Just finished my S.E.X.
- Thread starter SilverS
- Start date
Well, I would certainly suggest inspecting all the wiring to the headphone jack, the headphone jack, and the wiring that goes from the headphone jack to the speaker terminals. Since a bunch of that is done in twisted pair in which both wires are black, I can see where it would be easy to make a mis-step. When in doubt, of course, use your Ohm meter on each end to make certain that you are working on the same wire.
I could also just be that headphone jack is shot, I probably resoldered the bottom terminal 4-5 times (miswiring/resoldering etc). I'll definantly check the wiring tomorrow though.
Thank you very much to everyone for all the help, I can't tell you how relieved I am to have you all around for advice
Thank you very much to everyone for all the help, I can't tell you how relieved I am to have you all around for advice
Paul Joppa
Moderator
Did you replace the headphone jack to get both channels working?
Here are things I've posted before, not sure if you've done all of them:
>> To start looking for hum and buzz, disconnect everything except the speakers or headphones and turn the volume all the way down. That isolates the electronics from possible external noise sources.
Try to measure the output hum at the speaker terminals, using the lowest AC voltage scale you have. (It may be too low to measure with your meter, but if we get any data it will help figure this out.)
>> A7, B7, C1 and C4 should all be connected to chassis ground by the wire from C1 to safety ground, and you should read nearly zero voltage, AC or DC, at these points. Check wiring and soldering.
>> Your readings at 2, 9, and 10 appear to be AC; the manual gives appropriate DC measurements but not AC. But T9 (connected also to T12) should be at AC ground through the 1000uF capacitorT12 to T15. Check those connections and solder joints, also the orientation of the capacitor. T10 is on the ground buss, ultimately connected to T18 which is screwed to the chassis plate so there should be no voltage, AC or DC at these points. (Are you sure the measurements are volts and not millivolts?)
Here are things I've posted before, not sure if you've done all of them:
>> To start looking for hum and buzz, disconnect everything except the speakers or headphones and turn the volume all the way down. That isolates the electronics from possible external noise sources.
Try to measure the output hum at the speaker terminals, using the lowest AC voltage scale you have. (It may be too low to measure with your meter, but if we get any data it will help figure this out.)
>> A7, B7, C1 and C4 should all be connected to chassis ground by the wire from C1 to safety ground, and you should read nearly zero voltage, AC or DC, at these points. Check wiring and soldering.
>> Your readings at 2, 9, and 10 appear to be AC; the manual gives appropriate DC measurements but not AC. But T9 (connected also to T12) should be at AC ground through the 1000uF capacitorT12 to T15. Check those connections and solder joints, also the orientation of the capacitor. T10 is on the ground buss, ultimately connected to T18 which is screwed to the chassis plate so there should be no voltage, AC or DC at these points. (Are you sure the measurements are volts and not millivolts?)
I just went down to give the amp one more test before going to sleep and its back to only working on the left channel again... This afternoon it transmitted on both channels when I plugged in my earbuds. So could it just be the low impedance of the Grado's that is messing up the transmission? Also, I'll do what you said to test for miss solders tomorrow afternoon and see if I can't get rid of the hum.
I'm wondering if it might be something about the fit of the headphone plugs in the jacks. Maybe check to see if the earbuds/both channels and Grados/one channel situation is consistent. I had a brand new set of cans at the Head Fi meet a couple weekends ago. Halfway through the day they went mono. Cans were fine, amp was fine. Turned out someone had overstressed the 1/8" to 1/4" headphone plug adapter and shorted it to mono.
Grainger49
New member
I can't help but wonder if the Grados work on other headphone outputs? The lack of Left channel might be the Grados. Then again it might not be the Grados. I just have to ask.
I believe I have found the problem causing the hum:
T21 ~ 143V (supposed to be 183V)
T22 ~ 143V (supposed to be 183V)
T29 ~ -14V (supposed to be -17V)
T12 ~ -14V (supposed to be -17V)
So, I should just check all my solder connections to the terminals on the B side or could it just be that power isn't properly getting to that side? Sorry for asking yet again but I don't know where to start looking.
As for the left channel only transmission, it's probably just that the Grado's plug and the headphone jack aren't playing nice, I'll have a new jack by the end of the week though so that should fix any issues there.
