[flatheadjr]

I bought this radio a while back and have been trying to repair it I have recapped it and when I power it up all I get is a hum from the speaker. ( After market modern speaker ).  Not quit sure where to start as my schematic has limited information and no voltage references. I'm also not sure on 2 capacitors of a can style that are .5 mfd @ 250V. The schematic shows no polarity. I'm not quite sure where to start.

[Radioroslyn]

Hi Jr and welcome to the Phorum,
Let's take a few voltage measures to see whats what. Pin 4 of the 84 tube to chassis ground. Should see about 220vdc there. Pins 2 and 3 of the 41 tube should also have about 220vdc too. Pin 5 about 8vdc.
The .5 mfd caps are what use to be call paper caps now days we use mylar caps and they are non polarized.

Terry

[klondike98]

Welcome to the Phorum!

[flatheadjr]

No the .5 caps are a metal can type that are mounted to the top of the chassis but my schematic does not show that they are polarized. There is one for sure that is electrolytic and I used electrolytic in that ones place. Maybe I'll have to try and post the schematic to show what I am talking about.

[klondike98]

Link to schematic

[Mondial]

If you are talking about the .5 uF caps marked 54 and 59 on the schematic, then as Terry mentioned they are definitely metal cased paper not electrolytic. These are used for interference suppression filtering. 

In any case, they have no bearing on the actual reception or lack of it, other than to reduce noise from the vibrator supply and car electrical system. 

If you receive no stations and only hear hum, then the problem is elsewhere 

[flatheadjr]

I'm going to check the above mentioned voltages this evening and should be able to go from there. As for the .5 caps I just used caps that were similar in value.

[flatheadjr]

Here's what I come up with, so power going into the rectifier is right around 500 VAC, I'm not sure with pin is #4 but only one read 195 VDC. On the output tube pin 3 is at 195 and 4 at 180, and no. 5 at 3.5 but for some reason I have to flip polarity on my leads to get a positive read out. The radio is 6V positive ground, battery voltage is good and the power wires are not getting hot.

[Radioroslyn]

Ok so far so good! 195V is fine. So pull the cap off of the top of the 75tube and touch the grid connection on the top of the tube. Should buzz like he** from the spkr. Do you have a signal generator?

Terry

[flatheadjr]

No I don't have any fancy electronic testing equipment just a meter for testing. The buzz will come from the speaker right? I'm not going to get buzzed? Haha!

[Radioroslyn]

No I don't have any fancy electronic testing equipment just a meter for testing. The buzz will come from the speaker right? I'm not going to get buzzed? Haha!

If you are into that sort of thing it could be arranged!

>No I don't have any fancy electronic testing equipment just a meter for testing
Suggest you get one here is a few on ebay : http://www.ebay.com/sch/i.html?_odkw=Hea...8&_sacat=0
Wouldn't pay more than $25 for one. If you do get one make sure it has the cable attached to the front (test lead) it will save you the trouble of finding a belly button connector to make up that cable. Don't necessarily need the manual as I think it's on line.

Terry

[flatheadjr]

I'll do that test sometime tomorrow and go from there. What does that signal generator do?

[Radioroslyn]

The short answer is it generates a signal.
It's used to generate a rf (radio frequency) signal so that we can test various stages in your radio and can use it to align the rf and if (read intermedate frequency) stages too.

Terry

[flatheadjr]

So I finally did the test, I removed the wire from the cap on 75 tube and nothing. Its hard to tell if it's a light hum coming from the speaker or if its just some AC noise.

[Radioroslyn]

Ok so measure the dcv on pins 2,3,4,&5 on the 41 tube and on the 75 tube pins 2 and 5. Measure from chassis. Report back. I'm assuming that all tube are lighting up.

Terry