That's What I did with mine. Lay a towel on the Tuner box 1st. Disconnect the STV-3 from the heatsink 1st and lay it out straight CAREFULLY across the board.
SX-939 worth the effort?
- Thread starter SpinninAgain
- Start date
Larry, thank you for the instruction. Are those STV-3H diodes irreplaceable if it breaks?
I have attached the pdf files of parts list I am using. It is downloaded from some thread in AK. Please have a look at the power amplifier section to check it is fine.
No but just do not break one and you will never have to look for one. when i see one I put glue on the leads where they enter the body to secure them.
Larry, I will be very cautious.
There are two 3.3K 2W metal oxide resistors with each of the filter capacitors. During taking out the old capacitor lead of one of the resistors completely broke. Just want to make sure that I have to absolutely use the resistor with the each of the capacitor and it has to be 3.3K Ohm 2W or I can skip it.
Thanks
I have some 2.7K 3W Metal Film resistors. Can I use it?
USE THE 3.3k 2W. These are bleed resistors upon shutdown. You want it to shut down and bleed off voltage at a certain rate. Lower than normal value and it can act like a short for the caps. The original resistors are probably 5% High & low. The value could conceivably be anywhere from 3,135Ω (<5%) to 3465Ω(>5%).
The list is an OLD ONE. The ECQ's are no longer available. and a few of the electrolytics are NLA in that configuration. There are replacements of the same basic model. the below list in the link is basically the same list that Zebulon1 uses now. It's been vetted also by Mark the Fixer and MattSD. I'd use this over your very old list.
https://audiokarma.org/forums/index.php?threads/sx-1010-rebuild-bom-help.748841/ POST #5
The list is an OLD ONE. The ECQ's are no longer available. and a few of the electrolytics are NLA in that configuration. There are replacements of the same basic model. the below list in the link is basically the same list that Zebulon1 uses now. It's been vetted also by Mark the Fixer and MattSD. I'd use this over your very old list.
https://audiokarma.org/forums/index.php?threads/sx-1010-rebuild-bom-help.748841/ POST #5
Larry, thanks for the updated list. I should have wait for your reply regarding resistor with capacitor!! I put the 2.7K 3w resistors with cap and the sound become very low and distorted and in one channel both through speakers and headphone. I took out the jumpers check the main amp with pre out from another amp and it is running fine! Then take out the pre-out of sx1010 to the other amp there is no sound at all. I took the voltage readings of different boards and it looks like below. As before manual values are in parentheses.
Power supply
Pin 8 = 13.4V (13.4)
Pin 9 = -12.8V (-13)
Pin 10 = -56.6V (-56)
Pin 11 = -23.1V (-24)
Pin 12 = 0 (no value in manual)
Pin 13 = 34.1V (35)
Pin 14 = 55.9V (56)
Pin 15 = 25.4V (24)
Protection board
Pin 2 = -12.99V (-13)
Pin 9 = 7.91 (no value in manual)
Pin 11 = 34V (35)
Pin 12 = 7.88 VAC (7.5)
Control amp
Pin 1 = -23 V (-24)
Pin 3 = 25.3V (24)
Pin 10 = 25.3 (24)
Pin 12 = -23V (-24)
Power Amp
Pin 8 and 9 = 56.6V (55V)
Pin 11 and 12 = -56.5 V (-55V)
Do you see anything to be concerned about pin voltages? Before change big capacitors I replaced the heat sink transistors of PS board with right replacement and receiver was working fine. Before checking anything else should I change the resistors in the capacitor to the right value and wattage? The voltages across the capacitors are 55V.
Power supply
Pin 8 = 13.4V (13.4)
Pin 9 = -12.8V (-13)
Pin 10 = -56.6V (-56)
Pin 11 = -23.1V (-24)
Pin 12 = 0 (no value in manual)
Pin 13 = 34.1V (35)
Pin 14 = 55.9V (56)
Pin 15 = 25.4V (24)
Protection board
Pin 2 = -12.99V (-13)
Pin 9 = 7.91 (no value in manual)
Pin 11 = 34V (35)
Pin 12 = 7.88 VAC (7.5)
Control amp
Pin 1 = -23 V (-24)
Pin 3 = 25.3V (24)
Pin 10 = 25.3 (24)
Pin 12 = -23V (-24)
Power Amp
Pin 8 and 9 = 56.6V (55V)
Pin 11 and 12 = -56.5 V (-55V)
Do you see anything to be concerned about pin voltages? Before change big capacitors I replaced the heat sink transistors of PS board with right replacement and receiver was working fine. Before checking anything else should I change the resistors in the capacitor to the right value and wattage? The voltages across the capacitors are 55V.