T21 ~ 143V (supposed to be 183V)
T22 ~ 143V (supposed to be 183V)
T29 ~ -14V (supposed to be -17V)
T12 ~ -14V (supposed to be -17V)
So, I should just check all my solder connections to the terminals on the B side or could it just be that power isn't properly getting to that side? Sorry for asking yet again but I don't know where to start looking.
As for the left channel only transmission, it's probably just that the Grado's plug and the headphone jack aren't playing nice, I'll have a new jack by the end of the week though so that should fix any issues there.
I want to piggyback on this thread as I am having the same issue... sort of. I just finished my SEX kit as well and when playing my ipod w/ Grado RS-2 headphones plugged in, the amp seems to work fine out of both channels. However, when I plug in my speakers, the right channel is not working.
I troubleshot to ensure that the speakers and cabling were not the issue, and they were not
So, I retraced all of the steps, paying very careful attention to the wiring from the headphone jack to the binding posts, which seems to be correct. I triple checked my solder joints which all seem to be good (I even moved one wire from the twisted teflon pair of wires to the outside terminal of the bottom pair of terminals on the headphone jack, as the inside terminal was crowded and made me suspicious that that terminal may have been a bad solder joint with how crowded it was). However, the problem remains the same.
I'm at a loss as to what else I can try, so I'm going to list a couple of inconsistencies that I found with the resistance/ voltage checks to see if someone can make sense of what might be going on...
RESISTANCE
19, 39 = 5.5K ohms at minimum volume (should be at 0 ohms w/ volume at minimum)
A4, B4 = 6K ohms at minimum volume (should be at 0 ohms w/ volume at minimum)
VOLTAGE
PT terminal 1= 0 VAC (should be at 120 VAC)
PT terminal 7= 188 VAC (should be at 0 VAC)
PT terminal 10= 188 VAC (should be at 0 VAC)
*Terminals 6 and 9 on PT are at 188 VAC as well.
I troubleshot to ensure that the speakers and cabling were not the issue, and they were not
So, I retraced all of the steps, paying very careful attention to the wiring from the headphone jack to the binding posts, which seems to be correct. I triple checked my solder joints which all seem to be good (I even moved one wire from the twisted teflon pair of wires to the outside terminal of the bottom pair of terminals on the headphone jack, as the inside terminal was crowded and made me suspicious that that terminal may have been a bad solder joint with how crowded it was). However, the problem remains the same.
I'm at a loss as to what else I can try, so I'm going to list a couple of inconsistencies that I found with the resistance/ voltage checks to see if someone can make sense of what might be going on...
RESISTANCE
19, 39 = 5.5K ohms at minimum volume (should be at 0 ohms w/ volume at minimum)
A4, B4 = 6K ohms at minimum volume (should be at 0 ohms w/ volume at minimum)
VOLTAGE
PT terminal 1= 0 VAC (should be at 120 VAC)
PT terminal 7= 188 VAC (should be at 0 VAC)
PT terminal 10= 188 VAC (should be at 0 VAC)
*Terminals 6 and 9 on PT are at 188 VAC as well.
Paul Joppa
Moderator
SilverS, those voltages are low, but not a lot low. Makes me wonder if your power line voltage is low, or if your meter is reading accurately. Let us know when you've replaced the headphone jack, I still suspect some internal damage for the intermittently missing channel. The fact that it once worked indicates the electronic portion is wired correctly.
cmason84, the voltages on the power transformer 6=7=9=10 do vary with different meters, so if the voltages at the tube sockets are correct you can ignore those power transformer measurements.
The zero volts at power transformer terminal 1 indicates you have the neutral connected to that terminal, not the hot. Check your wiring carefully, then if necessary check your house wiring - it may be that your power is wired incorrectly. (I am assuming you have true 3-wire sockets with a good safety ground.)
You say you get both channels on the headphones - first thing is to be sure it's really both channels, and not one channel in both ear pieces. The latter would indicate a bad connection between the headphone plug and the jack, which might be a mechanical problem rather than an electrical one. If you do have both channels in the phones, then the problem is in the wiring from transformer to jack and speaker connectors.
cmason84, the voltages on the power transformer 6=7=9=10 do vary with different meters, so if the voltages at the tube sockets are correct you can ignore those power transformer measurements.
