Dash speaker size/ cb radio location

[Ifitaintbroke]

Jim, again, you are correct. S5-1 and s5-2 both go to the dimmer switch. I realize now that each of the mechanical switches are actually 3 switches it the schematic.

I think that 5-1 & 5-2 are actually two legs of a single DPDT switch that simply control whether each digit gets a solid ground connection or if it 'sees' 330ohm to ground.

Another thought. Could it be that the channel switch works, but the display is stuck? I'll have to test it to find out.

I don't think that's possible.

IC 501 is controlling which segments of the display digits light up.

It probably cycles through channels with a momentary switch, and outputs to the display on one side and the crystal oscillator on the other.

(M) prefix makes me think Mitsubishi, but I don't have any of my semiconductor books to look up 58804B anymore.

This schematic doesn't follow convention in switch symbols (buttons v/s toggles) but I suspect S4 as that's the only switch that doesn't seem maintained (arrow in lever)

The channel select button on the left is momentary, correct?

You are correct on Mitsubishi, as some of the components have an M and the "triple triangle" emblem.

And, yes, it is momentary.

Another thing, the mic these radios take has an extra switch that can switch the channel. Basically in use the same as the one on the head unit. On the 23 channel, it works, on the 40, it doesn't. In the schematic it is the four pin mic thing. What I wonder is this: if the switch on the head unit is the problem, wouldn't the mic switch still work? Of course, the only way to know that is to see if they are routed together in the schematic.

Bigger question to me is: what part of the radio ACTUALLY switches between the frequencies?

Bear with me on this, I'm thinking in terms of electrical, not electronic.(I went to school to be an electrician.) I'm pretty used to wiring diagrams, such as the EVTM's, but this is virgin territory for me.

[ArdWrknTrk]

You are correct on Mitsubishi, as some of the components have an M and the "triple triangle" emblem.

And, yes, it is momentary.

Another thing, the mic these radios take has an extra switch that can switch the channel. Basically in use the same as the one on the head unit. On the 23 channel, it works, on the 40, it doesn't. In the schematic it is the four pin mic thing. What I wonder is this: if the switch on the head unit is the problem, wouldn't the mic switch still work? Of course, the only way to know that is to see if they are routed together in the schematic.

Bigger question to me is: what part of the radio ACTUALLY switches between the frequencies?

Bear with me on this, I'm thinking in terms of electrical, not electronic.(I went to school to be an electrician.) I'm pretty used to wiring diagrams, such as the EVTM's, but this is virgin territory for me.

Three diamonds. 💎💎💎.

Yes, I see the lead from just above capacitor 504 at pin 14 runs to the mic jack.

The mic button comes before S4.

So if neither the push button or the microphone button works, it's not the switch.

Either the IC is bad or the leg of pin 14 is broken off.

The XTAL OSC UNIT is the crystal oscillator that determines frequency.

IC501 is the common thing that drives both the tuning and the display.

Look closely at leg 14 (phones have macro cameras now) Is it broken or have a cold solder joint?

If you could look at the package of the chip with a IR camera you might see a hot spot.

 

[Ifitaintbroke]

Three diamonds. 💎💎💎.

Yes, I see the lead from just above capacitor 504 at pin 14 runs to the mic jack.

The mic button comes before S4.

So if neither the push button or the microphone button works, it's not the switch.

Either the IC is bad or the leg of pin 14 is broken off.

The XTAL OSC UNIT is the crystal oscillator that determines frequency.

IC501 is the common thing that drives both the tuning and the display.

Look closely at leg 14 (phones have macro cameras now) Is it broken or have a cold solder joint?

If you could look at the package of the chip with a IR camera you might see a hot spot.

Traced to pin 14, but the problem it that I can't see the circuitry without removing IC501 from the main board, as it is right up against the XTAL OSC. I may just remove it. A good question though, will IC501 be the same for both the 23 and 40, and just the OSC be different? I would think so. If that's the case, all I have to do is swap the IC501 from the 23 to the 40(assuming that's the problem.

[ArdWrknTrk]

Traced to pin 14, but the problem it that I can't see the circuitry without removing IC501 from the main board, as it is right up against the XTAL OSC. I may just remove it. A good question though, will IC501 be the same for both the 23 and 40, and just the OSC be different? I would think so. If that's the case, all I have to do is swap the IC501 from the 23 to the 40(assuming that's the problem.

