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Post by samadams on Apr 12, 2009 9:43:50 GMT -5
Hi there,
I am new to the forum, and new to Browning radios.
This past week, I acquired a Browning Mark III. It’s a really nice looking radio, and in good shape. It hardly has a scratch on it. I knew the radio was not 100% when I got it, but it seemed like a good deal, so I couldn’t pass it up.
With the radio, I also received a D104 (in bad condition, but I have experience with them) and a “channel box” that goes on top of the set of radios. The box says “Synthesizer” and says “Memtrix PLS-4”. This is obviously used to gain access to the channels above 23. It goes all the way up to 27.995. This little box looks well worn, as if the last user used it often.
The owner of this radio said it was his fathers, and it had been sitting since the early 90’s in his garage. When he last used it, it worked. Now, it only powers on. I have been trying to figure out what’s going on. It does not transmit or receive.
I took the radio to a local radio shop, and he told me he did not work on them, or anything tube based. I have a little experience with electronics so I decided to look into it myself. The radio shop told me to spray the knob internals with contact cleaner b/c the copper contacts would oxidize and not work. I have done that, and the radio is still not working.
Here are some things I have recognized when looking in the radio. In the transmitter portion, I have 1 broken tube. The tube is a 7558. Also, on this piece of the radio, V4 (12BY7), V8 (12AU7), V1 (12AX7) tubes are not lit up. These tubes still said Browning on them, so I imagine they were old. I replaced them with NEW tubes. On the receiver end of the radio (or side with speaker) the radio is missing a tube at V4 and the board says it should be 12AT7. Should that tube be installed? All the tubes I replaced are now glowing bright.
Can you guys give me some pointers to get this thing going? I’m really excited to finally use a good radio. I’ve been using exports on the base for a long time, and I really want this thing to sing again.
Thanks for your help, and I look forward to chatting with all of you! I sure would like this radio transmitting again…or even the receiver working, lol.
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Post by FIXR on Apr 12, 2009 10:31:53 GMT -5
The Memtrix PLS-4 is an EPROM controlled synthesizer similar to the control and synthesizer section in the Browning MKIV transmitter. One section of receiver tube V4 is the receiver VFO oscillator and the other section is a mixer. You will have to have one installed for it to receive. Fixr www.TubesPlus.com |
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Post by Tombstone (R.I.P.) on Apr 12, 2009 11:21:47 GMT -5
The suggestions that I'll try and help you are guesses as where to start until a real Browning tech steps in here. A radio that old and sitting that long probably has component failures such as electrolytic capacitors, resistors that are open or have changed value and crystals that are no longer on frequency, among other things. Be careful what you spray into the controls. A lot depends too on how much use the radio has had when working. Obviously this rig has been modified but to what extent. The 12AT7 in the receiver should be intact as do all of the other tubes and make sure that they're not mixed up and in their correct sockets. Spray tuner cleaner into the tube sockets and gently wiggle the tubes in the sockets. The receiver should run independantly as long as the control cable from the transmitter is plugged into it. I assume that you replaced the 7558 tube in the transmitter? The early production Mark III receiver won't tune much higher than channel 23, the late production model will tune a little past channel 40. separate crystals must be added to get to the higher frequency that you describe and another crystal added to go below channel one and there are different ways to do this. There is a main crystal under the left rear of the receiver's chassis that you can remove (I forget the frequency of it right now) and solder a rotary switch to the connections where the crystal was originally and put that crystal and the other crystals on the switch to provide the original 23 or 40 channel band and the ones for the xtras that will result in 23 or 40 channels more per crystal depending if your radio is the early or late production model. This method has it's draw backs since you have to keep the leads to the switch as short as possible and you would have to drill a hole somewhere for the switch. I think that there is another way to do the same thing but uyilizing one of the front panel controls. That's where you need the techs fixr and/or 2600 among others, to get into the fine points of this, they're both members of this forum. If you're not confused yet I'll continue......... Ok, the synthezer box I'm not familiar with. It sounds to me like a group of crystals is used to generate the desired frequency. If that's what it is and not a slider or VFO then it should work and as using a slider or VFO you shouldn't need to have an amplifier or buffer kit to drive the transmit oscillator correctly. Whoever modified the transmitter with that box might have just pulled an unused channel crystal from the rorary tuner and connected the output wires where the crystal came from. If this is the case and the radio won't transmit on the slot where the box is connected it should transmit on any of the other 23 channels as long as the crystals are there and the rest of the transmitter is as it should be. This is the problem, there could be multiple problems and trying to figure out someone else's mods, trouble shooting and repairing can get that much more difficult. There is also a possibility that the aligmnent adjustments have been tuned so far out of wack that the thing won't transmit. There could be other modifications that we don't know of. Now, can you hear the transmit/receive relays click when you key the mic? If not then you may have no voltage or low voltage to the relay's electro magnet windings or the windings are open or shorted (burned out). If this is the case you can work the relays manually with a non conductive tool. If you do hear the click that tells you that the relays are working then there could be a problem with dirty or burnt relay contacts causing a no transmit or no receive condition. Also, I think that there's a Zener diode mounted in the top of the chassis near the power supply that if fails it will shut off the transmit. This may or may not be true of the receiver too, I forget. The microphone.......There could be a possibility of incorrect wiring at the mic plug or a wire that has come off or a switching problem in the mic causing the relays not to work. Be careful, there is high voltage present at the transmitter's mic jack! All of the tubes must be up enough for the radio to run and of course the front controls must be set correctly. There are a lot of other reasons why your radio won't transmit but I tried to touch most of the bases to get you in the ball park but hopefully other techs on this board will step in and help you better than I can, good luck!
