Pioneer RT-909 Trouble
- Thread starter snailman
- Start date
elnaldo
Lunatic Member
Here is a schematic for the darlington:
http://html.alldatasheet.co.kr/html-pdf/37508/SAMSUNG/KSD560/245/1/KSD560.html
It seems OK to measure a diode voltage drop from emitter to collector, but not from collector to emitter.
Are you testing the unit with the tape loaded? Without the tape the reel motors run very fast.
If so, just measure the voltages at the regulator you just fixed, to see if it's OK, and then we can proceed to search for another problem.
dnpainting
Super Member
Also, check to make sure you don't have a cold solder joint or solder bridge on the parts you put in.
elnaldo
Lunatic Member
Can you post the schematic, or the part where Q210 is? I can't find it in my RT901 schematic.
You need to be careful, check the work you did once finished, check continuity between points, be sure everything is fine. you never know where your fail can end. If hi voltages are involved, some serious incident could happen.
I've burned my amp once, including an obsolete "unobtainium" IC (I had to replace it and adapt the circuit) because I forgot to solder one capacitor ground. Now I'm more careful and check everything twice before powering on.
You need to be careful, check the work you did once finished, check continuity between points, be sure everything is fine. you never know where your fail can end. If hi voltages are involved, some serious incident could happen.
I've burned my amp once, including an obsolete "unobtainium" IC (I had to replace it and adapt the circuit) because I forgot to solder one capacitor ground. Now I'm more careful and check everything twice before powering on.
Here is the schematic:
The service manual linked by dnpainting (http://www.kallhovde.com/pioneer/rt-909sm.pdf) is what I've been using. This board is on page 57.
The service manual linked by dnpainting (http://www.kallhovde.com/pioneer/rt-909sm.pdf) is what I've been using. This board is on page 57.
Attachments
Partial Success!
I found and fixed another problem. Turns out I accidentally replaced D223 instead of ZD201.
Replacing the correct diodes, the system powers up, the meter and counter are lit, and the functions engage when the buttons are pressed.
However, the servos do not engage when play is pressed, and the capstan motor doesn't turn. The H-bridge area also gets rather hot, and it smells warm.
I am assuming I need to test (and replace) the H-bridge transistors?
I found and fixed another problem. Turns out I accidentally replaced D223 instead of ZD201.
Replacing the correct diodes, the system powers up, the meter and counter are lit, and the functions engage when the buttons are pressed.
However, the servos do not engage when play is pressed, and the capstan motor doesn't turn. The H-bridge area also gets rather hot, and it smells warm.
I am assuming I need to test (and replace) the H-bridge transistors?
dnpainting
Super Member
Cold solder joint?
Reflow joints
Reflow joints
Lucky. I don't see a scenario that could have taken out the capstan motor.
It is time to get systematic. Do only as you are told, or you will be on your own.
Don't do a dang thing until you have read this complete post and digested it completely. While soldering, disassembling and reassembling, unplug the power cord and put the plug in a zip-lock sandwich bag. after repair work, clean the area you worked on with pure isopropyl alcohol, and examine every square inch of the board(s) foil side with at least 10x magnification (cold joints, solder bridges, etc.), and check for any broken wires in the area. This will go a long way to prevent recurrence of what just happened.
Q210 shorted, collector to base, turns into a diode, feeding the supply voltage and current to the anode of D222. Now, control logic usually prevents Q210 and Q212 from turning on at the same time, but the short allows that condition (bad mojo). The only thing limiting the current, when Q212 turns on ("play" in some direction (no time to work it out & signals are not labelled)), is how hard Q22 is pulling on Q212's collector (probably full on since the capstan cannot turn without current going through it).
Here is the list of possible blown/overstressed parts, depending on the time that power was applied, and failure modes of individual parts: Q210, D222, Q212. Now to the capstan motor assy: Q22, Q21, IC21. If time was real short, you may not have blown up anything. You may have just taken out a fuse (FU4, 4A). If Q245 was working, your new Q214 was probably spared. If not, add Q214 to the list, and possibly D223, and of course Q245 which would not have been working, to allow Q214 to be taken out.
