|
Post by 238 on Aug 1, 2020 21:46:01 GMT -5
Has no audio. Found that R46 470k ohm is bad,pin 2 to ground. Also on pin 3 it has R47 150 ohm to ground,this is correct. It also suppose to have R78 22 ohm in series with C54 25uf to ground from pin 3. But they only have a 100uf x 50 volt to ground no resistor. Should i change it back like it suppose to be? 238
|
|
|
Post by 2600 on Aug 3, 2020 1:03:25 GMT -5
So, uh you're talking about the 6BQ5 modulator tube, right? More than one tube in that radio. We use a 22uf 50-Volt cap from pin 3 to ground, and simply lose the 22 ohm resistor. It was put there to reduce bass response, best I can tell. The original 150-ohm resistor from pin 3 to ground was rated at 1 Watt. We use a 2-Watt part to replace it whether it looks bad or not. Would be a good idea to check R51, a 3.3k 1/2-Watt resistor that has one end soldered to the 3-section 'can' filter capacitor. If it's burned, this is what killed your mike audio. The cause is the breakdown of the mode-selector switch. The brown bakelite plastic degrades, causing that resistor to be fatally overloaded. It's possible to 'hot-wire' the radio and unhook the shorted sections of the mode selector. This makes the transmitter AM only, and disables SSB transmit. Or you can replace the selector. Not cheap. Not easy. Have a look at R51 and see if it looks overheated. 73
|
|
|
Post by 238 on Aug 5, 2020 21:49:23 GMT -5
This is a early model transmitter. I am sure the mode switch is in bad shape. R51 has been hot, but still works. I thought i might be able to make it work for him on AM, but it has to much wrong. I know he can not spend what it would take to fix it. I looked on Barkett's site an a mode switch is now $90.00 + shipping. His receiver is in good shape, so he would be better off to find a good transmitter. 238
|
|
|
Post by 2600 on Aug 7, 2020 0:41:11 GMT -5
All the more reason to put together a "how-to" for bypassing the mode selector altogether. We have "hot wired" this transmitter for AM only. It's a lot cheaper than a mode selector. And besides, the mode selector often damages other components used for sideband only. Don't want to put in a new selector and find that SSB transmit still won't work.
One problem is the number of production changes over the life of the product. Wire colors change from version to version. I do have pics from the late version, the one that has the SSB ALC pot sticking up out of the chassis along the edge between the final and driver tubes. Even so there may be more than one version with that control.
Wish me luck. Got other irons in the fires.
73
|
|
|
Post by vanlifeson on Aug 7, 2020 12:24:48 GMT -5
All the more reason to put together a "how-to" for bypassing the mode selector altogether. We have "hot wired" this transmitter for AM only. It's a lot cheaper than a mode selector. And besides, the mode selector often damages other components used for sideband only. Don't want to put in a new selector and find that SSB transmit still won't work. One problem is the number of production changes over the life of the product. Wire colors change from version to version. I do have pics from the late version, the one that has the SSB ALC pot sticking up out of the chassis along the edge between the final and driver tubes. Even so there may be more than one version with that control. Wish me luck. Got other irons in the fires. 73 Does the SSB ALC pot have any effect on AM audio?
|
|
|
Post by 238 on Aug 7, 2020 23:18:03 GMT -5
I am going to try an wire it for AM only. If you put it on SSB it blows R60 i believe it was. It goes to the relay. I put it on AM an took the knob off. I am going to see if i can figure it out. When i work on this stuff it is for people that can not afford to send it to a shop. I do not charge to fix it if i can. I do it to also help educate me on this old radio. 238
|
|
|
Post by 2600 on Aug 9, 2020 0:23:05 GMT -5
Yep.
Setting the ALC for clean sideband audio tends to make the ALC also kick in on AM modulation peaks, holding it back. The ALC is supposed to be disabled in AM mode, but they didn't get that exactly right.
