I would appreciate it if someone could help with my problem. My son was cranking his Hafler amp and blew the internal fuses. I replaced all the blown fuses including the ones that protect the speakers. Both channels play but the right is distorted. I checked the bias and it is only 20ma. When the amp is first turned on the reading is 240ma then quickly drops to 20ma. I checked Q9 in the bias circuit and it's ok. Any ideas what could be causing this problem?
As you troubleshoot this channel are you monitoring it for DC offset?
You could swap the MOSFETs from one channel to the other to rule out a problem with them.
What color are your circuit cards?. The earlier version has phenolic cards that could not withstand a very high temperature in the solder bath upon construction. Heating and cooling over time may have caused tiny breaks in continuity where some components are soldered. Try reflowing solder on all joints on the back of the circuit card, especially the pre-driver and driver transistors.
After all of this you may have to begin checking and/or replacing pre-driver and driver transistors.
And, I assume you have tried to rotate P1 while monitoring bias setting. Did you replace Q9 or just pull and check it? It will not control the bias circuit if its hFe is too low.
You could swap the MOSFETs from one channel to the other to rule out a problem with them.
What color are your circuit cards?. The earlier version has phenolic cards that could not withstand a very high temperature in the solder bath upon construction. Heating and cooling over time may have caused tiny breaks in continuity where some components are soldered. Try reflowing solder on all joints on the back of the circuit card, especially the pre-driver and driver transistors.
After all of this you may have to begin checking and/or replacing pre-driver and driver transistors.
And, I assume you have tried to rotate P1 while monitoring bias setting. Did you replace Q9 or just pull and check it? It will not control the bias circuit if its hFe is too low.
DH-200 Bias
Let us know how you are doing on your problem.
Did swapping MOSFETs from one channel to the other make a difference? Did you re-flow solder to all the connections on the back side of the circuit card?
I know from experience that those phenolic cards became a problem over the years and re-soldering everything solved a very similar problem for me with an old DH-200 amp.
Let us know how you are doing on your problem.
Did swapping MOSFETs from one channel to the other make a difference? Did you re-flow solder to all the connections on the back side of the circuit card?
I know from experience that those phenolic cards became a problem over the years and re-soldering everything solved a very similar problem for me with an old DH-200 amp.
Q12 and Q13
I have been told that those driver transistors are a common cause of failure.
What value of fuses are in the fuse blocks on the back panel? If a 2 or 3 amp fuse is placed there they will often blow before the amp is damaged.
How do you check these transistors? I assume you remove them? How do you unsolder these little guys? Do you have a solder sucker? My soldering skills and equipment are not that good but maybe I can improve.
Good luck.
Dick
I have been told that those driver transistors are a common cause of failure.
What value of fuses are in the fuse blocks on the back panel? If a 2 or 3 amp fuse is placed there they will often blow before the amp is damaged.
How do you check these transistors? I assume you remove them? How do you unsolder these little guys? Do you have a solder sucker? My soldering skills and equipment are not that good but maybe I can improve.
Good luck.
Dick
"The filter caps are bad. I'm thinking that they may not have gotten that way on their own."
Strictly a function of heat vs time.
You can:
Buy 105* caps instead of 85* caps
Or:
Get bigger caps
(in general, ripple current ratings follow the physical SIZE of the can, the more surface area, the higher the rated current)
Strictly a function of heat vs time.
You can:
Buy 105* caps instead of 85* caps
Or:
Get bigger caps
(in general, ripple current ratings follow the physical SIZE of the can, the more surface area, the higher the rated current)
Hi Terry,
Buy new capacitors firstly. Try any electronic parts jobber in your area, or Digikey, Newark Elecronics. There are more. These will cost some money.
Are the vents "popped", or do you have excessive ripple? Djk is right in that 105 degree caps may last longer. The 85 degree types should be okay in there. Just make sure the ventillation for the amp is enough to keep it running cool - ish.
-Chris
Buy new capacitors firstly. Try any electronic parts jobber in your area, or Digikey, Newark Elecronics. There are more. These will cost some money.
Are the vents "popped", or do you have excessive ripple? Djk is right in that 105 degree caps may last longer. The 85 degree types should be okay in there. Just make sure the ventillation for the amp is enough to keep it running cool - ish.
