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TM504A differences from TM504
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I'm finally getting around to fixing, updating and working on my 500 plug in collection.
I have a, apparently, rare TM504A chassis that was modified by a previous owner so not all modules work in all slots and sources do not talk to destinations. It also has an oscillation in the power supply that I need to fix (Classic issue with how they did the feedback on the power supply). It is finally time for me to understand the back programing header and how to use it so that say my freq counter can read the oscillator or the volt meter read the power supply though the back plane while still being able to swap out modules. I have been unable to find a manual or schematic for this unit, but there are plenty for the TM504. Is there any real difference other than the addition of a fan and switch location? Is the TM504 service manual good enough or if not where can I hunt down a TM504A one? I sure wish there was a modern version of the 500 modules. I have some great modules with no current product options. I use the filter/pre-amp all the time at work and once I updated the op amps it works better than the current version by another vendor. But these things sure are getting old and I wonder if it is worth my time to keep them working for bench work any longer. For now I'll keep trying. Thanx, Hawker |
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On Thu, 26 Apr 2018 07:22:05 -0700, you wrote:
I'm finally getting around to fixing, updating and working on my 500 plug in collection.Mine is a TM504. There's a backplane programming book, and you will need the manual for each plugin to see what the exported signals are. No idea. You could update them by re-designing some of the modules and adding microprocessors. It would be an undertaking, though, so I'd recommend the TM5000 series if that's a way you want to go. You'll find that the TM500 modules are decent enough, but as you note, the technology is old. You can upgrade some of it, but short of redesigning the entire module, I suspecte your options are limited. in terms of keeping them working, I'd ask what other similar equipment you have, and if it's that much better. I have a mixture of standalone and TM500 modules, each of which has its use. Harvey
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Stanford Research Systems offers a system similar to the Tektronix TM-500/5000 systems. I've not done an exhaustive comparison between what plug-ins SRS offers and what Tektronix offered; I suspect that SRS does not offer as many plug-ins as Tektronix did. But the SRS system is current and modern. The pieces are also expensive.
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DaveD On 4/26/2018 9:58 AM, Harvey White wrote:
On Thu, 26 Apr 2018 07:22:05 -0700, you wrote:I'm finally getting around to fixing, updating and working on my 500 plug in collection.Mine is a TM504. There's a backplane programming book, and you will |
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Did you find info on TM504A? It could not have been produced for very long. In my "newest" 1983 Tek catalog, Tek are offering the TM500 (not A) and they had then brought out the TM5003 and TM5006.
The user customization of the frames was an asset for flexibility but can cause damage with surplus TM500 equipment. People don't check for customization including movable tabs in the card edge connector to block module ingress. Any "new to you" TM500/5000 needs to be checked for a few things. Past users may have made mods so that the frame is not "plug and play" and this can cause you to inadvertently damage module or frame. Worthwhile as you said, to understand the customization possibilities and options. I am still a big TM500/5000 fan. There wasn't anything like it back then. Working units have uses today. Basic physics measurements are accurately and inexpensively made with TM500/5000 if you don't need computer interface. Easy to repair. Lots of info and parts. Not sure what would be today's "equivalent" system with the breadth of modules and cases. It was a very flexible system although bulky by today's standard and no computer interface unless you had certain newer modules and frames with GPIB. George |
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Hi Hawker,
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The TM504A is apparently quite rare. It doesn't show up in any of the catalogs. In the 1993 catalog the TM504 is listed along with several other mainframes but by 1994 the only TMxxx plugins are the TM5003, TM5006A, TM502A, TM503B, and TM506A. There is nothing active in any of the TM500 mainframes so I am puzzled by your comment about an oscillation and feedback in the power supply. This sounds like it has a switching power supply which would make it VERY DIFFERENT from a TM504 and more like the TM5003 or TM5006. Dennis Tillman W7PF -----Original Message----- -- Dennis Tillman W7PF TekScopes Moderator |
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Thanx folks.
