Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Reduction => Topic started by: ryburdman on February 26, 2021, 04:04:08 AM
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All resistances check all LED's light up. I am getting a hum in both channels and no audio coming through at all. I hooked up another phono and it works normally so I am pretty sure its not the TT or the amp.
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The last Reduction I fixed had the following issues:
1. All the RCA jacks were not installed properly. The metal ring tab was mounted against the chassis and not directly under the nut, which caused there to be no audio.
2. The ground wires that run through/around the 9 pin sockets were loose on the sockets and not adequately soldered.
3. There were a few other random solder joints that weren't solid that were also causing problems.
Since you don't have audio on either channel, I would be looking at how you installed your RCA jacks.
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As I fiddle with the RCA's i found I can get it to stop humming and work great if I wiggle the black output RCA but its really finicky. On inspection it looks exactly like the other RCA's.
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Can you post some build photos?
If the RCA jacks are assembled in the proper order, then the problem you have suggests there's a loose solder joint or two.
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https://photos.app.goo.gl/qdujsXFnAFRwzwn47
Let me know if you want any specific angles or shots I can take more
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I would recommend getting a proper pair of side cutters (I use the CHP-170) and trim off all those leads nice and short that are poking out. The one coming out of 26L that's almost touching the chassis will smoke part of the amp when it does touch the chassis.
I would reheat the solder joints on the ground lug of each input RCA jack. Those don't look like they have flowed out all the way.
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Yeah and maybe reflow terminal 22. Can't see it in the pics, but that is what the ground end of the output RCA connects to. RE the side cutters, I just got a pile of grievance for not buying $40 swiss side cutters when I posted my intended-to-be-humorous broken sidecutter on social media. A Swiss sidecutter that, I will note, won't fit into a lot of tight places we need side cutters to fit. I would guess the guys posting the spendy cutters don't work in an environment where the less experienced employee will use a soldering iron for a prybar or a ceramic screwdriver as a cold chisel. I lost a really nice $500 solder station to that kind of activity. The $5 side cutters like Hakko and Xcelite we have around are perfectly adequate for what we are doing and it's no biggie if somebody does something dumb with them. We cut thousands of pieces of wire with those cutters every year.
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My two cents: I wouldn't even try to hunt down the problem until I reheated every single solder joint in the amp. I see a lot of what look to be cold solder joints (lumpy solder) and no signs of melted wire insulation near the cut ends -- both signs of using too low a temperature. If you have an adjustable iron, I'd crank it up to at least 750 F. If you don't have an adjustable iron, try letting the tip dwell longer on the joint. When reheating a joint, it's not enough that the solder melts; you want to see it run like water into the joint. MORE HEAT! You might find that reheating all the joints solves the problem a lot faster than trying to figure out which particular joint or joints is/are the problem -- and end up with a amp that will stay sounding great longer.
cheers from the peanut gallery, Derek
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Thanks for the input guys. I reflowed the RCA's and the problem moved to the other red output RCA so I am going to take Dekes advice and just reheat everything. I have an adjustable iron set at 750 should i go higher?
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I set mine at 899, which is as high as it can go.
If you happen to have new Hakko 888, it's very easy to think you're turning up the heat when you are actually in calibration mode and are in actuality decreasing what would be the maximum temperature.
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Ok. I set the iron to 899 and reflowed everything. I no longer get a hum anywhere and the audio from the red rca's works great but nothing out of the black rcas. no hum no audio.
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Recheck your voltages and resistances.
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All voltages check out except for my manual shows 0 for 44 and 45 and they are reading 80 but from an earlier thread I believe this is where they are supposed to be I just mention it to be thorough
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44 and 45 will depend a bit on the meter, but if everything else is OK those terminals can't be incorrect.
I would suggest that you're still looking at a bad solder joint or a solder bridge across an RCA jack. You could certainly post some more photos, especially since you can now focus in on one half of the build.
