Regulator problem
Dick, thanks for the posted schematics. The circuit is essentially very similar to the one I have put in my 2 DH-200 for years and they still work fine.
mmerig, your circuit is certainly different than the one posted by Dick since you have additional transformers. Are these transformers having small secondary voltage used to increase the main DH-220 transfo secondary voltage OR
are they high voltage secondary and not connected to the main DH-220 transfo secondary?
From the picture, I can not locate the rectifier bridge. Also the transfos size (power) seems a little bit small. You seem to have only one fuse on your board. Where is it connected? There should be a protection mean to avoid such dramatic failure...
After this sad event of damaging your pc-19 circuit, does the regulator circuit still works?
you seem to be skilled enough so I am confident that you will find the cause of the problem.
Good luck
Dick, thanks for the posted schematics. The circuit is essentially very similar to the one I have put in my 2 DH-200 for years and they still work fine.
mmerig, your circuit is certainly different than the one posted by Dick since you have additional transformers. Are these transformers having small secondary voltage used to increase the main DH-220 transfo secondary voltage OR
are they high voltage secondary and not connected to the main DH-220 transfo secondary?
From the picture, I can not locate the rectifier bridge. Also the transfos size (power) seems a little bit small. You seem to have only one fuse on your board. Where is it connected? There should be a protection mean to avoid such dramatic failure...
After this sad event of damaging your pc-19 circuit, does the regulator circuit still works?
you seem to be skilled enough so I am confident that you will find the cause of the problem.
Good luck
Mod boards
Hi Countzero,
These mods that adds to the stock DH-200 pcb are done on prototype universal boards from Radio Shack or else, that is why they are very cheap to try and experiment. However, I have also drawn some pcbs with these mods and others too and finally I do not like the newer mods I have done so I quit these pcb design.
Afterwards, I wanted to experiment with class A and the DH-200-220 chassis is kind of small. From calculations, I could not get enough heat dissipation with the DH-200 chassis to make it work in class A to get a reasonable power ( I like loud listening...). I have decided to design and build a complete new jumbo amp with new chassis, power supply (2 x 500 VA), big caps, new pcb design based on the DH-200-220-500 topology but including the mods that I liked in my DH-200 amps and then interfacing with Erno's Borbely output board pcb to drive 5 pairs of Lateral mosfet per polarity. This gives about 15-20 W rms in class A (8 ohms) and about 70W rms class AB in 8 ohms. Most of the time I only listen to level which are still in class A (15W is loud in a living room) but I have some power reserve for other occasions when I want it louder!
I have already sent documentation by e-mail to several posters since sone information about the mods are not of the best quality or complete enough to be posted here...What mod would you try?
Remember that one of these mods (input circuit) is coming from an active patent so it can not be used comercially...
Countzero said:
Hi Countzero,
These mods that adds to the stock DH-200 pcb are done on prototype universal boards from Radio Shack or else, that is why they are very cheap to try and experiment. However, I have also drawn some pcbs with these mods and others too and finally I do not like the newer mods I have done so I quit these pcb design.
Afterwards, I wanted to experiment with class A and the DH-200-220 chassis is kind of small. From calculations, I could not get enough heat dissipation with the DH-200 chassis to make it work in class A to get a reasonable power ( I like loud listening...). I have decided to design and build a complete new jumbo amp with new chassis, power supply (2 x 500 VA), big caps, new pcb design based on the DH-200-220-500 topology but including the mods that I liked in my DH-200 amps and then interfacing with Erno's Borbely output board pcb to drive 5 pairs of Lateral mosfet per polarity. This gives about 15-20 W rms in class A (8 ohms) and about 70W rms class AB in 8 ohms. Most of the time I only listen to level which are still in class A (15W is loud in a living room) but I have some power reserve for other occasions when I want it louder!
I have already sent documentation by e-mail to several posters since sone information about the mods are not of the best quality or complete enough to be posted here...What mod would you try?
Remember that one of these mods (input circuit) is coming from an active patent so it can not be used comercially...
try this -- instead of the 1N4759 used in the article substitute a potentiometer (or 13K resistor) -- place a 1N4752 (33 BV) across the LM317 instead of a 1N4007 -- this will limit the max voltage across the LM317 to 33V. You have thus created a "kinda" MAIDA regulator. You might also want to put a resistor in series with the circuit (as shown below) to limit the discharge current through it.
Recall that the original article specified either an 1N4759 OR a 25K, 25 turn trimpot -- but without a device to limit the voltage across the LM317 I can see cause for tears.
Here's a hint from SY -- consider putting a 4.7 ohm resistor in series with the C7 and C8 output filter caps on the regulator boards.
I haven't done this to my DH-220, but have simmed it. You should be able to squeeze all the components onto the existing boards.
Recall that the original article specified either an 1N4759 OR a 25K, 25 turn trimpot -- but without a device to limit the voltage across the LM317 I can see cause for tears.
