Repair Pioneer A9 NSA

[Carguy1394]

It should be easy enough to test a thermistor, in isolation measure the room temp resistance then heat up or cool off while monitoring the change in resistance

TH 1.2 is listed as TH103-2. 470K S09 IN is written on the thermistor itself, 470K SE is written on the other. If you have data, how many ohms should be at 20C, 50C, 80C. post them. This will be useful to understand if they are working properly and if they are drifting. An analogue may be found. I don't know what exactly they are for in this scheme. Markthefixer should say, but he already explained that pioneer does not give info about their role in the scheme:
"TH1 and TH2's presence form an unknown influence on the R43,R59 || TH1, R57, R45 driver base voltage divider string. Pioneer doesn't bother listing ANYTHING about it."

 

[Carguy1394]

Yes.

also, after beating myself up the last time, I just realized that with the boards disconnected, not only grounds and power were disconnected, but also the STV-4H diode was no longer in the NSA circuit, connecting Q17e and Q21e.... another "I'm sorry" for not realizing that.

I agree, use the driver boards with the 2sa985a and 2sc2275a drivers disconnected (fully removed from circuit) and the midpoints of R1 / R2 unhooked -
feedback will be on big board using split R61 center connected to R71 (and R62 split center connected to R72 on the other channel).

That board's connections will power up Q29 & Q31, provide a few grounds, and restore the STV-4H thermal diode circuit.

BTW, I'm not trying to quibble:
Thermistors are a different part than the thermal diode.
the thermal diode is STV-4H, which is several semiconductor junctions passing current
while
the thermistor TH1 is connected across R59 (2.2k) and on the other channel TH2 is connected across R60(2.2k). That TH1 is a resistor that shifts value depending upon it's temperature.

TH1 and TH2's presence form an unknown influence on the R43,R59 || TH1, R57, R45 driver base voltage divider string. Pioneer doesn't bother listing ANYTHING about it.

Now, with R43 replaced, and the stv-4h diode back in circuit, I'm hoping the numbers on that sheet come back perfect...

With the boards in place, I believe all the ground connections are connected. If you have doubts or questions, wait for me to get my addled brain online again and things reconsidered and straightened out.

I did everything exactly according to #143. For this I used two other of my driver boards with the driver transistors removed. I switched on step by step and started the measurements. All the voltages I tried to measure pulsated. That is, they pulsated-changed their value in tenths and hundredths of volts and did not stay with a constant digital value.


This led me back to the alternate option listed in #99, that is, the first option described by markthefixer in #43. I immediately measured the driver voltages for a quick preview. The sum of them was 0.V

I decided to wait for the amplifier to warm up for half an hour. After half an hour I touched the radiators of the drivers with my hand. all were of the same temperature close to human body temperature ie 36.6C-37C. I immediately touched the transistors Q9-Q16. They were warmer, but not hot - somewhere around 45C maximum to 50C. I've started the measurements I'm posting here. In the middle of the measurements, I touched the radiators of the drivers again - they were very hot, I shut down the amp and checked and measured all grounds. There was no problem. I turned it back on after the drivers had cooled and picked up where I left off by redoing two transistors back. Their voltages were different from the ones measured a while ago when the amplifier warmed up. Then I decided to measure very quickly and without recording because while I'm slow to record the voltages can change. And that's exactly how it turned out! And so- B with B, E with E,C with C of the symmetrical transistors Q9 with Q10, Q11 with Q12...etc. And also on the complimentary predrivers Q30 with Q32 and Q29 with Q31. The sum of these voltages is also equal to 0,...

I have demonstrated this with transistors Q29 and Q31. There I have measured Q31 E=1.99V. As I measure and record Q29 B and Q29 C , already during this elapsed time of about a minute and more the voltage has changed and is Q29 E =+1.66V and summed with the complementary Q31 E= -1.99V their sum is no longer 0.000 and is -0.33V. For this I have recorded in the red brackets the voltage that was measured on a cooled amplifier immediately for an interval of 1 second, I have memorized it because it is easy and I have written it down.

