-
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.
Melaka poor audio on ssb
- Thread starter Staybolt
- Start date
This is easiest with another radio in the same room. Turn down the mike gain so the wattmeter won't kick above about a half Watt on sideband.
If it sounds worse that way than it does turned up, the bias is set too low on either the driver, the final or both.
A common problem, especially if either of the trimpots for driver or final bias got turned randomly.
And if it sounds better turned that low, and worse when turned back up, this is not the problem.
73
If it sounds worse that way than it does turned up, the bias is set too low on either the driver, the final or both.
A common problem, especially if either of the trimpots for driver or final bias got turned randomly.
And if it sounds better turned that low, and worse when turned back up, this is not the problem.
73
Have you a power meter? If so put it inline. Start transmitting with the mic gain turned all the way down and saying something like OOOOOLLAAAAHH into it. Increase the mic gain until the power no longer goes up. There is absolutely no advantage to increasing mic gain above that point on SSB. You won't put out any more power, you won't sound any louder, you'll just sound distorted if you do.
Ive done that plus checked the bias. Still sounds shitty. It almost sounds like how a crappy class c linear sounds on ssb very choppy and distorted....
Yup thats what im using is my meter. Also the radio has almost no audio gain even with a d 104.
You should get one. It is basic tool to diagnose, repair and tune rx/tx equipment.
Mike
Check your final amplifier stages. some of the FET's could be smoked. If you know some one with a scope borrow it or take your radio to them. The Galaxy amps get burned fairly easily.
If the amp is bipolar the bias resistors might be burned.
If the amp is bipolar the bias resistors might be burned.
Last edited:
The 4558/IC4 might be toast?
There is a mod to change out two resistors on that IC and it makes the audio louder but distorts too much too. Check it against schematic and try replacing IC4 with another known good one. Seen that one before . . .
There is a mod to change out two resistors on that IC and it makes the audio louder but distorts too much too. Check it against schematic and try replacing IC4 with another known good one. Seen that one before . . .
"Choppy and Distorted" usually means you have a bad coupling issue between two stages.
The Melaka uses the 360014B board...so IF you have that Schematic Great! Else, you should get one as well as the component layout one too. Foil side of it too, can help...
As SP5IT was inferring - if your AM sounds ok, and seems to show no signs of "pinching" - then the path to the AM Regulator should be ok. But are you sure? Does PA and FM mode also sound ok? AM Regulator can run in two modes - Carrier control (Forms FM and AM power) or open Throttle SSB mode (SSB where ALC is the limit)
But, it uses several methods to turn off the Regulator for SSB mode. If one of them isn't working right, you can get pinched or distorted audio.
That doesn't mean it's there either - you can get pinched audio effects from a poor tuneup - might be a good idea to double check work and verify your tune up is right - else nothing is going to work.
Lets' take a look...
Those are your tuneup locations...Alignment - Caster/Camber -Toe-In Toe-Out - Tracking
And there's your Mic amp section and it's related components...
So, did you do your homework and see if the Bias (TX) voltage at R217 is even there?
Did you check to verify ALC is working? (Removing TR32 and the audio clears up - well you have more work to do)
FM mode - does FM work ok or do you get "distorted results" in that mode too?
IF your only mode that gives you distorted audio is in SSB - then make sure AM Regulator and all it's systems are not interfering with the Radios' Full-Throttle control.
How about that wonderful Wall-Of-Wattage - the TX Strip and related components - did someone screw up a slug or is the Bandpass Filter out of whack? How about the Predrivers? Issues?
So please - tell us that you've done all we've asked you to do - so we can help you...Lots of people have stopped in to help - doesn't seem like you're getting anywhere - so work with us here...