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 Post subject: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Sun 06, 2020 11:31 pm 
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Joined: Sep Sun 06, 2020 10:14 pm
Posts: 7
My faithful radio has developed an odd problem. After 5 minutes of playing FM using the AC adapter it starts emitting a regular pattern of five thumping sounds on all bands. At first, I thought it was an intro to a techno song, lol. If I shut it off for a few minutes it plays fine and then starts thumping again.
It does not do this on battery power.
Any Ideas? I realize it is hard to diagnose from a post.
Probably would not be a bad idea to take it to a shop for an overhaul. I'm electronics challenged. I see there are a number of repair shops recommended on the Southern California Antique Radio Society forum. Would it be helpful to find one specializing in this particular radio? Is there someone here that can recommend a shop near Long Beach, CA?
Thank you.


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Sun 06, 2020 11:47 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17969
Location: Utica, NY 13502 (USA)
My fist thought would be a bad filter cap in the AC adapter causing the radio to go into a slow-speed oscillation sometimes known as "motorboating".

Dave


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 12:23 am 
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Joined: Sep Sun 06, 2020 10:14 pm
Posts: 7
I'll try a different adapter.


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 12:42 am 
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Joined: Sep Sun 06, 2020 10:14 pm
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That seems to have solved the problem. Never seen an adapter go bad before.


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 12:52 am 
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You know, I just got to thinking. I dropped the adapter yesterday from about two feet. Must have done it in.


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 2:45 am 
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Joined: Sep Sun 06, 2020 10:14 pm
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Dave Doughty wrote:
My fist thought would be a bad filter cap in the AC adapter causing the radio to go into a slow-speed oscillation sometimes known as "motorboating".

Dave

I have an another AC adapter with 12V 1.5A output. Would 1.5A be too much?
Thanks


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 3:43 am 
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Joined: Feb Thu 06, 2020 3:42 am
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Wnen powering radios from external supplies one must be careful of the actual voltage the wall wart puts out . Just because it says 12 volts does not mean anything unless it is regulated. Most 12 volt supplies output is probably on the order of 15 or 16 volts the load of the device connected to it drops it to a safe value. A TO 3000 draws approx 25 to 50 ma a 1.5 amp power supply would stress the radio unless it is regulated. USE BATTERIES AVOID PROBLEMS!


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 12:59 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17969
Location: Utica, NY 13502 (USA)
A 9-volt, unregulated wall-wart supply rated at 250 ma or more will provide the correct voltage to operate a Royal 3000-1.

Dave


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 1:01 pm 
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billk wrote:
USE BATTERIES AVOID PROBLEMS!

Sounds like a sound suggestion. And I appreciate the Ma info.
My other TO 3000-1 will only operate on adapter. I have swapped out the battery tray so I eliminated that as the problem. I do not see anything loose. Is there something a novice could also check? Any guesses on what might have gone wrong?
Sorry, I don't mean to morph this thread into another topic but it is kinda related.


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 1:10 pm 
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Dave Doughty wrote:
A 9-volt, unregulated wall-wart supply rated at 250 ma or more will provide the correct voltage to operate a Royal 3000-1.

Dave

This is an interesting comment. I have an adapter with step down voltages. I usually use the 12V setting and the radio plays loud and clear. I tried switching to 9V and the radio output was garbled and low.
As you know, the battery tray holds a total of eight 1.5V batteries making up 12 volts. If the radio will operate fine with 9 volts why didn't the designers make the tray to hold 6 1.5V batteries? Just curious.


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 1:29 pm 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 5166
Location: Sunnyvale CA
Poche wrote:
Dave Doughty wrote:
A 9-volt, unregulated wall-wart supply rated at 250 ma or more will provide the correct voltage to operate a Royal 3000-1.

Dave

This is an interesting comment. I have an adapter with step down voltages. I usually use the 12V setting and the radio plays loud and clear. I tried switching to 9V and the radio output was garbled and low.
As you know, the battery tray holds a total of eight 1.5V batteries making up 12 volts. If the radio will operate fine with 9 volts why didn't the designers make the tray to hold 6 1.5V batteries? Just curious.



In Dave's case, the 9V 250 mA wall wart probably puts out around 12-13V at the ~15-20 mA required. Unregulated supplies count on the output current dragging the output down to the rated voltage. Run it at less than the expected output current (in this case, 1/10th or so of the intended current) and the voltage floats high. If you tried the same thing with a 12V 250 mA wall wart, it might run at 15V on a Royal 3000, far too high.

I run a 12v 1 amp *regulated* supply, it puts out around 11.9v regardless of load.

Brett


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 Post subject: Re: Zenith TO 3000-1 Odd Problem
PostPosted: Sep Mon 07, 2020 4:27 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17969
Location: Utica, NY 13502 (USA)
Poche wrote:
Dave Doughty wrote:
A 9-volt, unregulated wall-wart supply rated at 250 ma or more will provide the correct voltage to operate a Royal 3000-1.

This is an interesting comment. I have an adapter with step down voltages. I usually use the 12V setting and the radio plays loud and clear. I tried switching to 9V and the radio output was garbled and low.
As you know, the battery tray holds a total of eight 1.5V batteries making up 12 volts. If the radio will operate fine with 9 volts why didn't the designers make the tray to hold 6 1.5V batteries? Just curious.
What is the output voltage of your supply both with and without the load of the radio connected? Perhaps your power supply's switchable voltage output is regulated, not unregulated. I was talking about a typical plug-in, single voltage, unregulated wall-wart.

I'd also recommend measuring the operating current drawn by your radio.

Dave


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