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In search of Palomar SL41
- Thread starter Eldorado828
- Start date
The gain is touchy and takes some time to tailor just right. It's a chore trying to hold the mic disassembled, keying it while talking, watching, listening and turning that tiny potentiometer... patience, lots of patience!
There is more BENEATH those 4 screws...
Those holes are plated thru - you only see the top of the board - there's more under it...
There is more under this circuit board you'll need to look at - one is the regulation - once you see the underneath, you'll know how the "regulators" work. Those jumpers feed the parts underneath...This is a multi-purpose platform for even the Up-Down button radios' with channel changers. They can supply the 5V (7805) or 12V so you can multi platform into radios that use regular dynamic (makes it appear as such) or Electret - High output or use with radios like the Amateur types that have 12V access available.
IF so inclined even talkback.
Now when you flip that board over, you may or may not have it populated - - but the support pads are there to install your own if you wish - it makes a neat hobby kit for a evenings work if you have the parts needed for that. Else it is frustrating because if not populated - you'll see where they go and you'll need to generate your own parts list to finish the customizing.
I believe the FET - per schematic is under there too...
Those holes are plated thru - you only see the top of the board - there's more under it...
There is more under this circuit board you'll need to look at - one is the regulation - once you see the underneath, you'll know how the "regulators" work. Those jumpers feed the parts underneath...This is a multi-purpose platform for even the Up-Down button radios' with channel changers. They can supply the 5V (7805) or 12V so you can multi platform into radios that use regular dynamic (makes it appear as such) or Electret - High output or use with radios like the Amateur types that have 12V access available.
IF so inclined even talkback.
Now when you flip that board over, you may or may not have it populated - - but the support pads are there to install your own if you wish - it makes a neat hobby kit for a evenings work if you have the parts needed for that. Else it is frustrating because if not populated - you'll see where they go and you'll need to generate your own parts list to finish the customizing.
I believe the FET - per schematic is under there too...
Am disappointed this mic squeals with my Galaxy 99v2. Seemed fine with the U980.
Turned it down internally all the way (counterclockwise), and turned Mic Gain pretty much Off. (Power turned down max amount, no Echo, etc).
Original SL41 mic from original release, no mods. Only difference I see from others is in pic HA linked from Eldo: Batt Neg on mine is two-pins close together versus the single pin shown in pic. (Green Arrow).
No deal. Just squeal.
Luckily, the Astatic 636L and a nice old RK56 both sound good (the U980 into an external speaker sitting back in the bunk). Can’t tell much difference if any.
So, have tested four (4) mics into the current big truck mobile rig. Down to two. (RK56 now the spare). The Galaxy mic stays home after this trip.
The A636 is the one originally-paired to this radio back in ‘14.
The PALOMAR SL41 needs some help.
.
Turned it down internally all the way (counterclockwise), and turned Mic Gain pretty much Off. (Power turned down max amount, no Echo, etc).
Original SL41 mic from original release, no mods. Only difference I see from others is in pic HA linked from Eldo: Batt Neg on mine is two-pins close together versus the single pin shown in pic. (Green Arrow).
No deal. Just squeal.
Luckily, the Astatic 636L and a nice old RK56 both sound good (the U980 into an external speaker sitting back in the bunk). Can’t tell much difference if any.
So, have tested four (4) mics into the current big truck mobile rig. Down to two. (RK56 now the spare). The Galaxy mic stays home after this trip.
The A636 is the one originally-paired to this radio back in ‘14.
The PALOMAR SL41 needs some help.
.
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Slow, when I had talked to the folks at Bob's about the two resistors they added when building them, they said it was a mod from palomar to rid of the squeal you're speaking of. I know I have some pictures of their mod but will have to look for them in my cloud. I'll get them up in the next day or two and tell you what those values are so you can get yours working.
Hopefully that'll get you to where it's usable on the 99v2, and maybe someone else with one of these now kind of unicorn mics.
