So I have been slowly getting the truck back to perfect fixing what others have done and even taken it to its first show.

I decided to get the radio rewired up and with new Sony xplod 5x7 car speakers wired up and the antenna connected, only the lamp came on. There was no hum or buzz just nothing so upon opening it up it looks like original 50 and 500 uf caps. I will replace those in hopes that that fixes the issue but what else might i be looking at needing to replace?

 

High value (like 1 meg or higher) resistors tend to drift way high over time. Check or replace. I would want to clean all the connections and volume pot, tuning cap, etc with solvent thoroughly. WD40 actually works for this and is favored by the pros. De-Oxit is good stuff too. Although a professional alignment is probably overkill for this, if you know somebody who can touch up the IF and RF alignment it really makes a big difference in sensitivity and selectivity. Lastly, peak the antenna trimmer on a weak station around 1400kHz once installed for best performance.

 

Probably a Bendix 6TBT AM Radio


The output AMP (transistor Q6) is expecting an 8 ohm load from the speakers. If not the correct load it doesn't take real long to burn out the AMP.


Otherwise, the voltage at test point 1 should be 10.8V (emitter of Q6), test point 15 should be 10.6V (base of Q6) and the collector of Q6 should be 1.8V. If the DC bias voltages aren't correct going to this transistor you'll have to work backwards through Q5 and Q4 which make up the audio frequency (AF) AMP.


The only resistor over 1M that I can see is R31 with a nominal value of 3.9M, may vary.


Capacitor C2 is 500 uf 2V
Capacitor C3 is 50 uf 3v


The input and output IF tuners are tuned to 262.5KC.


The lamp comes on so you know your fuse is good. Voltages should be present so you can start troubleshooting from there. I could recommend a schematic if you want to dig into it further.

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This might also be good reading. I'd never heard of using it on electronics and it didn't sound right to me. (Certified Electronics Technician). If you want to do so, go ahead.


https://answers.yahoo.com/question/i...8013301AAtL89L


Now, if this is the product being used from WD40 then I can see it, but not the normal oil product we have known and loved for decades.


http://www.wd40specialist.com/products/contact-cleaner/


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Yes, I would agree, don't use it on your laptop fan, as the website linked alludes to.

But then, we're talking about something completely different. It is true the cork sniffers get all bent out of shape whenever they hear "WD40" but the truth is, it works great for old school volume controls. For decades. It is basically Kerosene in a can. Guess what the old school radio guys used to clean tuning caps, chassis, etc? Uh-huh.

What do you suppose, btw, is in the modern "approved" by-certified-electronics-repair-technicians electronics cleaners anyway? (Since Freon and Csrbon Tet have been banned) Surprise! Solvents like Naptha, Kerosene, etc. MSDS tells the tale.

 

I find good old WD-40 attracts dust and dirt to itself and I have not found it to be a good choice for my electronics work. Potentiometers seem to get gummed up when I use it. But, whatever works for you is fine by me.


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I'll take the schematic for the radio if you have a link to one and get a update back when i replace the two caps.

Now you say it expects a 8ohm load but as far as i know no car speaker system uses that. Only 4 ohms, i recently put kickers in my 64 Galaxie with the stock radio, a redi rad, and just the one 4 ohm speaker. It would have blown as well right? I can't really find any 8 ohm 5x7 car speakers if it really wants that much load.

 

"I'd never heard of it being used on electronics"

and

"I find that it gums up in potentiometers"

So which is it? Anyway it works great. I'm not making this up, lots of pros really do use it on pots and have for decades.

 

I was just suggesting a schematic if you want to dig in further. They are on eBay.


I'm not saying it expects an 8 ohm load, the schematics and specs do say it expects an 8 ohm load. Normally a 4 ohm load isn't adequate if they specify 8 ohm, but 4 ohm is better than no load at all.


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I often don't use complete sentences.


I'd never heard of it officially being used on electronics. I have used it and find it gums up stuff for me. Results vary. Most of all, have fun doing it!


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Leaves a gummy residue? Well, so what? Don't let the perfect get in the way of the good. It's not like anyone is going to be looking inside the pots?

The pots already have dust and crap in them, that's why they get scratchy and noisy in the first place.

 

OK, Ted. Have a good one...


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If anyone else is interested here's a much better link. Sort of beating a dead horse, but better than shooting a famous lion, I guess.

Safe to use WD40 as switch or potentiometer cleaner? | Electronics Forums


Also, here's a short video I just uploaded showing the waveform of Creedence on the AM radio.




Enjoy!


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Jeez Louise! LOL

I read the link provided and as explained earlier, some folks just can't abide by it, and immediately wigg out but offer nothing substantial by way of rebuttal other than it "leaves a residue". Interestingly several people allowed it's just fine for the purpose. I suspect the "redneck" bias may be at work with some. A different label, and high price would fix 'em right up.

For our purposes here - cleaning a potentiometer - a light lube or residue is precisely what is wanted. There some other "special" ingredients in contact cleaners - but they are 99% petroleum solvents, such as lighter fluid. Kerosene has been used to clean pots for going on 100 years, there may be "better" things to use, but what's more likely to be on the shelf??

In fact that's why I mentioned it in the first place. Most people will have WD40 on the shelf, at least before any fancy contact cleaners, and they aren't making a career out of radio repair, they just want the scratchy volume control to go bye. It's works great, does no harm and is cheap. I'm really at a loss here why anyone would make an issue out of it, frankly. We're here to help people at FTE for one thing. I wouldn't steer ya wrong.