A project that I have worked on and off for several years is finally almost finished - My Delco AM Stereo / FM Stereo / Tape Deck / Aux input car stereo converted into a portable (well, kind of, its pretty heavy) radio.
It has a standard 12v barrel adapter input which takes either a standard 12v wall adapter or my 12v/12a LiFePo4 rechargeable battery, a detachable FM dipole antenna, 2x20w speakers, a carrying handle, and an aux. input modded into the front such that when you plug in any 1/8" audio source, it overrides the radio and plays your mp3 player (this mod I did not do, I purchased it this was from an ebay seller who specializes in adding this port to old Delco car radios).
FM reception is, as expected, excellent. Front-end overload is non-existent and the noise floor is very low. Only downside is selectivity - these old Delcos are notorious for extra-wide bandwidth on FM. I considered replacing the ceramic filter with something narrower but it looked like a lot of work.
AM is solid as well. It supports AM stereo reception, and I can actually pick up 2 stations in AM stereo - 890 WLS out of Chicago and 630 CFCO out of Toronto (which plays country music). AM stereo sounds pretty good. Nice thing about the AM Stereo button is that it doubles as a wide/narrow bandwidth selector for all AM station, and in wide mode supports a full 10khz of audio bandwidth.
The speakers sound great as they have full frequency response (the bass hits pretty low on these, at least down to 40 or 50 hz), and the 5-band EQ is very sensitive allowing you to tweak the sound a bunch. The 12v 12ah Lithium Battery I purchased (it was kind of expensive) puts out plenty of juice to power the entire unit.
I plan on eventually building a back panel for this and tidying up the wires (including doing away with the yellow wire caps) but for now everything is hooked up. Only thing I have to figure out how to do is to connect my Terk AM antenna. I had tried it over a 75-300 ohm converter (plugged into the coaxial to Motorla adapter - a piece that was NOT easy to find), but it doesn't work well - I think the converter is the culprit.
Overall I'm very happy with how this came out.
Post a comment
Your Information
(Name and email address are required. Email address will not be displayed with the comment.)
Very nice; if ever I get the electrical chops to do something like this, I'll use a pair of multi-driver 6x9s and then size the case accordingly for some serious thump..
Posted by: StarHalo | January 27, 2014 at 05:54 PM
I love this idea. There are a lot of old car radios available----and I wish I had the know-how to do something like this. It's fantastic.
Posted by: Angelo | January 28, 2014 at 04:47 AM
Nice work, Brandon. What year Delco is this? It looks like the one in our '95 Buick Century.
Posted by: Keith Beesley | January 28, 2014 at 10:09 AM
Its an 89-93 Cadillac Buick model. I replaced the volume and tuning knobs with a black knob that I had from another radio (it came with silver-colored knobs).
The electrical side of this is actually very simple. All you have to do is find the wire adapter for your model, and in my case, each wire was labeled. The speakers consume 4 total wires, I twisted together the constant and ignition powers into one and connected that to the 12v+, the black to ground, and that's pretty much it. I purchased several adapter pieces on ebay for the antenna, used an old pair of rabbit ears, and used some barrel adapters for the battery connections. I had somebody I know do the case for me, and I bought the radio with the aux already installed.
I used my kill-o-watt meter to measure the actual power draw when plugged into the wall. It draws 3.5 watts when powered off (I have no idea why) and about 9 watts on at low volume and up to 17 watts if turned up loud. Overall I should get 10-15 hours per battery charge.
Posted by: Brandon | January 28, 2014 at 12:44 PM
The power draw while off is for clock and/or station memories, that's why most cars lose their radio memories if you disconnect the battery.
Posted by: StarHalo | January 28, 2014 at 09:10 PM
New, just out of beta, Radio Search Engine http://radiosearchengine.com/
Posted by: Tom Welch | January 29, 2014 at 08:19 AM
These are good radios. There was a time when I kept finding them cheap at garage sales, though not recently. I got the first one in 1997, adding a power supply and speakers (eventually descendants of the Radio Shack Minimus-7) and not only is a more than decent receiver for the money for local reception, but it is good for DXing.
I didn't know they did AM stereo, though maybe that's a result of variation. The same receiver board is in one Delco with an LCD readout. One I modded by cutting the audio feed from the receiver board (it's separate from another board that is the synthesizer and audio board) and adding audio input jacks and a switch to select either. I later found one of the cassette versions, minus the cassette mechanism, so I just patched in the external audio to where the tape mechanism fed the audio (I guess there was a tape preamp, either in the radio or on the mechanism, I can't remember) And eventually I traced the antenna, separating am from FM (just one tiny trace) so I could have a proper dipole feeding the FM section. The AM section seemed to be a low impedance winding on a front end tuned circuit.
The FM receiver is the best I've ever had (which may not mean much). No overloading. I never found a problem with the selectivity, indeed assumed it was better than average.
3.5watts does seem a lot. I'm not sure what the display is, but I'm not sure it draws that much. Keeping the memory and time alive uses miniscule current. I did find the green display way too bright at night, so I added a switch to disable it. That's part of the wiring harness, one wire to keep the memory and clock alive, and a separate wire that turns off the display until you turn the ignition (and it gets +12v).
When they were so common (and I wish they still were) the fact that one could find more than one so easily made me think about using a pair as a diversity receiver. Use one and the receiver board from another, the synthesizer from the receiver tuning the second receiver board, then do something with the audio and feed both with different antennas.
I made a couple of bedside radios for people. Took a computer power supply, stripped it out so I was just using the box, and built a quieter linear power supply inside the box, mounting the radio over the box.
Now I'm not finding them, I feel like hoarding what I do have.
Michael
Posted by: Michael Black | February 02, 2014 at 04:36 PM
Michael - thanks for responding, sounds like some interesting mods you did there. I'm intrigued by the idea of tracking down the separate AM and FM antenna inputs internally.
Regarding the clock, I also find it way too bright at night - but since I just use this on battery and don't care about the clock, I simply disconnect the battery.
The lithium battery I'm using, I finally got to put it through a full cycle, and it actually gave me about 12 hours. So it puts out its rated capacity of 144wh. And my charger only takes 3 hours to re-charge it. These are definitely a huge step up from an SLA battery.
Used this for Super Bowl audio and thoroughly impressed all the guests. Halftime filled up the room amazingly well - I think I can say that this radio produces the cleanest sounding audio of any radio I've ever owned - the mids and highs are incredibly clear, and the bass hits quite well. The only radio I have in the same league is my Grundig Satellit 2400.
Posted by: Brandon | February 03, 2014 at 06:30 PM
If I were you, I would install a auxiliary cord to the speakers. That way you can still enjoy the old speakers, but listen to modern music. At this point I would just exchange it for a new stereo though. http://safeandsoundalaska.com
Posted by: Jameel Johnson | May 20, 2014 at 01:12 PM