The 15003 / 4 is more robust than the originals, but it is
slower - 2 MHz compared to 4 MHz. It should drop in, although
you would want to confirm no oscillation in the finished job.
slower - 2 MHz compared to 4 MHz. It should drop in, although
you would want to confirm no oscillation in the finished job.
Nelson Pass said:
What does this mean in terms of sound quality? are these the wrong transistor? Now I am really confused. I dont want to go thru this and have inferior sound I will tell you that right now.
Putting away the soldering iron until I get this figured out.. only have 2 in so far.
EDIT: I see now that Anatech was looking for someone to confirm these transistors.. I fear I jumped the gun on this and ordered the wrong ones.
Not sure what to do now.
400a outputs
The 15004s and 15003 will work fine. I have used them although I prefer 15022 and 23
Higher voltage and current capabilities is a good thing. The 2 Mhz is not an issue since the bandwidth of the design is about 20Khz At least it will be harder for it to oscillate!
Heres what I usually do to improve these units.
1 Use blackgates in the driver board
2 Use IXYS fast recovery rectifier
3 Rewire the power supply with better wire
4 Replace the fuse posts
5 Mills resistors are an option for the emitter resistors
Bias at 150 mv. Increase to 200mv as desired.
The first objective is to get it running without oscillation or DC offset
Jon of VintageAmp
The 15004s and 15003 will work fine. I have used them although I prefer 15022 and 23
Higher voltage and current capabilities is a good thing. The 2 Mhz is not an issue since the bandwidth of the design is about 20Khz At least it will be harder for it to oscillate!
Heres what I usually do to improve these units.
1 Use blackgates in the driver board
2 Use IXYS fast recovery rectifier
3 Rewire the power supply with better wire
4 Replace the fuse posts
5 Mills resistors are an option for the emitter resistors
Bias at 150 mv. Increase to 200mv as desired.
The first objective is to get it running without oscillation or DC offset
Jon of VintageAmp
As for now, I would concentrate on the broken parts only until you can confirm that the amp is working.
The grease is not conductive so no worries about it touching the transistor pins.
Apply equally, Anatech’s brush method is perfect.
Put some on the transistor, lay the mica on top and put some on the mica too.
Bolt all transistor into the amp and solder them afterwards, not the other way around.
The job is done properly if a tiny bit of grease comes out of the devices borders when fastening.
Replace other broken parts (IIRC two resistors but measure all source R’s) and power up the amp slowly with a variac and a light bulb in series with the mains.
/Hugo
The grease is not conductive so no worries about it touching the transistor pins.
Apply equally, Anatech’s brush method is perfect.
Put some on the transistor, lay the mica on top and put some on the mica too.
Bolt all transistor into the amp and solder them afterwards, not the other way around.
The job is done properly if a tiny bit of grease comes out of the devices borders when fastening.
Replace other broken parts (IIRC two resistors but measure all source R’s) and power up the amp slowly with a variac and a light bulb in series with the mains.
/Hugo
Hi Hugo,
Thank you. You took the words right out of my mouth! 🙂
I only use a variac on power up and measure test points like a demon.
Hi Joe,
Those are the transistors I would use in this design as replacements. MJ15002X types are faster and may oscillate in some older designs. Jon knows them to work well in this case.
I used to stock MJ15024 and MJ15025 as standard replacements and the MJ15003 and MJ15004. Both are excellent in their application. I still think the MJ15003 and MJ15004 are the more proper subs in your case.
-Chris
Thank you. You took the words right out of my mouth! 🙂
I only use a variac on power up and measure test points like a demon.
Hi Joe,
Those are the transistors I would use in this design as replacements. MJ15002X types are faster and may oscillate in some older designs. Jon knows them to work well in this case.
I used to stock MJ15024 and MJ15025 as standard replacements and the MJ15003 and MJ15004. Both are excellent in their application. I still think the MJ15003 and MJ15004 are the more proper subs in your case.
Yes! Get it running before worring about the tweak aspect.
-Chris
AR2,
your question merits its own thread and can be found here:
http://www.diyaudio.com/forums/showthread.php?postid=1131075#post1131075
/Hugo
your question merits its own thread and can be found here:
http://www.diyaudio.com/forums/showthread.php?postid=1131075#post1131075
/Hugo
Man was I in a bad mood last night after Nelson Pass made that post.. Well; if you guys are relatively sure that these are right I will move forward... only one problem.. Ocillation? The only oscillation I know of too look for might be involving my girlfriend 😉
I assume by DC you mean I should check the output and input for that matter for excessive DC.. and my readings of the working channel are documented here to use as a benchmark. But I have no oscilloscope so I am not sure if I will be able to "check for oscillations"..
Okay; game on!
..and thanks for the grease info.. this is nearly the same as when you do a head gasket on a car engine.. smooth and consistant.. most will get pushed out when you torque them down.. (And I am only using the screwdriver to torque, so its not a ton.. and I am using locktite on the threads.. seemed prudent).
