maratrac remote squelch

[k9wkjham]

i have a A7 lowband Maratrac that came to me with a standard A7 head
since i am a geek and like knobs, i wanted to add a control head that gives me one to twiddle.
it seems i have all the parts in a row, in the proper order



per the information in the service manual JU1509 is open and JU1510 is closed as seen in the included pic
the pot is functioning as it should, the voltage on pin 9 of the interconnect external header varies from 1.9-2.6V as it should.
but it has no effect on the function of the squelch circuit.
i must be missing something obvious here

ideas?

de k9wkj

[KitN1MCC]

is the drawer setup for it

[jackhackett]

Have you tried adjusting the squelch pot in the radio? Bob Meister has a couple of articles on the Maratrac squelch over at the repeater-builder site if you haven't seen them yet.

[Bill_G]

I was going to say a Maratrac is a gussied up Maxtrac. The SQ pot is on the RF board. I never knew there was a place on the head for adding a pot, but I didn't have that many customers with them, and they never sparked an interest in me to poke around in the manual. Bet you do have to do something about the fixed pot in the trunk unit. Perhaps just opening it all the way will give you some control up front.

[k9wkjham]

is the drawer setup for it

hence the pic of the squelch board with the proper part #
and the snap of the interface board with the jumpers where they should and shouldnt be

[k9wkjham]

Have you tried adjusting the squelch pot in the radio? Bob Meister has a couple of articles on the Maratrac squelch over at the repeater-builder site if you haven't seen them yet.

well Bob's articles are what pushed me to give this a shot
i spend lots of time absorbing on RB

[k9wkjham]

I was going to say a Maratrac is a gussied up Maxtrac. The SQ pot is on the RF board. I never knew there was a place on the head for adding a pot, but I didn't have that many customers with them, and they never sparked an interest in me to poke around in the manual. Bet you do have to do something about the fixed pot in the trunk unit. Perhaps just opening it all the way will give you some control up front.

well the heads dont get a pot added, as it is a factory assembled option that many drawers have but did not get ordered with the knobbed head
they did not offer this option on anything but low band radios of later production

there has been no joy getting any sort of interaction with squelch setting and the remote pot
and as i mentioned the proper voltages are appearing on the interconnect header as the remote pot is moved
here is a pic of the other end of the squelch/audio board w\showing the internal pot

[jackhackett]

Bill, AFAIK only low band units came with the remote squelch, so if you weren't dealing with those you wouldn't run into it.

They're a bit more than a Maxtrac. They have a separate board for audio which has the squelch circuit on it. That's where the pot is.

It looks like there's also a jumper on that board, JU1202, that needs to be removed (for a low band it should already be out, but wouldn't hurt to check).

According to Bob M. you should then set the remote squelch pot at the 9 o'clock position and with the radio connected to the antenna adjust the pot on the audio board until the squelch just closes.

[k9wkjham]

It looks like there's also a jumper on that board, JU1202, that needs to be removed (for a low band it should already be out, but wouldn't hurt to check).

maybe onto something here
i cant see that jumper on my pics
so ill have to pull the radio back in and lookie for it
the schema shows that JU1202 is in for normal squelch and out for remote
it must be on the backside as i see the traces for pins 1 and 7 of the opamp are on the reverse

ill do that after range time in the morning

[k9wkjham]

well lookie here

if i had been smart enough to look over the schematic instead of just the snippet that is in the RB maratrac section
i would have seen JU1202 !
as you can see that 0 ohm resistor was added in by hand at some point
im guessing that all the boards where pick and placed with out the jumper and when a customer ordered a no knob radio they stuck it on there

works great now
i can leave the internal pot a bit loose and still bump out the noise on some of the louder spots

thanks for getting me to look at the right thing!

de k9wkj

see ya on lowband

[jackhackett]

Good deal, glad to help.