Now, if you blew FU4, I'm concerned about the proper functioning of Q214 and Q245. The provided supply voltage should have folded back, protecting all the downstream parts, and Q214. The fuse should not have blown. If it did blow, you had well over 4A going somewhere, and that is bad news.
Take Q210, Q212, and D222 out of the circuit, and test them. Remove Q214 and Q245 and test them. Put good Q214 and 245 in, leaving Q210, D222, and Q212 out. Ensure that S2 & S3 are open (tape presence guides in "no tape loaded" position). Connect up your DC meter to measure the voltage at the junction of R293 and Q245-emitter (ref'd to ground). Put in a good fuse in FU4. Watch the meter and power up the unit. If the fuse blows, or you get anything other than around 24vDC on the meter, shut back down quick. If you get 24V, power back down and start working on the H-bridge (motor drive).
H-bridge work: put known good parts in Q210, D222, and Q212. Close S2 and S3 by rotating the tape presence guides to simulate a loaded tape (hold them with a rubber band). Connect your DC meter to measure the DC voltage on Q210's emitter (ref'd to ground). Power up the unit, record the reading. It should be around 24 volts. Power down the unit. If OK so far, connect your DC meter to measure the voltage on the collector of Q212 (ref'd to ground). Power up the unit, and record the voltage in "stop" mode. Verify that the capstan is not spinning. Select "play" in either direction. Record the voltage. Verify that the capstan is spinning. Power down the unit.
Do nothing else, period, and report back your findings. I know you really want to get this going, but at the moment, you are in a downward spiral. There are some unobtainium parts in there, and if they are still good, they are at risk of biting the schnitzel at the current rate. Slow down, and do only what you are told. Then report back your findings and wait for further instructions. There can be only one line of guidance, and that does not include your own taking of initiative. What that means, is you need to pick a troubleshooting path and stick with it. You can't go down multiple roads and expect good results. Slow down. Be meticulous and extra careful. Don't be in a hurry, or easily frustrated. Remote troubleshooting is very slow, and must be done carefully and accurately. No one can keep up with your actions as it is right now.
Pick a guiding voice, and follow that one's instructions, to the letter, ignoring all other input, unless the selected voice agrees. If my voice is not the one selected, let me know and I will withdraw. If mine is the selected voice, heed my voice exclusively. The others will speak to me. I will listen to them. You ignore them. For you, you and I are having a private conversation, overheard by the others. I may be talking to others, but you are not, and they are not to address you. Those are my terms. I have not done remote troubleshooting for quite a while, but have a bit of available time, and am willing to do it this time, until my terms are significantly breached, or my guidance is rejected (this is an acceptable choice), or we reach some conclusion.
Rich P
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FU4 and FU5 are blown.
I will remove and test those components.
The unit was playing for about 15 minutes, and it was on for about 30 seconds again after I put the cover on.
Just out of curiosity, why did it work after removing the solder bridge, and swapping the diodes?
If IC21 is bad, will this need to be sourced from a parts unit?
I will remove and test those components.
The unit was playing for about 15 minutes, and it was on for about 30 seconds again after I put the cover on.
Just out of curiosity, why did it work after removing the solder bridge, and swapping the diodes?
If IC21 is bad, will this need to be sourced from a parts unit?
FU4 I was prepared for. FU5 is going to be another story. You may have a pinched wire or one has broken off and touched somewhere it should not have. Either way, it is bad news. We can't go both directions at once, so we will deal with FU4's path.
Playing the unit with obvious indications of stress (getting hot and smelling) was not a good idea. We won't be doing that again.
Removing the solder bridge and swapping the diodes may have cleared up some of your issues. I can't tell from here, with the current data available. We still do not know that the parts are in correctly, or are not damaged. We will find that out shortly. Parts must be correct and installed correctly from here on (oriented correctly and soldered in correctly).
The capstan motor and IC21 are made out of unobtainium. I see folks claiming to sell IC21, but I have no experience with them, and the parts are likely Chinese counterfeits. You will likely need a parts unit or contributions from someone with a parts unit.
