Ting Ho Dung Posted September 12, 2015 Posted September 12, 2015 I would like to send an amp head with a hum issue to someone who can fix it.
mathman Posted September 12, 2015 Posted September 12, 2015 There was someone in Land o' lakes. Can't remember his name now. Let me see if I can find it.
ArnieZ Posted September 12, 2015 Posted September 12, 2015 HFC'er Brewmaster was making amps for a while I think he is in FLA.ArnieZ
mathman Posted September 12, 2015 Posted September 12, 2015 That's him. I think he is in Land O' Lakes or at least he was.
Ting Ho Dung Posted September 12, 2015 Author Posted September 12, 2015 Anyone know how to get hold of him? He hasn't been on since June and his website isn't functioning.
veatch Posted September 12, 2015 Posted September 12, 2015 For hum, I would start with the filter caps. If you're handy with a soldering iron, they're usually pretty easy to replace.
Biz Prof Posted September 12, 2015 Posted September 12, 2015 Dumb question: Isn't it filter caps that are usually the culprit behind excessive white noise in high-wattage circuits like old Marshalls?
it's me HHB Posted September 12, 2015 Posted September 12, 2015 They also maintain nearly lethal voltage even with amp unplugged, proceed with caution ( big-time )
JGale Posted September 12, 2015 Posted September 12, 2015 Where are you? What kind of amp is it? Does anything affect the hum, plugging, unplugging, control knob movement, touching the amp chassis, etc.Possibilities range from loose wire to bad components. Is it tube? Have you swapped them out? All these things and more, Howie.EditedToAdd: Next question is does anyone have a circuit diagram?
Ting Ho Dung Posted September 12, 2015 Author Posted September 12, 2015 Where are you? What kind of amp is it? Does anything affect the hum, plugging, unplugging, control knob movement, touching the amp chassis, etc.Possibilities range from loose wire to bad components. Is it tube? Have you swapped them out? All these things and more, Howie.EditedToAdd: Next question is does anyone have a circuit diagram?I'm between Orlando and Tampa. The amp hums when you turn it on with a low Hz hum. It doesn't change when all knobs are at zero and nothing at all is plugged in except for the speaker. It doesn't seem to be a grounding issue as it doesn't change when touched or things are plugged in. It's a 6v6 18 watt / bassman IIRC that I bought off ebay because it was point to point and I was considering getting back into electronics and thinking about learning mods. All the components were supposed to be new except for the RCA glass. Those are the only tubes I haven't swapped because all I have are 6l6s. I have a schematic that supposedly is what this guy built.
triodecr Posted September 13, 2015 Posted September 13, 2015 Did it just start humming or did it always have the hum? If it's always been there then I would suspect output tubes or improper grounding when built.
randelli Posted September 13, 2015 Posted September 13, 2015 Amps hum when they can't remember the words...I could help but I am in Austin.
Armitage Posted September 13, 2015 Posted September 13, 2015 You didn't let the blue smoke out did you?It simply amazes me how they get all that blue smoke in there in the first place.
JGale Posted September 13, 2015 Posted September 13, 2015 Can you post the circuit? Anyone near him that can shoot him some different 6V6 tubos?
Ting Ho Dung Posted September 13, 2015 Author Posted September 13, 2015 Did it just start humming or did it always have the hum? If it's always been there then I would suspect output tubes or improper grounding when built. It has always hummed. I know a little about electronics and it seems every circuit is excessively grounded which makes me wonder if it's a ground loop. Can you post the circuit? Anyone near him that can shoot him some different 6V6 tubos? I'll certainly look for it. Didn't take as long as I thought to find it. 18 W 6V6c modification on Mark Huss plexi and JTM 45 Here's a PDFe with more Couple Links he sent me. This is the actual amp. It's the beige MAM 20
randelli Posted September 13, 2015 Posted September 13, 2015 Post up the schematic and or layout for review.I have delt with my fair share of hum issues and may be able to help out. I have a process that I go through; but it envolves open chassis and potential shock hazzards. Proper cap discharge technique is a must!
Ting Ho Dung Posted September 13, 2015 Author Posted September 13, 2015 Post up the schematic and or layout for review. I have delt with my fair share of hum issues and may be able to help out. I have a process that I go through; but it envolves open chassis and potential shock hazzards. Proper cap discharge technique is a must! Damn, Don't know what happened. They were there and now, Poof! Must have lost them in one of my edits. Here. 2nd Schematic PDF
randelli Posted September 13, 2015 Posted September 13, 2015 I think I was typing while you were attaching... One thing we can do is try to isolate the circuit to see when the hum starts. Do these steps in order, turning off the amp between steps, and see which sections are clean. This will point us to the trouble spot. Be sure to leave the speaker connected! 1) Remove ALL tubes and turn on the amp. This will let us know if the PT and or OT are the culprit. Sometimes they hum a little. Turn OFF the amp! 2) Add the 6V6 power tubes and turn the amp on again. This will tell us if it is in the power section. Turn OFF the amp! 3) Add the V3 recovery 12AX7. This will tell us if it is after the tone stack, or in the presence circuit. Turn OFF the amp! 4) Add the V2 preamp 12AX7. This will tell us if it is in the second gain stage, or in the tone stack. Turn OFF the amp! 5) Add the V1 preamp 12AX7 or 12AY7. This will tell us if it is in the first gain stage or volume section. Try this and report back. Notes: Two of the filter section resistors are not labeled on the schematic. Do you know what they are? The heater wires to the tubes do not appear to be twisted to cancel out RF noise.
