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 Post subject: A different TO 3000
PostPosted: Sep Thu 10, 2020 7:52 pm 
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Joined: Sep Thu 10, 2020 7:35 pm
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Hi, I'm a new member of this forum, I thought that I've used your info enough without being a member that it was time I joined. I bought a TO 3000 several months back, it was totally dead. After replacing the electrolitics and a few transistors I was able to get the FM to work reliably however the AM and shortwave only work intermittently. By intermittently it will work fine if turned on and the band switch was in the AM position but switching to FM or another band and returning to the AM the AM band only has a soft hiss. Many times when this is the condition I can turn the set off and then back on and it works again. I have cleaned the band switch with CRC electronic cleaner and worked it in well but with little improvement. I have checked around for loose contacts around the AM oscillator, checked the AM antenna connections and the like but can not find any problems. Has anyone encountered this condition?
Thanks for any help you can provide Bill.


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 Post subject: Re: A different TO 3000
PostPosted: Sep Sun 13, 2020 2:46 am 
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Location: Black Hills, SD 57745
Possibly. On one of mine, the tabs along the shaft of the bandswitch had worn. This allowed the shaft to rotate some few degrees without actually moving the switch contacts properly. Since the shaft is detented, it would sometimes hit the detent before the contacts made good. This could be seen on a close inspection of the switch action as it was turned.

Rotating beyond a detent, then reversing the knob carefully till it made contact allowed it to work until next time I switched bands.

Cure was to get it in place, then solder the shaft where the pinched/crimped attachments held the shaft to the wafers.

Probably caused by someone rotating the knob too hard past the stops. Something had to give. Kids do such things, don't ask how I know! :roll:
-Ed

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 Post subject: Re: A different TO 3000
PostPosted: Sep Sun 13, 2020 9:01 pm 
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Thanks Ed I’ll check that out.


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 Post subject: Re: A different TO 3000
PostPosted: Sep Sun 13, 2020 9:06 pm 
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Location: Haledon, NJ, usa
Another possibility is the local AM oscillator transistor . 121-350 (2n2089)
The hiss indicates, to me, that the local oscillator isn't running.
Check the components and connections and switch contacts in that circuit.
It may or may not "start" or properly change frequency unless it's started in that band.

Check that circuit.

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 Post subject: Re: A different TO 3000
PostPosted: Sep Thu 17, 2020 9:06 pm 
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Joined: Sep Thu 10, 2020 7:35 pm
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Peter;
Thanks you may have it when the AM cuts out and when I put a known good transitor radio near the TO and tune the TO I don't hear the oscillator sound on the transistor radio.


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 Post subject: Re: A different TO 3000
PostPosted: Sep Thu 17, 2020 11:32 pm 
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Location: Haledon, NJ, usa
bbelin wrote:
Peter;
Thanks you may have it when the AM cuts out and when I put a known good transitor radio near the TO and tune the TO I don't hear the oscillator sound on the transistor radio.

There ya go!

If you have a scope... you can put your probe tip near to the oscillator to see if it's running. Careful... do not actually connect the probe tip to that circuit or it may load it down and kill it too.
Good luck.

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 Post subject: Re: A different TO 3000
PostPosted: Sep Sun 27, 2020 3:17 am 
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Thanks again but no scope.


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 Post subject: Re: A different TO 3000
PostPosted: Sep Sun 27, 2020 4:14 am 
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Location: Haledon, NJ, usa
If your schematic shows voltage test point near or at the LO transistor .... check those.
If they are wrong may be value printed was for actively running osc.
Then try changing that transistor maybe.

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 Post subject: Re: A different TO 3000
PostPosted: Oct Sat 03, 2020 11:02 pm 
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Location: Port Orchard, Wa 98366
Sometimes the Bandswitch fingers have lost there springiness.
So when you move the switch they will not have enough solid contact. You can watch to see if they move up and down which is a good indicator that they are making contact. If your still in doubt then use an ohm-meter to see if contact is either good or bad or flaky.
If your careful and take your time you can adjust the fingers back to original tension. I have used a diddle stick and also a scribe to adjust the tension. The fingers are normally brass or bronze and get brittle with age. Also the rivets may no longer be in full contact with the fingers they hold and support in place. (I claim no responsibility if they get or are damaged :mrgreen: )

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 Post subject: Re: A different TO 3000
PostPosted: Oct Sun 11, 2020 5:06 pm 
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Thanks Radiosmoker


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 Post subject: Re: A different TO 3000
PostPosted: Oct Mon 12, 2020 6:25 pm 
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Location: Palos Verdes, CA
I have a Zenith 3000-1 that would cut-out when I was listening to AM, so I used some contact cleaner on the transistor sockets and it solved the problem. I wish Raytheon hadn't soldered the transistors into my 8TP radios! - Mark


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 Post subject: Re: A different TO 3000
PostPosted: Oct Mon 12, 2020 8:22 pm 
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Be very careful spraying switch cleaner around. Better to spray some into a small container and apply to the contacts with a small paintbrush or q-tip. Too much cleaner soaked into the phenolic of the wafers and it'll be weeks before your radio works properly again.

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 Post subject: Re: A different TO 3000
PostPosted: Oct Wed 21, 2020 8:50 pm 
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Thanks for the advise on the cleaner majoco


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