Hi. I have completed a wiring diagram of the radio I bought so everyone can give some opinions. I'm not a draftsman so be kind & needs tidying up but. you'll get the idea

I have these three vintage radio resistors two carbon I think and one dog bone. I would like to know if someone can tell me how to read these older resistors correctly and what size are they? Yes, I do know how to read the resistor code charts but, I'm confused as to which end of the resistors to start.

What is suggested to use instead of a vintage voltage dropper? If details are required please let me know. Photos attached. Much appreciated.

Thank You.
Hammer_651

Hi Hammer_651, I assume the photos are coming, I do have a chart for how to read the "dog bone" type resistors, I will try and find a link.

With the dog bone type if I am not mistaken it is. First digit is the body colour, second is the colour at one end and the dot in the middle is the multiplier. In relation to the wattage rating, it is size dependent, the larger in both length and diameter that larger the rating. I am sure the chart gives some dimensions and power rating numbers.

That is my recollection, I will try and find the chart or you can do a search on the internet.


George

Old resistor code goes "Body - End - Dot"

Body is 1st digit, end is 2nd digit, dot is the no. of zeros that follow.

Example: A green resistor with a black end and an orange dot is 50K ohms (or should be!)

If you have some idea of what the radio is, there may already be a circuit diagram in existence.

I use an ancient AutoCad to draw reverse engineered sets, plus a few other things.

Chart here: http://www.archradioclub.org/dogbone.jpg

Hi all. I thought I emailed the pics but they didn't go for some reason. I have emailed them again.

Hammer_651

Vintage User,

A couple of things:-

1. When sending pictures it is very important to include your username and the full title of the thread, otherwise it is very difficult for me to find the correct post to link the photos to.
2. Please always send photos in JPG format. I can't upload videos and only just managed to find out today what a HEIC file was and how to open it up.

I will upload the photo sent tonight, which shows the underside of the chassis.

Hi Brad. My apologise. I wasn't aware of this file been different it's from an apple phone. I'll check them and change and resub,itt if that's ok.
Thanks again.
Hammer_651

G'day Hammer,

No need to apologise - we are all new at one stage. I've uploaded the photo which originated as a HEIC file, but I would need you to make stills out of the two videos if you can.

Thanks for the photos. I can see immediately that the resistors in question are a pair of 500k (which have probably gone high), and a 100k on the right hand side of the photo.

The dropper on the left side is unknown, as they are often not marked. They tend to go open or become intermittent.

Please check those 500k resistors, as they can cause grief to the output valve.

Apple have a habit of their "walled garden" approach, in this case using their own formats for pictures. There should be an option (so i've heard) of using JPG as a more common format instead. I don't have one of their phones.

Is it possible to get a picture of the top of the chassis?

If you want to stop the mains cable twisting use a gland pointy end in. I still put a tie on the inside to help it from not being pulled. SC had trouble realising that, & think the clamps are to small.

The mains earth wire's first point of contact should be to the chassis. Firmly secured with a nut, bolt and star washers. Yours appears to go to the transformer.

Excellent work on the new images. I have made the 4th one a hotlink to a PDF version of your circuit diagram so it can be enlarged to make it easier to read. Just click on that image to access the PDF.

Hi all. Thanks for your input it's greatly appreciated.
Unfortunately Marcc I do not have a schematic or model or make just a chassis, thanks for your advice too. The supply is just a temporary thing for now.
Jacksprat. Yes it does, I'm aware of earthing after 50yrs in electrical trade, it's a temporary connection.

Robertt, I will attach a pic of the top of the chassis for you. Thanks.
I do have a copy of the dog bone resistor detail and now thanks to you all I have more info.
Thanks.
Paul.P.
Hammer_651

Hi Robertt. I have attached a pic of the top of the unknown chassis for all to see.
Hammer_651