HSC Gear Part II

A quick recap. Sean Boyer made 3D gears for the HSC mechanism I was working on. They worked great as replacements for the broken stock gear. I danced a jig. And Scott Walker got the HSC unit he had been dreaming of for quite some time. This is a Home Stereo Console Seeburg made for home use. It holds and plays fifty 33 1/3rd albums. It also has an AM/FM radio with inputs to the amplifier for two more components such as a tape deck or CD player. He is in New York. He arranged shipping and off it went. After he got it and set it up he loaded some LP’s and started enjoying it. I got a message that the mech stopped moving a couple days later. I had wired the mech in place to keep it from moving and stressing the gear so this couldn’t be attributed to traveling from Texas to New York. I had a bad feeling….Thanks to instant messaging and digital pictures it becomes fairly easy to help someone. Especially when they’re willing and have a modicum of mechanical ability. And oh boy! Did he need it. I didn’t think the gear had failed. I showed him a picture of the tool I made to manually move the mech. It’s very similar to the rare Seeburg tool but with a T handle. He made one and the mech still wouldn’t move. So, it could only be the gear. This is a quick write-up but all this action took place over a period of about the last three weeks.

Replacing the reduction gear in the motor isn’t that hard but when you’ve never done it much less know the nomenclature it can be daunting. Several messages and pictures and I walked Scott through replacing the gear. One has to take the rubber belts off, the three screws holding the turntable on, loosen the clutch screws because the motor has a shaft that fits the clutch slot; and to reach the clutch the mech hasd to be all the way left, remove the turntable motor mounting bracket, then the three screws holding the scan motor in and finagle it out past the clutch. Three screws hold the top of the motor case on. I had sent a couple extra gears along for “just in case”. I got him to suspend the mechanism like it is originally suspended. I thought perhaps sitting on a hard surface the mech was transferring too much force to the gear when the mech changed directions. I had one of these in my old shop in Seagoville and well remember hearing the mech swinging about upon direction change.

Scott replaced the gear. It lasted all of two days and stripped. Scott, being a pro at changing gears now handled another replacement with aplomb. I had been back and forth with Sean about this turn of events. He is the maker and hopes to market these gears. He decided to make some out of nylon. It took him less than a week to get several turned out. He sent me nine I think,v and I got several to Scott as quickly as I could. However, the current gear seems to be going strong. It is the same material as the others but a different color. I don’t know if this signifies anything or not. Sean says the red, yellow, and black gears are all the same material but…???

I advised Scott to clean the motor case out real well to get any bits of chewed up plastic out on this last replacement. I’m certain he cleaned and lubed it well. Until the current gear busts we won’t know about the nylon gears for awhile. At least until I haul the HSC 6000 out of storage and start on it. Same basic mech, same control center and selector. It has a different amp/radio in it. Whenever I get the SMC3 done and gone I’ll haul it out.

Kudos to Scott for being so willing to dive in and replace the gear and fix the other little problems that have cropped up.

Myth Dispelling Time

I’ve seen one too many posts about silver tarnish being conductive. One of the things I do on every SHP amplifier redo is desolder the tone controls, take them apart and clean the contacts by hand. I have learned this the hard way. Too many times I have douched them down while actuating the slide controls furiously to try and clean them. I really thought I was accomplishing something. Measuring after cleaning it was apparent not much was happening with the “drown” method. The method of desoldering and disassembly is a very positive way to make sure they are clean. 100% accuracy.

Try your slide controls for the bass and treble. Hear any difference when you switch them from setting to setting? If not then they are dirty. The first time I cleaned them this way I was very surprised when I heard distinct changes in tone when switching either one; treble or bass. That is all I needed to be convinced. These amps actually have quite good tone when given a chance. Since the SHP series amplifiers are 40+ years old they need all the help we can give them.

Back to the silver tarnish. Too many people repeat what they hear or read having no practical knowledge of the subject. The contacts on the tone controls are silver plated and tarnish like any other silver does slowly turning black. I’ve seen one too many posts on a favorite Facebook page that states silver tarnish is conductive. Nonsense! In the first picture I show one side of the slide control, the middle, connected to an ohmmeter. You can see it measures almost a 1,000,000 ohms-a lot of resistance. It should read less than 1 ohm resistance.

Here is a picture of the disassembled tone control. Note the build up of tarnish.

A short discourse…..Desoldering these is just like removing any other component on a circuit board. Once removed I used a small pair of dikes or diagonal cutters to pry the two legs away from the slide lever holding the unit together. These contacts can be then cleaned by a variety of methods. Use a soft wire brush, a fiberglass eraser, a big “Pink Pet” pencil eraser, a cotton swab dowsed in your favorite cleaner. Put the two halves back together, bend the two legs back. Look at the other two unbent legs as a guide as to how far to bend them back. Not enough and the tone control will come apart. Too far and the little board gets pushed out of place.

Here is a picture of the same contact measurement after cleaning. You can see quite a difference. With practically zero resistance you will get very distinct differences when switching the tone controls and can have an amp much more “tune-able” as to how you like your music to sound. And it’s easy to see that the silver tarnish caused quite a resistance.