Thanks guys.
Ok, I have a few questions.
1) You can see in the pics the type of heatsink I plan to use on the drivers. Do you think these will suffice?
2) If you look just to the right of center in the first pick you can see the 2SC3955 bolted to the heatsink. Is this too far from the output transistors to do it's job?
3) The fan I purchased is 120V. It puts out a lot of air and is a bit noisier than I had hoped for. On my Hafler P500, there is a 120v fan that has two thermal switches which are bi-passed with 20W 150ohm resistors. As the heatsink heats up the switches open and send the current through the resistors. These are hooked in series and the switches open at different temps. Would this work for this amp?
If so, what temp switches should I use?
4) I used the terminal block as a way of securing the leads without grounding them to the heatsink. Do you think I could solder each set of three leads to eyelet connectors and then bolt them down? I worry about them moving around and somehow shorting out.
5) I only see one grounding point on these board and that is next to the input. It seems rather small. Is this the only point where they are grounded?
6) On the schematic I see R205 and C201 going to ground. are these necessary? Would I simply hook up from the output to the star ground?
They are what I have. Do you guys think they will be enough for this amp? I plan to hook them up like this.
Thanks again.
Blessings, Terry
Ok, I have a few questions.
1) You can see in the pics the type of heatsink I plan to use on the drivers. Do you think these will suffice?
2) If you look just to the right of center in the first pick you can see the 2SC3955 bolted to the heatsink. Is this too far from the output transistors to do it's job?
3) The fan I purchased is 120V. It puts out a lot of air and is a bit noisier than I had hoped for. On my Hafler P500, there is a 120v fan that has two thermal switches which are bi-passed with 20W 150ohm resistors. As the heatsink heats up the switches open and send the current through the resistors. These are hooked in series and the switches open at different temps. Would this work for this amp?
If so, what temp switches should I use?
4) I used the terminal block as a way of securing the leads without grounding them to the heatsink. Do you think I could solder each set of three leads to eyelet connectors and then bolt them down? I worry about them moving around and somehow shorting out.
5) I only see one grounding point on these board and that is next to the input. It seems rather small. Is this the only point where they are grounded?
6) On the schematic I see R205 and C201 going to ground. are these necessary? Would I simply hook up from the output to the star ground?
They are what I have. Do you guys think they will be enough for this amp? I plan to hook them up like this.
Thanks again.
Blessings, Terry
Re: emitter resistors...
Hi stuart,
I'm hoping you are still sending some to me. I know I have already used others in this amp but I am planning on building another when Als boards are done.
Are you talking about adding a 16ga wire in addition to the ground plane? I am planning to tin the entire foil pattern with solder once I have the resistors and leads added.
I don't know what a MKP is. Could you explain this a little better and maybe give a recomendation for the part?
Thanks, Terry
Stuart Easson said:
Hi stuart,
I'm hoping you are still sending some to me. I know I have already used others in this amp but I am planning on building another when Als boards are done.
apassgear said:
Are you talking about adding a 16ga wire in addition to the ground plane? I am planning to tin the entire foil pattern with solder once I have the resistors and leads added.
I don't know what a MKP is. Could you explain this a little better and maybe give a recomendation for the part?
Thanks, Terry
Hello Terry, try wiring the fan to one pair of the secondary outputs. The fan will run much slower and quieter, as it is an AC fan you should not have problems with the Hysterisis curve effect of a DC Motor. he fan will not draw enough current to unbalance the AC supply to the bridge rectifier.
BTW
MKP is a Metalized Polypropelene Capacitor.
Regards
Anthony
still4given said:
I prefer 12V DC fans, they are quieter, but that requires a 12V secondary or another small trafo. Building a PSU and circuit for a variable speed fan is very easy… I do mine on a 2.25x1.7 PCB including PSU. This way you can adjust the speed to what is requiered, in winter you may like a slower fan speed...
Looking at your setup I think you will need the fan ON all the time but you can add a thermo switch (through the secondary) to the fan circuit maybe some 75º C. DigiKey carries those, but don’t remember the part number, I could search for those if you want.
Here is the schematic showing the fan switch.
R45 and R46 call for 20w 150ohm.
I already have two 25w 150ohm resistors.
Would this work?
I am a little worried about using part of the secondaries from my xformer for my fan since it seems a little undersized as far as vA is concerned, especially since everyone else seems to using two xformers. Maybe I'm worrying for nothing.
Thanks, Terry
R45 and R46 call for 20w 150ohm.
I already have two 25w 150ohm resistors.
Would this work?
I am a little worried about using part of the secondaries from my xformer for my fan since it seems a little undersized as far as vA is concerned, especially since everyone else seems to using two xformers. Maybe I'm worrying for nothing.
Thanks, Terry
results and pics
OK Mark, thanks for the help. In the image below according to the posted (other) method-- looking at the transistor pins on the far side that face you-- the base is the pin on the left and the emitter is the pin on the right. I get a reading of .52 using my diode test mode on the DMM black on collector (case) and red on pin (MJ21193) and red on collector and black on pin (MJ21194). This is consistent with data sheets I have seen (note that the Onsemi DS does not indicate which pin is which).
I wonder what this .52 is supposed to represent?
