Alrighty, update time!
Got my capacitors in today. I opted for nichicon gold caps, and replaced the 4 electrolytics in each of the output sections of radio 1. Screwed it back together, both channels work, and the tone and balance controls both vaguely do what they are supposed to do. I'm not really too worried about that as I'm mainly trying to get them to output audio, not restore them.
Time for radio 2. I desoldered the same electrolytics, replaced them, along with the output amps. Since I don't have an auto bulb handy, and all the stores are being finicky about when they are open, I used the 400mA setting on my meter. Using radio 1 as an example, the power draw is ~360mA. Radio 2 is ~340mA. Seeing as there is no short, I connected power to it and a speaker. No output, no FM stereo indicator.
I checked the voltages on both output amps against what the manual calls, and they were all in the ballpark voltage. Some where a bit higher since I think the manual is using a +12v power source, and I am using a +13.8v source.
Going from there, I checked the voltages on IC1, IC3, and IC4 since they all appear to deal with the FM circuit. Most of the voltages are close, but some are off. Im not sure if that has to do with my power supply, aging parts, or failed parts.
IC1:
4.7(4.4)
2 (1.9)
4 (3.6)
0 (0)
2.76 (2.6)
2 (1.9)
3.66 (3.6)
5.89 (5.8)
3.66 (3.6)
2 (1.9)
8.3 (8)
1.56 (1.2)
2 (1.9)
2 (1.9)
IC3:
0 (0)
0 (0)
5.8 (5.4)
11.8 (10.4)
2.52 (4)
12.14 (10.4)
2.3 (2)
1.27 (1.1)
4.7 (2.2)
IC4:
2.88 (3)
2.93 (3.2)
0 (0)
1.6 (1.6)
2.14 (2.1)
13.5 (12)
10.7 (9.5)
10.8 (9.5)
12.87 (12)
Any thoughts?
Got my capacitors in today. I opted for nichicon gold caps, and replaced the 4 electrolytics in each of the output sections of radio 1. Screwed it back together, both channels work, and the tone and balance controls both vaguely do what they are supposed to do. I'm not really too worried about that as I'm mainly trying to get them to output audio, not restore them.
Time for radio 2. I desoldered the same electrolytics, replaced them, along with the output amps. Since I don't have an auto bulb handy, and all the stores are being finicky about when they are open, I used the 400mA setting on my meter. Using radio 1 as an example, the power draw is ~360mA. Radio 2 is ~340mA. Seeing as there is no short, I connected power to it and a speaker. No output, no FM stereo indicator.
I checked the voltages on both output amps against what the manual calls, and they were all in the ballpark voltage. Some where a bit higher since I think the manual is using a +12v power source, and I am using a +13.8v source.
Going from there, I checked the voltages on IC1, IC3, and IC4 since they all appear to deal with the FM circuit. Most of the voltages are close, but some are off. Im not sure if that has to do with my power supply, aging parts, or failed parts.
IC1:
4.7(4.4)
2 (1.9)
4 (3.6)
0 (0)
2.76 (2.6)
2 (1.9)
3.66 (3.6)
5.89 (5.8)
3.66 (3.6)
2 (1.9)
8.3 (8)
1.56 (1.2)
2 (1.9)
2 (1.9)
IC3:
0 (0)
0 (0)
5.8 (5.4)
11.8 (10.4)
2.52 (4)
12.14 (10.4)
2.3 (2)
1.27 (1.1)
4.7 (2.2)
IC4:
2.88 (3)
2.93 (3.2)
0 (0)
1.6 (1.6)
2.14 (2.1)
13.5 (12)
10.7 (9.5)
10.8 (9.5)
12.87 (12)
Any thoughts?
The balance control should cause full mute of one channel at each end of travel, tone should be smooth changes.
You should have Power lamp PLUS AM lamp Or FM lamp that's before any Stereo lamp, look at wiring on switch S2 (AM/FM switch).
Sounds correct..
You should get a turn on thump in the speakers upon power up, if so you can then probe input pins with a disconneted meter probe and inject hum/buzz to check the amplifiers (vol control at max).
I have found chip amps that static voltage measure ok but don't work.
I don't know if this applies here but some early Toyota car stereos speaker ground went to chassis. This is strange I know but I once had a Toyota "Godzilla" van, (like you see in the Godzilla movies), and it had this set up in it. The speaker grounds where grounded to the chassis. I had never seen that before. Just one wire going to each speaker.
There are several companies that makes modern stereos for vintage cars. Classiccarstereo.com is one place that sells them. They are made in the old form factor like the ones you have but they are modern in every other respect.
Well....if I were to diagnose this, where should I start checking on the controls? The pot that has the tone control is attached to a pcb, and the balance I believe is just screwed to the face since it has the tuner control attached to it.
My apologies for not being clear and concise, the FM and AM lamp do light up when switching between the modes.