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https://photos.app.goo.gl/EcjzRKeadbBoaBdS9
Here is a new set of pictures focusing on the black RCA side
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Can you remove the inner lead of the 0.1uF coupling cap and the 0.47uF coupling cap and pull them straight up, then post some more pics with those mostly out of the way?
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https://photos.app.goo.gl/TX6NB1XGS8EAw8DU6
EDIT
Now with the new link
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I would scrape this off. I'd also get those solder balls away from terminals 17/18, you don't want those to make a connection between the red wire and the chassis plate!
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This could also cause problems. This and solder joints is the kind of stuff you want to look for when your DC voltages look good but sound isn't making it through.
If cleaning out these jacks doesn't work, let me know what kind of multimeter you have (brand and model) and we can send some signal voltage into your Reduction and take some measurements.
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I have a fluke 115
How do I go about cleaning the RCA's out?
Do you mean the mark around 29? its not a solder ball it was an arc I had when I most recently voltage tested it was a trimmed wired that wasnt cleared out and made a spark
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You can use a toothpick to clean out the jacks. I would do that before doing any signal testing.
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Cleaned out the RCA's and resoldered the caps. Tested it still nothing out of one channel. I have to go pick my boys up from school. I will be able to make a run at this again tomorrow.
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OK, post the make and model of your meter and I can give you some follow up instructions.
-PB
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I have a fluke 115
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OK, find a device (phone/tablet) with a headphone jack and download either a signal generator app or a 60Hz tone. With an 1/8" TRS to RCA cable, you should be able to measure the AC voltage coming out of the RCA jacks and turn the device all the way down, then up one step on the volume control. Let us know what AC voltage this is.
Plug the RCA cables into your Reduction with the Reduction off an measure the AC voltage across each RCA jack and let us know what it is.
The Fluke 115 has a mV range and it looks like it will default to AC mV, which is what you want. I would expect your phone to put out maybe 300mV at max volume and somewhere between 5 and 10mV one step above mute.
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Sorry for the delay I had life get in the way and had to get a TRS to RCA sourced. I am a big unclear as to where to and how to measure on the RCA I want to make sure I get you a good reading.
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Plug the TRS to RCA into your device, download a signal generator app and play a 60Hz tone. Put your black meter probe on the shell of one RCA plug and the red probe on the center of one RCA plug, set your meter to AC millivolts, then adjust the volume all the way down on your device, then up one click. Let us know what that AC voltage is that you see.
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Black input 49mv
Red input 52mv
Black output 55mv
Red output 81mv
It fluctuates a lot and is tough get get a good reading on it.
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You're not quite following what I'm asking you to do.
1. Put the Reduction in another room, close the door, leave it alone for now.
2. Plug the 1/8" TRS to RCA cable into your phone/tablet/whatever.
3. Download a signal generator app.
4. Play a 60Hz tone though it.
5. Turn the volume all the way down, then up one click.
6. Now measure the AC voltage across each RCA plug at the end of your TRS cable.
The minimum AC voltage that can come from most devices will be a lot lower than 50mV. Be aware that your meter has a different setting for AC millivolts that will give you more stable readings.
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Gotcha,
2.5mv Red and White outputs
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Perfect, now grab your Reduction and plug those RCA cables into the inputs. You don't need to apply power to the Reduction, just the RCA cables.
Now read the AC voltage across the input jacks.
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2.5 red
2.3 black
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OK, that tells you that the input jacks aren't clogged with debris.
Power the Reduction up and play that tone into the inputs. You can just anchor your black meter probe to the grounding screw if that's easy for you, then measure the AC voltage at:
6
10
19
23
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6-0
10-2.5
19-0
23-10
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6-0
10-2.5
6 really can't be 0V if 10 is 2.5. You're also missing units, is that 2.5V or 2.5mV?
19-0
23-10
Ditto here, 10V? 10mV? What AC voltage do you see at terminal 27?
