40-145 speaker issue - Printable Version

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+--- Thread: 40-145 speaker issue (/showthread.php?tid=11811)

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RE: 40-145 speaker issue - OldRestorer - 03-17-2015

Ok from pin 7 of 7Y4 to pin3 of 7B5 it is 500 ohms. From pin 3 to pin 2 of the 7B5 it is 475 ohms.
From the field coil I am getting 1.6K ohms 

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RE: 40-145 speaker issue - Radioroslyn - 03-17-2015

Ok  seems like your P/S is working. Take the screwdriver hold on the metal portion touch the tip of the driver to pin 6 of the 7B5. Should hear hum in speaker when touched.
Terry

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RE: 40-145 speaker issue - OldRestorer - 08-19-2015

Well,
I got the speaker from Mike but NOTHING! I put it in just like the old one and it fit perfectly. It has the same numbers on the cone but different nimbers on the metal. Tried putting the screw driver on pin 6 of the 7B5 and got no hum. The screw driver did clip and I got a good buzz,

When we tested it with another speaker it worked so I dont get it. I cant have 2 bad speakers in a row right? At one point I put the volume real low and I got some music but that was it. I hooked up the antenna and then tried it without it. Tried all buttons, checked the connections checked the tubes, checked out! I am about ready to throw it,
Any ideas?

Me

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RE: 40-145 speaker issue - OldRestorer - 08-20-2015

HELLLLLLLP!!!!

Me

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RE: 40-145 speaker issue - sam - 08-20-2015

heeeeelp
 ahhh mikes not here to help you lol

did you try test speaker before you install mikes speaker or awhile ago ?
recheck wires and solder joints
or could have bad speaker after all it 70yrs old
try taping on to another radio to see if speaker works
miss universe me

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RE: 40-145 speaker issue - Raleigh - 08-20-2015

If you wired it just like before, your "as received" wiring could have been wrong.

Testing the speaker isn't that hard. 10 minutes. I believe you said there are 3 wires soldered to the speaker. Unsolder and remove them from the speaker.

It should only take three tries to find the the field coil if the speaker is good.

-- Connect your ohm meter to any two of the terminals on the speaker. Wiggle the clips to get good contact. 1700 ohms? You've found the field coil terminals. Open circuit? Move to next step.

-- Move ONE of the meter leads to the remaining terminal. 1700 ohms? You've found the field coil terminals. Open circuit? Move to next step.

-- Move the OTHER meter lead to the remaining terminal. Same drill as before. This time if you get an open circuit, you really do have a dead speaker. You've tried all three possibilities. Two combinations should be open and the other should be the field coil at 1700 ohms. If the field coil is fried, you still might get some resistance across the field coil terminals.

-- Mark FC terminals with tape or marker so you won't forget. Bad things happen when people connect this speaker up wrong and put hundreds of volts through the voice coil and onto the chassis.

-- Connect the ohm meter leads between the remaining terminal and the metal frame of the speaker, where the fasteners go that hold it to the chassis. Around 2 to 6 ohms? You've found the voice coil terminal. Open circuit? Bad speaker.

-- Mark the voice coil terminal with tape or marker.

If your speaker is good, you can reconnect it as follows. If not, check again & make sure your meter connections are solid.

-- Find the wire that connects to pin 7 of the 7Y4 AND to the positive terminal of the 12 uF filter cap. If connected to a terminal strip, trace it back until you find these two connections. Connect this wire to either one of the field coil terminals that you marked. Can't find the wires or they are connected to something else? Stop and tell the Phorum all about it.

-- Find the wire that connects to the positive of the other filter cap AND to the black wire from the output transformer. Trace it back until you find these two connections. Connect this wire to the other field coil terminal you marked.

-- The remaining wire should connect only to the output transformer, but it might be soldered to a terminal strip before it gets there. Connect this wire to the voice coil terminal that you marked. [edited to add: if you connect your ohm meter between the end of this wire and the metal of the chassis before you connect it to the speaker, you can see if the secondary of the transformer is good. I'm not sure exactly what the reading should be, but a few ohms is typical. Open circuit? Bad or improperly connected transformer.]

-- Solder the connections.

-- Attach your speaker back onto the chassis. (If you want to test it first, connect the metal frame of the speaker to the metal of the chassis with a test lead. This speaker will not work unless the metal frame of the speaker is grounded to the chassis.)

-- Connect your meter leads to the voice coil terminal you just soldered and the metal of the chassis. 2 to 6 ohms? Your speaker is connected properly. Open circuit? Check ground connection 1st, then all connections as above.

Now you know that your speaker is good electrically and that it is connected to the right wires. If it still doesn't work at all, the fault probably is elsewhere.

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RE: 40-145 speaker issue - OldRestorer - 08-20-2015

Oh boy,
I have homework,

Thanks much for the helpful answer unlike Sam.....

Me

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RE: 40-145 speaker issue - Raleigh - 08-20-2015

Easy homework.

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RE: 40-145 speaker issue - sam - 08-20-2015

Kirk 
in a nut shell same thing as I said 
Check your wires and solder  retry other speaker 
Works then you know  other speaker is bad ohm it out
Same thing just not detailed 

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RE: 40-145 speaker issue - OldRestorer - 08-21-2015

Well I tried the bad speaker on a different radio and got nothing. Tried the new speaker on another radio and got nothing. Hooked up the speaker I know is good and got static from the speaker.

I guess that means both speakers are bad?

UGH!

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RE: 40-145 speaker issue - sam - 08-21-2015

umm all that Raleigh wrote and all you did was swap speakers to test
mmmm     quote   THANKS SAM        in a nut shell
NOW go ohm out speakers and check wires
  ohh I may have 1 or 2 speakers

SAM

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RE: 40-145 speaker issue - Raleigh - 08-21-2015

Depends on how the speakers were supposed to be wired on the second radio. The speakers aren't really interchangeable unless designed to work the same.

If you hooked your suspect speaker up to a radio that uses a different kind of speaker and got silence, it doesn't necessarily prove anything.

If you test step-by-step to find out whether the field and voice coils are good, then we have a starting point to troubleshoot your radio. It isn't that hard. As I said above, it shouldn't take more than 10 minutes with your ohm-meter. It's a max of 3 simple steps to find and test the field coil and one more to test the voice coil. If either the field coil or the voice coil is open or compromised then we know the speaker is bad.

The only other way to check the speaker is to put it into another radio that you know is working that also uses a 1700 ohm field coil (or close to it) and a voice coil that returns to ground through the speaker frame.

Swapping out speakers willy-nilly is a waste of time and could easily damage something. You can swap out the speaker with other radios, but you have to know what you're doing and work carefully. Testing the speaker properly is easier and takes less time.

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RE: 40-145 speaker issue - OldRestorer - 08-22-2015

I have a guest for a few days but I will get to work on this when she is gone.

Me

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RE: 40-145 speaker issue - Kenneth F. Besso Jr. - 08-22-2015

WOW,,,I really surprised about all this,,,,

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RE: 40-145 speaker issue - sam - 08-24-2015

ok kirk
back to work on this

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