Phonic power pod 740 question

[nosaj]

i have a phonic power pod 740 mixer/pa
complaint is low volume on ch1 and ch2

Ch1 and ch2 are Hi/z and ch3 and ch4 are Super Hi/z

What is Super Hi/z?

After that plan of attack is to check the rails. The volume is lower on ch1/2 using a fm radio via TRS cable, I am listening through the monitor jack to hear this.

nosaj

[Mick Bailey]

Hi/z is TRS balanced mic and line level sources. Super Hi/Z is unbalanced TS guitar or bass input. I'd call them just low and high impedance myself.

[Jon Snell]

Lost in the Chinesium translation into pigeon English is what it is.
Ch1 & 2 XLR inputs are the usual low impedance inputs, with phantom option through 6k8 feeds and the TRS jack is around 10k eventhough they have 100k input load resistors, the Tips feed into a 3k9 that tie T & R together before feeding them into a 4k7 to ground load.
Ch3 & 4 feed a 4558 with a 500k input load. OK for Shure Unidynes and guitar work.

[nosaj]

Ok i replaced the caps going around the inputs and the levels are all ok now on the 1/4 TRS and the XLR inputs
except ch 2 XLR no sound but the TRS works just fine. I seem to be overlooking something. If anyone hass any suggestion I'd be very grateful.
Thanks,
nosaj

[x-pro]

The XLR input circuitry is simple. "There are three parts in two rows".
Either C202 C203 is open, or C237 C238 is shorted, or the switch pins in the TRS are broken, or the pins in the XLR connector are broken.

[nosaj]

I found a capacitor leg that was touching another part of the circuit. grounding out the XLR. Now that I undid that I do get signal but it's low and muffled from the CH2 xlr, while CH2 TRS is fine .

. CH1 TRS is the low and muffled even after replacing the jack and surrounding caps, While CH1 XLR is fine. The caps in the dotted box I cannot find on the PCB.
nosaj

[x-pro]

Is +48V phantom voltage applied to both pins of the XLR connector when it is turned on?

[nosaj]

Yes Phantom power is on both pins on all channels.+48v
nosaj

[x-pro]

Now that I undid that I do get signal but it's low and muffled from the CH2 xlr, while CH2 TRS is fine .

. CH1 TRS is the low and muffled even after replacing the jack and surrounding caps, While CH1 XLR is fine.
nosaj

Is it just as you wrote it, or are you confused? It's very strange.
XLR input - microphone input. TRS line input. Watch the level of the input signal!
Only passive elements on these inputs (capacitors and resistors) and TRS contacts are responsible for all such "characteristics". It is possible that the R106, R107, R110, R111 ratings in the CH1 channel have changed.

[x-pro]

There may very well be a fault in the PAD switch. Its contacts.
I have a Yamaha EMX68s on my desk right now, with similar symptoms of malfunction. And the culprits are these buttons.

[nosaj]

Ok I will follow the signal up to the Pad switch and see how it goes.
Thanks,
nosaj

[nosaj]

Ok i have discovered I have the wrong service manual for the PA.
Can't upload it to the forum so I gdrived it.
Only problem now is ch2 XLR is low volume. Replaced the electrolytics surrounding and the TRS jack. Still Low volume I premise I should be checking Q101 or Q102 for signal.

Nosaj

Previous manual all TRS had muting jacks this one only has stereo jacks.

[x-pro]

Is the TRS input normal?
And XLR is downgraded?
How so, if they have one input line on Q101, Q102 ?
Unless there's a microcrack in the printed conductor.

[nosaj]

Is the TRS input normal?
And XLR is downgraded?
How so, if they have one input line on Q101, Q102 ?
Unless there's a microcrack in the printed conductor.

I'm really not sure I did make some jumper wires from the xlr to the next point in the circuit(bypassing the trace and it didn't make a difference. It's really weird.
nosaj

[g1]

Can you post a screenshot of the input circuit from correct schematic?
Not sure what you meant about 'muting jacks' regarding 1st post schematics, did you mean switching jacks?