Pioneer SX-980: in protect mode with over 40v for DC Offset (continued)

[JoeDotCom]

EDIT: IS THE DIM BULB TESTER STILL CONNECTED????
we may be getting into a chicken/egg situation, but if the bulb goes dim, it's safe to remove as long as idle current is zero'd, until we go BACK on the bulb to test the idle current operation. What wattage are you using? is the idle current turned down? Can you increase the bulb wattage?
IF SO, GO STRAIGHT INTO THE WALL AND RECHECK pins 22, 23, 25, 27 VOLTAGES, if good, don't lift the diodes.
END EDIT

OK, saw your edit. Zeroed the idle on DBT (not a full turn ether way, found 0v using idle adjustment procedure in manual. again, learning. )

Went off DBT, no explosion. Protective eyeware anyway.

22: 50.7
23: 23.5
25: -24.3
27: -61.2

Those numbers look pretty promising, yah?

 

[JoeDotCom]

22: 50.7
23: 23.5
25: -24.3
27: -61.2

Those numbers look pretty promising, yah?

SO what do you think MTF? I am cautiously hopeful that the issue is solved.

 

[markthefixer]

SO what do you think MTF? I am cautiously hopeful that the issue is solved.

is
27: -61.2 a typo? It should be -51v.

-62 is wrong.

read and post the voltages on the transistors you replaced.

do NOT expect an answer before Monday. I stole precious time to just do this.

be sure you put the diode and transistors in correctly.

 

[markthefixer]

SO what do you think MTF? I am cautiously hopeful that the issue is solved.

is
27: -61.2 a typo? It should be -51v.

-62 is wrong.

read and post the voltages on the transistors q3, q4 and diode d9 you replaced.

q4 2sb682 100v 4a 30w 55-300hfe 8mhz
512-KSA940TU pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
it is very hard to pt this one in wrong

q3 2sa850 100v 0.5a 0.8w 55-300hfe 130mhz *** appears to be bce ***
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 (R=60-120, O=100/200, Y=160/320)
thus if you installed exactly as old one, ignoring the ecb data I provided, it is reversed...

I don't know if we discussed or needed to discuss proper transistor orientation upon replacement.


do NOT expect an answer before Monday. I stole precious time to just do this.

you need to LOOK at the schematic (page 60 of 62), and at least find pins 22,23,25,27 on the awr-156 board and their voltages on the schematic.

 

[JoeDotCom]

27: -61.2 a typo? It should be -51v.

q3 2sa850 100v 0.5a 0.8w 55-300hfe 130mhz *** appears to be bce ***
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 (R=60-120, O=100/200, Y=160/320)
thus if you installed exactly as old one, ignoring the ecb data I provided, it is reversed...

I don't know if we discussed or needed to discuss proper transistor orientation upon replacement.

This is very embarrassing. I totally missed that it was ecb rather than bce. Actually, until now, i did not know I needed to look for that. If we did discuss it, it did not sink in and i am sorry for missing that. You are right, i simply installed the new q3 the same as the old one. so it was backwards. I have fixed the error now.

To MTF specifically along with everyone else who has chimed in on this and also those who are following this project (1,781 views in the month this thread has been active). I apologize for not catching that. i am VERY grateful for all the help i have received thus far and all the time that has been put in by others for my benefit. The least I could do is be sure to follow the instructions I am receiving accurately. Again, my bad on that. Fixing this unit is chore enough without needing to watch out for me making silly mistakes and not reading instructions completely.

I have flipped the transistor into its proper orientation and have the following readings to share:
22: 51.1 (previous: 50.7)
23: 23.6 (previous: 23.5)
25: -23.7 (previous: -24.3)
27: -51.6 (previous: -61.2) <-----


Wrong!!

Corrected

read and post the voltages on the transistors q3, q4 and diode d9 you replaced.

Next up, I will measure and post the readings for q3, q4, and d9.

you need to LOOK at the schematic (page 60 of 62), and at least find pins 22,23,25,27 on the awr-156 board and their voltages on the schematic.

thank you for the manual link. The service manual I have from Hifi Engine does not show those voltages. having them there is VERY helpful. thank you.

do NOT expect an answer before Monday. I stole precious time to just do this.

I really appreciate all the time you have spent with me so far MTF. I would gladly wait weeks, or even months for the kind of one on one help i am receiving here. It is never my intent to pull you away from the more important things in life. Take your time, and again, I am grateful.

 

[markthefixer]

Next up, I will measure and post the readings for q3, q4, and d9.

Don't need to, with the correct voltages there's no need for troubleshooting.

to pull you away from the more important things in life

This IS pretty important, It's just that in the past I let it get to be TOO high of a priority, to my detriment.... It CAN be addictive....
so these

do NOT expect an answer before Monday. I stole precious time to just do this.

are as much a reminder to myself. plus asking a question in the 9/21 post, then the 9/23 post comes around asking the same question feels like a nudge BACK to the bad old fast answer days.

