Dash speaker size/ cb radio location

[Gary Lewis]

You mean something like this?  

It is Smittybilt's Clinometer app and it provides a wealth of info.  I just haven't figured out how to mount the phone somewhere stable yet, but I have a good idea.

[ArdWrknTrk]

I mean I like the novelty of repurposing an aircraft instrument for an off-road rig.

Neither one really has any meaning for me but I find small pleasure in the incongruous (like having a hooded fire control button in the cab of a flatbed)

[Gary Lewis]

Bob’s Bronco could use one - an artificial horizon display, not a hooded fire button. So it wouldn’t be incongruous. But might be quite useful, or at least informative.

[grumpin]

My old 87 4Runner had a clinometer and an altimeter.

[Ifitaintbroke]

I thought about an inclinometer.

[Ifitaintbroke]

Working on the Royces. Both were built in May of 1976. Both are the exact same model. Both look IDENTICAL. But one is a 40 channel, and the other is a 23 channel. Both work, but, the 40 channel is stuck on channel 38, and won't move. The other works fine, but as we all know, 23 channel radios are illegal to use. What I want to do is swap parts from one or the other to make a working 40 channel. At first i thought the channel select switch on the 40 was bad,(which makes sense because it's probably been pushed 539,264,850 times), but, it feels the same as the other, and, looking at it, it doesn't really seem like much can go wrong with it. I don't know anything about electronics, but on observation both units appear to have identical parts-with one exception. The channel indicator panel. Or whatever you call it.
This is the 23 channel.

This is the 40 channel.
What concerns me is this: on the 40, is the switch bad, or the thing that has the channels loaded into it(if that makes sense). Another thought: The components in both units look the same except for the ones in the pictures.
If the FCC's decision to change to the 40 channel system, which became effective in 77', was announced in May of 76', Royce would immediately have to switch production to 40 channel models. It would not make sense to completely redesign the radio. What seems most likely to me it that they only changed the part in my pictures, to keep the assembly lines rolling.
Here's the problem: if that part is bad on the 40, and I swapped in the one from the 23, all I would accomplish is making it a 23 channel radio. So I'm hoping the switch is bad. (Both switches are the same). Here is the switch:


One of them is for selecting the channel, the other is a dimmer. It appears that all they do is let current from one side to the other by means of a sliding contact. If that is the case, all I have to do to test it is to test for continuity when the switch is pressed.

[Ifitaintbroke]

Schematic:

Can't find the selector switch in it.

Another thought:
As I've said, I don't know anything about electronics, but usually if a board is bad it's obvious by burn marks right? Can one go bad with any obvious sign?

[ArdWrknTrk]

I'm trying to read this on my phone, but I would say what are the two switches directly above transistor Q501(?) on the left side?
You say "one is a dimmer". What does it dim? The display? An indicator lamp?
They both go to the IC header and switch between direct and through a resistor, it seems.
(again, my eyes are not so good anymore and I'm looking at a sub6" screen)

Circuit boards can definitely fail without scorches.
IC's can fail internally, sometimes a resistor, transistor or diode will fail open without showing on the package.
Often the best way to detect a fault without a logic probe is to look with an infrared camera.

[Ifitaintbroke]

It controls the channel display.

[Ifitaintbroke]

https://cbtricks.org/radios/royce/1_610/graphics/royce_1_610_om_ser1_sch.jpg

[Ifitaintbroke]

Jim, you are correct. R519 and R520 both go to the switches. I'll have to look up their specified resistance, and check them. I would much rather it be something simple like that. One unit is completely functional, so, if that is the problem, I should be able to take one from the 23, and put it in the 40. Also, can you explain the infrared? What would I be looking for?

[Ifitaintbroke]

Looked it up, and, if I'm reading it correctly, they should be 330 ohms. Will test tomorrow.

[ArdWrknTrk]

The link is a little clearer but I'm still zoomed WAY in and can only see a fragment at a time on my phone.

S51 & S52 are the dimmers for each of the two digits (7 segment displays, FGABCDE) probably a DPDT* switch.

S14 (to the right of Q501) would pull pin 16 of IC 105 to ground.
I suspect this is what causes channel shift and the displays to change.

[ArdWrknTrk]

Ifitaintbroke wrote

Also, can you explain the infrared? What would I be looking for?

 With an iR camera you can see hotspots on the board.
Some things (like a resistor that's sinking lots of current) are naturally going to be hot but if you see a hot spot inside an IC or some other component that's overheated it's a good clue there's a failure.

Sometimes you can even feel it with the back of your hand.
I haven't done much troubleshooting at the component level since I was a kid (about when these radios were made)

[BigBrother-84]

Gary Lewis wrote

You mean something like this?  

It is Smittybilt's Clinometer app and it provides a wealth of info.  I just haven't figured out how to mount the phone somewhere stable yet, but I have a good idea.

🤣

[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.

[Ifitaintbroke]

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

[Ifitaintbroke]

Went thru all the trouble to look up and decode the resistors, then realized that the schematic lists the ohm rating right next to the resistors.

[ArdWrknTrk]

Ifitaintbroke wrote

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.

Ifitaintbroke wrote

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?

[ArdWrknTrk]

When I was six I could read resistors at a glance and bin them in my sleep.  

Now they're specks the size of coarse ground pepper surface mounted on multilayered boards.
'Times change'...