Hi. I recently obtained a Hafler 110 preamp from a friend who had not used it in years. I am not getting any sound from the right channel. I also tried my headphones without the amplifier(DH 120)on, and I only had sound from the left side. Does this tell me it is definitely the preamp? What are the most likely causes? Thanks
Here's a good start
you may already have it, but here's a link to the manual, including schematics:
http://www.hafler.com/techsupport/pdf/DH-110_preamp_man.pdf
you may already have it, but here's a link to the manual, including schematics:
http://www.hafler.com/techsupport/pdf/DH-110_preamp_man.pdf
Hi I have done some repair works on such preamp some years ago and there was heavily oxidated selector switch....if you can buy new,replace it if not try with some contact spray but it will solve problem just temporary....and there is also possible that some pot is breaking too. And more. It is also possible that there you have dry or defective cap. There is a lot of tantals in signal path and also some other electrolytics on tone control circuit and psu.... Regards and good luck
There are no Tantalum caps in this preamp as far as I can remember, but there are many aluminum electrolytics that go bad. Mine had issues in the mute timing circuit, C39 and C40, and I do think one of the mute FETs went bad also. I just pulled the FETs and the output thump was not that bad, but most of my power amps mute on power up anyway so I'm not sure how bad the preamp is.
I changed all the caps in the line stage, and would do the phono section also if I used it. Note that many of the electros are non-polar types which are not so common.
I changed all the caps in the line stage, and would do the phono section also if I used it. Note that many of the electros are non-polar types which are not so common.
Thanks for your input Pete. I just wish I knew more about this stuff. I had a very knowledgeable friend who suddenly past away last year. This would be childsplay for him.OH well,onward.
Very sorry to hear about your friend. Just ask away here and we'll try to help.
I purchased this at an Audio Show on Long Island in 1980 (I believe). Since that time it was used by 2 of my sons -- and came back owing to bad RCA's --- found another problem at the same time:
Fixed:
New Input connectors:
Will probably replace the floating LM317/337 regulators and install a ground loop breaker. The main input board ground is connected to the chassis at the phono inputs which will have to change as well.
An externally hosted image should be here but it was not working when we last tested it.
Fixed:
An externally hosted image should be here but it was not working when we last tested it.
New Input connectors:
An externally hosted image should be here but it was not working when we last tested it.
Will probably replace the floating LM317/337 regulators and install a ground loop breaker. The main input board ground is connected to the chassis at the phono inputs which will have to change as well.
Just got done putting in the LT1963A -- this part required a bit of fudging as it's 20V max -- so the ground leg is lifted with 2 green LED's and a zener replaces the first power divider resistor to yield 23.2V:
An externally hosted image should be here but it was not working when we last tested it.
I used similar rca sockets but mibe were gold . They came from Digikey or Mouser.
Most important change the muting jfets or just remove them as I did since I had so much trouble with them.
The worst problem of all is dirty or oxidized switches, get some Cramolin DE-OXIT.
sound wize replacing the cheap crap electrolytics on the output to some aerovox polypropylene caps was astoundimg!
Most important change the muting jfets or just remove them as I did since I had so much trouble with them.
The worst problem of all is dirty or oxidized switches, get some Cramolin DE-OXIT.
sound wize replacing the cheap crap electrolytics on the output to some aerovox polypropylene caps was astoundimg!
I didn't know Aerovox made a PP cap that big.
The problem with the output stage coupling caps may be that it has the dual purpose of driving a pair of low-Z headphones. I'd suggest that 4.7uF/50V film cap would drive a 10K z-in load just fine, and use a HV opamp (OPA551) for the cans.
The problem with the output stage coupling caps may be that it has the dual purpose of driving a pair of low-Z headphones. I'd suggest that 4.7uF/50V film cap would drive a 10K z-in load just fine, and use a HV opamp (OPA551) for the cans.
modern hot input levels to older gear
Modern CD players put out larger peak to peak line level voltages than older gear like my Halfler DH-110 is used to seeing..... I think. My Oppo disk player has a volume control. If it is up all the way my Hafler DH-110 distorts badly.
Modern CD players put out larger peak to peak line level voltages than older gear like my Halfler DH-110 is used to seeing..... I think. My Oppo disk player has a volume control. If it is up all the way my Hafler DH-110 distorts badly.
Modern CD players put out larger peak to peak line level voltages than older gear like my Halfler DH-110 is used to seeing..... I think. My Oppo disk player has a volume control. If it is up all the way my Hafler DH-110 distorts badly.
Hmmm you shoud not be having a problem with the Oppo . The 110 has a pretty hefty output swing and the input overload level is pretty high as well. Once again I would suspect those pesky muting FET's, try pull them out and see if your distortion goes away.
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