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    Dan Walker
    CVRS Member

    They say there are no stupid questions on this forum, but I need some help.
    I have worked on lots of radios but have never tried to inject a signal
    I have an Eico model 324 generator but I DO NOT have any idea of what to set any of the dials
    to or what pins to inject the signal into, and what tubes.
    I mean I know nothing about this so if any of you guys can help me send me an email
    or a PM.
    This will be for my DeForest Crosley radio model 83
    Dan in Calgary

    Les Dickson
    CVRS Member

    Hi Dan. Do you have a manual for your Eico 324 and a schematic for your DeForest 83?

    Ralph Spracklin
    CVRS Member

    Afternoon Dan

    I’m like yourself, this has not been one of my strong areas of expertise. But as a result of your query, I am now learning fast.

    Much written On-line on this subject. The onr thing I will say upfront is always conect to your radio using a Capacitor inline with your Probe. This to keep you from smoking your Signal Generator. Some Signal Generators already have one such Capacitor installed internally in the Signal Generator itself. If your unit has such an internal Capacitor, be certain to replace it, A capacitor around .01-.5 mF will be sufficient. Also as your unit is an older one, make certain it is Calibrated accurately. Your unit is also RF and Audio Frequency capable, so make certain you set it up properly when working on either the Front End or the Output End of the Radio. Hope this information helps.

    Elements of Radio Servicing, below is a good resource. Pages 21-48



    Les Dickson
    CVRS Member

    Hi Dan. i’m not sure if you’ve received the information you need. The information below lists the steps in a generic troubleshooting a radio by injecting signal. I’ve found it quite useful.
    Using Signal Generator to Troubleshoot Radios

    1. You should start your troubleshooting at the plate of the output tube.
    2. Start with the output of the generator turned up just enough to hear the signal with the volume at max on the radio.
    3. You will inject a 400 cycle AF signal into the plate of the output tube,
    4. then the grid of the output tube,
    5. then the plate of the first audio tube,
    6. then the grid of the first audio tube.
    7. If all is well up to this point, and the signal from the generator is heard in the speaker, set the generator to the IF (intermediate frequency) for the radio, usually 455kc. Inject this modulated signal into the plate of the last IF amp,
    8. then the grid of the last IF amp,
    9. and so on until you get to the front (antenna end) of the radio.
    10. Hearing the signal thru the speaker will indicate a normal condition, not hearing it places the trouble between where the signal was lost and the place you last heard it.
    11. You then measure voltages and resistance and figure out what the specific failed component is.
    12. The signal will get louder as you go toward the antenna, due to the additional stages of amplification.
    13. You will need to turn it down at each different test point if everything is working okay. You want to keep the output low during an alignment to keep the AVC system from affecting your alignment.
    14. Turning the output of the generator down during troubleshooting is not so important.
    15. The capacitor that you use with the signal generator hot lead is used to protect the signal generator from the DC power in the radio. The alignment instructions for the radio will tell what value cap to use, but I just leave a .01 at 630 on mine all the time, since that seems to be the most common value. If you use this cap at all times, you won’t damage the generator.
    16. Just as a reminder, PLEASE use an isolation transformer when you work on this radio. Not only will that protect you from harm, but it will be added protection against accidentally frying your generator.
    Dan Walker
    CVRS Member

    Thank you for the information Les.
    I will try to get to this a little later ,as I have some other business to take care of for a day or so.
    Dan in Calgary

    Dan Walker
    CVRS Member

    I guess I should let you know that the out put of this radio works very good
    as I can play the Mp3 player hooked up to the volume control and it plays loud and clear.
    I am attaching the best schematic I have of this radio so you might be able to tell me which tubes to inject the signal into and where.
    With the last instructions I was not quite clear [ LAST If amp ]?????
    I know this is pretty basic for most of you guys, , but I have never done this before.

    Dan Walker
    CVRS Member

    Sorry; Here is a schematic showing the tubes, and various names.

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