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Static / No Audio from Pioneer SX-727

A

Amanda123

New Member
Hello!

I am new to AudioKarma, and relatively new to vintage audio equipment, so I would appreciate any insight you all might be able to offer.

I have a problem with static and popping / no audio in my system. I've isolated the problem to the receiver, which is a Pioneer SX-727. The receiver was professionally cleaned/serviced in January 2016.

My problem is especially frustrating because it is extremely inconsistent. Sometimes my system will play perfectly for a short period of time (10-30 minutes) before popping out and going silent. Sometimes it will play audio with static and popping coming from the left channel only. Sometimes it will only output static and popping that cannot be isolated to a particular channel. Sometimes I'll turn it on and it won't put out any noise at all.

The static and popping does not change in volume when I adjust the volume on the receiver. When it can be isolated, it is located in the left channel. When present, the static and popping persists on all channels (A,B,C, and headphones). I don't know that it makes any difference, but the static/popping is still the same whether I use phono 1 or phono 2 as my input.

Any ideas about what's wrong with it would be appreciated. Also, I don't trust myself to repair it on my own, so if you have any idea how much it would cost to repair, that would be good to know. I'm pretty attached to this receiver, but if it's just going to be a money pit I might move on to another receiver.

Thanks in advance for your help!
Amanda
 
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Amanda; The 727 is a great 1st piece, and does require a bit of TLC now that it's in it's advanced age. There will be parts that need replacement (if not done already), and occasional cleanings. The fix on this is fairly simple but correct terminology will help you understand what is going on inside. You don't get rid of a car because the brakes squeal (unless it's a Tribant or a YUGO)

CHANNELS are LEFT AND RIGHT. ONLY 2 as this is strictly a STEREO unit. (with optional 4 channel units it can be run in quad, but its a mish mash of gear).
CHANNEL OUTPUT's (L & R) are switched between 3 sets of speakers so it's really no difference which speaker switch it runs thru as long as it will run thru all 3 (speaker switches are good).
SOURCES are AM,FM, PHONO, AUX, TAPE MONITOR (1 or 1 & 2 depending on model). Depending on where the source switch is set will determine what boards are connected to complete the circuit between the original source (phonograph, tape deck , radio, Cd player or other on AUX) and the speakers.

Do some light trouble shooting. LEAVE the SPKR in "A". Turn on the unit and switch to AM until it drops out the left channel. If it doesn't do it after a reasonable amount of time, then switch to FM (repeat and rinse), Then AUX(use a CD Player) (repeat and rinse), As the Tape Monitor is basically useless without a tape recorder, don't worry about it. If it doesn't do this in ANY of the Sources but PHONO, you need to troubleshoot the phono and receiver. Get a small piece of cloth and some metal cleaner and clean the phono RCA Jacks on the back 1st. Then clean the RCA plug on the end of the cable with DeOxit and a toothbrush (boyfriends or husbands is ok, he won't notice the taste (just kidding). Use an old used toothbrush. Do both ends of both left and right cables. Make sure the connections are tight, also check the wiring on the phono, and the cartridge. If this doesn't resolve the problem, you could have a transistor or a capacitor going bad in either the EQ board (otherwise known as the phono EQ Board), or the preamp board, although the phono board is the problematic if the popping and static is only heard in PHONO. On the 727 PIONEER called it the HEAD amp.

Another thing that it could be is dirty contacts in the switches and pots on the front panel. I would do this 1st as it's the most prevalent problem with Audio gear. These get dirty just from environmental conditions, and can drop signals intermittently. I would clean all of them with Deoxit D-5 and follow up with Faderlube F-5 (Faderlube replaces the lubricant in the pots and switches lost during cleaning....very important). Read this thread .....
http://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/

Guitar-Center carries both locally. About $35.00 for both cans. They should last a few years if doing the 727 cleaning once a year.

I've experienced pot and switch cut out within 6 months of initial cleaning , and just do it again. Think of it as preventive maintenance on your car. Brakes, tires, oil changes, etc. The 727 dates from 1972 to 1974 so it's a fair bet it's probably as old as your parents. As they get older, parts start drying up, breaking down, etc. And it's not just the 727, ALL OF THEM DEGRADE.


