Browning Mark 4

[sonofahbuck]

RE: Browning Mark 4
Hi, hope I am doing this right. Re: Browning mark 4. When I first power up all is well. Aprox. one hour later the channel indicator starts to flicker and corresponding static comes thru the speaker. Sorta like a machine gun/static sound. Soon all this stops the channel indicator lights go out and the transmit goes dead. Rec. works fine. I am not sure where to start. something is heating up,resistor ? Anyone have a suggestion to help me get close ? Spray some of that freeze stuff on and see what happens ? I want to ask you guys before I do something that cant readily be undone. Thanks, Sonofahbuck

[MDYoungblood]

Hello sonofahbuck,
I made this it's own topic as it was not part of the one you posted it to. While you are waiting for some reply's post an intro in the "Welcome to the Forum" topic, http://www.cbradiotalk.com/viewforum.php?f=89 , so other can greet you to the forum.

3's

Greg

[TheCBDoctor]

RE: Browning Mark 4
Hi, hope I am doing this right. Re: Browning mark 4. When I first power up all is well. Aprox. one hour later the channel indicator starts to flicker and corresponding static comes thru the speaker. Sorta like a machine gun/static sound. Soon all this stops the channel indicator lights go out and the transmit goes dead. Rec. works fine. I am not sure where to start. something is heating up,resistor ? Anyone have a suggestion to help me get close ? Spray some of that freeze stuff on and see what happens ? I want to ask you guys before I do something that cant readily be undone. Thanks, Sonofahbuck

Good morning sonofahbuck,

If it takes an hour for your radio to fail I would suggest checking the hardest working component and circuit in a radio, and that would be the power supply. I doubt if it is a resistor. If it is anything it would be the bridge rectifier or series pass transistors; All of the current supplying the radio will pass through these components first. If the component gets hot the problem would normally be a break down in the junction in a transistor or diode.

Since it is a tube radio the breakdown may be a plate in a tube. I would say use freeze spray to isolate the problem, but since this is a tube radio spraying freeze spray on a hot tube will crack the glass on the tube. Since the problem is not in the receiver unit of the Mark IV concentrate on the power supply to the transmitter.

The Mark IV is almost identical to the Mark III so many parts are interchangeable and the same schematic can be used. Here is a link to my website of a photo of a Mark III

http://thecbdoctor.net/_mgxro ... 10806.html

If you are going to re-tube a radio I suggest replacing them all. Good luck and thanks for keeping the older rigs in service. One last thing: You may want to check out and replace any electrolytic capacitors. This is a common problem with tube radios because of the high voltages used. These high voltage caps easily dry out and break down under heat.

Respectfully as always

[sonofahbuck]

Hi CB Doctor, thanks for the reply and info on the Mark 4. I have this set on every day and about 2 days after my post it stopped all the channel light flashing/static and then going dead on tx. I've operated it many times since, leaving it on for 5 hours or more at a time and it's never malfunction again. Go figure ! Those intermittent problems are a real stoneonabeach. Well,, it's running 100% now but,, recapping is just around the corner. Remember,,if it ain't broke, fix it till it is. Thanks for everything until next time, which may not be long with one of these old tubers. Son of ah buck. My Dad's nickname was "Buck" Thanks, Sonofahbuck.

[bluemeanie]

HI
My MKIVA was having similar problems years ago. On the IVA it has a bunch of 1 and 2 watt foil resistors in it and they were breaking down. I had a friend change lot of them and power problems were fixed. Not saying that's your problem. Some of the smarter guys could confirm that but from what I'm told the little foil resistors get suspect when they get old.
Mark

[sonofahbuck]

Hi Bluemeanie, thanks for the post. I'll keep all that in mind the next time it acts up as I am sure the problem will at some point return. I'll then go over what you and Radio Doctor have suggested. Until then I'll just keep my fingers crossed and hope she keeps running like she should. Thanks all, Sonofahbuck.