Neither radio thumps when it turns on, but I did notice that when I was connecting the speaker to Radio 2 while it was powered on, I was getting that scratchy noise as I was attempting to connect the speaker, if that makes sense. I replaced both chip amps on Radio 2, so I would hope that they aren't dead right out of the package.
To me it seems like the amp chips arent getting an input. Seeing as the amps are getting the input, it looks like I will be needing to use my scope. Where should I start checking, and what should I be looking for?
Wheres the fun in that? They don't look original, nor are they cheap. If I can't fix the second radio, I have a pioneer ke-1818 that I will probably install.
You start by reading and understanding the schematic ffs.
I would expect some kind of click or whump when power is first applied with speakers already correctly/reliably connected.
Touching fingers along amp pins should cause some kind of output.
You can also use a headphone to sniff across the speaker outputs, there should be some kind of low level hiss noise.
You find a $2.00 headphone and use it to 'sniff' line level signal like I said starting with the points A and B marked on the schematic.
The earths marked are important, if open circuit then bal/tone will not work, also maybe amplifiers.
Max.
Reading a schematic isnt like a book. I know what all the components are, but I do not grasp how the components affect the circuit, especially when they have failed, nor how to trace where the signal goes. I appreciate the help you have been giving me so far, but I really dont appreciate the "ffs" part, fyi. If it were that simple to read and understand a complex-to-me schematic, do you think I'd be here asking this many questions that may seem frivolous to you..?
I will check the grounds on both radios tomorrow, and see if I have a spare pair of earbuds laying around. I assume that since I am trying to locate the pre amplified signal, its going to be rather quiet?
Max plank, if you're not going to be civil, go away. People here are learning. They aren't experienced techs. If you don't like my suggestion, report it to a moderator.
You know what the components are and you don't understand what they do ?.
You can't follow a signal line back from the power amp input pin to where that signal comes from ?.
You have been told what to test and how to test and you still don't know if there is line level signal on the tops of the volume control/ends of the balance control ?.
30 mins Googling circuit theory and learning the most basic of electronics and you would understand this circuit from the amplifier input pins back to the line level sources ie the output pins of the AM and FM chips.
The ffs comes from because it seems you have not done at least this self learning part, basic electrics and electronics is simple elementary first step, also you have not completed your first task which is to report what you find with injecting hum/buzz or monitoring with earphones ffs.
Finally Yes, earphones may load source signals down causing low level and maybe also cause distortion but you will hear something from the radio sections.
You need two alligator clips leads, one connecting chassis and the HP plug sleeve, the other lead connecting HP plug tip to probe point in the radio, you will get acoustic output out of one earphone only.
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Correct. It's one thing to know what a component is, its something else to know how it functions in a specific application. Resistors do one thing, capacitors do another, put them together and you got a filter. Capacitors can block DC, or they can act as a short term power buffer with power hungry car setups. Resistors can act as shunts, or bias transistors.
You want me to test something, you need to draw a big circle on the schematic and say "TEST HERE". You assume I know where to test when you say "top of XXXX part" or "Probe this part of the circuit". These parts have a direction to them? What specific part of the circuit do I need to test, with what tool, and what am I specifically looking for? A waveform? A voltage?
No, not really. Learning about RLC parts won't do a whole lot here, and if I could learn everything in 30 minutes needed to fix this radio, mind sharing the link with me and everyone on the forum..?
Again with the ffs. I'm going to echo what Perry said. If you are going to continue to be uncivil, you can leave this post. I can't just absorb the knowledge you have and magically understand everything. We all do things differently, and I apologize that I haven't been following your instructions to the T. This is a learning experience for me trying to fix these radios, and I would like to check things that I think could show a hint as to why its not working before doing what other people suggest.
If you continue to be uncivil, then this forum thread is done, and I will put away the radio for another day. I already have enough projects going on, and with the stress of not finding basic essentials in the store, I don't need a sour forum user adding to it.
Just a small update--
I went to start testing for signal last night using the silhouette of the circuit board in the service manual as a guide, and turns out, aside from the amplifier portion of the circuit, nothing else lines up. The volume / tone control board is different, fm radio section different, etc. I tried measuring the resistance across the pots to see if those were even the same, and they were no where near the 20k ohms that the manuals calls out (they were around 5k? Ill have to measure from the top of the pcb to ensure I am checking the correct points).
I went to start testing for signal last night using the silhouette of the circuit board in the service manual as a guide, and turns out, aside from the amplifier portion of the circuit, nothing else lines up. The volume / tone control board is different, fm radio section different, etc. I tried measuring the resistance across the pots to see if those were even the same, and they were no where near the 20k ohms that the manuals calls out (they were around 5k? Ill have to measure from the top of the pcb to ensure I am checking the correct points).
Are the pots marked for value?
The pots are connected to other components which will skew the readings in the circuit.
The pots are connected to other components which will skew the readings in the circuit.
Again connect a headphone between ground and one end of the balance pot with the bal pot centered, you should have signal of some sort, ditto with the volume pot.....it is not difficult.