Looking at the PHONO EQ board on the 727, there are 6 2sc458 or 2sc871 transistors or a mixture of both. These are notorious for going noisy and or popping / dropping out when warmed up. Replacements are the KSC1845FTA @ mouser for $0.21 ea. If you have a friend that is into electronics and can do soldering with correct leg placement of the transistors, offer a 6 pack of his favorite beverage. Also I would replace the electrolytic capacitors on the board as well if they haven't been already. About $4.00 for all the caps.

Can you take off the bottom and top (#2 phillips screwdriver will do all the screws easily) and take some pictures of the innards. Then we can tell you if it's been worked on. Make sure the pictures are taken with a flash inside or they'll be too dark to see. OR just put it outside and take a few there. Try and minimize glare off the metal if you can, please.
While you have the top and bottom off is a perfect time to clean all the switches and pots.
If you have a work order from the shop photo that also, blanking out the customer information and the shop name. This way we can see what they did and guide you better as to what needs to be done.
 
I have a deadline on Wednesday so I'm not able to do any more troubleshooting until that's passed, but here are the requested photos/documents.
Scan.jpeg File_000 (4).jpeg File_001.jpeg

Thanks for your help!
 
Ok! Now we know it had "Switches and controls CLEANED as best i could". :wtf:
Relay was refurbished???!?!?! You don't refurbish a relay. You either burnish the contacts ONE TIME or replace it.
Wiring and connections refurbished??!?!?!?! :bs: Not that I can see, unless he squirted DeOxit in the connections (and there ain't many on a 727) and put them together and pulled apart to clean them a few times, as most everything is wire-wrapped and or soldered. . You could do the same thing except check it for operation with test gear. Your test gear is your speakers and headphones.

This looks like it's an unmolested SX-727 as it left the factory just from the 2 pics you supplied. It really should have a total recap and trouble prone transistors (2sa725's and 2sc1312, 2sc458) replaced. Thank god it doesn't have the 2sc1451's WHEW!!!! (Those are #1 on the TOP TEN WANTED LIST!)

Electrolytic capacitors generally have a useful life of 20-25 years at the outside, and they can dry out totally to the point where a cap will short and take out other parts. The trouble prone transistors as noted above get noisy, and can drop off on the one side intermittently, or at least cause what I describe as "RICE KRISPIES" .

Parts for a total rebuild would run about $75.-$85 from Mouser or Digikey. Figure about $500-$600 parts and labor for a shop to do this (if you can find one that will do a full rehab.). There are guys on AK that do this as a hobby and generally charge somewhat less, and you get a better job because they know the latest part #'s, and use better Fairchild, or OnSemi transistors from reliable suppliers, and all the upgraded stuff that pioneer included in later models, that should be included in the 727.

Get a can of DeOxit D-5 and a can of DeOxit FADERLUBE F-5. you will need to remove the front panel to gain access to the push button or flip switches. The pots and switches on the boards, will need some dis-assembly, but it's 2 boards and you'll undo the front cover, then each retainer nut on the knob shafts to pull the board out the back. Clean the pots and switches on both boards. (Spray inside, then turn or push in-out or flip up and down 30-40 times each. Then flush for 1-2 seconds with the Faderlube.) Do this for each switch and pot (poteniometer (volume, balance, bass, treble controls). Put it back together, and let it sit for an hour or so to let the carrier in the spray to dry completely. Turn it on and test.

This will rule out dirty switches and pots (1st thing done for intermittent contact). Then if it still does the pop and drop, then we can get into replacing capacitors and transistors. Lot's of help here, and just doing the Headamp (phono EQ) will cost about $8-10. including caps, and transistors. Roll in the DeOxit, and you're still under 1/3 of what the shop charged just for a cleaning. Now to teach you how, or you find a friend who's into electronics.

Larry
 
I have a friend in town who's into electronics so I'm going to try to bribe him to help me out with this endeavor...he's only in town for another week so hopefully we can get it figured out in that time.

I don't have any of the equipment required for electronics repairs, so I have to assemble a shopping list. This is what I can tell that I will need based on your (super helpful!) comments; please let me know if I'm leaving anything out, or if there's something I don't need:
-assorted screwdrivers
-soldering iron
-solder
-solder wick
-solder remover
-voltmeter
-deoxit
-faderlube
-6 2sc458 or 2sc871 transistors for phono board (KSC1845FTA @ mouser)
-various other capacitors and transistors?

