Tektronix 7000 mainframe and 500 plugins REPAIR manuals? - Page 1
Forum section: electronics / testgear

author: lapoltba
author_rank: Contributor
timestamp: October 09, 2014, 10:47:37 am
content: I have searched quite a bit for these and so far I have only been able to find copies of the instruction/operating manuals. I see repair manuals being sold on Ebay, but I'm cheap. The mainframes I have were working at one point, but I'm pretty sure the caps in the power supply have gone bad. I have 1 working DMM, but the other is FUBAR. The SG503 works on 1x range only and I would like to fix that. One of my FG504 works beautifully, but the other is intermittent. That is one I would really like to have working, they are slick units.If anyone has any links to REPAIR manuals for these I would really appreciate it!I have the following:2x 7854 mainframes2x dm502 multimeter plugin2x PS503 triple output power supply1x SG503 leveled sine generator1x TG501 Time Mark Generator2x FG504 40Mhz sweep function Gen.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: October 09, 2014, 12:03:53 pm
content: A reasonably decent scan of the 7854 service manual here:http://bama.edebris.com/manuals/tek/7854/-Mark-

author: lapoltba
author_rank: Contributor
timestamp: October 09, 2014, 12:05:33 pm
content: Hmm, not sure how I missed that on the BAMA website... Looks like I'll have some fiddling to do tonight.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: October 09, 2014, 12:09:22 pm
content: The 7854 manual is a necessity every owner of one needs... it's a beautiful scope... when it works-Mark-

author: lapoltba
author_rank: Contributor
timestamp: October 09, 2014, 02:17:35 pm
content: Agreed! I saved both of mine from the scrap heap at school a few years ago. Only one worked then, but now both are acting the same. Powers on but won't pass self test and nothing on the screen. That was as far as I got with them. I would be happy to get one working 100% again. I originally took both to keep one for parts anyway.I got a ton of plugins, two of the remote consoles for the 7854s and two 500 series racks in the same haul. I love all the stuff I have, but I don't love moving it around.

author: edavid
author_rank: Super Contributor
timestamp: October 09, 2014, 03:37:18 pm
content: Quote from: lapoltba on October 09, 2014, 02:17:35 pmThat sounds like ROM rot.Do the LEDs light up?

author: 1xrtt
author_rank: Regular Contributor
timestamp: October 09, 2014, 06:56:49 pm
content: The instruction manuals for the 500 series plugin are available on Bama and K04BB. I never found a service/repair manual for any of them. But the instruction manuals have the schematics, part list, board layout, even mechanical drawings.If service/repair manuals does exist for these plugins, I'll be wanting them too!

author: edavid
author_rank: Super Contributor
timestamp: October 09, 2014, 07:15:16 pm
content: Quote from: 1xrtt on October 09, 2014, 06:56:49 pmNo, there were no manuals called repair manuals. Tek usually had instruction manuals (which included service information) and operator manuals (which left it out). The 7854 is an exception to this... there are separate operator and service manuals, because a combined manual would have been too big.

author: lapoltba
author_rank: Contributor
timestamp: October 09, 2014, 08:07:37 pm
content: Quote from: edavid on October 09, 2014, 07:15:16 pmGood to know. I'll have to take a closer look at them then.Regarding the 7854s: Yes, It starts to boot, beeps a few times and some of the horiz/vert trigger lights flash off. The Busy, ERR, I/O, SRQ and Remote only red LEDs remain on and it halts. The Vert. and Horiz. mode selectors are unresponsive. Nothing on the screen.

author: lapoltba
author_rank: Contributor
timestamp: October 09, 2014, 08:35:29 pm
content: Alright, thanks for the nudge in the right direction David. According to the troubleshooting chart I have RAM, ROM, and RTC faults.

author: edavid
author_rank: Super Contributor
timestamp: October 09, 2014, 08:50:28 pm
content: Quote from: lapoltba on October 09, 2014, 08:07:37 pmIt does seem like ROM rot. You can replace the ROMs with EPROMs. The ROM images and information can be found here:http://www.davmar.org/TE/Tek7854/Tek7854-ROMs.zip

author: lapoltba
author_rank: Contributor
timestamp: October 09, 2014, 09:23:38 pm
content: Excellent, thank you for the link. I had found another source, but I couldn't get to the FTP site for some reason.Any suggestions on where to source those eproms? A quick search wasn't too helpful. I figured since you had the info for the roms so handy you may just have a source for the chips too!

author: edavid
author_rank: Super Contributor
timestamp: October 09, 2014, 09:35:46 pm
content: Quote from: lapoltba on October 09, 2014, 09:23:38 pmI don't know of any current US sources for MCM68766s, but there are plenty on eBay, or you could tryutsource.net/MCM68766.html. Make sure you have access to a programmer that supports them though. It's probably easier and cheaper to buy 4 of the adapter PCBs (http://store.go4retro.com/2364-adapter) and use 2764s.