The zero volts at power transformer terminal 1 indicates you have the neutral connected to that terminal, not the hot. Check your wiring carefully, then if necessary check your house wiring - it may be that your power is wired incorrectly. (I am assuming you have true 3-wire sockets with a good safety ground.)
You say you get both channels on the headphones - first thing is to be sure it's really both channels, and not one channel in both ear pieces. The latter would indicate a bad connection between the headphone plug and the jack, which might be a mechanical problem rather than an electrical one. If you do have both channels in the phones, then the problem is in the wiring from transformer to jack and speaker connectors.
Thanks Paul, all is well now.
The power was wired correctly (voltage check sheet lists incorrect voltages for terminal 1 and terminal 2 on PT; they're switched).
The problem was the wiring from the jack to the binding posts. When the directions said to solder the wires to the red and black binding posts, I was looking at the red and black on the underside of the chassis instead of the topside of the chassis. All I had to do was swap the wires at the two inside binding posts and I'm getting sound from both of my speakers now.
The power was wired correctly (voltage check sheet lists incorrect voltages for terminal 1 and terminal 2 on PT; they're switched).
The problem was the wiring from the jack to the binding posts. When the directions said to solder the wires to the red and black binding posts, I was looking at the red and black on the underside of the chassis instead of the topside of the chassis. All I had to do was swap the wires at the two inside binding posts and I'm getting sound from both of my speakers now.
I have already replaced the headphone jack, which fixed the hum. As for it transmitting on both channels I checked again, and it turns out it was just transmitting a the left single to both sides. So even at the time when I posted to worked on both, it really was just a mono signal being transmitted on both sides.
Paul Joppa
Moderator
Good, that's progress!
OK, we'll do some signal tracing, starting at the input and output. First, find a song that is fairly consistently loud. Unplug the source from the SEX amps and measure the AC voltage at the RCA plugs coming from the source. You should see a fraction of a volt on each channel - I'm just making sure your meter can measure a signal that small, and that both channels are working on the source.
Now it's the right channel that's dead. That would be hhe "A" tube which is on the left when the amp is upside down, correct?
Then plug that source into the right channel (the dead one) and measure the voltage at T19, with the amp still turned off. You should see the same voltage if the volume control is all the way up. Then check at the tube socket pin 4 - that's the grid, input to the tube, and should be the same as T19.
If the signal has gotten that far, then we'll check the other end. Measure the AC voltage at T20, where the output transformer brown wire is connected. Do this with the amp turned on. You should see a much greater voltage. If it's there, check at T5 which is the transformer output - should be less again, maybe a volt or two.
OK, we'll do some signal tracing, starting at the input and output. First, find a song that is fairly consistently loud. Unplug the source from the SEX amps and measure the AC voltage at the RCA plugs coming from the source. You should see a fraction of a volt on each channel - I'm just making sure your meter can measure a signal that small, and that both channels are working on the source.
Now it's the right channel that's dead. That would be hhe "A" tube which is on the left when the amp is upside down, correct?
Then plug that source into the right channel (the dead one) and measure the voltage at T19, with the amp still turned off. You should see the same voltage if the volume control is all the way up. Then check at the tube socket pin 4 - that's the grid, input to the tube, and should be the same as T19.
If the signal has gotten that far, then we'll check the other end. Measure the AC voltage at T20, where the output transformer brown wire is connected. Do this with the amp turned on. You should see a much greater voltage. If it's there, check at T5 which is the transformer output - should be less again, maybe a volt or two.
I'm really confused right now. I just tried testing those terminals and when I had the negative lead connected to the ground wire from the power socket, and the red one in hand touching nothing, it was reading 1-1.5V~. Then when I connect the positive lead to terminal 19 it drops to .0003V~
Also I had a question about terminal 19. I recall when soldering resistors to those terminals, the guide called for the B side to have the resistor soldered to the lower hole of terminal 19, while the A side should have it soldered to the top hole of terminal 19. Is this a mistake in the guide? And perhaps why I'm not getting a signal from the right channel?
Also, considering speakers are picking up the right channel wouldn't that mean the terminals around the tubes and the tubes are all working properly?
Also I had a question about terminal 19. I recall when soldering resistors to those terminals, the guide called for the B side to have the resistor soldered to the lower hole of terminal 19, while the A side should have it soldered to the top hole of terminal 19. Is this a mistake in the guide? And perhaps why I'm not getting a signal from the right channel?
