Similar problem with a twist
Hi,
I know this thread is quite old but it is so on point for me I hope I can get some suggestions. I have a DH-110/DH-220 combo. The 110 has been acting up lately and is now basically non-functional.
Symptoms are the right channel no longer works. I have used Deoxit on all pots and the input selector (the selector feels rough when switching). Initially, the problem was solved when a great expert in Seattle told me to plug into the headphone jack a couple times to make sure its contacts were releasing. That lasted about a month. Now nothing seems to work.
Something interesting - and perhaps telling - is that I had a FiiO X3 providing audio signal. I turned off the preamp while the FiiO was still playing and while the amplifier was still on. I noticed that some low-level signal was getting through, very distorted but sounded like both channels - even with the preamp off. And, another thing, when switching the source selector, there was some bleeding of signal - audio in to tuner inputs but low-level distorted sound when on selector on Aux.
I do not know much. I have the schematic but am no electronics expert. I do follow directions/suggestions pretty well though. Any thoughts? Crosses fingers . . . .. . . .
Hi,
I know this thread is quite old but it is so on point for me I hope I can get some suggestions. I have a DH-110/DH-220 combo. The 110 has been acting up lately and is now basically non-functional.
Symptoms are the right channel no longer works. I have used Deoxit on all pots and the input selector (the selector feels rough when switching). Initially, the problem was solved when a great expert in Seattle told me to plug into the headphone jack a couple times to make sure its contacts were releasing. That lasted about a month. Now nothing seems to work.
Something interesting - and perhaps telling - is that I had a FiiO X3 providing audio signal. I turned off the preamp while the FiiO was still playing and while the amplifier was still on. I noticed that some low-level signal was getting through, very distorted but sounded like both channels - even with the preamp off. And, another thing, when switching the source selector, there was some bleeding of signal - audio in to tuner inputs but low-level distorted sound when on selector on Aux.
I do not know much. I have the schematic but am no electronics expert. I do follow directions/suggestions pretty well though. Any thoughts? Crosses fingers . . . .. . . .
Hafler DH
Hi,
Thanks for the reply.
I do get stereo sound in my headphones. But now, if I use the line outs to my Mitsu Amp, it throws the amp into protection mode.
I even tried to used the headphone out signal plugged into the amp and the amp went into protection mode. If I used the headphone out on my FiiO directly into the amp, it worked perfectly.
Something is whacked for sure. Any thoughts?
Hi,
Thanks for the reply.
I do get stereo sound in my headphones. But now, if I use the line outs to my Mitsu Amp, it throws the amp into protection mode.
I even tried to used the headphone out signal plugged into the amp and the amp went into protection mode. If I used the headphone out on my FiiO directly into the amp, it worked perfectly.
Something is whacked for sure. Any thoughts?
Hafler DH 110
Hi,
I got out my DVM and plugged in a line level signal into the tuner inputs and set the volume at 1/2 on the preamp..
Putting + probe on the inside and the common probe on the outside I got the following:
1. Left side headphone = -13.3v Right side headphone = -5.2v
2. Direct line out on back = L = 2.3v R= 0.0v
The output voltages increased/decreased if I changed the volume knob.
Seems to me, even as inexperienced as I am, that the headphone voltages are wacky and the line out R should register more than 0!
Hi,
I got out my DVM and plugged in a line level signal into the tuner inputs and set the volume at 1/2 on the preamp..
Putting + probe on the inside and the common probe on the outside I got the following:
1. Left side headphone = -13.3v Right side headphone = -5.2v
2. Direct line out on back = L = 2.3v R= 0.0v
The output voltages increased/decreased if I changed the volume knob.
Seems to me, even as inexperienced as I am, that the headphone voltages are wacky and the line out R should register more than 0!
I know a guy.....that is a top notch audio equipment technician that takes great care in restoring the quality of sound and appearance to first rate equipment such as your Hafler amp and preamp for very reasonable prices. I know for a fact that he owns the same amp and preamp part of his private collection. He has serviced my Yamaha CA-2010 and CT-1010, my McIntosh MC2105 and my tube amp.
He is in the Chicago area.... If you can't find someone closer with a great reputation contact me and I will put you in touch.
He is in the Chicago area.... If you can't find someone closer with a great reputation contact me and I will put you in touch.
Yes, if with no signal you have DC voltages present at the outputs, then there are definite problems,
such as bad coupling capacitors, etc. You should have 0VDC at all outputs.
Well,
I finally got back to working on my Hafler DH-110 and was searching the interwebs and came across this and had forgotten I posted here. I have learned a lot. Now, after having replaced several caps, an IC for the power on/off delay and two transistors the J112, my preamp sings, is clear and I am very happy. No thump on power off either. Thanks!
I finally got back to working on my Hafler DH-110 and was searching the interwebs and came across this and had forgotten I posted here. I have learned a lot. Now, after having replaced several caps, an IC for the power on/off delay and two transistors the J112, my preamp sings, is clear and I am very happy. No thump on power off either. Thanks!
