OKAY I NEED SERVICE MANUAL FOR COURIER CENTURION PLL 40 CH

[357]

OK I think I got a Brown-white stripe wire from L17 on the back of the board.
I get 2.28AMP on SSB.
With mic gain off I can only get it down to 50ma.

Sure wish someone had some hands on with this radio.

50ma should be better than what it was though, it was almost cranked.

***range is 47ma to 75ma with this.

 

[357]

OK setting the bias to 47ma with this method makes the audio sound crunchy with background noise.
I'm at a loss.

 

[loosecannon]

I have seen cans like FT1 before now that i saw the pic. it is a 455khz tuning can that has a 455khz ceramic filter built into it. the realistic DX160 receiver has a can like this.
just tune it like the rest of the 455 cans.


did you actually lift one end of L17 and check the current there?

im not sure what your edit was referring to. did you get different readings upon rechecking?

what you are trying to do is isolate the DC feed to the collector of the final and read the current being drawn when it's "on" but with no power being created.
I am just guessing at this point, but i suppose i would set it for 50mA and get a few radio checks on SSB.

if the comebacks are positive with regard to voice quality, and no one is saying that you sound choppy, then you can leave it there and use the radio for a while on SSB, then check the temperature of the final. if it's just warm you are probably ok.
if it burns your finger, then you probably want to try 40mA, etc...

good luck,
LC

 

[loosecannon]

just saw your last reply.

try setting it at 75mA and see how that sounds, and feels as far as temperature goes.
LC

 

[357]

That brown wire in the picture is the one I lifted to get the ma measurements.
L17 is on the other end of that trace.
I think If I lift that brown wire, I get L17 and L20

 

[357]

35ma plus 20ma is 55ma.
Maybe I should set it to that??

I wish there was a service manual.

 

[loosecannon]

yes, if you just lift the wire, L17 is still connected to other circuits.

Since i'm just guessing at this point, i don't feel like you should go any further with this unless you just want to try stuff.

i will do my best to get ahold of the right SAMS.
LC

 

[loosecannon]

you can still get the SAMS here if you are willing to pay for it:
https://www.samswebsite.com/en/photofact/search/index/model/Centurion_40D
LC

 

[357]

399 sent me this:

The sams says that test point 12 is located at the junction of L16 and L17. It says to open the junction path, and insert a 150ma dc meter. Then adjust RT20 until you get a reading of 35ma.

 

[loosecannon]

cool!
that 399 is a good dude.

let us know how it works out.
LC

 

[loosecannon]

here is a quote from someone who knows alot more about this than i do:

"I remember seeing that "minimum crossover distortion" nonsense back in the day. Pretty meaningless. One way is to listen to the radio on a second receiver. Turn the mike gain down so you only get a half a Watt or so on voice peaks. Now turn the bias pot to zero (in a radio that has one). Slowly advance it while modulating the radio at low power on SSB. It will sound horribly raspy until the trimpot reaches the threshold where you are getting some idle current. The audio quality will improve dramatically at this threshold point. Setting it just above that spot is not a bad way to do it. You run the risk of setting it too high and cooking a final. Less risky to set the driver bias this way, but still not as good as putting a current meter in line with the collector circuit.

Turning the mike gain down for a Watt or less peak output will let you 'hear' that crossover distortion, and also the bias-trimpot setting where it begins to go away. But only if you have a variable control to set it in the first place."

maybe give his method a shot if you aren't getting anywhere.
LC

 

[357]

here is a quote from someone who knows alot more about this than i do:

"I remember seeing that "minimum crossover distortion" nonsense back in the day. Pretty meaningless. One way is to listen to the radio on a second receiver. Turn the mike gain down so you only get a half a Watt or so on voice peaks. Now turn the bias pot to zero (in a radio that has one). Slowly advance it while modulating the radio at low power on SSB. It will sound horribly raspy until the trimpot reaches the threshold where you are getting some idle current. The audio quality will improve dramatically at this threshold point. Setting it just above that spot is not a bad way to do it. You run the risk of setting it too high and cooking a final. Less risky to set the driver bias this way, but still not as good as putting a current meter in line with the collector circuit.

Turning the mike gain down for a Watt or less peak output will let you 'hear' that crossover distortion, and also the bias-trimpot setting where it begins to go away. But only if you have a variable control to set it in the first place."

maybe give his method a shot if you aren't getting anywhere.
LC

Ya I noticed that "crunchy" audio and I set it to where it cleared up.
Maybe I'll get brave and hack into the trace.
You can see it in the picture above, from the brown wire to the next point to the right is where I'd have to cut.
At least I'm out of the danger zone on this.

 

[357]

Wow the simba ssb/2 and the 40D/pll are almost identical.

 

[Adamf]

Hi, does anyone know if RT4 to adjust AM s meter is on the top or bottom of the board? Thanks for any help. Adam

 

[Adamf]

Hi, does anyone know if RT4 to adjust AM s meter is on the top or bottom of the board? Thanks for any help. Adam

All good, I found it. Adam