| Author |
Message |
    
Griswald
| | Posted on Sunday, October 26, 2003 - 11:22 pm: | 
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Hey Browning owners,... need some help on this one.
I have a Mark III that when warmed up, the receive goes completely out. No needle movement at all. When I key the radio, or adjust one of the knobs, the receive will come back again for a while then it cuts out again.
I tested all the tubes and found problems with the following:
6BQ5- Bad Emissions
12BY7A- Bad Grid Leakage
7558- Bad Emissions, Weak
12AT7- Shorted
6AQ5A- Bad Life Test
6BE6- Shorted
Besides the tubes being bad, what other things should I be looking for? Could the tubes be causing this problem?
What do I need to do to re-align the radio once I replace these tubes?
Thank you! |
Crafter
| | Posted on Monday, October 27, 2003 - 12:02 am: |
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Use a contact cleaner and spray the channel selector knobs. If I remember correctly the 12by7 is the recieve.
I'll find my owners manual and check on the alignment seems like the is a small silver tuner for the 7558. |
Scrapiron63
| | Posted on Monday, October 27, 2003 - 9:09 am: |
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The tubes and things in the transmitter, like the 7558 will not effect the receiver. I don't have my book handy to see how many of these you listed are in the receiver,but replacing the bad ones in the receiver will probably take care of the problem. The bad 6BE6 is certainly suspect. Have you checked the Nuvistor tubes the little silver ones in the back of the receiver, they are either 6DS6 or 6CW6, both will work. That's a likly problem also. scrapiron |
Griswald
| | Posted on Monday, October 27, 2003 - 1:37 pm: |
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Scrapiron63-
The 6DS4's were good already. Tested good.
Crafter-
What channel selector knobs are you talking about?
Does anyone have the instructions for the tune-up?
Thanks |
Scrapiron63
| | Posted on Monday, October 27, 2003 - 9:38 pm: |
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Griswald, only the transmitter has a channel selector, that would not affect the receiver, it has the VFO. Did you replaced the bad tubes in the receiver, and if so did it help. It could be the relays since its dropping out like that. There are some coils that can be adjusted for the receive, but I wouldn't change them untill I found the intermittent problem. I guess you checked the coax connectors, they are probably 25 years old and could be spread open too much. |
Insider
| | Posted on Monday, October 27, 2003 - 11:05 pm: |
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I have three of the tubes you listed. I have no tube tester and at least one of them is noted as being used. If you want them, e-mail me your address and I'll send them to you. They are:
6BE6
12BY7A
EL84 (same as 6BQ5)
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Griswald
| | Posted on Tuesday, October 28, 2003 - 8:55 am: |
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Insider-
I just sent an email to you.
THANK YOU VERY MUCH!!!!
Copper Forum Members are the best! |
Tech833
| | Posted on Tuesday, October 28, 2003 - 10:58 am: |
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Gris-
First of all, if you have a tube with a shorted element, DO NOT turn the radio on with that tube in it! You may very well damage other components or especially, the power transformer (which would be almost impossible to replace).
I do have the tube types you listed in the storeroom, and I do have a quality tube tester. I would certainly be willing to assist you (I have a soft spot in my heart for tube gear, ask anyone).
HOWEVER, I highly suggest you recap your radio before you continue. The problem is, under your chassis are many wax/paper capacitors. Wax/paper caps have a very high failure rate, especially as they age. The paper used to make these caps contains acid, which is part of the paper purification process, that over time disintegrates the paper structure. Pick up a 43 year old newspaper that has been exposed to high heat and see what happens. When the caps break down, the leakage goes way up, and the caps will eventually short. This will cause failure of all sorts of other components and even your tubes (over dissipation). Miles and miles of text regarding this issue are available on the antique radio nets and forums.
Replacing all the wax/paper caps with modern caps is easier than you think, and will bring your equipment back to better than factory spec operation. Naturally, you will need to realign after recapping. You do not need to realign after simple tube replacement.
Although, most people here credit me with some antenna knowledge, my 'real' area of expertise is medium and high power transmitting equipment. That usually involves tubes. My home contains many antique radios that work. A few get used every day. My 1940 Crosley table radio is on right now.
833 |
de
| | Posted on Tuesday, October 28, 2003 - 7:37 pm: |
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OK this is going to sound strange. BUT here I go....
You could have a cold solder connection. When the unit is cool the solder contracts tightly around the connecting wire and makes contact. BUT when you warm the thing up the solder expands and the connection breaks--radio goes dead.
Try this...When the radio is warmed up and dead open up the top and with a small plastic tube or straw tap each component. USE NON CONDUCTIVE PLASTIC. What you are doing is rattling the connections to jiggle the loose connection into making temporary contact. When you find the loose connection(s)/ there could be more than one / just resolder carefully the connections. I suggest you suck up or absorb the old solder before resoldering. Remember just tap, do not bang the components hard and definately do use something nonconductive to tap.
ALSO you might also get a good magnifying glass and look closely at the soldering. Make sure that the wires soldered to the posts and connectors have good connections as well.
Pe patient and good luck |
Griswald
| | Posted on Tuesday, October 28, 2003 - 8:50 pm: |
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Could the tubes I listed be causing this problem?
I tapped on the relay, nothing happened. I cleaned the contacts too on the relay and put it back in, no change. Sprayed tuner/lubricant cleaner into the ACG RF Gain pot, no change.
Will try the tubes once they get to my house.
de- Thanks for the suggestions as I will try that.
Tech 833- That's good to know that I do not need to re-align if I replace the tubes,...?? Are you sure,... because most people I have spoken to have said that I should,...?? I do have a #79 Sams but no scope or signal generator to perform most of the tasks required to re-align.
Which caps are the paper/wax kind in the Mk III?
Could definitely use your help as it sounds like this could potentially be a major job.
Thank you |
Insider
| | Posted on Friday, October 31, 2003 - 3:43 pm: |
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I may be having trouble with my outgoing e-mail. I sent the tubes out on Tuesday by first class mail. Keep us updated... |
Bigbob
| | Posted on Friday, October 31, 2003 - 8:30 pm: |
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My wife has bad ears,I wish it was as easy to fix hers,oh try freeze spray I think r.shack still sells it it's for finding bad solder joints,works great.But dont get it on hot tubes,POW!Bigbob |
Insider
| | Posted on Friday, December 05, 2003 - 11:05 pm: |
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Griswald, how'd you make out with that radio? |
Griswald
| | Posted on Saturday, December 06, 2003 - 11:03 pm: |
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Insider-
I switched all the tubes out and left the ones that tested good. No change really. Would the keying circuit cause the receive to short out? There is a red wire near to 6AQ5 on the bottom side that seems to have a bad solder. This area in the Sam's photo says audio output but I still can't get the thing to work right.
Thanks Insider, appreciate the tubes. |
Insider
| | Posted on Tuesday, December 09, 2003 - 12:37 pm: |
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Could be relay contacts, or as Tech833 mentioned, capacitor failures. Recaping sounds like a good idea. You may want to ask him or one of the other techs the best way to go about it as they are likely familiar with these radios. I've never seen the inside of one. |
Tech833
| | Posted on Friday, December 12, 2003 - 11:08 pm: |
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You could send it here for a restoration. I admit it would not be cheap, but I have restored quite a few tube radios for discriminating collectors. |
Griswald
| | Posted on Saturday, December 13, 2003 - 12:20 pm: |
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How does one contact you Tech 833?
No email address in your profile...
Thanks |
Tech833
| | Posted on Saturday, December 13, 2003 - 4:18 pm: |
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Just send it to tech833 at copper dot com. |
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