Test Equipment Anonymous

MED6753

The King watching over his domain.

MED6753

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 defe...

MED6753

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

MED6753

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 i...

MED6753

Where would that watt hour meter have been designed / used for then at just 25Hz, I always thought the standard was for either 50 or 60Hz? Niagara Falls? https://en.wikipedia.org/wiki/Utility_frequency#25_Hz_origins Many US electrified railroads are 25Hz to this day. Old New Haven and Pennsy are ex...

MED6753

Ain't that the truth. Harley has already broken several. :shock: Arh, yes, but he's still a young kitten at heart, give him a couple of years and that will be a thing of the past. Exactly! Once he's got some experience, he'll start knocking the whole tree down. :twisted: :twisted: :twisted: (I keed...

MED6753

Specmaster wrote: ↑Wed Dec 04, 2024 9:50 pm Seasonal cat picture.

cat and tree.jpg

Ain't that the truth. Harley has already broken several.

MED6753

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'...

MED6753

In order to troubleshoot this plug-in in a 7603 I had to change a jumper as per the manual. https://imagizer.imageshack.com/v2/xq70/922/0TOo46.jpg 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 workin...

MED6753

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 trou...

MED6753

I have no clue if it's worth anything or not. Does Ebay give any insight?

MED6753

AVGresponding wrote: ↑Sat Nov 23, 2024 3:15 pm Got this in a job lot this week, wonder if Mike can tell me if it's worth trying to flip it:

44e02f5b-c7dd-4917-a31f-abe6d5b1e0d3.jpg

IMG_20241123_112103390.jpg

What is it?

MED6753

Your acquisition persuaded me to get out it's bigger brother 454 and give it a quick checkout. There's many common parts between the 453/454 and I have a parts unit if you need something unique and unobtanium. If I recall the only parts missing from it are the vertical output transistors which Sean ...

MED6753

My very first job at IBM in 1973 was a high powered switch card tester which had a 453 integrated into the tester to verify proper waveform and frequency.

MED6753

bd139 wrote: ↑Thu Oct 31, 2024 10:16 am What's this? You bought another Tek scope. Oh now I'm never going to live this down. I'll create a thread for it

Naked photo. It does have clothes don't worry.

No fancy ICs abused in this. It is of course broken which I will document elsewhere.

IMG_2325.jpeg

It's either a 453 or 454.

MED6753

OK, let's get this DM501 calibrated and completed. First up. As noted prior the Ohms was flaky. Due to a dirty range switch. Deoxit fixed that. And it did require a minor adjustment of the ohms calibration pot. Now in spec in all ranges but I still don't like that it doesn't have a 200 ohm range. Th...

MED6753

Those blue Philips 'lytics have to go. Always a problem. Some more in the suppy section on the back. Recent "defpom" video seems to suggest the back PS section might have a looming problem with brittle plastic leading to overheating regulators, at least check the TO-220's on the metal she...

MED6753

OK gang, I opened up the assembly and I found the problem. And my hunch was totally correct. ... This gooey crap was between the 9MEG resistor and the others below it. ... I cut one lead of the 9MEG to isolate it and surprise, surprise....measures 9MEG. That gooey crap plus a foam pad on the cover ...

MED6753

Specmaster wrote: ↑Sat Oct 12, 2024 10:44 pm
Well sleuthed, Watson

Elementary my dear Sherlock.

MED6753

Bloody tants. :roll: They all measured good but we all know that can change at the next power up. https://imagizer.imageshack.com/v2/xq70/922/EqyGqA.jpg It's FIXED!!!! :lol: The contaminated network was the source of the inaccurate DCV. I'll bet almost all the DM501's on Ebay sold as not working suf...

MED6753

nixiefreqq wrote: ↑Sat Oct 12, 2024 11:33 am did you by any chance stick your probes directly in the gooey crap just to see how conductive it is?

No I didn't because the stuff was falling apart and stuck to everything it came into contact.

MED6753

OK gang, I opened up the assembly and I found the problem. And my hunch was totally correct. As proof, the unit on the bench and measuring the 9MEG resistor. NFG. https://imagizer.imageshack.com/v2/xq70/923/zsm4Gm.jpg I opened it up with a dremel. That large resistor clearly says 9MEG/0.1%. https://...

MED6753

bd139 wrote: ↑Fri Oct 11, 2024 1:11 pm Something suspect going on there.

I would pull the divider network and test it externally before going anywhere near replacing it or opening it lest one ends up with two problems to solve

Go back and read. I did pull it before testing.

MED6753

The mystery of what's inside that part will be resolved once I cut it open with a dremel. The replacement parts should arrive tomorrow (Friday).

MED6753

Look at all those crapacitors.

Let me "fix" it for you.

Test Equipment Anonymous

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Re: Tek 7B92 Plug-in Repair

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