I would guess that the cleaning behavior of flux (rosin) in rosin-core solder would be plenty. If you're using rosin-core solder (which you should), then you don't need to DeOxit the posts beforehand.
SX-850 Restoration Record
- Thread starter davros
- Start date
I would guess that the cleaning behavior of flux (rosin) in rosin-core solder would be plenty. If you're using rosin-core solder (which you should), then you don't need to DeOxit the posts beforehand.
davros
Active Member
All Boards, with the exception of the Main Amp board have been recapped.
The known bad transistors have been changed (2SA725, 2SA726)
Along with Q1,Q2,Q8,Q9 on the power supply board, Per Watthour and Zebulons recommendation.
Started with DimBulb and relay kicked in, removed from DimBulb and checked power supply voltages.
(AWR-101)
Pin............Schematic voltage....Actual Voltage
Pin 2,3.........5.4V........................5.1V
Pin 4,5........13.9.........................13.3V
Pin 6,7.........51.5V......................50.3V
Pin 8,9,10....36.5V......................35.5V
Pin 11..........28V.........................27.2V
Pin 13.........-13.5V......................-13.2V
Pin 14..........-51.5V.....................-51.7V
Pin 15..........-19V........................-18.99V
At this point it was Bed Time, and right before I was to turn it off, the protection relay kicked out, 5 seconds later it kicked back in. I rechecked my readings (Same) and the relay kicked out a second time, and like before about 5 seconds later it came back on.
Radio was at low volume with 2 cheap 8 Ohm speakers. No Static or sound artifacts were heard. The relay kicked out so softly I wasn't sure if I just lost the radio station or not (no Antenna)
At this point I powered down for the night.
My Question now is, at my next session, do I power up and get the protection board readings, or do I move on to the Power Amp Board?
Could Recapping all but the Amp Board throw it out of whack? Or is it more likely something else?
The purpose of doing one board at a time was to make sure if I messed up I could backtrack easily. The TO-220's were the last thing I did. Solder joints look good...
The known bad transistors have been changed (2SA725, 2SA726)
Along with Q1,Q2,Q8,Q9 on the power supply board, Per Watthour and Zebulons recommendation.
Started with DimBulb and relay kicked in, removed from DimBulb and checked power supply voltages.
(AWR-101)
Pin............Schematic voltage....Actual Voltage
Pin 2,3.........5.4V........................5.1V
Pin 4,5........13.9.........................13.3V
Pin 6,7.........51.5V......................50.3V
Pin 8,9,10....36.5V......................35.5V
Pin 11..........28V.........................27.2V
Pin 13.........-13.5V......................-13.2V
Pin 14..........-51.5V.....................-51.7V
Pin 15..........-19V........................-18.99V
At this point it was Bed Time, and right before I was to turn it off, the protection relay kicked out, 5 seconds later it kicked back in. I rechecked my readings (Same) and the relay kicked out a second time, and like before about 5 seconds later it came back on.
Radio was at low volume with 2 cheap 8 Ohm speakers. No Static or sound artifacts were heard. The relay kicked out so softly I wasn't sure if I just lost the radio station or not (no Antenna)
At this point I powered down for the night.
My Question now is, at my next session, do I power up and get the protection board readings, or do I move on to the Power Amp Board?
Could Recapping all but the Amp Board throw it out of whack? Or is it more likely something else?
The purpose of doing one board at a time was to make sure if I messed up I could backtrack easily. The TO-220's were the last thing I did. Solder joints look good...
Watthour
Electron Rancher - JS3600
The PS voltages appear to be acceptable (pretty darned good, in fact). Changing the supply voltages even slightly by installing new components could have altered the offset and idle current settings. In the morning the unit can be powered on at zero volume to get the the offset and idle readings.
Use all the usual cautions in connecting for readings and when adjusting the trimmers.
