I had one of these back in the early 1970's. I played in a rock band, our motto was, if you can't be good, be loud. The Crown served well for that purpose.
I worked in a stereo shop, where I fixed a few of these also, and I still have the original service manual. I don't know who they got to write the manual, but is is a classic. If the intent was to get you to read the whole book before digging into the amp, it worked. I read the whole thing and laughed out loud all afternoon. As mentioned:
A few more quotes from the manual that I can remember from 1972:
Blood, sweat, and the smell of burnt parts. CPN does not stand for chocolate plated noodles, it means Crown part number.
9348 is the date code, and since this amp was extinct in 1993, so these are not the original transistors.
I am sure that there are plenty of modern transistors that will work in this amp (and I have not kept up with the state of the art) but I can say that the original amplifiers used 2N3773's. I had found a cooperative tech at Crown who told me to use ONLY Westinghouse 2N3773's and to match them by Vbe at a speciffic collector current (I don't remember ). I used Solitron millitary spec 2N3773's and they worked well.
The amp that I had, came to me because it had failed in a live music situation multiple times. It was replaced with something new, and tossed in the trash. Autopsy revealed the usual shorted outputs, blown emitter resistors, and associated fried parts. The transistors were RCA's, the Crown tech confirmed that RCA's tend to blow up in live rock environments. After I rebuilt the amp with Solitron outputs, it rocked. I sold it after a couple of years, and never saw it again.
History has repeated itself, and I was recently given a Crown CE2000. It was also the victim of an "expert" and has multiple black stains on the PC board where parts used to be. I have downloaded the service manual, and will dig into it when I find the time.
I worked in a stereo shop, where I fixed a few of these also, and I still have the original service manual. I don't know who they got to write the manual, but is is a classic. If the intent was to get you to read the whole book before digging into the amp, it worked. I read the whole thing and laughed out loud all afternoon. As mentioned:
A few more quotes from the manual that I can remember from 1972:
Blood, sweat, and the smell of burnt parts. CPN does not stand for chocolate plated noodles, it means Crown part number.
9348 is the date code, and since this amp was extinct in 1993, so these are not the original transistors.
I am sure that there are plenty of modern transistors that will work in this amp (and I have not kept up with the state of the art) but I can say that the original amplifiers used 2N3773's. I had found a cooperative tech at Crown who told me to use ONLY Westinghouse 2N3773's and to match them by Vbe at a speciffic collector current (I don't remember ). I used Solitron millitary spec 2N3773's and they worked well.
The amp that I had, came to me because it had failed in a live music situation multiple times. It was replaced with something new, and tossed in the trash. Autopsy revealed the usual shorted outputs, blown emitter resistors, and associated fried parts. The transistors were RCA's, the Crown tech confirmed that RCA's tend to blow up in live rock environments. After I rebuilt the amp with Solitron outputs, it rocked. I sold it after a couple of years, and never saw it again.
History has repeated itself, and I was recently given a Crown CE2000. It was also the victim of an "expert" and has multiple black stains on the PC board where parts used to be. I have downloaded the service manual, and will dig into it when I find the time.
bla bla bla
I plan to keep the case and heat sinks as I want to restore not rebuild. The output board will only fit the exact layout and position of the existing set-up. I have it in soft format and ready for tweaking. Nothing is in stone and I need more tech input from the brains who have downloaded the schematic from Crown Web Site and are reviewing it as I type this.
I am no PEng so I will need some serious input if I am to change the circuit. There is a lot going on in this design and it is much more complicated than the look of the amp itself. I consider the foot print, era and power to make this an exceptional design. It needs a little modern twist.
If it is all nine, then I will replace the components and put it back together, still it should be better than new.
Shawn.