Here I will shorten the descriptions of the causes and will only say the results empirically. What makes the voltages change and what makes the drivers and transistors heat up?

They heat up due to the disturbances introduced by the probes during the measurements, which causes them to heat up as well. How- I don't know how-I don't have an oscilloscope or a spectrograph. I am using Fluke 115.


Probably the probes initiate some positive feed back connection which raising the temperature and dinamicly change the voltages on the transistors during the amplifier is trying to balance itself


Also, the board reacts on the laser thermometer and turned the protection ON.

Heated to hot board and drivers after the amplifier turned off and immediately turned on from hot position it cooling down to human body temperature in about 5 minutes.

If it is left from the heated position to cool again for the same time, it cools to 36C.

Also when I measure the voltages only on the drivers boards the amplifier don’t react with a heating.


Here my question is: Is this the "zeroing" mentioned by markthefixer , and what will be the next step from here?

 

[Carguy1394]

Yes . Got it. Again there was a problem with the connectors on the driver boards. Apparently, this is the weak point of this amplifier. Some kind of solution should be invented here. .Even to be completely eliminated and use solder for the grounds and the thermodiode and unregulated voltages. Even if we achieve something good, on the end we have to connect these connectors. And then comes the risk that everything done will fail. At the moment I don't know what to do to solve the problem. Maybe replacing the 8 wire ribbon cable with a longer one or just longer individual wires that can be twisted?

 

[markthefixer]

I see it. I am thinking on it. I don't think a couple of extra inches will hurt things. Those aren't the WORST parallel cables I have seen Pioneer use.

 

[Carguy1394]

I see it. I am thinking on it. I don't think a couple of extra inches will hurt things. Those aren't the WORST parallel cables I have seen Pioneer use.

Yes there is always worse. I shouldn't blame Pioneer Engineers for something that has worked for 40 years .It's just that these connectors are not intended to be removed and inserted constantly. However, it is not clear to me why the tracks on the left GWX-595 connector are inclined and thinned, and not like the right GWX-596. The left channel is more often defective. The parallel cable in its normal position is twisted and bent. This keeps it taut and the holes on the board with their sharp edges break it easily if it is connected/disconnected frequently. And small wires break from the bottom of the connector and touch the cable next to it and make a problem.
This can be seen in the enlarged photo. The wright red/white cable has already 2 broken wires.
I replaced Q29 and Q31 again just in case. Even if they are good, they reduce their hFE when they see 60 volts. I replaced the parallel cable with a separate wires that do not create any tension when bending and twisting, and I might as well glue them with silicone so that they bend more smoothly. I also bypassed the broken tracks.
I turned on the power, the protection turned off after 10 seconds and I waited half an hour. The drivers were around body temperature. I started measuring from Q32 to Q7.
I post the results here. They were measured according to No. 99, where the thermal diodes and all connections, groundings and unregulated voltages -/+60V are present connected with a fresh replaced wires.
When I measure Q14 C/Q13 C the voltage is about 1.7 V. But if I have previously measured voltages across Q9-Q12 , the voltages of Q13 C/ Q14 C immediately rise to about 5 V - which I have marked in the measurements with " ** " .
I have marked this with " * " the measurements on the bases on Q9 to Q12 each made by turn of and on the amp .
I think from the probes these transistors amplifying some signal and creating positive feedback connection, as I already described in #147. Maybe that's why in the service manual they don't measure the voltages of the bases of Q9 do Q12?
I don't know if that's right. I'm stopping here and will wait for direction on what to do next.

 

[markthefixer]

At first glance, things are definitely looking a lot better.

Tomorrow I shall carefully re-read it. This was my last "quick stop in" before retiring for the evening, whatever of it that is left.

 

[Carguy1394]

At first glance, things are definitely looking a lot better.

Tomorrow I shall carefully re-read it. This was my last "quick stop in" before retiring for the evening, whatever of it that is left.

