SX 727 left channel speaker crackle help!

OK!!!!

Recently bought a 727 for £20 that was looking a bit sorry for itself! It has cleaned up well, but has one major issue that really needs to be tackled!

In the left hand channel there is a lot of crackles and pops that occour even when the volume is at 0 or full, its still the same.

When I turn the amp on to speaker A (with speakers hooked up to A) there is no crackle at all. However, after a 2 seconds of turning on there is almost a small 'click' , 'dong' or 'tap' almost like something has just kicked in and then the crackling and popping starts. The warmeer the amp gets the worse it seems to get.

I have had the top, face and bottom plat off, and the connections to the large capacitors at the back all look very clean, along with the output transistors.

Any help on the issue would be great, as I would love to hear her sing again!

Cheers!

Try cleaning the pots with deoxit, I had the same problem with the volume pot on my SX 3700.

Sounds like a transistor is failing.

Best easy attack is to replace the smaller amplifier transistors located on the amplifier pc board.

Then there are 4 transistors on the AF card that also could do this.

with it open it is also a good time to replace the electrolytic capacitors.

you will be surprised just how well things will work out when that is done.

I will have to make up a list of replacement transistors, (and capacitors) from Mouser.com in the states (also have outlets in UK)

here's an old capacitor list from my notes - some numbers may be old/obsolete.. don't sweat it (yet)

General c1 6800uF 50v CEW 647-UVZ1J682MRD 6800 63 $3.72 25x50mm
General c2 6800uF 50v CEW 647-UVZ1J682MRD 6800 63 $3.72 25x50mm
General c3 1000uF 63v CEW 647-UPW2A102MHD 1000 100 $2.06
General c6 220uF 10v CEA 647-UPW1A221MED 220 10 $0.18
General c7 330uF 16v CEA 647-UPW1E331MPD6 330 25 $0.28
General ? 220uF 50v CEA 647-UPW1J221MPD6 220 63 $0.62

phono /head amp
W21-002 c1 22uF 16v CEA 647-UPW1V220MDD 22 35 $0.15
W21-002 c2 22uF 16v CEA 647-UPW1V220MDD 22 35 $0.15
W21-002 c3 4.7uF 25v CEA 647-UPW1H4R7MDD 4.7 50 $0.12
W21-002 c4 4.7uF 25v CEA 647-UPW1H4R7MDD 4.7 50 $0.12
W21-002 c5 10uF 25v CEA 647-UPW1H100MDD 10 50 $0.12
W21-002 c6 10uF 25v CEA 647-UPW1H100MDD 10 50 $0.12
W21-002 c15 220uF 35v CEA 647-UPW1V221MPD 220 35 $0.22

tuner
AWE-015 c2 .47uF 50v CEA 598-DSF050J474 0.47 50 $0.29
AWE-015 c23 4.7uF 25v CEA 647-UPW1H4R7MDD 4.7 50 $0.12
AWE-015 c27 1uF 50v CEA 647-UPW1H010MDD 1 50 $0.12
AWE-015 c29 4.7uF 25v CEA 647-UPW1H4R7MDD 4.7 50 $0.12
AWE-015 c30 1uF 50v CEA 647-UPW1H010MDD 1 50 $0.12
AWE-015 c33 100uF 16v CEA 647-UPW1V101MPD 100 35 $0.26
AWE-015 c36 10uF 16v CEA 647-UPW1H100MDD 10 50 $0.12
AWE-015 c38 .47uF 50v CEA 598-DSF050J474 0.47 50 $0.29
AWE-015 c45 10uF 16v CEA 647-UPW1H100MDD 10 50 $0.12
AWE-015 c53 .47uF 25v CSSA 598-DSF050J474 0.47 50 $0.29
AWE-015 c54 4.7uF 25v CEA 647-UPW1H4R7MDD 4.7 50 $0.12
AWE-015 c55 3.3uF 16v CSSA 647-UKL1H3R3KDDANA 3.3 50 $0.20
AWE-015 c57 3.3uF 16v CSSA 647-UKL1H3R3KDDANA 3.3 50 $0.20
AWE-015 c58 1uF 50v CEA 647-UPW1H010MDD 1 50 $0.12
AWE-015 c61 .47uF 50v CEA 598-DSF050J474 0.47 50 $0.29
AWE-015 c65 100uF 16v CEA 647-UPW1V101MPD 100 35 $0.26
AWE-015 c66 2.2uF 16v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWE-015 c67 2.2uF 16v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWE-015 c73 47uF 16v CEA 647-UPW1E470MDD 47 25 $0.19