Hi there, new here and so glad I found this forum!
I just hooked up my Hafler amp and preamp after 12 years and I suspect the preamp is not working. Tried another amp with same result. Tried inputs from CD, tuner and ipod with same results (waiting for parts for turntable). I built both in the summer of 1980. Preamp has been in constant service, recently driving a pair of big Crowns.
Just moved from Winnipeg to Cobourg and move may have hurt the preamp.
I just hooked up my Hafler amp and preamp after 12 years and I suspect the preamp is not working. Tried another amp with same result. Tried inputs from CD, tuner and ipod with same results (waiting for parts for turntable). I built both in the summer of 1980. Preamp has been in constant service, recently driving a pair of big Crowns.
Just moved from Winnipeg to Cobourg and move may have hurt the preamp.
Your situation is not clear. I gather that you have been running the Hafler DH 110 for 12 years, and then hooked it up again after a move, and then it did not work. If so, this should eliminate problems due to it sitting around unused for 12 years (cap reforming, dirty switches, etc.).
Your next post mentions minimal sound at maximum volume.
The jfets that ground the signal to mute it at turn-on could be the cause, but it is odd that both would go bad at the same time, and from just jiggling around in a vehicle. My guess is it is a switch, or the even more likely, the problem is one or both of the ribbon cables that connect the PC board to inputs and outputs. Try removing these at both ends, spraying some contact cleaner on them, and then re-connect them and try it again. You could just wiggle them around a bit to see if that changes anything, but it is worth cleaning them after so many years. I have a DH110, and have had trouble with the jfets and the ribbons. Those have been the only problems I can remember.
Hi mmerig,
No, please do not spray contact cleaner on cable ends and sockets. Especially don't jiggle the wires around as that will cause broken connections.
Hi Riverman,
Welcome to DIYAudio. I hope you enjoy posting here.
Best thing to do is to have a look at it on the bench. That way signals can be traced and meters can tell us when something is shorted or open. We don't have to resort to rough treatment of the internals which may bite you years later.
Best, Chris
No, please do not spray contact cleaner on cable ends and sockets. Especially don't jiggle the wires around as that will cause broken connections.
Hi Riverman,
Welcome to DIYAudio. I hope you enjoy posting here.
Best thing to do is to have a look at it on the bench. That way signals can be traced and meters can tell us when something is shorted or open. We don't have to resort to rough treatment of the internals which may bite you years later.
Best, Chris
The ribbons and plugs on the Hafler are quite tough, and not what we typically see in modern CD players etc. I should have been more clear though in what I meant by "jiggling". Sometimes, when contacts are a bit corroded, a gentle rocking of the plug on the pins will make a difference, and that would indicate a problem there. Or better yet, you can just remove and replace the plug and see what happens then.
Examining it on a bench is a good idea, but what if that examination points to corroded plugs or pins? Removing the plugs is just as hard on the pins and plug as gently wiggling them. Given the circumstances (a move), the problem is likely electro-mechanical, not a shorted transistor or something like that. So why not start with the most likely components (the ribbons and plugs).
Why not use contact cleaner on dirty/corroded contacts? Some people use denatured isopropyl alcohol to clean contacts, rather than a naptha-based one like Caig DeOxit. The latter is okay to use on all electrical contacts, including plugs and cables, according to the label.
Hi mmerig,
On the bench, the unit is under more controlled circumstances. Careful tapping and signal tracing finds most issues. There could be a cracked solder on the PCB as well. Cleaning solvents tend to wet up the legs of capacitors and some transistors. Sprays are poorly controlled and there tends to be a fair amount of overspray on the board. The cleaning fluids most people use destroys the rubber seal on electrolytic capacitors over time.
Trying to service a PCB that has been sprayed isn't fun, and burning residues smell bad and can foul soldering iron tips. Not hard to clean off, but given a choice I'd rather work on units that haven't been poked at. Besides, gentle pushing on boards and components is a better way to find intermittent problems.
The only application methods for using cleaners on plugs and sockets is either with a "Q-Tip" or syringe. That way the quantity and location of the fluid can be controlled. There is also a good reason why alcohol is the cleaner of choice in calibration labs.
-Chris
On the bench, the unit is under more controlled circumstances. Careful tapping and signal tracing finds most issues. There could be a cracked solder on the PCB as well. Cleaning solvents tend to wet up the legs of capacitors and some transistors. Sprays are poorly controlled and there tends to be a fair amount of overspray on the board. The cleaning fluids most people use destroys the rubber seal on electrolytic capacitors over time.
Trying to service a PCB that has been sprayed isn't fun, and burning residues smell bad and can foul soldering iron tips. Not hard to clean off, but given a choice I'd rather work on units that haven't been poked at. Besides, gentle pushing on boards and components is a better way to find intermittent problems.
The only application methods for using cleaners on plugs and sockets is either with a "Q-Tip" or syringe. That way the quantity and location of the fluid can be controlled. There is also a good reason why alcohol is the cleaner of choice in calibration labs.
