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

ramblingman

are all the voltages correct at the voltage regulator??

ramblingman

d44 is the anti spiking diode
i would check the big electroylic cap,in the right rear corner of pc board
it will be a 470 mfd @ 10 vdc,i think it is c-135 or 136
anyway if it needs replacing replace with a 470 mfd @ 25-35 vdc

ramblingman

should be clockwise.
but just turn it full clockwise and check,if it cuts off modulation.then just
turn it full counterwise..youll get it.

ramblingman

what is the p.c.b number???
on most ranger units-vr14 adjust the carrier
and vr16-adjust the amc-modulation

ramblingman

vr16 is the amc adjust

ramblingman

dose the tx light come on when you key the ptt,,if not ck r60 for o/c
also ck pin 6 of ic 2 for 6 volts,if not present change ic 3,it is bad.

ramblingman

ck c131 for shorts or o/c

ramblingman

hello,,,i had similiar problem on a 150 gtl dx
i think the p.c board is very similiar..
found the problem to be,,one of the regulators,the
one for receive only ,,had bad solder connection at p.c.b.
it will look o.k.,,you will have to look close under your
magnified light,,while flexing the board.

ramblingman

hello there,,,first before i started changing crystals..
i would first try resolldering all of the crystals.
and also check for cold solders in the v.c.o. area

ramblingman

SOUNDS LIKE THE 10.695 MHZ CRYSTAL FILTER IS BAD

ramblingman

I JUST WANTED TO WISH ALL THE GREAT GUYS THAT TAKE PART IN THIS FORUM A HAPPY THANKSGIVING....DONT EAT TO MUCH BIRD,,HA HA TOO LATE FOR THAT HUH??? IT IS A PRIVILEGE TO BE PART OF SUCH A GREAT COMMUNITY HERE..ALOT OF GREAT PEOPLE HERE,,WITH ALOT OF KNOWLEDGE OF RADIOS..I LEARN SOMETHING NEW ALL THE ...

ramblingman

cb tricks,,,look under the galaxy 77hml exact same as general lee minus the fancy faceplate..another thing you might want to check the diodes around the audio transformer..reason i say,,i have a cobra 148 gtl i bought off fleabay..and it does the same thing..and i discovered some dumdum hooked it up...

ramblingman

O.K. First flip down into ssb mode..Does the s-meter peg with no incoming signal..If so check C-21,C-22. If this is not the case lets then find out if our audio section is working. With a metal probe in hand touch pin 4 of the audio chip The audio chip is a TA7222ap i.c. it has 10 legs inline and mo...

ramblingman

Your problem is most likely a bad front end overload protection diode. This usually happens when a nearby station keys up with high power on. I will have to check and see if i can find schematic,in order to give you the diode location numbers.But most the time,they will be two diodes of same specs.,...

ramblingman

Q134 is either O/C,,Or someone has installed it the wrong way around. Also Q124 May be O/C,,This could also lower the emitter of Q134. Also check for broken traces around Q134..Also coupling cap. C-120 could be O/C..Also i would check D-165 and VR-113 for O/C,,This controls the biasing for the drive...

ramblingman

Probably because the way it is down here..No one talks ssb local in our area..If you talk ssb it will have to be dx..And like the man said thats the fun part of cb radio..Buying a cheap little radio,ive got several used pro 510s for 5 bucks here..And just seeing how much you can get out of it before...

ramblingman

Yes, it did check low on the transistor checker. TR-52 SSB Shunt was shorted, so i think hat is what took out the new MOD Amp TR-51 2SB754. When the fault was on, the voltage across all three pins of TR-51 was 13.0+ v.d.c In turn the radio was dead keying 10+ watts but had no forward and no AM Tx Au...

ramblingman

Check C-128 , If this cap goes bad , it will cause
dc voltage to leak into audio causing a buzz sound on TX.

ramblingman

Just to let everyone know, I got this radio back going. The problem was i got a bad batch of new parts from h and y.. I changed these parts with some old stock i had and that did the trick..The moral to that story is, Dont ever assume just because they are new parts that they are good. I just bought...

ramblingman

The voltage at mirror board is 14.0 v.d.c. I traced R-243 to the ssb shunt switch.So i decided to try and remove ssb shunt TR-52 and then retry unit. Removing TR-52 ssb shunt regained my AM RX. But still no AM TX Audio,Dead key still wide open. I am going to remove T-1 and check it. And check the re...

ramblingman

Yes i removed the mirror board,disconnecting both finals and driver
Excessive current draw still there.R-243 Still gets extremely HOT.

ramblingman

Galaxy melaka- EPT-360014B NO RX on AM , period, NO RX Signal and No RX audio SSB RX Good AM TX dead key wide open 10+ watts dead key with no forward and no modulation SSB Tx also seems alittle low, But it does have TX Audio on SSB. But it only has about 5 or 6 watts peak output on SSB. Audio at P.A...

ramblingman

One or both of the 2sc2290s on the amp board are probably shorted.

ramblingman

First check the mic,,if the shield gets shorted with the audio wire it can cause a squeal..If youve checked the mic and it is o.k..Then next id check the voltages at TR-51 the AM Mod Amp..If TR-51 shorts you dead key will be wide open, no forward modulation..And often it will cause a high pitched sq...

ramblingman

After taking a look at schematic..IC-4 is the 5 volt regulator.
And the 8 volt regulators are IC-6 AND IC-15 these are along
the right chassis rail,the 2 ics closes to the front of radio.
They should be 7808s and the 5 volt reg. should be a 7805.

ramblingman

Have you checked simple stuff first..First of all i would check
the mode switch.Have seen a dirty mode switch cause this
many times.Also make sure all wires are still connected on mode
switch..Poor solder connections..

