The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

zeppfrog

thanks, and yes, its off on an external as well as far as i know, it wont send out enough power to test on my external really. will double check those

zeppfrog

if the switch is the problem, they are around on ebay... or http://www.pacific.us.fm/pacific2005/store/index.html maybe

zeppfrog

thanks for the response again ramblingman, i did swap a few of the electrolytics rick mentioned, yet to find a few of them. I will get those voltages for you in the morning. thanks

zeppfrog

by the way, should have mentioned this before at the start. The Mod does bump to about 20% when you first key then drops to zero. if you continue to key it, the percentage drops as well.

(replaced IC 4 and tr 50 with no effect)

zeppfrog

Replaced tr51. the odds of me havin a new 2sa1012 are bout as good as me winning the lottery, but i did. :lol: Got the dead key back now and good watts. thanks ramblingman. now you dont know a substitute for the 2sa934 do ya? still hunting for my missing modulation, thinking of swapping out the audi...

zeppfrog

Thanks RamblingMan. the tx/rx light is coming on and the meter still moves on key up. So I skipped the first two, tr 36-38. checked the diode just for voltage and got 6vdc rx/ 5.83 tx TR 51 TX/RX 1.76/1.36 1.05/-0.51 10.93/10.87 TR 50 TX/RX 1.75/0.30 1.05/-0.51 1.79/0.35 TR 41 TX/RX 10.15/10.02 7.64...

zeppfrog

welp, i sKwewwed the pooch. swapped out several of the capacitors with new, then i was tweaking around the VR's (hi/lo pwr and mod) to see if i could get anything, (nope) the looked away and zoik poof... yep, i was using the metal screwdriver. lost all output. can hear it key up but thats it, no sig...

zeppfrog

look at my post on the cheapskates power supply, and i get good results from at and atx. there is a link there as well to a nice mod for your pc power supply, but if you are lazy, tap it into the yellow and black on one of the drive connections and turn on the pc... (if you remove it, you need to pr...

zeppfrog

any chance anyone knows what the purpose of that bottom left socket is for, i have an old connex with it and three wires , (orange, red, brown) coming off it. the brown goes to the am/fm/pa selector, the other two go to the main pcb. There is also a Yellow wire on the audio in and out both. one goes...

zeppfrog

i thinks you will need to remove some windings on those big ferrites and also change several capacitors. i have studied on changing my texas star from 2290's to the 2879 and studied the parts lists on cbtricks. might check some of those out on your model or look at the list for the texas star for id...

zeppfrog

also make sure the new diode is installed proper... ie: the white stripe to the right if the arrow on the pcb is to the right.

zeppfrog

mic first, (borrow a good one from someone) then it may be losing its modulation or off frequency on transmit

zeppfrog

already built several here, one even from an e machine to power my mobile tester at two amps. others range from seven to eleven amps so far from at and atx. not getting any static from them at all on my radios and have gotten alot of repairs made since. on the AT power supply you follow the same ins...

zeppfrog

Ok, anyone playin with cb's has either needed or trashed their power supply with to big a radio... like me... all my 12v batteries took a dump too, and my wife has my hobby money down to a trickle. I need power... hey, did I just find that old dx 33 in the garage... not much good even for a boat anc...

zeppfrog

-thanks guys, gives me someplace to start. making my christmas components list now

zeppfrog

that or i blew something out... ;o)

zeppfrog

so far I quickly tested pin 9, not sure which is 9, but tested all 4 corners to see what i got... on the back side left, i get a voltage rolling between 1.5 and 3.25 (roughly) the other three corners are also erratic but i get the negative along with a 0.10 area voltage. as with the frequency, all e...

zeppfrog

For the 2sc 1969, i believe i ordered from RF Parts. or http://www.MCMElectronics.com

zeppfrog

i dont really know the model, but just using some guess work here. if you are sure the wiring is correct on the new pot, and i trust you did a good job on that, then it could be there was a cold solder joint just waiting to be disturbed. it also could be that something attached to the chassis, such ...

zeppfrog

I have had this thing on my shelf awhile. was pretty dirty when i got it, and frequency didn't just drift, it rolled. I removed the extras from it, like extra crystal switch and restored the original in its place. then i replaced the pll but the frequency is still rolling. on the tester it shows the...

zeppfrog

did you have good wattage before changing the volume pot? I would check there first. miswired perhaps.

zeppfrog

if you are receiving ok over a mile, (and you have a decent antenna setup) I would do the 2sc1969 mod to your ltd. if you are a decent solderer and can get the parts (rf parts or others online) its pretty inexpensive. To have it done costs a bit more. still the most bang for the buck in a cobra 29. ...

zeppfrog

or drop a fat little resistor across the grounds of the pa/ext spkr on the back solder side of the main pcb. changing your resistance changes the volume of your talkback. running a pair of wires in series with these to a switch will make it switchable as well.

zeppfrog

hey guys , I got yet another cobra 29 question. I made a trade on a chinese made 29 ltd classic. at first it appeared nice n clean and stock. so, before any real testing, i made a swap for a nw st i finally fixed (after over a year if receive problems, tip[tiny black spec of a resistor on solder sid...

zeppfrog

likely the change in wattage has changed how your meter is responding. I would not rely heavily on the built in swr meter in a cobra under best of conditions. as said , use an external swr meter to set your antennas. (your radio doesnt care if it has the cal knob all the way left or right while your...

