Test Equipment Anonymous

I bought this 500MHz 7B92 Time Base plug-in off Ebay several years ago and was advertised as working. It doesn't. In fact, it was completely dead. No trigger, no sweep, no trace on the CRT. I contacted the seller and he refunded me full purchase price and told me to keep the plug-in. I did some troubleshooting with an ohm meter and found a shorted tant. Replaced the tant but still no joy. So I put it aside to work on another time.





Fast forward to today. In order to troubleshoot this plug-in I needed a Tek P/N 067-0589-00 plug-in extender. Go check Ebay prices to see why I didn't buy one. But Pat (Cubdriver) has one and he has graciously let me borrow it. I received it today and once I'm done with it I'll return it.



I'm going to use a 7603 mainframe rather than a 7904 mainframe to troubleshoot the plug-in because it's 3 bay rather than 4 and easier to move around on the bench. Next installment will have it fitted and ready to work.

In order to troubleshoot this plug-in in a 7603 I had to change a jumper as per the manual.



Overall view with fixture and plug-in installed. I pulled the cover off the 7603 to make sure fixture was properly seated. Even with this extender working on that crowded plug-in is going to be a challenge.



There's a clip on the extender to hold the plug-in in place. Pull up to release.



Let the fun begin.

MED6753 wrote: ↑Wed Nov 27, 2024 6:56 pm Overall view with fixture and plug-in installed. I pulled the cover off the 7603 to make sure fixture was properly seated. Even with this extender working on that crowded plug-in is going to be a challenge.

Wow, yes, I can see why working on that is going to be a challenge.

The end-to-end length of the scope plus the plugin seated on the extender card is impressive.

I don't think I can see any way to set that up other than width-wise which means working on anything on the far side of the plugin while it's seated in the extender is going to be difficult, particularly taking measurements from anything on that side while it's running and live.

Arrange some support blocks and stand it on its rear end with the plug in standing upright? If you had a lazy Susan that would let you access both sides easily. The challenge would be preventing Harley from knocking it over...

-Pat

25 CPS wrote: ↑Mon Dec 02, 2024 1:41 am I don't think I can see any way to set that up other than width-wise which means working on anything on the far side of the plugin while it's seated in the extender is going to be difficult, particularly taking measurements from anything on that side while it's running and live.

Not forgetting turning it around - and then finding you need to probe something on the other side.

That's your own personal version of Murphy's access cover, as per AN47 Appendix J, p131, IV.30 and IV.31 You do have a copy of that PDF on your machine, don't you.
Bonus points if you have more than one paper copy.
Hide your head in shame if you need to gurgle it

Thank you for giving me another reason to avoid Tek 7000s; never liked them, even in the 70s

Cubdriver wrote: ↑Mon Dec 02, 2024 2:58 am Arrange some support blocks and stand it on its rear end with the plug in standing upright? If you had a lazy Susan that would let you access both sides easily. The challenge would be preventing Harley from knocking it over...

-Pat

Have pieces of wood or foam plastic to support the back and prevent it from being damaged from contact with the support, then have further blocks to form a well into which the scope was put to prevent toppling. Then you've got the plug in and extender presenting a lot of leverage with risk of damage, and I'd guess the extender was intended to be used horizontally. Then somehow you'd need to bring the plug in to a convenient height to work on. It's a fair amount of building stuff.

A sufficiently large, strong table would be a better bet, depending on the space available, which may be limited. How about a table, or other support, to extend the bench out, so the mainframe and most of the weight, was on the bench and the plugin was properly supported with access to both sides? It would depend on the materials and space available.

I've never been drawn to Tek 7000s either.

Everything mentioned about the challenges involved troubleshooting this plug-in duly noted. Without a doubt it's going to be a pain in the arse. I haven't had a chance to start since this past weekend was Thanksgiving USA here with all the craziness associated with that. Hopefully later this week I'll get some time. See attached flow. This unit is dead right at the start. No matter what trigger mode is selected there's no trigger light. B trigger dead too. So that's where I'm going to start. The best I can hope for is perhaps a voltage is missing.

Finally got some time to troubleshoot this plug-in.

The defect with this plug-in was staring me right in the face. The Main Triggering Mode/Coupling/Source switches are supposed to light up. DS1 and DS3 on attached schematic. Verified that there's no +5V to the lamps. So in the process of tracking it down.



I had to pull a board to get access to the power distribution.



So far I haven't found the issue but I'm hot on it's trail. See attached schematic. There's a drafting error on it. Can you spot it?

MED6753 wrote: ↑Mon Dec 16, 2024 8:01 pm Finally got some time to troubleshoot this plug-in.

The defect with this plug-in was staring me right in the face. The Main Triggering Mode/Coupling/Source switches are supposed to light up. DS1 and DS3 on attached schematic. Verified that there's no +5V to the lamps. So in the process of tracking it down.



I had to pull a board to get access to the power distribution.



So far I haven't found the issue but I'm hot on it's trail. See attached schematic. There's a drafting error on it. Can you spot it?

How can DS, FH and BB be connected to +15v when the other end is connected to +5v?

It's +15V coming in from the mainframe at pin 18. The +5V is the error. It should read +15V.

MED6753 wrote: ↑Mon Dec 16, 2024 11:03 pm It's +15V coming in from the mainframe at pin 18. The +5V is the error. It should read +15V.

Thats what I was saying, but kind of badly

You ever bark up the wrong tree? Well yesterday I was a barking fool. The +5V that turns on the Trigger switch lamps originates from the mainframe, not internal to the plug-in. The 7603 scope that I'm using to troubleshoot the plug-in has no provision to light those lamps. Therefore, it's not a defect and I'm back to square zero. Oh well.