I'd be very surprised to find a drive, which would have a pull-up on drive select line higher than tens of kΩ. They are required to have one. I've tried another drive ("modern" HD drive - SFD-321B), and it required over 5mA to pull Drive Select to low, so a 1kΩ pull-up was there (again - n...

Well it works without the external pull-up, so where is the problem? It was working like that for the last 30 years... Shugart' specification says that the DS line is OC, so there should be no pull-ups on the host controller side. The drive itself also doesn't have external pull-ups, but when powere...

I've measured it on the actual drive. But it is logical. The Specification says that the Drive Select line (among other lines) is an open collector type, so the drive has to deal with it. One more thing - you don't need any adapters. All you need is a switch shorting and opening a jumper/shunt on th...

Controller IC in that drive has an internal pull-up of about 16kΩ. The Drive Select line on the host/controller side is supposed to be open collector. Atari is a little "noisy" so it is better to use additional pull-ups, but both options should work. SIMPLE __________ PIN 10 PIN 10 _______...

Drives are expected to have pull-up resistors on the Drive Select lines, so there's really no need for this resistor. Yet it is safer to put 4,7k pull-up resistors on the drive sides of the switch (1 resistor for each drive). They should not be switched. Motor-On line is common for all 4 drives acco...

I'd say 100uF 6V. I'd have more doubts about the bigger one.

I've got one marked as:
70T <- date code
100 <- capacitance
6V <- voltage rating
and these are 100uF/6V.

wietze wrote: ↑Wed Jan 13, 2021 9:21 pm I am using RAM simms that I have succesfully tested using Yaart on another machine.

I see no SIMMs there (SIMMs are used in the STe, here you have just chips in DIP packages), but what I see is the AT-Speed hardware emulator. Have you tried removing it?

I'd really like to help, but unfortunately I have to give up. I currently own only one STe, with external Blitter (early board, with some factory bodges), the second one, with integrated Blitter, does not belong to me, and I've verified that it has CPU soldered on the board. So I can't risk damaging...

As far as I remember STe machines with internal (integrated) Blitter, have no socket on CPU... and I guess you won't be willing to send anything to PL How fast the ROMs need to be in order to this booster work?

Technically they are EPROMs, but have no quartz window, so they are called OTP EPROMS.The PROM term seems to be obsolete and reserved, for "fusible" memories. There is a Flash EPROM replacement for 27C256 - this is Winbond W27C256 (and 27C512). Despite also being 27C marked, they are Flash...