Someone (ooops, look like it was you) said something about ohms. Using the DMM to read ohms I cannot get any reading between any pins and the collector; I know I used 200 ohm setting (yeah its too low...I know) and even a higher setting too but for some reason no setting would give me a valid reading. Anyway, it should have right?? Might have to check this again.
Mark A. Gulbrandsen said:
OK Mark, thanks for the help. In the image below according to the posted (other) method-- looking at the transistor pins on the far side that face you-- the base is the pin on the left and the emitter is the pin on the right. I get a reading of .52 using my diode test mode on the DMM black on collector (case) and red on pin (MJ21193) and red on collector and black on pin (MJ21194). This is consistent with data sheets I have seen (note that the Onsemi DS does not indicate which pin is which).
I wonder what this .52 is supposed to represent?
Someone (ooops, look like it was you) said something about ohms. Using the DMM to read ohms I cannot get any reading between any pins and the collector; I know I used 200 ohm setting (yeah its too low...I know) and even a higher setting too but for some reason no setting would give me a valid reading. Anyway, it should have right?? Might have to check this again.
An externally hosted image should be here but it was not working when we last tested it.
Pics of Front Panel
A word about my front panel.
I thought about this a lot. My amp will look kind of wacky like my other amps and preamps (see my www link below).
However, more to the point. I shamelessy stole styling cues from the KSA 50, and then the FBB series of amps. I'll use, as you can see, a countersunk name badge and the triangle of lights. This will be immediately recognizable as a krell clone due to these styling features, but the rest of the thing will be completely different.
Made by Frontpanelexpress.com, total cost was about $70.00. The badge part was over $20.00; very expensive and time consuming to design, but so very very relevant, don't you think?
I hate to ruin the surprise but Stewart wanted some pics. Since he has been so helpful here is a preview-- again against my better judgment. I feel bad about posting this early because I halfway think that all of you will laugh at this and hate it and I halfway think all of you will copy the idea...oh well you will see it eventually when its done.
A word about my front panel.
I thought about this a lot. My amp will look kind of wacky like my other amps and preamps (see my www link below).
However, more to the point. I shamelessy stole styling cues from the KSA 50, and then the FBB series of amps. I'll use, as you can see, a countersunk name badge and the triangle of lights. This will be immediately recognizable as a krell clone due to these styling features, but the rest of the thing will be completely different.
Made by Frontpanelexpress.com, total cost was about $70.00. The badge part was over $20.00; very expensive and time consuming to design, but so very very relevant, don't you think?
I hate to ruin the surprise but Stewart wanted some pics. Since he has been so helpful here is a preview-- again against my better judgment. I feel bad about posting this early because I halfway think that all of you will laugh at this and hate it and I halfway think all of you will copy the idea...oh well you will see it eventually when its done.
An externally hosted image should be here but it was not working when we last tested it.
Terry,
Your resistors are on the way...you should have them in the next couple of days...
The various small value caps around the mains input and bridge rectifier are a good idea, but not essential, they clean up the input from PG&E and reduce the possibility of mains borne interference.
The diode test tells you the forward conduction voltage of the diode formed by the junctions of the transistor. A reading between 0.5v and 0.6v would be expected for a forward biased junction, and no reading at all for a reverse biased junction. The C-E junction will not show any reading in either polarity.
Stuart
Your resistors are on the way...you should have them in the next couple of days...
The various small value caps around the mains input and bridge rectifier are a good idea, but not essential, they clean up the input from PG&E and reduce the possibility of mains borne interference.
The diode test tells you the forward conduction voltage of the diode formed by the junctions of the transistor. A reading between 0.5v and 0.6v would be expected for a forward biased junction, and no reading at all for a reverse biased junction. The C-E junction will not show any reading in either polarity.
Stuart
Terry,
Yes that is what I ment with the bus wire, just make a U and solder beside the cap terminals before you tin the ground plane.
It will work very nice if you tie the wire in 3 palces before sodering it, this is done by making small holes besides the wire and use a small gage copper wire for tying. But tin the bus wire first. You will need a hevier soldering iron in palce of what you use regulary for PCB work, applay heat over the bus wire.
Yes, as Anthony said, MKP is a metalized polyprop cap. >Even if you dont have provision for it now, try to test with and w/o and hear the difference, then you decide.
Yes that is what I ment with the bus wire, just make a U and solder beside the cap terminals before you tin the ground plane.
It will work very nice if you tie the wire in 3 palces before sodering it, this is done by making small holes besides the wire and use a small gage copper wire for tying. But tin the bus wire first. You will need a hevier soldering iron in palce of what you use regulary for PCB work, applay heat over the bus wire.
Yes, as Anthony said, MKP is a metalized polyprop cap. >Even if you dont have provision for it now, try to test with and w/o and hear the difference, then you decide.
source for sinks
It is 3/4 of the Mystery amplifier
After almost 3 years of DIY I am convinced that the only place to get heat sinks and chassis' are ebay and surplus stores. And the trading post here of course.
apassgear said:
It is 3/4 of the Mystery amplifier
After almost 3 years of DIY I am convinced that the only place to get heat sinks and chassis' are ebay and surplus stores. And the trading post here of course.