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soldering iron temp ??
- Thread starter 1iwilly
- Start date
Depends on the type of solder. I use 330°C for 60:40 and 63:37, only increasing it when I encounter something stubborn.
Most things are lead-free now, and that takes a little more heat, especially with smaller tips that don't transfer heat well, but once a little lead solder gets mixed in, the melting point of the entire joint drops.
There are pros and cons to all the solder alloys. Lead-free play better with chip quik and other low melting chip removal alloys because bismuth makes lead brittle and can cause joint failure, but lead-free solders are also higher temp which can be harder on sensitive/small parts. I will always use lead-based solder, I just make sure that if I use a low-melting bismuth alloy, I clean and flush the pads before installing the new part.
In your case, I would first apply a little 60:40 to the resistor leads, then, with flux on the SMD part, I would use the soldering iron to melt the 60:40 on the resistor lead into the solder holding the SMD part allowing the solder to enhance thermal contact (rather than a dry iron tip on the smd part). Be careful though, if you get it too hot, the SMD will transfer enough heat to the other side and it will come off ~ usually sticking to the iron tip sealing its fate.
Most things are lead-free now, and that takes a little more heat, especially with smaller tips that don't transfer heat well, but once a little lead solder gets mixed in, the melting point of the entire joint drops.
There are pros and cons to all the solder alloys. Lead-free play better with chip quik and other low melting chip removal alloys because bismuth makes lead brittle and can cause joint failure, but lead-free solders are also higher temp which can be harder on sensitive/small parts. I will always use lead-based solder, I just make sure that if I use a low-melting bismuth alloy, I clean and flush the pads before installing the new part.
In your case, I would first apply a little 60:40 to the resistor leads, then, with flux on the SMD part, I would use the soldering iron to melt the 60:40 on the resistor lead into the solder holding the SMD part allowing the solder to enhance thermal contact (rather than a dry iron tip on the smd part). Be careful though, if you get it too hot, the SMD will transfer enough heat to the other side and it will come off ~ usually sticking to the iron tip sealing its fate.
I would try to put the tip on the tinned resistor lead, and let the heat conduct to the smd part. Maybe set up something to hold the big resistor to make sure it doesn't move. Get in and out with the iron quickly, shouldn't take much.
i would start in the low 600's. Fahrenheit of course.
you're going to end up moving that surface mount resistor i can almost guarantee you, so you'd be better off removing it and just putting the equivalent value part in it's place.
it looks like the chip resistor is a 1K, and if it is then the equivalent resistance to those two values in parallel is 816 ohms.
my advice would be to buy an 820 ohm chip resistor, and if you're not comfortable soldering those, then an 1/8 watt through hole resistor would be your best bet.
you could also look on the schematic to determine if there are larger "tie points" that you could solder that 4.7K across.
LC
you're going to end up moving that surface mount resistor i can almost guarantee you, so you'd be better off removing it and just putting the equivalent value part in it's place.
it looks like the chip resistor is a 1K, and if it is then the equivalent resistance to those two values in parallel is 816 ohms.
my advice would be to buy an 820 ohm chip resistor, and if you're not comfortable soldering those, then an 1/8 watt through hole resistor would be your best bet.
you could also look on the schematic to determine if there are larger "tie points" that you could solder that 4.7K across.
LC
Look at the schematic, it's a R1087
22k ohm resistor. To me, it looks like i can put the 4.7k to pin 3 and pin 4 ?? Icom printed boards on the service manual suck, they use a red color for background so you can't see chip lay out
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yeah that was a bit confusing, as i looked up the mod and it did say it's R1087 that needs to be paralleled instead of R1082 as you originally posted.
im not sure what resistor you were holding that 4.7K above in your pic but it was definitely a 1K resistor.
If it is indeed that 22K resistor that you are trying to parallel with a 4.7K then absolutely yes, soldering it across pins 3 and 4 will be easier.
LC
im not sure what resistor you were holding that 4.7K above in your pic but it was definitely a 1K resistor.
If it is indeed that 22K resistor that you are trying to parallel with a 4.7K then absolutely yes, soldering it across pins 3 and 4 will be easier.
LC
Thanks, loosecannon, i fixed the typo, but yes, 1087, and i uploaded the right pic. The resistor with 223 is the 22k ohm
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Easy to confuse the numbers, R1087 IC1082.
Since the feedback resistor (definitely 1k) is lower than the parallel combination of 22k and 4.7k (3.9k), it is hard to say if this mod will produce the results you want. After all, the mod I read online did not mention the original resistor value, so we do not know what that mod applies to, radios with the 1k resistor or the 22k resistor. Maybe you have a mod sheet saying what the original resistor was that this mod applies to. The one I read did not mention it. I saw the updated pic, editing accordingly.
Correct me if I am wrong, but shouldn't that resistor be increased if you want more output from the op amp? If anything is being paralleled, I think it should be across R1088.
Looks like there is more than one way to do this though. That IC1087 amp has a voltage control input at pin 8. It looks like IC1701 (a 12 channel DA converter with buffered outputs) takes a digital signal from the processor and turns it into a control voltage (MONV) which is supplied via R1092 to the junction of the voltage divider that provides the initail bias to pin 8 of IC1082 (the VCA).
The divider (R1091 and R1093) puts pin 8 at 5v*8200/(8200+27000)=1.164v and the DA's buffered output works to change it from there. By monitoring this control voltage, it might be possible to figure out a mod that alters the gain using the control pin rather than altering the feedback path. Although I admit, altering the feedback would have less impact on the range the settings produce. But if it is too quiet across the range, who cares if we shave a little off that.
