Jaws Mark 2 LC7120

[3pinplug]

Hi all
At my local boot fair today and managed to pick up a little jaws 2 for £3.
Problem 1
Tried it and had 5 watt ch1 & 40 but only 2 watts output on ch20, opened it up and took speaker lid off then had 5 watts all channels, put speaker lid back on radio and it drops to 2watts again ??? Can’t see speaker is hitting anything.
Doesn’t appear to have receive and sometimes makes a squeal on PA but does have mod in PA.
Are these common faults for this radio?

Any info on the LC7120 version as can only info on the LC7131 version.
Thanks
Mark

[ChubbyChops]

Is there any transmitted audio?
Any noise when you run your finger over the audio amp pins?
Speaker has a magnet on it so may be pulling on a coil with a loose core.....

[14CS06]

Hello

Schéma LC 7131

@+
Claude

[3pinplug]

Ok so if i changed speaker to non magnet that would sort it? I will try teansmit audio in morning and check back on if it there, i did run finger over Audio chip and got the hum so assumed it ok.
Also thanks For schematic Claude, thats the one i have it shows the LC7131 PLL mine has the LC7120 or is everything else the same - just different PLL chip?
Thanks both fir your help.

[ChubbyChops]

You need to find what the magnet is influencing and fix it.
All speakers have magnets in them.

[Buick Mackane]

The speaker might be a replacement which is to big hence the problem, Upload a pic of it, Also check that the board screws are tight, No receive could be a few things, Dried out caps, Transistors, Faulty or dirty switch contacts.

[3pinplug]

Ok will take a pic of speaker / lid and put some dimensions on it.

[The Collector]

The cases going back on may be moving the chassis a fraction as they're usually a tightish fit. Perhaps check all circuit board and any earth mounting screws etc just in case. Other than that I'm pretty clueless

[14CS06]

Hello

LC 7130

@+
Claude

[3pinplug]

Hi Claude
Thanks for the pic of the LC7131 insides, I enclose a pic of my LC7120, the two are very diffrent in appearance so the schematic fpor the LC7131 will be diffrent by the looks of it. No idea why it opens the other way up when you enlarge the pic.

jaws4.jpg

[3pinplug]

Its not the speaker causing the problem with the RF its the cover itself, i had a spark off the case as the end of the RF driver screw has 13.8V on it so I accidentally touched this with the cover when carryoing out trials, not sure that is right is it?
The speaker is 0.25 wats and 8 ohms whereas claudes pic shows 0.5ohm 8 watts so is this the right speaker? The speaker mounting screws also look to be exceptionally long so will change these. Audio can be heard on the PA facilty but when I transmit it is way off frequency so no way to verify it on transmit.
Anyone have the schematic or alignment instructionsfor the LC7120 version as looks like they may be different , but I will await further advice as I am unsure on this. Heres some pics:-

jaws3.jpg

jaws2.jpg

jaws1.jpg

[ChubbyChops]

The speaker looks correct at 8ohms but the screws do look long, although that may not cause an issue.
There should be an isolating washer between the driver transistor and the chassis.

[14CS06]

Hello

IRRADIO MICRO 80
Platine : 482802C











@+
Claude

[14CS06]

Hello



















@+
Claude

[14CS06]

Hello















@+
Claude