BTW.. I know Mr. Pass meant no harm with that post.. he just assumes I know more than I do.. BTW- Mr. Pass did decline to sign my amp.. he has had too many requests for this he has already turned down and it would not be fair.. he was very nice about it and I have no ill feelings whatsoever..
All the caps are in on the input board.. and 2 transistors and 1 emmitter are installed. Lots to do..
I'm glad I took detailed photos to get everything back EXACTLY as it was! 🙂
Thanks to all who have responded here...
Oh, can someone explain the lightbulb in line with the variac? On the AC line? I am confused.. and I assume the point is to have the bulb blow if there is a problem?
I assume by DC you mean I should check the output and input for that matter for excessive DC.. and my readings of the working channel are documented here to use as a benchmark. But I have no oscilloscope so I am not sure if I will be able to "check for oscillations"..
Okay; game on!
..and thanks for the grease info.. this is nearly the same as when you do a head gasket on a car engine.. smooth and consistant.. most will get pushed out when you torque them down.. (And I am only using the screwdriver to torque, so its not a ton.. and I am using locktite on the threads.. seemed prudent).
BTW.. I know Mr. Pass meant no harm with that post.. he just assumes I know more than I do.. BTW- Mr. Pass did decline to sign my amp.. he has had too many requests for this he has already turned down and it would not be fair.. he was very nice about it and I have no ill feelings whatsoever..
All the caps are in on the input board.. and 2 transistors and 1 emmitter are installed. Lots to do..
I'm glad I took detailed photos to get everything back EXACTLY as it was! 🙂
Thanks to all who have responded here...
Oh, can someone explain the lightbulb in line with the variac? On the AC line? I am confused.. and I assume the point is to have the bulb blow if there is a problem?
The light bulb goes in series with one wire of the mains voltage.
It prevent excessive current draw in the amplifier in case something is wrong.
I can't calculate the bulb wattage but try 100W to start with.
DC at the output is indeed what you want to measure.
Disregard the input for now.
/Hugo
It prevent excessive current draw in the amplifier in case something is wrong.
I can't calculate the bulb wattage but try 100W to start with.
DC at the output is indeed what you want to measure.
Disregard the input for now.
/Hugo
Hi Joe,
One other point. Slower output devices are very unlikely to oscillate compared to the original parts. If the amp had an oscillation problem before, it will still have one.
Since you are using new parts, your rebuild should go okay unless you miss something.
-Chris 😉
One other point. Slower output devices are very unlikely to oscillate compared to the original parts. If the amp had an oscillation problem before, it will still have one.
Since you are using new parts, your rebuild should go okay unless you miss something.
Try not to read more into a post than is there. I know there are no voice inflections to read, or facial expressions. Therefore it's always best to assume a post is made with the best of intentions.
-Chris 😉
anatech said:
Right back at you.. I never assumed he "meant" anything by it.. I was just discouraged that I made the wrong part selection..
Thanks.. I should be done by this evening sometime.. but I need to get some parts to rig up the light bulb.. I'll need to make a hardware store run and get a few things..
I'll let you know how bright the light gets 🙂
Hi Joe,
Understand you are powering up a high bias amplifier. Therefore the lightbulb will starve the amp unless you also get some bigger ones.
Example. Say the amp normally draws 200 W just sitting there (yours draws more I think), a 200 W light bulb would probably glow at around 1/3 brightness as a guess. The amplifier would get around 60 VAC at it's terminals in that case assuming a 120 VAC supply, the lightbulb would drop the other 60VAC. This isn't exactly right since I don't use lightbulbs and you are running the lamp at reduced voltage. So my voltage drops will be off. I do know the lamp may be much dimmer than 1/2 brightness (unless I'm wrong about that - very possible).
Hey Hugo!,
Comments? Please correct me here.
-Chris
Understand you are powering up a high bias amplifier. Therefore the lightbulb will starve the amp unless you also get some bigger ones.
Example. Say the amp normally draws 200 W just sitting there (yours draws more I think), a 200 W light bulb would probably glow at around 1/3 brightness as a guess. The amplifier would get around 60 VAC at it's terminals in that case assuming a 120 VAC supply, the lightbulb would drop the other 60VAC. This isn't exactly right since I don't use lightbulbs and you are running the lamp at reduced voltage. So my voltage drops will be off. I do know the lamp may be much dimmer than 1/2 brightness (unless I'm wrong about that - very possible).
Hey Hugo!,
Comments? Please correct me here.
-Chris
anatech said:
I still dont quite understand.. it would help if you gave me a scenario... lets say there is something "wrong"... would the bulb at some point go very dim? If everything is ok would the bulb get brighter and brighter as I turn up the variac?
I dont know what the point is I guess.. I figured it was being used as a fuse.. guess I am mistaken?
