Recent content by Jeff_Birt

In this video we refurbish two odd TRS-80 Model 100s. One of them is a one-of-a-kind prototype from the estate of Tandy engineer Frank Druda (thanks to my friend Eric D.). Second M100 has an odd ‘blonde’ keyboard. Let dig into both and see how much the prototype differs from a production unit...

The Workslate was a very odd choice of products for Convergent, irrespective of the 'all apps are spreadsheets' design philosophy. Thanks for making more information about them available. I have worked on a few with duff microcassette drives (and leaky caps), they were different revs with...

No worries. It is hard to know what or how much of something folks will need so feedback is always welcome. The choice of the male connector on the BPD was to mate with the female on the Model 100 (the original target of the BPD.) Since the BPD has grown to work with so many other devices it can...

If there is enough interest, I will add the matching cables so you can pick them up with the Backpack and adapter. I know it is a bit frustrating at times trying to get a Backpack as they tend to sell out quickly. There was a bit more of a delay this time between batches as we moved to the...

When there are multiple chips sharing the same signal, it can be hard to figure out which one is causing the problem. Presuming your scope settings are the same between the two captures of AD3 it would appear that the signal is being pulled HI. Follow the trace as best you can on the PCB and...

The 74HC will work fine. You might also look for the typical CMOS versions CD40245.

And, video #2:

Looks good! Congrats on the repair. The stickiness is not desired. It is the result of the silicone rubber leaching silicone oil. This is one of the issues that causes them not to work properly. As pointed out in the video the glass goes all the way up against one edge of the metal frame...

Adding UMHW strips to modern FFC cables to make them compatible (correct thickness) for the Tandy Model 102. Part of the non-stop excitement of supporting vintage hardware :)

I have recently done two videos on repairing a stack of 5 PC-1/PC-1211s I had accumulated. The first video came out last week and the second video will be released next weekend. Video #1: In this video we take a stack of 5 Sharp PC-1211 (TRS-80 PC-1) pokecoms and try to turn them into 4 working...

I have fixed 4 out of 5 PC-1211 (PC-1) that had piled up recently. It looks like there are perhaps 3 different PCB variations. I found there are two versions of the CPU 1, and two versions of the LCD drivers. The original CPU 1 version was found on one unit with the mod and one unit without. I...

I have fixed several displays with and without new zebra strips. Now that I have new ones available, I tend to replace them when taking one of the LCDs apart as it is one less thing to possible stop it from working. With a single missing column like that you probably have a bit of corrosion on...

Just did a video about a PX-8 with similar symptoms. Some of the caps had started to leak. Recapped cleaned up corrosion still no boot. Found a RAM test ROM which pointed out a bam DRAM. Note that the DRAMs are very odd NEC parts with a built-in low power self-refresh. I stole one out of a...

Even with flow control you may need an intercharacter delay on some machines. Old UARTs typically have a 2-character buffer. One for last char received and one for the char currently being shifted in. The flow control may not be a feature of the UART but be a function of the OS itself. It is...

Thanks, being able to control the EOL delay like that is indeed handy.