Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: kill_surf_city on July 07, 2022, 04:43:48 PM
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I just finished my build with SUTs installed and i rechecked the voltages and everything was good. I had a very low hum in both channels, but that may or may not be an issue with my main amp. I did some check of cords and such, then when i turned the amp back on, the left channel was out - well turns out it's just out of balance. I'm getting sound out of it but the right side is MUCH louder. My LEDs are still coming on but I see the ones on the top of the C4S board near IB aren't quite as bright. I measured voltages
IA - 215v
IB - 118.8v
OA -158.4v
OB - 115.4v
OC - 97.1v
OD - 98.1v
OkA - 98.1v
OkB - 97.9v
OkC - 1.235v
OkD - 1.523v
Where should I look for a problem?
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I would disconnect the blue wires feeding the "I" terminals on the front C4S board and redo the voltage checks on the C4S shunt regulator board above the 12AU7 socket.
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I would disconnect the blue wires feeding the "I" terminals on the front C4S board and redo the voltage checks on the C4S shunt regulator board above the 12AU7 socket.
Okay side B is reading as 216v
side A of the board is reading 188.5v
any specific joints i should check?
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damn it. i was doing some probing to try and find the source of the issue, and something sparked on one of the 100kohmJ parts and now two of the LEDs on the A side are out.....but I am getting 249v on the side that was lower. Not sure what to do now.
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Post IA, IB, OA, OB, KregA, KregB voltages. There was and still is something wrong with the power supply regulator that's built on the 12AU7 socket (which I why we have you test it early in the build), so this portion of the circuit needs to be working properly before moving along to the rest.
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Post IA, IB, OA, OB, KregA, KregB voltages. There was and still is something wrong with the power supply regulator that's built on the 12AU7 socket (which I why we have you test it early in the build), so this portion of the circuit needs to be working properly before moving along to the rest.
IA - 256v
IB - 253v
OA - 250v
OB - 217v
KregA - 183.6v (this value never seems to pick a number, it floats around this range
KregB - 1.95v
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KregA definitely shouldn't be going that high. Are you sure that's not in mV instead of V?
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KregA definitely shouldn't be going that high. Are you sure that's not in mV instead of V?
ah sorry, i meant mV on that one. just tested it again and its at 179.3mV
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Something like this could be a shorted 431 regulator, though typically we don't see them short in that manner, or possibly a jumper on the C4S board above that socket that isn't wired properly.
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Something like this could be a shorted 431 regulator, though typically we don't see them short in that manner, or possibly a jumper on the C4S board above that socket that isn't wired properly.
Sorry, I don't understand. The C4S board was disconnected from the IA/IB leads when I ran this test. Which one is regulator is 431?
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Something like this could be a shorted 431 regulator, though typically we don't see them short in that manner, or possibly a jumper on the C4S board above that socket that isn't wired properly.
here's the underside.
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There's a front C4S board that sits up by the three signal tube sockets, then a C4S regulator board above the D socket. On the C4S regulator board you've shown me, I would reflow all the solder joints other than those for the LEDs. If you are using lead free solder, I would grab some 60/40 Kester rosin core solder. If you are using leaded solder, I would turn up the heat so things are a bit more willing to flow out.
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There's a front C4S board that sits up by the three signal tube sockets, then a C4S regulator board above the D socket. On the C4S regulator board you've shown me, I would reflow all the solder joints other than those for the LEDs. If you are using lead free solder, I would grab some 60/40 Kester rosin core solder. If you are using leaded solder, I would turn up the heat so things are a bit more willing to flow out.
Okay, cool. I 'll r eflow those joints now. But other than that do the jumpers look wired properly?
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There's a front C4S board that sits up by the three signal tube sockets, then a C4S regulator board above the D socket. On the C4S regulator board you've shown me, I would reflow all the solder joints other than those for the LEDs. If you are using lead free solder, I would grab some 60/40 Kester rosin core solder. If you are using leaded solder, I would turn up the heat so things are a bit more willing to flow out.
also, i checked my solder, it is 60/40 rosin core.
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Turn up that heat!
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Turn up that heat!
Okay, i re-flowed every joint and im still getting 178-180mV on KregA. Heat on my iron is up as high as it goes.
