Couple of questions...

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Couple of questions...

Post by mushroombrew on Sun Sep 06, 2009 12:05 pm

This doesn't relate to my previous post, so I started a new one. Firstly, I've been going to the schematics quite a bit for the Moto 6y radio, and I'm a little confused. There are many resistors on it that for instance say "470MOhm". I would [i]assume that means "megohms", but the resistor color codes and ohm meter read out to be Kilohms. What terminology are they using to come up with that? Reason I ask is that this radio is a family heirloom and I dont want to mess it up and the previous repair person was not interested in making anything easy for me.

Secondly: I don't have a tube tester, nor can I afford one right now. I don't even get enough radios to justify the purpose of buying one. Furthermore, some of these tubes cost 20-30 bucks apiece, so I don't want to randomly buy new ones if I don't need to. Is there anybody out there that would test them for me if I mail them to you? There are 6 tubes and they are all octal base. Two have a top terminal. I'll be happy to pay you for your trouble.

Thanks in advance.

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Re: Couple of questions...

Post by Resistance is Futile on Sun Sep 06, 2009 1:56 pm

Have you replaced the Caps?
As far as the resistors go, go by the color code on each. Only replace the ones that are out greater than 20 %.
The tubes are better staying with you. If they light then thats Half the battle. If you ship them you may never get them back unless you can trust the person. You can get a used Jackson tube tester for about the same price. Just make sure you test it first. They can be had at Ham-fests and swap-meets for $10- 25. Find a local Ham club, they can be found by listening to the local ham frequencies on 2 meters, even if you only have a handheld scanner. These Guys are always getting together to exchange equipt and radios and a lot are into antique radios.
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Re: Couple of questions...

Post by mushroombrew on Sun Sep 06, 2009 2:12 pm

I have replaced the caps. The problem now is that I only get a very faint hum from the speaker and the 6v6-g output tube is being overvolted by about 40 volts on the plates and it hits about 300 degrees in a couple of minutes. Somebody in the past did some recapping and was using the old filters in combination with incorrect new ones. The also replaced some of the film caps with incorrect ones and completely removed two resistors including a 2-watt one. Point being, I cant trust anything he did. I just want to do a good job on this radio and I wanted to eliminate the possibility that any of the tubes, especially the 6v6, is bad. I won't be turning it back on until I get the repairs under the chassis completed. Also, I have a grundig s350dl radio, which does go through the 2 meter band, but it doesn't have ssb reception, so I can't hear any hams... Thanks for getting back with me on that. Oh, and BTW, the telephone wire thing in the other post that I mentioned... It was this radio. Suspect

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Re: Couple of questions...

Post by Resistance is Futile on Sun Sep 06, 2009 4:15 pm

Sounds like somebody on a tight budget did the repairs.
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Re: Couple of questions...

Post by VANT on Tue Dec 22, 2009 10:09 am

Most old timers in the repair business will tell you that you really don't need a tube tester. All you really need a good multi meter and a copy of the rca tube manual. There are some real good tube testers out there and then there are some that don't test all the different functions a tube has and can give you a false positive. Keep in mind that a tube tester is just like any other piece of old technology and needs to be "recapped" and made sure it too is working properly.
---Vant
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Re: Couple of questions...

Post by sprman on Tue Dec 22, 2009 10:18 pm

Hi you can get tubes cheap at radio swap meets.I have gotten boxes of tubes for $20.00 and they are not TV tubes.Get to hamfest and swap meets .6V6s will run hot as will 6K6,6F6,6L6 tubes.Check and se what your line voltage is.I uses plus ,minus 20% on voltage and resistance unless they say diffrent.Todays meters will read better than the old ones.Ithink at most a 6V6 will have 350 volts as max limit,check a tube book or google it.Sprman : )

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Re: Couple of questions...

Post by Resistance is Futile on Fri Dec 25, 2009 12:43 am

Just to let you know 2meters is FM so no sideband needed Wink
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Re: Couple of questions...

Post by rojoknox on Sat Jan 16, 2010 3:27 pm

Greetings from FixitLand!

mushroombrew wrote:...I've been going to the schematics quite a bit for the Moto 6y radio, and I'm a little confused. There are many resistors on it that for instance say "470MOhm". I would [i]assume that means "megohms", but the resistor color codes and ohm meter read out to be Kilohms. What terminology are they using to come up with that? Reason I ask is that this radio is a family heirloom and I dont want to mess it up and the previous repair person was not interested in making anything easy for me. ...

There are some old schematics that use 'M' for 1000 (the Roman numeral for one thousand). There aren't too many 470-megohm resistors used in radios, so if you see such an apparently gargantuan value in a schematic you can figure they mean 470,000 or 470 k. (Some RCA schematics dispense with abbreviations altogether and show the full numeric value!)

On a related note, you'll often see "mmf" -- micro-microfarads -- on capacitors. The equivalent term "picofarad" didn't come into use until the late 1950s.

Take care,
--
J. E. Knox 'The Victor Freak'

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