Search found 433 matches

by The Defpom
Sunday 6th Jun 2010, 11:01
Forum: CB Radio Repair and Troubleshooting
Topic: Ham Jumbo Alignment Problem
Replies: 4
Views: 10352

Re: Ham Jumbo Alignment Problem

If it were me, I would undo everything and return it to original first (apart from the EPROM board), and then go from there, possibly re-modding anything that is needed.
by The Defpom
Sunday 6th Jun 2010, 0:18
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148-GTL issues
Replies: 7
Views: 9429

Re: Cobra 148-GTL issues

Hi, You would still need to align the radio after the conversion to AU, not only the frequencies, but you would also need to align the TX and RX sections as well, as they will likely be tuned for best performance on NZ. You would need a 7 digit frequency counter to correctly align the frequencies, i...
by The Defpom
Saturday 5th Jun 2010, 23:54
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148-GTL issues
Replies: 7
Views: 9429

Re: Cobra 148-GTL issues

That is funny, I get people giving me Cobra 148's to convert from 27 to 26MHz, it almost seems a waste to convert one back ! Basically the NZ mod involves changing a crystal (X3) to drop the radio down by 635KHz (from 11.325MHz to 11.1125MHz) , however, once that crystal has been changed, all you ne...
by The Defpom
Saturday 5th Jun 2010, 23:35
Forum: CB Radio Repair and Troubleshooting
Topic: President lincoln display/audio fault
Replies: 26
Views: 31195

Re: President lincoln display/audio fault

There should not be a connection from the MPU (the large chip) to the speaker, are you sure it is soldered, and the wire has not just come off and lodged between a couple of pins ? Lincolns can be hard to troubleshoot, I have repaired many of them, it usually requires a frequency counter and oscillo...
by The Defpom
Tuesday 27th Apr 2010, 15:47
Forum: CB Radio Modifications
Topic: Adding TX/RX LED to Lincoln
Replies: 7
Views: 15818

Re: Adding TX/RX LED to Lincoln

You could just use a flip flop type transistor switch pair, and feed that directly from the mic TX line, which is 0V when in TX, nice and simple. Yes there are points you could connect to, in order to pick up the RX and TX only voltages, off hand I cant name them, but there is a PNP switching transi...
by The Defpom
Saturday 20th Mar 2010, 20:45
Forum: CB Radio General
Topic: Kudos - Dave Zodiac
Replies: 6
Views: 11528

Re: Kudos - Dave Zodiac

here here!
by The Defpom
Monday 8th Mar 2010, 7:49
Forum: CB Radio Modifications
Topic: MC145151 PLL
Replies: 15
Views: 22808

Re: MC145151 PLL

Hi Dave, Hopefully we can get to the bottom of it. Pin 28 should be connected to 0V through a 220pF ceramic cap to help load down the LD output (minor detail) You have the 8V and 0V markings back to front on pins 2 and 3, pin 2 is 0V, pin 3 is 8V. For 10KHz spacing you want RA0 and RA1 to be low, an...
by The Defpom
Sunday 7th Mar 2010, 9:13
Forum: CB Radio Modifications
Topic: MC145151 PLL
Replies: 15
Views: 22808

Re: MC145151 PLL

Hi Dave, I have used that PLL with an EPROM, only I moved all the inputs over by 1 bit, and set it for 5KHz steps, then the lowest bit can be manually switched to give a 5KHz shift. It is a very versatile PLL, and is able to be configured for many different situations, negative and positive going PD...
by The Defpom
Saturday 6th Mar 2010, 8:55
Forum: CB Radio Repair and Troubleshooting
Topic: Midland 76-900 internal PSU fault
Replies: 6
Views: 8821

Re: Midland 76-900 internal PSU fault

The usual culprit that dies in that power supply is the main current regulator, Q201, sometimes I have found the Zener diode dead (ZD1, ZD2), or Q1. To answer your question, you could use a different diode there OK, as long as they can handle the current they will be OK, as the voltage is low anyway...
by The Defpom
Friday 5th Mar 2010, 14:12
Forum: CB Radio Repair and Troubleshooting
Topic: Galaxy 98vhp deadkey 250 watts on ssb???
Replies: 9
Views: 12954

Re: Galaxy 98vhp deadkey 250 watts on ssb???