I honestly can't say.

I wouldn't expect it is given that it would have to control twice as many channels.

Do you have a schematic for the other radio?

Is the chip the same number?

Maybe Bill or Gary have something to offer???

I haven't dealt with this stuff in 40 years.

[Ifitaintbroke]

I honestly can't say.

I wouldn't expect it is given that it would have to control twice as many channels.

Do you have a schematic for the other radio?

Is the chip the same number?

Maybe Bill or Gary have something to offer???

I haven't dealt with this stuff in 40 years.

Well, there's not much point in me going any further. I can't get the board off. No matter what I do, I can't get the old solder off that's holding it to the main board. Not that I'm very good at soldering. As for the schematics, there's only one, and it doesn't specify which it is. That somewhat confirms my belief that the main difference is in the OSC, as it's internal circuitry is not shown, therefore another schematic would not be needed.

[Ifitaintbroke]

I honestly can't say.

I wouldn't expect it is given that it would have to control twice as many channels.

Do you have a schematic for the other radio?

Is the chip the same number?

Maybe Bill or Gary have something to offer???

I haven't dealt with this stuff in 40 years.

And the chip number? Well, I can't read it, because it's on the side facing the OSC. Why did I think this would be a fun and easy introduction to electronics?

I'll get over it.

Maybe I can find someone who can get the board loose. Ironically enough, I soldered the pins back in, and that worked fine.

[Gary Lewis]

And the chip number? Well, I can't read it, because it's on the side facing the OSC. Why did I think this would be a fun and easy introduction to electronics?

I'll get over it.

Maybe I can find someone who can get the board loose. Ironically enough, I soldered the pins back in, and that worked fine.

I'm lost. Have been reading the mail, but have no suggestions.

However, unsoldering integrated circuits isn't easy. It is hard to get every pin de-soldered, even using "solder wick", and you have to have all of them "clean" in order to get the chip out. Plus you don't want to heat the legs very much or you can damage the chip. It isn't easy.

[ArdWrknTrk]

Well, there's not much point in me going any further. I can't get the board off. No matter what I do, I can't get the old solder off that's holding it to the main board. Not that I'm very good at soldering. As for the schematics, there's only one, and it doesn't specify which it is. That somewhat confirms my belief that the main difference is in the OSC, as it's internal circuitry is not shown, therefore another schematic would not be needed.

I got introduced to electronics by bread boarding Forrest Mims projects and desoldering the components on server rack sized boards from DEW Line radar stations. 👴

Gary is right. You need to work quickly and have a deft touch.

 

[ArdWrknTrk]

Well, there's not much point in me going any further. I can't get the board off. No matter what I do.

....... as it's internal circuitry is not shown, therefore another schematic would not be needed.

Depending on how it was soldered on (this is all LONG before RoHS compliant lead free solder) it's best to flux first and then use Goot Wick or similar to pull the solder off the back of the board.

There is no schematic for the millions (now Billions) of gates and junctions etched into silicon.

If you did have all the masks you'd lose your mind, or die of old age before you figured it out.

I often say that when reading even simple schematics like in the EVTM, that [solid state] is like having a map where the whole of Africa is labeled "thar be dragons here!"

But some things can be deduced from what pins connect to what.

[Ifitaintbroke]

Well, there's not much point in me going any further. I can't get the board off. No matter what I do.

....... as it's internal circuitry is not shown, therefore another schematic would not be needed.

Depending on how it was soldered on (this is all LONG before RoHS compliant lead free solder) it's best to flux first and then use Goot Wick or similar to pull the solder off the back of the board.

There is no schematic for the millions (now Billions) of gates and junctions etched into silicon.

If you did have all the masks you'd lose your mind, or die of old age before you figured it out.

I often say that when reading even simple schematics like in the EVTM, that [solid state] is like having a map where the whole of Africa is labeled "thar be dragons here!"

But some things can be deduced from what pins connect to what.

I'm putting this on the back burner for now. I'll try to get back to it soon but my "workweek" is starting tomorrow. I won't be off again till Monday.