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Post by highpoint on Dec 26, 2015 18:13:24 GMT -5
Are there any proven transmit audio modifications for both the Browning MkIII and MkIV. I did a search but there isn't much info on these old boat anchors. Searching the web there isn't any concrete mods that are reversible. I did see a mod to disable the audio clipper in the MkIV but not much else. I don't have interest in rack gear or injection, just something to maybe improve the frequency response or increase the modulation %. And as stated it should be reversible. If anyone can steer me in the right direction as far as information I would surely appreciate it. Thank you for your help.
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Sandbagger
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Post by Sandbagger on Dec 26, 2015 19:14:12 GMT -5
Are there any proven transmit audio modifications for both the Browning MkIII and MkIV. I did a search but there isn't much info on these old boat anchors. Searching the web there isn't any concrete mods that are reversible. I did see a mod to disable the audio clipper in the MkIV but not much else. I don't have interest in rack gear or injection, just something to maybe improve the frequency response or increase the modulation %. And as stated it should be reversible. If anyone can steer me in the right direction as far as information I would surely appreciate it. Thank you for your help. Well, the thing about Brownings is that most people who have them collect them and run them as they ran them when they were new 40+ years ago, which means pretty much that stock "Browning sound", so there isn't much interest in modding the heck out of them. That being said, any radio can be modded to give it more power, or less dead key, more modulation etc. But after that's done, it will no longer sound like a legendary Browning, which IMHO is what makes a Browning unique. If it were me, I'd pick up a Galaxy, RCI, Magnum or one of the other popular audio monster radios, and do that up, and run it when you want to hang with the all knobs to the right crowd, and enjoy the Browning the way it was supposed to be run. |
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Post by highpoint on Dec 26, 2015 20:12:40 GMT -5
I am not looking to "mod the heck" out of them. To be honest with you I have stacks of Brownings and other old time radios up to the ceiling in storage. Some are mint, others are in less then perfect condition. They will never be worth anything since they have been modded with everything from soup to nuts. I do my best to bring them back to stock configuration, but cosmetically some are beyond hope with switches and other junk mods. Figured one day I would get around to messing around with them. The day is here. I just wanted to see if there is anything out there worth doing...thank you for your reply.
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Post by cbrown on Dec 28, 2015 10:27:22 GMT -5
A Turner Plus 2 is a good match, as is an Astatic.
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Sandbagger
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Post by Sandbagger on Dec 28, 2015 18:56:33 GMT -5
I am not looking to "mod the heck" out of them. To be honest with you I have stacks of Brownings and other old time radios up to the ceiling in storage. Some are mint, others are in less then perfect condition. They will never be worth anything since they have been modded with everything from soup to nuts. I do my best to bring them back to stock configuration, but cosmetically some are beyond hope with switches and other junk mods. Figured one day I would get around to messing around with them. The day is here. I just wanted to see if there is anything out there worth doing...thank you for your reply. I don't mean to come off like some stick in the mud, pardon me if I came across that way, that was not my intent. Yea, if you have a bunch of Brownings (lucky man!) then some of the more trashy looking ones become candidates to experiment on. Like you said, if they're not in real good shape, they won't be worth as much. But Brownings in good shape can and do fetch upwards of $400 or more depending on exact condition. That's why most avid Browning collectors strive to maintain them in factory stock condition. But depending on your level of technical know-how, there are things you can do to a Browning transmitter to change the way it sounds. Increasing coupling cap in the mic amp and cathode bypass cap values in the modulator stages will fatten up the low frequency response. Experimenting in this area is best done with either an audio sweep generator and analyzer or a variable audio generator and a scope, so you can see what effects you are having. I did a little google searching for Browning mods, and I really didn't come up with much (anything) in a step-by-step format. There has been discussion here in the past about audio mods, the pitfalls of the audio clipper circuit and the following low pass filter, and the effect it has on audio mods. You might be able to search here and find that discussion. |
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Post by highpoint on Dec 28, 2015 23:40:47 GMT -5