Looking closely at the pictures, it appears one of the wires needs moved from that capacitors pad that other pad also occupied by a red wire.... If that makes sense. Compare the original to the Bob's version and you'll see what I mean. Not sure if that's also parr of the mod.
Looking closely at the pictures, it appears one of the wires needs moved from that capacitors pad that other pad also occupied by a red wire.... If that makes sense. Compare the original to the Bob's version and you'll see what I mean. Not sure if that's also parr of the mod.
You're splitting down the output.
...uses a 4.7K resistor across the output...
Difference between the two?
One is done up to be closer to EXPTECTED input impedance of the MIc amp circuit -
use what you wish...
When you run a mic with open cap - you're at the mercy of the environment - when you place a terminating resistor on the output side of that same cap, you have FAR less problems with squeals and open loop gain feedback paths you never know when or where they will show up.
Remember too, that the Mic you originally have with the radio MAY require POWER to operate it's Electret Condensor and or Any SPECIAL FUNCTIONS the handset uses to communicate thru the Mic cord...Channel Changer, Squelch, Monitor - these functions may interfere unless you take steps to remove power, trim wires - any live wires can cause problems.
The 1K resistor mod shown, you nay need to use these values because of the gain the Mic has and it's ability to overdrive the inputs of a system that looks for Electret Condensor - the 1K ACROSS the mic Wire helps to TERMINATE the Audio Line properly to reduce chances of squealing.
Look around at many Mic amp "outputs" - many are terminated using a fixed resistor or at the end of a variable for this same problem they would otherwise have with theirs.
Some may have to use this method...
Bobs CB Shop design......uses a 4.7K resistor across the output...
Difference between the two?
One is done up to be closer to EXPTECTED input impedance of the MIc amp circuit -
use what you wish...
When you run a mic with open cap - you're at the mercy of the environment - when you place a terminating resistor on the output side of that same cap, you have FAR less problems with squeals and open loop gain feedback paths you never know when or where they will show up.
Remember too, that the Mic you originally have with the radio MAY require POWER to operate it's Electret Condensor and or Any SPECIAL FUNCTIONS the handset uses to communicate thru the Mic cord...Channel Changer, Squelch, Monitor - these functions may interfere unless you take steps to remove power, trim wires - any live wires can cause problems.
The 1K resistor mod shown, you nay need to use these values because of the gain the Mic has and it's ability to overdrive the inputs of a system that looks for Electret Condensor - the 1K ACROSS the mic Wire helps to TERMINATE the Audio Line properly to reduce chances of squealing.
Look around at many Mic amp "outputs" - many are terminated using a fixed resistor or at the end of a variable for this same problem they would otherwise have with theirs.
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Unless the newer ones have that option mine don't have it.
There are several MENU's on that damn thing, one being Mic Gain another having Hi-Cut...
Which is why I hated working on programming those things as a Customer Engineer (CE-stuff)
This link....
https://www.worldwidedx.com/threads/question-on-the-anytone-6666.258034/#post-734042
Can it help you?
So yes, I could be wrong about that - and no - to me personally, the Mic Gain would be the control I'd be looking into to find the right setting of Gain for it.
Which is why I hated working on programming those things as a Customer Engineer (CE-stuff)
This link....
https://www.worldwidedx.com/threads/question-on-the-anytone-6666.258034/#post-734042
Can it help you?
So yes, I could be wrong about that - and no - to me personally, the Mic Gain would be the control I'd be looking into to find the right setting of Gain for it.
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Another thing to watch out for,
Got a spare 2-pin Header jumper from an old PC?
Why? Because of the Hi-cut filter and the Volume control output level - both when that header is jumped, work together - it bypasses the output "hi-impedance" cap - and lets you adjust not just volume, but tone directly.
Look at post # 139 from me - the "Header" is already installed.
So to help your situation - you may need to install that jumper on the output to your resistor pair to offset a tonal problem and bring the output control to bear more influence on the output tying both tone and output controls together...
