Technics SU-V9 adjusment procedure questions

Synchro-bias

New ClassA
:eek: Finally what seems like a lifetime ( a bit dramatic but has been a few months) the V9 is complete, and due for a once over again to make sure there is no shorts. All new fresh capacitors -long life high temp FR PWs SU bipolars plus film output for phono.

Thyristors have continuity with heatsink yet when they were out on the heatsink there was no continuty

When the service manual states to turn before adjustment - VR301 VR302 and VR601 to be turned counter clockwise direction - ? this mean completely?

Step1 - done this before wire to ground and TP703 while doing adjustments for VR701/2

turn off V9
then
Step2
Connect 8 ohm load to speaker terminal ? does that mean 8ohm resistor or speaker, i have an 8ohm cheap pair of speakers - woofer has no capacitors yet is 8 ohm

Connect DMM to Q327 and TP502 - that does go to ground so negative on Q327 and positive on TP502?


turn off V9
then
Step3
with the ICQ mention wherev to put the probes so is fine

Sankens look a bit bent? not sure i might redo them?
sanken okay pins.jpg
v9complete2.jpg

V9 adjustment.jpg
 
The manual seems clear. It referes to q327 "Collector" at step 2. I'll check the schematic tomorrow, but I think you need to check +V and -V against ground.

It doesn't matter if you connect the+ or - probes to the test points, since you are measuring voltages, just the sign will change. That's not relevant in steps 2 and 3. Just the voltage value.

Manual asks for a dummy load (a resistor, not a speaker)

icq test points must be found in the schematic, labeled A B C D , probably the emitter resistors.
 
As said, use resistors. Speaker are not always what they say.
I made up some resistors to load at 6.3 ohm and 6.7 load so as to check that the relay changed over when it should.
 
Thanks Elnaldo and Tony. I will look for some resistors - maybe a 5.6 and 2.2 ohm 1% tolerance 7.8ohm would be around 8ohm

collector and TP501 with the DDM and adjusting VR601 with the resistors in series making at ohm in each speaker terminal left and right channel? as with impedance setting
 
Thanks Elnaldo and Tony. I will look for some resistors - maybe a 5.6 and 2.2 ohm 1% tolerance 7.8ohm would be around 8ohm

collector and TP501 with the DDM and adjusting VR601 with the resistors in series making at ohm in each speaker terminal left and right channel? as with impedance setting

Accuracy is not needed. you could even use a 10 ohm load, since the manuals specs voltages for "6.6~16ohm", or parallel some resistors you have at hand to get approx 8 ohm.

I assume you already adjusted the impedance detector circuit in step 1. You need a 6.5 ohm load to do this adjustment, since the detector threshold seems to be 6.5 ohm. The 6.3 and 6.7 ohm trick is a good idea .

Step 2: TP502 is ground, (check page 23 of the PDF file from Hifi engine), so it seems you are measuring voltage between Q327 collector and TP502 (ground).

Step 3: I can't locate points A B c D in the schematic, I suspect they should be at the emitter resistors (the 0.22 ohm resistors). Please check if your PCB is labeled or if you have some pins to connect a DMM near those resistors.
 
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Hello Elnaldo
I havent started on the V9 yet, i have to do another check over for any solder traces etc.
I have the resistors for step1 to do the impedance since i have done this before i know what to there.

Step2 was confusing me.
To do the voltage adjustment approx 8ohm , i could use 4.7 and 3.3 to get 8ohm or single 8.2ohm resistor metal type? i wonder if they want carbon as for the Step1
I need to adjust VR601 for 8ohm load so TP501 ground - Q327C (rather a tight space) , with resister in speaker terminals ( as with step1) and turn to adjust to voltage

They say before adjustment to turn anticlock wise VR601 ( i assume completely turn it)

They are the big white resistor looking things
v9 icq adjust.jpg

I can see now that TP502 is along the ground
 
Any 8 ohm resistor will work to adjust step 2. If the collector where to measure is too hard to access, you can measure at any place electrically connected to it. Follow the pcb trace, I usually find some resistor to connect the dmm.
 
