Hi,
if 2n3773 were the original outputs then they had 150W at 100V on the DC SOA. Yes the knee in the SOA curve was @ 100Volts. It is even tested (100%) for this parameter.
There are not many higher rated devices that can better this significantly.
If you change devices then this is the crucial parameter that needs to be bettered.
The 200V MJL3281 and 350V MJL4281 cannot get near that high voltage performance. I realise that these are To264 plastic packages, I'm just pointing out the futility of selecting apparently high voltage devices.
Even the To3 MJ15024 has fallen from 250W @ 70V to just 100W @ 100V.
Now, go and look at the 2sa1535 high voltage performance, it stinks!
if 2n3773 were the original outputs then they had 150W at 100V on the DC SOA. Yes the knee in the SOA curve was @ 100Volts. It is even tested (100%) for this parameter.
There are not many higher rated devices that can better this significantly.
If you change devices then this is the crucial parameter that needs to be bettered.
The 200V MJL3281 and 350V MJL4281 cannot get near that high voltage performance. I realise that these are To264 plastic packages, I'm just pointing out the futility of selecting apparently high voltage devices.
Even the To3 MJ15024 has fallen from 250W @ 70V to just 100W @ 100V.
Now, go and look at the 2sa1535 high voltage performance, it stinks!
AndrewT said:
Aaah the old & reliable 2N3773....it's coming back to me now. Aah I know, I designed with it here ...
http://www.diyaudio.com/forums/attachment.php?s=&postid=822751&stamp=1137818325
from thread
http://www.diyaudio.com/forums/showthread.php?postid=822751#post822751
The 2N3773 is very strong but it could be too slow. The data sheets do not show an Ft for it and my Towers book says only 200Khz....The reason I designed with it was to fulfill a special request by Zeonrider who had a box of 'em.
Now the MJ15003's whilst not as powerful as 2N3773's are still stronger than the originals, have much better gain and an Ft of 2Mhz.
Depending on where ya live...these could be fairly cheap to pick up... cheaper than the fancy new transistors.
Cheers
Q
After looking at the service manual, I realized that the amplifier that I had, and used to service was the DC300. It is a different animal than the DC300A. The service manual is on their web site and is still good for a laugh:
http://www.crownaudio.com/pdf/legacy/dc300-sm.pdf
For modern output devices look at ON Semi MJW21195 and MJW21196. Even I have a hard time blowing these up. They are not TO3, but can be made to fit on most TO3 heat sinks.
There is a similar part in TO3 packaging the MJ21193 and MJ21194. The Crown CE2000 uses the MJ21194 parts, 12 of them in each channel.
http://www.crownaudio.com/pdf/legacy/dc300-sm.pdf
For modern output devices look at ON Semi MJW21195 and MJW21196. Even I have a hard time blowing these up. They are not TO3, but can be made to fit on most TO3 heat sinks.
There is a similar part in TO3 packaging the MJ21193 and MJ21194. The Crown CE2000 uses the MJ21194 parts, 12 of them in each channel.
I'm Sold! MJ21194
This TO3 rocks. It is the ideal replacement to the 2N3773. The gain looks slightly higher but over all it is ideal looking. And how about that, Crown currently uses them. Sounds good to me.
2N3773 SOA 100W @ 100V
MJ21194 SOA 200W @ 80V
For the supply voltages of +_65VDC running in the DC300A the MJ21194 would be and upgrade.
Thanks,
Shawn.
tubelab.com said:
djk said:
This TO3 rocks. It is the ideal replacement to the 2N3773. The gain looks slightly higher but over all it is ideal looking. And how about that, Crown currently uses them. Sounds good to me.
2N3773 SOA 100W @ 100V
MJ21194 SOA 200W @ 80V
For the supply voltages of +_65VDC running in the DC300A the MJ21194 would be and upgrade.
Thanks,
Shawn.
Hi,
post 52 & 59 suggested mj21194.
Your numbers are like apples and oranges.
I know nothing about the Crown but I still think the 21194 would make an acceptable replacement for the 3773. It will also allow working into a lower load (post52)
post 52 & 59 suggested mj21194.
Your numbers are like apples and oranges.
they should say 3773 150W @100V and 21194 200W @100V.
