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 9710 VCA/Mixer - Test #4 & #6 
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Joined: Sat Mar 07, 2015 6:23 pm
Posts: 10
Post 9710 VCA/Mixer - Test #4 & #6
Hi,

We are nearly though verifying this unit.

In step #4 there was a slight tone with the Pan control at full "R"; when turning the "Modulation Null Trimmer" there was no discernible difference in the tone.

In step #6 there was a modulation sound, but the carriers were not of the same volume. The original carrier was much more dominant than the modulating signal.

There are remedial steps listed listed we are not sure if the step #6 is the expect behavior. Do we treat this as failing step #4 and step #6 or just step #4?

Thanks,
Nic & Tenchi.


Sat Feb 27, 2016 8:22 pm
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Post Re: 9710 VCA/Mixer - Test #4 & #6
Hello Nic & Tenchi.

The “trouble” checks following each Testing section are only very general. For example, for Test #4
check IC4, Q3, Q4 or associated parts, and, IC6 and Js 3 and 6 wiring – this simply implies verifying
the parts are the ones specified and with the proper polarity, good soldering, etc. It is rare for parts to
be the trouble due to defects, though they can fail if an accidental short-circuit occurs (ie board
soldering comes in contact with metal while powered or probing for voltages results in contact between
two nearby but separate circuits).

Specific to the trouble you describe, the R24 Modulation Trim not affecting the signal output in Test #4,
check the middle, wiper terminal of the trim (also the end of R27 which connects with the wiper
terminal) for a DC voltage which varies from negative 12VDC to positive 12VDC as the disc is adjusted
from one extreme to the other.

This variable voltage should work to minimize the signal level at the VCA A output. It might not be
eliminated, particularly if you are going into a sensitive input, but there should be a significant
difference between the levels heard at the extremes and the dip which occurs at an intermediate
setting of the trim corresponding to a VCA ADSR “off” control into the VCA A section. Looking at the
one in P9700S here, it is set about mid-rotation for this condition.

If this checks to be OK, below are some other DCV readings in the VCA A section
going sort of left to right from IC6c to IC6D according to the schematic. Set ADSR
controls to 9:00 and modulator to Cycle.

IC6pin9 0V
IC6pin10 0V
IC6pin8 4.9
R34 wiper terminal (appx. calibrated setting) 4.4V
IC4pin10 5v
IC4pin8 5v
IC4pin2 -0.73
IC4pin3 -0.74 to -0.91
IC4pin1 -0.01 to -0.02
IC4pin4 -0.02 to -0.20
IC4pin14 -12
IC4pin5 -10.47
IC4pin6 6.33 to 6.35
IC4pin12 6.35 to 6.37
IC6pin13 4.75 to 4.90
IC6pin12 5.35 to 5.37
IC6pin14 -0.04 to 0.23

Test#6 has you checking for a complex tone which results from using one audio signal to modulate
another audio signal. The difference you notice in the “mix” of the signals can be the result of
something awry in Test#4, but it also is affected by the Carrier Trim setting which is set in the
Calibration section on page 22 of the manual (advanced about two-thirds of the way on the unit here).
DC voltage testing can be made for this trim, R34, in the previously described Modulation Trim tests.

-0-0-0-

Attachment:
PT ts response.pdf [232.57 KiB]
Downloaded 339 times

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Scott Lee
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Mon Feb 29, 2016 5:37 pm
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Posts: 10
Post Re: 9710 VCA/Mixer - Test #4 & #6
Thanks Scott,

We followed the steps "Specific to the trouble" and the results were as expected.

These were the values with R24 & R34 defaults (roughly half way):

IC6pin9 0.7mV
IC6pin10 0V
IC6pin8 4.98V

Because R24 was referenced earlier, we weren't quite sure whether the mention of R34 was a typo, so we did the readings with R34 at 4.4V and R24 at default (0.03V), with R34 at default (1.82V) and R24 at 4.4V, and with both R34 and R24 at 4.4V.


