Tektronix 11403 repair, errors G3611 & G3711

[Satbeginner]

Hi all,

I found myself a good looking -but obviously not working- 11304A scope with a 11A52, an 11A72 and a 11T5H plug-in.
The physically good looking mainframe powers up, and seems responding to all the buttons and settings, but..... the power-on diagnostics gave several errors on both the mainframe as well as the plug-ins.

I removed the plugins, and it seems the type of errors from the plugins are strongly related to the errors on the mainframe.
The mainframe errors are in the AD converter, or at least in the read-out of the AD converter.

I found there is communication between the big acquisition board and the data-processing board y means of a series of flat cables.
When placed on it's left side, the bottom flat cable is the one bringing the data from one board to the other one.
On the acquisition board ECL technology is used (dual D-type ECL Flip Flops MC10H131), on the data board these signals are converted into TTL by means of ECL->TTL (MC10125) converters.

When I run the AD Converter Voltage tests (+0,8V, 0,0V and -0,8V) the readout is always 0,034V, this could mean the AD converter is dead, or the communication between the AD board and the data board is wrong. (I hope for the latter...)
When I remove that particular flat cable, the readout is always 0,1024 V, so that suggest the processing of the data is still working?
It is supposed to be a 10bit AD converter, so I think the values will go from -1024 to +1024 ?

I found that some of the ECL outputs have wrong levels, so I removed the faulty FlipFlops, and to be sure, I also removed the corresponding ECL-TTL converter.
I ordered these parts, so now I have to wait until they arrive, I placed sockets on the boards so it will be easier to replace the chips when they arrive.

For now I have some questions:
Are there any schematics for this scope floating around somewhere?
Are there people with some experience on repairing these scopes that I can share experiences with?

Further updates follow when the parts arrive.

Un saludo,

Satbeginner (Leo)

[Johnny10]

I have an 11402A Unit and 2- DSA602.

The 11402 has same issue as yours but I haven't messed with it since it failed.
I believe when I first got the unit I ran it with the covers off and per instructions the ADC overheats and goes bad.
Did that myself!

eBay has a service manual which I would grab if it were me.  https://www.ebay.com/i/300868211640?chn=ps&dispItem=1
The DSA 602 doesn't have a service manual available which makes it difficult to diagnose and repair.
I have repaired the DSA 602 Ram pipeline error.

The plugins are probably fine.
Failures were listed on self test in 11402 unit but when using the 11000 plug-ins in the DSA 602 all were fine and they all passed Enhanced Accuracy also.

Good Luck, Maybe I will pull out the 11402 if you find some success.


Actually after writing this reply I bought an 11402 service manual on ebay.