Note about the use of glue and epoxy. The glue (contact cement) is used for the outer edge of the spider cup and paper cone edges where it bonds to the metal speaker frame and for the outer gasket on top the paper cone and partially onto the metal frame. Do not apply it like "contact cement" use it like you would white glue, just smear it on, and stick parts together. It will work that way just fine and is how the speaker repair shops do it.
The Epoxy is used everywhere else, voice coil to spider, voice coil to cone, lead wires, dust cap. I like using a small screw driver to dab the epoxy into the various places it needs to go.
The standard 6x9 voice coils come with prepunched holed for the lead wires, these are always too far up the cone walls for old speakers. I patch these factory holes with a tiny circle of black paper, and i make new holes about an inch or so from the voice coil. The lead wires should be allowed to cure in place with the epoxy before you place the service loops and solder them to the terminals on the back side.
The dust cap is the last part to go on, you can and perhaps should test the speaker before gluing the dust cap in place.
Don't forget you need to supply the field coil with DC when you test this speaker, if you don't it barely makes a peep. I used a bluetooth demo kit that contains a powerful class D speaker driver for testing purposes. Then I can play all the terrible music i keep on my iPhone to break it in -stan
hi truckernix, the coil is about 4 ohms cold, so with good wires from 6.3V it would be about 1.5 - 1.6 amps in theory. my power supply shows 1.34 amps but i'm likely suffering from a lot of extra lead resistance in those skinny wires and the alligator clips.
if your generator is running well and the truck is at about 7.2V then the coil would be linear in that range and should go up to about 1.8 amps.
The specification for the radio is 6.5 amps max @ 6.0V input, which includes the speaker. That makes sense from what i recall with the last one i fixed up, radio - speaker was in the 4.x amps. -s
I do not yet have a full set of usable original buttons and knobs, and I prefer not to mix and match original and reproductions so i'm going to use all 3D printed buttons and knobs for now.
My 3D buttons are a bit elaborate, they consist of machined brass parts that are epoxied into the plastics, all employ a set screw to lock in place. I didn't come up with the 3D printing design myself, I traded circuit design time with a friend who printed these buttons and knobs, i should have the files somewhere if we need to dig it up for future use. The tone control knob has a minor mistake, there was a 90 degree rotation for the metal insert, so i needed to tweak the knob to accept the insert clocked by 90. The fine detail of the tone knob steel insert needed to be finished up by hand with jewelers files, it must grab the outer control shaft without squeezing it too much.
Once the buttons are assembled they are sanded and washed before paint. I allow the water to dry over night, the 3D printed plastic seems to be slightly porous and i don't want water messing up the paint. The buttons and knobs will be painted the same color as the Dial backplates (Rust-oleum 7771 SAND). I find that Rust-oleum paint is quite durable for contact surfaces that need to be touched daily as long as the paint is allowed to dry for a full month or more before being put into service. There are some paints intended specifically for plastic surfaces that may do better in this application, however I didn't want to buy a new can of something that didn't match the dial face perfectly.
A while ago I had an update on painting the dial back plates. The parts have had plenty of time for the paint to cure, now they won't be nearly as delicate to damage. Attached are some cross section drawing to show how these parts fit together and which colors are used on the various surfaces of the dial face parts.
Assembling the escutcheon is fairly straight forward if you are the person who took it apart and remember how all the parts go together. If you haven't seen one assembled, the details are not very clear in the documentation. Best to pay attention and take photos when you disassemble your first one. Escutcheon parts photo left to right: Assembly main body plastic, Dial, Dial Backplate - Upper, Dial Backplate - Lower, Steel Button Surround Insert
The tiny round head screws that hold the Dial Backplate Upper and Lower are machine thread into copper. These tiny screws don't use any washers, they are friction fit into the copper dial parts. The round heads are not the best option for use on plastic, but based on taking 3 of these apart now, these tiny screws appear to be original.
The larger 6-32 screws that hold the button surround are flat head style, these will try to spread the plastic if they are too tight, but that's original as well so it's going back in too.
short update, Installing escutcheon and push buttons onto the tuner unit.
Original style press on push buttons could go on anytime, but since mine lock with a set screw they must go on before the escutcheon, which means they have to go on before the tuner unit is installed into the main housing. This also means that once my radio is in the truck, if i want to remove a push button, the radio has to come out and be disassembled. This situation is not ideal, but it is something i'm ready to live with for my home made push buttons.
The backplate pointer goes onto the tuner unit first. Next my home made push buttons install from left to right. Finally the escutcheon slides over the buttons and screws into place.