Here's a hint from SY -- consider putting a 4.7 ohm resistor in series with the C7 and C8 output filter caps on the regulator boards.
I haven't done this to my DH-220, but have simmed it. You should be able to squeeze all the components onto the existing boards.
An externally hosted image should be here but it was not working when we last tested it.
Hello FAB
The circuit I built is very similar to the circuit that Dick posted, which is out of the AA article. All I did was make the regulator more compact.
Dick's post shows a transformer above the main circuit, and this transformer is separate from the main DH220 transformer. It is a Triad FP 120-100 (see parts list, 3rd item down on right column). The rating is 12VA, 120 VAC out at 0.1A, center tapped.
In the picture the rectifier bridge is the grayish rectangle centered between the transformer and its big caps and the rest of the circuit beginning with the black filter caps with white letters. (This desciption is for one channel).
The fuse is in series with the transformer input. The original design had one fuse for each channel. Mine has one fuse for both channels.
The regulator still works.
It will be about a week before I get back to the VR/PC19 problem.
The circuit I built is very similar to the circuit that Dick posted, which is out of the AA article. All I did was make the regulator more compact.
Dick's post shows a transformer above the main circuit, and this transformer is separate from the main DH220 transformer. It is a Triad FP 120-100 (see parts list, 3rd item down on right column). The rating is 12VA, 120 VAC out at 0.1A, center tapped.
In the picture the rectifier bridge is the grayish rectangle centered between the transformer and its big caps and the rest of the circuit beginning with the black filter caps with white letters. (This desciption is for one channel).
The fuse is in series with the transformer input. The original design had one fuse for each channel. Mine has one fuse for both channels.
The regulator still works.
It will be about a week before I get back to the VR/PC19 problem.
Hello jakinnj:
I mildy suspected that there could have been a voltage surge through the regulator that damaged some transistors on the PC19, but thought with all of those capactors on the regulator, this was unlikely. I am stll very new at this, and rely more measurements than theory or simulations. I will try and see if there is a surge at turn-on before I put in your modifications.
Thanks very much.
I mildy suspected that there could have been a voltage surge through the regulator that damaged some transistors on the PC19, but thought with all of those capactors on the regulator, this was unlikely. I am stll very new at this, and rely more measurements than theory or simulations. I will try and see if there is a surge at turn-on before I put in your modifications.
Thanks very much.
jakinnj,
The way you guys SIM a circuit amazes me. I'm not an EE but your additions, especially the zener across the VR chip, sure make sense to this long time dabbler. Thanks.
What does MAIDA stand for?
What effect will "putting a 4.7 ohm resistor in series with the C7 and C8" have on performance of the regulator?
Thanks....
The way you guys SIM a circuit amazes me. I'm not an EE but your additions, especially the zener across the VR chip, sure make sense to this long time dabbler. Thanks.
What does MAIDA stand for?
What effect will "putting a 4.7 ohm resistor in series with the C7 and C8" have on performance of the regulator?
Thanks....
Another question:
How important is it to have "dual mono" regulators? Why not just just one VR for both channels? Will the voltage demands of one channel modulate the voltage to the other channel? I thought the circuit cards operate in Class A and their voltage/current demands remain very steady. Therefore, on VR for both could be a way of simplifying the mod.
Just a thought...........
How important is it to have "dual mono" regulators? Why not just just one VR for both channels? Will the voltage demands of one channel modulate the voltage to the other channel? I thought the circuit cards operate in Class A and their voltage/current demands remain very steady. Therefore, on VR for both could be a way of simplifying the mod.
Just a thought...........
Dick West said:
Here's a link to Maida's Application Note (LB-47, 1980):
http://www.national.com/an/LB/LB-47.pdf#page=1
This is what the "real" Maida regulator looks like -- the Darlington pair stand off the full power supply voltage while the LM317 just seek the drop across the zener. Note that this will help with ripple elimination, but it isn't going to be that great for power supplies with wide variation. It is an improvement over the Staggs article from TAA (even though it was written 13 years prior.)
The 4.7 or 2.7 ohm resistor corrects for the inductance in the power supply capacitor -- so you get a lower overall impedance -- and no ringing from the RLC circuit. when I did the GB of the "Last PAS" regulator boards I incorporated it at SY's request.
An externally hosted image should be here but it was not working when we last tested it.
regulator problem
mmerig
jackinnj circuit is probably an improvement but the circuit you are already using should do the job without normally damaging the pc-19 board (since plenty of peoples have used it so far). As you said, with the present capacitors and if your regulator circuit still works (fine with no additional ripple?) then the suspected voltage spike that might have occured was not that high or long enough to damage 160Vdc transistors in the pc-19 card.
