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148GTL MALAYSIA

This is where it gets dangerous, for it will drift terribly after reading that mod...

You'll need to make some decisions.

You want to put in a different pot...?

One, When you do this mod, are you able to keep - or wish to keep - center slot? Then all parts must STAY in place - in one form of ohmic reading or another.​

Two - You are using a different pot than what was specified - since this is a Malaysian model, I cannot guarantee the ability to use that described mod for your work.​

Three - VERIFY the pot you're swapping in. Did you measure the resistance across the 2 FIXED terminals of the Pot, the two that are not adjustable? What was your reading?​

If it's 40K or more, then you will have to change R174 from 12K to 10K to offset the divider difference between 20K pot of the ORIGINAL, to the 50K Pot of the replacement - being higher - changes the LINEARITY or "center" of the pot to the EXPECTED Center slot the board thinks you should be at.​
  • 1/2 being Center would be 10K either side, of the ORIGINAL 20K pot.
  • now? IT's more like 20~22K either side, divide down the R174 by half to obtain a better linearity of turn (rotation) for Up and Down. You can try 8.2 K - but 10K is better - See R124 afterwards to help with "Center"
    • You will need to "adjust R174" to fix the "divider range" in expected ohmic resistance across the Varactors' to provide more linear rotation. This also helps you with Drift issues later.
    • If you use a 10K pot, you'd have to GO UP in value for R174 to 18K to offset this ohmic loss of tuning range.
There is a better way, you have to keep R124 in place - R174 is a "Divider" that makes the rotation more even both up or down from "center". IF you don't care, then REMOVE R174. HOWEVER you'll have to "retune" the USB LSB and AM to "Center slot" when you remove R174.

R124 is needed to even obtain Center Slot - keep it in there - for both Drift and linearity to either side up or down from Center. R124 can also provide you an easier WAY OUT of the "center slot tuning mess" you'll be in when you apply for open clarifier and make too many changes.

Fourth - The test, you will have to KNOW which way the Clarifier "center" will change.
  • IF all parts are in place and you just want to replace the 20K with a 50K - then R174 is a 10K, R 124 is now a 1.2K.
    • You are going DOWN in ohmic value to offset a LOADING condition the Varactor will see, since it's literally twice as much as before (If you switch to a 50K) - DROP- LOWER R124 to 1/2 Original value
Locate VR402 going back to the Main PCB.- Remove/Unbolt any echo boards, Frequency counters - to allow access.

EASY - Beginners Way - When you KEEP the Original Potentiometer

- also the most beneficial and least stressful way...​

Behind the front panel - locate the Voice Lock Pot and it's color code, trace it back to near -centerline- more to front, you should be able to see an outline or header labeled VR402 - this is the location.

Find R124 towards the back of the header on the main PCB, behind it there will be a wire, trace this wire - follow back towards the Right Front - by S/RF meter - remove it- unsolder or clip - from this point...

Locate D52, unsolder - lift one leg - to disconnect the 8 volt TX

  • - Why unsolder? Easier to restore normal operation later if you need to return this back to stock for Resale - SEE Ferengi
upload_2020-10-9_19-38-44.png
Locate MODE switch. A series of wires head to BACK to the MAIN PCB IN FRONT OF the VR402 location by D52 and D75 - it's by the edge of the front of the board. Locate the 8 volt Constant at that Jumper J12A (?) - I've posted a graphic below to help.
upload_2020-10-9_18-24-46.png
Solder wire to this jumper that has your 8V constant - you're done!
Does It Have To Be This Complicated?

It's when you want to add in a different ohmic reading potentiometer
and all of the associated headaches caused by using a less than ideal,
non-linear functioning and more drifting problematic potentiometer
of a different value than what the manufacturer used/installed there,
in the first place....
Yes, because you haven't even verified that you can successfully unlock the Clarifier using it in it's stock form and observing results to even see if it tunes the way you want to go.

See graphic above and note the Color coding - this follows your comment on the B20K pot you scavenged from another Galaxy-based Donor.

It's Pin out of leads are - two outer lugs are your FIXED resistance, the inside one (Middle) is your variable.

Orange and Violet, if it's doesn't rise and fall in the right direction of turn to suit your tastes, swap Orange and Violet around AT THE POTENTIOMETER . - Green wire is your Wiper/Variable in the above Graphic.
 
This is where it gets dangerous, for it will drift terribly after reading that mod...

You'll need to make some decisions.

You want to put in a different pot...?

