Rebuilding An Obsolete IC To Save A Betacam SP Tapedeck

Betacam is not the Betamax you may have had at home– it was a professional format that lived on into the 21st century, in the “SP” form. In many places, it would have been the last tape format in use. So it is perhaps understandable that [ldursw] decided to recreate an obsolete and unobtainable IC to save a Sony broadcast-grade editing Video Tape Recorder (VTR). Still mad, perhaps, but in a way we very much appreciate.

The Sony BVW-75 VTR had an odd flaw where the output lacked colour, unless paused with dynamic tracking off. Then colour would appear, but only in odd stripes. Clearly the chroma circuit was at fault. Some sluthing found that a sync separator IC– that separates the sync pulses that keep everything moving together, if the name didn’t give it away– wasn’t behaving correctly. More sluthing found that the chip in question was no longer available. Luckily, the concept of a sync separator hasn’t quite given up the ghost, and another part was available. It just didn’t fit, used a different voltage, and had an inverted output. No biggie! [ldursw] added a voltage regulator, an inverter, and a video amplifier chip, then after breadboard testing put them on a PCB with pins that match the original IC’s form-factor, making it a plug-in replacement.

That’s a GitHub link at the start of this article, by the way, so he’s open sourced the solution for anyone who needs a Toshiba TA7357P video sync separator. We don’t know who else needs this, but we’re willing to bet that whoever does, really needs it. On behalf of whoever that might be, we offer sincere thanks to [ldursw] for the hack, and for submitting it to our tips line.

This reminds us a little bit of a tape deck repair we featured previously, reviving another Sony format– D-1 tapes–to archive old media.

We can see the internal pads from an integrated circuit where the epoxy has been ground away.

When Repairs Go Inside Integrated Circuits

What can you do if your circuit repair diagnosis indicates an open circuit within an integrated circuit (IC)? Your IC got too hot and internal wiring has come loose. You could replace the IC, sure. But what if the IC contains encryption secrets? Then you would be forced to grind back the epoxy and fix those open circuits yourself. That is, if you’re skilled enough!

In this video our hacker [YCS] fixes a Mercedes-Benz encryption chip from an electronic car key. First, the black epoxy surface is polished off, all the way back to the PCB with a very fine gradient. As the gold threads begin to be visible we need to slow down and be very careful.

The repair job is to reconnect the PCB points with the silicon body inside the chip. The PCB joints aren’t as delicate and precious as the silicon body points, those are the riskiest part. If you make a mistake with those then repair will be impossible. Then you tin the pads using solder for the PCB points and pure tin and hot air for the silicon body points.

Once that’s done you can use fine silver wire to join the points. If testing indicates success then you can complete the job with glue to hold the new wiring in place. Everything is easy when you know how!

Does repair work get more dangerous and fiddly than this? Well, sometimes.

Continue reading “When Repairs Go Inside Integrated Circuits”