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Re-capping the Browning Mark 3

nomadradio

Analog Retentive
Apr 3, 2005
6,935
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Louisville, KY
www.nomadradio.com
I posted a step-by-step procedure with pictures, showing the 'scorched earth' business of recapping the Browning Mark 3 receiver and transmitter about 15 years ago.

On the CB Tricks forum.

Oops.

Can't find the copy I should have kept on the local machine. Might yet turn up, but no joy as of today. Found some of the photos for it still in my ImageShack account.

Some of them. And some are just gone, no longer retreivable for some reason.

Next-best thing is a bill of materials or "BOM", or 'shopping list'. The capacitors listed below have stock numbers from CE Distributing. http://www.cedist.com

The resistors are generic, and don't necessarily have to be non-inductive. Wirewound parts are fine for most values listed. Won't disturb any of the circuits mentioned here. Not necessarily the cheapest.

Here's what we currently use for each:

Receiver:
To replace the 3-section 'can' filter with three 40 uf 450V sections we use the CE number 'C-EC50-50-500"

This is only a two -section part. The schematic says all three sections are 47uf. The factory part you'll find in it will say 40 uf. This two-section 50 uf part is rated at 500 Volts, not 450. Not really important. It will replace C45B and C45C.

But what about that third section? A 47uf 250-Volt rated cap will do this job for C45A just fine. Same part gets used for C58. CE Dist stock number is "C-ET47-250".

While we're at it, the three-legged rectifier block gets replaced with a pair of 1N5408 diodes. This is safer than trusting the 50 year-old original rectifiers. A 4.7-ohm 1 Watt resistor R42 serves to limit rectifier surge current, but gets burned black in a lot of radios. Best to replace it as well. For years we used a 5.6 ohm 2 Watt wirewound we had a sack full from a hamfest flea market. Until they ran out. We currently use a 10 ohm 2 Watt wirewound resistor because we scored a box of those cheap. As you can see, there is some leeway with replacing R42.

Here are a couple of pics for one production version of the receiver:

mk3rxnewc6261arectsr64s.jpg


mk3laterxsn466520c61bca.jpg


mk3laterxsn466520c6261a.jpg


This brings us to C64, a 4uf 150V axial-lead cap that has its negative lead soldered to the rim of the socket for the 6AQ5 tube V10. The positive lead goes to V9B pin 8. A cap with radial leads is easier to just solder the negative side to the rim of the socket for V9. We have been using a 250-Volt cap for this, but can't find one in the CE catalog. They do have a 350-Volt part, says "C-ET350-4.7".

Found a pic:

mk3laterxsn466520c64det.jpg


R58 is a 270-ohm resistor from pin 2 of V10 to ground. It gets replaced either with a 2-Watt or 5-Watt part, depending on what's in stock. The original is a carbon-composition resistor, famous for changing value and overheating the audio tube V10. A resistor is cheaper than that tube. Doesn't matter what kind, just the power and resistance value.
R58 is in parallel with C67, a 4uf 50-Volt capacitor. CE Dist number for it should be "C-ET-50-4.7".
Found an old pic showing a 5-Watt part for R58.

mk3laterxv10aftersm.jpg


We always replace R56, the 2.2k 1/2 Watt resistor with a 2-Watt part. A large "ping" capacitor will get this one hot enough to visibly darken the three red color bands.

Found a pic of the ping parts.

pingpartsui6.jpg


The "ping" capacitor C66 will produce a much longer ping with a 100uf cap. CE part number is "C-ET-450-100".

I just noticed a seemingly-wacky inconsistency in the way CE Distributors seems to embed the capacitor's value and voltage into their stock number. Some of them have the voltage rating, followed by the capacitance. Others have this the other way around.

I'm gonna go back and see if I just jumbled something before I tackle the Mark 3 SSB transmitter. It's a whole separate can of worms.

73
 
Last edited:

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