Alright, I here are the results of my measurements on the RK07. My first step was to replace the 6-button/indicator panel with the *original* panel. When I got the drive, the "B" button was a little damaged, so that the white "B" plastic cap did not lock on properly on the button. I had a complete panel, so I swapped the two. That was some months ago. As I connected the RK07 last week or so, I found out that two bulbs were defective, and replaced them after checking with the *Ohm meter* that those were OK. I wrote that the READY lamp did not light up, and I did check that the bulb was OK ... I had fixed the panel with the "difficult" "B" button cap, so I replaced the two panels. The READY lamp goes ON! Great, the RK07 drive is OK, it must be something with the panel. I swapped the two panels again, and yes the READY lamp stays off. Again, I swapped the two panels, and took the suspicious panel to my shack (more test equipment available there). Applied +5V to the panel board ... RUN STOP, WRITE PROT and FAULT turn on, READY, "A", and "B" stay off. For "A" and "B" that is correct as they are connected via an inverter. Applying Gnd to the input pins of E1 (on the Operators Control Panel), and "A" and "B" turn on. But the READY lamps stays off; OK, so E3 is gone. However checking the input (6/7) and output pin (5) shows the correct functioning of this 75452! Is the lamp defective again? This time (on the work bench) I did not use an Ohm meter, but the +5V power supply ... the lamps glowed *very* dim, barely visible! The lamp has a different rating! I installed a +6.3V type in the READY indicator; the panel works! Please don't laugh :-) It turned out in the end that just a simple light bulb of wrong rating got me working for several hours! Lesson learned: check and double-check, do not assume the worst, but start with the very simple things! BTW, an other good thing comes from this exercise: I checked on bitsavers, and there is no field printset of the RK06/RK06. I will scan my set this week and upload it. - Henk. ________________________________ Van: cctalk-bounces at classiccmp.org namens Tony Duell Verzonden: za 21-01-2006 01:35 Aan: cctalk at classiccmp.org Onderwerp: Re: RK07 questions You were lucky. I happened to know where my RK07 prints were... Good luck. Feel free to ask anything abotu this drive's hardware. I find it a particularly interesting one, and spent many enjoyable hours reading that print. -tony This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.