Zetron 37 max power up problem

[hamzagi]

hello,

I've bought a Zetron 37 max to be used with two GM340 radios (GR500).
wiring is finished, i've tested the ouput voltage of the pin A+ , before connecting the Zetron 37, i found 13V
after connecting the 37Max it doesn't power up and the A+ voltage become 8V

i've used the second 37max, but it was the same

is there any suggestion about that ?

thanks

[Will]

There is a wiring change, remove the A+ lead from the transmit radio to the 37Max, it can burn out the fuse in the receiver radio. The 37 Max only needs power from the receiver radio.

[hamzagi]

It is already connected to A+ of the receiver only

regards

[Will]

So you do not get 12 volts at the Zetron 37? Disconnect the cable to the transmitter radio. Do you have 12 volts at the Zetron now?

[hamzagi]

hi,
and what if I'll connect the Zetron 37Max to another 12V power source ?
only the two pins +12V DC and Ground.

[Will]

You could have a bad source of 12 volts on the RX radio. Yes you can get the 12 volts from the same feed as the radios use, be sure to add a 2 amp fuse in line to the 37 MAX.

[hamzagi]

I've connected it to 12V power source and it was working, led status was green
what do you think ?
is there any problem with the radios A+ output, or there is a ground problem ?

[hamzagi]

I've tried with a third radio but is the same problem

[Will]

I've tried with a third radio but is the same problem

You probably have a wiring problem.

There IS a known problem where the TX radio sucks A+ thru the RX radio and kills the A+ output on the RX radio.

The TX radio should only have four wires, GND, Mic audio, PL tones, and PTT in the Zetron 37 configuration.

The RX radio should only have 4 wires, A+ , GND, RX flat audio, RX un-mute (RUS) to the Zetron 37.

So you will have to use the A+ from the power supply thru a fuse to the Zetron 37.

[hamzagi]

i've connected the zetron as you requested.
now the COR led is always on.
i've activated one user pl, it seems to detect the pl tone.
but now i'm not able to send dtmf commands anymore
each time that i send a dtmf digit i see the status led going on and off

[Will]

Do you have the RX radio correctly programmed?

RX PL/DPL UN-mute to active low on pin 8

RX audio jumper set to flat un muted.

Are your DTMF tone at the correct transmit deviation?

[hamzagi]

now i can access to the 37Max and activate pl
i've made a test with PL 77 and i've seen that the transmit led of the controller was on.
but the actual problem is that on the handheld radio it detects carrier , channel led go green, but without audio.


i have two motorola gm340 on that repeater

RX radio config / Pin8:Carrier detect RX audio accessory output: Flat Unsquelshed
one channel , with TX/RX frequency is the same without PL activated

TX radio config: Pin3: Voice&DataPTT
one channel , with TX/RX frequency is the same without PL activated

in case that problem is caused by deviation, how can i adjust it with an oscilloscope only?
what i thought is even if there is a problem with deviation we can hear at least a noise on the handheld radio

[Will]

The TX radio needs the PL tones from the 37 Max fed to the flat input. a 10k resistor in line at the TX radio for isolation.


So the TX radio has four wires from the Zetron 37 max:
Zetron GM Radio
Ground 2 BLACK AUX pin 5 and 7
Ground 4 BRAID No connection
TX Audio 5 BLUE AUX pin 2, MIC Audio
PTT Output 7 ORANGE AUX pin 3, MIC PTT
TX PL/DPL 10 GREEN 10k resistor to AUX pin 5, Flat TX Audio