Edit: Why not just monitor say an emmitter and slowly turn up the voltage? (no bulb).. ? Or maybe monitor ALL the emmitters? I could note the good side values? Maybe I should note a whole bunch of test points on the good side and just keep going in circles thru the test locations as I go up 10v at a time? That seems "wise" to me.
With big amps, I start with 100 or 150 watt.
Smaller amps will see 60W. I soon get a grip on how the amp behaves. I watch the rails and the output and have my nose, eyes and ears sharpened at startup. Nothing fancy. 🙂
/Hugo
Smaller amps will see 60W. I soon get a grip on how the amp behaves. I watch the rails and the output and have my nose, eyes and ears sharpened at startup. Nothing fancy. 🙂
/Hugo
Hi Joe,
Hugo, thanks. I only use a variac, or a DC power supply, so you are my expert on light bulbs.
-Chris 😉
A high current fault would make the bulb brighter. A direct short would make the bulb glow at full brightness when you have full voltage.
Hugo, thanks. I only use a variac, or a DC power supply, so you are my expert on light bulbs.
-Chris 😉
Hi Joe,
Nice pile of parts.
I've just seen your posts.
You're going to love this...
I wouldn't recommend locktite on the screw threads. While it's prudent on vehicles, those screws conduct power for the collectors. Is locktite conductive? I don't have an answer for that question... There is no need to use it on the transistors as I've never seen it used before. Will it work ok, your guess is as good as mine.
The transistors you bought will work fine.
Check the resistance between the heatsink and each transistor as you mount them. If you find a direct short, then you'll know you have to check the last transistor that you mounted. It will save you lots of grief checking each one as you do them in the event one of them shorts through the mica insulator.
No matter what, before you apply power, check the resistance between the transistor cases and the heatsink.
You should not have a direct short between the transistor cases and the heatsink!
Also, double and triple check your soldering work for bridged solder joints.
The light bulb or the variac both will do the same thing. The idea is for you not to hit it with full power until you are sure you did everything right. Put it all together, then give it about half voltage, then measure the dc offset at the speaker terminals.
You'll have a pretty good idea if everything is correct. If both channels have no dc at the outputs then you can slowly bring up the power. Just keep checking it.
Keep us posted.
Nice pile of parts.
I've just seen your posts.
You're going to love this...
I wouldn't recommend locktite on the screw threads. While it's prudent on vehicles, those screws conduct power for the collectors. Is locktite conductive? I don't have an answer for that question... There is no need to use it on the transistors as I've never seen it used before. Will it work ok, your guess is as good as mine.
The transistors you bought will work fine.
Check the resistance between the heatsink and each transistor as you mount them. If you find a direct short, then you'll know you have to check the last transistor that you mounted. It will save you lots of grief checking each one as you do them in the event one of them shorts through the mica insulator.
No matter what, before you apply power, check the resistance between the transistor cases and the heatsink.
You should not have a direct short between the transistor cases and the heatsink!
Also, double and triple check your soldering work for bridged solder joints.
The light bulb or the variac both will do the same thing. The idea is for you not to hit it with full power until you are sure you did everything right. Put it all together, then give it about half voltage, then measure the dc offset at the speaker terminals.
You'll have a pretty good idea if everything is correct. If both channels have no dc at the outputs then you can slowly bring up the power. Just keep checking it.
Keep us posted.
Hi Steve,
For car amps it's wonderful stuff if you are torquing the screws properly (not too tight). I imagine it would be just as good for powered subs.
-Chris 😉
I've seen it used from time to time. It doesn't seem to affect conductivity since it's used sparingly.
For car amps it's wonderful stuff if you are torquing the screws properly (not too tight). I imagine it would be just as good for powered subs.
-Chris 😉
Hi Chris,
I wouldn't use it, but I'll defer to you on this one.
I've never seen it used inside a large amp.
Thanks!
I wouldn't use it, but I'll defer to you on this one.
I've never seen it used inside a large amp.
Thanks!
Loctite Blue for mounting TO3 transistors
Did a little more research on the Loctite issue:
I assumed that Loctite Blue was being used so parts could be removed if necessary.
"Dielectric Strength: 9.8 kV/mm" (cured)
Here's the technical data link...
http://64.242.109.170:8080/1/doc?id=26192
It looks to be a pretty good insulator once it has cured.
I would not be using it in areas that need to conduct electricity... (i.e. TO3 transistor mounting)
(sorry guys...)
Did a little more research on the Loctite issue:
I assumed that Loctite Blue was being used so parts could be removed if necessary.
"Dielectric Strength: 9.8 kV/mm" (cured)
Here's the technical data link...
http://64.242.109.170:8080/1/doc?id=26192
It looks to be a pretty good insulator once it has cured.
I would not be using it in areas that need to conduct electricity... (i.e. TO3 transistor mounting)
(sorry guys...)