I finished recapping the DH110 daughterboard (4 caps total). The bang is still there when I push the Tone button in or out. I also found that the sound got really tinny and flat sounding. I may end up putting some different NP caps in there if these don't wake up. I found one more cap hidden on the motherboard below that switch card. Its a squat little 220uF 50V. I ordered a replacement in FG. Hopefully that'll be the end of the noise.
raycarr00
Super Member
if the bipolar caps were replaced(check for cross soldering),push button switches doused with cleaner and worked,pins that connect the small board to the large board cleaned...don't know. did replace that cap by installing it from the underside(was a pain to remove by unsoldering it whole,instead of cutting it in half,then unsoldering). another AK member working on the dh 110,ran it without that board installed. he did lower the volume and turned the pre on first,then the amp. good way to rule out the board as the issue. always turn the pre first then amp...keeps pre from activating it's volume control protection,or the transistors mentioned in this thread.
I think that little 22uF/50V cap is going to be the answer. With the card pulled out, the top two switches leave the board, along with all 4 of those NP caps. Of the two remaining switches that are still in place on the main board, the tone is one of them. I haven't traced out the circuit but I'm betting that cap is attached to the tone switch one way or another.
Yes, I ordered replacement J112 along with the voltage regulators and related diodes for about 20 cents each. And now I can't find them in my lab mess.
While you're here, I wanted to confirm something about those four odd caps by the bass and treble pots. I know we talked about this a couple weeks ago but I need to understand this a little better...
The cheese caps are polycarbonate, as are those weird SMD ones next to them. I replaced the big plastic Seacors at C19/119 (you used Mundorfs there) with ClarityCap PX series polypropylene in the appropriate value. I have two left - could I use those to replace the cheese polycarbonate?
Also, I managed to get Tropical Fish in 47nF (0.047uF) 250V - those are metalized polyester, so are you certain those would be appropriate replacing those SMD polycarbonates? I don't want to do all that work to end up changing the sound for the worse.
I'm thinking about starting a separate thread regarding these replacements to get some more eyes and opinions on it. Like I said, I want to understand it.
While you're here, I wanted to confirm something about those four odd caps by the bass and treble pots. I know we talked about this a couple weeks ago but I need to understand this a little better...
The cheese caps are polycarbonate, as are those weird SMD ones next to them. I replaced the big plastic Seacors at C19/119 (you used Mundorfs there) with ClarityCap PX series polypropylene in the appropriate value. I have two left - could I use those to replace the cheese polycarbonate?
Also, I managed to get Tropical Fish in 47nF (0.047uF) 250V - those are metalized polyester, so are you certain those would be appropriate replacing those SMD polycarbonates? I don't want to do all that work to end up changing the sound for the worse.
I'm thinking about starting a separate thread regarding these replacements to get some more eyes and opinions on it. Like I said, I want to understand it.
raycarr00
Super Member
the "cheese" caps are bipolar;just use bipolar and listen to see if they're to your liking. I used Tropical fish there(had some left over)and the sound was accentuated.
you have the dh 110 with the SMD caps-I would leave them. I had a channel go out on one of my SMD versions of the DH 110 when I tried replacing them with poly caps. they're SMD plus a resistor (on the large ones in the center board). don't see them in your version. smaller ones by the "Cheese" caps. you can remove them and test them. they test just like any other cap.
If you want to replace them,add the resistor if it had a resistor.
yes,start a thread.
you have the dh 110 with the SMD caps-I would leave them. I had a channel go out on one of my SMD versions of the DH 110 when I tried replacing them with poly caps. they're SMD plus a resistor (on the large ones in the center board). don't see them in your version. smaller ones by the "Cheese" caps. you can remove them and test them. they test just like any other cap.
If you want to replace them,add the resistor if it had a resistor.
yes,start a thread.
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I've now replaced all the NP caps on the daughtercard, plus that 220uF 50V cap hidden underneath it. I cleaned the spikes underneath the card and put F5 on them and did a final wipedown. I also dribbled some F5 into the tone switch and worked it furiously to get that to soak in.
I had the DH110 up and running just now. Initially the tone switch gave the barest pop - acceptable for a 35 year-old switch - but after working it a few times it started getting noisy to the point where I thought I'd blown the speakers again. This switch has to go. I have no idea where to even look.
Any ideas out there?
I had the DH110 up and running just now. Initially the tone switch gave the barest pop - acceptable for a 35 year-old switch - but after working it a few times it started getting noisy to the point where I thought I'd blown the speakers again. This switch has to go. I have no idea where to even look.
Any ideas out there?
This switch isn't noisy, Ray, I think its got a bad contact inside that is somehow passing DC to the audio path. The bang that comes out of it when I use it could wake up a bag of concrete.
raycarr00
Super Member
same thing happened to me when a pin had been missed on the board and ribbon cables. check that all the pins are inserted into board...easy to miss one(push them with a pen as board's inserted). same with ribbon cables. dh110 functions without board...turn preamp on,volume down,finally turn on amp. see if symptom persists.
I was very careful with adding the board back in, and all the ribbon cables are installed.
Not yet. I've been doing home stuff. Maybe I'll get to it today, but I still have to deal with that bad switch.
Unfortunately with the turn of the year, all the cap sales seem to have dried up.
I've put the new caps into service. I then tried a tactic to get rid of the switch noise - I heated up the switch lead solder joints one by one and worked the switch while I did that.
The preamp is now playing and the switch noise is going. However, I have tremendous distortion through the preamp now. Picture an amp without speaker protection relays: play a CD through it, turn off the amp, and listen to the music as the supply caps bleed down. (On my GFA-555 this lasts for almost 30 seconds). When you get near the end of the charge the music starts to break up. Thats what preamp sounds like now.
I doubt its the new layered .047uF caps. Those are most likely there to bypass the .47uF next to them. I think its the switch, since its for tone.
I'm going to get a new switch, I'm tired of fighting this one.
The preamp is now playing and the switch noise is going. However, I have tremendous distortion through the preamp now. Picture an amp without speaker protection relays: play a CD through it, turn off the amp, and listen to the music as the supply caps bleed down. (On my GFA-555 this lasts for almost 30 seconds). When you get near the end of the charge the music starts to break up. Thats what preamp sounds like now.
I doubt its the new layered .047uF caps. Those are most likely there to bypass the .47uF next to them. I think its the switch, since its for tone.
I'm going to get a new switch, I'm tired of fighting this one.
raycarr00
Super Member
good idea on solder heating the pins. did you try playing the pre without the entire switch assembly? prior post suggests to turn pre on first and then the amp. eliminating the entire switch assembly bypasses the muting transistors, caps, etc.,as the culprit and if issue persists. I wonder if one of those caps on the switch board is bad...hmm. 
inquiring minds want to know.
inquiring minds want to know.