-Chris
"I am in the process of trying to fix my P230's. The filter caps are bad. I'm thinking that they may not have gotten that way on their own. Where can I find new MOSFETs if I need them?"
http://www.profusionplc.com/product-frame.htm
Hafler DH200/220 used the 10N16, 10P16 after Hitachi discontinued the 2sk135 & 2sj50
I think your amp uses the plastic TO247 case ECX10N16, 10P16 only $4.89 in 20 lot, or $8.94 in qty 2
Try apex jr for inexpensive snap-in caps:
http://www.apexjr.com/capacitorsR.html
10,000Mfd
80V
Snap-In 1 3/8" X 3 1/8" Nichicon $3.95
http://www.profusionplc.com/product-frame.htm
Hafler DH200/220 used the 10N16, 10P16 after Hitachi discontinued the 2sk135 & 2sj50
I think your amp uses the plastic TO247 case ECX10N16, 10P16 only $4.89 in 20 lot, or $8.94 in qty 2
Try apex jr for inexpensive snap-in caps:
http://www.apexjr.com/capacitorsR.html
10,000Mfd
80V
Snap-In 1 3/8" X 3 1/8" Nichicon $3.95
anatech said:
Hi Chris,
No The vents aren't popped, but of the four caps in the two amps I have, one cap reads 65.3 VDC+ and 0 VAC and the other three read 42.6VDC+/-, 19.8VAC. This is basically what the leads read when disconnected from the caps altogether, so that tells me that the three are probably dust. Hope I'm right and not just throwing away another $60.
I ended up ordering these caps. A bit more expensive than the Nichicon caps that djk linked to, but they are the same size physically as the ones that are in there now.
djk,
Thanks for the help. The MOSFETs in the P230 are 2SK134 and 2SJ49. They are not plastic, but metal. Looks like the ECF models are what I would need. Is there a way to check these with a multimeter to tell if they are bad or not? I wouldn't mind finding out before I hook up the new caps. I don't know how to test MOSFETs.
Thanks, Terry
If MOSFETs are paralleled they must be matched on VGS. I'm not too technical but I believe one uses a curve tracer.
I have an original Hafler MOSFET checker that allows go/nogo checking of a device and of matching it to another. You can see on the TO-3 cans a stenciled number, which is the Hafler grade number. Hafler matched these devices within 10% of each other. If they are not matched one device will hog all the power and try to do all the work. These devices must be matched.
Then, even a good device may be "leaky." There is a routine to check a device for leakiness and the routine uses a DVM. I don't have the instructions to this test handy but I believe they have been posted somewhere. Perhaps some gentle reader here will point us to the link.
As for PS caps. Yours seem to be leaky. Put something like a 1000 ohm resistor in series with the voltage in to a cap. Charge it up and measure the voltage drop across the resistor to get a measure of how leaky the power cap is.
I have an original Hafler MOSFET checker that allows go/nogo checking of a device and of matching it to another. You can see on the TO-3 cans a stenciled number, which is the Hafler grade number. Hafler matched these devices within 10% of each other. If they are not matched one device will hog all the power and try to do all the work. These devices must be matched.
Then, even a good device may be "leaky." There is a routine to check a device for leakiness and the routine uses a DVM. I don't have the instructions to this test handy but I believe they have been posted somewhere. Perhaps some gentle reader here will point us to the link.
As for PS caps. Yours seem to be leaky. Put something like a 1000 ohm resistor in series with the voltage in to a cap. Charge it up and measure the voltage drop across the resistor to get a measure of how leaky the power cap is.
Hi Terry,
You are correct. Those caps are toast. Replacing all four is the right way to do this. Keep the good one for experimenting. Sprague makes good parts, these should last.
Nelson Pass has good instructions on his web site for testing mosfets. I put groups of four on the same heatsink and measure the Vgs at the same current in all. I used 1 Ohm as the current sense resistor. You end up with the ones you wish to match on the same heatsink to keep them at a similar temperature. This makes a difference. Leave them mounted on the heatsink and make your own connections to them. Any defective ones will have vastly different Drain current Vgs characteristics than good units. I apply 20 -50 VDC to the group as this is more realistic of the operating conditions. Leakage will show up here.
-Chris
You are correct. Those caps are toast. Replacing all four is the right way to do this. Keep the good one for experimenting. Sprague makes good parts, these should last.
Nelson Pass has good instructions on his web site for testing mosfets. I put groups of four on the same heatsink and measure the Vgs at the same current in all. I used 1 Ohm as the current sense resistor. You end up with the ones you wish to match on the same heatsink to keep them at a similar temperature. This makes a difference. Leave them mounted on the heatsink and make your own connections to them. Any defective ones will have vastly different Drain current Vgs characteristics than good units. I apply 20 -50 VDC to the group as this is more realistic of the operating conditions. Leakage will show up here.
-Chris
Be careful of what anatech said. Nelson Pass uses vertical mosfets instead of the lateral mosfets used by Hitachi. They are not the exact same item and require different testing voltages. I don't know the exact technical particulars but my EE guru has warned about confusing the two types. If you do a search in the SS forum you can turn up some discussion about the differences between lateral and vertical MOSFETs.
Hope this helps.
Hope this helps.
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