8ohm load step2.jpg
Any 8 ohm resistor will work to adjust step 2. If the collector where to measure is too hard to access, you can measure at any place electrically connected to it. Follow the pcb trace, I usually find some resistor to connect the dmm.
Thanks Elnaldo, - means like below to get 8 ohm load
 
Before powering up the V9
VR601, 301 and 302 turned completely counter clockwise. VR701/2 i think i have it a centre position
Main speaker on
Volume at 0
Straight DC
Resistors - from RS 5% carbon measure without leads, directly to mulimeter terminals 6.2/3ohm. I have another pair made up of 4.7 + 1.8 ohm - 6.5/6.6 ohm i could use
------
V9 powered up fire, no sound or bangs ! that is good

I tried adjusting the impedance but no luck cant get near 0.0v or -0.01? 200m setting gives -1 wiring issue or maybe wasnt in centre position? , but apart from that great to see the lights working
 
Fernando, Tony or Baily i had another attempt
Not sure what i am doing wrong, even tried the other resistors 6.5/6.5ohm vs 6.3 6.5ohm
Appears VR701 gets closer to VR702 adjustment of -0.13 and VR702 best is -0.24?

Could it be step2 needs to be done first?
Could it be step1 VR701/2 are not at centre, i assumed halfway was the lines on the pcb which appears to indicated a centre position

Maybe VR701 needs to be turned clockwise as in the above adjustment proceedure first then adjust VR702.

thanks
Sam
 
Step 1 needs to be done first, that sets the threshold to the impedance detector circuit, which will change the voltages you will check at step 2.

It says you need to connect TP703 to ground. I'd wait intructions from BTSs , who already did the adjustment, before shunting to ground a part of the circuit.

Seems you need both dummy loads connected, same at both channels. Manual calls for 6.5 or 6.6 ohm.

I'd adjust as explained in the manual manual, first VR701 full clockwise, then TP702 (VR702), and then TP701.
 
Thanks Fernando
The main board had a crack i fixed this and checked, maybe since assembly something unsoldered mabe? or maybe i turn VR701 fully clockwise before turning on the amp. I remember before when i did the adjustment with the V9, it was TP703 to chasis. Tony (BTS) used 4.7 + 1.5 - gave 6.3.6.5ohm. I can try both sets of resistors. Or maybe was not half way where I thought it was with VR702
 
update with V9
i pushed the adjustment dial beyond it limit and get the readings so maybe the adjustment dial is a bit faulty
-0.11 TP702 and -0.00 for TP701
 
update with V9
i pushed the adjustment dial beyond it limit and get the readings so maybe the adjustment dial is a bit faulty
-0.11 TP702 and -0.00 for TP701

Voltages are perfect!

If you don't trust a trimpot, replace it. If it doesn't make good contact, it needs to be replaced. Or, measure the actual resistance and replace it with fixed resistors, paralleling some to get the exact value.
 
Thanks Fernando
The voltages - soon as i got the desired number i removed the screw driver quickly, and there was as slight sound from the transformer. I think they must be in need for replacement. Would be measuring the resistance of the pins into the pcb board.

I measured from one point to other points as in the photo the resistance

trimpots.jpg
 
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If the voltage is OK now, without touching the trimpots, you should actually desolder them and measure the resistance of each half, and replace with resistors. Or, with this "in circuit" measurements, try to get the same resistance values at the same points with fixed resistors. Anyway you need to desolder the old trimpots. Or, buy new trimpots, perhaps it's easier to adjust.
 
Voltages are perfect!

If you don't trust a trimpot, replace it. If it doesn't make good contact, it needs to be replaced. Or, measure the actual resistance and replace it with fixed resistors, paralleling some to get the exact value.

Good advice... older trimpots can wreak havoc... you do not want bias pots acting up.

Impedance (tap select) is of less consequence- if you got voltages right, test amp with 2 pairs of spkrs, see if tap select switches to low tap when Spkrs A+B are selected, and goes back to high tap with only 1 pair connected (using 8 ohm spkr systems)
 
Hi Fernando
Yes, i had to hold the screwdriver for a little while to get the voltages but it could have moved, as it was very touchy. Neeed new or resistors as you said. I sure hope Bias and Power are fine.

Hi Baily
Yes, i think they are toast or near the end of their use

True the bias is very important

Only have one speaker terminal A only but i have not done step2 or 3 yet. I can hook up the test speakers and see if it clicks (taps)
 
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