The Great XTS RF Board Repair Saga (Not [M] Approved Method)

Post by **akardam** » Fri Dec 02, 2005 10:21 am

So, as some of you may have gathered, I've been hunting for a XTS 3000 Range 2 RF board for a while now. A friend of mine got a high split 3k that only put out 1/10th of a watt. No bueno.

First thing we looked at, was how much a new RF board would cost from Moto.

$700+ list.

Ouch?!

Ok. Plan B. Beg/borrow/steal a used/junker/NOS board. We searched high and low, trolled fleabay, posted here and elsewhere. No hits. No bueno.

So, I was over at his bouse a couple days ago, and in an idle moment I flipped through the service manual to the RF board diagram pages. We were convinced that the PA was bad, because in all other respects the board performed flawlessly. I found the listing for the PA, and the more I looked at it the more I thought to myself, gee, it looks like that PA module ought to be easy enough to pull off the board and put on a new one.

We cracked the radio open, and looked at it. Sure looks easy enough, we said, so I fired up MOL and started hunting for the part. Up it popped. I looked up from the laptop with a grin on my face, and my friend said "Don't tell me..."

$81 list.

Bueno! Very very bueno!

The order was placed, overnight priority shipping requested. Motorola was contacted several times to make sure it went out. They must have gotten sick and tired of hearing from me by the end of the day.

The module arrived yesterday AM, and after work my friend and another radio geek assembled at the radio geek's house, with me on my way close behind, and started dissassembly. By the time I got there with the PA, they had extracted the RF board from the radio.

Here it began to look like it wouldn't be so easy. In case you've never seen one, the PA is a small pcboard sandwitched between a 1/8" solid heatsink on the bottom and a metal shield on the top, with the lead feet coming out the side. The bottom heatsink sits directly on the RF pcboard, with a small area cutout of the board to allow part of the heatsink to contact the backplate of the radio directly.

Well, the heatsink was inextricably connected to the RF board, and the PA pcboard was inextricably connected to the heatsink. We didn't know if it was soldered or glued (we suspected solder), but we tried everything - hot knife, heat gun, we even sacrificed a solder tip and ground it down thin - no bueno.

At this point my friend's Xray was demanding him home, so he had to leave. The radio geek and I decided to soldier on. We got to thinking, and he looked at me, and said, "Dremel?" I looked back and said, "Dremel."

Now, I can just imagine the shock, horror, pain, that everybody is feeling right about now. Take a dremel to a $700 RF board? Are you nuts?! What did you take a hit of, we want some!! Well, we reasoned, if this doesn't work, we're looking at a new RF board anyway, so let's go for broke.

We started by dremel cutting the PA pcboard off of the heatsink. Goodbye, pcboard. Vaporized. Poof. Gone.

Then we took the grinder and started to grind down the heatsink. Our theory was if we ground it down far enough, just to the pcboard itself, we could drop the new one in its place and glue it down somehow.

As it turned out, it was a bit easier. It was indeed tack soldered onto the RF board with about 20-30 seperate solder points. As I was grinding the heatsink down, I noticed that something was bubbling out from beneath the heatsink. We got an "Aha!" look on our faces, grabbed a leatherman, ran the grinder up to full speed, and a few seconds later, off it popped.

I just about flung what was left of the heatsink across the room in satisfaction.

After that, we cleaned up the board, put down the new module, soldered it in, closed up the radio, and put it on the bench.

4.2 watts out, <=60hz deviation, modulation good. Bueno! Oh so very bueno!

My friend was a happy boy this morning.

Unfortunately we didn't take any pictures, because we hadn't anticipated such a long and involved process. But, we got-'er-dun, and that is all that counts.

Tony Soprano · Post by **Tony Soprano** » Fri Dec 02, 2005 10:47 am

Not to be a pessimist, but unless the PA heatsink is soldered down as it was originally intended, it probably won't last. Proper grounding is essential for heat dissipation and for reducing stress on the module. As long as you baby it it might hold up. Good job on the diagnosis though!

Tony

Post by **akardam** » Fri Dec 02, 2005 11:24 am

Uh... well, it may not have been a Moto spec job, but we did solder it back in as closely as possible to how it was originally. And I figure, even if it only lasts for a while, it'll be worth it compared to a whole new board.

Tony Soprano · Post by **Tony Soprano** » Fri Dec 02, 2005 11:34 am

Sure, I'm not hatin you for it, I just finished the same job for an HT1000 customer and it cost them about $165 with labor. Beats $285 flat rate though. Takes some sack to take it to a Jedi/Cosmo RF board like that, a lot of "real" radio shops won't even try it.

grogling · Post by **grogling** » Fri Dec 02, 2005 12:47 pm

thanks both of you for getting it working. wish i could have been there for the rest of the dremel mess, but akardam was nice enough to bring the remaining scraps from the nasty amputation.

i'm going to take care at making sure i don't use high-power on a continuous basis.

-g-

Post by **wavetar** » Fri Dec 02, 2005 1:09 pm

We use an 80Watt soldering iron with a huge flat tip on it (nickname: Bertha). Let her warm up for about 15 minutes & she makes short work of the solder on the bottom of the Jedi/Cosmo PA...not to mention the PA's in GTX/LCS mobile radios...and those pesky Maxtrac power connectors...and those darned 800 MICOR PA modules...basically anything which requires a lot of heat!

Todd

Tony Soprano · Post by **Tony Soprano** » Fri Dec 02, 2005 1:31 pm

wavetar wrote:We use an 80Watt soldering iron with a huge flat tip on it (nickname: Bertha). Let her warm up for about 15 minutes & she makes short work of the solder on the bottom of the Jedi/Cosmo PA...not to mention the PA's in GTX/LCS mobile radios...and those pesky Maxtrac power connectors...and those darned 800 MICOR PA modules...basically anything which requires a lot of heat!