Good to hear that you found the fault.
by The Defpom
Thursday 4th Mar 2010, 10:39
Forum: CB Radio Repair and Troubleshooting
Topic: Galaxy 98vhp deadkey 250 watts on ssb???
Replies: 9
Views: 12954

Re: Galaxy 98vhp deadkey 250 watts on ssb???

Then it is likely to be something around the BM, I would start by checking the power supplies and switching, Q34 does the switching, it may be leaky so it is not switching off properly, also check C149, C144, C146, C145 after that you will just have to check each resistor around the IC, R172, R174, ...
by The Defpom
Wednesday 3rd Mar 2010, 11:08
Forum: CB Radio Repair and Troubleshooting
Topic: Galaxy 98vhp deadkey 250 watts on ssb???
Replies: 9
Views: 12954

Re: Galaxy 98vhp deadkey 250 watts on ssb???

I would be looking at the balanced modulator first (IC6), to make sure that it is filtering out the sidebands and only providing an audio carrier, and then go from there.
by The Defpom
Friday 19th Feb 2010, 22:08
Forum: Scanners
Topic: pro 2006
Replies: 7
Views: 43157

Re: pro 2006

I know this is an old thread but in case anyone finds it searching for the same symptoms, I found the cure. Simply replace the batteries, then RESET to Factory Defaults - Both Realistic Pro's I've owned are reset by holding the 2 and 9 buttons down then turn on - you will lose all stored frequencie...
by The Defpom
Friday 19th Feb 2010, 22:03
Forum: CB Radio Alignments
Topic: SWR meter
Replies: 1
Views: 6093

Re: SWR meter

It is not really needed, FS stands for Field Strength, it is used to check the radiation pattern of the antenna, I have never used one, and am not really sure it is of much use anyway, personally I think it was just a bit of a gimmick.
by The Defpom
Thursday 18th Feb 2010, 7:17
Forum: CB Radio General
Topic: Am I slowly killing my radio?
Replies: 2
Views: 7439

Re: Am I slowly killing my radio?

Mag mounts are not ideal, as they are really meant for temporary installations, or ones that require the antenna to be removed frequenctly (such as places that have low height access etc. that said, as long as they are tuned then it will work just fine, it wont be a performer, but it will work. You ...
by The Defpom
Saturday 13th Feb 2010, 23:39
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

You will just have to adjust it and watch the voltage, like I said in my earlier post, aim for about 7V on the highest channel the radio has got, and check that you have at least 1V on the lowest channel the radio has got. The slug could need to be turned either way, as it depends on where it is set...
by The Defpom
Saturday 13th Feb 2010, 15:52
Forum: CB Radio General
Topic: Sound Module Pre-Keyup info required Please.
Replies: 9
Views: 17405

Re: Sound Module Pre-Keyup info required Please.

0V, zero volts, the earth trace.
by The Defpom
Saturday 13th Feb 2010, 15:35
Forum: CB Radio General
Topic: Sound Module Pre-Keyup info required Please.
Replies: 9
Views: 17405

Re: Sound Module Pre-Keyup info required Please.

It may be possible, but it would require that the switch design currently uses the 0V line, the only way to know for sure would be to open up the unit and see if one of the wires goes to the 0V trace inside it, if it does then you could connect the other wire to the TX line and see if that does the ...
by The Defpom
Saturday 13th Feb 2010, 13:50
Forum: CB Radio General
Topic: Sound Module Pre-Keyup info required Please.
Replies: 9
Views: 17405

Re: Sound Module Pre-Keyup info required Please.

The switch may need to be replaced using ONLY the wire connections provided, using another source of supply may damage the unit, or the radio, it is best to keep them completely separated from the radio wiring unless it can be clearly seen that one wire is just the 0V rail. The other three wires are...
by The Defpom
Saturday 13th Feb 2010, 11:57
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

Yep, you need to adjust it, make sure you use the correct size screwdriver to avoid breaking the core.

