SSlmixed.com Forum
Tech discussion => 4K,6K,8K Series => Topic started by: oyanliz on December 10, 2018, 08:06:34 AM
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Hi,
We have a channel strip where pushing Split or EQ in switch, cuts the signal and stops sounding the incoming signal on the channel. It seems is something wrong in the motherboard. We have replaced all the cards (amplifier, VCA, dynamic, EQ, Logic...) and also we have tryed with another EQ switch card (T82312).
Seems that split and EQ switch are working fine.
I have tryed to find info in the forum, but I did not find any similar issue.
I would apreciate any help.
Thanks i advance.
Regards.
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This sounds to me like it could be a bad connection to the switch card? If I remember right that these are "fork" style connectors, it might be worth giving the connections on the 611 a VERY GENTLE squeeze with a pair of fine nosed pliers.
This was quite a common problem, even on new channels.
Good luck, Andy
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I will check and I will write back.
Thank you so much Andy!
Best regards.
Oihan
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Hi,
I left this issue "for repairing list" until today! I am trying to do another maintenance revision to the console and today have been fighting with this channel Strip.
SPLIT switch and EQ switch are ok. I revised all the wires and continuity between EQ switch, SPLIT switch, EQ card edge pins and Low Pass Filter pot. Everything seems fine (eq card swapped as well), so I suspect that the issue is on LMF or LF gain pot (when I rotate them, makes strange noise).
Tomorrow I will remove a pot from another strip and I will test again.
Does someone know if these pots broken very often? Maybe I am going in a wrong way?
Thanks in advance
Regards
Oihan
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Yesterday I spend all the day doing more tests and have been squeezing the "fork" style connectors one more time, before start replacing the 22KOhm pots. I do not know what happened, but now the channel does not sound. Signal input is ok in the channel, but pre vca does not sound (just a very small signal). I thought it could be the SPLIT selector, so I replaced it, but not success.
So now the channel does not even sound via large fader.
Any help I will apreciate so much.
Thanks in advance.
Best regards.
Oihan
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Hi,
I have been doing some tests. The SPLIT switch is ok and the pot switches of both filters too. Input, VCA, eq and dynamic cards are also working fine. Something in the motherboard, arround eq signal, is not ok, but I can not find the issue. I have attached the schematic with the signal flow issue through the channel strip. When the EQ is not activated, the signal is attenuated on VCA fader (very very low signal) and when it is activated, the signal is cut. In the small fader, dynamic is working and split (filtering) also is working, but when EQ is activated (MON), the signal is cut. EQ switch card have been replaced also.
Can cause any issue a bad pot of the EQ, when EQ is not activated? Is there any critical thing I should check in the motherboard?
Any idea... will be welcome!!
Thanks in advance.
Oihan.
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Hi all,
I never could fix the EQ issue of this strip. Now another issue came up on the same channel strip. The VCA fader it is not working. I have swapped the Amp card, VCA card and Group amp card... all off them working fine.
Now, when routing signal via small fader, the signal is ok before VCA (small fader up, LF and RF switches pushed, INPUT switch pushed and not pushed), the OUTPUT switch of the small fader is on, the signal is cut. Could be something in the logic card? Or multiplexer card?
Is there any relation with the EQ issue? The EQ card and all switch cards and switches are ok... but when EQ is activated, the signal is cut always.
I have updated the issues signal flow diagram.
Any help it will be appreciated.
Thanks in advance.
Best regards.
Oihan
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Hi,
This week I decided to try (one more time) fixing this issue (I have tried several times the last 3 years)… this channel is working fine except EQ. When EQ is activated… signal is cut (in VCA or small fader). EQ switch card is working fine and all pins are making contact with the card. Low and high filters are working fine when SPLIT switch is activated. All cards have been replaced several times… so the issue is in the strip. I measure -18v/18v in the EQ card… should I try replacing EQ pots or so? What can cause cutting signal when EQ is activated?
Thanks in advance.
Best regards.
Oihan
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Hi,
How are you guys? I hope you’re all doing very well.
This morning I spend some time doing maintenance works in the console. As always… I have tried to check and doing some tests on the cursed channel.
Today I realized that the signal it is not cut when eq is ON. The signal is very very low… but it is there… when I move the eq pots… it seems some are working fine and other are not. I definitely have decided to replace all pots… one by one… If any of you have any other idea… it would be nice to hear it… before I do the replacing.
I will write back when I have replaced all the pots… or maybe a few… if any is failing and I find it in the start.
Regards to all!
