Oberheim TVS-1

This Oberheim TVS-1 I bought at a bargain price. The guy who sold me this told me he had tested it and that it did indeed made sounds, but he did not know how it worked or how to control it externally. I got it for 1100 Euro Which is a bargain here in Sweden as I've seen people wanting double that amount for their TVS-1. Anyway, getting home with the TVS-1 I discovered something was not right with this machine. One module sounded constantly and the keyboard acted really weird. Triggering the same key could result in many different tones anything from the lowest bass tone to the highest pitch. When I switched on to the mini sequencer it all worked fine and so it did when I random controlled both modules. So it seemed the Keyboard was at fault somewhere.

It might seem small in size, but do not underestimate it's weight. The main reason for it being heavy is the steel plate to which everything is fastened to including the wooden case.

Ok, it might not look as if it needs restoration work ... But inside this machine is a lot of stuff to be done.

It does not look that bad actually, right ? ... Wrong !! Underneath all those knobs lurks dust and behind the panel a lot of tantalum caps. Look at the power switch, can you see that it looks sort of yellowish around that part ?

The bender assembly, rusty screws and rusty details on the case. A lot of fat stuck on those knobs. Keys are dirty, the tolex looks old and worn out.

This is the Bender section after restoration. One of the flat head screws were found inside the synthesizer, the others had been used to fasten the SEM modules to the mainframe so clearly some one has done some work on this TVS in the past.

The handle looks rusty too. This synthesizer was stored away in the attic of a house for more than 15 years I was told. I guess that is why it was so rusty.

When I bought this synthesizer I didn't even get a power cord with it.

Three blue tantalum caps and two electrolytic ones per SEM module and a lot of open type trim pots that need replacement. I always measure the pots before removal and then the new one once it is in place, this makes it easier to fine tune the module when it is powered up. Fine tuning the SEM modules is not that different from tuning an Ob-X I might add. But here you do not need to care about any test switches.

Another view of the SEM module and the orientation of all those wires.

The keyboard electronics which is located under the bender section of the TVS-1.

Another view of the same module. In the manual there is no procedure for the tuning of all these trim pots. I hope to be able to write down what each one does when I am getting to the tuning procedure of the TVS-1.

The Main output module and the wires.

The Mini Sequencer module and the orientation of the wires.

Only a skeleton remains. Here´s also the reason for it´s weight the steel plate at the bottom of the TVS-1. getting this out of that case requires you to unscrew the handle and four screws on the bottom of the TVS case. After that you simply pull it out of the wooden case.

Here´s one of the reasons why the keyboard would not work. The J-wires are too long which made them short circuit between the gate and the CV wires, also note that there is a lot of rust on the CV/Gate leads. The leads including the J-wires were cleaned using steel wool.

And this is the result of cleaning them with steel wool. The plastic parts holding the CV & Gate leads are not hard to remove, they are screwed to the Key bed, simply unscrew them and the white plastic parts can be moved around for easier cleaning of these wires.

More of that shiny result.

And even more. Each J-wire was also cleaned to make better contact with the leads.

Removing the springs from the keyboard.

Removing the plastic keys.

Removing the metallic key supports and revealing some other bad guys underneath that.

Keys taking a bath.

Only bad bushings, dust and dirt remains.

Old bushings removed. Some were so dry they crumbled when thouched. 

The New bushings in place and the Key bed is cleaned.

The end result is nice and clean. Notice some shine on those keys.

The old bender section.

The New bender section. Exchanged all those trim pots and caps.

The main output module not restored.

Main output module electronic restoration.

Main output module restored.

The mini sequencer before picture.

Mini sequencer electronics before restoration.

Mini sequencer after restoration.

Mini sequencer pots, not much to do here but to re-lubricate the pots.

The Mini sequencer restored and finished. The plastic parts can actually be found today at Farnel, so if they are too far gone you might be able to still get hold of these knobs new. The way to remove these pots is to open up the top plastic part and then with a screwdriver unscrew the screw found inside the body of the knob and then simply to lift the knob away using minimal force. The knob is made up of four parts, the skirt, the main body, the fastening screw inside the main body and the top plastic part which hides away the screw in the body. Each of these parts can be ordered separately from Farnel.

Here I have removed the old electrolytic caps and replaced the tantalum ones and the trim pots as well.

A SEM module before restoration.

Before removing any parts.

Removing the top PCB reveals the pots underneath on a second PCB. The two at the top are for the Oscillator tuning.

More pictures will come on the restoration of a SEM module shortly ...

The front panel as it was.

As it is today.

... More pictures will eventually come up...