Looking at the VCA's datasheet, we can see control voltage vs gain curve to give us an idea (once we know what the DA is doing to pin 8's quiescent state).
The real question is whether or not the DA can bring the voltage up to at least 2.5v where the gain cannot go any higher. If pin 8 is above that voltage, then the feedback path is the only way to increase it further.
Correct me if I am wrong, but shouldn't that resistor be increased if you want more output from the op amp? If anything is being paralleled, I think it should be across R1088.
Looks like there is more than one way to do this though. That IC1087 amp has a voltage control input at pin 8. It looks like IC1701 (a 12 channel DA converter with buffered outputs) takes a digital signal from the processor and turns it into a control voltage (MONV) which is supplied via R1092 to the junction of the voltage divider that provides the initail bias to pin 8 of IC1082 (the VCA).
The divider (R1091 and R1093) puts pin 8 at 5v*8200/(8200+27000)=1.164v and the DA's buffered output works to change it from there. By monitoring this control voltage, it might be possible to figure out a mod that alters the gain using the control pin rather than altering the feedback path. Although I admit, altering the feedback would have less impact on the range the settings produce. But if it is too quiet across the range, who cares if we shave a little off that.
Looking at the VCA's datasheet, we can see control voltage vs gain curve to give us an idea (once we know what the DA is doing to pin 8's quiescent state).
The real question is whether or not the DA can bring the voltage up to at least 2.5v where the gain cannot go any higher. If pin 8 is above that voltage, then the feedback path is the only way to increase it further.
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Lets just ignore my pin 8 detour for a minute. That mod is giving me trouble.
Op-amps 101: When you feed a signal into the + input and connect the output directly to the - input, the output will be the same as the input since the op-amp works to eliminate the voltage difference between the + and - inputs.
Add a voltage divider between the output and the - input and now the output has to go higher to get the same voltage at the - input. Ok, that's fine. More gain.
But if we then parallel R1087 lowering its value, more of the output goes to the - input, meaning less output is needed to do the same job. Less gain.
I think if anything needs to be paralleled, its R1088 (or raise the value of R1087).
Feel free trying that mod, but I have a feeling that decreasing R1087's value by paralleling it will drop the gain and make the monitor volume even quieter.
Op-amps 101: When you feed a signal into the + input and connect the output directly to the - input, the output will be the same as the input since the op-amp works to eliminate the voltage difference between the + and - inputs.
Add a voltage divider between the output and the - input and now the output has to go higher to get the same voltage at the - input. Ok, that's fine. More gain.
But if we then parallel R1087 lowering its value, more of the output goes to the - input, meaning less output is needed to do the same job. Less gain.
I think if anything needs to be paralleled, its R1088 (or raise the value of R1087).
Feel free trying that mod, but I have a feeling that decreasing R1087's value by paralleling it will drop the gain and make the monitor volume even quieter.
i can verify it does work without the resistor i had to have the volume at 12 to 1 o'clock i held the resistor on the 2 spots while the wife connected the power cord, listening through the headphones, i had to lower the volume to 8 o'clock. Now the bad. i need a better headband magnifier. 3.5 is not enough for my bad eyes, and 2 is very tight to solder i just can't find a good, clear copy of the service manual to see if i can tap somewhere else for the 2 spots. The funny part my hands only shake when i grab the soldering iron and bring it close to the component.
Well, i took a chance, heart racing, feeling like them guys in the movies trying to defuse a bomb, red wire, white wire, shaky hands. But I solder that sumamabitch resistor on there, thanks for the replies. Now the 8 o'clock position is like 1 o'clock position. Reason for the mod is when the volume at 1 o'clock to monitor my audio, when i unkey the volume is super high, whether through headphones or an external speaker, compared to now at a reasonable listening setting
Attachments
Great job, glad you got it done. I want to add that to combat shakiness, I stop caffeine the day before. That takes care of most, but a good belt beforehand helps steady the hands, and practice your smd work on some smd electronic scrap. I have lots of stuff around that I can practice on, starting with tacking a wire to an ic pin, do it over and over until you consistently get a clean joint and no blobs. Then I try other things until confident. Practice your hot air station on scrap so you figure out the air pressure needed, not blowing components off the board or interfering with components in proximity to the area worked, and how to maneuver the gun above, below and around to keep from burning. I did all this before ever attempting smd work, and it really paid off.
You are not the only one, and you should talk to your primary care doctor, I have been diagnosed with essential tremors, it started several years ago, I found it was getting harder to do fine detail work, soldering is now difficult because of this.
Essential Tremor shakiness is often called an intention or action tremor because it worsens when a person performs some specific task, such as picking up a glass. The most common initial symptom is shaking of the hands, but other areas, including the arms, legs, and head, are frequently involved. Some people develop a trembling voice. At rest or during sleep, the tremor tends to improve or go away.
It's a real thing, not just a symptom of getting old.
73
Jeff
The monitor function on the IC-746 tends to have low output compared to receiver AF volume; therefore, in order to listen to yourself, you have to increase the volume. When the PTT is released back to receive mode, the AF setting nearly blows your speaker or your headphones.Add a 4.7K resistor in parallel with R1087. This brings up the gain of IC1082 to a more reasonable level that can still be controlled by the monitor level function, but with plenty more gain