One, When you do this mod, are you able to keep - or wish to keep - center slot? Then all parts must STAY in place - in one form of ohmic reading or another.​

Two - You are using a different pot than what was specified - since this is a Malaysian model, I cannot guarantee the ability to use that described mod for your work.​

Three - VERIFY the pot you're swapping in. Did you measure the resistance across the 2 FIXED terminals of the Pot, the two that are not adjustable? What was your reading?​

If it's 40K or more, then you will have to change R174 from 12K to 10K to offset the divider difference between 20K pot of the ORIGINAL, to the 50K Pot of the replacement - being higher - changes the LINEARITY or "center" of the pot to the EXPECTED Center slot the board thinks you should be at.​
  • 1/2 being Center would be 10K either side, of the ORIGINAL 20K pot.
  • now? IT's more like 20~22K either side, divide down the R174 by half to obtain a better linearity of turn (rotation) for Up and Down. You can try 8.2 K - but 10K is better - See R124 afterwards to help with "Center"
    • You will need to "adjust R174" to fix the "divider range" in expected ohmic resistance across the Varactors' to provide more linear rotation. This also helps you with Drift issues later.
    • If you use a 10K pot, you'd have to GO UP in value for R174 to 18K to offset this ohmic loss of tuning range.
There is a better way, you have to keep R124 in place - R174 is a "Divider" that makes the rotation more even both up or down from "center". IF you don't care, then REMOVE R174. HOWEVER you'll have to "retune" the USB LSB and AM to "Center slot" when you remove R174.

R124 is needed to even obtain Center Slot - keep it in there - for both Drift and linearity to either side up or down from Center. R124 can also provide you an easier WAY OUT of the "center slot tuning mess" you'll be in when you apply for open clarifier and make too many changes.

Fourth - The test, you will have to KNOW which way the Clarifier "center" will change.
  • IF all parts are in place and you just want to replace the 20K with a 50K - then R174 is a 10K, R 124 is now a 1.2K.
    • You are going DOWN in ohmic value to offset a LOADING condition the Varactor will see, since it's literally twice as much as before (If you switch to a 50K) - DROP- LOWER R124 to 1/2 Original value
Locate VR402 going back to the Main PCB.- Remove/Unbolt any echo boards, Frequency counters - to allow access.

EASY - Beginners Way - When you KEEP the Original Potentiometer

- also the most beneficial and least stressful way...​

Behind the front panel - locate the Voice Lock Pot and it's color code, trace it back to near -centerline- more to front, you should be able to see an outline or header labeled VR402 - this is the location.

Find R124 towards the back of the header on the main PCB, behind it there will be a wire, trace this wire - follow back towards the Right Front - by S/RF meter - remove it- unsolder or clip - from this point...

Locate D52, unsolder - lift one leg - to disconnect the 8 volt TX

  • - Why unsolder? Easier to restore normal operation later if you need to return this back to stock for Resale - SEE Ferengi
Locate MODE switch. A series of wires head to BACK to the MAIN PCB IN FRONT OF the VR402 location by D52 and D75 - it's by the edge of the front of the board. Locate the 8 volt Constant at that Jumper J12A (?) - I've posted a graphic below to help.
Solder wire to this jumper that has your 8V constant - you're done!
Does It Have To Be This Complicated?

It's when you want to add in a different ohmic reading potentiometer
and all of the associated headaches caused by using a less than ideal,
non-linear functioning and more drifting problematic potentiometer
of a different value than what the manufacturer used/installed there,
in the first place....
Yes, because you haven't even verified that you can successfully unlock the Clarifier using it in it's stock form and observing results to even see if it tunes the way you want to go.

See graphic above and note the Color coding - this follows your comment on the B20K pot you scavenged from another Galaxy-based Donor.

It's Pin out of leads are - two outer lugs are your FIXED resistance, the inside one (Middle) is your variable.

Orange and Violet, if it's doesn't rise and fall in the right direction of turn to suit your tastes, swap Orange and Violet around AT THE POTENTIOMETER . - Green wire is your Wiper/Variable in the above Graphic.


The pot I pulled has the exact same readings as the one I replaced it with. 21.XX ohms center pin to left pin, center pin to right pin. The reason I replaced it was because it was loose and had no center detent (which I thought it was supposed to). the one pulled was a B20K and I replaced it with a B20K. I figured the only difference between the two was the detent since it ohmed out identical.

*edit*
Original: Left to Right pin = 21.19 ohms
Replacement: Left to Right pin = 21.21 ohms
 
Last edited:
Original: Left to Right pin = 21.19 ohms
Replacement: Left to Right pin = 21.21 ohms

*WHEW*

Ok, simplifies things, but why change - just needs detent? Hmmm... Strange, Voice Lock usually came with one - at least on my 148, Grant XL - even the F did too!

Uh oh...maybe nothing - but a parts swap? Ugh...This was made in Malaysia - being sourcing was different - they did use Ranger (RCI) for sourcing - but they have Detents in theirs - you got this one without, so you swapped another "Ranger/Galaxy" based for the same?

It's the $300 you spent on this knowing that, that bothers me...wondering what's going to happen next...
 
*WHEW*

Ok, simplifies things, but why change - just needs detent? Hmmm... Strange, Voice Lock usually came with one - at least on my 148, Grant XL - even the F did too!

