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 Post subject: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Tue 15, 2020 1:20 am 
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Location: Panama City, FL 32401
I have a D7000Y that works fine on batteries. Just bought the power cord for it. Is it safe to apply ac, or are there any electrolytics I should check first? Has anyone who has run this radio on ac experienced any hum on the bands? Thanks!


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Tue 15, 2020 6:50 am 
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Joined: Mar Tue 27, 2012 1:24 pm
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I know very little about the 7000, but the 3000 is susceptible to thermal runaway on the final transistors if you use AC adapters.

Usually I stick with batteries on my transistors for that reason.

Like I said, the 7000 may be safer to use with an AC adapter. I'm sure one of the people who know more about Zenith TO's will be able to say so.

I just posted this because I was lucky -- my 3000 shut itself down, and luckily it worked again. On batteries.


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Tue 15, 2020 1:49 pm 
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Joined: Nov Wed 07, 2007 12:44 am
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Location: Kingman, Arizona
The D7000Y AC power supply has a 500uf electrolytic cap which by now is probably leaky and should be replaced. The AC power supply is mounted in the back cover which is easily removed to access the power supply. I use 470uf 50 volt caps for replacements. Harry


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Tue 15, 2020 7:36 pm 
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Thanks to you both, that's very helpful and informative. Think I'll hold off using it on ac until I find out more about this. Since everyone seems to use these on batteries maybe that's why.


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Wed 16, 2020 3:41 am 
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Joined: Aug Wed 24, 2011 4:35 am
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Location: Sunnyvale CA
Zenith Royal wrote:
I have a D7000Y that works fine on batteries. Just bought the power cord for it. Is it safe to apply ac, or are there any electrolytics I should check first? Has anyone who has run this radio on ac experienced any hum on the bands? Thanks!


It runs fine on AC, I would just hook it up and plug it in, and have done so many times. As noted there is a 500MFD electrolytic cap across the power supply, that is the one that routinely loses capacity and causes hum. I have seen a couple of them that have blown up and left plastic shards inside.

Just remove the back and it is right there. A possible source of problems is the changeover switch, clean that with contact cleaner while you are in changing the capacitor.

On AC, there is no detectable hum if it is working correctly, but there is a slightly higher background noise level that doesn't exist on the radios that use wall-wart type AC, like the 1000 series and 3000 series, which seem to have absolutely no difference between AC and battery. I attribute that to the proximity of the diode to the rest of the electronics, because making the capacitor much bigger - like 12000 mfd - doesn't change anything.

Brett


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Wed 16, 2020 4:39 am 
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Location: Panama City, FL 32401
Thanks for the info Brett. I do have a 25v 500uf electrolytic I could use. Don't have the power cord yet, it's most likely tied up somewhere in the mail. The seller on Ebay makes them himself, and guarantees them to work, even tests them on his own T.O. Very reasonable price too. BTW: owners of the R7000 should be aware that model does not use the same power cord.


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Wed 16, 2020 8:55 am 
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Joined: Aug Wed 24, 2011 4:35 am
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Location: Sunnyvale CA
Zenith Royal wrote:
Thanks for the info Brett. I do have a 25v 500uf electrolytic I could use. Don't have the power cord yet, it's most likely tied up somewhere in the mail. The seller on Ebay makes them himself, and guarantees them to work, even tests them on his own T.O. Very reasonable price too. BTW: owners of the R7000 should be aware that model does not use the same power cord.


Right, I think the R7000 uses a standard shaver cord, but Royal 7000 series (7000-1, 7000-2, D7000Y) use one that is custom and just a bit smaller. I have seen plenty of them with the pins bent were someone shaved down a, er, shaver cord to fit in the hole, and then forced it on.

500mfd/25V will be fine.

Brett


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Wed 16, 2020 9:11 pm 
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Location: Ashhurst, New Zealand
Renton481 said:
Quote:
but the 3000 is susceptible to thermal runaway on the final transistors if you use AC adapters.


Many people and I have said on this forum that you shouldn't run a 3000-1 on a "12 volt" AC power supply unless of course it's a proper regulated device. The 12 volt wall wart will give out 12 volts if you a sucking the rated current out of them but as the radio only takes about 25mA max the output voltage can be as high as 16volts. I use a 9volt 200mA supply and it works well.

_________________
Cheers - Martin ZL2MC


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 Post subject: Re: Running a Zenith Royal D7000Y on ac power
PostPosted: Dec Thu 17, 2020 3:08 am 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 5359
Location: Sunnyvale CA
majoco wrote:
Renton481 said:
Quote:
but the 3000 is susceptible to thermal runaway on the final transistors if you use AC adapters.


Many people and I have said on this forum that you shouldn't run a 3000-1 on a "12 volt" AC power supply unless of course it's a proper regulated device. The 12 volt wall wart will give out 12 volts if you a sucking the rated current out of them but as the radio only takes about 25mA max the output voltage can be as high as 16volts. I use a 9volt 200mA supply and it works well.



Yes, I was going to say something but decided to let it go - the radio doesn't care where the DC comes from. It does care if it is >12v. Otherwise it is no more prone to issues on AC than DC. I use 2 amp 12v regulated power supply originally intended for some sort of HP computer gadget, but the current is more like 15-20 mA, So, almost any 12V unregulated supply will go far over, because it counts on the rated load to hit the output voltage.

Brett


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