Thanks so much for your help :)
 
It is a receiver that is worth the time to fix, but I wouldn't sink $500 into it for a shop to do. I agree with Larry that it is probably the head amp, but I think more inputs go through it than just phono (I could be wrong, but too late tonight to check). I rebuilt the one in my avatar, and if you have some basic skills at soldering you can use the information here to rebuild yours. There are a lot of talented people here like Larry that can pretty much walk you through it. I wrote a thread on my repair if you want to see some of what is involved.
 
This is a nice receiver to get started on. Well worth the DIY effort.
If you have another set, amp,and or pre-amp to test the operation of the separate units:
Separate the set at the "Pre In" and "Main Out" jumpers on the back of the receiver. Use only one section of the receiver checking to see if it's in the amp section or the pre amp assembly. This will isolate the problem if you want to try to get it going quickly.
Most likely it's in the pre amp section as the set still operates and passes audio. Head amp if the problem is only when using the phono.
As Larry says:
Clean the controls first
Check the power supply voltages making sure they are stable. Consider restoring it as it utilizes suspect transistors.
Rebuild the AF Assembly board (AWK-010) getting rid of the old problematic transistors.
Get it working again and then think about restoring it.
You don't have to buy new tooling/equipment, look in used listings for good quality gear. This is key to a fun, easy experience repairing your set.
 
Last edited:
Okay! Initial troubleshooting done.

Audio pops and cuts out on all sources.
Deoxit'd and Faderlubed all pots and switches.
Tested setup after cleaning the receiver; it immediately made a popping noise and then cut out, now there's no audio from any source.

So from what you all have said, I'm guessing it's a problem with the preamp board?

Please let me know how to proceed.

Thanks for your help!
 
Build a DBT (Dim Bulb Tester).
Instructions
Can you hear the protection relay click a moment after switching the set on?
If not, remove the jumpers from the back of the set. see if you can hear the relay click.
If not, you will need to web search the operation of a DMM or read the instructions in the owners manual. There is a certain amount of self training that you need to accomplish.
Check all (4) fuses by removing them and checking for continuity (Checking to see if they are open). One main (F1) and two supply (F3 and F4). One lighting fuse (F2).
If any fuses are blown (Open) do not replace them until you finish the DBT.
Record the power supplies voltages, all are in DC volts. Read DC volts on PS (Power Supply), Pins 2, 5, 6, 7, 14 and 15.
Record the DC voltages on all the protection board pins.
 
Amanda; Suggest you download ALL of the files for the 727 from this site. IT has the owners manual, Service Manual, Schematics (which are in the manual,) Protection circuit supplement, Brochure, and a review from one of the 70's stereo magazines. Just scroll down to the sx-727 and download away.

Larry
 
All manuals are downloaded and I will do the DBT when I have some help. Just to give everyone an update....

My brother, who's my go-to tech person, works out of state but said he'd help me work on the receiver when he's back in town for Christmas. So I'll probably be hitting y'all up for some knowledge around then :)

After I cleaned the pots and switches and let the unit dry for a day or so, everything was working great! I could easily play 2-3 records with no issues. Now on occasion though, after extensive warming up (say 1-2 sides of a record), all audio pops out. This happens on all phonos and speaker a, b, and c. I have to leave the unit alone for a few hours or longer for it to go back to normal.

Please let me know if this information changes your initial assessment of the unit.
 
Doesn't change anything but it does reinforce the transistors and or caps failing due to heat in the head amp board, tone control board, and or preamp board. As it does it in phono in addition to the other sources, I'd be inclined to redo the phono board(HEAD AMP) 1st. Then test and continue on thru each board until the problem is solved. I would also rebuild the POWER SUPPLY BOARD to ensure that all voltages are in spec. Good voltages are important to good operation of the unit.
 
Amanda
Did you ever track the issue down? My 727 is doing Exactly the same thing. Hoping you can point me in the right direction.
 
maxsound. Everything above applies to your unit. Clean the controls 1st with DeOxit and Faderlube. Read "the Idiot's Guide to De-Oxit....Revisited" as linked in an above post. If the problem still exists, remove the PRE-OUT/Main in jumpers, clean both the jumper and RCA Jacks. Leave the jumpers out and turn on and leave on until the unit pops and dies. If it doesn't (you'll hear it in the speakers), then the problem is in either the HEAD AMP or the AF AMP. Connect RCA cables from the PREOUT jacks to the input of another Amp/Receiver and test. If it pops and dies that reinforces the AF AMP AND HEAD AMP.

