samson xm610 odd clipping problem

[mattball826]

samson mixer. xm610

replaced both amps boards from doa repair (shorted outputs many burn resistors and company suggested change boards)..

did put new amp boards in. unit clip indicators come on continuous. beginning to think this was initail problem and customer ran unit like this which blew channels.

is there good way to test just the mixer portion or does it have to have the control lines from teh amps to work. or is anyone familiar of common problem making unit clip. all dc volatges are good. i scope output and seems to be problem on lower half of signal (not as symmetrical as would think it should be). its not just one channel in mixer either. it is all. i removed efx board so its not that either.

iow i am trying to decide if i can troublshoot using ext dc and see if the problem in mixer section.

i recall similar problem with behringer box mixer that was a bad diode. that symptom is kind of what this xm610 is doing.

ideas?

[Jazz P Bass]

Strange that the clip LED's come on.
Seeing that the power amp board "tells" them to turn on.
And both amps are new.
The LED's have +15Vdc on them at all times.
When the power amp detects clipping, the clip circuit "gives" the LED's ground & they illuminate.
Do the separate amplifiers work?
Are they both clipping?

[mattball826]

new amps boards. initial problem was doa with many burned components on those boards.

the units works now but has excessive clipping and indictator leds come on and flash when the audio is clipping. what else is there is very hf noise with the audio l and r lines as well (at plug pins 5 and 7 going to pow amp boards).. i changed ic711 for giggles since 5 and 6 of that ic were clean. noise was on pin 7.

problem is the units is clipping (distorts) at low to moderate volumes and really bad at higher amts.

signal out of rec out and main out mon out 1/4" sends are clean.

yes both chs clip no matter the power mode

i verified power supply was ok too. just trying to find out when else is common to these to cause this problem. worked on many 910's and 610's and not seen this kind of problem. audio seems clean but at moderate or louder volumes distorts bad. with sig gen looks liek low half of op is being clipped. bias check ok, nothing off there. one of the first things i looked at.

i hope they didnt send me bad amp boards.

been nice if i had another unit like it to test the replacement boards.

[mozwell]

I hope the sch helps if you dont already have it.

If all the power supply lines are good, +/-82VDC, +/-24VDC, +/-15VDC, +5VDC & 48VDC check they have low ripple.
Are all the fuses ok. Pull them & check them.

We need to work out where in the chain you are getting asymetrical signal.

Does the signal look ok at "rec-out" rca jacks, does it look ok at "main-out" jack, does it look ok at "mon-out" jack, does it look ok on the "aux-send" jack

On the 14 way connector AN102, do the signals & power supplies look ok.
On each amp board, is there any DC offset on the speaker outputs.
Is the speaker relay pulled in

The clip led is driven from Q101, Q102, Q103, Q104. Are there working ok, or is there a difference in voltage between the bottom end of R123 & R127....

lets find out where the signal goes funny & we can go from there.

[mattball826]

problem solved. i feel like dummy

i overlooked bad cap c107 wide open on esr meter. voltage was around-72v but ripple through ceiling. funny unit did not really have a hum i would have suspected it would. next time i check that more thoroughly instead of on the pin connector.

new boards are fine too. 14mv idle.

now i get to reassemble entire unit and mixer board/panel!

thanks for helping me stop chasing my tail.

[Jazz P Bass]

Rule #1: Check the power supply.
Glad you got it fixed.

[ozzie.freddo]

schematic not downloading

I only get a blank page when I try to download the schematic of the Samson XM610. Only a newbie here and could do with some help in finding it, thanks.

[Enzo]

Hi welcome. Nothing you are doing wrong, it is a blank file, the result of a server crash we had here a while back. Hopefully someone can repost it for you. What part do you mostly need?

[ozzie.freddo]

missing schematic

Hi welcome. Nothing you are doing wrong, it is a blank file, the result of a server crash we had here a while back. Hopefully someone can repost it for you. What part do you mostly need?

Thanks for the welcome, I'm mainly interested in the output stage where Q123 has exploded.

[Enzo]

If that happened, your C5200s are probably bad, or one of them anyway.

[ozzie.freddo]

If that happened, your C5200s are probably bad, or one of them anyway.

.
Yes, maybe. Thanks for the new PDF, but, it too, is just coming up blank.

[mozwell]

try this

[ozzie.freddo]

thanks, got it, it'll be a big help.

[ozzie.freddo]

If that happened, your C5200s are probably bad, or one of them anyway.

It would seem as if many components on the positive side are affected. Q121 and Q123 have exploded; R157, 159, 145, 147, 144, 140 are o/c; D112 is s/c; ; D109 and Q120 are dubious but Q129 and Q125 (the C5200s) seem to be ok (with a simple in-circuit diode test showing their PN junctions to be intact)

Somebody dismantled the unit before me and I have no information on the failure conditions but am wondering if it is possible that the cause is power supply related (although the other channel is apparently (visually) undamaged.

Any thoughts, or known failure modes for this unit?

PS I am just a volunteer visiting a 3rd world country

[Jazz P Bass]

My thoughts on the failure are 'it is what it is'.

Often times it is too late to ascertain 'why' it went.

Or how.

But it did.

And then you get the 'stick another fuse in it'.