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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Hafler DH101 noise
Recently only one channel my preamp started having random crackle and pop noises. The music on this channel also sounds distorted when the crackle and pop noises are present. The noise is only intermittent.
The noise is not affected by the signel source, dub and mono switches, the balance and volume knobs nor the tone switch/settings. The functional block diagram on page 21 of the Hafler manual shows only the high level gain stage and the dc feedback sections as unaffected by all of these controls. Can anyone suggest where to look / test for the source of these noises? The manual is available on line at http://www.hafler.com/techsupport/index.asp?ID=3 Thanks for any help. |
#2
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I had a problem with the right channel of my Hafler DH-110 fading out, or
disappearing altogether. A good cleaning of the wire connectors INSIDE the preamp fixed the problem and now it sounds great! I don't know if the DH-101 has similar heavy internal ribbon cables. Search the Vintage Forum at audioasylum.com. I found help at http://db.audioasylum.com/cgi/m.mpl?...ms&r=&session= Best of luck. jjhnsn |
#3
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ttworld wrote: Recently only one channel my preamp started having random crackle and pop noises. The music on this channel also sounds distorted when the crackle and pop noises are present. The noise is only intermittent. The noise is not affected by the signel source, dub and mono switches, the balance and volume knobs nor the tone switch/settings. The functional block diagram on page 21 of the Hafler manual shows only the high level gain stage and the dc feedback sections as unaffected by all of these controls. Can anyone suggest where to look / test for the source of these noises? The manual is available on line at http://www.hafler.com/techsupport/index.asp?ID=3 Thanks for any help. -- ttworld Loooking at the actual schematic on pages 12 & 13, it looks to me like the DC feedback path is through the Bass control. Does turning that control do anything with the crackles? You mentioned all the controls except the Bass and Treble controls. I haven't probed it but I would expect the Bass control to read 0 volts DC (give or take a few mV) on all 3 lugs with no signal. Electrolytic capacitors are the most frequent failures in old electronics. An ESR meter would detect them easily. I bought my DH-101 back in '79 in kit form. I haven't had any issues with it yet -- after only 26 years. I did modify it to convert the phono 1 position to a high level input for the CD player and hardwired the phono cartridge input directly to the phono preamp which still comes up as phono 2. Also altered the grounding by using a 5-way binding post for the ground wire from the turntable directly to the PCB rather than the chassis. Its a good unit if you like the minimalist approach to audio. Let us know what you find. GG |
#4
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The bass/treble knobs have no affect. The tone switch has no effect either.
Thank you for looking. |
#5
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ttworld wrote:
: Recently only one channel my preamp started having random crackle and : pop noises. The music on this channel also sounds distorted when the : crackle and pop noises are present. The noise is only intermittent. : The noise is not affected by the signel source, dub and mono switches, : the balance and volume knobs nor the tone switch/settings. : The functional block diagram on page 21 of the Hafler manual shows only : the high level gain stage and the dc feedback sections as unaffected by : all of these controls. : Can anyone suggest where to look / test for the source of these : noises? Have you tried posting your question on: www.dyiaudio.com Its a forum that has a lot of knowledgeable people that could help with your problem. |
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