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Are both halves of the 12AU7 glowing?
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Are both halves of the 12AU7 glowing?
sorry it took me a bit. but yes, both sides are glowing. I even swapped out the tube that came with the kid and put in an RCA.
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The next thing to do would be to set your meter to beep when you touch the probes, then start probing all the pairs of all the transistors and the 431 regulators on the board above the D socket to see if any of them are internally shorted.
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The next thing to do would be to set your meter to beep when you touch the probes, then start probing all the pairs of all the transistors and the 431 regulators on the board above the D socket to see if any of them are internally shorted.
I'm not sure my meter has that option. Also, I probing around a min ago and caused another spark. this time at the resistor at reg on side B. Now none of the LEDs turn on and the voltage on side B is now siting around 170v while on side A it is still at 260v
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The next thing to do would be to set your meter to beep when you touch the probes, then start probing all the pairs of all the transistors and the 431 regulators on the board above the D socket to see if any of them are internally shorted.
Both of the 100KΩ 3W are beeping on opposing ends. Also one end of each of the 0.1 μF 400V film capacitors, the 431 resistors on side B and A as well as the 2.49KΩ resistors
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Also, I think I may have figured out where the issue was in the first place. The wire connected to D8 wasn't soldered so well, but while i was probing and trying to find an issue with a resistor I caused those sparks that I'm sure shorted out one or even all of the resistors that are now beeping. Let me know which one's I should buy replacements for.
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If a resistor shorts, typically it will burn itself up in the process. If that hasn't happened, then the beep may be an instantaneous beep that goes away after a short time due to a capacitor charging.
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If a resistor shorts, typically it will burn itself up in the process. If that hasn't happened, then the beep may be an instantaneous beep that goes away after a short time due to a capacitor charging.
The beeps I get are continuous until I remove the probe. When you say “burn up†would this be something I can see on the resistor? Also should I hold the probe on the resistors that are beeping for a while to see if the beep stops?
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Yes, and we also would expect the resistor to fail to a state that's completely open. Keep in mind that you need the probes across the part itself, not one probe on ground and the other probe poking around the circuit.
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Yes, and we also would expect the resistor to fail to a state that's completely open. Keep in mind that you need the probes across the part itself, not one probe on ground and the other probe poking around the circuit.
Ohh okay. I was attaching my black ground clip to the ground near the power switch and then probing the lead of each resistor with the red probe. But you’re saying I need a probe on each of the of the resistors correct?
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You need to probe each pair of pins on all the solid state devices (transistors and regulator chips).
You do not need to probe the resistors. A blown resistor avails itself with sounds, sights, and smells.
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You need to probe each pair of pins on all the solid state devices (transistors and regulator chips).
You do not need to probe the resistors. A blown resistor avails itself with sounds, sights, and smells.
Okay so you’re saying on the underside of the board I need to probe the points where I soldered them in? Sorry I’m just confused by what the “pins†are.
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Yes, the pins of the transistors and regulators are the leads that are poking through the bottom of the PC board.
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Yes, the pins of the transistors and regulators are the leads that are poking through the bottom of the PC board.
Okay, so I disconnected the board and took it off, flipped it over and probed those regulators. The LM431 regulators give me a constant beep as long as I hold the probes on any two pins. Same goes for when I probe the PN2907A pins. The pins on the MJE5731A on side B also give me a constant beep and ones on side A give me the same but with different pins being probed. Does this mean all of the regulators and transistors are shorted and that I need new ones?
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It is incredibly improbable that every single transistor on that board is fried, and that's not reflected in your voltage measurements. It may just work out best in this situation to use our repair service so I can fix this for you.
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Yes, the pins of the transistors and regulators are the leads that are poking through the bottom of the PC board.
?
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It is incredibly improbable that every single transistor on that board is fried, and that's not reflected in your voltage measurements. It may just work out best in this situation to use our repair service so I can fix this for you.
Darn okay. Thanks for helping Paul.
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It is incredibly improbable that every single transistor on that board is fried, and that's not reflected in your voltage measurements. It may just work out best in this situation to use our repair service so I can fix this for you.
