RE: [Repeater-Builder] Maxtrac Question

[Bob M.]

Cheaper to just buy another UHF MaxTrac or Radius and swap the PA outright. By 
the time you figure in the troubleshooting and repair time to replace Q2740, 
you'd be better off with another radio and keep the best looking and working 
parts.

Bob M.
==
--- On Sat, 6/7/08, Eric Lemmon <[EMAIL PROTECTED]> wrote:

> From: Eric Lemmon <[EMAIL PROTECTED]>
> Subject: RE: [Repeater-Builder] Maxtrac Question
> To: Repeater-Builder@yahoogroups.com
> Date: Saturday, June 7, 2008, 10:57 AM
> Tom,
> 
> It appears that the final transistor Q2740 is dead, and the
> driver
> transistor Q2730 is running wide open.  The driver normally
> provides about
> 13 watts to the final.  Check all solder joints and verify
> the correct DC
> voltages are present during transmit.  An RF millivoltmeter
> can be a great
> help in troubleshooting this problem.
> 
> The complete MaxTrac service manual 6880102W84 is available
> for download on
> the RBTIP, and Part 4 of 4 covers the power amplifier.  The
> 17.1 MB file is
> here:
>  df>
> or as a TinyURL:
> <http://tinyurl.com/5qoar8>
> 
> Let's hope that the final PA transistor is okay,
> because it (4880225C24)
> costs about $110 from Motorola.  I did a cursory search on
> the Internet and
> found a supplier in Mexico selling the same part for about
> $65.
> 
> 73, Eric Lemmon WB6FLY
> 
> 
> -Original Message-
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] On Behalf Of
> tgundo2003
> Sent: Friday, June 06, 2008 10:52 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Maxtrac Question
> 
> I have a UHF (D44) 40w 449-470 maxtrac on the bench. All
> checks out
> good, except power out. Most I can get out of it is 22
> watts, and that
> happens at 92 on the adjustment scale, any values above 92
> yield no
> difference in power output.
> 
> Here is the strange thing- I get more out (22W) at 441.300,
> and only
> 14w at 467.xxx. Since this is a 449-470 split I would think
> it would
> be the opposite. 
> 
> Anyone have any thoughts?
> 
> Tom
> W9SRV


  

RE: [Repeater-Builder] Maxtrac Question

[Eric Lemmon]

Tom,

It appears that the final transistor Q2740 is dead, and the driver
transistor Q2730 is running wide open.  The driver normally provides about
13 watts to the final.  Check all solder joints and verify the correct DC
voltages are present during transmit.  An RF millivoltmeter can be a great
help in troubleshooting this problem.

The complete MaxTrac service manual 6880102W84 is available for download on
the RBTIP, and Part 4 of 4 covers the power amplifier.  The 17.1 MB file is
here:

or as a TinyURL:


Let's hope that the final PA transistor is okay, because it (4880225C24)
costs about $110 from Motorola.  I did a cursory search on the Internet and
found a supplier in Mexico selling the same part for about $65.

73, Eric Lemmon WB6FLY


-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of tgundo2003
Sent: Friday, June 06, 2008 10:52 PM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Maxtrac Question

I have a UHF (D44) 40w 449-470 maxtrac on the bench. All checks out
good, except power out. Most I can get out of it is 22 watts, and that
happens at 92 on the adjustment scale, any values above 92 yield no
difference in power output.

Here is the strange thing- I get more out (22W) at 441.300, and only
14w at 467.xxx. Since this is a 449-470 split I would think it would
be the opposite. 

Anyone have any thoughts?

Tom
W9SRV

Re: [Repeater-Builder] Maxtrac Question

[Jim Miller WB5OXQ in Waco]

I have had that happen on radios that had been overheated and needed the lead 
tabs resoldered on the output transistors to get the power back up.  maybe not 
your case though.  Usually most radios will make more than their rated power 
especially at higher input voltages.  Sometimes not for long though!  You might 
check dc voltages inside the radio when keyed to make sure you don't get a bad 
voltage sag when transmitting.  Old Regency radios had a bad habit of that when 
the off on switch got weak.
wb5oxq

  - Original Message - 
  From: tgundo2003 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Saturday, June 07, 2008 12:52 AM
  Subject: [Repeater-Builder] Maxtrac Question


  I have a UHF (D44) 40w 449-470 maxtrac on the bench. All checks out
  good, except power out. Most I can get out of it is 22 watts, and that
  happens at 92 on the adjustment scale, any values above 92 yield no
  difference in power output.

  Here is the strange thing- I get more out (22W) at 441.300, and only
  14w at 467.xxx. Since this is a 449-470 split I would think it would
  be the opposite. 

  Anyone have any thoughts?

  Tom
  W9SRV