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Post by backslider8893 on Jul 9, 2019 19:16:30 GMT -5
Looking for schematic and/or tune and alignment instructions. So far she is running good but low modulation is the main issue. Thanks! Attachment Deleted |
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Sandbagger
Administrator/The Boss 
Posts: 6,247 
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Post by Sandbagger on Jul 9, 2019 21:25:53 GMT -5
Looking for schematic and/or tune and alignment instructions. So far she is running good but low modulation is the main issue. Thanks! View AttachmentLow modulation could be caused by a variety of issues. Could be bad electrolytic caps in the audio chain, or it could be as simple as a bad microphone. Check your receive audio. Does it sound normal, and can you make it blast when you turn up the volume? If not, I would start thinking bad electrolytics. If the volume seems strong, it might be a bad mic, or maybe a mis-adjusted modulation limiter. |
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Post by backslider8893 on Jul 9, 2019 21:54:02 GMT -5
Although the caps probably need replacing due to its age it currently receives and transmits with no problem. I switched mics and it basically sounded the same. I would like to adjust the AMC limiter VR but I don’t know how to identify the exact one without a schematic. It appears that a Diode may have been removed toward the back right corner by the prior owner but according to my Dosy meter the MOD is barely hitting 50% and I believe it’s somewhat accurate because I drove down the road in my mobile and had my son talk to me for a couple minutes. I was able to find and adjust two L coil pots and get a few more watts out of her but the modulation still sounds very plain and somewhat quiet (if that makes sense 😄). My Connex is way louder and crystal clear.
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Post by 2600 on Jul 9, 2019 21:59:58 GMT -5
Mike could be the problem, too. It's old enough to cause trouble. Just one problem. The 4-pin plug on the mike and the socket on the radio are not wired like a modern-day Cobra or Galaxy. We adopted the habit of changing the mike socket in Robyn radios to match a Cobra mike.
Easier than keeping track of a mike wired the old Robyn way so it's handy whenever a Robyn radio shows up.
And if you have a spare mike wired for Robyn, comparing the audio for each mike would be my next move.
The radio is old enough that if you run it for very long with all the old electrolytic capacitors in it, they will fail and cause problem after problem.
73
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Post by backslider8893 on Jul 10, 2019 12:57:22 GMT -5
Thanks for the insight. I did change it out with another Robyn mic but it sounded the same. Do you have any simple instructions on how to change out the mic pin?
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Post by dilbert on Jul 12, 2019 11:43:07 GMT -5
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