Monitor the voltage on CH40 and adjust the VCO until it reads 7V, then recheck on CH1 of the lowest band to make sure you have at least 1V there.
by The Defpom
Saturday 13th Feb 2010, 10:13
Forum: CB Radio General
Topic: Sound Module Pre-Keyup info required Please.
Replies: 9
Views: 17405

Re: Sound Module Pre-Keyup info required Please.

You didn't exactly wait very long... 11 hours is hardly enough time to expect a response, maybe people were asleep, or at work, or out. In my case I was fixing a radio, then a I went to sleep... My guess for your requirment would be to make a small relay switching circuit, to replace the push button...
by The Defpom
Saturday 13th Feb 2010, 9:55
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

The easiest way is to just pick it out with a small screwdriver, put it to one side, once adjusted, put it back in a remelt it.
by The Defpom
Sunday 7th Feb 2010, 23:47
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

I would actually say to check the voltage at TP2, watch it when you go from CH10 through to CH40 on the UK band, and see if the voltage stops changing once you get to the channels which are not working, the voltage you see is used to control the VCO frequency, and comes from the PLL, it can only pro...
by The Defpom
Saturday 30th Jan 2010, 14:16
Forum: CB Radio Modifications
Topic: new cobra 25/channel mods?
Replies: 7
Views: 10307

Re: new cobra 25/channel mods?

Yes, he has authored a few books, and service manuals.

For more info about the mixer, if he still has it on his site, go to :http://www.cbcintl.com
by The Defpom
Saturday 30th Jan 2010, 9:14
Forum: CB Radio Modifications
Topic: new cobra 25/channel mods?
Replies: 7
Views: 10307

Re: new cobra 25/channel mods?

The PLL generates different internal N codes for its frequency divider between TX and RX, so the board to replace the PLL must do the same. Lou Franklin designed a mixer circuit which switches the radio from low side to high side injection (or vice versa), and allowed a conversion my by mixing in a ...
by The Defpom
Friday 29th Jan 2010, 22:56
Forum: CB Radio Modifications
Topic: new cobra 25/channel mods?
Replies: 7
Views: 10307

Re: new cobra 25/channel mods?

The PLL is a ROM type, they cannot be expanded. The PLL is the same as a TC9106 except that the inputs are inverted. I have successfully done a band swap to one of these, to convert it to NZ channels, but it is not something that most people would be able to do, I designed a board years ago to repla...
by The Defpom
Friday 29th Jan 2010, 9:35
Forum: CB Radio General
Topic: Wasp CB Mike Connections
Replies: 2
Views: 7274

Re: Wasp CB Mike Connections

I just got one of these in to repair, so can answer this question now.

1 - Audio
2 - Common
3 - RX
4 - TX
by The Defpom
Tuesday 26th Jan 2010, 8:56
Forum: CB Radio Repair and Troubleshooting
Topic: Old rig in need of some TLC perhaps?
Replies: 10
Views: 19507

Re: Old rig in need of some TLC perhaps?

Well that is interesting !

OK, can you find the main PCB's number and tell us what that is, it is likely that it is the same as some other radio inside, if we know the PCB number we will be able know what to base repair advice on.
by The Defpom
Monday 25th Jan 2010, 12:44
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

move the array back first, I was incorrect in thinking it could have been in the wrong holes.
by The Defpom
Sunday 24th Jan 2010, 14:54
Forum: CB Radio Repair and Troubleshooting
Topic: Old rig in need of some TLC perhaps?
Replies: 10
Views: 19507

Re: Old rig in need of some TLC perhaps?

Going by the diagram if the TX LED is on, then the radio is transmitting, as it is powered from the RF output, either that or TR11 has failed. Check the voltages on TR21 (D14), this is the TX/RX switch and should provide 9V or so in RX, and 0V in TX, D14 is the RX voltage regulator, as this switch i...
by The Defpom
Saturday 23rd Jan 2010, 7:35
Forum: CB Radio Repair and Troubleshooting
Topic: Old rig in need of some TLC perhaps?
Replies: 10
Views: 19507

Re: Old rig in need of some TLC perhaps?