Turning the ALC pot for max AM modulated power will effectively disable it for sideband transmit. And if the sideband receive on this radio was any good, that would be a bad thing. Most anyone who can afford to put a Browning on the air these days also has a "real" sideband radio of one kind or another. My customers would rather have full modulated AM power than clean SSB transmit that they'll never use.
I have a set of pics that I took of this process. Used them last week to speed up hot-wiring a Mark 3 SSB for AM only, so that's sorta like proofreading. Just gotta get the pics cropped, sized, downloaded and a description worked up.
And proofread.
73
|
|
|
Post by easymoney on Aug 16, 2020 18:54:14 GMT -5
Hello to all,
I’m new to the forum. I’m trying to get a MKIII up and running. When you turn the transmitter on it instantly smokes R64 the 4.7 Ohm 1watt resistor. I’m thinking the old PD&E diode is bad.Has anyone had this problem? Or maybe could shed some light on what needs to be done to fix the issue?
Also it has been completely recapped.
Thanks for any help, Easy money
|
|
mattbee
Mudduck
Tram & Browning Enthusiast :)
Posts: 38
|
Post by mattbee on Aug 17, 2020 6:15:39 GMT -5
Shorted Electrolytic Capacitor, and or the Bridge Rectifier is bad as well.
|
|
|
Post by 238 on Aug 17, 2020 8:28:48 GMT -5
I would replace all the parts in that circuit. That way you know it is in good shape. 238
|
|
|
Post by easymoney on Aug 17, 2020 13:41:53 GMT -5
I will upgrade it the way 2600 shows on an earlier post. With the two diodes and caps.
Thanks for the help, Easy money
|
|
|
Post by easymoney on Aug 23, 2020 20:53:51 GMT -5
Installed all new components. Talked for about 30 minutes and it started smoking the new caps and R51 is over heating.
|
|
|
Post by 238 on Aug 23, 2020 22:25:04 GMT -5
If R51 {3.3K) overheats the mode-switch is going out. 238
|
|
|
Post by 2600 on Aug 26, 2020 23:12:21 GMT -5
Installed all new components. Talked for about 30 minutes and it started smoking the new caps and R51 is over heating. Ah, what size fuse is in this transmitter? The original 2-Amp size should have tripped before damaging a pair of 3-Amp B+ rectifiers. The only two ways to overheat R51. C47A failed as a short, or failed mode selector. 73
|
|
|
Post by easymoney on Sept 3, 2020 14:32:39 GMT -5
2600
Sorry for the delayed response. I never checked the fuse until you asked. Someone has replaced it with a 20amp. I changed it and the transmitter Will run for about five minutes then pop the fuse.
I think I’ll just set them on the shelf.
Thanks, Easymoney
|
|
|
Post by 2600 on Sept 4, 2020 22:50:56 GMT -5
Lately when a customer says he wants a Mark 3 radio repaired, I bring up the mode selector right away. It has gone from being a failure-prone part 30 years ago to a 'sooner or later' failure. Unless the radio has no more than 500 original miles, that selector is very, very likely to be breaking down bit by bit.
Eventually I'll manage to write up the 'hot-wire' alternative. The transmitter can be wired around the selector to use it only for AM transmit. Cheaper and easier than a new selector. Especially when additional parts in the sideband modulator get clobbered.
There are enough production changes found in that transmitter over its production life that a single set of highly-detailed "clip the blue wire" instructions won't be practical. Each of the several revisions of that transmitter have small changes to the wiring of the selector.
Got some pics shot, but not cropped and resized yet. Need more 'round tuits'.
73
|
|
|
Post by easymoney on Sept 5, 2020 11:05:15 GMT -5
I’m not sure what revision this one is.
Someone else said the mode selector was probably bad.
I’ll open it back up and see if I can figure out how to bypass it.