Use all the usual cautions in connecting for readings and when adjusting the trimmers.
davros
Active Member
SO here is the update,
With the pre-amp jumpers removed, volume at 0, speakers connected I read the following
Amp Board
Pins 9 to 10 .3mV
Pins 24 50 25 26mV
Pins 12 to 13 20.3 mV
Pins 27 to 28 22.3 mV
Protection Board
Pin 2 -13.14
Pin 9 8.63
Pin 12 7.28 AC
The Protection relay dropped out only twice during these readings. Each time was was for just long enough for the relay to re-engage. No reading were taken during a dropout.
Each time a very faint noise could be heard in the speaker(s) when the relay clicked off. It did not precede the relay click, rather it was at the click. I couldn't tell if it was just one or both. Might have just been normal noise.
With the pre-amp jumpers removed, volume at 0, speakers connected I read the following
Amp Board
Pins 9 to 10 .3mV
Pins 24 50 25 26mV
Pins 12 to 13 20.3 mV
Pins 27 to 28 22.3 mV
Protection Board
Pin 2 -13.14
Pin 9 8.63
Pin 12 7.28 AC
The Protection relay dropped out only twice during these readings. Each time was was for just long enough for the relay to re-engage. No reading were taken during a dropout.
Each time a very faint noise could be heard in the speaker(s) when the relay clicked off. It did not precede the relay click, rather it was at the click. I couldn't tell if it was just one or both. Might have just been normal noise.
davros
Active Member
Unless the gurus advise against it, I will likely recap the amp board, replace the Bias and Offset pots, and replace the known troubled transistors.
With the entire unit cleaned recapped and known troublesome transistors replaced, chasing the intermittent protection may prove difficult.
I won't be able to get to this until Monday, so I have a little time to ponder it over....
With the entire unit cleaned recapped and known troublesome transistors replaced, chasing the intermittent protection may prove difficult.
I won't be able to get to this until Monday, so I have a little time to ponder it over....
davros
Active Member
So I have started the Amp Board (AWH-059) , and I have a question.
I plan to replace the 726's, the trim pots, and the capacitors.
Is there any other items that are "must do's" ?
Also, as I remove the heatsink, with the 2SB531A and 2SD371 Outputs, I have to wonder if replacing them with the MJ21193G, and MJ21194G would be a good idea? I already have them, so cost isn't an issue, and I have them removed anyway, so it's literally no more work.
Most parts are already on hand to do this, but I would like to keep this as simple as possible. The Amp board is not a Board to be trifled with IMO.
I plan to replace the 726's, the trim pots, and the capacitors.
Is there any other items that are "must do's" ?
Also, as I remove the heatsink, with the 2SB531A and 2SD371 Outputs, I have to wonder if replacing them with the MJ21193G, and MJ21194G would be a good idea? I already have them, so cost isn't an issue, and I have them removed anyway, so it's literally no more work.
Most parts are already on hand to do this, but I would like to keep this as simple as possible. The Amp board is not a Board to be trifled with IMO.
Sounds like you're already doing it, but be sure to clean off the old thermal grease, replace the mica insulators on the output transistors, and put back together with new thermal grease like Avis's Thermalcote.
davros
Active Member
OK, I forged ahead and I can see the light at the end of the tunnel!
Amp Board is recapped,
726's have been replaced,
Trim Pots have been replaced (Could the leads have been shorter!?)
20 Minutes in Bias position on DBT no issues.
Biased to 20mv
Offset set to 0 +/- 1mv (It bounces up and down 2mv) it go's from -.1 to .1
Did it again on line power no DBT and no changes necessary.
Realized I didn't do the filter caps yet, so I'll do that tomorrow.
Then I'll recheck Bias and put it back together.
Now off to bed, my back is a mess from leaning over this table all afternoon...
My hats off to the guys who do this for a living, I would starve if this was my main Gig! If I was any slower I'd be going in reverse.
Amp Board is recapped,
726's have been replaced,
Trim Pots have been replaced (Could the leads have been shorter!?)
20 Minutes in Bias position on DBT no issues.
Biased to 20mv
Offset set to 0 +/- 1mv (It bounces up and down 2mv) it go's from -.1 to .1
Did it again on line power no DBT and no changes necessary.
