Sir tom1970 . . . . . (so 'dat makes you 54yo ?)
Before you jump off the deep end with that
EYE SEE 6 attempt . . . shudder . . . shudder . . .
WAIT ! . . . lets initially do a signal flow path walk thru.
I am referencing to page 20 of supplied
Pee Dee Eff . . . now you go therealso.
My consideration is perceiving that your prior testing was with audio signal input at
X2 and/or
X2 inputs and the final amplified and processed audio output at
Line Output X7.
My analysis would be based upon either a single section of an op amp stage at fault for that random noise burst origin or an internal DC power distribution within one unit being disruptive to one or all of its stages.
Starting at top left corner
X2-X3 inputs and watching the signal flow to the right thru stages . . . .
Initial input to pin12of IC3D output at pin # 14.
From # 14 signal audio output divides to an upper short processing path thru T1 FET and then into IC3C # 10 (its zero crossbar makes it look like an 8 or B).
The lower, longer audio path is thru #6 of IC3B and out #7 and then up to T9 and out of it into #9
of IC3C.
After boosting up within IC3C it goes out of #9 of IC3C and transports a DC signal and initially takes a DC path down and the to the right over to schemas top right corner.
In that area it then routes up into a D6 steering/isolation diode and its selected attenuative resistor and is being 1 of 2 inputs into IC6 INPUT meter driver amp pin # 5.
Going back to IC3C #8 the audio AC signal after passing thru C8 then passes down and to middle left of schema and into pin # 5 of IC4 of a
ULTRA BASS BOOSTING cluster of components and goes out at pin #1 of IC4A.
We will touch upon this area again, when confirming, which position that you had a switch placed in.
We are back to IC3C #8 and thru C8 again, but with audio now going into IC3A pin #2 and amped and processed out as IC3A pin # 1 and is then coupled thru C4 and goes into multiple selective frequency tailoring adjustments which then go into IC6D pins # 13 and # 12 to immediately amp thru and come out #14 and go into an additional mixed stage of amplification at IC6C pin #10 and comes out at pin #8 of IC6 and passes thru steering/rectifier diode D4 with its selected attenuative resistor and is the second input of
INPUT METER amp pin #5 of IC6B.
POINT OF INTEREST . . . . .
IF your popping and crackling is being within the stages we traced so far . . . .
.Question ? . . . . .
are those pops showing on the meter, either as mini or maxi meter blips ?
If so, and since the D4 and D6 are being shown as 1N4148's types and . . .IF . . .they happen to be the more serviceable leaded versions.. . . . . versus SM . . . . . taking a soldering iron and lifting one lead of D6 might then tell you of noise origin being in those few earlier stages.
Then there is the IC3-IC6 possibility by lifting one lead of D4.
We stopped the audio signal flow out of IC6C #8 and if you pass it to the right and go into and loop thru the FX send and return connections its next encounter is being the pin #3 of IC6A.
Now that sole C section of IC 6 can be isolated by no
FX-SEND------to-------
FX-RETURN.
Can you try those two connection conditions to analyze probability of only IC6A at fault . . . . or else its an internal power distribution / avalanche break down fault that's affecting either one or all of its sections.
RELEVANT INFO . ..
FX_SND to
FX_RET circuitry connectivity is shown mid bottom of schema, just above the
DRAWING REVISIONS BOX.
Considering that we now have
FX_SND to
FX_RET interconnected . . . .lets now travel further on down . . .
The Yellow Brick Road ******
Signal is going into IC6A #3 and is amped out at IC6A #1 and travels left to center schema R84 where it drops down to pass audio into IC7A pin #2 . . . .
AND ADDITIONALLY . . . going into a IC8A solid state analog switch 4053 IC8 switch section A that has the option of switching in the output of the earlier mentioned
ULTRABASS amp cluster .
See if your front panel has that selector knob as its being either the 4th or 6th over (BLURRY Pic)
That switch sends turn on voltage to pin #11 of its analog switch section A to add in some degree of low freq audio from its out at the VR2A
ULTRABASS control pot to the left . . . . . that being
IF . . .you don't have that pot already sitting down a lower or no output level .