Uh oh...maybe nothing - but a parts swap? Ugh...This was made in Malaysia - being sourcing was different - they did use Ranger (RCI) for sourcing - but they have Detents in theirs - you got this one without, so you swapped another "Ranger/Galaxy" based for the same?

It's the $300 you spent on this knowing that, that bothers me...wondering what's going to happen next...

He's the "real story", I messaged him about it.....
The seller was not the original owner, but a close friend. The owner passed away and the friend inherited the radios. He was going by "looks" of the radio when he listed it, plus he said if it wasn't right he'd issue a refund. The VL was loose/Sloppy so I figured that was why there was no detent. I looked in the old Connex and found a matching pot and checked it against the "original" and the readings were +/- .01-02 so I used it. Everything else seems nice and snug, no butchery that I could see. None of the screws had "wear" marks so that kinda told me it wasn't opened much. I don't mind doing little odds and ends to get it right, kinda makes me feel like I had a small hand in getting the old girl healthy again. I checked SSB using my Uniden 980 today. I'm not a SSB vet but it sounded clear on transmit and receive. I got both "tuned?" and then went up then down with the VL and could make the same adjustment on the opposite rig and bring it in clear, then return to center and they were both clear. I'm going to find someone to do the unlock for me. If it was a plentiful radio like the 29 (if it had SSB) I'd do it, but I don't want to discover I have golden screw-stick on this one.
Andy, I greatly appreciate your time and patience working on this with me.
 
I guess I'm like a "Nurse" - I worry over the simplest "ow'ies", on the patients...

I have no problem with that. The "patient" is a dying breed and I want this one to remain healthy and unbutchered. Heck, since I got the dead key turned down to run the amp, I'm not even doing the variable power. Little things can make big things smoke, so all input and advice to prevent such is most welcome.
 
I'm the total opposite of you. I have a really nice grant xl that had no mods, and it is a just a nice stock radio. It sits on the shelf and I use a beat up hacked to hell 148gtl. I just can't bring myself to use up the life of a nice old radio.
 
Last edited:
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I'm the total opposite of you. I have a really nice grant xl that had no mods, and it is a just a nice stock radio. It sits on the shelf and I use a beat up hacked to hell 148gtl. I just can't bring myself to use up the life of a nice old radio.

Now if this radio was already in bad shape, I wouldn't think twice about bailing off in it with a screw-stick in one hand and a soldering iron in the other...but other than a few 25 year old glitches, I don't see much wrong with it so I want to keep her like that.
 
Just so you know...

You may have wondered where some components are,

upload_2020-10-10_9-20-46.png

They've been updated to a different package - the board is such an older - yet trusted, design, they no longer make many of the parts to fit the outline - instead, they are surface mounts - and located on the bottom of the board...
upload_2020-10-10_9-14-53.png
Red arrows point out the Varactor's.​
 
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Just so you know...

You may have wondered where some components are,


They've been updated to a different package - the board is such an older - yet trusted, design, they no longer make many of the parts to fit the outline - instead, they are surface mounts - and located on the bottom of the board...
View attachment 40904
Red arrows point out the Varactor's.​

Is this a good or bad thing...or just "one of those things" Would it be worth replacing it with an original or leaving as is? My plans for this radio is to just talk on it, no crazy mods, no abusing the internals, not selling it...just putting it in my pick-up with a amp in-line and talking.
 
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OK....full install done. Talked to a hand about 1 mile away on my 29 and then the 148. He said the 29 sounded good but the 148 sounded better and when I turned the amp on he said it just got louder with more signal, no funny or muffled sounds, just nice clean, clear audio. I'm happy now....until I find another radio I've always wanted.
Thanks for all the help and knowledge.
 
Is this a good or bad thing...or just "one of those things" Would it be worth replacing it with an original or leaving as is? My plans for this radio is to just talk on it, no crazy mods, no abusing the internals, not selling it...just putting it in my pick-up with a amp in-line and talking.

IT's a "good thing" meaning that you have a radio they found a way to use Varactors in, when the package deign that the Varactor came in, was dropped and they did up a different way using a Varactor of a different design.

The radio is fine, just letting you know that in light of it's age, any effort to increase range of tuning requiring a change in parts and components - will require knowing how they "put it together" when otherwise the parts that would have been in there ORIGINALLY are not, since Varactors have a polarity, you will have to install them as they have done.

These are the minor quirks in using an older Discrete-bound chassis when the parts to fix them are no longer made in the same package as it was built around and used - back then.

Varactors are the simpler ones, replacing the Bipolar Transistors no longer made - having to upgrade using types of others that have a different pin out from the original design, are more difficult.

The caution here is, like what Scotty Said to Kirk,
upload_2020-10-11_11-14-22.png
IF it ain't broke, don't fix it.

When you have to fix it, get it fixed, and don't run it like the way you did - when you broke it.- this advice is for all...
 

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