-Chris
My posts were context-specific. That is, Riverman built the amp, so I assume he is competent enough to not spray a board willy-nilly with contact cleaner. I also figured having just moved, his "bench" would be a kitchen table or something, and his house is full of boxes to unpack. The last thing I would want to do in this situation is go through a preamp with a scope etc. to find a fault that might well be fixed with a "McGiver" mentality. That is, think about what may have gone wrong and focus on that, then if that does not work, go to a second choice if there is one, then once stumped, go through the circuit thoroughly, starting with the power supply, (both channels are diminished), or anything else that would be in common with both channels being bad.
This all reminds me of the great story Richard Feynman tells about his childhood experience fixing a radio, titled "He fixes radios by thinking!". There is an intuitive way to approach a repair -- this works for some people, but not for others.
The down-side of the context-based approach to posts, is that someone else may see my reply, and with less experience, cause some problems that you mention, or they just don't prefer an intuitive approach to things, and would rather be completely systematic about it.
This all reminds me of the great story Richard Feynman tells about his childhood experience fixing a radio, titled "He fixes radios by thinking!". There is an intuitive way to approach a repair -- this works for some people, but not for others.
The down-side of the context-based approach to posts, is that someone else may see my reply, and with less experience, cause some problems that you mention, or they just don't prefer an intuitive approach to things, and would rather be completely systematic about it.
Hi mmerig,
About contact cleaners. Most are supplied in pressurized cans. This will cause a lot of overspray, and even I can be surprised when the contents comes out at far higher volumes than I intend. For cables and contacts (relays), I use the back of white business cards coated with the fluid of choice, or a "Q-Tip". This is simply the only way to control where the fluid goes for certain. Wouldn't it be nice if you could have precise control of spray cans? We can't to the degree required. Of course you can make damns to block overspray with something absorbent downhill to catch the excess.
One of the big problems with spray chemicals is that they work slowly on other components. You might not see the damage until some years pass. Then it is doubtful you will connect the two events. Of course, my favorite is the trimmer capacitor with chemical in it. Detunes varying with temperature. Lovely. This is often what is on/in a tuning capacitor that drifts. I have to wash many out. The trimmers usually need to be replaced, or taken completely apart to be cleaned properly.
I hate cleaning up after other technicians, never mind well meaning individuals who ask "how hard can it be"? Electrolytic capacitors with rubber seals are particularly vulnerable to chemicals like WD-40 and anything else that will attack rubber. Some transistors can be damaged as some chemicals may creep up the lead, through the encapsulant and onto the die. That process normally takes years, but a studio tech I know had a Neve console that was cleaned card by card. The next year was marked by strip after strip failing and failing again. Eventually he just ordered new capacitors and transistors and replaced them all. I really felt bad for him, but his experience puts an exclamation mark on what I have said here.
There are good reasons why high reliability technicians work the way they do. May sa well take their lead and do some things the same way. If you're keeping the equipment long term, it would pay to work carefully - and think!
-Chris
These posts will be read by lurkers, those who never post, and by others for years to come. You have to keep that in mind at all times. In addition, never assume anything about someone's expertise and comfort level. Ask first and post accordingly. I tend to assume completely unskilled people will read these posts, so I try to write down to the basics. For this I have been called condescending by folks who know at least some of the subject matter. Where's the balance? If I write as I would to a colleague, I lose most average people. So it seems best to write assuming as little as possible.
About contact cleaners. Most are supplied in pressurized cans. This will cause a lot of overspray, and even I can be surprised when the contents comes out at far higher volumes than I intend. For cables and contacts (relays), I use the back of white business cards coated with the fluid of choice, or a "Q-Tip". This is simply the only way to control where the fluid goes for certain. Wouldn't it be nice if you could have precise control of spray cans? We can't to the degree required. Of course you can make damns to block overspray with something absorbent downhill to catch the excess.
One of the big problems with spray chemicals is that they work slowly on other components. You might not see the damage until some years pass. Then it is doubtful you will connect the two events. Of course, my favorite is the trimmer capacitor with chemical in it. Detunes varying with temperature. Lovely. This is often what is on/in a tuning capacitor that drifts. I have to wash many out. The trimmers usually need to be replaced, or taken completely apart to be cleaned properly.
I hate cleaning up after other technicians, never mind well meaning individuals who ask "how hard can it be"? Electrolytic capacitors with rubber seals are particularly vulnerable to chemicals like WD-40 and anything else that will attack rubber. Some transistors can be damaged as some chemicals may creep up the lead, through the encapsulant and onto the die. That process normally takes years, but a studio tech I know had a Neve console that was cleaned card by card. The next year was marked by strip after strip failing and failing again. Eventually he just ordered new capacitors and transistors and replaced them all. I really felt bad for him, but his experience puts an exclamation mark on what I have said here.
There are good reasons why high reliability technicians work the way they do. May sa well take their lead and do some things the same way. If you're keeping the equipment long term, it would pay to work carefully - and think!
-Chris