Regarding the described possible positive feedback described in #148 and #150 and the stars in posting #150 .
Is this positive feedback, is it self-generated or is triggering in the process of measurements by touching the transistors with a probes and how is it obtained? Yes it changes the voltage of Q13C/Q14 C from 1.7V to 5.3V/5.5V

I decided to connect a second Fluke (#2) to Q13 C (left channel) and ground, permanently connected. With the other Fluke #1 I started measuring the voltages on Q10. (right channel).
With the amplifier running on a 110V supply, the Fluke 2 showed 1.75V at the Q13 C.

1. When I touched the Q10 B with the probe of Fluke 1 it showed +10.9V and Fluke 2 continued to show +1.75V on the Q13 C.
2. When I touched the Q10 C with the probe of Fluke 1 it showed +11.8 Volts and Fluke 2 immediately showed +5.5 Volts on Q13 C !!!
3. I turned the amplifier off and on again - Fluk2 on Q13 C again showed +1.75 Volts.
I touched the Ku10 E with the probe of Fluke 1 and it showed 11.8 Volts and Fluke 2 immediately showed again +5.5 Volts on Q13 C !!
In summary - by measuring the collectors and emitters of transistors Q9,Q10 Q11,Q12, the voltage of transistors Q13 C /Q14 C rises from 1.7 volts to 5.5V/5.3V.

I want to ask the following question:
Is it ok to connect a resistor of around 30ohm or 50ohm or some other value between pin 5 for GWX-593 and ground , ( and for the GWX-594-pin10 and ground ) , to create a load that will eventually eliminate the posible positive feed back connection that changes the voltages and ensure more accurate measurements ?

 

[markthefixer]

This is a problem caused by the extra feedback taps I directed to be used.

The voltage readings in this one look normal enough to begin rolling back to the original unsplit resistances.

Pins 5 & 10 go back to the components C25 & C26, which are part of an amplifier's "zobel" filters.
one set of filters is L1 1.1 microhenry & R87 10 ohms 2 watts in series through the output
The other set (Boucherot cell) is R71 (8.2 ohms 2 watts) & C25 (0.033 uF) (& R72, C26).

I'm NOT saying to do anything yet!!! We just have to start thinking about it, evaluate where we are with ALL the boards.

are the grounds at 3-1 and 4-2 connected to the appropriate gwx board?
if not, the Boucherot cell is floating.

A Boucherot cell (or Zobel network) is an electronic filter, used in audio amplifiers to damp high-frequency oscillations that might occur in the absence of loads at high frequencies. Named after Paul Boucherot a Boucherot cell typically consists of a resistor and capacitor in series, usually placed across a load for stability.[1]

It is commonly seen in analog power amplifiers at the output of the driver stage, just before the output inductor. The speaker coil inductance of a loudspeaker generates a rising impedance, which is worsened by the output inductor generally found in analog power amplifiers; the cell is used to limit this impedance.[2]

The documentation for some power operation amplifiers suggests the use of a "Boucherot cell between outputs and ground or across the load".[3]

Additionally, Boucherot cells are sometimes used across the bass driver (and mid-range) of a speaker system, in order to maintain a more constant driving point impedance as "seen" by a passive crossover. In this specific arrangement, the Boucherot cell is sometimes also known as a Zobel network.[2]

Some loudspeaker crossover designs aim to stabilize impedance at high frequencies by including Zobel networks.[4]

 

[Carguy1394]

This is a problem caused by the extra feedback taps I directed to be used.

The voltage readings in this one look normal enough to begin rolling back to the original unsplit resistances.

Pins 5 & 10 go back to the components C25 & C26, which are part of an amplifier's "zobel" filters.
one set of filters is L1 1.1 microhenry & R87 10 ohms 2 watts in series through the output
The other set (Boucherot cell) is R71 (8.2 ohms 2 watts) & C25 (0.033 uF) (& R72, C26).

I'm NOT saying to do anything yet!!! We just have to start thinking about it, evaluate where we are with ALL the boards.

are the grounds at 3-1 and 4-2 connected to the appropriate gwx board?
if not, the Boucherot cell is floating.