Oihan
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Hi Oihan,
can you trace the signal on the EQ card?
I understand that the issue seems to be on the channel and not the card. But this might give more clues to what is happening.
Maybe you'll identify a section where it still works but then cuts out a section afterwards and it may lead you to a faulty pot or pot connection or something.
You'd probably need an extender or test jig for that.
Best,
Christian
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Thanks for your comment Christian. I have all extenders for testing and checking the channels… but I don’t have any oscilloscope for tracing the signal around the EQ card.
I will write back soon…
Thanks for answering Christian.
Regards.
Oihan
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Hi Oihan,
great that you have the extenders!
You could try using a software oscilloscope together with a soundcard:
https://www.nutsvolts.com/magazine/article/turn-your-computers-sound-card-into-a-scope
I don´t really have experience with that and would probably use a separate inexpensive interface, just in case I´d hit a high voltage.
But it should work.
In the TV workshop where I did my apprenticeship 25 years ago we used a small audio amplifier box with a probe wire to trace audio signals around the TVs circuits.
You could just listen to them through a tiny speaker in the box. Fun times. What I´m trying to say is that I think for tracing the equipment might not have to be super sophisticated as long as it gives you an impression if a signal is present.
There are also several modern/free VST options:
https://hiphopmakers.com/best-free-oscilloscope-vst-plugins
https://basicwavez.com/best-free-oscilloscope-vst-plugin/
Best,
Christian
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I don't remember which Eq pot, but if a pot9(s) is bad, there will be no signal when the Eq button is pushed down. If the pot doesn't turn smoothly, it should be replaced. Good luck.
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I have found on a number of times that the Filter pots have a dead spot, at the off position. This will break the signal chain when the EQ is engaged.
Secondly, the "follow channel / follow EQ" jumpers on the the main module board have had cracked solder joints, which happen as they get knocked when removing and reinstalling them.
Anthony.
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Hi,
Thank to all for your help! It is very kind of you!!
I have resoldered all main module joints as you mentioned Anthony... no luck. The Filter works fine and when the Filter pots are not at the off position, the EQ does not work when is enganged... so I supose the Filter pots are ok, are not they?
Dave, when you say pot9(s)... are you referring to frequency and curve pots?
Christian, thanks for all the info you have posted... I do not have any cheap interface for trying to do that... but definitelly I will buy a second hand one to learn how to check issues as you mentioned.
Before I start changing the pots... I made some more tests... I can hear a very low signal... moving LF and LMF section pots... seems that audio signal is changed... not sure if signal changes when moving the HF section pots. When moving HMF section pots... nothing changes in the signal... so I will start replacing the HMF section pots... one by one. I do not know if have any sense my assumptions (as I drawed in the schematics). I also have tested each pot ohm variation in place... I know they should be removed for testing... but no one is out of limit when turning the pot.
Thanks one more time... I will post back if I find the faulty pot...
Best regards.
Oihan
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I have not had any trouble with the Filter pots. Sorry I don't remember which ones. probably level? I'm not sure which Eq you have, but the G series Eq has four sections. If any one of those sections has bad pot(s), they will kill the signal when the Eq is turned on. I have three 4K SSL consoles, and it has happened too me, but not very often. I've had pots that grind when turned.
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Don't neglect the Dynamics switch card, particularly the Channel Out switch. Given that this switch changes the order of Dynamics and EQ, I believe the EQ'd signal needs to pass through this card as well, regardless of whether the switch is pressed or not.
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Hi,
Thanks to all one more time!! I would not be able to do all maintenance work in my loved SSL4040E. I finally could fix the channel 31!!
This channel is one of eight SL611G fited in my console.
I have started replacing the frequency pot of HMF section, after cheking the Dynamics switch card (as suggested Chris in his post).
The first pot replaced... I was testing if something have changed... and when I was testing... I have touched the +15/-15 trim pot of HMF.
I have realized that touching one of the pole of the pot... signal was coming!!
I have removed the covering plastic of the pot... and I could see one of the two white cables was peeled and touching the other pole! It is crazy!
So I have added a new heat shrink piece to the peeled cable and a bigger diameter trasnparent heat shrink for protecting all pot poles pins.
The pot works fine, the issue was the short between these two poles.
I have attached some photos as info for anyone who could have a simillar issue in the future.
Thanks to all for the support and help offered in this forum.
Very best regards.
Oihan
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Great detective work!
Congratulations on fixing the channel and thanks for sharing your solution.
Best,
Christian
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That's a new one I have not seen before.
Well done finding it.
Anthony/