ramblingman

I would suggest starting taking some voltage readings and relay them to us...Take readings while the radio is in fault mode. And we can compare them with our voltage chart..Like i said start by giving your readings around the voltage regulator chip..And B.T.W. I wouldnt worry about the Am Mod Amp ge...

ramblingman

If the pll was going out of lock..you would have no rx and no tx at all..I would be looking in the area of the voltage regulator chip.. I believe it is ic-4 in this radio,not certain on that number however. But it should be the first chip on the right side rail of radio. It could also be a shunt com...

ramblingman

Input Power- 1 to 5 watts AM/ 2 to 10 watts SSB
Output Power= 25 to 35 watts

ramblingman

He is probably a ham-head..You know they all know more that any of us guys that use and repair cb..They think just because they take and pass that simple ass little test.. They know it all..I could pass that simple little ham test with both eyes shut..But i dont care to talk to those big ego know it...

ramblingman

If its tuning info you want:::::R225 Is the amc limiter L304,L305,L306 is the Am Tuning Slugs.... But i would not recommend cut the resistor R225 out of circuit...I would do it this way...Locate Q205 Transistor Unsolder the collector (Center Pin) of Q205 Amc Shunt and install a 10K resistor in serie...

ramblingman

Could also be a poor solder connection..Next time it quits transmitting
remove the top cover and try bumping around on the pc board with
plastic screwdriver or something non metallic and see if your tx
returns..

ramblingman

Sounds like the regulator is going..when it does this does
the meter light and leds go dim.

ramblingman

Use the cobra service info,The one for the cobra 29 ltd is the same
as the uniden pc76 and the pc78

ramblingman

Yes your are going to have to have that resistor in line
with the rx wire.What this does is shunt any rf back to
ground.To keep it out of the rx circuit.That is probably
why you are getting squeal at keyup.

ramblingman

Wrong again,Sorry
http://www.cbtricks.com/cgi-bin/databas ... s=1&key=72

ramblingman

Sorry Timrim,Try this,the previous one aint gonna work.
http://www.cbtricks.com/cqi-bin/databas ... s=1&key=72

ramblingman

Try This Timrim
http://www.cbtricks.com/cgi-bin/databas ... s=1&key=72

ramblingman

Disconnect the small disc capacitor that is connected to the base tab of the audio chip.And see if it still does it.Also if this does not help.Try installing a rf bead on the audio lead at the mic socket.Also try installing a 0.1 uf disc cap. from the audio wire at the mic socket to the shield wire....

ramblingman

First off start with the simple stuff. Check the mic for broken wires. Then check the p.a. switch Next check for bad solder joints Then do a p.a. test to see if you have tx audio,do this by plugging an external speaker into the p.a. jack,put the radio in p.a. mode,and speak into the mic and see if y...

ramblingman

These radios are equipted with the s.w.r. shutdown circuit. The radio has a switch on the rear panel to switch this on or off. If the s.w.r. is above 2.5 to 1,this feature will shutdown all tx. Im am thinking this is probably your trouble.Try turning off this option and see if tx returns.If it does ...

ramblingman

Usually a no receive/ weak receive symptom is caused by excessive A.G.C. action.What you can do is to disable the A.G.C. and see if normal sensitivity returns..You can do this in two ways, By shorting the A.G.C Bus to ground..Or by lifting one end of a series component in the feedback loop,,like a r...

ramblingman

You may have already checked these?? rx overload diodes,
also the 10 volt caps on the 8 volt rx rail.Just a thought..Also could
be a open I.F. Can.Although im sure youve already tryed tweaking
these,seeing if they had an effect.

ramblingman

Just a thought..I know you said you checked for bad solder connections but,,Have you checked your I.F. Cans Reason i say,,i had a radio awhile back with low receive and turned out that one of the I.F. Cans were not completely pushed though the p.c.b. before they soldered it..This was a factory new r...

ramblingman

Well guys,i guess you could say you never know till you try..I tryed the IRF-520s in the K.L.V 250.And it did work, but like rick said..It did not do the wattage as a amp with the RM-3s in it.And also they seemed to run hotter than the RM3s..With a radio keying 1 1/2 watts and swinging 8 watts, the ...

ramblingman

The MB-3756 Is the Regulator i.c.....And the audio chip should be a TA-7222AP,it should be the largest i.c., that is mounted on the right side rail on your radio,Knobs facing you. You will not be able to see the part number,until you remove the screw and pull the chip back..As the part numbers are f...

ramblingman

Alright rick,,So do you think the erf-2030 would be a better replacement than the irf-520.Or neither of them would be good..As far as these rm-3 s,this is the first time ive ran across this transistor.Expesically in a amp..Of course this is the first one of these k.l.v. amp ive ever fooled with.. I ...

ramblingman

Well thanks guys..Yes i knew i could get them at coppers. You can also get them at h and y.And they are less than 5 bucks each there..But i was just wondering if one of these mosfets i already have would work..Instead of having to wait on the others to be shipped..It was not a matter of price,seeing...

ramblingman

I was wondering do any of you guys happen to know, what a suitable sub would be for the RM-3 Transistor. These are the new type transistors used in the KLV amps. I have a KLV-250 amp here,With no TX.after checking out i found all four transistors bad.I am wondering if i might have a direct replaceme...

ramblingman

Thats right on timrim,Looks like from the pic. the best i can see they are using a 100 ohm resistor on swing kit.This usually produces about 1 watt to 1 1/2 dead key..I always use a 51 ohm here,This will give somewhere between 2 and 2 1/2 watt deadkey. This way you can set your swr meter cal., Also ...

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