Warning: When removing the escutcheon assembly from the tuner unit, remove only the two Escutcheon screws and pull it straight off. The Backplate pointer must remain screwed to the tuner unit. Never unscrew both the Backplate Pointer and the Escutcheon assembly simultaneously. The Backplate Pointer is sufficiently tight into the Escutcheon that the two will want to travel as one, this order would seriously risks breaking off the pointer.
Now all the internals are ready to test fit into the housing. I could wait to affix the labels until after the test fit, but i think it will be okay to do it now. This post will be two parts so that i can post more photos again to show the history of reproducing the labels.
I took good photos of the label remnants on a couple of these radios and redrew them on the computer. My process starts with taking clear straight facing photos with a ruler for scale. I used the program Omnigraffle which is not nearly as powerful as photoshop but is suitable for this task. Once in the computer i can resize the image to it's native size using the ruler in the photo against the ruler in the editor. Then i go online and start researching the fonts until i have all the right characters i need to retype the label. These labels required over a half dozen fonts to create. Any graphics an icons i redraw as necessary. Once the drawing is completed i group them together and make it a 1:1 PDF for printing purposes.
Also while having fun drawing in the computer I tested my artistic skill by making a label placement drawing I decided it would be best to document the locations as fewer and fewer radios have the labels intact as time goes on. The labels were at the same locations on the two units that had label residue, so that appears to be consistent and original.
The attached drawings are not a PDF, they won't print very well, if you want the PDF to print proper i will send it to anyone who asks, just PM me with an email address.
Once the PDF is ready to print 1:1 i went to the local Staples and perused the paper options.
The paper stock used for the original labels is semi gloss and thicker than your average paper. I found that Xerox Digital Elite Gloss 80 lbs. had a nice weight and shine to it and was very comparable to the original labels so for $1.19 that's what I got. Staples has an in-store email to send files to for printing, so i was able to conveniently transfer the PDF from my phone to the store and have it printed without issue. Make sure to ask for a ruler and measure the sizing bars on the printout to ensure it's the right size.
Back at home cut out the new labels and use white glue on the back to stick them in place.
To finish off the housing the serial number tag gets riveted back into place ensuring it's the same way up as original and now everything is ready for assembly fit check.
Again, If anyone wants a copy of any of my PDFs PM me.
Time to test fit the parts into the housing before alignment. I like to make sure all the wires are correctly routed and a good length because I don't want to do any soldering after the alignment procedure.
The spark plate and tuner unit fit well as expected. The chassis wires have to be crossed over in a specific pattern when the chassis is connected to the tuner unit. This step involves looking at the disassembly photos carefully and reproducing those wire placements. The wires will un-twist and be in their original locations when the chassis is rotated for installation. Some of the big ground braids require a propane torch to get enough heat to solder well. I find it useful to mask off the area to solder with some tin foil to protect parts and wires from the heat of the torch.
Once the chassis was installed I found a couple issues. Issue 1 I could really use an extra inch or two on the tone control wires. The tone wires are the gently twisted green and blue pair that go the long way around the tuner unit. These wires originally did not have to cut the corner behind the tuner unit as in my photo. Issue 2 A terminal on the speaker is crashing into the chassis. I will have to reproducing the magnificent factory bend that was present on the speaker terminal when I removed it. I thought the terminal was an accidental deformation, turns out it is required to clear the chassis.
The guts of the radio will be removed to have the issues addressed and will be aligned outside of the housing for easier access to the ferrite cores. In theory the best alignment would be done with all in the housing, but that seems like a tight fit and aligning it while apart seemed to work alright on the last one i did.
project update Today will be two posts to fit more photos. Almost complete!
I Resolved the few minor issues found in the test fit. Increased the Tone wires by a couple inches and the tuning clutch was a bit looser than i liked, it measured 0.022 at open, i reduced that to about 0.018 and it feels better.
I like using old rusty tubes that i don't care about for the initial power up and DC checks. I get the fancy glass tubes with GM Genuine Part markings once i know the radio won't burn any out. Some of the old tubes had some rusting on the metal base, soaking them in evaporust and rinsing them off with alcohol got them looking good.
The initial power up test revealed excessive current draw which i traced to the speaker wiring, I wired up the plug "top view" by accident, my notes were written with "bottom view" pinout. Fortunately this error didn't cause any permanent damage and was an easy fix.
The alignment procedure was a bit more painstaking because I didn't have my AM signal generator in California. To do the alignment i used a simple function generator outputting a pure sine wave at the specified frequency. Then instead of looking at the demodulated tone at the 6V6 i check the carrier or IF with an oscilloscope.
Before the unit is aligned it will (should) pick up radio stations and sound reasonable, however you may notice that the unit is more sensitive and picks up the weak stations better post alignment; for this particular radio it was very noticeable, the AM band had more usable station after it was aligned.