This 55v has a 1k ohm pot for vr16, should I change it out for a 5k ohm pot at vr16 or leave it 1k ohm? Someone might have even changed it before because my other radios with the same board show 5k ohm ports at vr16. Maybe where they were dual final boards is the difference?
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Direct injected galaxy DX55V wattage problems
- Thread starter That_guy_in_wv
- Start date
I checked tr41, 50, 51, all voltages show good on amps and regulators when keyed with audio cord in, but they're still getting hot and wattage still won't turn down if turned up, key set to 2 watts and all the way up 5. Once turned up it won't go back down. I changed D91 to a new 1n4148 and put c190 back to a 100uf at 16v. I also changed vr16 back to a new 1k ohm pot but still no difference.
Tr50 and tr51 show 3v on the collector (center pin) when going from board ground to pin, 2.85v when keyed. There should be 5.40 volts dc on the collector.
I've changed c143, c146, c147, c148, c149, c150, c189, c190, c191, c212, tr49, tr50, tr51, D29 and D91 still no change same as befor. I also changed vr13 and vr16
Whoa! Ok, we're in a shotgun mode here...
It may be from other components you haven't even thought of yet.
Lets' see if you can take a look at the TX Strip - it may be a failed cap in that strip that is causing the feedback.
Again above and behind - so slow down, I know you want it fixed, but one thing that did happen is you swapped in that radio into another antenna. So if stability in one location was good, we cannot guarantee the same in all locations it's used in.
The 1K pot? Yes, knowing it's a "dual" final radio - loading of the circuit does change, the adjustment is different - you obtain higher RF power with same Test point voltages you'd use with a SINGLE final design, so relax, we're on it...
Locate C174, it was originally a 2.2uF - replace it with a Fresh one....50V (50WVDC)
Since this is a DI model - some changes have occurred so I'll need to know if other changes were made in other areas - but that's for later - just do the C174 thing..
It may be from other components you haven't even thought of yet.
Lets' see if you can take a look at the TX Strip - it may be a failed cap in that strip that is causing the feedback.
Again above and behind - so slow down, I know you want it fixed, but one thing that did happen is you swapped in that radio into another antenna. So if stability in one location was good, we cannot guarantee the same in all locations it's used in.
The 1K pot? Yes, knowing it's a "dual" final radio - loading of the circuit does change, the adjustment is different - you obtain higher RF power with same Test point voltages you'd use with a SINGLE final design, so relax, we're on it...
Locate C174, it was originally a 2.2uF - replace it with a Fresh one....50V (50WVDC)
Since this is a DI model - some changes have occurred so I'll need to know if other changes were made in other areas - but that's for later - just do the C174 thing..
But not C128 (2.2uF Tantalum) or C129 1uF - because the imbalance can cause this squeal ...
But - wait...
Ok, lets' see if the "squeal" is from the Mic amp...
Got a 560pF laying around?
Place it across the Mic amps Feedback Resistor - R165, should be a 270 K Red, Violet Yellow...lowers gain see if it's related to open loop or leaky/faulty resistor at R165
Also remove R172 - leave TR32 in place at the moment...
Check again...still High Carrier?
- No? Suspect Mic amp...thru feedback loop of parts related to AMC/ALC including Limiter
- else - continue
Next Step - remove C187 - completely disconnect the Mic amp from your injection point.
Check again? Still high carrier?
This leaves in TR32...and TR34's ability to handle ALC and AMC...
If the Mic amp is at fault for this uttrasonic squeal, removing R172, and C187 this would remove it from the AM regulator and should restore your ability to adjust AM power.
But, if the "high carrier" still exists, continue to leave Mic amp out of circuit, Time for the next step...including Removing TR34...
Still a Squeal, then with Mic amp, ALC AMC - out of any influence, the suspected parts are back with the Injection point and the parts that interface with it. Including the parts used to put it in there (back at the Hi-Fi equipment itself)
We have to do this in steps to make a flow chart so we can retrace back to the points that we get or lose, control of carrier.
I placed the 560pf across R165 and lifted R172 but now the carrier will only got from 0 to .2 watts. Even with the cap removed wattage dropped out to nothing but driver carrier I believe.
The new cap at C174 was bad, it was new? I replaced it wattage is back. Ok back to checking the mic amps feedback resistor. I'll be back
I removed tr32 and tr34 and carrier is still the same. Weird part is that tr32's location is marked on the board as tr37, there are 2 tr37's silk screened on this board lol.
P.S. my injection points audio cable is plugged into my phones headphone port. it leaves no hifi equipment failures to have to take out of the equation. Audio will still play over the air on a dummy load and I can still test the radio as if its plugged into the pc getting audio still. Same same but different...