Yes djk, and I wait to see what is to be done on the dysfunctional OpAmp. I think it makes sense to cook up a new driver board, I think. It is where the sound of this amp is born. It is where the Glass can be broken and the warmth of mother's chest can be introduced to the circuit.djk said:
I plan to keep the case and heat sinks as I want to restore not rebuild. The output board will only fit the exact layout and position of the existing set-up. I have it in soft format and ready for tweaking. Nothing is in stone and I need more tech input from the brains who have downloaded the schematic from Crown Web Site and are reviewing it as I type this.
I am no PEng so I will need some serious input if I am to change the circuit. There is a lot going on in this design and it is much more complicated than the look of the amp itself. I consider the foot print, era and power to make this an exceptional design. It needs a little modern twist.
If it is all nine, then I will replace the components and put it back together, still it should be better than new.
Shawn.
I'm Happy
Just like the chaps that had those giant tube amps in the seventies, they were ashamed they had to go gigging with valve PA systems while the better-offs were using the big transistor power amps.
Well, we all know where the money is now, don't we?
This thing is a classic nomatter how you slice it. It is worth it, just for the love of it. I hope you understand. Perhaps not what you would suggest but it makes me happy.
Shawn.
burnedfingers said:
Just like the chaps that had those giant tube amps in the seventies, they were ashamed they had to go gigging with valve PA systems while the better-offs were using the big transistor power amps.
Well, we all know where the money is now, don't we?
This thing is a classic nomatter how you slice it. It is worth it, just for the love of it. I hope you understand. Perhaps not what you would suggest but it makes me happy.
Shawn.
Limited room for Driver Transistors
Good list Wrench but this captures my attention:
The DRIVERS must be reworked. The boards are scored from the heat there. Damn it the driver PCB couldn't be any closer to the front face plate of the amp. Like having your face pressed into a glass window?
(more glass being mentioned) If larger devices are to be used they may need to be laid down flat on the PCB. I can easily make custom heat sinks but low profile must be kept in mind. It seems to me in general the front driver board location was suffocating but it may have been one particular application of abuse that made this one worse?
Shawn.
Good list Wrench but this captures my attention:
wrenchone said:
The DRIVERS must be reworked. The boards are scored from the heat there. Damn it the driver PCB couldn't be any closer to the front face plate of the amp. Like having your face pressed into a glass window?
(more glass being mentioned) If larger devices are to be used they may need to be laid down flat on the PCB. I can easily make custom heat sinks but low profile must be kept in mind. It seems to me in general the front driver board location was suffocating but it may have been one particular application of abuse that made this one worse?Shawn.
Hi Shawn,
May I suggest a few things?
First, why not attempt to improve the existing design? You will reuse at least 50 % of the new outputs in this design. Try the MJ21195 / 96 pair as a target for output devices.
Have a listen. Live with it.
At this point you will be more familiar with the workings of your beastie (didn't I tell you it was?). Now you can take your time and update or completely redesign the unit. You will know where you came from and be secure in the knowledge that you did squeeze that last drop of performance from the original design. It's teh only way to create a roadmap for others to follow later.
I don't think you can just sit down and voila! A new design without mucking around with it. Take your time and enjoy the trip.
-Chris
May I suggest a few things?
First, why not attempt to improve the existing design? You will reuse at least 50 % of the new outputs in this design. Try the MJ21195 / 96 pair as a target for output devices.
Have a listen. Live with it.
At this point you will be more familiar with the workings of your beastie (didn't I tell you it was?). Now you can take your time and update or completely redesign the unit. You will know where you came from and be secure in the knowledge that you did squeeze that last drop of performance from the original design. It's teh only way to create a roadmap for others to follow later.
I don't think you can just sit down and voila! A new design without mucking around with it. Take your time and enjoy the trip.
-Chris
Re drivers. Anything larger than a TO-5 would have to lay down, but at least you can screw it to soething substantial to carry the heat away. There are some Japanese TO-126 package devices that would also work ok if you can find them. Back in the day the amp was designed, there wasn't much in the way of driver transistors. RCA had some complementary devices using TO-5s on proprietary integral heat sinks, but they were only good to around 90V or so. I recall using 2N3439 and 2N5416 transistors for drivers out of desperation, even those these are HV devices, and pretty slow.