Also, considering speakers are picking up the right channel wouldn't that mean the terminals around the tubes and the tubes are all working properly?
Paul Joppa
Moderator
When the meter lead is not touching anything, it acts like an antenna and picks up whatever electrical fields are around. Once it is connected to something, the low impedance of that something (less than the 10,000,000 ohms of the meter input anyhow!) shorts out the antenna function, leaving the measured voltage.
The top and bottom holes of the terminals are all the same metal, so they are all connected together. I'd call it an "inconsistency" in the manual ... sounds better that way. :^)
You said previously "As for it transmitting on both channels I checked again, and it turns out it was just transmitting a the left single to both sides." Now you say the right channel is working with speakers. So I don't know what the real problem is anymore. If both channels work with speakers but not with headphones, then the headphone jack/transformer output/speaker terminal wiring is in error somewhere.
The top and bottom holes of the terminals are all the same metal, so they are all connected together. I'd call it an "inconsistency" in the manual ... sounds better that way. :^)
You said previously "As for it transmitting on both channels I checked again, and it turns out it was just transmitting a the left single to both sides." Now you say the right channel is working with speakers. So I don't know what the real problem is anymore. If both channels work with speakers but not with headphones, then the headphone jack/transformer output/speaker terminal wiring is in error somewhere.
Yeah I can see where the confusion is coming from. Let me sum everything up to a final conclusion:
The speakers since day 1 of the issues have only been transmitting on the right channel.
The Headphones since day 1 have only been truly transmitting on the left channel (when I said they were transmitting both it was just the left channel being sent through both sides for some reason)
So where do we go from here?
The speakers since day 1 of the issues have only been transmitting on the right channel.
The Headphones since day 1 have only been truly transmitting on the left channel (when I said they were transmitting both it was just the left channel being sent through both sides for some reason)
So where do we go from here?
Paul Joppa
Moderator
Thanks, that makes better sense now - guess I just got lost in teh many posts.
OK, the amp is generating output on both channels. The output (autoformer secondary connections are T5 and T25 for the hot lead (the black primary and white secondary are both connected here. The cold side of the outputs are the secondary black wires, connected at T10 and T30.
The hot outputs (T5 and T25) go to the headphone jack, and from there to the hot (red) speaker binding post on the top side for that channel. You may have to trace the physical wires, because the output transformer secondary winding has a fraction of an ohm resistance, making it hard to tell with a meter which speaker terminal is connected directly, and which is connected through the winding. Also, the speaker terminals in the manual are coded red for one channel, black for the other channel - but on top there's a red and a black for each channel - it's the binding post color, not the base color referred to. I'm not sure if the current speaker terminals are identical to what's in the manual now, so I can't be certain this is clear, but this seems to be the most likely place for a wiring error.
Similarly the cold outputs go to the headphone jack (lowest terminals, which are connected) and from there to the black speaker binding posts.
It might help to first unsolder the wire that goes from T5 to the headphone jack, and also the one at T25. In both cases, these are one wire of a twisted pair. Then those wires can be traced with an ohmmeter, as can the cold wires (the other wire of the twisted pairs).
OK, the amp is generating output on both channels. The output (autoformer secondary connections are T5 and T25 for the hot lead (the black primary and white secondary are both connected here. The cold side of the outputs are the secondary black wires, connected at T10 and T30.
The hot outputs (T5 and T25) go to the headphone jack, and from there to the hot (red) speaker binding post on the top side for that channel. You may have to trace the physical wires, because the output transformer secondary winding has a fraction of an ohm resistance, making it hard to tell with a meter which speaker terminal is connected directly, and which is connected through the winding. Also, the speaker terminals in the manual are coded red for one channel, black for the other channel - but on top there's a red and a black for each channel - it's the binding post color, not the base color referred to. I'm not sure if the current speaker terminals are identical to what's in the manual now, so I can't be certain this is clear, but this seems to be the most likely place for a wiring error.
Similarly the cold outputs go to the headphone jack (lowest terminals, which are connected) and from there to the black speaker binding posts.
It might help to first unsolder the wire that goes from T5 to the headphone jack, and also the one at T25. In both cases, these are one wire of a twisted pair. Then those wires can be traced with an ohmmeter, as can the cold wires (the other wire of the twisted pairs).
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