P.S. my injection points audio cable is plugged into my phones headphone port. it leaves no hifi equipment failures to have to take out of the equation. Audio will still play over the air on a dummy load and I can still test the radio as if its plugged into the pc getting audio still. Same same but different...
Ok, well, the rub now is, you have a feedback path, but it's not audible.
We have not ruled out AMC and ALC, just found out its' not caused by a loop BACK to the Mic amp - But TR53 and D83 work TR34. (I know I said ALC - but there is an ENVELOPE control at TR53 - but also Audio limiter so to me it QUALIFIES as ALC because it LIMITS envelope (TR32 thru D67, D68 and D69 routing))
So, in some Radios the SSB has an ALC at the RF output tap, along with AMC and The TR32 route from Mic amp out.
So the effort is not a high pitched squeal that is a feedback problem, you have a DC Bias issue...
OR...
Are you sending out FM and AM signal at the same time? Then that area is by the MODE switch - two diodes from Voltage Regulator TX side of 4558 D81, D82 - checks status of Mic Pin 3 for TX toggle. Just make sure Diodes are NOT acting like dead shorts - they will toggle in TX, but having it (one or Both) shorted lets another section power or add power, into the TX Pin 3.
At one time you said you were not getting TX light - this is where I scratch my head....so that means Pin 8 LOCK on the PLL - but that can be from a bad cap - did you get TX back?
Which even goes deeper, So remove the piggy, Replace TR32, TR34 put them back in, Restore the Mic amp. or OEM as you can.
This can even get to a back panel problem with mounting the Final and Driver, potentially a breakdown problem. (perforated an insulated part causing ground loop)
So just review your work, and now is a time for reheat-reflow work in the driver and final area - to have this occur, you'll need to look for "thermal" heating up faster than the area around it - sort of thing.
The main culprits are AM regulator - which you know heats up - do you have any spare 2SA473s? Part of the "Darlington pairing" IF you feel the 754 is good, did you check the 473? Heck even R242 that 10K by the 473 can be suspect as opened up.- or if changed - new part may add to this. Even mounting hardware - everything recently done to Inject has to be gone over.
Also TR53 - AMC - just pull it for now, to remove a loop. But keep it out, but around, until we eliminate the AM Regulator section - this area gets hot, but in what part first?
We have not ruled out AMC and ALC, just found out its' not caused by a loop BACK to the Mic amp - But TR53 and D83 work TR34. (I know I said ALC - but there is an ENVELOPE control at TR53 - but also Audio limiter so to me it QUALIFIES as ALC because it LIMITS envelope (TR32 thru D67, D68 and D69 routing))
So, in some Radios the SSB has an ALC at the RF output tap, along with AMC and The TR32 route from Mic amp out.
So the effort is not a high pitched squeal that is a feedback problem, you have a DC Bias issue...
OR...
Are you sending out FM and AM signal at the same time? Then that area is by the MODE switch - two diodes from Voltage Regulator TX side of 4558 D81, D82 - checks status of Mic Pin 3 for TX toggle. Just make sure Diodes are NOT acting like dead shorts - they will toggle in TX, but having it (one or Both) shorted lets another section power or add power, into the TX Pin 3.
At one time you said you were not getting TX light - this is where I scratch my head....so that means Pin 8 LOCK on the PLL - but that can be from a bad cap - did you get TX back?
Which even goes deeper, So remove the piggy, Replace TR32, TR34 put them back in, Restore the Mic amp. or OEM as you can.
This can even get to a back panel problem with mounting the Final and Driver, potentially a breakdown problem. (perforated an insulated part causing ground loop)
So just review your work, and now is a time for reheat-reflow work in the driver and final area - to have this occur, you'll need to look for "thermal" heating up faster than the area around it - sort of thing.
The main culprits are AM regulator - which you know heats up - do you have any spare 2SA473s? Part of the "Darlington pairing" IF you feel the 754 is good, did you check the 473? Heck even R242 that 10K by the 473 can be suspect as opened up.- or if changed - new part may add to this. Even mounting hardware - everything recently done to Inject has to be gone over.
Also TR53 - AMC - just pull it for now, to remove a loop. But keep it out, but around, until we eliminate the AM Regulator section - this area gets hot, but in what part first?
tx/rx light works when the radio is keyed it never stopped working, the pre-driver for the driver final is also getting hot. Voltage on its center pin is very high. I'll check the work I did again, i replaced the 2sb754 with the 2sb827 when I first did the di it was the only ones i have around and the 473's are replaced with 1869"s. I'll wait till we get back together before I do more, not sure if that might rule something out. Thanks