Uniden Washington Modulation?

[sp5it]

How do you turn up the modulation on this radio?

By connecting oscilloscope to dummy load connected to the radio. Inject audio signal of 1KHz at 30mV to Mic input. Than adjust AMC to 98%. Done.

For AM modulation, you can clip R104, this is your AMC.

Butcher mod? C'mon why you want to thrash nice radio?

 

[Eastside]

Got to be your meter or the leads if you key the mic and you aren't seeing any current/mA's on the meter . . .

**EDIT**
Check the fuses inside your meter! The fuse protects against over-current use. The rest of the meter may function fine; but in mA mode with a blown fuse, it won't read. Been there; done that. Bet that is it!

You may be right...where would you buy one of those tiny fuses?
its paper covered so you cannot tell if its blown?

 

[Grinder74]

On my DMM I have to insert my lead in the mA jack.

 

[Eastside]

Mine acts the same no matter which jack you plug it in.....Robb might be right.......ive used that meter to probe a lot of tube radios.

 

[Eastside]

You were right Robb.....it was the fuse....I pulled the fuse out of my capacitor checker and put it in my dmm and voila it works....thanks my friend

I set the driver bias at 30mA.....and the final bias at 50mA according the alignment specs on the defpom site for the PC-385 PCB/Uniden / President Washington.
Question...why are the settings different from the ones on the pic you posted?

The Defpom PC-385 Alignment Page

 

[Robb]

You were right Robb.....it was the fuse....I pulled the fuse out of my capacitor checker and put it in my dmm and voila it works....thanks my friend

I set the driver bias at 30mA.....and the final bias at 50mA according the alignment specs on the defpom site for the PC-385 PCB/Uniden / President Washington.
Question...why are the settings different from the ones on the pic you posted?

The Defpom PC-385 Alignment Page

The difference of 5mA is negligible. The photo is a page from the SAM's manual for the Cobra 142GTL. Your choice of settings should be just fine.

 

[Eastside]

The difference of 5mA is negligible. The photo is a page from the SAM's manual for the Cobra 142GTL. Your choice of settings should be just fine.

Yeah....I realized that after I looked at how close they were.

I sure am grateful you told me that about the blown fuse....I proly would have bought a new dmm.

I have tuned 28 and 29....I cannot find 36?
28 made the most difference on the meter....29 a little more.....somehow it seems to have made the rx clearer and better.

Do you have a picture of where all those tx cans are ?

 

[sonoma]

lets see if I can post the service manual for a stalker radio. it is the same basic radio as the 142. , I do not have a sams of the 142 but I use this one for a 142 when needed, here is a link to it.

it is in 2 sections. 1 to 20 has the tx align and 20 on has more.

Teaberry Stalker IX

 

[sonoma]

forgot to tell you this will work for the washington you have also.

 

[loosecannon]

eastside,

does your washington have a VR in it near the rear right corner of the board?

it will me in a place that looks like it was meant for a transformer to go in.

if so, this is your AMC control. if you have already disabled R104, then it probably wont have any effect.

just a thought.

also, do you know why the fuse blew in your DMM?

just thought id throw this in so it doesnt happen to you again.

when reading VOLTAGE, you connect the probes "in parallel" with the circuit under test.
this means that positive goes to the trace you want to read voltage on, and negative goes to PC board ground.

im sure everyone already knows that.


BUT!

when reading current, you need to put the probes "in series" with the line you want to measure the current on.

this means that the line must be pulled, and one end connected to positive, and the other end connected to negative.

if you ever have the DMM set to read current (A, mA etc...) and you put the leads "in parallel" with a line that has voltage on it, you will immediately blow the fuse in the meter.

thank goodness for it too, because if it wasnt there, you could really let the smoke out of the radio and the meter depending on where you put the leads.

LC

 

[sonoma]

Loose Cannon on page 4 he posted a pic and it looks like it has the vr under wires for the amc. he says the radio has never been touched so it should still be usable.