Hey, I understand where your coming from. I am into old muscle cars and Lionel trains in addition to radio equipment. I keep everything factory stock as possible. Once you de-virginize something with aftermarket parts or mods it many times becomes close to worthless. People argue this all the time at car shows. There is a certain good feeling you get knowing your Original car is worth ridiculous money compared to the fellow who has the same car with a big blower sticking out of the hood, etc. I know it's all about the fun but what fun is it knowing you threw away your 100,000 car for the sake of being creative, hahahha. Now it's one step above scrap. I at one time had the ultimate collector disease, lol. But in truth I agree with you, the most I would do with a Browning or any other vintage radio is turn up the audio adjustment. Not only that, I mark the original potentiometers position with a sharpee so I can always bring it back to stock. I have a few junkers that most would consider parts units. I got them up and running but they never will be worth anything due to switches, holes, and other strange deviant mods. I acquired these units at the time just for parts units. Since I got them up and running I figured I would have a little fun. Right now I am having a hard time setting the two transmit audio controls on a museum quality Browning MkIVA. One is for sensitivity, the other is a clipper control. I have the alignment procedure, etc. but I want a little more then stock audio out of this thing. Using the original 776 Browning mic, I just can't get a good sound. Either it has to much bass or not enough audio. No middle ground. Strange radio this MkIVA is. In addition I threw in some Telefunken and Mullard tubes and changed out the electrolytics and did a quick alignment. I am sorta new here so now you know where I am at. Not a wise guy or a radio mutation maker. Anyway...thanks for getting back to me. |
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Sandbagger
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Post by Sandbagger on Dec 29, 2015 7:35:25 GMT -5
Hey, I understand where your coming from. I am into old muscle cars and Lionel trains in addition to radio equipment. I keep everything factory stock as possible. Once you de-virginize something with aftermarket parts or mods it many times becomes close to worthless. People argue this all the time at car shows. There is a certain good feeling you get knowing your Original car is worth ridiculous money compared to the fellow who has the same car with a big blower sticking out of the hood, etc. I know it's all about the fun but what fun is it knowing you threw away your 100,000 car for the sake of being creative, hahahha. Now it's one step above scrap. I at one time had the ultimate collector disease, lol. But in truth I agree with you, the most I would do with a Browning or any other vintage radio is turn up the audio adjustment. Not only that, I mark the original potentiometers position with a sharpee so I can always bring it back to stock. I have a few junkers that most would consider parts units. I got them up and running but they never will be worth anything due to switches, holes, and other strange deviant mods. I acquired these units at the time just for parts units. Since I got them up and running I figured I would have a little fun. Right now I am having a hard time setting the two transmit audio controls on a museum quality Browning MkIVA. One is for sensitivity, the other is a clipper control. I have the alignment procedure, etc. but I want a little more then stock audio out of this thing. Using the original 776 Browning mic, I just can't get a good sound. Either it has to much bass or not enough audio. No middle ground. Strange radio this MkIVA is. In addition I threw in some Telefunken and Mullard tubes and changed out the electrolytics and did a quick alignment. I am sorta new here so now you know where I am at. Not a wise guy or a radio mutation maker. Anyway...thanks for getting back to me. The MKIV is usually a great sounding radio with the 776 mic. It's possible that you have a bad mic element or that the gain pot inside the mic is adjusted too far up. You could also have dirty gain pots inside the radio which don't allow smooth adjustment. Generally speaking, I would adjust the clipper to allow maximum modulation first, and then set the gain pots for a decent audio level. Once you achieve that, then I would bring the clipper down to keep max modulation peaks from exceeding 100%. If that doesn't do the trick, try an unamplified D-104. They match up pretty well, and it will not be bassy, that's for sure...... |
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Post by cbrown on Dec 29, 2015 9:29:00 GMT -5
Even an amplified Astatic is a good match on a Mark IVA as long as you keep the preamp levels reasonable. The Turner mics (which is what the 776 is) have a better bass response than an Astatic with a D-104 head.
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Post by highpoint on Dec 29, 2015 21:12:57 GMT -5
I am going to give it a shot this week. I have a station monitor that I am going to put in line to view what's going on. Using a CB meter to gauge modulation is not accurate. Thank you for your help.
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Sandbagger
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Post by Sandbagger on Dec 30, 2015 10:01:30 GMT -5
I am going to give it a shot this week. I have a station monitor that I am going to put in line to view what's going on. Using a CB meter to gauge modulation is not accurate. Thank you for your help. A scope is absolutely essential for experimenting in the audio section. Far more illustrative of what's going on than a simple level meter. You'll do much better with that monitor in line. |
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Post by highpoint on Dec 31, 2015 17:18:18 GMT -5
Haven't had a chance to experiment this week. Thanks again for getting back to me. To you and everyone else on this site...Happy New Year! |
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Post by cbrown on Jan 5, 2016 9:52:15 GMT -5
Same to you!
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Post by BBB on Dec 5, 2016 12:11:52 GMT -5
Mark IV, IVA and Mark III HiFi mod/ direct inject.
Saw this posted else ware. I can not confirm this was successful nor have I ever performed this HiFi mod. It is just information by others that may or may not be useful:
Browning Mark 4 and 3 HiFi mod from Night Crawler:
To bypass the clipper refer to the schematic for the Mark 4 Transmitter.
1. Remove V204 the 12AU7 that tube is used for the clipper.
2. Find C220 and L601 on the schematic locate those parts in the transmitter.
3. Disconnect the end of C220 that's connected to L601.
4. Connect that end of capacitor C220 to pin 2 of of V204 the 12AU7 after the tube is removed.
5. Do not reinstall the 12AU7
The clipper is now bypassed also C213,214 and C215 can be changed from .001uf to .01uf for more low frequency response.