As for embarrassed, it's MY job to be sure you are doing it right when I get into a thread.

Thus from now on rather than typing a whole tutorial on transistor installation, I will put the burden on the other guy to TELL ME how he intends to install them.

maybe when I come up for air I can reference a few of my old posts that best explain transistor installation. put together an easy to link to post with lots of other links...

oh, and why am I here NOW?

I came home between the days (sat / sun) of the event I am attending, to collapse into some well needed sleep about 10 pm last night.

I heard the DREADED clicking of a dead start relay coming from my refrigerator as I cleared the door.

looked.... no puddles yet, and just too dog tired to do anything about it anyway....

collapsed, passed out and woke up a little while ago, with a little steam restored to defrost the freezer ice into some containers to keep it contained, LEFT the ice in the freezer, and tossed what few other perishables into the freezer with the ice to keep it cool.

man, I just can't catch a break.... :nono:

well, I'm gonna go try for another hour or two of shuteye...

STILL going BACK to the event, the fridge will have to wait until Monday, when I have a fighting chance of getting replacement parts....

as for buying ice to keep things... well... the ice will cost more than what will spoil.... heck I'm paying more than that just for PARKING...

the frozen stuff already defrosted, and can't be re flash frozen....

 

[JoeDotCom]

Don't need to, with the correct voltages there's no need for troubleshooting.

So we are on the upswing here? I smell idle current adjustment on the horizon. (but will wait for your word of course)

the fridge will have to wait until Monday, when I have a fighting chance of getting replacement parts....

Good luck man, that sucks. We lost a bunch of food during the big storms in in chi-town a few weeks ago. no fun. If you need to replace any transistors in the fridge, be sure not to put them in backwards.

 

[markthefixer]

yes, idle current can be adjusted.

don't forget:

The thing to remember is that the equipment that is connected to the dbt can do strange things because of the reduced AC voltage the unit is "seeing". The brighter the bulb, the lower the AC voltage at the unit.

It may be enough that the protection circuit thinks that the AC is turned off....

OR, as idle current is increased (part of testing) and the bulb grows brighter the AC dips below that "magic" protection circuit threshold. It CAN induce butterflies when that happens.

Also while adjustments are done while "under the bulb", they will be in error when the unit is connected straight to the power line.

Of these adjustments:

Offset can be adjusted into the ballpark

BUT

WE NEVER LEAVE IDLE CURRENT SET ANYWHERE BUT THE MINIMUM WHEN TRANSITIONING FROM THE BULB TO THE POWER LINE.
That is because this fresh infusion of FULL AC voltage WILL cause that idle current setting done on the DBT to be WAYYY too high off the bulb.

But we do test the idle current one channel at a time ON the DBT, trying to turn it up to the indicated reading to see if we can tease out any nasty responses while under the safety (and complication) of the bulb. We may NOT get high enough idle current because of the reduced AC voltage while "under the bulb" but it's better than nothing.
THEN we turn back down the idle current on each channel after the test.

to power up a unit, thumbnail of ideal sequence ONLY, there will be variations and decisions/exceptions (none major - especially for idle current):

connect the dbt
turn it on
after it dims, try to adjust any adjustable power supply voltages (only a few units have this)
try to adjust the offset voltages down to zero
one at a time, try setting (then turning back down) the idle current.
if none of these causes the DBT to go on "hard", then:
connect to AC line directly
set any power supply voltages for real
set any offset voltages for real
set any idle current settings for real
go back after 20 min or so of "soak time" and tweak offset and idle.

The sequence of power supply, offset then idle adjusts is paramount, BECAUSE the power supply adjustment affects the offset voltage.

Thus as the power supply warms up, the offset WILL drift a bit - it is unavoidable.
As the output transistors warm up, the idle current will drift a bit, it is also unavoidable.

 

[JoeDotCom]

connect the dbt
turn it on
after it dims, try to adjust any adjustable power supply voltages (only a few units have this)
try to adjust the offset voltages down to zero
one at a time, try setting (then turning back down) the idle current.
if none of these causes the DBT to go on "hard", then:
connect to AC line directly
set any power supply voltages for real
set any offset voltages for real
set any idle current settings for real
go back after 20 min or so of "soak time" and tweak offset and idle.

Thanks Mark. I am excited to hear some music on this thing soon!.

So, if i can follow this sequence with good / stable numbers and get the idle and bias set correctly (first on, then off DBT)... are we good to go then? Can I can move on to a) playing some music on this thing. and then b) replacing each of other components you specked out for me to 'beef things up'?

 

[JoeDotCom]

OK, followed the steps above. All readings looked solid on the DBT and then off the DBT. I left it turned on for 30 min or so then re-tweaked everything. It all looks solid.

So I got brave and connected a junker speaker and a makeshift antenna to the receiver to see if I could get some sound out of it. If you have about 2 minutes to spare (1:47 to be exact) you can even see / hear the joyous sound of the newly operating sx-980 here: http://www.youtube.com/watch?v=v7v2vwGSmzs

Couple more questions though...

