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PC68XL questions

loosecannon

loosecannon

Sr. Member
Mar 9, 2006
4,501
4,244
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hi all,

i just received one of these that was purported to be new, yet looks as if it had been lightly used a few times.

anyway, i have a few questions about this chassis, as it is the first one ive ever played with.

of course, mods are welcome, but i already have the basics-RC/NPC, and ive been to DTB's site and seen the final change mod.

im wondering about how to date the radio using the serial number?
and also whats this DYNAMIC SQUELCH thing all about?
is it unidens "soundtracker"?
is it worth a darn? worth disabling?

i noticed the radio's receive really favors the upper channels, but i dont think there have been any hands in it, as all the goodies are still covered in wax and glue.
its from china, is this common?
i'll align it myself, just curious.

one last question, ive read here on the board to remove the disc cap going from the ground of the audio chip to chassis ground in the COBRA 29LTDs.
there is one in my 68xl, and im wondering if the same deal applies?

thanks for any help,
loosecannon
 

Chinese are fairly new ones , they were also made in the Phillipines , same radios as far as IM concerned. DSC is what it is , it's simply connected to the SQUELCH control . yellow wire will disconnect it and you can put the two other wires together and use the switch for something else. I personally don't think it had anything to do with Cobra's ST system. Just because the wax and glue looks good ,still doesn't mean that somebody could have had there hands in it all the same. I would think the radio should receive the same on all channels but that could be just from the area your in or alighnment of radio ? I can't help you with the cap from the IC to ground , most of the time they are there for a reason , can't figure out why removing it would make any differents ? Have fun and enjoy your radio.
 
thanks for the response,

the cap on the audio chip thing had to do with low modulation or something, and was for the 29LTD series of radios.
who knows, just thought i'd ask.

the only thing i might need a switch for is if i do deadkey wattage switch thing.
you know, like 2 watt deadkey and 4 watt deadkey.

i figure it would just involve different values of the resistor used in the swing mod.
not sure yet if the long wires to the switch would cause a problem.

i will do the alignment and swing mod tonite.

thanks again,
loosecannon
 
Why not a variable?

DSC is useless. On the ones I've had, it disables the squelch control with a preset squelch level.
 
AHAHHH!!!

THAT'S the reason for a "dynamic squelch control"!!! LOL
oh, they think they are sooooo clever, but i figured them out!!!

its there so that truck drivers can take their radios to a tech, and have him put in variable power, echo, or whatever else, and use the SQUELCH location for the control.
with the DSC the driver will still have some sort of silencing mechanism on his radio for those moments when he has to listen to something else, or wants to cut out one of us "annoying base stations." LOL

i think thats pretty cool, and as little as i use my squelch control, i might just put an echo board in this radio.

can anyone suggest one?
i've never put one in a radio before, and im not interested in using it to annoy others with endless repeats; i just want a bit of reverb on my audio.
being a guitar player; i have always been a big fan of reverb.
hmmm, does anyone make a reverb board?
loosecannon
 
I just happen to have one of the original "Tweety Bird" reverb units. Its a spring reverb, same as is found in many guitar amps and mixing boards. email me at the address shown in my signature if you are interested. It won't be cheap, though, those units are getting quite rare.
 
I wonder why someone hasn't picked up the design / patent for the old Tweety Bird units ? They were simple worked pretty well & back during the 70's & EARLY 80's .ALL the big time operators had to have one .
 
DTB Radio said:
I just happen to have one of the original "Tweety Bird" reverb units. Its a spring reverb, same as is found in many guitar amps and mixing boards. email me at the address shown in my signature if you are interested. It won't be cheap, though, those units are getting quite rare.
Click to expand...
..........I've got one of those that I got ~20 years ago. It still works great, only had to clean the slide controll a couple of times. Mine has: D&J Electronics Addison,IL 60101, below the on/off switch as well as a picture of Tweety talking into what looks like a D-104 mic. Just curious if yours is the same as mine, if so....rare is right. (I'm not butting in on your transaction, mine's not for sale) Who ever buys yours, won't be dissapointed for sure. 73's
 
Switch Kit said:
because the cb radio hobby is a dying breed chainsaw. :(
Click to expand...

I think you are way wrong. With the cycle about to erupt again,
you are going to see a great increase in the cb hobby.