Replace FU4 and FU5 and perform my previous instructions up to a point where you may detect a failure, or you get to the end of them. Report back on your findings. If FU4 or 5 pops, that is where you stop, power down and report back. Do nothing else.
When you report back findings, stop and wait for a response and further instructions, no matter how long it takes for the response to come. I am juggling many balls right now. Guidance will be formulated based upon your most recent post. If you take initiative, conditions will change. While you were playing the unit, I was writing my instructions. We had not established a remote troubleshooting relationship, but if we had, the current issue would not have occurred.
So, do, then report back and wait for further instructions.
We can discuss the whys of things at the end of each inning, but we don't have time or required background info to discuss it during play. Just be my eyes and hands. By the way...post a nice picture of your soldering iron, and especially its tip. I want to see what you are working with.
Rich P
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I will continue to follow your instructions and update as they are completed.
My schedule is also a bit hectic, so it may take a couple days before I can get things done.
Attached are photos of my soldering iron. If this one isn't good, I have a few others around here somewhere.
I cannot thank you enough for offering to help me with this. :ntwrthy:
My schedule is also a bit hectic, so it may take a couple days before I can get things done.
Attached are photos of my soldering iron. If this one isn't good, I have a few others around here somewhere.
I cannot thank you enough for offering to help me with this. :ntwrthy:
Attachments
I don't like your soldering iron. you need something more suitable for detailed electronic pcb work, something with a long tapered tip that is somewhat chisel shaped at the clean, well tinned business end. You also need to have a nice soldering sponge to keep the tip clean. There is not much tinned end on yours to work with, and it is too blunt and broad, so you will likely get a lot of solder bridges and cold joints. Get a nice solder sucker, solder iron stand, small gauge solder braid, and a way of dispensing your isopropyl alcohol as needed. You will also need a small, stiff-bristled brush, for cleaning the circuit board after work has been done on it. An old toothbrush will do.
You need a nice space to work in, with plenty of lighting, preferably that which you can move around to get better illumination at various angles.
Use eye protection - lab goggles (mine have reading glass portions in them). Hot solder or other things in the eyes immediately negates the value of working audio equipment. Regular glasses are better than nothing...until they are not. Solder can splash past the sides. Don't ask me how I know. Lets just say that I have a set of lab goggles with a melted place on the inside of one lens from hot stuff coming off of a tantalum cap that blew up in my face.
I know these are added expenses, and you do not have to do this part, but you will be glad you do, for each item that you do.
I will be giving you instructions, and generally, indicating what you should see. If I do tell you what you should see, and you do not see it, that is a fail. Stop, power down, and report back. If you encounter a fail, while executing a series of instructions or measurements, do not proceed to the next step. Just stop, power down and report back.
I am not in a hurry. You must not be. Remember, do what you're told, in the manner and sequence you are told, nothing more. If you are not sure about some procedure or sequence, do nothing until you do. Just report back and ask.
Put some heat-shrink tubing on your meter leads, so that only the very tips are exposed. You do not want to make shorts while taking measurements. Make sure your meter lead tips are nice and pointy, so they don't slip around on contact points and so they penetrate any oxidation or coating on test point(s).
If you need to, solder a small bit of resistor lead or some such to a point to be probed, so you can hang your meter lead from it. Remove it when you no longer need it.
Here at the beginning, especially while the unit is blowing fuses, you will be instructed to connect meters to points, power up the unit, take some action(s) and measure and record the meter reading. This is critical. You do not want to expose sensitive circuits to unacceptable voltages or loads at all, but sometimes it is unavoidable so we will keep it very brief. You definitely want to be able to hang you meter leads off the test point(s) for these measurements.
I'm concerned about FU5 blowing. Before you execute my previous instructions, remove D228 and D229, and verify that they are OK. Pray that they are, because Hell will want to be paid if not. If good, put them back in (correctly located and oriented and soldered in).