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Sorry, i was all mess up on the last one heres a retry
6-13mv takes a bit to get there starts at like 6 and slowly climbs
10-230mv
19-0 and one of the led's blinks when i test it
23-140mv
27 -12mv takes a bit to get there starts at like 6 and slowly climbs
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19-0 and one of the led's blinks when i test it
You have a loose connection, that causes the LED to blink.
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After probing more, it only makes a led blink off if I have the Fluke in mv if its in regular ac volts I don't get the Lightning bolt icon and the led doesn't go off, I am wondering if that's the meter causing the leds to go out.
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No, you have a loose connection making the LED flash. There isn't anything about what the meter is up to that will cause that.
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Ok if that's the case, when I measure with the meter in ac mv heres where leds blink
2- led to 3
7- both leds
13-led to 3
14 led to 3
15 both
---------
18 both
19 led to 9
20 led to 9
26 both
29 9
31 9
Sorry this is taking so much of you time and such a pain, I really appreciate the help.
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6-13mv takes a bit to get there starts at like 6 and slowly climbs
27 -12mv takes a bit to get there starts at like 6 and slowly climbs
Ignore what I said previously about 19. What we see with 6 and 27 is the amplification after the first stage. You have 13mV and 12mV of signal coming out. This is way lower than what I would expect with 2.5mV of signal coming in, but it's consistent.
Can you carefully measure the AC voltage again at 10 and 23? If you have 12-13mV at 6 and 27, you can expect far more than that at 10 and 23.
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10-230 mv
23- 140mv
I just want to mention as to make sure i am doing this correctly. When I am just holding the red probe in the air with the black connected i am reading around 260mv, if I unclip the ground and just hold both in the air I am reading 60mv. The readings I am giving you are when black is clipped to the ground and red its touching 10 or 23.
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Yes, the black probe needs to go to the ground lug on the chassis and the red probes to the terminals in question.
The reading on 23 indicates that your Reduction is passing some signal, but not a sufficient amount.
Can you post some fresh photos like the first set you posted? In that set of images, I saw lots of issues and perhaps some of those are still present.
If all else fails we can get you setup with a flat rate repair, but I would not at all be surprised to find that if I reflow all your solder joints, your Reduction will work fine.
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Here is a new set
https://photos.app.goo.gl/v5dcuCkjJgmHqJyB8
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The 0.47uF cap on the left channel looks like the leads are snapped coming out of one end.
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I have checked both sides of both .47 uf caps it feels and looks solid not snapped but here are some close ups.
https://photos.app.goo.gl/uGH5pseHvAmEJkACA
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An optical illusion then.
I'm not sure I have anything else to offer. The signal tracing seemed to indicated that audio is making it through your Reduction, albeit with some channel imbalance, but your audio tests indicate just hum and no audio. While we can do a flat rate repair for you, it seems equally likely that either your Reduction will work OK here or this will just be a matter of solder joints.
Let us know how you would like to proceed.
-PB
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What are we looking at for a repair fee?
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Since your kit is assembled with the stock parts and doesn't wildly deviate from the manual, you're good to go with the old $125 flat rate repair. We can setup the order and UPS you a box and packing materials, then you are responsible for shipping the amp to us with those materials and paying for return shipping on the repaired kit back to you.
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Ok great, I am going to give it one more try to flow the joints, cross my fingers and see if that does it, if not I'll send it in.
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One of the things I am trying is swapping the tubes to see if the problem follows them. As I do that I'm noticing the Left side (black) tube socket is really tight and tough to seat the tube. Could this be causing the issue?
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A tight socket is generally a very good thing.
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Ok I give up, Ill send it in. What do I need to do to start that process.
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You can call the office or e-mail [email protected]. Let Eileen know that we have chatted on the forum and I've sent you to her for the repair service and she'll get you taken care of.
-PB
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I got this kit on the bench today and it's impeccably built and perfectly functional right out of the box.