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Old 21st April 2009, 01:17 AM   #1
db5owat is offline db5owat  United States
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Default Hafler DH 200 musical concepts mod

Several years ago I built this amp and later did a MC kit mod. I just noticed the other day that the right speaker was lacking the usual bass and was also lacking bass as compared to the other speaker. I traced the problem to the right amp output.

I can follow directions and build a kit but I have no training beyond that!

My question:

How do I proceed in determining what's wrong inside this amp related to the right side output that would effect bass but not other frequencies? Is there something relatively obvious that this points to? I appreciate any advice.

Dave
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Old 21st April 2009, 03:38 AM   #2
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Default Re: Hafler DH 200 musical concepts mod

Quote:
Originally posted by db5owat
Several years ago I built this amp and later did a MC kit mod. I just noticed the other day that the right speaker was lacking the usual bass and was also lacking bass as compared to the other speaker. I traced the problem to the right amp output.

I can follow directions and build a kit but I have no training beyond that!

My question:

How do I proceed in determining what's wrong inside this amp related to the right side output that would effect bass but not other frequencies? Is there something relatively obvious that this points to? I appreciate any advice.

Dave
Hi Dave,

I'd start by making sure all of the internal connections are still solid. This is the most likely weak point to surface over time with a kit product. Next I'd suspect an electrolytic cap has gone bad. You can look at them and see if the ones in the right channel look different than the left. They will normally look like the plastic sleeve around the aluminum can has shrunk. I believe the stock amp had a few in circuit locations that would do exactly what you describe, although I'm not sure what the modded kit had.

The electrolytic caps have an electrolytic fluid in them that will dry up with time and the cap's value drops dramatically and the response will frequency response suffer (they will also run hot and shrink the plastic sleeve). A wholesale replacement of the caps is a straight forward thing that should be do able if you built the kit.

This assumes the music coming from the channel is not distorted and the channel is not showing any other issues like running really cold or hot relative to the other.

Just a few thoughts,

Philip.
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Old 27th April 2009, 11:27 PM   #3
db5owat is offline db5owat  United States
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Philip- thank you for the response. It will take awhile before I can work on this amp. I did take it apart for visual inspection. Nothing seemed "out of place". How does one go about testing each electrolytic capacitor to see if it is the offending one? I'm a real novice.
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