Rebuild but still the same
Chris,
I would like to replace all of the components in this amp and hold on to the weird parts that can't be easily replaced like the funky inductors. I am ready and preparred to etch a new driver board and two output boards. I don't feel that many components can be removed with out wrecking the pcb trails anyway.
I guess I'm a little carried away with my forward thinking.
All I really want to do is improve it where possible knowing that I am etching all new pcb's for the amp. I don't want to end up with an entirely new amp.Looking at the schematic I will need:
-Substitutes for all of the transistors.
-If the power supply feeding the OpAmp is deemed ok then I can just change the layout for the pcb around it to accomodate new OpAmps?
-All passive components replaced with higher tolerance components. As you say and I love this quote, " All ceramics meet Mr. Hammer. Time for mica and the poly sisters."
That is the extent of my intentions but if there is obvious room to tweak a few things, I'm game.
Cheers,
Shawn.
anatech said:
Chris,
I would like to replace all of the components in this amp and hold on to the weird parts that can't be easily replaced like the funky inductors. I am ready and preparred to etch a new driver board and two output boards. I don't feel that many components can be removed with out wrecking the pcb trails anyway.
I can't, I don't have the knowlege but I'm hoping a few hard brain scans of the schematic by the locals here may reveal some obvious suggestions if I am already etching new pcb's.
I guess I'm a little carried away with my forward thinking.
All I really want to do is improve it where possible knowing that I am etching all new pcb's for the amp. I don't want to end up with an entirely new amp.Looking at the schematic I will need:
-Substitutes for all of the transistors.
-If the power supply feeding the OpAmp is deemed ok then I can just change the layout for the pcb around it to accomodate new OpAmps?
-All passive components replaced with higher tolerance components. As you say and I love this quote, " All ceramics meet Mr. Hammer. Time for mica and the poly sisters."
That is the extent of my intentions but if there is obvious room to tweak a few things, I'm game.
Cheers,
Shawn.
Hi Shawn,
That sounds perfectly reasonable.
Be....all you can be....... Arrrgh!
In keeping with the spirit then, figure out where your mounting limitations are. Plan for new components throughout and lay out your improved design. Forget trying to use subs. Figure on using the most capable parts and understand that you will have to play with the stabilization of this amp. You may even incorporate a DC servo to null out the last few mV.
You can design a daughter board to mount standard pinout type op amps to the existing design. That way you can try both, even LM318's to test components available at the time the amp was built.
-Chris
That sounds perfectly reasonable.
Be....all you can be....... Arrrgh!
In keeping with the spirit then, figure out where your mounting limitations are. Plan for new components throughout and lay out your improved design. Forget trying to use subs. Figure on using the most capable parts and understand that you will have to play with the stabilization of this amp. You may even incorporate a DC servo to null out the last few mV.
You can design a daughter board to mount standard pinout type op amps to the existing design. That way you can try both, even LM318's to test components available at the time the amp was built.
-Chris
New boards and stuff
Oh man! that is a hard one. I see no available room in this design for any expansion boards. Even a daughter board is pushing it and believe me this it the fast way if I could. Look at the top view looking in on the original posts. I don't see room for daughter boards or small opamp power supply ( I would love to put in a tiny power supply +_ for the OpAmp circuit).
Shawn.
I need to look again, I must make room....
anatech said:
Oh man! that is a hard one. I see no available room in this design for any expansion boards. Even a daughter board is pushing it and believe me this it the fast way if I could. Look at the top view looking in on the original posts. I don't see room for daughter boards or small opamp power supply ( I would love to put in a tiny power supply +_ for the OpAmp circuit).
Shawn.
I need to look again, I must make room....
Hi Shawn,
You may have to mount the faceplate without the top / bottom cover to check vertical clearance. It's been a while and I've never looked at these with a view to mounting anything new inside.