1) PS Transistor temp
So after it was on for about 45 min, I turned it off and unplugged it. I checked and the large transistors on the power supply board were really toasty. Hot enough that I could not keep a finger on the heatsink for more than 10 or 20 seconds. I have never had my hand inside a receiver before joining AK, so I am not sure if that is normal operating temperature for those bad boys or not. Are those transistors supposed to be that hot?

2) Moving Forward
If everything is cool with the transistor temperatures above, then we are done troubleshooting/repairing right? So now I can move on to replacing the other components to beef things up? If so, then I will work through the rest of the components I have for the power supply. After installing each new component, i plan to power the receiver on to verify everything is still working and installed correctly.

What is the best indicator to use to verify everything is OK as each component is installed/tested... Will testing the Offset / bias each time be a good way to be sure everything is working smoothly as i go?

Is there a recommended order for the remainder of the parts to be installed in?


YAY It is working!!!! Thank you for all your help, THANK YOU!!!

 

[markthefixer]

They DO get hot...

Power supply then protection. It WILL affect the offset voltage, and will necessitate a re-setting of idle currewnt, including starting out from zero idle current/

once you get the ps, prot and amps upgraded, then you will be able to leave them set and unmolested as you do the rest of the audio circuits.

do a board at a time, not a components at a time between power ups.

most of the caps will have a polarity, film caps (0.1uf to 1.0 uf) do not.

most care must be taken to get the transistors in correctly.

 

[JoeDotCom]

They DO get hot...

Good to know. thanks.

Power supply then protection. It WILL affect the offset voltage, and will necessitate a re-setting of idle currewnt, including starting out from zero idle current/

once you get the ps, prot and amps upgraded, then you will be able to leave them set and unmolested as you do the rest of the audio circuits.

do a board at a time, not a components at a time between power ups.

most of the caps will have a polarity, film caps (0.1uf to 1.0 uf) do not.

most care must be taken to get the transistors in correctly.

ten-four. That all makes sense. I will be very happy when the tinkering is done and can button this thing up and enjoy it. My goal is to work through the rest of this over the next few evenings.

Thanks for everything up to this point MTF, you rule! I have learned so much (and will continue) during this process. Hopefully from here on it will be 'recreational' work rather than emergency repair.

Cheers!

 

[JoeDotCom]

Hi,

just checking here... as i am replacing the caps on the powersupply board, i am noticing c11, c12, and c15 call for 220uF caps in the manual and in your parts list, however what is actually on the board that i am removing are 100uF caps (pic).

Is it OK to be putting in the 'correct' caps as specified in the schematic? Or should i be going back and ordering caps to match the value of what is in there currently?

-joe

 

[ouimetnick]

I'm always told, go what was in the unit. If the receiver came stock with 100µF Caps, then replace them with the same value. Remember, schematics, and part value lists in the service manual are prone to errors.

 

[Japetus]

and:
remember that this unit was running well with these 100µF caps before -> stay with them.

BTW: Now anyone knows your left hand forefinger print - take care where you leave them from now on ...

 

[JoeDotCom]

I'm always told, go what was in the unit. If the receiver came stock with 100µF Caps, then replace them with the same value. Remember, schematics, and part value lists in the service manual are prone to errors.

and:
remember that this unit was running well with these 100µF caps before -> stay with them.

BTW: Now anyone knows your left hand forefinger print - take care where you leave them from now on ...

Thanks for the input. I will plan on collecting a list of items that do not match and then putting in another order.

Question... can I replace everything that DOES match and fire this thing up leaving the couple of 'old' components in place temporarly? (like these original 100uF caps?)

 

[JoeDotCom]

q1 2sd712 npn to-220 bce 100v 4a 30w 55-300hfe 8mhz

Q5 2sd712 npn to-220 bce 100v 4a 30w 55-300hfe 8mhz
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54

[...]
substitutions:

q1 2sd712 100v 4a 30w 55-300hfe 8mhz
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54

Q5 2sd712
512-KSC2073TU

Another question, so I pulled out Q1 and Q5. They are both in line to be replaced with part 512-KSC2073TU above

However, i just wanted to check on their markings...
Q1 is labeled D712 8YR-D
Q5 is labeled D712 8XV-D

I see above that we are doing some substitutions above, but I can only understand a percentage of all the numbers up there. Are we cool to replace both the 8YR-D and the 8XV-D transistors with the 512-KSC2073TU?

 

[avionic]

Another question, so I pulled out Q1 and Q5. They are both in line to be replaced with part 512-KSC2073TU above

However, i just wanted to check on their markings...
Q1 is labeled D712 8YR-D
Q5 is labeled D712 8XV-D

I see above that we are doing some substitutions above, but I can only understand a percentage of all the numbers up there. Are we cool to replace both the 8YR-D and the 8XV-D transistors with the 512-KSC2073TU?

Yes..

 

[JoeDotCom]

Yes..

 

[Watthour]

Likely date or lot codes, since they aren't a suffix to the part no.