Courier Centurion 40D Restore

[loosecannon]

really nice work 357.
love the look of that radio.

i've never seen a mod like that, and im so curious as to how it all works.
I wonder if it's been documented anywhere.

That cap lead being shorted to the resistor lead could have been one of the biggest headaches a tech can come across.
you could have been spinning your wheels on that for days.
nice find.

I understand your reluctance to get into that PLL section. who knows what they used to cement those "relays" down.
I have been in the same place many times, and if you are like me, you know somewhere in the back of your mind that not doing those caps will haunt you every time you turn it on and wonder how much more stable the radio could be if you had.

My advice is to not be in too much of a hurry to button the whole thing back up just yet.
give yourself a couple of days of not working on the radio, and come back to it with a fresh mind set, and new patience.

I'll bet that you could use an exacto knife and a hell of a lot of time, and get those things loose from the board.
definitely would be the only radio work i planned on doing that day.
that said, i haven't seen what you are looking at in person, and maybe it would be an exercise in futility to mess with that section.

really nice build.
LC

 

[357]

Thanks!!
It was a pain but now its good for another 20 years or so.
The only thing I find is the power supply gets hot as hell, not sure if thats normal or what.

 

[loosecannon]

hmmm...

if you remove the wires that feed all the branch circuits, and just turn the power supply on and let it idle, does it still get hot?

also, which part seems to be getting really hot?
the transformer, the bridge rectifier, or the regulator?
LC

 

[357]

hmmm...

if you remove the wires that feed all the branch circuits, and just turn the power supply on and let it idle, does it still get hot?

also, which part seems to be getting really hot?
the transformer, the bridge rectifier, or the regulator?
LC

the regulator mostly, 50C and the transformer a bit less.
I was running it at 14.10V but it gets too hot for my liking.
The other thing is it pops kinda loud when key-unkeying.
Seems worse after capping.

 

[loosecannon]

well the popping thing is usually to do with speaker contacts being closed before the microphone contacts have opened.
sometimes this is the contacts in the mic itself, (D104's are notorious for this) and sometimes it's the RX/TX relay in the radio.

could it be that you upped the value of a filter capacitor that has to do with the keying circuit and now the contacts aren't closing as fast as they should because the larger value cap is now taking longer to discharge?

this is a complete guess on my part, and i haven't seen this happen before.
just brainstorming.
try keying the radio with no mic attached by using a jumper wire.
that would tell us who the culprit is.

as for the power supply, check the DC voltage at the cathodes of D301 and D302.
If im reading the schematic right they should be either 6.1 or 6.2 volts.
if they are higher, the regulators might run hotter than usual.

If that is ok, then my guess is that there is something going on with that clock switch that switches from clock on to clock off to auto to alarm.
in the schematic, it looks like the DC out of the power supply board runs through this switch, to the AC/DC switch, then on to the board.

maybe try disconnecting the wire going into the switch from the power supply board, and inserting a current meter in series with it, and measure the current draw on receive.
this should only be a few hundred mA with the volume low.

Im only guessing here to give you something to start with, in the hopes that something jumps out at you like dirty switch contacts, or something like that.
Sure wish we had that SAMS. this stuff would be easier.

I have never worked on this kind of chassis before, so anything i come up with is just from staring at the schematic.

good luck,
LC

 

[357]

thanks for the ideas.
I'll check the diodes.
The squelch has a heavy pop when going in and out too.
I remember older radios were like this alot.
I made a video but the camera doesn't seem to pick up the bass of the pop. (3 posts up)

 

[357]

I think I see a issue, maybe the popping.
C108 is supposed to be .01uf and I have a 47uf there...not sure how I botched that.

Sweet Jesus it even looks backwards...pos+ should be to D28

 

[357]

OK is the schematic lying???

 

[357]

I guess my only option is to test a 0.1uf cap "backwards" and note any differences.
Not happy about it

edit*
I pulled the trigger and with a 0.1 cap "backwards, the "pop" at key up and squelch is now eliminated.

more edit*
I tested the points with a voltmeter and the sinkscreen does indicate the + side.
The schematic must be wrong or its a non-polarity situation.

I did screw up putting a 47uf there though.

So squelch is now a very light "pop", super light.
Key up is still clunky but not as bad.
Nature of the beast I think there though

 

[loosecannon]

you can probably get away with a non-polarized cap here.
you did use the AC setting of your voltmeter here right?

This cap is in the audio path and increasing its value will increase the bass response.
within limits that is. you could use a .47uf or a 1uf, but i wouldn't go much past that.
47uf is way too much is is most likely the reason for your popping.

hmm, gonna pat myself on the back for predicting a too large value cap, even though i guessed wrong that it was a filter cap. LOL

sounds like you have it nailed down.

if you want to increase the audio bandwidth, there are more caps to increase and some to decrease in value. let me know if you want me to find out which ones.
LC

 

[357]

I think I'm gonna stay, Bob.

I checked the diodes. D302 17V D301 6V
Also I used DC to check that cap, C108
Can you share the schematic you have?
Mine doesnt show volts.

Thanks again.

 

[loosecannon]

the only schematics i have are the one on cb tricks and the one for the gladiator on the vkham site.
i think ive posted links to both in this thread, let me know if i didn't.

they don't show voltages, i was just figuring that since we are dealing with an audio waveform, that we would want to know which side of the cap had more AC voltage, but maybe that's stinkin thinkin.

either way, sounds like the radio is working!
LC

 

[357]

the only schematics i have are the one on cb tricks and the one for the gladiator on the vkham site.
i think ive posted links to both in this thread, let me know if i didn't.

they don't show voltages, i was just figuring that since we are dealing with an audio waveform, that we would want to know which side of the cap had more AC voltage, but maybe that's stinkin thinkin.

either way, sounds like the radio is working!
LC

Yes defiantly working good.
Power supply still feels hot just in receive mode.
Not sure where D302 is getting 17V from.

 

[357]

This picture you can see the blob that was from the factory, not making a good connection on the pink wire to the regulator.

 

[loosecannon]

i actually did see that earlier and forgot to ask you about it.
i also forgot to get back to you about the power supply.
give me some time and i will try to post back tonight.
LC