Tombstone
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Post by Tombstone (R.I.P.) on Apr 12, 2009 11:29:36 GMT -5
He, he, he. fixr, I was typing my post while you were entering yours. I was hoping that you would jump in here! Now samadams is in better hands.
Tombstone
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Post by samadams on Apr 12, 2009 20:36:19 GMT -5
Thanks for the help from both of you guys. I should have my other V4 tube in tomorrow to try out. I will try out those things Tombstone laid out as well and keep you updated on how this thing is going. Thanks for taking the time to answer me!!
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Post by samadams on Apr 13, 2009 18:41:17 GMT -5
Ok guys, here's where I got to.
On the receiver side, my tube came in. I took the tubes out of the receiver, cleaned the sockets and the tubes and put all the tubes in, including the V4 (12AT7). and....
The receiver IS working! WOOHOO!
Now onto the transmitter. It's still not keying up. The tubes all light up, but I went ahead and cleaned the sockets, and the tubes and reinstalled them, making sure they were all correct. They all glow very bright. When I go to key, I get no relay chatter, or anything. It could be the mic, but the only 2 pin mic I have is a D104 that came with the rig. I have some 5 and 6 pin mics here, but I'm not sure how to wire them to work on the 2 pin plug. Do you think the mic could be the problem? What else can I check on the transmitter? Also on the transmitter the AM/USB/LSB lights are not lit up, and the meter light is not lit up. I have some 5 pin Cobra and 6 pin Ranger mics I could rewire if I knew how to wire them to the 2 pin plug.
You guys have been great. Thanks for all your help. I probably wouldn't have gotten this far without you guys. Tombstone, thanks for all the hints. I did as much as I understood to do, to try and get this transmitter going. The receiver is working awesome...this thing has an awesome receive.
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Post by Tombstone (R.I.P.) on Apr 13, 2009 19:53:36 GMT -5
Glad that you made some progress. Stick with the D-104. To check the key up circuit in the mic unscrew the mic connector from the radio, depress the side lever and run the lock up on the neck so that the mic stays keyed. With a meter or something that will test continuity you should have a dead short or continuity across pin 2 and the shell. If you have that the radio should key up if there's nothing else wrong. If you don't have continuity across pin 2 and the plug shell or you have it on pin one then either the plug is wired wrong or there's a problem in the mic. If the mic passes the test then you would want to connect it back to the transmitter, lock it on key-up, and check for voltage at the relay's coil windings but I don't want you to do that because of a great chance of high voltage shock and I'm not responsible. It could be that your panel lamps and meter lamps are burned out. You say that the tubes are lit up very bright? They shouldn't be like light bulbs. If they're glowing overly bright I'm thinking a voltage problem and the panel lamps being out may have something to do with it but now voltage checks are needed and it's not safe to do by someone with very little experience as you could get killed. You would need a schematic that shows voltages anyway so now it's time for you to find a Browning tech. Hopefully it's just the mic not switching the transmitter on and your panel lamps are just burned out. Could be a mode switch problem too but you need a tech. I wish I could help you more but it's not safe to poke around in there.
Tombstone
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Post by Afterburner(OT-749) on Apr 13, 2009 21:03:52 GMT -5
Send it to FIXR, he can fix anything!
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Post by BionicChicken on Apr 14, 2009 6:59:37 GMT -5
Send it to FIXR, he can fix anything! And you can ship it to him without having to bring it in person!!! Alan does a great job and is one of the best there is on Brownings. BC |
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Post by samadams on Apr 19, 2009 8:40:38 GMT -5
I was planning on sending it to him, and then the wife wrecked her car. (she is ok). Now I have to fork out money for the deductable. This is going to put a set back on me sending the rig out.
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Post by Afterburner(OT-749) on Apr 19, 2009 13:53:20 GMT -5
As long as she is OK. Wife's ... can't live with them... Can't live without em!
They just sometimes mess up a good man's dream.
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Post by BladeRunner now OLD FLASH!!!!! on Apr 20, 2009 11:47:39 GMT -5
I'll second the "send it to Fixer" idea. Sorry to hear about the wreck and i hope your wife is OK.
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Post by samadams on Apr 22, 2009 7:11:45 GMT -5
Thanks guys. She is doing great, but the new Volvo XC90 we just bought last Auguest is not, lol. It's a total loss. And of course, this means the insurance company wants to give me what the car is worth NADA and not the payoff value. For what they are offering me, I cannot even buy a used one. Go figure.
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