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

timrim

Is zener diode D-70 breaking down? what does the scope tell us when put on Q-30 and Q-31?

timrim

Well, now I can read the messages, but when I hit send, I get the same message, although, perhaps you got reply anyway?

timrim

Ranger does not like to sell direct, I have had that problem as well, usually they will refer you to one of their distributors.

timrim

On the volvo, I use a bird perch mount which works well. If you do not wish to go that route, your antenna may need a counterpoise, which is a couple pieces of #14 wire cut to 1/4 wavelength and stretched out.

timrim

Still no go, someone else sent me PM, was that you?

timrim

If adjusted properly they should work ok, keep in mind that the problem may be the talkback adjustment in the mic.

timrim

Ok, thanks.

timrim

It did not allow the file to be sent, got a message that the server reset the connection. I am not sure, but I may have fixed the problem, if not, I will post it with a link to the service manual in case someone is willing to take the time to download it. I will know for sure in the next several day...

timrim

Someone sent me a PM, but I get the following message when I click it to read it: "Sorry, but you cannot initiate private messages, users with special ranking can message you, and you can reply to them, you just cannot start a new message thread." Someone with special ranking must have sen...

timrim

Your counter probe is loading down the circuit, if you have a 10:1 probe, use it, there will be less loading of the circuit.

timrim

You need a resistor with a 10uf cap in series with it connected across 2 of the points on the relay. If you cant find the points, I will see if I can dig up a schematic.

timrim

The intermittent transmit problem could be bad solder connections, I would check for those. The problem with having to press the band button is acting like a problem with the math chips (binary adders). I have had this problem with radios in past and found one of the chips bad. I would check for bad...

timrim

Problem here is that the Lincoln does not use an analog meter, its digital. He could attempt to turn the TX meter adjustment (might be R-117 if memory serves me correctly). If that does not work, then its a safe bet the final is dead.

timrim

Sorry Rick, I have been busy with a sick TS-940SAT, or I would have been offering more ideas in here, the SS-158EDX is one of my favorite radios! Ok, check the following parts: Check the following varactors> D-99, D-100, D-148 Check the following caps> C103, C107, C112 You said that sometimes that t...

timrim

I have a Kenwood TS-940S with a possible VCO problem, where is proper place to post it? Also I have the complete service manual in PDF format, but it is 67 megs un-archived. Is it possible to upload it for possible help with radio?

timrim

Yes, it will work fine. That is what some of the older versions used.

timrim

Are voltages correct on IC2 (VCO) and IC9 (TX Mixer)?

timrim

The first thing I would do is press around on board to see if there is bad soldering. Then align the PLL and see if symptoms remain.
But I bet its not quite that easy.

timrim

Bandit is the name. I usually keep a couple on hand in case someone just wants a "set it and forget it" echo.

timrim

Yea, somewhere along the line, I went off course and I was stuck on 2 transistors that did not have their collector voltage!

timrim

Hmmm, I missed a lot of posts

timrim

Is C-130 shorted? Did someone ask if Q124 was shorted emitter to collector?

timrim

Hmmm, I need to go back and re-read everything. I think I missed a valuable clue somewhere. This is why it would be nice for manufacturers to put peak to peak voltages on various stages in service data. Ok let me re-ask a question differently. Is the 27mhz signal at the base of Q-134 normal amplitud...

timrim

I made a typo in my last post and just corrected it.

Is Q-134 bad? What are voltages on Emitter, Base and Collector?

If Q-134 is good, then I would look at bias, perhaps the transistor is not fully turning on. Check R-168 and R-169. Is C135 shorted?

timrim

Is there a 27Mhz signal at Q-134 emitter? If not than Q-134 is suspect. I would also check Resistors 164 and 167. If a 27 MHZ signal does exist at the emitter of Q-134, then check for a 27 mhz signal at C120 L132 C134 junction, if 27mhz signal exists here than C120 is open or bad soldering. If 27mhz...

timrim

On IC-106, are voltages correct? Are you getting a 27Mhz signal on pin 9 output? If so, check for 27 Mhz signal at Q134, if signal is missing and voltages are correct at Q134, it is likely that filter FT104 is bad. If you do not have 27Mhz at pin9 of IC-106, Are both mixer signals present at IC 106?...

timrim

Let me check and see how much trouble it is to get customs forms, shipping estimate etc. I will let you know one way or the other in a few days.

timrim

Using an oscilloscope, check for base to collector gain on the following transistor: Q124. Do you have a 27Mhz signal there with stronger signal at collector?