Rich P
You need a nice space to work in, with plenty of lighting, preferably that which you can move around to get better illumination at various angles.
Use eye protection - lab goggles (mine have reading glass portions in them). Hot solder or other things in the eyes immediately negates the value of working audio equipment. Regular glasses are better than nothing...until they are not. Solder can splash past the sides. Don't ask me how I know. Lets just say that I have a set of lab goggles with a melted place on the inside of one lens from hot stuff coming off of a tantalum cap that blew up in my face.
I know these are added expenses, and you do not have to do this part, but you will be glad you do, for each item that you do.
I will be giving you instructions, and generally, indicating what you should see. If I do tell you what you should see, and you do not see it, that is a fail. Stop, power down, and report back. If you encounter a fail, while executing a series of instructions or measurements, do not proceed to the next step. Just stop, power down and report back.
I am not in a hurry. You must not be. Remember, do what you're told, in the manner and sequence you are told, nothing more. If you are not sure about some procedure or sequence, do nothing until you do. Just report back and ask.
Put some heat-shrink tubing on your meter leads, so that only the very tips are exposed. You do not want to make shorts while taking measurements. Make sure your meter lead tips are nice and pointy, so they don't slip around on contact points and so they penetrate any oxidation or coating on test point(s).
If you need to, solder a small bit of resistor lead or some such to a point to be probed, so you can hang your meter lead from it. Remove it when you no longer need it.
Here at the beginning, especially while the unit is blowing fuses, you will be instructed to connect meters to points, power up the unit, take some action(s) and measure and record the meter reading. This is critical. You do not want to expose sensitive circuits to unacceptable voltages or loads at all, but sometimes it is unavoidable so we will keep it very brief. You definitely want to be able to hang you meter leads off the test point(s) for these measurements.
I'm concerned about FU5 blowing. Before you execute my previous instructions, remove D228 and D229, and verify that they are OK. Pray that they are, because Hell will want to be paid if not. If good, put them back in (correctly located and oriented and soldered in).
Rich P
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If IC21 is the logic control IC, good luck. I had similar problems with my 909, and needed to buy the entire board out of a donor just to get that IC.
Mine worked fine after that.
Glenn
Mine worked fine after that.
Glenn
IC501 (AN6251) was actually the IC I had issues with, still difficult to find though.
IC21 is a Mitsubishi M51970L Motor Speed Control for the capstan FG Servo. It is in an 8-pin SIP package. When Pioneer last sold them (they are permanently out of them now), they sold them for $42 each.
Unless the previous diddling with the 24V regulator circuitry caused excessive voltage to be applied to the chip, for too long (quite possible), the chip might be OK. Excessive voltage could have take out the chip's local supply regulator, ZD21, a 250 mW, 15V zener. if that is true, R29 (680 ohm 1/4 W resistor) must also be checked.
Let's wait to check this stuff until we get the 24V regulator working correctly. We'll check this in its time.
Rich P
Unless the previous diddling with the 24V regulator circuitry caused excessive voltage to be applied to the chip, for too long (quite possible), the chip might be OK. Excessive voltage could have take out the chip's local supply regulator, ZD21, a 250 mW, 15V zener. if that is true, R29 (680 ohm 1/4 W resistor) must also be checked.
Let's wait to check this stuff until we get the 24V regulator working correctly. We'll check this in its time.
Rich P
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dnpainting
Super Member
Just a suggestion Rich for the OP, snailman may want to get himself a heatsink (alligator clip) of some kind as to avoid overheating diodes and such.
Hope you are doing well Rich and I thank you for all your help with my 909.
Hope you are doing well Rich and I thank you for all your help with my 909.
If you have an appropriate solder iron and tip, I find clip-on heatsinks too cumbersome to be of value. For those with limited soldering skill and/or non-optimal soldering gear, a clip on heatsink might be in order. RadioShack used to carry a soldering kit that had a couple of heatsink clips in it, but you would be hard-pressed to get much of anything of value from them these days.
I don't remember our work on your deck, but that can be explained by my age-related cognitive degeneration
. In any case, you are welcome.Rich P