Realized I didn't do the filter caps yet, so I'll do that tomorrow.
Then I'll recheck Bias and put it back together.
Now off to bed, my back is a mess from leaning over this table all afternoon...
My hats off to the guys who do this for a living, I would starve if this was my main Gig! If I was any slower I'd be going in reverse.
davros
Active Member
Filter caps are replaced!
Those Caps were solidly out of Spec. Both read between 9400 - 9600 uF. Out of a rating of 15,000uF that's a pretty big drift in value. My Cheap little tester can test to 20,000uF where my Fluke can only test to 10,000. I thought the Cheap tester was bad, but my Fluke was able to back it up.
The new 18,000 uF caps read 18,500 uF each (cheap tester) OVL on the Fluke. So that's pretty much a doubling of the filter caps, not to mention any ESR / Ripple differences.
Last thing I did was DeOxit the terminals (Wire Wrap Posts). I used the needle dispensers (so much easier than spray!) to get 100% D5 into the wraps. After about 5 Min I used Q-Tips to soak up any leftover. The 100% from the bottle doesn't dry as fast as the 5% from the aerosol can. Followed up with DeOxit Gold to prevent them from corroding in the future.
After all that, I warmed up for 20 min and I readjusted the Bias (Both had gone down to 18mV. I'm not sure if that was because of the DeOxit changing anything, or just natural drift. Once set it stayed withing +/- 1mV for another 20 Minutes.
The protection relay issue I had earlier seems to have gone away, Likely due to the work on the Amp Board.
At this point I put the Pre-Amp jumpers back in and hooked to my test speakers. Beautiful and glorious sound.... Out of the left speaker....
Turning the volume up a little "pushed" the glorious sound to both speakers...
Another half dozen try's later I powered down and cleaned the relay contacts. Problem disappeared, and now works fine. Guess its time to research a new Relay. I should have just done it in the first place........
It was now 10P.M. so I left it disassembled and went to bed. Tomorrow /Today will see the reassembly and hook up to my main speakers, and I'll break her in!
Those Caps were solidly out of Spec. Both read between 9400 - 9600 uF. Out of a rating of 15,000uF that's a pretty big drift in value. My Cheap little tester can test to 20,000uF where my Fluke can only test to 10,000. I thought the Cheap tester was bad, but my Fluke was able to back it up.
The new 18,000 uF caps read 18,500 uF each (cheap tester) OVL on the Fluke. So that's pretty much a doubling of the filter caps, not to mention any ESR / Ripple differences.
Last thing I did was DeOxit the terminals (Wire Wrap Posts). I used the needle dispensers (so much easier than spray!) to get 100% D5 into the wraps. After about 5 Min I used Q-Tips to soak up any leftover. The 100% from the bottle doesn't dry as fast as the 5% from the aerosol can. Followed up with DeOxit Gold to prevent them from corroding in the future.
After all that, I warmed up for 20 min and I readjusted the Bias (Both had gone down to 18mV. I'm not sure if that was because of the DeOxit changing anything, or just natural drift. Once set it stayed withing +/- 1mV for another 20 Minutes.
The protection relay issue I had earlier seems to have gone away, Likely due to the work on the Amp Board.
At this point I put the Pre-Amp jumpers back in and hooked to my test speakers. Beautiful and glorious sound.... Out of the left speaker....
Turning the volume up a little "pushed" the glorious sound to both speakers...
Another half dozen try's later I powered down and cleaned the relay contacts. Problem disappeared, and now works fine. Guess its time to research a new Relay. I should have just done it in the first place........
It was now 10P.M. so I left it disassembled and went to bed. Tomorrow /Today will see the reassembly and hook up to my main speakers, and I'll break her in!
davros
Active Member
Soooo......
After another 20 Min of listening to FM today, I cleaned up my mess, replaced covers,buttons,and knobs and moved the SX-850 to its new home.
I hooked up my main speakers, various inputs, and antenna and went back to listening to FM at low volume while I continued putting away my gear. A break in period if you will...