Ting Ho Dung Posted September 14, 2015 Author Posted September 14, 2015 I think I was typing while you were attaching... One thing we can do is try to isolate the circuit to see when the hum starts. Do these steps in order, turning off the amp between steps, and see which sections are clean. This will point us to the trouble spot. Be sure to leave the speaker connected! 1) Remove ALL tubes and turn on the amp. This will let us know if the PT and or OT are the culprit. Sometimes they hum a little. Turn OFF the amp! 2) Add the 6V6 power tubes and turn the amp on again. This will tell us if it is in the power section. Turn OFF the amp! 3) Add the V3 recovery 12AX7. This will tell us if it is after the tone stack, or in the presence circuit. Turn OFF the amp! 4) Add the V2 preamp 12AX7. This will tell us if it is in the second gain stage, or in the tone stack. Turn OFF the amp! 5) Add the V1 preamp 12AX7 or 12AY7. This will tell us if it is in the first gain stage or volume section. Try this and report back. Notes: Two of the filter section resistors are not labeled on the schematic. Do you know what they are? The heater wires to the tubes do not appear to be twisted to cancel out RF noise. Spent some time doing these steps except I don't know which is position is which. So I've linked this photo to help. It appears to be the 12ax7 in the rear in the photo. I also noticed that touching the chassis and on / off switch does decrease the hum a bit but not noticable like touching grounded guitar strings in an amp that works correctly . So here's the take: No chord plugged in inputs. No tubes, had to get on hands and knees in front of the speaker to hear any hum Power tubes, again on hands and knees but could hear a bit of hum about a foot away. Power tubes in and 12ax7 in the rear position and could hear a lot of hum. Even standing and walking away in the room. It's pretty loud. Power tubes in and (since I didn't know which position was which) moved 12ax7 to the left-center position and pretty much the same hum as just the power tubes alone. Power tubes in and moved 12ax7 to the front position, same as above. Power tubes in and 12ax7 left in front position and then added 12ax7 to the left-center, same as above. Power tubes in and added third 12ax7 and lots of hum. Power tubes in and different combinations in the 3 positions and the culprit seems to be the position in the rear. Something I forgot to mention earlier that happens is there is an odd "swish" sound when the presence know is turned in either direction. The same kind of sound like covering the mouth piece on the old chord phones when you didn't want the person on the other end to hear what was being said. Edit for clarification and shitty typing.
randelli Posted September 14, 2015 Posted September 14, 2015 I would try new 12AX7's if you have any available. The point to point may also be part of the problem. It is coming in the gain stages and careful layout plus sheilded signal wiring would lessen that. Of course, once the drummer comes in, it doesn't matter anyway.
Brewmaster Posted September 14, 2015 Posted September 14, 2015 I heard somebody was looking for me. Yes, I'm alive and well, still in remission, and go for maintenance treatments one a year to ensure I stay there.You need to also look at the solder joints. I can't tell you how many time I have traced hum issues to a poor solder connection.If you are local, send me a PM and I'll take a look at the amp.. Just an FYI....I built a 6v6 based 18 for another builder a few years ago and he owns one of my 18 watt heads. The boards on bothhave considerable differences from what you will find on the 18watt site. I also had custom trannys in mine but have bulit several with Heyboyers.
Ting Ho Dung Posted September 15, 2015 Author Posted September 15, 2015 I would try new 12AX7's if you have any available. The point to point may also be part of the problem. It is coming in the gain stages and careful layout plus sheilded signal wiring would lessen that. Of course, once the drummer comes in, it doesn't matter anyway. I have several 12ax7s around and a few of the 12a*7s. Still the same when the one in the back is plugged in. Thanks for your help. It now needs to go to someone because while I was playing through it today it is really the best amp I have. I heard somebody was looking for me. Yes, I'm alive and well, still in remission, and go for maintenance treatments one a year to ensure I stay there. You need to also look at the solder joints. I can't tell you how many time I have traced hum issues to a poor solder connection. If you are local, send me a PM and I'll take a look at the amp.. Just an FYI....I built a 6v6 based 18 for another builder a few years ago and he owns one of my 18 watt heads. The boards on both have considerable differences from what you will find on the 18watt site. I also had custom trannys in mine but have bulit several with Heyboyers. Thanks, will do so ASAP
veatch Posted September 15, 2015 Posted September 15, 2015 I heard somebody was looking for me. Yes, I'm alive and well, still in remission, and go for maintenance treatments one a year to ensure I stay there.You need to also look at the solder joints. I can't tell you how many time I have traced hum issues to a poor solder connection.If you are local, send me a PM and I'll take a look at the amp.. Just an FYI....I built a 6v6 based 18 for another builder a few years ago and he owns one of my 18 watt heads. The boards on bothhave considerable differences from what you will find on the 18watt site. I also had custom trannys in mine but have bulit several with Heyboyers.*GREAT* to hear from you, sir. Good to hear you are in remission.
tomteriffic Posted September 15, 2015 Posted September 15, 2015 I heard somebody was looking for me. Yes, I'm alive and well, still in remission, and go for maintenance treatments one a year to ensure I stay there.You need to also look at the solder joints. I can't tell you how many time I have traced hum issues to a poor solder connection.If you are local, send me a PM and I'll take a look at the amp.. Just an FYI....I built a 6v6 based 18 for another builder a few years ago and he owns one of my 18 watt heads. The boards on bothhave considerable differences from what you will find on the 18watt site. I also had custom trannys in mine but have bulit several with Heyboyers.What Jef and Jim said. GREAT to see you back and even better to hear you are in remission!
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Ting Ho Dung
I would like to send an amp head with a hum issue to someone who can fix it.
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