Hey PB, I went ahead and just reordered the shunt regulator board since that was where the problem seemed to lie. I just rebuilt it tonight and turned it on. Voltage on side A is 229v and on side B it's 221v. Both are within range, but not identical. Could this be a potential problem? I just wanted to double check with you before I went ahead and reconnected the C4S board.
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That is likely more of a resistance tolerance thing. How are the Kreg voltages?
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That is likely more of a resistance tolerance thing. How are the Kreg voltages?
side A is 1.93v
side B is 1.92v
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That is still not working properly and those voltages tend to suggest that you may have solder bridges on the PC board, parts swapped, or miswired jumpers. Possibly the Kreg wires or OA/OB wires could also be swapped.
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That is still not working properly and those voltages tend to suggest that you may have solder bridges on the PC board, parts swapped, or miswired jumpers. Possibly the Kreg wires or OA/OB wires could also be swapped.
what would a solder bridge look like?
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That is still not working properly and those voltages tend to suggest that you may have solder bridges on the PC board, parts swapped, or miswired jumpers. Possibly the Kreg wires or OA/OB wires could also be swapped.
here's the top and bottom of the board. I can't see any issues. What do you think?
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Can I see what the D socket looks like with that board pulled out? I do see one solder joint on one of the PN2907s that doesn't look 100%, but nothing else that's obvious.
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Can I see what the D socket looks like with that board pulled out? I do see one solder joint on one of the PN2907s that doesn't look 100%, but nothing else that's obvious.
sure thing. I'll reflow that PN2907 as well.
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Other than the wire leaving D5 being improperly routed, I don't see any issues. At this point things like non-electronics solder and flux start to pop up as possibilities for creating the issues you're experiencing.
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Other than the wire leaving D5 being improperly routed, I don't see any issues. At this point things like non-electronics solder and flux start to pop up as possibilities for creating the issues you're experiencing.
okay, the one that goes through D5 and into D4?
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Yes. This isn't going to be the cause of your problems, but rather something that may cause problems down the road.
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Yes. This isn't going to be the cause of your problems, but rather something that may cause problems down the road.
Oh okay. What do I need to change? Also, as for the solder I'm using it is 60/40 rosin core. Made by Cookson Electronics. It is however a bit thicker than what I used on my crack, but to be honest that actually made the soldering easier for me.
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With one probe on each of the 6.3V terminals, what DC voltage do you see? It occurs to me that it's possible that your 6.3V regulated DC supply may not be putting out sufficient voltage for proper tube emission, so that's worth looking into (or there's something in the heater circuit consuming extra current).
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With one probe on each of the 6.3V terminals, what DC voltage do you see? It occurs to me that it's possible that your 6.3V regulated DC supply may not be putting out sufficient voltage for proper tube emission, so that's worth looking into (or there's something in the heater circuit consuming extra current).
Okay, I'm getting 6.25v on the 6.3 V terminals on the PSU board.
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With one probe on each of the 6.3V terminals, what DC voltage do you see? It occurs to me that it's possible that your 6.3V regulated DC supply may not be putting out sufficient voltage for proper tube emission, so that's worth looking into (or there's something in the heater circuit consuming extra current).
Hey PB, I noticed that one of the screws that is supposed to secure the PSU board just wasn't there, found it and screwed it in. I decided to go ahead and connect everything and redo my voltage tests. Everything was well within range on all boards. The Kreg on the shunt regulator is still showing me ~1.9v on both sides but I went ahead and turned it on and everything sounds perfect to me. No balance issue. No hum. Do I still need to worry about that Kreg value on the shunt regulator?
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If the front C4S board is hooked up and you still see 1.9V at each of the Kreg pads on the board above the D socket, what's the DC voltage at the +275V pad on the power supply board above the power transformer?
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If the front C4S board is hooked up and you still see 1.9V at each of the Kreg pads on the board above the D socket, what's the DC voltage at the +275V pad on the power supply board above the power transformer?
With the C4S board connected I'm getting 5.94v on side A and 5.92v on side b. DC voltage on the +275 pad is 265v.
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I do also have the step up transformers installed if that makes any difference.
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Those Kreg voltages are more reasonable and should be sufficient for the circuit to operate properly.
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Those Kreg voltages are more reasonable and should be sufficient for the circuit to operate properly.
Awesome. Thanks for you help Paul.