Voltages are ok. ALL OF THEM! What you're seeing there is the difference between your Wall socket input voltage and a regulated, calibrated test stand input voltage. Nothing to worry about. The amp is running fine according to your post, which means the circuits (main amp) fed from the Main filter caps are ok. The fuse did it's job as it was designed to do.
The lack of sound from the preamp side could be anything between the input jacks and the PRE OUT jacks. EQ amp(phono), switching boards (very likely and problematic), tone control board. If the source you are using is a line level source and it's plugged in to AUX, try it on any other source jack on the back, EXCEPTING PHONO. Switch to that source on the front and try it again. Actually, do all sources and note results, and post them here. Clean the switches AGAIN. Like I said when you were doing the 939, you may have to tearr them apart and physically clean the contacts.
The lack of sound from the preamp side could be anything between the input jacks and the PRE OUT jacks. EQ amp(phono), switching boards (very likely and problematic), tone control board. If the source you are using is a line level source and it's plugged in to AUX, try it on any other source jack on the back, EXCEPTING PHONO. Switch to that source on the front and try it again. Actually, do all sources and note results, and post them here. Clean the switches AGAIN. Like I said when you were doing the 939, you may have to tearr them apart and physically clean the contacts.
Larry, today morning I switched it on, the right channel is clear and perfect. Left channel is dead quite.
With jumpers off taking pre out to marantz 2265 same results left is dead quite, right is perfect.
I have extensively cleaned all switches with tons of D5 same result. Left channel is dead quite if I touch solder parts of right channel I get hum in right speaker but if I touch left solder side of preamp no hum no noise to left speaker. just super quite.
I get some hum or noise in left speaker only when I touch left Pre Out jack connection solder at the back.
Again, both of the channel were working fine before installing filter capacitor .
This is happening with all input sources, aux, tape1, tape2, phono. As I told you main amp is fine in both channels when I use Marantz 2265 as preamp.
I have checked the equalizer amp pin's voltage today
Pin 1= -23V, manual = -24V
Pin 3= 0.0V, manual = +24V (is manual correct?)
Pin 15 = -23V, manual = no value given
all other pins shows 0.0V reading
Please help!
Thanks
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SOLVED PRE-AMP PROBLEM AND CREATED MAIN AMP PROBLEM!!! HERE IS THE STORY
Found the culprit for left channel pre-amp which was the broken output wire at pin 7 and in excitement connected that wire to pin 8 which is also in left channel preamp and switched on found again only right channel is working (which normal as I connected to wrong pin) amp runs few minutes and after I found it is in wrong pin I switched it of and connected to write pin 7. Switched on the amp and I found only left speaker is running this time not right speaker. I checked with head phone got sound in both channel. Used sx-1010 as pre amp to marantz 2265 both channel is working excellent. Used marantz 2265 as pre amp and found only left main amp of 1010 is working not the right side one. I have no clue why right main amp as my connection was wrong in left pre-amp channel!!
I did not yet touch the main amp. It would be great if you please give me some advice where to look at first?
Pins 1 & 8 are the only POWER (Voltage) leads for the EQ Board. Pin 1 according to the schematic, is -24V, while Pin 8 is +24V. ALL VOLTAGES BELOW ARE DC Referenced to Chassis Ground.
Pin1 (EQ BOARD) is fed from Pin 15 of the POWER SUPPLY. -24VDC
Pin8 (EQ Board) is fed from Pin 11 ofthe POWER SUPPLY. +24VDC
Pin 15 of the power supply ALSO FEEDS Pins 3 and 10 of the control Amp ASSY (AWG-027)
Pin 11 of the power supply ALSO FEEDS Pins 1 and 12 of the Control Amp ASSY (AWG-027)
Check the POWER SUPPLY PINS 11 & 15
Check the CONTROL BOARD PINS 1, 3, 10, 12 for +24v or -24V. Referenced to Chassis Ground.
