This is the second blog post from Stanford Media Preservation Lab in our series documenting our progress as we refurbish our ½” reel-to-reel videotape machine. When we left off, we had given our Sony AV-3650 a good cleaning and re-lubricated most of the mechanical workings of the tape transport.
The goal for these next sessions was to remove the old jacks from the machine’s connector panel and replace them with modern jacks that wouldn’t require adapters and could be used with our newer equipment in the video lab. Although the connectors were still functional, they were old and worn from use.
The image of the panel below shows several different types of audio and video jacks, a spring loaded fuse holder, auxiliary AC power out, and the AC input plug. There's a 1/8” mono mic input and an auxiliary line audio input installed in the top left of the panel. We decided to leave the mic input alone, as we didn’t have any need to replace it. However, we did want to give the auxiliary audio input a new connector for use in testing and calibration, as well as a new connector for the audio line out, and a new BNC connector on the RF out for use in monitoring while making adjustments to the tape path.
The video input and output used a threaded UHF connector commonly seen on equipment manufactured in the 1970s. These old jacks are about 15 mm in diameter and will accept UHF to BNC adapters, but we decided to remove them and install new BNC connectors so we wouldn’t need to use adapters on our machine.
Although we’ll never attach a camera to this VTR, the 6-pin DIN camera jack was left installed because there wasn’t a good reason to remove it. This jack was used to connect a camera with a multiconductor cable carrying horizontal and vertical drive pulses from the VTR to the camera, as well as the composite video image from the camera to the VTR for recording. The 8-pin jack labeled “TV” was used to connect a TV to the machine for off-air recording, since there was no TV tuner integrated into the deck itself. We didn’t remove or modify this jack.
The fuse is a regular 1.5 amp cartridge fuse that is still intact, but we’ll probably replace it since we’re replacing other components on the machine.
There is a empty receptacle on the panel between the fuse and the TV connector. It looks like a placeholder for another jack. It may have been left there for an optional AC selector switch since Japan uses 50 Hz as well as 60 Hz electricity. Machines made for use there would’ve been capable of choosing one utility frequency or the other. Below that space is an AC out jack. Since we won’t need to use the AC out, we have left it alone, as well.
The AC input will be the first plug we update. When we purchased the machine, it didn’t come with an AC cable, but we were able to find an extension cable with the necessarily smaller NEMA 5-15 female plug to fit in the jack. We’re replacing it with a more modern IEC connector found on a lot of electronics manufactured today.
Seven screws secure the connector panel to the back of the deck, and there are small hinges on the bottom of the panel that allow it to tilt down for access to the connectors and their wiring.
The plastic “ornamental plate” that labels the jacks had to be removed in order to access the screws that keep some of the parts in place. The plate is screwed onto the panel, but also attached to the steel with a light back coating of glue. We used a flathead screwdriver to pry up one corner, and then gently pulled it apart from the rest of the panel.
Prior to removing the AC jack, Ken tested the wiring assignment of the AC terminal on the machine. We plugged the NEMA 5-15 cable into the deck’s old AC jack, and using our ohmmeter, we were able to identify the assignment of each wire by matching them to the hot, neutral and ground counterparts on the cable’s plug. After noting the proper placement of the wires attached to the back of the old AC connector, we went on to take out the NEMA jack. Two screws removed it from the panel, and the three wires were unscrewed from their terminals.
The image below shows Ken holding up the new AC jack to the steel panel. Our new part needed to be fitted because it was too large to slide through the round receptacle. However, we were fortunate to find that the screws in this AC jack housing aligned fairly well to the existing holes in the panel.
We measured the dimensions of the AC jack using our calipers, and placed tape over the receptacle to mark where we’d need to make some space. Using our metal file, we added corner notches to the circular hole so that the rectangular body of our new jack would slip through and fit flush against the steel.
As we worked, we made sure that we weren’t over-filing the panel because we didn’t want our new connector to fit loosely. When the piece fit snuggly into place, we used some 3mm screws to secure it to the panel. The bottom screw fit nicely through the housing of our AC jack and through the steel panel, but the top screw hole needed some help from our drill. We'll cover the space leftover from the original round connector after our new AC jack is installed.
We used hex nuts to tighten the screws to the panel. Here are two images showing the new connector installed and soldered. Black gaff tape was used to cover up the space left over from the original jack.
We moved on to replacing the video and audio connectors. These images show a used BNC connector that Ken brought for test fitting, and an example of the RCA connectors we installed. Our new parts were purchased from both local parts vendors and an electronic components supplier based in Texas.
The old UHF connectors were threaded through the panel and held in place with a large hex nut on the back of the connector. After desoldering their wires, Ken removed them by gripping the outer part of the jack with pliers, and then using a wrench to unscrew the nut on the inside of the panel.
The BNC connector was installed using another hex nut to lock it to the outside surface of the panel. We re-attached the plastic plate because the nut needed to fit over it in order to hold the connectors in place. Here, Ken is installing the part, and in the image below, you can see the BNC connectors fully attached. Ken supplied the third BNC connector that we installed to replace the 1/8” mini jack for our RF output.
In order to fit our new audio connectors into the panel, we used a tapered reamer to increase the size of the outlets. We measured the target diameter for each hole in the panel and placed tape at the corresponding diameter on the reamer so we’d know when to stop boring out the new hole.
This image shows the backside of the panel after we installed our new connectors. The new video out jack can be seen on the right (the spacer has a terminal for ground), the BNC connector for RF out is on the left, above the audio line out connector seen in the foreground with the orange wires (In this machine’s configuration, one comes from a point on the audio board and the other runs to one of the pins of the TV output connector).
Here is an image of our completed update of the input/output panel.
We had time to turn on the machine and make sure the new AC jack was working, but we decided to wait on testing the audio and video jacks until we’d completed our next stage of work. With the connector panel squared away, it was time to focus on the electronics and start replacing the machine’s capacitors.
I like these because they are very affordable and accurate, and they will give readings in inches or millimeters.