Yes-CN3-1 / CN4-2 grounds and all the other grounds are measured from the soldering points on the GWH-146 to the
chassis and they are 0.3 Ohms (shorted probes are 0.2 Ohms)

I was just thinking of trying with plugged in headphones and a magnet on the reed relay Rl-3 if that feedback would be damped, because the circuit goes through the headphones 32 ohms and the resistors in the connector R301/R302 330 ohms /3W . And indeed from pin 5 / 10 of the GWX -593/594 to ground the measured resistance is 353 Ohms .

But I'll listen this time and will not doing this experiment.

Also, know I understand that the Boucherot cell which is acting as a cut-off filter is supposed to damping any high frequency feedback. So may be when is connected everything into the case will be working properly.

So if we will not do more tests or adjustments/repairing with this board, I mean also the measurements with varying VR 1,2,3,4 , I can disconnect this board and put aside and connect the following. Two more left to do before disassemble the test rig. This was in the worst condition.

 

[markthefixer]

i think that without drivers (and of course outputs) 32 + 330 ohms is too much of a load.

I could see trying about 1000 ohms (1 k) as a load.

I feel that a bit more exploration of the voltages to the driver bases, from the NSA cells (and their control circuits: VR3 100k) and from the STV diode and variable resistor VR1 (100) in an apparently working unit will serve us well when the remaining boards have their turn in the test rig.

I would measure (measurement block):
Q13 collector (red) to gnd (black),
Q17 collector (red) to Q17 emitter (black), /////////////// this is the positive side NSA cell :Q17 & Q19
*** start of special readings when Q25 emitter set to 1v and thus 1 mA: ****************************************************
Q25 collector (red) to output R71 (black) //// the control voltage being sent to the positive side NSA cell
Q27 collector (red) to output R71 (black) //// the control voltage being sent to the negative side NSA cell
*** end of special readings when Q25 emitter set to 1v and thus 1 mA: *****************************************************
Q17 emitter (red) to Q21 emitter (black) //////////////// (this is the stv diode & resistor),
Q21 emitter (red) to Q21 collector (black),, /////////////// this is the negative side NSA cell : Q21 & Q23
Q15 collector (red) to gnd(black).

First with vr1 & vr3 at 0 ohms do the measurement block
then vr1=0, vr3 to max, redo the measurements and include the *** special measurements ******************************************
then vr3 adjusted for 1 ma (Q25 emitter (black) to +60v regulated rail (red), 1 volt across R47 1k ohms and
redo the measurements including the *** special measurements.
Leave VR3 at one volt setting
now time to adjust VR1 and see what changes as vr1 is increased. 20 ohms, 40 ohms, 60 ohms, 80 ohms and 100 ohms.


just for informational sake, we are close to the idle current adjusting procedure with these tests, of course we are missing drivers and outputs.
**** this is the idle current adjusting procedure from the manual ************************************************
from full CCW (0 ohms) on both VR1 & VR3
adjust VR1 for 50 mA idle current read as 50 mV across 2 output transistor emitter resistors
then adjust VR3 to raise the idle current to 75 mA (75 mV)
****** this is the end of the idle current adjusting procedure from the manual ***********************************

VR1 overcomes the variations in the two Vbes of the NPN and PNP output transistors. (the +0.6xx V and -0.6xx V base drives) and gets current flowing
VR3 then trims up the NSA cells.


whew........
but it will be worth it, knowing exactly how it should be working.

 

[Carguy1394]

i think that without drivers (and of course outputs) 32 + 330 ohms is too much of a load.

I could see trying about 1000 ohms (1 k) as a load.

I feel that a bit more exploration of the voltages to the driver bases, from the NSA cells (and their control circuits: VR3 100k) and from the STV diode and variable resistor VR1 (100) in an apparently working unit will serve us well when the remaining boards have their turn in the test rig.

I would measure (measurement block):
Q13 collector (red) to gnd (black),
Q17 collector (red) to Q17 emitter (black), /////////////// this is the positive side NSA cell :Q17 & Q19
*** start of special readings when Q25 emitter set to 1v and thus 1 mA: ****************************************************
Q25 collector (red) to output R71 (black) //// the control voltage being sent to the positive side NSA cell
Q27 collector (red) to output R71 (black) //// the control voltage being sent to the negative side NSA cell
*** end of special readings when Q25 emitter set to 1v and thus 1 mA: *****************************************************
Q17 emitter (red) to Q21 emitter (black) //////////////// (this is the stv diode & resistor),
Q21 emitter (red) to Q21 collector (black),, /////////////// this is the negative side NSA cell : Q21 & Q23
Q15 collector (red) to gnd(black).