Just a thought: are you sure your positive and negative grounds of your regulator are electrically connected (either together or via the star ground of the amp). Sometimes the multimeter probes do the connections during measurement and when the probes are not therw anymore...)?
mmerig
jackinnj circuit is probably an improvement but the circuit you are already using should do the job without normally damaging the pc-19 board (since plenty of peoples have used it so far). As you said, with the present capacitors and if your regulator circuit still works (fine with no additional ripple?) then the suspected voltage spike that might have occured was not that high or long enough to damage 160Vdc transistors in the pc-19 card.
Just a thought: are you sure your positive and negative grounds of your regulator are electrically connected (either together or via the star ground of the amp). Sometimes the multimeter probes do the connections during measurement and when the probes are not therw anymore...)?
Re: regulator problem
FAB -- I do suspect that a surge blew through some of the transistors.
If you examine the boards from the original article you'll see a problem -- (well, it's not a critical problem, just a big design booboo) -- the dreaded "ground plane" -- Walt Jung would spank them for this. (In Walt's absence, perhaps Janneman would do the honors.)
The wiring in the unmodified Haflers was the among the first issues tackled.
fab said:
FAB -- I do suspect that a surge blew through some of the transistors.
If you examine the boards from the original article you'll see a problem -- (well, it's not a critical problem, just a big design booboo) -- the dreaded "ground plane" -- Walt Jung would spank them for this. (In Walt's absence, perhaps Janneman would do the honors.)
The wiring in the unmodified Haflers was the among the first issues tackled.
Attachments
jakinnj,
But, even if the transformer presents a momentary surge at turn on wouldn't the following regulator impede it?
Also, are two VR circuits required for a stereo amp? Why not use just one? Would the load variation caused by one channel also show up in the other channel's electrical supply?
But, even if the transformer presents a momentary surge at turn on wouldn't the following regulator impede it?
Also, are two VR circuits required for a stereo amp? Why not use just one? Would the load variation caused by one channel also show up in the other channel's electrical supply?
A turn-on surge seems to be the most likely reason for damage, but I don't see it on either rail with an analog meter, but a little blip (maybe 100 volts- hard to tell) shows up on a DMM. The surge may be too fast for me to measure.
Is a ground plane so bad on a board carrying only DC?
In a week I shoud be able to work on it.
Thanks for all of the advice. I'll try jakinnj's suggestions.
Is a ground plane so bad on a board carrying only DC?
In a week I shoud be able to work on it.
Thanks for all of the advice. I'll try jakinnj's suggestions.
a regulator is a voltage reference, control device (pass transistor) and error amplifier. the regulator has to first (in analog) calculate the error and correct bias to the pass transistor -- so that first cycle is like corn going through a goose.
your transistors should be able to take some surge beyond their ratings -- but not for very long indeed.
your transistors should be able to take some surge beyond their ratings -- but not for very long indeed.
What do I have here.... DH-220 mods by Musical Concepts... to what extent?
I'm new to diyaudio, so please forgive my ignorance. I was out at garage sales this weekend and I picked up a Hafler DH-220. The cover panel also has a Musical Concepts modifications tag on it. It looks to be heavily modified and I was hoping that someone could tell me what I found? It looks to have a large Toroidal (circular coil) Transformer and four large capacitors versus the square transformer and two capacitors in the owner's manual.
Currently neither channel is working, but the left channel was working before my RCA inputs must have loosened up the left post. I noticed that the musicap on the capacitor rail has a burn on it where wire enters the musicap (Part C-2816 1.0 +/- 10% 200V MCPP105KC Musicap).... anyone know where I could get more of these?
I was going to post some jpegs of the amp w/o the cover on, but my files are too large. Email me and I will send you the pictures or put them online.
Can someone recommend some troubleshooting steps that I can try? All the fuses are fine, but the musicap does need replaced.
I'm new to diyaudio, so please forgive my ignorance. I was out at garage sales this weekend and I picked up a Hafler DH-220. The cover panel also has a Musical Concepts modifications tag on it. It looks to be heavily modified and I was hoping that someone could tell me what I found? It looks to have a large Toroidal (circular coil) Transformer and four large capacitors versus the square transformer and two capacitors in the owner's manual.
Currently neither channel is working, but the left channel was working before my RCA inputs must have loosened up the left post. I noticed that the musicap on the capacitor rail has a burn on it where wire enters the musicap (Part C-2816 1.0 +/- 10% 200V MCPP105KC Musicap).... anyone know where I could get more of these?
I was going to post some jpegs of the amp w/o the cover on, but my files are too large. Email me and I will send you the pictures or put them online.
Can someone recommend some troubleshooting steps that I can try? All the fuses are fine, but the musicap does need replaced.
Over the years Musical Concepts ha several different types of modifications to the circuit cards in the Hafler amps. You need to get a graphics software that can shrink the size of your JPGs and post pictures here. There are several free shareware graphics programs suitable to your needs.
Does your PCB look like this? Without more specific info you will only get generalities in advice.
Does your PCB look like this? Without more specific info you will only get generalities in advice.
