Sapphire I - Audio Troubleshooting Help Needed

[spiritkid]

Hi Volks Folks!

I recently acquired a Sapphire I by Bendix radio for my 1960 Type 1 Beetle and am hoping someone can help me troubleshoot it. I've searched the forums and haven't found an adequate solution to my problem.

Here is a video I made to help demonstrate:


Link

My car has been converted to 12v, and since this radio is 6v, I am using an EMPI 12v to 6v Inline Voltage Drop Resistor. 

For testing purposes, I’m using a fully charged, 12V test battery.

I’m also using a brand-new, correct speaker from Wolfsburg West and have my car’s antenna hooked up. 


The problem:

Radio powers on, but no audio comes through. There is, however, a ~120bpm (or 60 cycle) beating/blinking happening both visually (with the light) and audibly (through the speaker). 

When I turn the volume pot, it produces a scratching noise through the speaker, in addition to a very low-volume hiss unaffected by the pot. I’m not getting any radio static (or stations) with or without the antenna connected. 

I also have the lamp connected to the same side of the voltage drop resistor as the radio’s positive terminal. I realize this would typically be connected to the dash lights, but in my case, what would I do if everything else in the car is 12v? 

As you can see in the video, when it’s all connected this way, the light and pulsing are always happening. When I disconnect the lamp from power, the pulsing only occurs when switching power on, but it also makes the light blink! Shouldn’t the light not work if the lamp wire isn’t connected? 

My multimeter shows that I am getting ~8.25v coming out of the voltage drop resistor. Does this seem right? Shouldn't it be 6v?

I have very basic soldering and electronic knowledge and am doing my best to read the schematic. Hopefully someone here can point me in the right direction of which component(s) might be the issue, or if I'm just doing something obviously wrong!

Thanks!

[Eric&Barb]

[Eric&Barb]

[Eric&Barb]

[spiritkid]

[spiritkid]

[spiritkid]

[Eric&Barb]

[Eric&Barb]

[Eric&Barb]

More threads to read up on:

https://www.thesamba.com/vw/forum/viewtopic.php?t=579130&highlight=radio+shack+reducer

https://www.thesamba.com/vw/forum/viewtopic.php?t=643312&highlight=radio+voltage+drop

Another thought that you should know, that any modern made Chinese voltage reducer might put out so much RF noise that the radio will have a lot of static.
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In Stereo, Where Available!

[zerotofifty]

Radio install and repair manuals Sapphire I radios from the samba technical section



https://www.thesamba.com/vw/archives/manuals/sapphirei_6_1962.php

https://www.thesamba.com/vw/archives/manuals/sapphire_i_5_62_photofacts.php
_________________
Sorry About That Chief.

Give Peace a Chance.

Words to live by.

[scrivyscriv]

It's really common for older electrolytic capacitors to leak out and stop capaciting.. usually losing just one or two will just give you a crappy sound or bad volume adjustments, but losing a handful, or all, will disable all the circuits they're in.

Its such a common repair that the radio guys just refer to it as "re-capping" a radio. Most or all electrolytic caps will be replaced leaving just the original vintage ceramic capacitors, which are non-electrolytic and don't contain any liquid. It's the liquid that leaks or evaporates rendering the capacitor non-functional. Radios have lots of them.

That is most likely what your radio needs. Since you aren't getting any sound at all, at bare minimum the amplifier circuit or tuning circuit is/are defective.
All vintage radios will have this problem, some worse than others. You would need to get a radio guy to recap and address any other issues if you want a functional original radio.

I did avionics for the last two years but I never got too far down into the component level to be of more help than that
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Robert in Memphis
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If you're ever in the Memphis area, you are welcome to stop by for advice and help.

[spiritkid]

Thank you all so much for the thoughtful replies so far. A bit of good news... I connected 4 AA batteries in series to create 6V, wired it to the radio, and BAM, it works! See the video:


Link


Now I am sure the voltage drop resistor is not functioning as I expected. I'll read the threads you linked and see if there is an elegant solution to get this radio working in my car!
[/youtube]

[zerotofifty]

resistor MUST equal to the resistance of the radio in order to cut the 12 volts in half to 6 volts the wattage of the resistor must be high enough to handle the draw that so that it dont over heat a burn out. basically you want half the current to through resistor and half through the radio, you need that half and half balance

also note that a resistor will increase in resistance as it heats up!

so you need the correct resistor. your getting over 8 volts to the radio, so you need a higher ohm resistor to get 6 volt. you want to cut the 12 volt voltage in half. you only cut it by about 1/3 extended use of the radio on high voltage may not be good for it

cause of the heat issue and need to select the correct ohms, these divider resistors are not ideal

in the linked diagrams, your radio is consider one of the two resistors as you run the radio in series with the resistor, that is why the radio and resistor must be same effective resistance, they must draw same watts to cut volt in half at the radio

if you use two resistors and take your radio voltage off a center tap and the two resistor are equal ohms and or high enough wattage, you will get half volts on the center tap BUT to not drain your battery when radios off, you also need to switch the resistors off, with a switch added

using one resistor as you are is the crudest method.

Voltage divider using two resistors, but you need to add the switch , which is not shown...
https://duckduckgo.com/?q=voltage+divider+resistor...iax=images
You need the switch at the input else the resistor will always be drawing load as the long as the battery power is connected. however using a single in series resistor, the switch in effect is the radio on off switch


There are solid state 12 to 6 volt converters for radios, I recommend using them, I have one, installed 45 years ago. these are much better
_________________
Sorry About That Chief.

Give Peace a Chance.

Words to live by.

[spiritkid]

[Eric&Barb]

[spiritkid]

[viiking]

I know this is very messy but why couldn’t you just have a small rechargeable 6V battery tucked away just for the radio? Unless it’s a show car you wouldn’t have to worry about the step down voltage changer.

The ones I see being sold are acid or Lithium based and you could calculate how long the battery would work for say with a 5AH battery.

Or am I stupid for suggesting this?
_________________
1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3

[Eric&Barb]

[spiritkid]