Crown CX824

SeleniumFalcon

I thought I'd listen to some 4 track tapes on my venerable Crown deck and discovered it was making a very low level humming sound. Not very audible but enough to get in the way of enjoying the sound quality. I'd also been bugged about the VU meter illumination not being even across the two meters. I suspected the humming problem was related to the power supply for the electronics section. The hum was equal for both channels and wasn't effected by the playback levels. So, I split the two section of the deck, the transport from the electronics and began testing power supply capacitors. I ended up finding a 100uF 50 V electrolytic that was low on value and had a bulging end cap. I decided the best approach was to go over everything and replace the lot, including the tantalum capacitors used in the audio path (the WIMA capacitors are the red guys).

SeleniumFalcon

The difficulty in testing the CX electronics is that the AC power is routed (via the black multi pin connector shown in the above photo) through the tape transport section down to the electronics section. So, I had to rig a temporary way of connecting the electronics to AC with test leads. Once that seemed handled I started on the transport section, removing it from the wooden cabinet and installing it on a rack mounting test assembly. Most of the internal electronics are on drop down frames.




You can see the 4lb capstan flywheel on the left and the drive belt that changes the three speeds. The Crown is a curious mix of electronic and mechanical solutions, the transport has a very effective logic control that allows any combination of commands to be entered. If you're fast forwarding (for example) and press "play" the logic system "remembers" your command, but first engages the braking system, brings the reels to a stop and then engages the"play" function. But, conversely to go from playing at 3 3/4 IPS to 7 1/2 IPS a metal arm is pulled from the front of the deck which moves the belt to the larger diameter section of the capstan pulley. And to go to 15 IPS the deck has to be turned around and manually repositioned on the pulley.

SeleniumFalcon

Here's a photo showing this belt moving assembly.

SeleniumFalcon

I've been wanting to try using an external playback component with the Crown transport to make an "end game" playback deck for 4 track tapes. But, the bottleneck was the fact that Crown used a hard to find (make that impossible to find) connectors made by the Winchester company. I didn't want to do anything to change the originality of the stock connections but wanted to be able to unplug the electronics and try the de Havilland 222. Lo and behold I finally identified the specific Winchester socket on Ebay and ordered it from Israel. After six weeks shipping time it arrived and I could make up a pair of RCA cables.

SeleniumFalcon

This is a photo of the inside of the transport showing the structure that provides the bearings for the capstan shaft. To me this one of the most impressive designs in any tape deck I've seen. Here is a description found in the 1968 Audio Magazine's review:

SeleniumFalcon

This photo shows the rear of the tape transport with the top plate removed and the logic circuit board to the right of center. The main AC transformer is attached to the top plate there is plenty of room to see the three motors.

SeleniumFalcon

On the right hand motor is an attachment which incorporates a lamp (detached at present) and two photo sensors. This is used a tape direction sensor for the logic circuit.

SeleniumFalcon

This photo shows the capstan motor which is a 117v synchronous motor and has a plastic housing to reduce motor noise. There is a fan blade attached to the front of the motor which pulls cooling air over the internals of the motor and exits on the left side.

SeleniumFalcon

This is another photo of the supply motor and the direction sensing attachment.

SeleniumFalcon

This is a photo of the transport controls assembly showing the two large DC lamps or bulbs. This deck doesn't have standard mechanical brakes, such as the bands on the Revox for example. Rather a DC voltage is applied to the AC motors which causes the motor to stop spinning. However, more DC voltage is required when the brakes are first applied. So the braking DC voltage is sent through a bulb which as it warms up presents a greater resistance hence decreasing the DC voltage allowing for a gradual slowing down of the motors.

SeleniumFalcon

This is the front of this assembly showing the transport control buttons and how easy it is to change the button illumination lamps.

erniejade

Nice work!!

SeleniumFalcon

Thanks! There doesn't seem to be very many photos around detailing the insides of this deck. My suspicion is that most owners don't ever get inside their decks and start taking things apart, they have reliable people like Chuck Ziska servicing them. So,I thought I'd post some..

F1nut

Fascinating as usual.

motorstereo

Nice job on getting that old Crown working. I had a couple live here for a while a couple years back and I thought they were exceptionally well built. From what little work I did on mine it seemed their engineers took into consideration that they will have to be serviced which was nice.

SeleniumFalcon

Starting to put everything back together in the cabinet after cleaning the wood and painting the inside bottom which was scuffed. I also installed four feet on the bottom to lift the deck off of the shelf. I've polished and waxed many of the metal chassis plates to restore some of the new look wherever possible.
I was able to replace the main AC power cord and all of the internal lamps.

SeleniumFalcon

vmaxer

that looks great, nice work!!

SeleniumFalcon

This has to be one of the easiest head assemblies to clean, after removing the two covers everything is accessible. The pinch roller is cleaned with Formula 409 and the heads and tape path are cleaned with denatured alcohol. Note the beautiful glass rod tape lifters and the rigidity of the support mechanism. I had removed the complete capstan/flywheel assembly and lubricated the sintered bronze bearings and polished the nickel plated flywheel and bracket and washed the drive belt.

SeleniumFalcon

The cabinet was made by a retired Crown cabinet maker who used solid padauk for the sides and top.

SeleniumFalcon

One of my initial goals was to even out the brightness of the VU meters, it just looked unbalanced. Once getting inside I could see the problem, Crown has used three lamp holders with the center one located closer to one meter than the other. This accounts for the unbalanced look. After replacing the lamps and working to position the three holders I finally got a satisfactory overall look.

SCompRacer

Highest marks! I had a Krell MM/MC phono board that used tantalum caps. I've read some folks replace tantalum with a low-ESR ceramic output capacitor.

Clipdat

Flawless.

JayCee

Missed this thread when you first posted. Awesome work and so nice to see such talent on display.

Re. the hard to find connector...

SeleniumFalcon wrote: »

...bottleneck was the fact that Crown used a hard to find (make that impossible to find) connectors made by the Winchester company. I didn't want to do anything to change the originality of the stock connections but wanted to be able to unplug the electronics and try the de Havilland 222.

I have no hands-on experience w/them but I have a "Polk" logo created on the 3d printer we viewed at PF '12. Also, w/Trey using a printer in his builds...I guess, for unobtainium parts, it would be a solution? Wonder how hard/realistic/cost effective it is to CAD a one-off part?

SeleniumFalcon

Thanks for the suggestion, @JayCee I've wanted a legitimate reason to get involved with 3D printing. I've used 2 part molding plastic to make things like binding post caps for ribbon tweeters before. You mix up a putty like material, then put it around the part you want to copy. This will give you a flexible mold to pour liquid plastic into, then drill out the center, tap it and paint. This is a procedure I use with model railroading to make boulders, scenery etc.

BlueBirdMusic

Very nice!!