Now switch between the two bass positions for the possibility of your crackling originating over at the
ULTRABASS cluster.
Otherwise you have continual common audio flowing into IC7A pin #2 and it exits . . . after being amped . . . at IC7A pin #1.
The audio then coming in from C6 takes a short and direct across top route and goes into an analog switch IC8 section B Pin # 2
The lower alternate shaping influenced path is having audio pass from C6 and go down and into
a closed loop tonal shaping cluster with initial entry into IC7B pin #6 and out its pin #7 and then pass down into IC7D pin #13 and out its pin #14 to loop back into pin #5 of IC7B. Confusing? Then just consider all of that adjustment and processing action, just influencing the aidio signal path between IC7B pin 6 to 7. Then you just take the influenced signal path as basically going from IC7B pin
#7 up and over thru R82 and then down into pin #9 if IC7C to be amped and outed at its pin #6 and then to the right to go into pin1 of analog switch IC6B.
Now . . . do you get it . . . . if you use the top section of
SHAPE switch you analyzing for noise origin in IC7A section. If you move down to its alternate position the IC7B,C and D sections are involved.
In our last testing we were merely differentiating as to whether the
SUPERBASS circuitry was the injected noise source.
The final audio path is now being from IC8B pin 15 and passing over to IC9C pin #9 for its amping up and outputting at its pin #8 and down and to the right to line out.
TROUBLESHOOTING PROCEDURES . . . . .
(speshfully deesined fer 'dem/'dose whuts don'ts gots
miimal mimul minnumul minnymal commun cents and toteully nuttin in buklarnin' spear-a-ints . . . . . . a'tall.)
Compliments of IVY league collegiate floor sweeping choremates . . . .
Delmer P.
(ee) Dumbnuttz
Pratley P.
(ee) Peterhaid
SUSPICIONS . . . .
That the pops / crackling might be originating in a particular I C section.
OR . . .that the power distribution portion, within the I C, might be affecting a select or all sections due to developed shot noise or voltage avalanching.
This will also need consideration of the 4053 analog switches .
INITIALCONSIDERATIONOFTWOWAYSONHOWTODOITTOIT . . . . .
We have tracked that audio from each given input and output of every IC and identified those involved pin numbers. As well, all inputs and outputs were defined.
NOW . . .take as simple of testing aid as is a mere 4.7 or 10 ufd E-cap
^^^^^, rated at the highest DC to be found on these components.
^^^^^^ If you are parts rich / blessed and happen to have a 1 thru 5 ? ufd paper /poly cap, that would work as well.
What you will be doing is taking that cap and ind initially . . . .and after
EVERY test . . . shorting out its 2 leads to DC discharge it completely.
You say that you have used sequential probing of audio fed into an aux minor audio amp and seem to have found the " no noise" boundary, if so convinced, feel free to skip ahead to JUST before that point and do this.
You will successfully ground the caps neg lead (not so important/relevant on the conventional paper caps) and use its + lead to solder to or
FIRMLY hold constant connect to the input or output of the I C section being evaluated.
EXPECT . . . .
1 . . . . . No affect at all
2 . . . . . Crackling or popping is still present
3 . . . . . That capacitors presence has now effected a tonal coloration of the sound with its
POPS and
CRACKLES and they are now transitioning to more subtle thumps . . . or maybe swamping on down to no noise at all . . . . until lifting off off the cap.
DISCHARGE THE E-CAP EVERY TIME AFTER TESTING AND MOVE ON DOWN THE SIGNAL PATH.
PHASE TWO . . . .
If uncertain by complete testing of every involved stages above, input and output pins.
Look up the power input pins of all of the involved I.C.'s including 4053's and review the sequential path of those being involved . Starting at audio origin/related IC, take solder sucker / flux / solder braid and remove solder to float that power input pin or lever its tab up out of solder if its being a Surface Mount /Flat Pack.
See if this procedure reveals a particular fault source.
Thaaaaaaaassssit . . . .
The Yellow Brick Road ******
73's de Edd . . . . . . . . . .
One has two parts in their brain, “left” and “right”
In the left side, there’s nothing right and
In the right side, in time, there’s usually nothing left.
.