af amp
AWK-010 c7 47uF 50v CEA 647-UPW1H470MED 47 50 $0.22
AWK-010 c8 47uF 50v CEA 647-UPW1H470MED 47 50 $0.22
AWK-010 c13 2.2uF 25v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWK-010 c14 2.2uF 25v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWK-010 c15 47uF 10v CEA 647-UPW1E470MDD 47 25 $0.19
AWK-010 c16 47uF 10v CEA 647-UPW1E470MDD 47 25 $0.19
AWK-010 c21 2.2uF 25v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWK-010 c22 2.2uF 25v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWK-010 c27 2.2uF 25v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWK-010 c28 2.2uF 25v CSSA 647-UKL1H2R2MDDANA 2.2 50 $0.20
AWK-010 c29 100uF 6.3v CEA 647-UPW1A101MDD 100 10 $0.14
AWK-010 c30 100uF 6.3v CEA 647-UPW1A101MDD 100 10 $0.14
AWK-010 c31 47uF 50v CEA 647-UPW1H470MED 47 50 $0.22
AWK-010 c32 47uF 50v CEA 647-UPW1H470MED 47 50 $0.22

power amp
AWH-011 c7 22uF 10v CEA 647-UPW1V220MDD 22 35 $0.15
AWH-011 c8 22uF 10v CEA 647-UPW1V220MDD 22 35 $0.15
AWH-011 c9 220uF 10v CEA 647-UPW1A221MED 220 10 $0.18
AWH-011 c10 220uF 10v CEA 647-UPW1A221MED 220 10 $0.18
AWH-011 c15 100uF 50v CEA 647-UPW1H101MPD 100 50 $0.22
AWH-011 c16 100uF 50v CEA 647-UPW1H101MPD 100 50 $0.22

protection
AWM-027 c3 470uf 6.3v CEA 647-UPW1C471MPD 470 16 $0.34
AWM-027 c4 470uf 6.3v CEA 647-UPW1C471MPD 470 16 $0.34
AWM-027 c5 100uF 16v CEA 647-UPW1V101MPD 100 35 $0.26
AWM-027 c6 4.7uF 50v CEA 647-UPW1H4R7MDD 4.7 50 $0.12

power supply
AWR-011 c6 100uF 50v CEA 647-UPW1H101MPD 100 50 $0.22
AWR-011 c7 100uF 50v CEA 647-UPW1H101MPD 100 50 $0.22
AWR-011 c9 220uF 35v CEA 647-UPW1V221MPD 220 35 $0.22
AWR-011 c10 220uF 16v CEA 647-UPW1V221MPD 220 35 $0.22
AWR-011 c11 220uF 16v CEA 647-UPW1V221MPD 220 35 $0.22



study the manual until the stuff above starts to meke sense (al least for finding it in the unit - not what it does).

BOM tool text block:
647-UVZ1J682MRD
647-UVZ1J682MRD
647-UPW2A102MHD
647-UPW1A221MED
647-UPW1E331MPD6
647-UPW1J221MPD6


647-UPW1V220MDD
647-UPW1V220MDD
647-UPW1H4R7MDD
647-UPW1H4R7MDD
647-UPW1H100MDD
647-UPW1H100MDD
647-UPW1V221MPD


598-DSF050J474
647-UPW1H4R7MDD
647-UPW1H010MDD
647-UPW1H4R7MDD
647-UPW1H010MDD
647-UPW1V101MPD
647-UPW1H100MDD
598-DSF050J474
647-UPW1H100MDD
598-DSF050J474
647-UPW1H4R7MDD
647-UKL1H3R3KDDANA
647-UKL1H3R3KDDANA
647-UPW1H010MDD
598-DSF050J474
647-UPW1V101MPD
647-UKL1H2R2MDDANA
647-UKL1H2R2MDDANA
647-UPW1E470MDD


647-UPW1H470MED
647-UPW1H470MED
647-UKL1H2R2MDDANA
647-UKL1H2R2MDDANA
647-UPW1E470MDD
647-UPW1E470MDD
647-UKL1H2R2MDDANA
647-UKL1H2R2MDDANA
647-UKL1H2R2MDDANA
647-UKL1H2R2MDDANA
647-UPW1A101MDD
647-UPW1A101MDD
647-UPW1H470MED
647-UPW1H470MED


647-UPW1V220MDD
647-UPW1V220MDD
647-UPW1A221MED
647-UPW1A221MED
647-UPW1H101MPD
647-UPW1H101MPD


647-UPW1C471MPD
647-UPW1C471MPD
647-UPW1V101MPD
647-UPW1H4R7MDD


647-UPW1H101MPD
647-UPW1H101MPD
647-UPW1V221MPD
647-UPW1V221MPD
647-UPW1V221MPD

Mark, Thank you so much for your detailed response and time! You couldnt describe to me where the amplifier PC board is could you?
Thanks again!