First with vr1 & vr3 at 0 ohms do the measurement block
then vr1=0, vr3 to max, redo the measurements and include the *** special measurements ******************************************
then vr3 adjusted for 1 ma (Q25 emitter (black) to +60v regulated rail (red), 1 volt across R47 1k ohms and
redo the measurements including the *** special measurements.
Leave VR3 at one volt setting
now time to adjust VR1 and see what changes as vr1 is increased. 20 ohms, 40 ohms, 60 ohms, 80 ohms and 100 ohms.


just for informational sake, we are close to the idle current adjusting procedure with these tests, of course we are missing drivers and outputs.
**** this is the idle current adjusting procedure from the manual ************************************************
from full CCW (0 ohms) on both VR1 & VR3
adjust VR1 for 50 mA idle current read as 50 mV across 2 output transistor emitter resistors
then adjust VR3 to raise the idle current to 75 mA (75 mV)
****** this is the end of the idle current adjusting procedure from the manual ***********************************

VR1 overcomes the variations in the two Vbes of the NPN and PNP output transistors. (the +0.6xx V and -0.6xx V base drives) and gets current flowing
VR3 then trims up the NSA cells.


whew........
but it will be worth it, knowing exactly how it should be working.

"i think that without drivers (and of course outputs) 32 + 330 ohms is too much of a load."

But there is a drivers installed. No PT , but the drivers are there and the middle point of R1/R2 2X75 Ohms are connected to pin 5 / pin10 on the driver boards GWX-593/GWX-594. I wrote this in #147 :
"This led me back to the alternate option listed in #99, that is, the first option described by markthefixer in #43. I immediately measured the driver voltages for a quick preview. The sum of them was 0.V... " - And in #43 we are using the drivers.

I accept this as my fault for not explaining well enough exactly what I'm doing by referencing a paragraph within another paragraph. I'm sorry I wasn't more specific in the descriptions. I'll keep that in mind in the next ones.

Well, anyway what to do from here on.
It's no problem to unsolder the drivers and go to option #99 where from the middle point R61/R62 we connected to R71/R72. And to make the measurements you write about above.

Or if somehow these measurements can be adjusted , or made to the current situation with the drivers installed and a midpoint from R1/R2 to pin 5/10 on the GWX-593/594 driver boards respectively?

 

[markthefixer]

No changes in the circuit. Procedure should be ok with them live.

3v max stays, the 150 ohm emitter resistor will get hot, but nothing burns. More voltage WILL burn the 75 ohm + 75 ohm resistors, while on the previous stage is R61 at 680 ohms and it will take a lot more base to emitter voltage to burn them.

So if emitter to base voltage at the drivers q29 & q31 approach or appear to be ready to exceed 3 volts, go no further.

 

[Carguy1394]

No changes in the circuit. Procedure should be ok with them live.

3v max stays, the 150 ohm emitter resistor will get hot, but nothing burns. More voltage WILL burn the 75 ohm + 75 ohm resistors, while on the previous stage is R61 at 680 ohms and it will take a lot more base to emitter voltage to burn them.

So if emitter to base voltage at the drivers q29 & q31 approach or appear to be ready to exceed 3 volts, go no further.

I'm still re-reading the last few posts multiple times to understand them better. But let me do #157 first. And here to ask first if I understood correctly
„No changes in the circuit. Procedure should be ok with them live.”

Does this mean that the two GWX-593/594 driver boards with installed drivers remain connected to the GVX-146. Also a 30 ohm headphones is plugged into the amp in the headphone jack and the reed relay is magnet activated to close the circuit and the headphones together with R301R302 330 ohms will be the load.