REBUILD THE POWER SUPPLY COMPLETELY 1st. Clean stable power is mandatory in these units Replace the 2sc458's on all boards, 2sa725's, 2sa726's, 2sc1384's as needed. There is a Parts list for the 727 in this thread http://www.audiokarma.org/forums/index.php?threads/pioneer-recap-lists-sticky-suggestion.457663/. Download the individual transistor replacements datasheets for pin orientation for the replacements. Test and if needed, rinse and repeat on the next board.
 
Thanks for the info.... Will be checking out the links.
larryderouin said:
maxsound. Everything above applies to your unit. Clean the controls 1st with DeOxit and Faderlube. Read "the Idiot's Guide to De-Oxit....Revisited" as linked in an above post. If the problem still exists, remove the PRE-OUT/Main in jumpers, clean both the jumper and RCA Jacks. Leave the jumpers out and turn on and leave on until the unit pops and dies. If it doesn't (you'll hear it in the speakers), then the problem is in either the HEAD AMP or the AF AMP. Connect RCA cables from the PREOUT jacks to the input of another Amp/Receiver and test. If it pops and dies that reinforces the AF AMP AND HEAD AMP.

REBUILD THE POWER SUPPLY COMPLETELY 1st. Clean stable power is mandatory in these units Replace the 2sc458's on all boards, 2sa725's, 2sa726's, 2sc1384's as needed. There is a Parts list for the 727 in this thread http://www.audiokarma.org/forums/index.php?threads/pioneer-recap-lists-sticky-suggestion.457663/. Download the individual transistor replacements datasheets for pin orientation for the replacements. Test and if needed, rinse and repeat on the next
Click to expand...
 
Yeah definitely original inside the only update that has been made is the LED upgrade. It will play perfectly for hours sometimes and then just start static and then kick off and it will come back on after say an hour so that sounds like caps to me also. I have been reading a couple threads on the the protection relay that it could be dirty.
 
I certainly had to fix (replace) the relay on my 828, contacts were burnt. A complete recap and all transistors on the power supply and pro board did it for me.
 
larryderouin said:
maxsound. Everything above applies to your unit. Clean the controls 1st with DeOxit and Faderlube. Read "the Idiot's Guide to De-Oxit....Revisited" as linked in an above post. If the problem still exists, remove the PRE-OUT/Main in jumpers, clean both the jumper and RCA Jacks. Leave the jumpers out and turn on and leave on until the unit pops and dies. If it doesn't (you'll hear it in the speakers), then the problem is in either the HEAD AMP or the AF AMP. Connect RCA cables from the PREOUT jacks to the input of another Amp/Receiver and test. If it pops and dies that reinforces the AF AMP AND HEAD AMP.

REBUILD THE POWER SUPPLY COMPLETELY 1st. Clean stable power is mandatory in these units Replace the 2sc458's on all boards, 2sa725's, 2sa726's, 2sc1384's as needed. There is a Parts list for the 727 in this thread http://www.audiokarma.org/forums/index.php?threads/pioneer-recap-lists-sticky-suggestion.457663/. Download the individual transistor replacements datasheets for pin orientation for the replacements. Test and if needed, rinse and repeat on the next board.
Click to expand...

Pulling this thread back up. I have a SX-727. I’ve recapped the tone board and replaced the 725s and 1312 transistors.

My issue is that…Aux sounds great…like really good and silent when the volume is down.

When I switch to Phono or AM/FM etc there is static/popping, but only in the right channel. If I turn the volume down the static/popping goes disappears…so it would be before the volume control, right? Would rebuilding the head amp solve this you think??
 
slowvinyl said:
Pulling this thread back up. I have a SX-727. I’ve recapped the tone board and replaced the 725s and 1312 transistors.

My issue is that…Aux sounds great…like really good and silent when the volume is down.

When I switch to Phono or AM/FM etc there is static/popping, but only in the right channel. If I turn the volume down the static/popping goes disappears…so it would be before the volume control, right? Would rebuilding the head amp solve this you think??
Click to expand...
Yes. Yes.
 
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