Or if you could tell me where I can find the 4 transistors on the amplifier PC card and the 4 on the AF card would be absolulty greatly appreciated!
Thanks again!

You need to study the service manual (just start reading it) with respect to the parts list I posted, and locate those first, Just be able to point at them.

You NEED to learn to be able to unearth the information contained in the service manual as to board and parts identification. once you can find them..

english name of board
AAA-NNN <<< designation for board (A = alphabet, N=number)
An <<<component identifier


ah HAH, my list is incomplete. it does NOT contain Cx (c1, c2. c45 etc..) designations...

Qx is transistors.

I WILL tell you which transistors, and what to replace them with when I have TIME to generate that information. I just blew unexpected time adding the cx designations. Not your fault, but time is finite... you have studying to do...

once you can FIND a part, then you need to learn about polarity for (most) capacitors, and lead identification (emitter. collector, base) for transistors, and the ONLY way (of the 6 ways some can be installed, 5 wrong.... ) to correctly insert it.

Mark, You are an absolute star! I am currently studying the manual and almost getting there in relating it to the amplifier itself annoying, lots of the parts are so hard to reach in this amplifier! my first project is a bigish one!
Thankyou for taking out a lot of your time to do this! Thanks so much!

Try starting on a SX-1010 or a QX-9900!!! The 727 should be a snap! The boards all have standoff's on the corners and the middle that the boards snap on to. There should be enough slack in the wires(once you remove the cinch wire) to lift the boards off and let them hang while removing the boards. DON'T REMOVE WIRES FROM THE POSTS THEY ARE WRAPPED TO. They are stronger than solder joints electrically.

1.) Do one board at a time. Start with the Power supply, if it's not putting out correct voltages, nothing will work correctly. Once you get the powersupply working corectly, test the unit, and move on to the next board. Protection circuit would be a good choice, then the equalizer amp, control amp's and finishing up with the main amp, and output's. As you work down the line, the circuits get more complicated, but you've been working on fairly simple circuits and on up to more complicated.

1a.) On all correspondence, use the board number 1st, then the part #. This will get everyone on the same sheet of music (so to speak). Pictures are worth a lot also. If you get stuck, post some pictures also.

2.) Double and triple check polarity of the new CAPACITORS compared to the board. Identify the NEGATIVE (-) side of the cap on the board and MARK THE BOARD on that side! When you install the new part, identify the negative side and match it up.

3.) Some of the replacement transistors will have a different orientation, Left to Right, than that of the old one. If the old one is ecb and the new is ebc you need to be able to identify the orientation on the board correctly and adjust the leads on the new transistor accordingly.

4.) TAKE IT SLOW! Rushing can and WILL hurt you, and damage the 727. If you're not sure of something STOP, ASK THE QUESTION, and wait for the answer. You may get lucky and have it that day, on the other hand, it may be 2-3 days. Don't get anxious and rush it. We want you to be able to start it up and have it RUN CORRECTLY the 1st time, with you in one piece.

5.) Mark is in the running for ONE OF THE TOP TWO PIONEER TECH's here. Listen and pay attention to him. Don't get ahead of him. He's methodical, invariably accurate (even off the top of his head is 99% correct) and is a hell of a lot more patient than a lot of us. When Mark gives you a parts list, he's personnally vetted it for availability, use in a particular position(transistors), and has used these parts in equipment he builds for others. The parts are reliable, heavily overbuilt compared to the originals, and will last a lifetime if installed correctly. If/when it gets to the point where I can't do my own gear anymore, Mark is at the TOP OF MY LIST, and only one or two others are on it and they are all AK'er's.

I've seen Mark take a guy who couldn't find his arse with both hands in a lit room and a 10 man working party, and guide him thru an overhaul of a SX-1010 to a succesful conclusion. IIRC it took 6 months but the final result was worth it to the guy, Mark, and the rest of us.

Stay on the manual. Read it again and again until the pictures, board numbers and such are 2nd nature. You'll get it eventually.

Larry

Later model service manuals improved greatly, with free downloads, reading a 737, 750 and 880 manual will all contribute to understanding.

Cant explain, how greatful I am to all of you, you have trully been amazingly supportive and helpful. Resoration will start soon and pictures (maybe even in a minute will be taken and up) will follow shortly of pre resto.
Thanks very much!
Rob.