Todd

We have a Bertha too, good for those GP300 ground battery contacts. The Chipmaster takes care of the PA's and OMPACs, and one of two heat guns take care of the rest. One of the heat guns is a 1500W Makita with a reduction nozzle, you can't beat it if you need brute force heat.

Post by **wavetar** » Fri Dec 02, 2005 2:38 pm

Tony Soprano wrote: We have a Bertha too, good for those GP300 ground battery contacts. The Chipmaster takes care of the PA's and OMPACs, and one of two heat guns take care of the rest. One of the heat guns is a 1500W Makita with a reduction nozzle, you can't beat it if you need brute force heat.

Yes, I forgot to mention the GP300 ground contacts. No problem for Bertha. We don't have a Chipmaster...would love to though. We're a little bit limited without one as far as working on things under shielding (ie - 99% of the components in a Waris radio). Got the same type of heat gun though...real nice...

Todd

Hightower · Post by **Hightower** » Sun Dec 04, 2005 2:40 am

It took three weller WTCPT irons with big fat 800 degree tips to remove these pesky shields and heatsinks. Naturally this takes two people to do and takes about 4-5 minutes ot heating to get the shield off.

Not sure what type of solder Motorola uses, but it has a higher melting point than regular 60/40, and I like that

mancow · Post by **mancow** » Sun Dec 04, 2005 9:51 am

When I worked at Allied Signal I think they called it Eutectic or something similar to that. It's was a 63/37 mix instead of 60/40.

mancow

mancow · Post by **mancow** » Fri Jul 21, 2006 4:41 pm

It looks like I'm in this same boat now.

My XTS3K 403-470 RF final is gone.

What about an HT1000 RF deck PA module? I have a good one around here somewhere. Would that work? If so I might run to the hardware store and grab one of those nasty ass huge soldering irons.

Post by **wavetar** » Sat Jul 22, 2006 3:51 am

Make sure the pin-out matches...there were several different variations of the Jedi P.A. Some had more pins than others. If it looks the same physically, while I've never tried it, it'll likely work.

Make sure the iron you get has the big, flat tips. The regular 'conical' or 'screwdriver' tips won't cut it, regardless of wattage.

Todd

K4RUR · Post by **K4RUR** » Sun Jul 23, 2006 9:08 am

Hi guys,
I checked the Jedi and XTS3000 service manuals and they list the same RF amp part number for both radios, here it is just in case you need it, 5105329v20. I thought they looked similar when I opened the XTS.

Good luck Mancow,
Lowry K4RUR

mancow · Post by **mancow** » Sun Jul 23, 2006 5:24 pm

WTF

According to MOL that part costs $12

Are you sure that's the correct thing (403-470 RF block) ?

K4RUR · Post by **K4RUR** » Sun Jul 23, 2006 5:50 pm

I need hooked on phonics. Here is the CORRCT PA part number, 5105385y10. That's for the XTS3000. It's a different part number for the Jedi, 5105625u04. Sorry about that. I must have left my brain at work.

Good luck,
Lowry K4RUR

mancow · Post by **mancow** » Sun Jul 23, 2006 6:09 pm

Before I order, I want to confirm that number is for the 403-470.

Is that correct? It doesn't say on the MOL site.

Thanks for the help.

K4RUR · Post by **K4RUR** » Mon Jul 24, 2006 12:37 am

Yes, that is for the 403-470.

Lowry K4RUR

Microwave Mike · Post by **Microwave Mike** » Mon Jul 24, 2006 6:59 am

I use a temp controled hot plate to start the removal process.
First I let the whole board come to a temp of about 375 degrees.
I then remove the leads of the amp. Then I remove the brick with
a iron running around 700 degrees. I start with the outer edge and work
the iron under the brick. Takes around 15 minutes. I then clean the old solder from the Rf board, and apply solder paste with a no clean rosen.
Then it is a reverse process, solder the leads of the new brick, then apply
a large tip iron to the back of the RF board behind the brick. The whole Rf board is around the same 375 degrees. It takes a few turns of the Rf board to get a full soldering of the back plane.

The temp of 375 is cooler than the vapor soldering method from the factory.
This method only applies high temps around the Rf brick.
The hot plate is a soldering type, like a plato. It can reach temps of 800 degrees.

mm

kcbooboo · Post by **kcbooboo** » Mon Jul 24, 2006 8:14 am

I'm surprised the components can stand that temp for as long as you seem to have it applied.

I tried removing the PA module from a GTX mobile. There are two ends of the module that are firmly soldered to the underside of the PCB, and each one is about 7/8 x 3/8 inch in area. I used a heat gun which did a nice job once I turned the air volume down and held the gun about 1/4 inch from the area I wanted to heat up. Took about 5 seconds for each end. Of course, in the process, a chip inductor went "pop" and flew off the board, but I managed to recover it and put it back during the repair process. I didn't bother soldering the new module to the PCB, just cleaned all the solder off with a sharp knife and made it as smooth as possible. Also, the plastic cover on the PA module got hot enough to seriously deform, and would probably have come off if it wasn't attached with some kind of epoxy cement underneath.

One of these days I'm gonna have to find someone locally who does SMD repair so I can see and learn the techniques. Seems to be the "wave" of the future.

Bob M.

The Great XTS RF Board Repair Saga (Not [M] Approved Method)

The Great XTS RF Board Repair Saga (Not [M] Approved Method)

and what a happy boy i am...

Brick replacement