Help Decide To Buy Broken Browning III SSB?

[Wildcat444]

I found a Browning III SSB that the seller is willing to part with for $200.  He says it has original bananna mic and is in excellent shape.  However, he says that although the receive works great, there is an issue with the transmitter... he says it archs at the mode switch.  I tried to ask more about the problem but all that I could gauge is that if you try to transmit, there are sparks at the mode switch.  He thinks the mode switch just needs to be replaced, but I was thinking a shorted cap (or more) or a shorted tube.

Is this a familliar problem to anyone or can anyone venture a good guess as to what this problem likely is?  I am farely good with electronics but I want to make sure I'm not getting myself into something too deep and $200 is worth it?  I also don't want to find out that the problem ends up being something umreplaceble, extreamely hard to get, or that replacement takes away from the originality.

Thanks!

[w3kq]

I found a Browning III SSB that the seller is willing to part with for $200.  He says it has original bananna mic and is in excellent shape.  However, he says that although the receive works great, there is an issue with the transmitter... he says it archs at the mode switch.  I tried to ask more about the problem but all that I could gauge is that if you try to transmit, there are sparks at the mode switch.  He thinks the mode switch just needs to be replaced, but I was thinking a shorted cap (or more) or a shorted tube.

Is this a familliar problem to anyone or can anyone venture a good guess as to what this problem likely is?  I am farely good with electronics but I want to make sure I'm not getting myself into something too deep>  I also don't want to find out that the problem ends up being something umreplaceble, extreamely hard to get, or that replacement takes away from the originality.

Thanks!

The mode switch is still available

http://stores.goldeneagleradios.com/-strse-48/Browning-Transmitter-Mode-Switch/Detail.bok

Pricey, but it has ceramic wafers, so it should be the last time you ever have to replace it.

Nomad gave an excellent overview of the process and the perils of changing one in an earlier post.  You probably will not be finished making repairs once the mode switch is replaced..... a bad mode switch usually takes out other parts after it has failed.... possible even the panel meter depending upon the failure mode and how much the former owner continued to attempt a "repair" prior to turning the power off and leaving it off. And as Nomad's post points out, it probably is one of the most common problems with these transmitters...  Many have been ruined by an innocent attempt to simply "clean" the switch.

Chris, I am coming up empty on a search for that expose' on the Browning mode switch you provided.... can you post the link here please?

And please note - this is my own opinion, and I'm known as very frugal (alright, I'm cheap), but $200 for an unknown set of problems is too much in my opinion.

Rick

[Wildcat444]

Rick, thanks!  So the most common problems with these transmitters is actually the vary problem he said it has?  Does the control arch or spark when this problem happens like he says his does?  Also, what causes this?

If I meet this guy and look at the radio to decide if I want to take it on, what should I look for to protect myself from a lemon?  Caps and resistors and controls are no problem... I might even have some stock in my own parts if needed.  The meter ($80) would be upsetting but I can't think of anything else that oupld cost too much (I would think the transformers are likely good).  I guess I could pull the cover real quick and test the meter movement with my multitester even while it's still in the circuit right?  Shouldn't I be able to just measure across it while still in the circuit and see if it still works just by the current coming from my multitester creating movement?

[Tubeman]

I've got a Mark III transmitter with the same problem, but it's not from wear, it was damaged.
My shop was destroyed last year by a tornado, I lost a lot of equipment but salvaged some stuff.  One thing saved was this transmitter, it was dirty and scratched up some but after I cleaned it up and some minor repair it worked ok. 
But after awhile it started arcing when keyed.  After closer inspection, I could tell it had took a pretty good lick on that corner under the mode switch.  The switch is cracked and coming apart, guess it took awhile to show up.
When I would key the mike, the mode switch would arc and also the relays.
So I just set it up on the shelve for a later date.  It's still sitting there over a year later. 

[nomadradio]

The mode selector on the Mark III SSB transmitter is a real dilemma. Most of the failures we see have to do with the brown bakelite wafer insulation. Since there are five circuits on each of the two wafers, the spacing between circuits is really close. When the switch is new, the breakdown voltage between adjacent circuits is sufficiently high. Surface contamination will cause leakage current between circuits. If you live in a high-humidity climate, that seems to speed up the breakdown of the insulation.  Eventually the bakelite will break down, and form a carbon track between two separate circuits. The most common circuits to go bad first will burn out a small 3.3k 1/2 Watt resistor that's soldered to the main 3-section filter cap. This will shut down the mike amplifier stages. The next most common will peg the meter when it's switched to the "Mod" position. This is what fries the coil in the meter.

I went looking for pictures, but didn't turn up much. I shot some detailed step-by-step pics a few years back, and then discovered I had gotten a couple of the wire jumpers wrong. Wasn't a big deal to straighten out and fix, but there was no way to go back and re shoot those steps of the process so they would be accurate. Chalked it up to poor planning.

One alternative is to admit that you will never use the radio for sideband, and simply jumper the transmitter for AM only. Bypassing the switch is a lot less labor than replacing it, and cheaper on materials to boot.