 

[Eastside]

eastside,

does your washington have a VR in it near the rear right corner of the board?

it will me in a place that looks like it was meant for a transformer to go in.

if so, this is your AMC control. if you have already disabled R104, then it probably wont have any effect.

just a thought.

also, do you know why the fuse blew in your DMM?

just thought id throw this in so it doesnt happen to you again.

when reading VOLTAGE, you connect the probes "in parallel" with the circuit under test.
this means that positive goes to the trace you want to read voltage on, and negative goes to PC board ground.

im sure everyone already knows that.


BUT!

when reading current, you need to put the probes "in series" with the line you want to measure the current on.

this means that the line must be pulled, and one end connected to positive, and the other end connected to negative.

if you ever have the DMM set to read current (A, mA etc...) and you put the leads "in parallel" with a line that has voltage on it, you will immediately blow the fuse in the meter.

thank goodness for it too, because if it wasnt there, you could really let the smoke out of the radio and the meter depending on where you put the leads.

LC

I do not see anything like that.

The only thing that I can think of is I was checking tube circuits in my Tram Titan II....I was in the final tubes 2 6GK6 and my probe on my dmm touched 2 hot wires and snap...I think that did it.

Thanks for the tech tipss...appreciate it.

 

[Eastside]

What about 38-39....is it worth tuning on them?

 

[loosecannon]

do not tune them!

just posting quickly until i can look at the schematic.

for now, hold off. you can really screw things up if you tune the wrong coil.
LC

 

[loosecannon]

ok, wanted to make sure i had my numbers right before i posted again.

please, please, please, no matter how strong the urge, DO NOT spread or compress L37 or L38.

these two coils are part of what is known as a "half wave filter" and their job is to filter out harmonics while maintaining the same impedance at their input as there is at their output.

messing with these coils in any way will mess this all up and create spurious emissions.

it may make it look to your wattmeter like the power out is being increased by playing with these coils, but to be sure, you are not increasing your wattage at 27mhz one bit.
you are increasing the output at the harmonic freqs, (54mhz, 108mhz, etc...)
your wattmeter is dumb and will just add all these different frequency outputs together, giving the false impression of increased power out, when all you have rreally done is increase the chances that you will bleed on TV's, phones, and computer speakers.

L39 is the 54mhz filter, and it is tuned at the factory for minimum output at 54mhz.
if you mess with this coil, you can only make it worse, because without a spectrum analyzer (very expensive!) you cant tell what is happening at the harmonic freqs.

here is a link to the service manual for the teaberry stalker XV which is nearly identical on the inside to your washington.

http://www.cbtricks.com/radios/teaberry/stalker_ix/graphics/teaberry_stalker_ix_xv_sm_pg01_20.pdf

this has the alignment procedure for the PLL, RX, and TX sections of the radio in it.

unless you have a freq counter that you KNOW is accurate, and a scope that you know how to use, dont mess with the PLL section.

to tune the TX section, set the mode to AM, channel 20, mike gain at max, and key the mic.

using your voice saying "ahhhh" into the mic (never use a whistle) or if you want you can find a 1khz tone on youtube that you can use by holding the mic to the speaker, tune these coils for maximum MODULATED power.

do not tune them for highest deadkey.

tune them in this order:
L26, L27, L28,L29,L36.

(L36 looks just like L39 but is right next to the final transistor 2SC1969)

after doing this, check the power output on channel 1 and then channel 40, if its not equal, then use L28 and L29 to balance the power out across all channels.

now set VR6 for whatever you want your deadkey to be. (no more than 5 watts, and if you are running an amp, 2 watts is perfect)

now go to SSB, turn the mic gain all the way down, and key the mic.
adjust VR5 for minimum deadkey. basically you are setting it for a "null".

i noticed in your pic that you have VR7 turned all the way up. this is a good way to blow your final transistor.

turn it all the way down, turn the mic gain all the way up, and modulate the radio in SSB using your voice or the tone.

while watching the wattmeter (PEP mode) slowly turn VR7 up just until turning it up doesnt increase the wattage anymore.
then back it off this adjustment just a hair.

if you want, i will go through the receiver section the same way i went through the TX section, but it wont be for a couple of days.

here are a couple more links to the teaberry:
http://www.cbtricks.com/radios/teaberry/stalker_ix/graphics/teaberry_stalker_ix_xv_sm_pcb_layout.pdf

http://www.cbtricks.com/radios/teaberry/stalker_xv/index.htm

good luck,
LC