Just about every truck in the good old Usa has a cb and
most amateur operators are not going to be able to resist
long distance contacts to be had on any band, including 11m.

Especially in my area, cb is far from a dying breed.
 
Maybe in your area , Not mine , and So.Cal. is a big freak'in place !! This shit went out about the same time diso did in the 70s , it's had a slowly but surely death ever since. Weather or not you think so or not . It is and has been a dying breed for a long time now. Not only that' it can be a dirty fillthy way of communacation compared to Ham radio and other ways. Citys around here don't want them ,they don't want ugly looking antennas 50 to 60 feet towering over the homes (and this aint the FCC it's the cities and what they want and what they don't want ,weather or not you own your own home or not ) people will not tolerate being bled on , ect. ect. ect. I personally love this cb radio hobby , but weather anybody wants to hear it or not , it is truly the trailer trash of communcations ,no if ends or buts about it. If it works for you ? thats all that really matters. You want to run some big power and talk the talk ? So be it ! You want to shoot some Dx and feel good about it ? So be it ! CB radio is what it is. Question is ? How far do you want to go with it ? It's your time and your dime. Weather or not it's for the egotistical self richous or it's for getting directions down the freak'in road ? Enjoy it while it lasts.I never said it was going bye bye , just that it's been a dying breed for a very long time now.I realize it's still going strong (according to souces) else where in the U.S. .....I can count at least 6 shops in the last 10 years that have gone belly up in my area , guys that were in business for decades had to close down because the business was just no longer there , Truck drivers are one thing but homes and mobiles in my area have almost dropped off the face of the earth !! oh sure , you have your lingering hand full of fools , but nothing like it once was NOTHING !! Los Angeles and San Bernardino and Riverside counties are as big as some of those eastern states !! and after 20 odd years in this hobby , I think I know what IM talking about. East coast / West coast bullshit !! I'll surely believe it when i see it and hear it in So.Cal if and when CB radio hit the map big once again .......I think then that would be just about the time the drugs were waring off. I believe CB came from the east coast to begain with , and there's a lot more open areas then the growing and thirving cities in which surround me in California. I glad to hear it's still going strong in other places. Go figure.
 
glad this thread is still going, who knows where its going, but its going.LOL

anyway, im back with some more questions about this chassis.

these are for all the smartie pants's in the forum.

i cant seem to find a schematic for this particular chassis online anywhere.
tried cbtricks, can find PC66, and all the cobra versions, but no 68xl.
if anyone can direct me towards one, that would be great.

my questions will most definitely show my level of inexperience, but hey, this is how we learn.

i noticed that this chassis uses a 2SC458 as the AF driver.
in the 148/grant xl radios, this part can be upgraded to an SK9229.
im thinking this would work in this chassis also. am i right?

the SAMS that i have is for the 21/25GTL so some part values may be different in the 68xl. In the 25GTL, C63 is a 47uF electrolytic capacitor that connects pin 9 to pin 10 of the TA7222AP audio chip.
what would be the effect of raising or lowering its value as it relates to modulation?
could C67 be increased? (470uF going from pin 9 to audio xformer)

D9, the modulation limiter diode, is a 1N60 diode.
would replacing this with a schottky barrier diode such as a 1N6263 (NTE583) have any sort of positive effect?

last, but not least; i have decided to do the MOSFET mod to this radio, and any advice specific to this chassis would be greatly appreciated.
do people also change the driver to an ERF device?

thanks to any and all who reply,
loosecannon
 
well,

looks like no one is interested in my inane ramblings. LOL
oh well.

i did the MOSFET mod to the 68xl today, using an NTE2382 and making my own EKL part from the resistors and a diode.

the NTE2382 is the cross ref. for the IRF520, but who knows if its a 510, a 540 or what. you know NTE...

anyway, i did it just like the cbtricks site says to, except i removed the 68pF cap, as it seemed to lower the PEP by a few watts.

without the NPC mod, i was deadkeying 6 watts and swinging about 40 watts. (radio shack PEP meter)

added the 220uF cap, and two 22 ohm resistors in parallel, which gave me a 3 watt deadkey, and swinging to about 35-40 watts.

i am happy!
this little radio kicks some serious butt now!
thanks for the help,
loosecannon
 

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