Nope - never found any documentation on the TM504A but I do see them out on Ebay - it looks more modern then the other main frames in the series. Apparently is is quite rare indeed but also maybe newer than most main frames in the series? I guess I have some learning and re-thinking to do. I got a 4 space rack as it is a good size for my bench (about as wide as everything else) but have more than 4 modules. I figured I would just swap them out per whatever function I was doing. It seems that may not work if I want the rack to be set up for them to talk to each other. I thought maybe I could set 2 up to be sources, 1 to be destinations and 1 for high power (power supply?) Maybe I just need to pull all mods and forget about the idea of internal coupling. I thought maybe things like the freq counter could read the function generator or volt meter read the power supply but perhaps that isn't realistic? Time to better read the manuals and info on modding. Is there a general reference I should refer to or just the manual for each module I am using? As to the oscillation issue. Due to the external pass transistors in the feedback loop of the power supply. If you redraw that circuit you notice that the load cap is a negative feedback cap and the feedback "resistor" is the pass transistor. As frequency goes up gain goes up. It was a common way to do power supplies back in the 70s but is problematic for newer parts. It This wasn't an issue back then because capacitors had high ESR, gave out at higher frequencies and op amps had poor bandwidth. Fix any of those issues (say with a low esr modern capacitor or different op amp), or increase resistance in the feedback loop (due to corrosion or a loose connection) and that supply format is known to oscillate. I suspect I just need to clean some contacts as I did not replace any caps yet. There are a few known fixes for this issue with a small RC inserted in the feedback loop to stabilize them. I run into this a lot when servicing old synthesizers that used the same power supply topology. So some main frames have switchers in them? TM5003 and TM5006? Any others? Are the switchers clean enough or should they be avoided? |
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Chuck Harris
TM503 and TM504 have their power switches as pull tabs on
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the side of the front panel. TM503A has its power switch as a rocker switch on the rear panel. I would expect that the TM504A would simply be a rear switched TM504. It seems to me, but I am too lazy to check, that there is an additional difference relative to suitcase handles on one side, and feet on the other, and perhaps a difference in the power cord, fixed vs. IEC style. -Chuck Harris Hawker wrote: Thanx folks. |
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That would explain the barriers he found too, setup specifically for the SG505 & AA501A.
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Bob. On 5/1/2018 2:42 AM, Egge Siert wrote:
Hi to All, |
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Thank you very much.
This gets me much closer. And yes there is a sticker inside referring to the SG505 and AA501a. I just assumed that the previous owner had those modules in it. Some google implies I need a manual 070-7813-01.pdf or f7523a1 but could only find teaser TOC for sale and dead links. Hopefully I can use this for general use at some point. The Tek Wiki link doesn't work. |
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Thank you,
That was really helpful in many ways. Alas it didn't explain the TM504A modes. FWIW I did get my TM504A working. I had to remove the slot to slot mods and the oscillation was fixed after I put some deoxit on the connectors to the transistors. They probably would have been better if I soldered the wires to bypass the connector. The inside was very clean and nicely laid out. No lock tite on screws so almost every screw was loose and the aluminum was welded together rather than screwed which makes it almost impossible to get the PCB out if I wanted to do heavy mods. It was much more modern looking than the TM504 inside. SMOBC circuit board and not Tin plated copper even! Either this module was newer than I thought or they were a very early adopter of SMOBC. Rare to see SMOBC before about 1992-1995 or so. I wish Tek had standardized on a "main out" and "Main In" pin so I could wire two slots together but which pin is main out and which is main in seems to change from 500 module to 500 module. Even worse is sometime the ground is the pin above, sometimes below and sometimes across with no consistency. Rules out the idea of being able to have an "input module slot" and "output module slot" that read each other if I want to change modules. I should be able to put a function generator in one slot and a volt meter or frequency counter in the next slot and have either of them read the function generator but alas they have different pin outs so this is not possible. What was Tek thinking? |
GeorgeP
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