R34 at 4.4V and R24 at default (0.03V) results:

IC4pin10 5.08v
IC4pin8 5.08v
IC4pin2 -0.724
IC4pin3 -0.729 to -1.038
IC4pin1 -0.009
IC4pin4 -0.013 to -0.202
IC4pin14 -12
IC4pin5 -10.57
IC4pin6 5.99
IC4pin12 5.99

IC6pin13 5.25
IC6pin12 5.22
IC6pin14 0.01


R34 at default (1.82V) and R24 at 4.4V results:

IC4pin10 5.08v
IC4pin8 5.08v
IC4pin2 -0.713
IC4pin3 -0.722 to -0.723
IC4pin1 -0.5
IC4pin4 -0.01
IC4pin14 -12
IC4pin5 -10.57
IC4pin6 5.99
IC4pin12 5.99

IC6pin13 5.24 to 5.25
IC6pin12 5.22
IC6pin14 0.02


Both R34 and R24 at 4.4V results:

IC4pin10 5.08v
IC4pin8 5.08v
IC4pin2 -0.71
IC4pin3 -0.72 to -0.93
IC4pin1 0
IC4pin4 -0.02 to -0.3
IC4pin14 -12.08
IC4pin5 -10.57
IC4pin6 5.99
IC4pin12 5.99

IC6pin13 5.24 to 5.25
IC6pin12 5.22
IC6pin14 0.03


Of note, where you had ranges and we have a single value, our values did not fluctuate.

Do these readings give you any indicators as to what any possible problems are?

Many thanks,
Nic & Tenchi


Sat Mar 19, 2016 8:10 pm
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Post Re: 9710 VCA/Mixer - Test #4 & #6
Quote:
Because R24 was referenced earlier, we weren't quite sure whether the mention of R34 was a typo, so we did the readings with R34 at 4.4V and R24 at default (0.03V), with R34 at default (1.82V) and R24 at 4.4V, and with both R34 and R24 at 4.4V.


Each trim works to vary voltage and this voltage is on their front, wiper terminal (and the resistors that follow in the schematic, R34 wiper to R31 and R24 wiper to R27). Your tests show these do adjust to about the middle of the negative to positive supply voltages. Testing at the connecting resistors will confirm the trim, and the solders for it and connected resistor.

Quote:
Of note, where you had ranges and we have a single value, our values did not fluctuate.


The ranges will be due to the modulator cycling and this control signal affecting IC4. The modulating CV is from IC7A(pin1) and enters via resistors R66 10K and R63 91K with transistors Q3/Q4 conducting the change. The IC7pin1 modulator output also goes to the panel connector J6 through wire L to the Ring terminal which works as a contact for shunting away the modulator output when a TipSleeve, mono, plug is inserted, shorting the J6 socket's ring and sleeve via the plug sleeve.

The TRS, 'stereo', at the J3 Carrier input is supposed to perform a similar action for inputs to VCA A (either the 'normal' L+R section as input, or a plug inserted external source).

A trouble which can occur with both types of connectors in the kit, TS and TRS (the ts are also closed circuit with a shunt contact resting against the tip contact when a plug is not inserted): Heat from soldering the terminals can travel up into the part and deform the plastic body. If you see a bulge or 'out of square' look on the connectors, it can result in a contact between the socket and a plug (or a 'normaled' connection, ie J1, J4, or the shunt action with a TS in the TRS J3 and J6) not making as it should.

Confirm TRS are at the J3 and J6 VCA A Carrier and Modulation input connectors (the c.c. TS connectors have a spring, seen looking into the back of the part, the TRS just have two contacts for the Tip and Ring).

If this is all good, it would be useful knowing if the calibration steps on page 22 work as expected.

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Scott Lee
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Tue Mar 22, 2016 1:56 pm
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Posts: 10
Post Re: 9710 VCA/Mixer - Test #4 & #6
Thanks Scott,

What became apparent from reading your last post was it seemed that plugs were inserted in J3 and J6; this was something we did not do for the previous results. We put 3hrs in each Sunday and basically start fresh each time, unless we believe we have unfinished business.

This time we have TRS patch between VCO to VCA on J3 and J6.

R34 at 4.4V and R24 at default (0.01V) results:

IC4pin10 5.08v
IC4pin8 5.08v
IC4pin2 -0.73
IC4pin3 -0.72 to -0.96
IC4pin1 -0.01
IC4pin4 -0.02 to -0.19
IC4pin14 -12.08
IC4pin5 -10.56 to -10.57
IC4pin6 5.99 to 6.0
IC4pin12 5.99 to 6.0

IC6pin13 5.25
IC6pin12 5.22 to 5,23
IC6pin14 0.01 to 0.02

The results differs slightly with modulation in some areas where it was missing. The main thing to notify you of was we did not have plugs in J3 and J6 with the previous results.