Repair Power supply or leads to EQ and Control boards.
Pin1 (EQ BOARD) is fed from Pin 15 of the POWER SUPPLY. -24VDC
Pin8 (EQ Board) is fed from Pin 11 ofthe POWER SUPPLY. +24VDC
Pin 15 of the power supply ALSO FEEDS Pins 3 and 10 of the control Amp ASSY (AWG-027)
Pin 11 of the power supply ALSO FEEDS Pins 1 and 12 of the Control Amp ASSY (AWG-027)
Check the POWER SUPPLY PINS 11 & 15
Check the CONTROL BOARD PINS 1, 3, 10, 12 for +24v or -24V. Referenced to Chassis Ground.
Repair Power supply or leads to EQ and Control boards.
Post's crossed. When you describe problems as above, it helps to use the BOARD ID NUMBER. (ie: AWG-027 = Control Amp). Pin 8 on the AWG-027 is the ground for the board.
As for the AMP. No clue. But it wouldn't be out of sorts to use the marantz, a RCA Patch cord, and a .01uf 600v film cap on the center lug of the patch cable as a Signal Tracer. Plug in to the Marantz AUX and start listening to differences between L&R components starting at the output of the drivers and work your way back to the inputs. If you get sound on one side of a component and not on the other, usually you found the culprit.
Did you check all of the speaker positions (A-B-C?), Also the relay may be carboned up on the one side and not letting signal thru. Put your meter on the left output's and check it against the right side. If it doesn't match, either the outputs aren't getting a signal or the relay isn't getting the signal thru. Check on both sides of the relay.
As for the AMP. No clue. But it wouldn't be out of sorts to use the marantz, a RCA Patch cord, and a .01uf 600v film cap on the center lug of the patch cable as a Signal Tracer. Plug in to the Marantz AUX and start listening to differences between L&R components starting at the output of the drivers and work your way back to the inputs. If you get sound on one side of a component and not on the other, usually you found the culprit.
Did you check all of the speaker positions (A-B-C?), Also the relay may be carboned up on the one side and not letting signal thru. Put your meter on the left output's and check it against the right side. If it doesn't match, either the outputs aren't getting a signal or the relay isn't getting the signal thru. Check on both sides of the relay.
One more info: I measure the voltages on Pin 8.9 on main amp it is now -41 V according manual should be -55V and yesterday when main amp was working fine it was -56v
voltage between pin 14 and 16 one board stady at 23.5 mV and other board is fluctuating from 5 mV to 70mV
voltage between pin 14 and 16 one board stady at 23.5 mV and other board is fluctuating from 5 mV to 70mV
Larry to minimize the confusion here is the current status
1. Both channels of Preamp is working fine with all inputs. So I think Board AWG-027 is fine. I checked it with marantz 2265 using as main amp and sx-1010 as preamp as well as with headphone connected to sx-1010. Both channels are working fine in both the cases.
2. Problem is now with main amp right channel no sound in right channel. Left channel I am getting sound. I did not wotk on main amp board AWH-032. I checked the voltages at Pin 8, 9, 11,12
In both of the boards it is now -41V on pin 8 & 9 and +41V in pin 11 & 12. According to manual it should be -55V and +55V respectively. Yesterday when the main amp was working fine it gives the value -56V and +56V respectively which is more reasonable and correct. Today I also measure the bias voltage between pin 14 and 16 in both boards. One board gives a steady value of -24 mV and in other board it is fluctuating fast anywhere between 5mV to 70mV (that's probably the channel which is not working. it is in the left if look from front side of amp).
Voltages back up to spec????
Yes, voltages are fine now. I was trying to get access to the back of main amp board but couldn't. After lifting the heatsink, to get access to the back of the board i need to take out the black metal holder to which the board is attached by screws.
Am I right?
The brackets are attached to the chassis on both sides of the boards by 2 screws. Remove the screws and the board pulls straight up.