, I was wanting to know if there was any where online that I can get a breakdown or schematics on it. I need to know where the speaker wires hook up and also if there's an earth wire or it earths through the unit mounting. Thanks
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Hello Dan.
The yellow wire is the positive supply, and the chassis of the radio is negative.
The speaker socket is a 1/8" ring and tip mono type connector (sorry, no AM stereo in 1968) located just below the positive wire entry point. The radio has its own circuit and fuse in the fuse block.
The other rear corner of the radio has the antenna socket and antenna trim capacitor.
I don't have a schematic to hand, but if I remember correctly the output stage uses germanium power transistors.
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Thanks, my radio has no wires there but I do see the entry point, I have the top off the radio and there are no wires inside leading to that point, if someone had the top off a radio and took a close up pic I could see where those wires go to and copy, maybe they broke off from a dry solder joint?
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Try kevinchant.com for a schematic.
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Ok Cheers, so I just had a look at another radio I have, does the speaker wire just plug in?
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Yes. The speaker uses a 1/8", (now called 3.5mm) mono ring and tip plug. If you don't have one Jaycar or Altronics should be able to supply it. Just make sure you get the mono type, as the stereo type may kill the radio output stage by short circuiting the output connections.
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Ok so do I need the original speaker or will any speaker work, I've heard with early holden radios you need the correct watt speaker?
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quote:
Originally posted by coupe
Ok so do I need the original speaker or will any speaker work, I've heard with early holden radios you need the correct watt speaker?
It's not a wattage problem, it's the impedance that differs. Most car radios in the 50s & 60s used 15 ohm speakers, including Air Chiefs. These days, 4 ohm is the most commonplace, with some units using 8 ohm speakers. 15 ohm speakers are a rarity. If you connect a modern 4 ohm speaker to an older radio, you will most likely blow the audio output transistors, especially if you enjoy listening to your music at high volume You can overcome this by either running two 8 ohm speakers in series, or using an impedance matching transformer between the radio output & any 4 or 8 ohm speaker. Dr Terry |
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The Air Chief has a label on the bottom that specifies the requirement for a 15 ohm impedance speaker. That particular radio is capable of about 8 fairly distorted watts output, so you will need a speaker that can also handle that power level.
As Dr Terry says, 15 ohms is now an uncommon impedance.
If you want to use the original mounting location, with the speaker shouting out of the dash grille, you will need the original oval shaped speaker, as there is not much room to adapt something else.
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You guys are awesome,thanks heaps
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Speakers in early Holdens were either 9" x 6" or 7" x 5", (depending on which model series) which is generally larger than many of today's speakers.
I have seen 2 smaller speakers fitted in place of the single large one, mounted to the original mounting plate & wired in series. Everything fitted back on the factory mounting holes. This looked to be a very neat solution to the problem.
Dr Terry |
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There's some new on eBay advertised for this mode as a factory replacement, they are 4 ohms 10 watts would this work by itself?
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Ok from what you guys have said is need to run an impedance matching transformer, maybe jaycar will have one
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