Hi, Most radios can be repaired, given the right amount of time investment, and parts availability, the tricky thing is having the test gear available to be able to find the faults, at the minimum you will need a power meter with a dummy load (or tuned antenna), a multimeter, a mic which is known to...
by The Defpom
Wednesday 20th Jan 2010, 4:48
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

It looks like I steered you wrong there, put the array back where it was, that is what I get from going by memory.
by The Defpom
Saturday 16th Jan 2010, 11:17
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

I mention the possible bad etching issue as I have come across it myself on one of my own EPROM PCBs, where a program line worked fine until a different band was selected, as the resistive effect of a partial bridge by copper residue from the band selection input dragged a program line voltage off w...
by The Defpom
Saturday 16th Jan 2010, 7:53
Forum: CB Radio Repair and Troubleshooting
Topic: SUPERSTAR 360FM EPROM
Replies: 38
Views: 46662

Re: SUPERSTAR 360FM EPROM

It could be a badly etched PCB, get a fine knife blade and run it down between every single track on the EPROM PCB, the slightest residue of copper could cause an incorrect input to be seen by the EPROM, you may not even be able to see that the copper is there. I assume that you have tried adjusting...
by The Defpom
Sunday 10th Jan 2010, 21:03
Forum: CB Radio Repair and Troubleshooting
Topic: No Tx audio on cobra 148 GTL
Replies: 8
Views: 13498

Re: No Tx audio on cobra 148 GTL

Great, at least it was TR26.

Now just to sort the meter...
by The Defpom
Monday 4th Jan 2010, 12:11
Forum: CB Radio Repair and Troubleshooting
Topic: No Tx audio on cobra 148 GTL
Replies: 8
Views: 13498

Re: No Tx audio on cobra 148 GTL

With R128 in place, try lifting one end of R161 (this is the SSB ALC feed), I just want to ensure that it is not staying turned on in AM.
by The Defpom
Friday 1st Jan 2010, 1:29
Forum: CB Radio Repair and Troubleshooting
Topic: No Tx audio on cobra 148 GTL
Replies: 8
Views: 13498

Re: No Tx audio on cobra 148 GTL

Try lifting one end of R128 and see if that restores normal TX audio with TR24 in place, if it does then the fault is (or around) TR26 or its feed from the AM TX power control. Some of your voltage readings are a bit odd, please recheck TR25 and TR26 readings. I found my notes, it was on a sister ch...
by The Defpom
Thursday 31st Dec 2009, 0:50
Forum: CB Radio Repair and Troubleshooting
Topic: No Tx audio on cobra 148 GTL
Replies: 8
Views: 13498

Re: No Tx audio on cobra 148 GTL

This symptom sounds familiar, it sounds like the TR24 is loading down the DC supply feeding the audio circuit, so its killing it, you are replacing TR24 with a 2SC945 ? I will have to look up this in my notes, I may be able to direct you to a likely part at fault. As to your meter fault, try replaci...
by The Defpom
Thursday 31st Dec 2009, 0:45
Forum: CB Radio Repair and Troubleshooting
Topic: President Lincoln no RX/TX
Replies: 3
Views: 7451

Re: President Lincoln no RX/TX

I would say to start off by trying to do an alignment and seeing what frequencies are missing or incorrect, as that can give a clue as to the location of the fault. A common problem with this chassis is aging surface mount ceramic capacitors or electrolytic capacitors on the MPU PCB, some of the ele...
by The Defpom
Thursday 24th Sep 2009, 12:51
Forum: CB Radio Repair and Troubleshooting
Topic: 2 differant power levels on ssb
Replies: 3
Views: 6205

Re: 2 differant power levels on ssb

The problem is probably the crystal filter, it may be filtering out the LSB sideband, I have come across this myself before on the same chassis, I had to retune the LSB offset and I.F. to be closer to the centre channel freq to get more of it into the passband of the filter.
by The Defpom
Sunday 13th Sep 2009, 0:24
Forum: General
Topic: expired trial apon instulation
Replies: 9
Views: 20027

