Need guidance repairing vintage 31 band EQ

[miguelcotaque]

So i thought i repaired a klark teknik dn360 31 Band Graphic Eq but i just tested and audio output is really low i mean mV (barely hear)
I replaced both input NE5532(I/o board) , Replaced Both 7818(psu) regulators misc caps and one of 2 DG308A(Eq Board) All of these Shorted
(initial problem link Need guidance repairing vintage 31 band EQ - Page 1)
Now unit turns on relays click no visual Overheat
So i pluged Xlr to Rca adapters and put some music , before turning on the EQ audio passes through. after relay´s click audio goes to the "inside" and comes out so so dim you nedd to turn the amp to 11 to barely hear it so i need some expert help looking at the Schematic and take a look were most likely is the problem i have no Oscilloscope to test 🙁
What i think may be the problem
#1 Bad conexion inside the relays , unlikely since bowth click , channel a and b but the do get warm
Update Channel B does not work , older problem
#2 Maybe the TL074 is not working properly
*Tested with simple led circit , it works
I assume all NE5534 are the frequency gain stuff so i assume if they don´t work only specific band will be missing (just my assumption)
#3 Rca voltage is too low and needs Xlr input
Not the case since i tested with Pro Xlr console today same issue
Schematic
http://www.cultureocentre.fr/sites/default/files/fichiers/notice_eq_klark_teknik_dn360.pdf
Thanks apreciare the help

 

[JonSnell Electronic]

Don't change things indiscriminately, it is a waste of time and money. All of the quad amps will not have gone down so you will have sound of sorts!
Use basic fault finding procedures.
Supply a signal and does it appear on the first IC? (IC2). If yes follow the signal path. If no check the input relay/transformer.
If yes but no output, has IC2 got + & - supply? If yes, check the IC.
There is a link panel that allows for an output transformer for balanced line out. Is it wired correctly? See page 8 of service manual.

 

[miguelcotaque]

Don't change things indiscriminately, it is a waste of time and money. All of the quad amps will not have gone down so you will have sound of sorts!
Use basic fault finding procedures.
Supply a signal and does it appear on the first IC? (IC2). If yes follow the signal path. If no check the input relay/transformer.
If yes but no output, has IC2 got + & - supply? If yes, check the IC.
There is a link panel that allows for an output transformer for balanced line out. Is it wired correctly? See page 8 of service manual.

i didn´t indiscriminately changed IC all the ones i changed where causing short on the PSU , i traced voltage to all the ICS and they are fine , will trace signal but not entirely sure , is was going to probe the inverting pin and ground (ic1), look for voltage then move to the output , next IC is this the way?

 

[martin martinez]

hey! this is old but, did you fix it? a signal tracer is the tool...!

 

[miguelcotaque]

hey! this is old but, did you fix it? a signal tracer is the tool...!

No e tenido la oportunidad de checar , el equializador prende pero el audio esta muy atenuado , a que te refieres con un signal tracer?
gracias

 

[planet10]

I did not and had the opportunity to check, turns the equalizer but the audio is very attenuated, that you mean a tracer signal?
thanks

English please

dave

 

[nigelwright7557]

Interesting pcb, it seems to be 2 layer (power supply has tracks on top of pcb) yet there are lots of zero ohm links in the audio side.

 

[miguelcotaque]

Interesting pcb, it seems to be 2 layer (power supply has tracks on top of pcb) yet there are lots of zero ohm links in the audio side.

1990 Tech i guess

 

[MAAC0]

Simple signal tracer

No scope? No problem. Use your amp as a signal tracer.

Check if signal is coming to the input pin of the first IC, then move to the next.

Check those KTR008 also.

 

[miguelcotaque]

Simple signal tracer

No scope? No problem. Use your amp as a signal tracer.

Check if signal is coming to the input pin of the first IC, then move to the next.

Check those KTR008 also.

Thanks, good idea
regarding those KTR008 they come covered in some black resin , how do i test them? could they be the problem?

 

[MAAC0]

Try here

Klark Technik schematics?

According to this post they are dual opamps with some resistors.
There must be inputs & outputs.
I believe these kind of resin stuff is called "melt....."

 

[miguelcotaque]

Try here

Klark Technik schematics?

According to this post they are dual opamps with some resistors.
There must be inputs & outputs.
I believe these kind of resin stuff is called "melt....."

Thanks , will do this to test for now
https://www.youtube.com/watch?v=IEcyDzYAsuU
Will have to print the shcematics to go step by step but i hope i find the problem

 

[dotneck335]

Relays are notoriously unreliable. I'd bypass those.