I know nothing about the Crown but I still think the 21194 would make an acceptable replacement for the 3773. It will also allow working into a lower load (post52)
Oops I did it again
Here is the other PC board. So we have artwork for full-on retro rebuild, if that is the way to go. I'm kind of sitting on the fence. I thought more people would take the time to vote in the poll? And all those people wanting to take her out to the cottage and drop her off the wharf? Tisk tisk.
Chris, regarding oscillations the current bandwidth is listed for the MJ21194 on the On Semi sheet as 4 MHz but there is no spec indicated on the 2N3773 data sheet. ??
Shawn.
Here is the other PC board. So we have artwork for full-on retro rebuild, if that is the way to go. I'm kind of sitting on the fence. I thought more people would take the time to vote in the poll? And all those people wanting to take her out to the cottage and drop her off the wharf? Tisk tisk.
Chris, regarding oscillations the current bandwidth is listed for the MJ21194 on the On Semi sheet as 4 MHz but there is no spec indicated on the 2N3773 data sheet. ??
Shawn.
Attachments
Hi Shawn,
Incorporate new devices in your layout since you have the chance to do so. You may end up with TO-220 or TO-126 types instead of the TO-5 originals.
The MJL2119X types maintain gain to higher current levels. The curves are a little flatter. The same goes for new drivers and other parts. It was common for parts like the Fairchild to be faster and have different compensation than other (motorola and other) brands. I thnk I remember that right. Point is, different outputs needed different compensation and they recognised that way back then.
So, compensate for the faster devices if they indicate that in one of the schematics and you may need to work on it some more.
-Chris
Incorporate new devices in your layout since you have the chance to do so. You may end up with TO-220 or TO-126 types instead of the TO-5 originals.
The MJL2119X types maintain gain to higher current levels. The curves are a little flatter. The same goes for new drivers and other parts. It was common for parts like the Fairchild to be faster and have different compensation than other (motorola and other) brands. I thnk I remember that right. Point is, different outputs needed different compensation and they recognised that way back then.
So, compensate for the faster devices if they indicate that in one of the schematics and you may need to work on it some more.
-Chris
New Devices in layout...
Yes, the image you see is soft, now that I have it on my PC it is like clay in my hands. As the devices are selected (IF) I will then tweak to embrace the different components. First things First, the image needed to be brought on board. BTW, both pieces of artwork were done painstakingly by hand in photoshop! I must be crazy?
Cheers
anatech said:
Yes, the image you see is soft, now that I have it on my PC it is like clay in my hands. As the devices are selected (IF) I will then tweak to embrace the different components. First things First, the image needed to be brought on board. BTW, both pieces of artwork were done painstakingly by hand in photoshop! I must be crazy?
I know what you mean but that sounds like mud.
Cheers
Front Panel
I stripped the front panel and it was in rough shape. I gave it a hair cut and little scrub & polish but it has these stains. The stains seem like some kind of acid was splashed on to it. I sanded it with scotchbrite very hard but still the stains won't come off?
It looks good but I think it should look better. Any ideas how to remove the blemishes?
Shawn.
I stripped the front panel and it was in rough shape. I gave it a hair cut and little scrub & polish but it has these stains. The stains seem like some kind of acid was splashed on to it. I sanded it with scotchbrite very hard but still the stains won't come off?
It looks good but I think it should look better. Any ideas how to remove the blemishes?
Shawn.
Attachments
Re: Front Panel
If it's aluminum and it's truly etched, they won't come off. Since you already scotched 'it, I'd give it a go over with a flapwheel sander or rotary scotchbrite type finisher, and try to even out the satin luster @ about 140 - 200 grit or so... give it a kinda "brushed chrome" finish.
I was trying to look at the b4 strip picture, but couldn't find a whole shot to see if it was etched b4 stripping.
The advantage of the brush finish is it hides damaged areas where the metal was dinged from being dropped and banged around, and, done right, looks pretty classy. You could then have it anodized and dyed to whatever color (puce?) maybe you want.
John L.