-Chris
Those sound like a replacement brand, as in ECG128 which was a T05 driver transistor. This further supports earlier work done.
You may have to mount the faceplate without the top / bottom cover to check vertical clearance. It's been a while and I've never looked at these with a view to mounting anything new inside.
-Chris
Hi Shawn,
I'm seeing double. I have to crash now.
More of the schematic is needed, I'll check mine. That "crappy" power supply did it's job fine. It was enough for the job at hand and saved them another winding or tap. Yes, it often needs repair but not so much that the amp wasn't reliable. MTF was measured in years.
-Chris
Edit:
I'm seeing double. I have to crash now.
More of the schematic is needed, I'll check mine. That "crappy" power supply did it's job fine. It was enough for the job at hand and saved them another winding or tap. Yes, it often needs repair but not so much that the amp wasn't reliable. MTF was measured in years.
Hmmm. Might be a house number then. I must admit to being hyper sensitive to anything remotely ECG sounding in older amplifiers. I haven't cracked that manual open for at least a year, so it's time for me to have a look.
-Chris
Edit:
Me too!
I need to replace this...
These are trouble at Q104 and Q204
Part Number = NSD128
Description = Si NPN Power HF Bipolar Junction Transistor
Manufacturer = National Semiconductor
V(BR)CEO (V) = 180
V(BR)CBO (V) = 180
I(C) Abs.(A) Collector Current = 250m
Absolute Max. Power Diss. (W) = 1.7
I(CBO) Max. (A) = 50n
h(FE) Min. Static Current Gain = 50
h(FE) Max. Current gain. = 500
@I(C) (A) (Test Condition) = 10m
@V(CE) (V) (Test Condition) = 5.0
f(T) Min. (Hz) Transition Freq = 100M
Status = Discontinued
Package = TO-202AA
Military = N
Looking for subs,
Shawn.
These are trouble at Q104 and Q204
Part Number = NSD128
Description = Si NPN Power HF Bipolar Junction Transistor
Manufacturer = National Semiconductor
V(BR)CEO (V) = 180
V(BR)CBO (V) = 180
I(C) Abs.(A) Collector Current = 250m
Absolute Max. Power Diss. (W) = 1.7
I(CBO) Max. (A) = 50n
h(FE) Min. Static Current Gain = 50
h(FE) Max. Current gain. = 500
@I(C) (A) (Test Condition) = 10m
@V(CE) (V) (Test Condition) = 5.0
f(T) Min. (Hz) Transition Freq = 100M
Status = Discontinued
Package = TO-202AA
Military = N
Looking for subs,
Shawn.
tubelab.com said:
Good words! Not often you drop in on the Semi side of the DIY so its good to stirr up some old vibes. Right now I just want to sub the full transistor line up with current offerings and I think the output section should not be too hard but the drivers and pre drivers?
Need help.Thanks,
Shawn.
"I replaced the old Delco output devices with some RCA 2N6678s. I also put in an input coupling cap...."
And how well did it work with a transistor with less than 60W at 100V SOA vs the 100W at 100V SOA transistor it came with?
I didn't understand SOA back then either.
The reason Crown specified Westinghouse is you got epitaxial, RCA was building hometaxial. For the longest time Motorola built both, the faster epitaxial part was more money. The newer MJ15024 is from the same die family as the epitaxial 2N3773, and the data is shown on the same pages and uses the same graphs for many of the parameters. The MJ21194 is the newest version with the perforated emitter technology they got from Toshiba.
And how well did it work with a transistor with less than 60W at 100V SOA vs the 100W at 100V SOA transistor it came with?
I didn't understand SOA back then either.
The reason Crown specified Westinghouse is you got epitaxial, RCA was building hometaxial. For the longest time Motorola built both, the faster epitaxial part was more money. The newer MJ15024 is from the same die family as the epitaxial 2N3773, and the data is shown on the same pages and uses the same graphs for many of the parameters. The MJ21194 is the newest version with the perforated emitter technology they got from Toshiba.