Tektronix 475A and DM44 Repair Power Supply and Logic

A huge thank you again for all that continue to Join us in the lab for repairs and alignments. The channel would not exist with out all of you so thank you again for dropping by.
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A viewer of the channel has provided some 475’s and 475A’s for some trouble shooting videos. This is the first video in repairing the 475A as well as the DM44 and with that down the rabbit hole we go:
** Repair exposes the Tech to mains electric and should only be done by trained personal. Errors can be fatal. **

[@ReyciclismoMTB]

Just like the two I have, mine are in working order. But I need( should) replace all the old stuff. Great video again. I hope you do one, on a 2246, I have a issue with mine.

[@ZenwizardStudios]

I do have plans to record some of the 2000 series I do need some examples to put in front of the lens.

[@ReyciclismoMTB]

@@ZenwizardStudios Interesting, funny enough the DM wont turn on just now hahah

[@ionbunoara4042]

Hi, I need help with a 465B oscilloscope. After 30 secs from power on the orizontal line goes outside from screen to the right and came back as a spot. All screen settings (luminosity, focus etc) are not working in this case. In the first 30 secs the orizontal line can be set, in shows the waveform. I have this from 2 days from a friend as a gift, I am a teacher and I need it for school. thank you.

[@ZenwizardStudios]

Sounds like a thermal issue in the power supply. I would watch the power rails. All of them if you can and see if one is falling out of spec or regulation. I suspect a faulted Tant Cap and or a cracked solder joint. The 30 sec time frames points to something with higher current as this would heat up the fastest. Take extreme care in the power supply there is quite a bit of elevated voltages in there.

[@LegalizeAdulthood]

So if you have a suspect TI socket, what is your preferred replacement part?

[@ZenwizardStudios]

The issues I have with these TI sockets is only with this era of socket design. I am more than happy to use a modern TI socket to replace these older series sockets with another brand would be Amphenol really any good quality socket of the correct pin count. This series of TI socket used a side contact for holding the IC pin and is known to be problematic. This was done at the time due to patent issue from another manufacturer. So modern there are no issue it is specific to this age of design.

[@fabiotrevisan8922]

While acknowledging that I it isn't on me to answer, I`d say, skip the sockets altogether. It's just a main source of headaches. Manufacturers back then would use sockets NOT JUST for easiness of repair, but also because ICs were an expensive part of the BOM and by using sockets they could pre-build the boards and having them populated with ICs only when they had an actual order, shortening the lead time for manufacturing without paying the high cost of having completely built boards collecting dust in the stock. Past 40~50 years, and this part of the equation is not relevant anymore. All the old equipment I eventually have to restore nowadays, I will remove the ICs and transistor sockets unless: a. it's a custom part, b. it's a programmable part, or c. it's a part in a circuit that is very hi frequenciy or very high impedance where taking out the socket would change the design parameters. Digital ICs (Logic gates, uPs, etc.), I would solder them directly to the board without thinking twice.

[@ZenwizardStudios]

I have a video in the works that will go in to this a little deeper I hope it will clear some things up.

[@LegalizeAdulthood]

@@ZenwizardStudios That was a great video! I have a lot of vintage computer gear (e.g. older than 80s micros, actual vintage stuff), so I'm likely to run into these problematic sockets at some point. Now that you've done the followup video it'll be easy to recognize these older sockets.

[@srtamplification]

That delay time knob would be useless for measurement purposes. That is what makes the original vernier so great.

[@ZenwizardStudios]

I have since found out that the delay time position integrates with the DM44 so this is actually the factory configuration.

[@srtamplification]

@@ZenwizardStudios Interesting. I always thought that the DM was just an add on to a scope. I didn't realize they came like that, but now that you mention it, I have never seen one with a DM and a vernier delay adjustment. Thanks!!!

[@ZenwizardStudios]

I am with you on this one I like the normal delay time knob. This will crop up again when I do the Horz alignment.

[@fabiotrevisan8922]

Besides being a piggy backed autonomous DMM, the DM44 has a functionality that allows for differential time-base measurements (period AND frequency). With that functionality, it renders the dly'd time base vernier knob completely unnecessary.

[@srtamplification]

@@fabiotrevisan8922 So my question is this: Can you put a DM44 on a Tek O-scope as an add-on and still have the manual capability to use the vernier, even though you wouldn't have to? I mean I still count reticules to measure voltage and time on a digital scope that gives you those values. Just old school I guess.

[@singleshot1331]

Have a 475A working when I turned it off top meter works lights on front come on but trace not coming on and the fan. Going to ask a friend if he wants it if not you're welcome to it if you want to pay shipping from Winston-Salem North Carolina I can send you pictures. No you need to just let it go to waste. Has extra glass plates probes two books and the update book. Hit me back if you interested has the heater probe also

[@ZenwizardStudios]

I could be interested the trace not showing is a bit worrying as the 47x scopes are known to have HV issues worst case scenario the HV multiplier might be toast.