Tektronix and Iwatsu repairs being attempted

[Jim Ford]

Hi, folks. Like I said in my intro, I'm between jobs for another couple of weeks, and I've been trying to repair some faulty test equipment in my garage lab while I have the time.

First on the list is a Tek TLA711 logic analyzer system. It seems the backup battery in the Benchtop Controller (basically a Windows 98 PC) was dead. It wouldn't boot up at all. Turns out the battery was inside a realtime clock IC module which is no longer available. But fortunately there were several crosses to that particular RTC. Now, I had to add a battery holder, a CR2032 coin cell battery, and a 32.768 kHz crystal. No more complaints from the BIOS about the RTC.

But the problem now is that the BIOS doesn't seem to recognize that there is a hard drive attached. I wasn't able to get the BIOS setup to Autodetect like the Tek TLA711 service manual said. I suppose I will have to open up the Benchtop Controller yet again to see if I bumped a cable or a jumper off inadvertently. I was hoping I didn't have to do so again (when I replaced the RTC, I didn't realize that it needed the battery and crystal, so that's 2 times disassembling and reassembling; this will be 3 times).

Unless somebody has a better idea? I'll see if I can get some screenshots in here with the error messages.

Next up is my Iwatsu SS-5710D 60 MHz analog scope. Evidently the D model is the one with the multimeter and frequency counter built-in (I'd have sworn it said SS-57100 on it, but Google showed no such animal, and I finally figured out that was a "D" not another "0"!). This scope works, but there seems to be a problem with the horizontal circuit. The traces on either channel 1 or 2 don't go past about 2 divisions on the right side of the screen, and they bunch up a bit at the right end.

Now, I found an instruction manual for the SS-5710, but it doesn't mention anything about the D version. Has schematics so I should be able to figure it out. Of course I'm all ears if somebody on the forum has experience with a similar problem. Let me see about screenshots.

Thanks. -Jim

 

[Jim Ford]

Update on the Iwatsu scope (SS-5710D): I tracked the problem down to saturation in the horizontal amplifier. The schematic shows it in section 11; Iwatsu puts a number on each page of the schematic, but these don't correspond 1:1 with the circuit boards. Section 11 is on at least 2 different boards, and section 5 is also part of one of the section 11 boards. I checked points 2 and 4 on the schematic (3 and 5 are the same points, just with the 10X horizontal magnification on - I'm not concerning myself with that right now).

 

[Jim Ford]

So here are some .jpg's of 1) the Iwatsu SS-5710 schematic, section 11, 2) a zoomed-in view of the section 11 schematic so that the point 2 and point 4 designations can be read, 3) a photo of the '5710D screen with the trace saturating at the right side, about 1 division from the end of the screen, and 4) a photo of the difference between point 2 and point 4, taken from a different scope (Tek 7904 with 7A26 vertical amp and 7B85 timebase). You can see the horizontal sweep in photo 4) saturating at about 100 V differential. How do I get it to go beyond that so that the sweep goes all the way across the '5710D screen? Is there another adjustment, perhaps on a further amplification stage beyond section 11? I'm just not that familiar with CRT's to know. TIA.