 

[markthefixer]

i would prefer not doing the magnet trick, no headphones connected or driven.

should have been more assertive on that.

procedure meant measurements, and whatever pot twisting called for.

i'm dead on my feet, thus the brevity. g'nite...

 

[Carguy1394]

i would prefer not doing the magnet trick, no headphones connected or driven.

should have been more assertive on that.

procedure meant measurements, and whatever pot twisting called for.

i'm dead on my feet, thus the brevity. g'nite...

"i'm dead on my feet, thus the brevity. g'nite..."

Especially at our age, we have to put our health above everything, and a key moment for this is falling asleep before 12 o'clock. I burned the board several times from mistakes made by working at night.

Ok, we will not deal with the headphones and the magnet of the relay..I also have suspicious that this will involve the EQ board.

Then what should be the connection- In the above posts, different connection options were considered, but they confused me and it is not clear for me which method to use last. (#43 or #99 +GWX593/594 , but wit no drivers )

The idea was to have a load resistor somewhere to damp the oscillations before the Boucherot cell. ( Or may be without this resistor)

Which option exactly?"

1. Use the driver boards together with the drivers and connect a resistance from the middle point of 2x75 ohms on R1/R2 to ground. Аnd how many ohms should this resistance be - as if I'm not mistaken it was indicated in "Tuning fork #8" - I'm not very sure.
Оr
2. according to #99 - the middle points of R61/R62 (2x380 ohms) are connected to the ends of R71/R72 .And we connect the driver boards but without the driver transistors to GWH-146. And from midpoint of R61/R62 to connect 1000 Ohms to ground for load?

In short, I need a simple instruction like - connect this to that to start to variate the VR1,2,3,4.

 

[markthefixer]

GWX-593 the driver 2sa985a is connected,
GWX-594 the driver 2sc2275a is connected,
and the middle point of
R1 2X75 Ohms is connected to pin 5 on the GWX-593 board and
R2 2X75 Ohms is connected to pin 10 on the GWX-594 board

R61/62 can be what it was originally, a single 680 ohm resistor. NO added connection to R71 or R72.

This is exactly Tuning Fork #8, and they discuss the output
"output power becomes 1W or less when the emitter resistors on the driver stage are more than 200 ohms. We are 150 ohms.

1 watt = v squared / 30 , v = 5.4v and then figuring in the R301 / R302 headphone resistors at 330 ohms (3W) decreases the load considerably.
in that respect it appears that I was overly cautious.

with the pins 5 and 10 connected, and your statement: "Yes-CN3-1 / CN4-2 grounds and all the other grounds are measured from the soldering points on the GWH-146 to the chassis and they are 0.3 Ohms (shorted probes are 0.2 Ohms)" the Boucherot cells are connected.

So if you want to use magnets to energize the headphone jack, I no longer have objections.

In summary - by measuring the collectors and emitters of transistors Q9,Q10 Q11,Q12, the voltage of transistors Q13 C /Q14 C rises from 1.7 volts to 5.5V/5.3V.

Try varying the VR3/4 from 0 to 100k and see if there is a point after which this voltage rise does not happen. If you had a scope, it would be interesting to check if the circuit is oscillating. However, if the Boucherot cells were connected back then, I would not expect to find oscillation.

when the Q13 C /Q14 C rises from 1.7 volts to 5.5V/5.3V please check
the voltages (referenced to ground) of the GWX-593 pin 5 and GWX-594 pin 10 output terminals.
does the Q15 C (to gnd) voltage stay the same?

 

[Carguy1394]

Unfortunately, I don't have an oscilloscope. I dream of finding an analog oscilloscope on offer at a low price, but for now I don't have any. Ok let's see what happens with the measurements
I will follow this instruction and post the results.

 

[Carguy1394]

had to wait for the delivery of the VR100K multi turn I had only replaced the VR100 ohm with the multi turn but since I started measuring with two fluke multi meters I noticed that the voltages varied by half a volt thanks to the VR100K. 60 volts pass through them and apparently the graphite layer breaks down over time. So know all the VR-s are replaced.I couldn't find out how many watts they are.

