"while you have q1 out you should try
connecting a 220k resistor from pin4 of
the 6110 to 12v
this will allow you to verify that it is still working"
Too late for that, and I'd rather avoid taking it out again as I'm not the best at de-soldering. Q38, R123 and R121 are all correct and soldered properly.
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moogah
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What is the differece between the signals for the 662 and 6110? taking the voltage at pin 1 of IC15A I get .5V. Without the datasheet for the 536 I'm not really shure how to go about figuring out what the output of Q3&4 should be and how that will affect Q1&2. One thing is sure, even after replacing all four with some I had there is still 12v at pin 4 of IC15B.
Here are some measurements that may be of interest. I've yet to make any sense of them.
By touching R3 to R146 the colllector of Q1 goes to 12v and the collector of Q3 goes to .5V. The collector of Q4 is always at 12V. This makes me suspicious of Q2, as I don't believe it should pass any current untill Q4 'sinks' some from it, perhaps I'm wrong and it is supposed to be 'normaly open'. In either case, it doesn't make much sense to me why Q1 still opens and closes. I've also considered that .5V is a bit low to be opening Q3, but clearly it is getting open.
Lets see if I understand how the gate signal works with the VCA. Starting with the envelope:
The base current for Q37 goes something like this:
Vs = ~5v (is this the correct voltage from R3?)
R146 and R144 form a bias divider providing ~3v to the base of Q37, assuming that it is indeed a current source. Now, in order to proceed I'd need to have little Re for a sc536, and so far I can't find a datasheet for it. Connecting up a simple breadboard circuit with a 10k load it drew more current than my bench PSU could provide (~1A).
Is C72 just a bypass/filter cap? C55?
Why does the VCA take inputs from the gate and pulse? I can understand using a pulse to trigger an evelope, but don't see it's purpose in a VCA, is there an actuall VCA Env that I am unaware of?
Here are some measurements that may be of interest. I've yet to make any sense of them.
By touching R3 to R146 the colllector of Q1 goes to 12v and the collector of Q3 goes to .5V. The collector of Q4 is always at 12V. This makes me suspicious of Q2, as I don't believe it should pass any current untill Q4 'sinks' some from it, perhaps I'm wrong and it is supposed to be 'normaly open'. In either case, it doesn't make much sense to me why Q1 still opens and closes. I've also considered that .5V is a bit low to be opening Q3, but clearly it is getting open.
Lets see if I understand how the gate signal works with the VCA. Starting with the envelope:
The base current for Q37 goes something like this:
Vs = ~5v (is this the correct voltage from R3?)
R146 and R144 form a bias divider providing ~3v to the base of Q37, assuming that it is indeed a current source. Now, in order to proceed I'd need to have little Re for a sc536, and so far I can't find a datasheet for it. Connecting up a simple breadboard circuit with a 10k load it drew more current than my bench PSU could provide (~1A).
Is C72 just a bypass/filter cap? C55?
Why does the VCA take inputs from the gate and pulse? I can understand using a pulse to trigger an evelope, but don't see it's purpose in a VCA, is there an actuall VCA Env that I am unaware of?
Last edited by moogah on Fri Oct 28, 2005 1:52 am, edited 1 time in total.
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Guest
your 6110 is probably bad
you might be able to get another one from ladyada
id suggest socketing it if you get it
as far as the envelope section goes
there are actually two envelope generators
the main generator is the one labeled envelope on the schematic
this is created by a pulse generated by q38
the vca envelope generator is created by this same pulse
and by the gate signal created by q36
the gate signal merely turns on the vca circuit
the pulse signal generates the attack and decay
via q32 and q31
q31 creates the current that controls the amplitude of the vca
q1 through q4 are merely current mirrors to reflect this
current appropriately to the 6110
since it is different than the 662
you might be able to get another one from ladyada
id suggest socketing it if you get it
as far as the envelope section goes
there are actually two envelope generators
the main generator is the one labeled envelope on the schematic
this is created by a pulse generated by q38
the vca envelope generator is created by this same pulse
and by the gate signal created by q36
the gate signal merely turns on the vca circuit
the pulse signal generates the attack and decay
via q32 and q31
q31 creates the current that controls the amplitude of the vca
q1 through q4 are merely current mirrors to reflect this
current appropriately to the 6110
since it is different than the 662
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moogah
- Posts: 186
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moogah
- Posts: 186
- Joined: Sun Jun 19, 2005 8:51 pm
Well, I've just breadboarded a version of Q1-Q4 and it seems my measurements made before aren't unusual except that the voltage at the output is just 10X too high. Using a 10k load on the breadboard I got an output of 3.2v corresponding to .00032A, 320uA if I'm not mistaken. This is just about right according to the 6110 datasheet (although it hints that 200uA would be better). Transferring these measurements to the x0x and assuming it's also putting out ~300uA I get an impedance at pin 4 of about 37K to produce 12v. I'm a novice at the math tho, so I don't put much weight behind that calculation. In fact, I can get the output of the breadboard to read 12v but using a load of 1.5M, this could make sense as a busted IC may have an exceptionaly high impedance. Oh Well.. Time to go shopping. Can someone tell me it ~.5v at pin 1 of IC15A sounds correct (while the gate is on)? Is it possible the in impedance at pin 4 has gone so high that while the mirror outputs correctly the resulting voltage is 10X what it should be? Does my math look ok?