zeppfrog

not alot to do to this one. as you can see, its not very large, so not much circuitry to play with... just not an overly popular model for the hacks

zeppfrog

that nightwatch illumination is real nice til its tampered with or quits... no simple bulb here. even rubbing a pair of needle nose against the edge around one of the knobs (say removing the dimmer pot to add echo) can kill the illumination around that area. only one fix... remove and replace the en...

zeppfrog

+10 would be good

zeppfrog

i think yer money is better spent when you start breaking 100 bucks on a cobra of any kind and adding bells and whistles to get what comes stock inside a "Big Radio" to just get the big radio in the first place. i see drivers all the time taking their 100 dollar 29ltd and dumping in anothe...

zeppfrog

well said

zeppfrog

bah, dont care about right or wrong... those are just abstracts... what i do care about is a nice loud flatulating sound after i am finished speaking my piece... should have come standard in the radio instead of that annoying beep

zeppfrog

rick, youre a pretty good hand... umm, but your picture scares my kids... and me a little bit

zeppfrog

any quik ideas on this one. whenever I plug this cobra in (with the power off) it lights up momentarily. then i turn it on and it works ok. I am concerned about this thing lighting up with the power switch off...

zeppfrog

good tip... not sure, since i keep my sound off on the pc... and too lazy to crawl under and hook it up , if my own board makes the same noise you are talking about, an odd farting sound... lol... but sounds like the trick to me. I have tried the astatic in several radios myself and came up with thi...

zeppfrog

i vote AStatic or RK-56 and never (personnally) use a mic that requires batteries... its self defeating. you either run against the amc which is going to cut it back or if the amc is clipped its going to make a bad sounding rig worse. I use both the astatic and roadking rk56. the rk56 is heavier and...

zeppfrog

i removed the weather board from a like cobra 29 wx ltd. desoldered the wires from the main pcb and antenna. (havent removed anything from the cb/wx switch on front) installed an echo board and the control into the removed weather band selector hole. I plan on rewiring the cb/wx switch for talkback ...

zeppfrog

Thanks redeye, good place to start. I probably knocked out one of the solder joints there when i was looking for the other bad solder joint

zeppfrog

read this one, once i noticed that my 29 classic was doing the same thing only with different channels. 1-2 on 3a; 5-6 on 7; 11-12 on 13; 15-16 on 19a; 21-22,25-26 on 27; 31-32 on 35; and 35-36 on freq 27.515. since I just resoldered a connection near the channel LED where part of the 9 was missing,...

zeppfrog

well, still didnt get those caps tested, though the solder under the larger looks suspiscious. had a baby boy at 12:05 this am, (well, not me, my wife did) here's cyber cigars to everyone and I will get back on this one as soon as she lets me. :) , yes it does receive in fm, but no mod there either....

zeppfrog

going to maybe save myself a headache, and just ask a dumb novice question. Using which setting on my ohm meter and what reading should i look for in the capacitors, also, should the radio be plugged in/on/or neither when checking... thanks (novice i said, heh) did a quik search so should be able to...

zeppfrog

nada in FM. 1 Thru 4= 4.14, 4.16, 4.26, 0.09

zeppfrog

no change to the mod, but i did bring the hi and lo deadkey back to 3/12. I also found a better diagram last night of the VR's. seems the one I have is more for the ssb models, doesnt show the hi and lo power settings. going to have a go on that in a bit, but I suspect I already messed with those a ...

zeppfrog

did some testing on the ic voltages, ic 4 and ic 8. both are somewhat off from spec, but not sure enough to matter. wish there was a real decent radio tech nearby, not a parts changer. (aka thief).a good vco and pll alignment might illuminate the problem. i suspect either one of these ic's or the re...

zeppfrog

Mod adjust does very little, goes to nothing at all, or slight bump. i have been pressing around on the area around the audio ic, ic8 and ic 4 and i seem to get the mod to go up, appears that tr 52 has been removed, and there are a pair of resistors tied to diodes near there. also looks like a capci...

zeppfrog

ok, better info now. i got another meter and retested, getting about 10 watts on lo, 15 on hi. also set up another radio to listen for noise, and yep, getting a kind of a low hum. you can almost hear the voice over it, but too fuzzed and low. also, i moved the echo down and it did lose the hum for t...

zeppfrog

btw, not the HP. single final, at this point, but its my hope to change that after i get it going right

zeppfrog

thanks Timrim, will check those and let ya know how it goes

zeppfrog

ahh, i think i see what you are saying... my meter has three meters in one as well. one for power, one for modulation, one for swr. the power hits 40, the mod just bumps and drops. but I think i understand you are saying there may be some internal noise killing my readings. I also have an audio mod ...

zeppfrog

I wouldnt qualify my power meter too highly, i have a 5/50/500 meter and set it on 50 and hits the 40 pretty solid. i turned it back to lower the output just to see if it moved, and it did, so i moved it back up for now just to leave things as they are and not create new troubles.

zeppfrog

I have found lots of mods for both these, but as for limiters. leave them in place. nothing is more annoying than hearing a loud unintelligible radio. both these rigs are great for power, and if you have the bux to spare, i would recommend sending both to sparkys cb shop. He did a top notch job on m...

The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Search found 51 matches

Cheapskates Power Supply

Cobra 2000 thinks it is a scanner

29 ltd mod confuzzled, Rick? (anyone?)

Cobra 29 LTD *wx removed false start

similar prob on a cobra 29