I also made a simple device to turn the screw on the multi turn VR resistors -
I put a plastic tube on the screwdriver with the diameter of the VR screw. Makes turning those little screws a lot easier

I made the measurements by clipping one fluke to Q13C/Q14C, and with the other fluke I measured Q15C/Q16C and the pins 5/10. VR I rotated them continuously and monitored the readings in parallel. Their graphs are parallel or overlapping. therefore I only give the final results
While measuring only the collectors of Q13/15/ .Q14/16 there was no spurious interference and no noise was heard in the headphones.

Noise occurs when I touch the transistors Q1, Q3, O9 with the probes. Q11 or Q2/Q10/Q12. Then noises are heard in the headphones Radio-type noises between stations, up to noise with a frequency of 10-15kHz. The interesting thing is that touching with the probe on the base of Q9 or Q10 these noises stop and the voltage is restored on Q13C by 5.5 volts to 1.8V

"when the Q13 C /Q14 C rises from 1.7 volts to 5.5V/5.3V please check
the voltages (referenced to ground) of the GWX-593 pin 5 and GWX-594 pin 10 output terminals.
does the Q15 C (to gnd) voltage stay the same?"
-The volts on Q15C drop from 1,719 V to 1,702V during this voltage appear.

So I rise the volts on Q13 C , by touching with e red probe Q1 in the point to R17. And after that with probe touch the Q10B and Q9B and the volts on Q13C goes to normal 1,7XX V Also in the knight the board is more stable ..

I don't know if this wasn't also on the previous board, if it matters and if it should be investigated at all. I can hook up the previous board and check that way if it does the same.
*****
These results are not completely accurate because they were done relatively quickly. Actually after about half an hour, these results change a little. for the right channel it is not significant, the change is in hundredths of a volt, but for the left channel, the difference in the graphs of the voltage of Q13C and Q15C reaches 0.2 V and is kept like this from minimum to maximum variation of VR1 or VR3.

Perhaps stability of the voltages cannot be ruched. without a temperature feedback with the thermal diodes.
Should I post measurements taken after 1 hour of starting the amp?

 

[Carguy1394]

Now I'm trying to figure out #155 to do the measurements but in places I'm not clear on exactly what to do. I will read it a few more times

 

[Carguy1394]

Regarding #155, which I have been dealing with for several days, I have the following questions:

1 . Instead of measuring the resistance of the VR to get several different points on the graph, can I divide the voltage from min to max that drops across the VR into 4 equal intervals and then take the measurements. This will save me an awful lot of time turning the amp off and on every time and shorting the big capacitors to measure ohms on the board…
But that's not all - after each switch on, it takes time for the board to warm up (minimum 15-20 minutes!) to get stable readings because the thermal drift from cold transistors to heated ones is measurable with the changes I make with VR. Аnd then if the board is not heated ,the error will be huge - the changes are 0.150 volts per quarter interval , and the thermal drift is close to 0.5 volts.

2. Is this the measurement block:

*** start of special readings when Q25 emitter set to 1v and thus 1 mA: ****************************************************
Q25 collector (red) to output R71 (black) //// the control voltage being sent to the positive side NSA cell
Q27 collector (red) to output R71 (black) //// the control voltage being sent to the negative side NSA cell
*** end of special readings when Q25 emitter set to 1v and thus 1 mA: *****************************************************

Or all this for witch must be taken the measurements by varying the VRs?

"Q13 collector (red) to gnd (black),
Q17 collector (red) to Q17 emitter (black), /////////////// this is the positive side NSA cell :Q17 & Q19
*** start of special readings when Q25 emitter set to 1v and thus 1 mA: ****************************************************
Q25 collector (red) to output R71 (black) //// the control voltage being sent to the positive side NSA cell
Q27 collector (red) to output R71 (black) //// the control voltage being sent to the negative side NSA cell
*** end of special readings when Q25 emitter set to 1v and thus 1 mA: *****************************************************
Q17 emitter (red) to Q21 emitter (black) //////////////// (this is the stv diode & resistor),
Q21 emitter (red) to Q21 collector (black),, /////////////// this is the negative side NSA cell : Q21 & Q23
Q15 collector (red) to gnd (black)."