Newbie with schematic issues

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Newbie with schematic issues

Post by truetone on Sat Oct 12, 2013 1:01 am

Hello everyone,

I replaced all of the condensers and not sure about resistors. R5 and R8 both state megohm.  For example what does R1 20M indicate? mega or milliohms. Please look at pic.

Second question is about dog bones.  Would this be considered brown, red, red  and the silver/gray is 10% tolerance?

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Any help would be greatly appreciated. Also any recommendations on tube radio for beginner would be wonderful.

Thanks,
C

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Re: Newbie with schematic issues

Post by 75X11 on Sat Oct 12, 2013 9:08 am

The resistor values will be expressed as M (mega) or K (kilo). Your component appears to be a red red silver wich I believe would be 22 with a 10% tolerance. Check your parts list to confirm. If it has a component that lists as a 220 and no 22's present, that would probably be it. Usually only capacitors or inductors will be expressed as milli or micro.
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Re: Newbie with schematic issues

Post by 75X11 on Sat Oct 12, 2013 9:13 am

Here are some extra sources that may help with other variations.

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Re: Newbie with schematic issues

Post by CrazyCanuck on Sat Oct 12, 2013 11:54 am

75X11 wrote:The resistor values will be expressed as M (mega)  or K (kilo).
Except that in many older schematics the "M" value represents "thousand", so "200M" will actually be 200,000 (200k) ohms. How can you tell when your schematic is that type? For schematics where"M" means "k", the megohm values will often be shown in text "megohms", not with a single letter "M".

CC

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Re: Newbie with schematic issues

Post by Bill Cahill on Sat Oct 12, 2013 1:12 pm

That is definately an older set, and, M in this case means K ohms. 200 M, therefore, means 2000K ohms.
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Re: Newbie with schematic issues

Post by Wildcat445 on Sat Oct 12, 2013 3:37 pm

Welcome to TRF. We have lots of helpful people here.

Regards

WC

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Re: Newbie with schematic issues

Post by truetone on Sat Oct 12, 2013 9:08 pm

Thanks for the info about "M". I just ordered a used copy of Elements Of Radio Servicing. Everything at the local library was on modern radio repair.

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Re: Newbie with schematic issues

Post by Ragwire on Sat Oct 12, 2013 11:54 pm

Welcome!
I have that same book, and I think you'll find it both helpful and interesting. That M for K business threw me off a few times, too, until I noticed a lot of resistor values would have been many, many megohms...more resistance than I had ever seen or even heard of in a typical radio circuit. 10 megohms is typically the highest resistor value you might see in tube radios, and that is even high. 6.8 or 3.3 megohms are fairly common, with resistance from a few hundred thousand ohm to 1 megohm being in a lot of circuits. There are a few low values like 100 ohms in the tube cathode circuits, many times.

Until you get your paper copy, here is a link to the book on pdf for free. [You must be registered and logged in to see this link.]
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Re: Newbie with schematic issues

Post by jerryhawthorne on Sun Oct 13, 2013 6:45 pm

Just to clarify and not have any confusion I do believe Bill made a typo on this response. A resistor listed as 200M in the old convention would be actually in the new convention 200K, not 2000K.
Regards, Jerry

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Re: Newbie with schematic issues

Post by Bill Cahill on Sun Oct 13, 2013 7:21 pm

OOps. ONe zero too many. Thanks. Yes. It was a typo.

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Re: Newbie with schematic issues

Post by Ron Pond on Mon Oct 14, 2013 9:06 am

<Second question is about dog bones.  Would this be considered brown, red, red  and the silver/gray is 10% tolerance?">

Correct.

Body, end, dot is the order in which dogbone resistors are read.

Therefore, if the resistor pictured has a brown body, a red end and a red dot with the other end silver, it is a 1200 Ohm resistor with a 10% tolerance.

Looks more like an orange body in the pic to me, which would make it a 3200 Ohm resistor.

The silver on the other end is its tolerance;
No colour = 20%
Silver = 10%
Gold = 5%
Red = 2%
Brown = 1%

This was the industry standard, however some radio manufacturers used their own colour code system which was different to the above. Atwater Kent comes to mind here.

Ron.
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