> Testing at the connecting resistors will confirm the trim, and the solders for it and connected resistor.

This was as expected.

> Heat from soldering the terminals can travel up into the part and deform the plastic body.

There was no deformation due to heat.

We will start calibration next time.

Many thanks,
Nic & Tenchi


Sat Mar 26, 2016 8:31 pm
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Joined: Sat Mar 07, 2015 6:23 pm
Posts: 10
Post Re: 9710 VCA/Mixer - Test #4 & #6
Hi Scott,

> Confirm TRS are at the J3 and J6 VCA A Carrier and Modulation input connectors

We confirmed they were TRS and no visible damage.

> If this is all good, it would be useful knowing if the calibration steps on page 22 work as expected.

We ran the calibration as suggested.

Modulation Null:
With the Gate off there was loud feed through. On adjusting R24 there was no change.

Carrier Null:
This gave the expected results.

We are hoping the results from the Modulation Null calibration and the results from tests #4 and #6 give you more information, for helping us debug this problem.

Thanks,
Nic and Tenchi.


Sat Apr 09, 2016 6:35 pm
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Post Re: 9710 VCA/Mixer - Test #4 & #6
Thanks for this update -- The trouble might be due to using 'stereo' TipRingSleeve (TRS) plug terminated cables in the VCA A Carrier In, J3, and Modulation In, J6, TRS sockets.

These VCA A inputs should be connected using 'mono' TipSleeve (TS) plug terminated cables.

When the TS plug is inserted to the TRS socket, the ring contact is shunted to ground via the sleeve of the plug.

On the Carrier In, J3, this eliminates the VCA L+R signal and substitutes an external signal source as the input to VCA A.

On the Modulation In, J6, the ADSR modulator is elminated and the external control is substituted as the modulation control signal.

...making a note to include this information in future revisions of the manual.

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Scott Lee
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Mon Apr 11, 2016 9:32 am
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Post Re: 9710 VCA/Mixer - Test #4 & #6
Hi Scott,

Thanks for the feedback.

> The trouble might be due to using 'stereo' TipRingSleeve (TRS) plug terminated cables in the VCA A Carrier In, J3, and Modulation In, J6, TRS sockets.

We retested #4 with 'Mono' TS plug terminated cables. We got exactly the same behaviour - the tone was not modified/minimized by adjusting the R24.

Thanks for any comments you can provide.
Regards,
Nic & Tenchi


Sat May 14, 2016 8:08 pm
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Post Re: 9710 VCA/Mixer - Test #4 & #6
Hello Nic, Tenchi.

Apologies for the delayed response. I wanted to set-up and get some more measurements specific to the R24 and IC4.

The variable voltage from R24 goes to pin 1 of the 1496 IC4 for minimizing the L+R signal (when no plug is in VCA A input), or, a signal applied to the VCA input.

Before the R24 voltage gets to IC4 pin 1, it passes through 470K yel-vio-yel R27. R27 and 1000ohm brn-blk-red R25 scale down the voltage and set a current flow into pin 1. The voltage here should be in a range of about -20 to -80 mV, regardless of the setting of R24.

Compare the measurements at the R25/R27 ends which run to IC4 pin 1, and, the pin 1 (on the top side of the board) of IC4. Them being the same will confirm the connection.

If not, confirm the resistors are the ones specified according to their color code and inspect their and pin 1's soldering. Do you see the nib of the pin extending through its joint -- if not, maybe it bent under the part as it was installed and not noticed during soldering. Nudge R25 and R27 to see if either may have cracked open, in which case the two halves would separate.

A replacement for the 1496 at IC 4 would be the next step. If you'll email me the address, I will send one in the mail.

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Scott Lee
scott@paia.com


Wed Jun 01, 2016 4:00 pm
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Joined: Sat Mar 07, 2015 6:23 pm
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Post Re: 9710 VCA/Mixer - Test #4 & #6
Hi Scott,

We measured the voltage at Pin1 on IC4 and it is -2.3mV to -2.4mV, not the -20 to -80 mV listed.

The values were consistent at the Pin1 R25/R27 adjacent via the trace.

R25/R27 were verified as having the right values.

The pins on IC4 and the R25/R27 were checked and re-soldered.

R25/R27 were nudged to verify unbroken.

Does this clarify the situation at all?

Regards,
Nic & Tenchi


Sat Jun 11, 2016 7:10 pm
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