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Author Topic: 1947 Zenith TransOceanic 8G005YT only static after recapping  (Read 27613 times)
K1CJS
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Posts: 6275




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« Reply #15 on: September 06, 2013, 05:02:09 AM »

...BTW, last night I turned it on in a dark room, with the back open. 117Z6 lit up but none of the other tubes even had a glimmer. Any suggestions will need to be made in cave man talk. Sri. abt that. THANKS in advance. Pulled out some of my 1940's radio handbooks, so i can read up on vacuum tube technology.

If that radio is one which the heater filaments are in series, all it would take is one tube with a bad (blown) heater filament to kill ALL the filaments.  Pull each tube one at a time and meter the filaments.  Chances are you'll find the problem.
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W1BR
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Posts: 4179




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« Reply #16 on: September 06, 2013, 08:02:22 AM »

It uses eight locktal tubes, with series filaments. If one is open the radio won't work at all. They are 1.5 volt battery tubes; which means the filaments might just be visible in a totally darkened room. The gettering on the glass makes it even harder to see what is going inside of those tubes regardless.

Pete
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KC5AQO
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Posts: 32




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« Reply #17 on: September 09, 2013, 06:04:32 AM »

The reason for concern on the TR-4 is that on 80 it dropped from 200 to 90 watts on my MFJ 949E in one day. Yes, the antenna is OK. I also tried out my spare set of 6JB6's and got the same exact result. Might send it to a Drake tech, OR, it could be a good education in hollow state technology for me, if I don't use up my welcome here asking for tech help. BTW found 3 resistors on the ZTO that were way out and one burned out resistor. Parts ordered and I will get back to you after installing new ones and retesting. If nothing else works, there's always the 44 magnum option for a cureall Wink. For the radio, not me !!!  THANKS ALL,    Mack Lester
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W9GB
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Posts: 3368




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« Reply #18 on: September 10, 2013, 06:42:06 AM »

Quote
If nothing else works, there's always the 44 magnum option for a cureall .
For the radio, not me !!!
Actually, that comment is insulting.  
It just expresses your lack of patience, or inability to learn how repair radio equipment.
In performing Internet help for 15 years now, I find majority rarely read (literacy issues with technical terms?), have issues with properly reading a schematic, and just desire answer hand-outs.

In the future, if you want help - stick to the Q&A topic you first posted (easier to follow, help for specific topic)
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KC4MOP
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Posts: 960




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« Reply #19 on: September 12, 2013, 04:43:35 PM »

Put in the 117Z6 and checked voltages on the tube sockets. 155 volts which I assume is B+ went to the 2 watt power resistor. Checked several tube sockets 4.5 volts 16 volts,150 volts, and so on but no 1 or 1 1/2 volt readings so the filiment string must be out HuhHuhHuh I will check the resistors tomorrow. Maybe then I can find a problem part. THANKS for putting up with a non-tech w/16 brain cells. Your EXPERT help is really appreciated.   Mack Lester     ps. After this I've got to figure why my Drake TR-4 is only putting out 90 watts max on 80 and 40. It never ends, does it ? Roll Eyes

What is the the Drake supposed to put out?
Don't sweat the small stuff. 90 watts is close enough.
Is this your radio?

http://home.comcast.net/~n9dd/zenithto.html

Are The tubes in the correct positions?
http://www.staff.science.uu.nl/~tel00101/FotoAlbum/RadioCorner/Sets/ZenTO800.htm

This is the scheeezo

http://www.staff.science.uu.nl/~tel00101/FotoAlbum/RadioCorner/Docu/8g005z1.pdf

This is where the rubber meets the road.....
Possible guess that the BATT A.C. switch is in battery?
Filaments are in series so if tube is bad or is not plugged in completely; then the set is dead. Those LOCTAL tubes need to be pressed in good LOCKED for good connection. They were limited design to make the set rugged and not fall out of the sockets.
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W1BR
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Posts: 4179




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« Reply #20 on: September 14, 2013, 07:24:47 AM »

I'd be looking at R19 and R20, which drop the DC voltage for the filament string.

If the switch was in battery, the AC rectifier tube would not have filament voltage and there would be no B+.
But, exercising that switch might be a good idea in case other sections are dirty.

Pete
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KC5AQO
Member

Posts: 32




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« Reply #21 on: September 17, 2013, 03:01:27 PM »

Hello Men,

     Just got back to Eham and saw the latest posts. THANK YOU for the continuing help. I am slowly learning. Will check the rectifier cathode output tonight. Did a caveman test today after putting in the new resistors, and left it on for 30 minutes. The rectifier lit up and was quite hot. The 4 tubes next to it were warm (probably from the rectifier heat. The other 3 on the other side of the chassis were cold, dead cold. SO, filiment voltage must be the problem. I will also check the resistors again that were pointed out. I'm not to lazy to read the schematic, just having trouble understanding the working of it. ALSO, THANKS for the help on my Drake TR-4. Will be on it as soon as this is cured.
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KC5AQO
Member

Posts: 32




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« Reply #22 on: September 17, 2013, 03:08:15 PM »

Hello KC4MOP,

     Sir, thank you for those pages. Big enough to read, a thousand times better than my hard to read one from another site. This is a great help. Mack
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W1BR
Member

Posts: 4179




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« Reply #23 on: September 18, 2013, 07:07:58 AM »

Hello Men,

     Just got back to Eham and saw the latest posts. THANK YOU for the continuing help. I am slowly learning. Will check the rectifier cathode output tonight. Did a caveman test today after putting in the new resistors, and left it on for 30 minutes. The rectifier lit up and was quite hot. The 4 tubes next to it were warm (probably from the rectifier heat. The other 3 on the other side of the chassis were cold, dead cold. SO, filiment voltage must be the problem. I will also check the resistors again that were pointed out. I'm not to lazy to read the schematic, just having trouble understanding the working of it. ALSO, THANKS for the help on my Drake TR-4. Will be on it as soon as this is cured.

Those battery tube filaments draw very little current. The filaments may be visible in very dark room. But, they will not get warm or appear to be working by using the naked eye. They were designed to run off dry batteries for long periods.

Pete
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KC5AQO
Member

Posts: 32




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« Reply #24 on: September 18, 2013, 06:47:32 PM »

THANKS for that info K1ZJH. Didn't know that. The 1LD5 went south during that warm up so Bought another off Fleabay today. Picture showed the tube I bought (hopefully) in a Big tester with the needle way over in the green. Will be a week before I can get the tube. my original tube was barely in the Good on my little 606 when I started. Now all the way in the red.
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