You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

Ok, make sure the AM power can be adjusted. If AM power can't be adjusted - then the entire issue may be with the regulator itself TR36 - it mixes Bias and audio and feeds the Darlington pair.

As you said and I do agree - a cap or rising voltage somewhere is pinching off the audio.

You had front end (panel) damage - so just about anything goes - even poor ground or a cap shorted and voltage leaks past. (Like the PA - bias can feed into the mic line but it would more distort audio than pinch it off (600 ohm dynamic))

One area that has a cap that gets goofy, is the Mic amp itself - it uses a 100uF 10V and there is also a line filter cap C109/C180 that is a 220uF cap over by the 7808 voltage regulator/Audio amp heat sink flange.

But also - if any works' been done or the damage up front passed into the rear panel in the AM regulator section - this crops up to - no regulation - audio dies too...

So check AM regulator see if any cracks or even shattered diode glass from bending of the board - like a sudden impact - I can see this happening along a side rail...Mic and AM regulator share same side..there is that network back there that feeds in - so if you have carrier great, but if theres' no regulation theres' no audio...
You've got your hands full...

<blockquote data-quote="Handy Andy" data-source="post: 634548" data-attributes="member: 52309">Ok, make sure the AM power can be adjusted. If AM power can&#039;t be adjusted - then the entire issue may be with the regulator itself TR36 - it mixes Bias and audio and feeds the Darlington pair.As you said and I do agree - a cap or rising voltage somewhere is pinching off the audio.You had front end (panel) damage - so just about anything goes - even poor ground or a cap shorted and voltage leaks past. (Like the PA - bias can feed into the mic line but it would more distort audio than pinch it off (600 ohm dynamic))&nbsp;One area that has a cap that gets goofy, is the Mic amp itself - it uses a 100uF 10V and there is also a line filter cap C109/C180 that is a 220uF cap over by the 7808 voltage regulator/Audio amp heat sink flange.But also - if any works&#039; been done&nbsp; or the damage up front passed into the rear panel in the AM regulator section - this crops up to - no regulation - audio dies too...So check AM regulator see if any cracks or even shattered diode glass from bending of the board - like a sudden impact - I can see this happening along a side rail...Mic and AM regulator share same side..there is that network back there that feeds in - so if you have carrier great, but if theres&#039; no regulation theres&#039; no audio...You&#039;ve got your hands full...</blockquote>

[QUOTE="Handy Andy, post: 634548, member: 52309"] Ok, make sure the AM power can be adjusted. If AM power can't be adjusted - then the entire issue may be with the regulator itself TR36 - it mixes Bias and audio and feeds the Darlington pair. As you said and I do agree - a cap or rising voltage somewhere is pinching off the audio. You had front end (panel) damage - so just about anything goes - even poor ground or a cap shorted and voltage leaks past. (Like the PA - bias can feed into the mic line but it would more distort audio than pinch it off (600 ohm dynamic)) One area that has a cap that gets goofy, is the Mic amp itself - it uses a 100uF 10V and there is also a line filter cap C109/C180 that is a 220uF cap over by the 7808 voltage regulator/Audio amp heat sink flange. But also - if any works' been done or the damage up front passed into the rear panel in the AM regulator section - this crops up to - no regulation - audio dies too... So check AM regulator see if any cracks or even shattered diode glass from bending of the board - like a sudden impact - I can see this happening along a side rail...Mic and AM regulator share same side..there is that network back there that feeds in - so if you have carrier great, but if theres' no regulation theres' no audio... You've got your hands full... [/QUOTE]

Top Bottom