This is topic Good CP-50 Replacement Power Supply in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Mark Gulbrandsen (Member # 72) on 02-17-2002, 06:05 PM:
By request from another Film-techer I am posting this. This is an easy to do replacement for the CP-50 raw power supply. Get yourself a Power-One, Model MAP110-4001 from Allied Electronics, or from a surplus house if you have one in your area that has lots of supplies around. I was able to get mine as new/surplus the other day for 25.00 new in the box! If you can't get one from surplus they're 120 dollars new from Allied. It is a switching type supply which is more efficient than the old toroid based unit anyway and very tightly regulated. I reccommend mounting this outside the CP-50 although it may fit on the right hand rack ear where the old supply sat. I just feel its better tog et the AC out of a high gain piece of gear altogether. Just feed it in though the white molex on the CP-50 backplane the same way the old supply fed in.
I did some testing with the 50's original supply before wiring in the new Power-One unit for more measuremants. They are as follows.
In a normal run of the mill 50 with all stock cards the voltages measured as follows.......
24 Volt Line was 27.85 Volts
12 Volt Line was 11.29 Volts
-12 Volt Line was -10.68 Volts
In this case the CP-50 plays back just fine although the DC rails are a bit off from what they should really be. This Dolby supply had recently been completely overhauled. New diodes, and all new low ESR electrolytic caps. This supply had several hundred hours on it at this point.
Now here is the clinker.....
Throw in a Cat 113C, a pair of Cat 280T's and a new 108C preamp card. and here's what happens.......
24 Volt Line is now 27.35 Volts
12 Volt Line is now 11.04 Volts
-12 Volt Line is now 10.49 Volts
The unit stopped playing at this point as the supply sags to low to operate all these hungry cards. The voltage LED's on the 113C card also appeared unevenly lit as though things were sagging a bit in the rail department.
With the new supply hooked in place of the old one, all three voltages measured with in .05 volts of where they are supposed to be. +24, +12 and -12 volts.
Am going to do some other measurements if I ever have time and add some film bypass caps to the rails on the backplane as well. I don't know at this point if the new supply will help better any of the other CP-50 specs, although the fader card and other related cards will be less likely to clip as soon as they would with the old supply so high quality SR playback will probably benefit. The S/N ratio might be just a tad better too but probably not by much. After a day of operation the new supply runs only luke warm. Its a 110 watt supply so its pretty over rated for the job at hand. There's plenty of reserve for running other accessories such as remote faders, or mag preamps.
Since this is my home unit I'll post more on this later this week after doing some listening tests and other measurements.
Mark @ Home
Posted by Ken Layton (Member # 133) on 02-17-2002, 07:13 PM:
Is this an enclosed switcher or open frame? What's the current rating on each voltage? Does this have a screw terminal strip or molex connector for the output connections?
Posted by Mark Gulbrandsen (Member # 72) on 02-17-2002, 07:22 PM:
Ken,
This is actually a quad output power supply. It is available in a number of different configurations. With cover, without, bare board, Etc. It has Molex connectors. 24 Volts @ 3 Amps, +12 volts at 1 Amp, and - 12 volts at 1 amp. I didn't use the 5 volt 12 amp terminals needless to say. Here is a link to the PDF spec sheet that I should have included in the above posting. http://216.147.54.136/resources/products/datasheet/map110.pdf
Let me know what U think Ken.
Mark @ Home
Posted by Ken Layton (Member # 133) on 02-18-2002, 12:55 AM:
Yeh, looks like a good little power supply. I'm assuming you mount it with nylon standoffs or nylon spacers. It said contact factory for mounting specs with their L bracket option.
Posted by Mark Gulbrandsen (Member # 72) on 02-18-2002, 08:05 AM:
Mine came mounted on a small plate for whatever reason. Otherwise it is just the board itself. They used alumnium standoffs to mount it to the plate. Its a bit heavy for nylon mounts. I'm considering mounting it in place of the original supply as there is adaquate room to do so. I will probably put a piece of some sort of metal in between the CAT 113C and it though for shielding. There are also mounting holes in the top of the "L" bracket and that would allow it to be attached to the top plate of the CP-50 as well for more heatsinking. It only gets luke warm after a days operation. I'm going to dos ome current draw measurements of the 50's rails tonight and will post them in the original post with the voltage measurements.
Mark @ Home
Posted by System Notices (Member # 2357) on 02-19-2010, 07:25 PM:
It has been 2923 days since the last post.
Posted by Jeff Else (Member # 4063) on 02-19-2010, 07:25 PM:
just did this modification and wow! the mysterious (slight) buzz i have tried in vain to eliminate every other possible way for the past month or so is now completely gone, and the CP sounds great!
Posted by Steve Guttag (Member # 268) on 02-19-2010, 09:26 PM:
Yeah...we are doing something similar with the CP200 power supply the PS1(B). We are gutting and installing switch mode power supplies. It will look and feel like it always has but the output rails...instead of +/- 11-12.5V (Depending on how loaded your CP200 is and if your caps are fresh) will have a regulated +/- 14V rails. So far, the noise improvement with this have been rather dramatic...less hum for sure and less hiss too. We are still tweaking on which supplies we are going to use to get the performance we want but we are almost there.
Steve
Posted by Jeff Else (Member # 4063) on 02-19-2010, 09:31 PM:
i agree that the improvement with a regulated supply is dramatic... why is (or was) this not standard issue on such expensive equipment?
Posted by Gordon McLeod (Member # 33) on 02-19-2010, 09:59 PM:
two reasons with the original card layout the supply was ample for the needs and the cost
Also switchmode supplies were not all that common when th cp50 was introduced
Posted by Steve Guttag (Member # 268) on 02-19-2010, 10:34 PM:
In 1976?...no switch mode was definitely not the norm.
Also...it is much more recent as to having "quiet" switch mode supplies. That is, them not putting their own noise onto the power rails. This has kept linear supplies going in audio applications.
Steve
Posted by Mark Gulbrandsen (Member # 72) on 02-20-2010, 09:53 PM:
Switch mode power supplies were actually used as far back as the Mercury Space capsule. Don't know about before that time period...
Mark
Posted by Gordon McLeod (Member # 33) on 02-21-2010, 02:29 AM:
not in main stream were they commonly used and often they were very noisy
Posted by Mark Gulbrandsen (Member # 72) on 02-21-2010, 10:33 AM:
I agree Gord... definately not mainstream back then. even computer power supplies were huge linear units back then. Broadcast gear always used linear supplies with the exception of the RCA TK-76 mini-cam. That may have been the first wide use of a switch mode supply in a mass produced item and they had to in order to make the camera light weight and portable. Military gear no doubt also used them extensively. When Sony started making headway into the Broadcast Market switch mode power supplies seemed to became the norm.
Mark