GM300 not transmitting PL/DPL

Victor Xray · Post by **Victor Xray** » Fri Jul 07, 2006 8:02 am

Anyone ever run across this problem?

10W GM300, model M04GMC29C3_
Transmits great but will not produce a PL or DPL no matter what tone is selected in the RSS. Reading back the radio confirms that its set for Tx DPL or PL, but the actual transmit carrier is CSQ.

Any ideas?

Max-trac · Post by **Max-trac** » Fri Jul 07, 2006 9:07 am

Was it working before?
How is the mic modulation?
Make sure the channel is not set up for any other signaling.
Make sure the PL inhibit pin on back is not switched (someone may have set it up for an external encoder).

(When you do a complete alignment, there is a setting for both PL and DPL total deviation level, it is unlikely, but possible they are set for zero. )

Victor Xray · Post by **Victor Xray** » Fri Jul 07, 2006 9:32 am

Since this is a 10w radio, my guess is that it was the RX radio from a GR500 or similar repeater.

Thanks for the reply, I'll check those things next time I'm around.

Victor Xray · Post by **Victor Xray** » Fri Jul 07, 2006 12:17 pm

Some answers:

Max-trac wrote:Was it working before?

No idea if Tone encode was working before I got the radio. I would assume so; however if this was just the RX radio of a repeater, tone encode probably was never used/tested.

Max-trac wrote:How is the mic modulation?

Verified good audio from the mic.

Max-trac wrote:Make sure the channel is not set up for any other signaling.

No other signalling set

Max-trac wrote:Make sure the PL inhibit pin on back is not switched (someone may have set it up for an external encoder).

PL inhibit pin is set to Low in RSS ("General I/O"), and nothing is attached to the accy port. Just radio, antenna, & mic.

Max-trac wrote:(When you do a complete alignment, there is a setting for both PL and DPL total deviation level, it is unlikely, but possible they are set for zero. )

I checked and both are set in the middle of the soft pot, not Zero.

Thanks for the suggestions. Any other ideas? Oh, and I verified that PL/DPL decode does work, just not encode.

kcbooboo · Post by **kcbooboo** » Fri Jul 07, 2006 2:09 pm

The GM300 has three pots on the RF board. One adjusts the receiver's squelch and is nicely labeled SQ. The other two affect the VCO and REF modulation signals. It's possible that the REF MOD pot is bad or has been turned down, although I don't think it would disable transmit PL/DPL, just make it quite soft. DPL is harder to modulate than PL. At least the pots should be 1/2 way. I've never seen an adjustment procedure for these, so I can't help you further.

Try selecting a high frequency PL, such as 192.8 or higher, and see if anything comes out. The PL/DPL deviation is not separately adjustable; if you've got 5 kHz of MIC deviation, then the PL would come in between 700 and 1000 Hz deviation just beecause of the component values that are used.

If you have a service manual and a scope, you can check the two PL/DPL lines coming out of the microprocessor, and follow the signal as it goes through a couple of op-amp filters. One of those could be a problem.

There are more jumpers on the GM300 logic board than in a MaxTrac. I don't know if one of them would have any effect on transmit PL/DPL.

Bob M.

Victor Xray · Post by **Victor Xray** » Fri Jul 07, 2006 4:52 pm

Thanks Bob. I tried a large selection of various PL and DPL tones but none appear on the Tx carrier. If I get free time, I'll crack her open and poke around. Unfortunately, I'm totally swamped with too many other tasks pending (real work) so to the shelf she goes.

Post by **wavetar** » Fri Jul 07, 2006 6:26 pm

Victor Xray wrote:PL inhibit pin is set to Low in RSS ("General I/O"), and nothing is attached to the accy port. Just radio, antenna, & mic.

I think that's your problem. Change that pin to "null" and see what happens.

Todd

Victor Xray · Post by **Victor Xray** » Fri Jul 07, 2006 7:12 pm

Hahaha, could it be that simple?! I'll let you know on Monday.

Victor Xray · Post by **Victor Xray** » Mon Jul 10, 2006 11:18 am

Well, pin 6 was already labeled as NULL 1, so that wasn't it.

Code: Select all

                       ACCESSORY CONNECTOR CONFIG
                       ──────────────────────────
 INT Accessory: None       EXT Accessory:       General I/O     Custom: N


   PIN#          DESCRIPTION         DATA DIR      DEBOUNCE     ACT LEVEL
    4            External Alarm       Output         No           High
    6            NULL 1               Input          No           Low
    8            NULL 1               Input          No           Low
    9            Emergency Switch     Input          Yes          High
   12            NULL 1               Input          No           Low
   14            NULL 1               Input          No           Low

Another idea?

proff · Post by **proff** » Mon Jul 17, 2006 4:28 pm

after working on motorola radios for the last 5 yrs
i can say I am sure it is your ASFIC
the GP300 has 2 electro caps break off but with yours it is the ASFIC chip is faulty.
As long as your haven't tweeked any POT's on the boards

K8TEK · Post by **K8TEK** » Tue Jul 18, 2006 4:19 am

Put it on a service monitor. See if you are getting ANY PL/DPL

proff · Post by **proff** » Tue Jul 18, 2006 5:39 pm

if you haven't got a service monitor, the between the I.F. chip and the quadrature coil/tank cct you wil;you see 3 lands on the PCB. One of them is the discriminator Audio out. with the help of a CRO you will see the subtone there.
if it is there your fault is the ASFIC chip

GM300 not transmitting PL/DPL

GM300 not transmitting PL/DPL

No TPL or CTSS tones from your GM300

No PL tones