Thanks,
Easymoney
|
|
|
Post by SIX-SHOOTER on Sept 14, 2020 11:31:10 GMT -5
I am going to try an wire it for AM only. If you put it on SSB it blows R60 i believe it was. It goes to the relay. I put it on AM an took the knob off. I am going to see if i can figure it out. When i work on this stuff it is for people that can not afford to send it to a shop. I do not charge to fix it if i can. I do it to also help educate me on this old radio. 238 SSB on a Browning SUCKS anyway so losing SSB is not an issue for me if it was mine.I have owned every Browning base radio ever produced & that includes the SSB models & I found SSB a waste of time & effort on all of them.I own plenty of good SSB radios so it's not a loss. SIX-SHOOTER
|
|
Sandbagger
Administrator/The Boss
Posts: 6,245
|
Post by Sandbagger on Sept 15, 2020 19:56:59 GMT -5
I am going to try an wire it for AM only. If you put it on SSB it blows R60 i believe it was. It goes to the relay. I put it on AM an took the knob off. I am going to see if i can figure it out. When i work on this stuff it is for people that can not afford to send it to a shop. I do not charge to fix it if i can. I do it to also help educate me on this old radio. 238 SSB on a Browning SUCKS anyway so losing SSB is not an issue for me if it was mine.I have owned every Browning base radio ever produced & that includes the SSB models & I found SSB a waste of time & effort on all of them.I own plenty of good SSB radios so it's not a loss. SIX-SHOOTER I am surprised by this. For all of the years back during Browning's heyday, they never managed to build a decent SSB receiver. The BFO on mine drifts horribly. I initially thought that mine had a unique problem. But after talking to other Browning owners, I was told that this is the nature of the beast. I can't believe that a nearly $800 radio could be outdone on SSB by a cheap and dirty Midland or Realistic radio. Granted the Browning was best known for that AM ping and signature audio. But for that same $800, the Tram D201 would have fared far better on SSB.
|
|
mattbee
Mudduck
Tram & Browning Enthusiast :)
Posts: 38
|
Post by mattbee on Sept 16, 2020 6:25:39 GMT -5
Honestly I personally think the SSB on the Browning's was nothing more than a sales-thing, to say they have SSB! In most cases the SSB sucks on them period! Now the Tram's have a much better working SSB circuitry for sure. Actually I enjoy talking SSB on one of my Handwired D201's regularly on the VFO side up on channel 38. Works amazingly well
|
|
|
Post by SIX-SHOOTER on Sept 19, 2020 13:11:21 GMT -5
SSB on a Browning SUCKS anyway so losing SSB is not an issue for me if it was mine.I have owned every Browning base radio ever produced & that includes the SSB models & I found SSB a waste of time & effort on all of them.I own plenty of good SSB radios so it's not a loss. SIX-SHOOTER I am surprised by this. For all of the years back during Browning's heyday, they never managed to build a decent SSB receiver. The BFO on mine drifts horribly. I initially thought that mine had a unique problem. But after talking to other Browning owners, I was told that this is the nature of the beast. I can't believe that a nearly $800 radio could be outdone on SSB by a cheap and dirty Midland or Realistic radio. Granted the Browning was best known for that AM ping and signature audio. But for that same $800, the Tram D201 would have fared far better on SSB. I have owned Three of the TRAM D201 (Hand Wired) & One D201A & all of them were very good on AM & SSB but if I wanted the Best AM transmitted Audio I'd take the Golden Eagle MK IVA but for both I prefer my DAK X & it's why I Sold all of the Brownings & TRAMS.Just my personal choice & many people Hate the DAK X & that's their choice & they have that right. {:>) SIX-SHOOTER
|
|
|
Post by easymoney on Sept 30, 2020 15:02:12 GMT -5
Hello,
I have installed the new mode switch with no improvements.
The fuse will blow shortly after turning the power on.
|
|
|
Post by 2600 on Sept 30, 2020 23:41:41 GMT -5
Disconnect one of the two red wires that feed the B+ section. Shouldn't matter which one.
It's a lot gentler to test a radio with a power-supply overload with a variable AC-voltage transformer, turning it up slowly from zero. Flipping on the power switch to see if the fuse trips risks surge damage to additional parts that were not bad before the overload appeared.
If the fuse still trips with the wire unhooked, you may have a bad power transformer. Could be some previous owner shortened its life with a too-big fuse at some time in the past.
