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

Hey Homer, was browsing the forum & seen your post & figured I would comment, I’m not on this for as much as I use to be. But your antenna looks great as always man, very nice; I always enjoy seeing your home built antennas. I wish materials were not so expensive or I would try to build some...

I wondered about it. I wish I had the means & the knowledge to do it as I would. Be cool if someone could, it was a nice chip for sure. And sorry for jumping in on your thread, just seen you mention about the code for the chipswitch & thought I would pop in as I have wondered about it for a ...

Hello, first off, KC7NOA I hope you get the radio sorted out. Wish I had the knowledge to help, but I do not. My question is, is it possible to read the code from a Chipswitch & what would one need to do that? It would be great if someone could start making new ones. It seems like there are quit...

Hello!

Check ZD1, it is a 12 volt zener diode, it sounds like it may be open circuit. I hope the schematic for the PS-8K is the same as the PS-8KX as I am going off of the 8KX version, it should be the same board though.

The Defpom, Yeah, I think we all had fun working out the problem! That is an interesting idea about keeping on the same radio for the puzzles. Would give people great information on actually finding problems in a particular model radio & how to go about troubleshooting them. People can follow al...

Quote from my last post:[/quote]so I am glad we got to help you for a change even though you already new the problem [/quote]. Rick, I understand exactly that this was for fun & you new the problem with the radio before you posted & this was to see if any of us could find the problem, I unde...

Hello again Rick! Glad to hear you found the problem! :D I would have asked about C60 as well, but to me in the schematic I could not tell if it was in parallel with C75 or not, it almost looks like it connects to R88 only & ground, I figured I would start with C75 first since it is clearly conn...

Rick,

The voltages on IC104 seem a bit low, especially the VCC Voltage on PIN-1 & PIN-9, which is probably why PIN-6 & PIN-7 have low voltage as well.

Check C75 as it may be shorted to very low ohms (faulty) & could be causing your transmit problem.

Rick, What is the DC voltage on PIN-1, PIN-6, and PIN-7 and PIN-9 of IC104 in RX mode & TX mode? IC104: RX mode PIN-1 = PIN-6 = PIN-7 = PIN-9 = IC104: TX mode PIN-1 = PIN-6 = PIN-7 = PIN-9 = It looks like the voltage on PIN-8 of IC104 is not going high enough in TX mode to conduct D147 & Q136.

Rick, What is the DC voltage on PIN-8 of IC104 in RX & TX mode? IC104: RX mode PIN-8 = IC104: TX mode PIN-8 = Looks like Q136 is not getting switched on, as there is not enough voltage on the base. Check D147 & make sure it is not open circuit (faulty). I probably won't be able to figure out...

Rick, What is the DC voltage at Q125 in RX mode? Post the voltages for the Base & Collector only, the emitter voltage appears fine at 7.95 volts, but the collector voltage is too low at 0.25 volts & the base voltage appears to be a little to high at 8 volts in TX mode. Q125: RX Mode B = C = ...

Well since I am still learning & understanding repairs I would normally not try to help anyone as I do not want to give anyone false information, however, since this is for fun I may do some posting as well. This was an excellent idea Rick, & hope to see more of this kind of thing in the fut...

mag69,
Your welcome! Have fun! Take care. Pioneer621

Hello mag69, The problem with trying to explain how to install a MOSFET final in this radio is difficult, as many of the parts in this radio are not labeled (mainly capacitors), UNIDEN decided to do that in a few different radios. Makes it extremely difficult to tell someone what parts to change or ...

why would you try to mod a am only cb budget radio for ,also how come some of these radios i have seen in the usa are only am fm ,i dont know how anyone can pay $400 plus us upto $800 for a fm am band only radio thats 1 big joke to me .you can buy a brandknew icom706mk2 g that is all mode all bands...

Yes, that is correct. You can Adjust L10, & spread or pinch L8 & L9, you will have to tweak them for best performance, spreading them may not increase output but in fact may lower it, you may have best performance with them pinched together, so just watch the output on a watt-meter & tun...

newradioguy, Yes, the Cobra 25 WX NW ST should have the same mods as the Cobra 25 LTD CLASSIC. I just tuned up a 25 WX NW ST the other day & I did it like any other 25 LTD, so I beleive all the mods should be the same. The only really main difference in it from a standard 25 LTD is the Night Wat...

Good to hear the mod went well! Yeah, the slugs are delicate and can easily be damaged if not removed very carefully. As for the receive: No, you did not do anything to the receive, you only modified the transmitter section. I have never personally done any receive mods to the Cobra 29 LTD other tha...

I am glad to hear the info helped! If you have any problems & can't get the radio modded right, I would be more than willing to try & help you out to get it working right; there are many other people here that would most likely be willing to help you out as well, though as I said before, if ...

Hi, what I meant was after you get the new parts installed and you are adjusting the output power (wattage) of the radio on a wattmeter you can tune “adjust” L14 for a 4 watt carrier, the carrier is when you hold the button on the MIC & do NOT speak into the MIC, you transmit just a silent dead ...

newradioguy, Hello, I have installed the MOSFETS in a UNIDEN PC76XL & they worked great, you will have no problems if your careful when soldering & don’t create any solder bridges or install anything wrong, just take your time on each step if you have never done it before. Once installed &am...

NightRanger3151, Thanks for the update! I am glad to hear it worked well for you, as it has for me. As I mentioned before, I am not sure if it is the greatest method, but it seems to work well & I cannot see any harm in doing the modification. I try to help out when I can. Take Care & have f...

NightRanger3151, I have experienced that same thing with my Cobra 29 LTD’s, it probably has done it on the few dozen or more I have worked on, they must be designed like that. The noise is strange, it is kind of a muffled up static that is heard through the radios speaker when the SQUELCH is just ab...

Thanks for the info Rick, I will keep that in mind next time I have that problem with one of my radios, I did not even think of using a choke in series with its input, I appreciate the info! NightRanger3151, you may want try the choke in your radio as Rick suggested as that may be a better solution ...

NightRanger3151, I am very happy to hear you got it working & the info I supplied helped you out! As I said before, it is probably not the best method out there, but it does usually always work & is easy & quick to do. The guys that were helping you are VERY knowledgeable & would hav...

Hello! Just thought I would give an idea of what I have done to eliminate the RF feed back type problem with the echo boards. I have installed a couple dozen or more of the ASTATIC echo boards in Cobra 29 LTD's (most versions of the 29) & have encountered that very same problem, MANY times! The ...

Hello again, I have not been on here in a little while. I really appreciate your reply's to my post! Thank You very much Defpom! And Thank You very much Rick! Your replys are very helpful. I have not really had time to trouble shoot that radio, so its basicly been sitting on the shelf. It may be the...

Radio. Mirage 88 Problem. don't seem to be locking on any frequency's Hi, I have a Mirage 88, same radio as the GALAXY 88HL radio's. It powers on ok, but has no receive in AM - USB - LSB, but in FM I can here normal static only. When I transmit, the light goes red but no output. When I change the ba...

Hi, Have you tried plugging a good external speaker in the EXT Speaker jack in the back of the radio. I have had a blown speaker in the radio put out slight sound before but you really had to turn it up to make out what was being said, so if you have not tried that its always worth a shot. Also, Doe...