If you want to inject the audio directly to the modulator instead of connecting the one end of C220 to pin 2 of the 12AU7 connect it to your rack gear.
Question: "Would I need more output from my rack if I direct injected the audio? I see that would be bypassing the 12ax7 which is the pre amp tube if I'm not badly mistaken. Would I need more output from the rack gear to drive the 6bq5? Thanks again for our help. Oh yeah also clipping c220 before or after the point that it goes to c219? Would I need more output from my rack if I direct injected the audio I see that would be bypassing the 12ax7 which is the pre amp tube if I'm not badly mistaken."
Answer: “Yes you would.”
You can inject the audio from the mixer into the 12AX7 through the mic jack but the inter-stage coupling capacitors C213,C214 and C215 determine the frequency response of the microphone stage those can be changed to a .01uf or a .05uf to improve frequency response.
Try it both ways and see what works best for you, also R219 will be your mic gain control and R603 the clipping control will not longer function after the modification.
Clip C220 before C219.C218,C219 and L601 are used for the high frequency filter for the clipper so you don't want anything connected to that circuit.
Observation: "My friend Marc asked me if his Browning Mark 3 transmitter would be a candidate for high fidelity audio on AM. The Mark4 uses the same audio amplifier circuit. After reviewing the schematic, it looked encouraging, for one thing the transmitter is plate modulated. The first thing in order was to sweep the audio chain and a Step response with a audio function generator. Looking at the audio response at the output of the transmitter with a scope. The stock response was 400 to 2800 Hertz with phase and amplitude distortion, this is telephone quality. The first two audio stages use a 12AX7 which are straight forward. The 3rd and 4th audio stage is a voltage clamper circuit. This limiter circuit clips the input signal which distorts the audio signal and produces odd order harmonics. Which is then put through a low pass filter to remove the harmonics and have a so called reconstituted signal. The final drive stage uses a 6BQ5. By making a few simple changes to the 1st, 2nd and driver stage and eliminating the clipper circuit and reducing the equivalent capacitance across the secondary of the modulation transformer. This will greatly improve fidelity and eliminate distortion of the transmitter. To my surprise the modulation transformer frequency response is quite good. The low end does suffer a bit because the Modulation Transformer lacks inductance but remember this was designed for communication audio. Output response was 60 to 15,000 Hertz (-3DB) with low distortion. I might still incorporate a loop of negative of negative feed back from the secondary of the modulation transformer to a earlier audio stage to see if any further improvements. I also have provided a line level input so you drive the transmitter directly from a audio chain. I do have wave file to demonstrate the results. The phone jack output from the receiver was feed directly into digital recording"
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Post by KneeBiter on Dec 5, 2016 18:27:11 GMT -5
I can confirm this does work. Not only did I do this mod to one of my mkiv's but I also replaced the factory modulation transformer with a vintage 25 watt multimatch Thordarson. The audio is unreal. When I talk on that radio everyone I talk to compliments the audio. I never ask. They just comment. I always hear :IT SOUNDS LIKE BROADCAST QUALITY" also "IT SOUNDS FULL" I do not direct inject. No rack. Just a vintage stock unamplified D104. If I switch to my stock mkiv without saying anything they tell me it sounds tinny compaired to how it did sound. One thing with changing out the mod trans you loose the modulation meter. I have a couple of extra Thordarson MOD transformers and thinking of playing with other radios to see what happens.
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Sandbagger
Administrator/The Boss
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Post by Sandbagger on Dec 5, 2016 19:33:55 GMT -5
I can confirm this does work. Not only did I do this mod to one of my mkiv's but I also replaced the factory modulation transformer with a vintage 25 watt multimatch Thordarson. The audio is unreal. When I talk on that radio everyone I talk to compliments the audio. I never ask. They just comment. I always hear :IT SOUNDS LIKE BROADCAST QUALITY" also "IT SOUNDS FULL" I do not direct inject. No rack. Just a vintage stock unamplified D104. If I switch to my stock mkiv without saying anything they tell me it sounds tinny compaired to how it did sound. One thing with changing out the mod trans you loose the modulation meter. I have a couple of extra Thordarson MOD transformers and thinking of playing with other radios to see what happens. The "vintage Browning sound" is somewhat bright and high end emphasized on an unamped D104 or the old banana mic. When you have a low end that rolls off at 400 hz, there's not enough bottom end for a full rich sound. I'm torn. On the one hand, I like HiFi audio, but I also like keeping my vintage radios as close to stock as I can. If I someday find another Browning, I might play around in the audio circuit and see what I can get out of it. |
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Post by KneeBiter on Dec 5, 2016 20:38:06 GMT -5
Im with you on keeping it stock. I really like my stock MKIV'S. I had the parts here and had several mkiv's so figured I would play around. The modded mkiv is now my favorite radio. And nothing has been done that cant be removed and put back to normal in 45 min or less
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