author: David Hess
author_rank: Super Contributor
timestamp: October 10, 2014, 06:00:36 am
content: If you cannot find free scans of the manuals online, Artek Manuals has most if not all of them available for a low price:http://artekmanuals.com/manuals/tektronix-manuals/All of the instruments in your list should be repairable. I have personally worked on the 7854, DM502, PS503, and SG503. Typical problems in rough order excluding dirty switches and potentiometers are:Bad Aluminum Electrolytic CapacitorsShorted Solid Tantalum CapacitorsBad SemiconductorsBeware that some of the instruments you mention had revisions and change notices which will not be covered in manuals intended for older versions. This is especially the case with the 7854 where the late model replaced the troublesome cursed Mostek ROMs (and PLA) which are subject to bit rot with a pair of 27128 EPROMs and the older SRAM board with a pair of 6264 SRAMs. Obviously the later 7854 is desirable from a reliability standpoint. There was actually a discussion on the TekScopes@yahoogroups.com about the feasibly of cloning the late model 7854 memory board to replace the ROM and RAM boards found in the early model 7854s.

author: lapoltba
author_rank: Contributor
timestamp: October 10, 2014, 11:12:32 am
content: Interesting, thanks for the info. I'm assuming I have the older versions as the Eproms are dated 83 and the board 70 something. I don't really know what I'm looking at though. I pulled the ROM board out to see about getting replacements for everything. I know the pots and switches need cleaning all around.Is there a good reference for the change notices you mentioned and maybe a link to the tekscopes discussion?I found a source for the components, but I can't justify spending $$$ on an eprom programmer that I'll never use again.

author: David Hess
author_rank: Super Contributor
timestamp: October 10, 2014, 01:07:56 pm
content: Quote from: lapoltba on October 10, 2014, 11:12:32 amIf it has separate ROM and RAM boards, then it is the older version. I am including a couple of photos of the early ROM board and the late memory board which replaced it.Another way to tell is that the late version, which has an internal lithium memory backup battery, has a switch on the back to enable the memory backup feature instead of jacks for external power.The serial numbers of the late versions are B100000 and above and they date from 1987.QuoteWith some care, the "mod-pots" can be disassembled for cleaning and will then work as good as new.QuoteThe commonly available free PDF scan of the 7854 service manual does not cover the late version and has three of the change notices at the end. The service manual scan you can order from Artek Media includes the documentation for all of the versions that I am aware of but only change change notices for the late memory board. If you do not need information on the late version then the free PDF scan should be enough.Yahoo has improved their forums so much that I cannot find links to anything on them anymore.The discussion only got far enough to determine that the market was small making such a project questionable economically. At least that was my conclusion.QuoteMaybe you can find someone to program the EPROMs for you.There are adapters made which may be used to convert the 2764 pinout to the 2364 pinout:http://store.go4retro.com/2364-adapter/

author: lapoltba
author_rank: Contributor
timestamp: October 10, 2014, 03:13:22 pm
content: Wow, thank you again. The pictures help. I definitely have the old version, but I don't have nice white stickers. Mine are the foil ones with some hand written dates on them.I never did have any luck with the yahoo groups.I did see that source for the adapter boards. I like that route as I couldn't find the other chip mentioned in the Readme.txt. The readme doesn't mention having to do anything with the address line pullup resistors, i'm assuming they are not needed. I'm looking into finding someone to program them for me. 12 chips total if I want to fix both scopes.On a side note, does anyone have any experience ordering fromhttp://www.futurlec.com? They have both the 2716 16K @ 200ns and the 2764 @ 200ns for a reasonable price.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: October 10, 2014, 03:26:01 pm
content: Thanks for posting this info. Although my 7854 dated 1985 still works in this respect I'm sure the sad day will come.... I printed this out and stuck it with the manual.-Mark-

author: David Hess
author_rank: Super Contributor
timestamp: October 10, 2014, 03:54:04 pm
content: Quote from: lapoltba on October 10, 2014, 03:13:22 pmPeople used foil because it was more reliable either by blocking UV better or not peeling or falling off do to age.QuoteThe pair of chips on the left are 2716 EPROMs which are unlikely to be the problem although they are easy to replace. The four chips to the lower right are the 2364 pinout ROMs which are the ones which normally fail do to age. The single chip to the upper right which looks like an EPROM is actually a Signetics 82S107 field programmable ROM patch. If that one is bad, then you are going to have problems because no replacements are available but it is possible to reprogram the ROMs in such a way that it is not needed.Quote from: MarkPalmer on October 10, 2014, 03:26:01 pmThe 2364 pinout ROMs and maybe the 82S107 field programmable ROM patch are the problem parts. I researched this when I initially was planning on preemptively replacing them or at least the Mostek ROMs in a 7854 but then discovered that the 7854 in question did not match any of the documentation I had because it was a late model which uses the alternative memory card. Up until that time, I did not even know that therewasa late model like that.The same cursed Mostek ROMs are found in other instruments of this era including multimeters, counters, logic analyzers (7D01), and other digital storage oscilloscopes (7D20). The 2764 to 2364 adapter that I linked to was intended for cabinet video games which used these misbegotten ROMs but I gather that some early PCs used them also.