After another 10 minutes, I walked into another room, and I came back and noticed it was quiet... to quiet....
No smells, no "pop", no weird behavior. But the protection relay had switched off. I shut it down and gave it a few minutes, then tried it again but the relay never clicked back on.
Lights are on, gauges work for FM and signal strength, just no relay.
Looks like its back to the bench.
Tomorrow... I do't think I can bear to look in it again today
Time to read the multitude of "My relay won't engage" posts...
****If it would be wiser to start a new thread I can.
I will likely need some guidance unless I can find an obvious issue.
Man.... I was all ready to post a success picture.....
After another 20 Min of listening to FM today, I cleaned up my mess, replaced covers,buttons,and knobs and moved the SX-850 to its new home.
I hooked up my main speakers, various inputs, and antenna and went back to listening to FM at low volume while I continued putting away my gear. A break in period if you will...
After another 10 minutes, I walked into another room, and I came back and noticed it was quiet... to quiet....
No smells, no "pop", no weird behavior. But the protection relay had switched off. I shut it down and gave it a few minutes, then tried it again but the relay never clicked back on.
Lights are on, gauges work for FM and signal strength, just no relay.
Looks like its back to the bench.
Tomorrow... I do't think I can bear to look in it again today
Time to read the multitude of "My relay won't engage" posts...
****If it would be wiser to start a new thread I can.
I will likely need some guidance unless I can find an obvious issue.
Man.... I was all ready to post a success picture.....
davros
Active Member
I have a relay on order as I know it will need to be replaced. The push-through effect was unexpected but fairly typical as I've read.
When I took the relay apart, I polished the contacts and applied deoxit/ deoxit gold. The first time I ran it it clicked but no sound out of one channel. I had to re-tighten the screw, and then it worked great.
Now it wont even engage. I'm hoping the coil went out, but that's not a failure I've read about even once on here, so my hopes aren't that high that that's it.
After work today I can get voltages off the power supply and the protection board and see where I am at...
When I took the relay apart, I polished the contacts and applied deoxit/ deoxit gold. The first time I ran it it clicked but no sound out of one channel. I had to re-tighten the screw, and then it worked great.
Now it wont even engage. I'm hoping the coil went out, but that's not a failure I've read about even once on here, so my hopes aren't that high that that's it.
After work today I can get voltages off the power supply and the protection board and see where I am at...
davros
Active Member
OK, So here we go....
Power supply
pin2,3 5.1
pin4,5 13.2
pin6,7 50.3
pin8,9,10 -1
pin11 -1
pin13 -13.2
pin14 -51.5
pin15 -19.5
So, it looks to me like Q5, I thought for sure I changed that when I had Q1,2&,8,9 out. Careful inspection shows that to not be true.
Anyone care to reaffirm this is a Q5 issue?
Any other thoughts?
Power supply
pin2,3 5.1
pin4,5 13.2
pin6,7 50.3
pin8,9,10 -1
pin11 -1
pin13 -13.2
pin14 -51.5
pin15 -19.5
So, it looks to me like Q5, I thought for sure I changed that when I had Q1,2&,8,9 out. Careful inspection shows that to not be true.
Anyone care to reaffirm this is a Q5 issue?
Any other thoughts?
Pageplayer
Active Member
Hang in there Davros. I'm also learning this new hobby. It feels great when everything goes as planned, but sucks when a simple change disrupts something else.
Thanks for the log of your work. Interesting.
Thanks for the log of your work. Interesting.
davros
Active Member
Oh, I've come to far to quit now. After reading quite a few posts concerning Q5,
Between reading the schematic last night and suspecting Q5, to then reading the old posts concerning others peoples problem with Q5, I am fairly confident the loss of power on Pins 8-9-10-11 is caused by Q5.
I will change it out tonight, and report back the results.
Between reading the schematic last night and suspecting Q5, to then reading the old posts concerning others peoples problem with Q5, I am fairly confident the loss of power on Pins 8-9-10-11 is caused by Q5.
I will change it out tonight, and report back the results.
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