TomWaits said:
If it's aluminum and it's truly etched, they won't come off. Since you already scotched 'it, I'd give it a go over with a flapwheel sander or rotary scotchbrite type finisher, and try to even out the satin luster @ about 140 - 200 grit or so... give it a kinda "brushed chrome" finish.
I was trying to look at the b4 strip picture, but couldn't find a whole shot to see if it was etched b4 stripping.
The advantage of the brush finish is it hides damaged areas where the metal was dinged from being dropped and banged around, and, done right, looks pretty classy. You could then have it anodized and dyed to whatever color (puce?) maybe
you want.John L.
Re: Re: Front Panel
Yes, I will send it out for anodized treatment. I think it is logical (if) I get this restoration/rebuild right, then I'll get a gold anodized finish. You know, from silver to gold! Heck you can go blue or whatever you want these days. I even checked out a DIY set-up from some dude in the US that shows exactly how to set up the process at home.
I've got to sand that cover down with something and I may try the flap wheel next. I'm a little worried about consistency and not putting groves on the face? Tomorrow over first coffee...
Thanks,
Shawn.
What do you mean by etched before stripping?auplater said:
The advantage of the brush finish is it hides damaged areas where the metal was dinged from being dropped and banged around, and, done right, looks pretty classy. You could then have it anodized and dyed to whatever color (puce?) maybe
John L.
Yes, I will send it out for anodized treatment. I think it is logical (if) I get this restoration/rebuild right, then I'll get a gold anodized finish. You know, from silver to gold! Heck you can go blue or whatever you want these days. I even checked out a DIY set-up from some dude in the US that shows exactly how to set up the process at home.
I've got to sand that cover down with something and I may try the flap wheel next. I'm a little worried about consistency and not putting groves on the face? Tomorrow over first coffee...
Thanks,
Shawn.
Getting better
Here is some cleaned up metal. Not so bad after all. Steel wool on the rusty XFMR and then I coated it with some new coil winding laquer. The top and bottom grills along with the bells from the XFMR were painted and baked today. The heat sink is mint as I did not touch it other than cleaning it with simple green and a little water.
Cheers,
Shawn.
Here is some cleaned up metal. Not so bad after all. Steel wool on the rusty XFMR and then I coated it with some new coil winding laquer. The top and bottom grills along with the bells from the XFMR were painted and baked today. The heat sink is mint as I did not touch it other than cleaning it with simple green and a little water.
Cheers,
Shawn.
Attachments
anodizing, etc.
what i meant was if there was any damage b4 you did anything where the stains showed up?
Anodizing isn't too hard to do, need about 36 volts AC @ 20 amps/ft^2, a 180 F sealing tank, and some etch and acid dip tanks for pre-treating...
I've set up lots of systems, from benchtop to automotive production runs...
BUT... to get it right, you gotta know what you're doing.
what i meant was if there was any damage b4 you did anything where the stains showed up?
Anodizing isn't too hard to do, need about 36 volts AC @ 20 amps/ft^2, a 180 F sealing tank, and some etch and acid dip tanks for pre-treating...
I've set up lots of systems, from benchtop to automotive production runs...
BUT... to get it right, you gotta know what you're doing.
Re: anodizing, etc.
I wish I had a macro photo option on my camera, then I could give close ups. These blemishes are on the surface of the metal and there is one good scratch in there too...
I just rubbed it and took a good hard look at it, they are not chemical stains at all, they are divits in the metal by a drill or a grinder or some gouge marks that go perhaps .1mm under the top surface. It looks like someone sanded out the old scars before and after I stripped the paint, voila. I guess I understand what you were saying earlier.
I can fix it, I need to sand out those areas gently with something powerful. I have a hand held grinder but what attachment would be best?
Shawn.
auplater said:
I wish I had a macro photo option on my camera, then I could give close ups. These blemishes are on the surface of the metal and there is one good scratch in there too...
I just rubbed it and took a good hard look at it, they are not chemical stains at all, they are divits in the metal by a drill or a grinder or some gouge marks that go perhaps .1mm under the top surface. It looks like someone sanded out the old scars before and after I stripped the paint, voila. I guess I understand what you were saying earlier.
I can fix it, I need to sand out those areas gently with something powerful. I have a hand held grinder but what attachment would be best?
Shawn.