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Guest
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moogah
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- Joined: Sun Jun 19, 2005 8:51 pm
To be clear, the .5v at 15A switches with the gate, that appears to work as proper.
Ok, I think this all makes sense then. Thanks for taking all the time to answer my questions. I've got plenty more if you still have the patience to answer
Also, I hope you don't mind me taking snippets of your posts to contribute to Jonnay's x0xd0x once I get this all sorted.
Given that the 6110 needs to be replaced before I can move on with the VCA I'm going to start working on the envelope decay issue. The circuit itself seems simple, the 4066 handles the logic for wheather or not accent is applied while C62, Q40 and Q41 create the AR, I'm not sure if the accent is stuck on or that the accent can even be changed before the sequencer has been assembled, so perhaps the envelope works like it should at the moment. I see that VR4 (cutoff) is connected to VR5 (env mod) and that it's the cutoff pot that connects to TM3 although I thought that was to adjust the resonance value. I'm not aure at the moment how the signals at the wiper of VR3 and R47 will interact, I'll breadboard something up tonight. VR5 links to Q10 and Q11 so I would assume the controll current is generated here. I'm not sure how a 4066 works nor exactly how the env mod is connected to the decay. Is it true that the second deck of VR6 does nothing?[/quote]
Ok, I think this all makes sense then. Thanks for taking all the time to answer my questions. I've got plenty more if you still have the patience to answer
Also, I hope you don't mind me taking snippets of your posts to contribute to Jonnay's x0xd0x once I get this all sorted. Given that the 6110 needs to be replaced before I can move on with the VCA I'm going to start working on the envelope decay issue. The circuit itself seems simple, the 4066 handles the logic for wheather or not accent is applied while C62, Q40 and Q41 create the AR, I'm not sure if the accent is stuck on or that the accent can even be changed before the sequencer has been assembled, so perhaps the envelope works like it should at the moment. I see that VR4 (cutoff) is connected to VR5 (env mod) and that it's the cutoff pot that connects to TM3 although I thought that was to adjust the resonance value. I'm not aure at the moment how the signals at the wiper of VR3 and R47 will interact, I'll breadboard something up tonight. VR5 links to Q10 and Q11 so I would assume the controll current is generated here. I'm not sure how a 4066 works nor exactly how the env mod is connected to the decay. Is it true that the second deck of VR6 does nothing?[/quote]
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moogah
- Posts: 186
- Joined: Sun Jun 19, 2005 8:51 pm
Ok, I've redrawn the schematic for the envelope this afternoon to break it apart and figure it out. Here is what I've got so far:
A pulse comes into the envelope through D37 and R152 which creates the envelope through C62, Q40 and Q41. I'm not sure what the FET does, but I think it's something like a current sink. While the accent is off R138 connects to VR6 (decay) which I believe shifts the bias up or down such that C62 discharges in a different region creating the longer/shorter decay times, I believe that the 3 diodes create quiesent bias but I'm not sure why 5.333 is applied to the bottom one. I assume there really is no attack phase. While accent is on IC12B shorts the decay knob out of the circuit. While accent is off the output of Q41 is sent to VR5 (envelope mod) which attenuates the signal and sends it to the controll section of the VCF (Q9, Q10, Q11). When accent is on IC12A sends the envelope signal from Q41 to VR7 (accent) which then attenuates the signal and sends it to the VCA and the second deck of VR4 (rez) the signal to VR5 (env mod) is still connected but remember that the decay time has been shorted.
A pulse comes into the envelope through D37 and R152 which creates the envelope through C62, Q40 and Q41. I'm not sure what the FET does, but I think it's something like a current sink. While the accent is off R138 connects to VR6 (decay) which I believe shifts the bias up or down such that C62 discharges in a different region creating the longer/shorter decay times, I believe that the 3 diodes create quiesent bias but I'm not sure why 5.333 is applied to the bottom one. I assume there really is no attack phase. While accent is on IC12B shorts the decay knob out of the circuit. While accent is off the output of Q41 is sent to VR5 (envelope mod) which attenuates the signal and sends it to the controll section of the VCF (Q9, Q10, Q11). When accent is on IC12A sends the envelope signal from Q41 to VR7 (accent) which then attenuates the signal and sends it to the VCA and the second deck of VR4 (rez) the signal to VR5 (env mod) is still connected but remember that the decay time has been shorted.
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moogah
- Posts: 186
- Joined: Sun Jun 19, 2005 8:51 pm
AL:LKJ:LSKJDF:LKJLKGJQWPUDH:QWJKJCDSLJLSHGD:LJKA:LSKJFKJHGLKSAJDF
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!11
xOx #141 LIVES! The 6110 proved to be the only hurdle in the assembly process. All that is left now is the tweaking of tuning and VCF parameters. There is a small issue with the digital section (some of the LED's act strange), I'll post the solution when I find it.
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!11
xOx #141 LIVES! The 6110 proved to be the only hurdle in the assembly process. All that is left now is the tweaking of tuning and VCF parameters. There is a small issue with the digital section (some of the LED's act strange), I'll post the solution when I find it.
Please be positive and constructive with your questions and comments.