Re: expired trial apon instulation

OK, the new version is up on the site now, it is up to version 1.3.0 now. I have added a couple more PLL's to the simulator, and done some other bits and pieces to tidy up some things. I have not tested it on Windows, as I do not have a machine here, as I am on a Apple Mac, but it should work OK. Th...
by The Defpom
Friday 11th Sep 2009, 2:12
Forum: General
Topic: expired trial apon instulation
Replies: 9
Views: 20027

Re: expired trial apon instulation

Because it has been a while since I last did an update to the software I have found that it has needed a lot of work due to changes with the way the compiler works now, I have fixed 2 problems, I only have one issue left, which is purely a display issue, the program still works, but I want to fix th...
by The Defpom
Wednesday 9th Sep 2009, 12:42
Forum: General
Topic: expired trial apon instulation
Replies: 9
Views: 20027

Re: expired trial apon instulation

Interesting, the demo should have expired at the end of 2010, I have just downloaded the latest software which was used to make the program, and will have a new version up on the site soon with some luck, I will post here once it is ready for you to download again.
by The Defpom
Monday 24th Aug 2009, 8:16
Forum: CB Radio Repair and Troubleshooting
Topic: Stalker IX low TX audio
Replies: 5
Views: 8607

Re: Stalker IX low TX audio

Try turning down the AM TX power to 4W and see if the AM TX audio comes right, 10W is too much, if the power output does not change when the VR as adjusted it gives a clue as to where the problem may be.
by The Defpom
Sunday 16th Aug 2009, 1:32
Forum: CB Radio Repair and Troubleshooting
Topic: Rotel 240 noisy TX
Replies: 1
Views: 4126

Re: Rotel 240 noisy TX

Check the PCB for any signs of cracked traces or bad solder joints, years ago when I still lived in the UK I have one of those with the same issue and it was caused by a PCB fault.
by The Defpom
Sunday 16th Aug 2009, 1:30
Forum: CB Radio Repair and Troubleshooting
Topic: GME Electrophone TX830N
Replies: 2
Views: 6411

Re: GME Electrophone TX830N

Dont use trademe, use http://www.ezyauctionz.co.nz instead it is free, faster and safer, (but I am biased). The LED bargraph display should light up in TX, if you cannot hear anything on RX it looks like the radio is a dud, it is probably fixable, but it is likely the fix will be more than the radio...
by The Defpom
Sunday 16th Aug 2009, 1:09
Forum: CB Radio Alignments
Topic: Magnum S9 PCB layout(bottom view)
Replies: 1
Views: 5979

Re: Magnum S9 PCB layout(bottom view)

Sorry, I have been really slack and not been around much lately, so I only just found this post, I have attached the layout you asked for.
by The Defpom
Sunday 16th Aug 2009, 0:49
Forum: Wanted !
Topic: channel selectors needed for 858 chasis radios
Replies: 2
Views: 7004

Re: channel selectors needed for 858 chasis radios

I do not have any selectors, and have not found a good source either, however, I have recently designed and made my own digiscan type units, so far I have made 3 of them, and am still refining the design, but they do work, let me know if you may be interested in one of these. They cover 25.995-28.00...
by The Defpom
Friday 20th Mar 2009, 6:57
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 29 No Keyup
Replies: 18
Views: 25760

Re: Cobra 29 No Keyup

Replace R98 anyway, as the current flow through it could be causing it to change value, I have seen that happen myself before.

If you do not get 5V at D19 with R124 lifted then the fault can only be R98 or D19.
by The Defpom
Thursday 19th Mar 2009, 15:09
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 29 No Keyup
Replies: 18
Views: 25760

Re: Cobra 29 No Keyup

Z10 on the diagram I was using may be called D19 in your radio, it is a 5V Zener diode, you should be seeing 5V across it, if not then check R98 (56 Ohm), as that feeds the 8V to the Zener, so R98 should have 8V on one side and 5V on the other, if the 8V is present but the 5V is not, then it could b...