Check pin 5 of IC103 with an oscilloscope, do you have modulation when speaking into microphone?

timrim

The Kink Kong is a nice antenna, I sell lots of them, but I would try and find one in your country because shipping on antennas can be expensive even shipping here in the states, most boxes end up being over-sized.

timrim

Finals are probably shot. It is not uncommon to have a great match from antenna to amp but a high match between radio and amp. This is because amp manufacturers are cheap nowadays and no longer put in input adjustments to keep swr down. Purchase an inexpensive antenna tuner and place it between radi...

timrim

It's pretty easy, I use the RoadRunner Roger Beep 2, a very nice beep!

timrim

LOL. It can be done with a Yaesu just like in the video, but it cannot be done with a CB, there is no 1.7 MHZ crystal in a PLL CB, nor is there crystals in your toaster, I died laughing when I saw that. Also, your CB would never transmit that high in frequency, and it is FM too! Be aware, that if yo...

timrim

Did you try removing the limiter? I think its TR24 in that radio.
I would also go over the transmitter tuning as well.

timrim

I can say with about 99% certainly that the final has blown.

timrim

Wires seem to be going to PA jack, I believe its normal for that board.

As for the power issue, there should be at least 2, possibly 3 adjustments for power settings, have you tried to adjust them? Perhaps someone set them the same, so that they did not fry their amp?

timrim

I am curious myself if the President George is a current model radio, if not, then it appears quite rare.

timrim

Have not worked on one in probably 10 years, they are rare!

timrim

Mosfets are not drop in replacements. Some other part(s) will need to be removed and the Mosfets will also need special biasing to operate.

timrim

Glad it worked!

timrim

It's the crystal nearest the front of the radio, just to the left of the 3 tuning coils. If it requires adjustment, adjust T-711 for 10.2400 Mhz at the collector of Q21.

Sorry for the delay, I have been busy the last couple of days.

timrim

Press around the PLL / VCO area of the circuit board and see if you can find bad soldering. I have repaired a few recently with this porblem.

timrim

You will need to unsolder the original and put the new one in its place. I have a Cobra 200 on the bench, so when I get to work, I will let you know which one it is. If the radio requires an alignment after crystal install, it will be a minor touch-up on one adjustment.

timrim

It sounds like it may be an AGC problem. Best way to check this is with a signal generator.

timrim

You don't need to worry about the diode. I just assumed that it was how they put in the talkback. The diode is near the audio chip and in front of T1, its D-78, if you wish to locate it.

timrim

If you have the diode clipped to give you a talkback, you can lower the talkback by adding a .047 uf cap from pin 4 of the audio chip to ground. Pin 4 should be the input to the audio chip.

timrim

You can directly replace the 455 with the 1446, so do you just need the mod? I may have a Lincoln here somewhere that has a 455 in it.

timrim

Because the DX959 has a carrier adjustment on the main board, a swing kit could be installed but would not be necessary as long as the modulation limiter is removed. All you would need to do with the limiter removed, would be to set the dead key low. There are various mods that you can do to the rad...

timrim

Sorry, I missed part of your question. They may have used a power transistor because it was all that was handy, or, perhaps they wanted to make sure it would withstand a very strong input. The latter don't make much sense though because its 2 driving 8, and it won't take much input to get BIG output...

timrim

Is there a distributor that still has any MB3756 regulator IC's for the Cobra 140/142GTL's and early 148GTL's? ECG has a replacement and it a whooping $23, last I ordered these a couple of years ago, they were only a few dollars each. I just got one in for repair today, but want to avoid ECG at thei...

timrim

Glad that worked for you. No, the slight drop is only to the RF keyer circuit, not the finals, so your output will remain the same.

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

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