And if the fuse holds and won't trip, put the red wire back and take loose one end of the 250-ohm 10-Watt resistor that feeds into the 3-section filter capacitor. If the fuse trips, the problem is upstream from that resistor. If the fuse holds, it's downstream from there.
73
|
|
|
Post by easymoney on Oct 1, 2020 15:17:06 GMT -5
Disconnected the red wire nothing happens.
Removed one leg of the 250ohm 10% resistor and it popped the 47uf 250v cap and the fuse. The transformer is extremely hot.
|
|
|
Post by 2600 on Oct 2, 2020 22:59:55 GMT -5
Time to check the rectifier, C61A and C62.
Those are the only parts connected to the power transformer's B+ winding when R59, the 250-ohm 10W resistor has one end pulled loose.
Consider that shorted rectifiers can put AC voltage onto the DC-only electrolytic caps. If the old rectifier was close to failure when the new filter caps were installed, it may have finally failed and killed one or two new filter caps.
A shorted cap can damage the rectifier.
A shorted rectifier can damage a filter capacitor.
We got in the habit of replacing the SR2/SR3 epoxy "three legged block" rectifier with two 1N5408 rectifiers. Just as a precaution. Cheaper than the time to properly test the old rectifier. And the 1N5408 has better surge performance, and is less likely to be damaged by a surge later on.
And the 4.7-ohm 1-Watt resistor R64 tends to look overheated and bedraggled after 45 or 50 years. We replace it along with the rectifiers, just as cheap insurance.
73
|
|
|
Post by easymoney on Oct 3, 2020 19:18:03 GMT -5
Thanks 2600 I’ll keep pecking away at it
|
|
|
Post by vanlifeson on Dec 18, 2020 9:42:20 GMT -5
So, uh you're talking about the 6BQ5 modulator tube, right? More than one tube in that radio. We use a 22uf 50-Volt cap from pin 3 to ground, and simply lose the 22 ohm resistor. It was put there to reduce bass response, best I can tell. The original 150-ohm resistor from pin 3 to ground was rated at 1 Watt. We use a 2-Watt part to replace it whether it looks bad or not. Would be a good idea to check R51, a 3.3k 1/2-Watt resistor that has one end soldered to the 3-section 'can' filter capacitor. If it's burned, this is what killed your mike audio. The cause is the breakdown of the mode-selector switch. The brown bakelite plastic degrades, causing that resistor to be fatally overloaded. It's possible to 'hot-wire' the radio and unhook the shorted sections of the mode selector. This makes the transmitter AM only, and disables SSB transmit. Or you can replace the selector. Not cheap. Not easy. Have a look at R51 and see if it looks overheated. 73
|
|
|
Post by vanlifeson on Dec 18, 2020 9:42:55 GMT -5
So, uh you're talking about the 6BQ5 modulator tube, right? More than one tube in that radio. We use a 22uf 50-Volt cap from pin 3 to ground, and simply lose the 22 ohm resistor. It was put there to reduce bass response, best I can tell. The original 150-ohm resistor from pin 3 to ground was rated at 1 Watt. We use a 2-Watt part to replace it whether it looks bad or not. Would be a good idea to check R51, a 3.3k 1/2-Watt resistor that has one end soldered to the 3-section 'can' filter capacitor. If it's burned, this is what killed your mike audio. The cause is the breakdown of the mode-selector switch. The brown bakelite plastic degrades, causing that resistor to be fatally overloaded. It's possible to 'hot-wire' the radio and unhook the shorted sections of the mode selector. This makes the transmitter AM only, and disables SSB transmit. Or you can replace the selector. Not cheap. Not easy. Have a look at R51 and see if it looks overheated. 73
|
|
|
Post by vanlifeson on Dec 18, 2020 9:44:48 GMT -5
Would reducing the value of the 25 µF capacitor increase treble response?
|
|
|
Post by 2600 on Dec 19, 2020 1:19:27 GMT -5
Not really. Will serve to reduce bass response and overall audio gain. Not the same as boosting treble tones.
73
|
|