Many times we find that the SSB modulator circuit has been fried, along with the carrier-balance control when the mode selector goes bad. Add up the total cost of replacing the switch and all the collateral damage as well, and the "AM-only" option looks better and better.

There's a transmitter here in the shop that was supposed to be the photo model for this procedure. I posted the power-supply rebuild procedures on this forum. The plan was to write up the AM-only 'bypass' procedure the same way.

But as they say, life is what happens while you are making other plans.

Have a look at the 100,000-mile tuneup procedures and see if you think that the radio is really worth 200 bucks. I'm skeptical.

http://www.cbtricks.com/forum/index.php?topic=3778.0

http://www.cbtricks.com/forum/index.php?topic=3829.0

If the relay is no good, you will need to replace both the relay and the socket. The pins are arranged differently on the new socket, so the wires don't go back where they were on the old one. The original relay has not been made for about 20 years, so you probably won't find a replacement that fits the old socket. The receiver speaker will go bad in some percentage of receivers. Not a large expense, but that size speaker is not cheap these days.

Consider how many tubes it will need. This can add a big chunk to the bottom line.

If someone tells you it can't be done, that's nonsense. What I tell the Browning customers is "It's only money".

73

[Wildcat444]

Thanks nomadradio.  You mention that many times the SSB modulator circuit has been fried... is there anything in that circuit that is expensive or hard to find, or is it all pretty simple/cheap stuff like resistors and caps that are easy to replace in the modulator circuit?

Also, can I test the meter when I meet the guy selling the radio by simply pulling the cover and multimeetering across it without taking it out of the circuit?

I have a lot of basic parts like resistors, caps, pots, and tubes already.  My though is that if the meter works and there isn't anything expensive or hard to find in the SSB modulator circuit, then it's not much of a gamble.  Am I wrong?

[nomadradio]

There is no way to know if the damage from the mode selector has gotten into the SSB modulator. It's just a 'worst case' possibility, along with a fried meter.

Pretty sure the meter reads full scale at 1 milliamp. A multimeter set to the ohms scale should get it to deflect the pointer, and show around 1000 ohms (I think) if the meter's coil is undamaged.

Besides, the meter, the mode selector itself is the only rare and expensive part. The rest is mostly labor expense. The SSB modulator circuit is a 'ring modulator' made with four germanium diodes. But they are inside the metal housing of T1. Blown diodes can be replaced, along with the carrier-balance pot. If your labor is, er, "free", that's different from paying a pro his hourly rate. And a lot cheaper out-of-pocket.

But yeah, besides T1, the mode selector and the meter, the rest of the failure components are fairly generic, pretty much all available from Mouser and others. Just be careful removing, disassembling and repairing the insides of T1. Haven't checked the price on that one lately. If it breaks, that's one more expensive part. The part number on it is A542, if you want to look it up at www.goldeneagleradios.com

73

[Wildcat444]

Ah, great!  Oh, I guess one more part which may need to be replaced that is slightly pricy and specialised would be the relay and socket?  Or is there a good chance this is OK?  Thank you so much!

[Wildcat444]

OK, I bought it!!  The meter works.   Both radios are extreamely clean.  No charring on the insides anywhere either.  Now... I examined the control and it does appear to have had some kind of sprey to it.  I couldn't find any breakes or obvious problems with the control but it is hard to see the whole thing.  I haven't turned it on and I'm am only going by the seller's word about the problem (arching at the control).  WHat to I do now?

Also, I tried the receiver without the transmitter connected and it powers up but no sound... does the transmitter need to be connected or do I have more problems?

[jp1116]

You have to jumper pins 4 to 5 and 7 to 8 to get it to work alone. Much easier to do if you have an octal plug. May as well bookmark this page http://www.cbtricks.com/radios/browning/golden_eagle_mark_3/index.htm

[Wildcat444]

Thanks JP1116, OK, I now see this in the schematic.

I plugged the transmitter (without powering it) into the receiver to check the receiver.  The receiver seems to work, but it's meter stays all the way to the right in the red at +40 though... only if I turn the RF gain down will the meter drop down.  AM I setting something wrong or is there a problem?

[Train]

May as well bookmark this page

[jp1116]

Have you tried to zero the meter yet?

[nomadradio]

The S-meter zero adjustment is on the rear panel.

73

[Tubeman]

Thanks JP1116, OK, I now see this in the schematic.
I plugged the transmitter (without powering it) into the receiver to check the receiver.  The receiver seems to work, but it's meter stays all the way to the right in the red at +40 though... only if I turn the RF gain down will the meter drop down.  AM I setting something wrong or is there a problem?

I had forgotten, so I just checked mine and the meter on the receiver does work right without the transmitter being turned on.  The transmitter does have to be connected to the receiver for it to work.
There's just one adjustment on the back of the receiver and it's for the meter.

The condition of those three little 6BA6 tubes, V5, V6 and V7 effects the meter readings. I have just swapped them around and see changes. If you haven't found any other problem, one of them could be bad/shorted.
Hope you have a tube checker or access to one, it's really a necessity with these old birds.

BTW, when you get proficient at changing those TX mode switches, I've got one you can work on.