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Before you drill mounting holes, experiment with orientation in case the field gets into the CRT or other circuitry.

Dave Wise
________________________________
From: [email protected] <[email protected]> on behalf of ChuckA <chuck@...>
Sent: Friday, May 3, 2024 9:30 PM
To: [email protected] <[email protected]>
Subject: Re: [TekScopes] 503 HV Transformer


To finish this thread the problem ended up being leakage from the CRT
filament winding in the LV transformer.
Seems I didn't "hear" Alberts description of the problem until I got an
email from Ferrous Steinka and the light went on.

I removed the CRT leads from the LV transformer and all the voltages
from the HV transformer came on and stayed on.
I connected a spare transformer I had to the CRT leads and now have an
excellent display on the CRT.

I was able to find a NOS 6.3V transformer with 3KV isolation for $5
that should fit on the bottom of the scope cabinet.
And another TEK scope joins the "herd"

Thanks to everyone who shared their ideas on fixing the problem

ChuckA

--
See Early TV at:

www.myvintagetv.com<>

I have a 179 bench DMM also. I usually leave it running because I'm always using it to check this and that.
I also have a 147 Nanovolt Null Detector. After I capacitor-discharge welded all the crimp connections, it works well AFAICT but I don't have the cable and it turns out I'm not enough of a volt-nut to make proper use of it. I'd rather have a 155 or an HP 419 or a Fluke 845.

Dave Wise
________________________________
From: [email protected] <[email protected]> on behalf of jmr via groups.io <jmrhzu@...>
Sent: Saturday, May 4, 2024 6:24 AM
To: [email protected] <[email protected]>
Subject: Re: [TekScopes] Keithley anyone?

I've got a Keithley 2015THD DMM, and I also have a basic Keithley 2000 DMM. I've also got one of the Keithley 2200 programmable power supplies plus another 2200 that needs to be repaired.
I usually operate all of these remotely via GPIB although the 2200 also supports USB.

I have some Keithley too: some 7001 fresh refurbished by me and waiting for
any hand-made board :)
And Keithley 230 (not sure regarding working). I switched it on about a 15
years ago.

Peter

сб, 4 мая 2024?г. в 16:24, jmr via groups.io <jmrhzu=
[email protected]>:

I've got a Keithley 2015THD DMM, and I also have a basic Keithley 2000 DMM. I've also got one of the Keithley 2200 programmable power supplies plus another 2200 that needs to be repaired.
I usually operate all of these remotely via GPIB although the 2200 also supports USB.

Thanks, I saw those but unfortunately I have a 575 which doesn’t have the step gen output banana plugs on it like the 576/577/370. I do have an eico 667 kicking around that I don’t use anymore since finding a tv-7, so Dennis’ solution seemed ideal … wouldn’t have to build any test fixtures either

I have some extra's PCBs that I designed and had made. They are based upon Dennis' (and ChuckA's) design. You can see pictures of the finished unit here: /g/TekScopes/album?id=291888. My multiplier design (like ChuckA's) does not need a tube tester (just a curve tracer). Feel free to email me, if interested.

There is another gentleman on here that sells a step multiplier that uses a switching PS to generate the high voltages.

I have a 179 as my shop DMM. It is the only instrument I own which goes to the cal lab.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA

On Sat, 4 May 2024, Ilya Tsemenko wrote:

It's interesting -- I also have 263 waiting in queue for refurbishment and
calibration as well as several 237 and 238 SMUs and couple of 6517A units :)
Almost done with my HP/Agilent boat anchors, waiting for the last 4 to
return from Keysight calibration, then will take on bunch of Keithleys.
Which are Tektronix now, BTW, so they all probably belong here now.

<+1>

I love Keithley's and repaired quite a bit of them, mostly DC/LF stuff.
Actually have 263 on bench too for some repairs. :)

BR,
Illya

On 05/04/2024 1:33 AM, Shaun M via groups.io wrote:

<Raises hand>
I do. I am working on a 263 at the moment. The best source for discussion I have found is the EEVBlog forum.
Shaun M

---
*
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*

<+1>

I love Keithley's and repaired quite a bit of them, mostly DC/LF stuff.
Actually have 263 on bench too for some repairs. :)

BR,
Illya

Also I am considering trades for in person meets.

I will also ship.

PM me for that.

I have an SC502 that I want to sell. I see an SC503 going for $500 on ebay, but as we all know, ebay really likes to inflate prices.

I don't see many of these SC502s being sold so I'm not sure of a good price to sell it at. I don't want to sell it for too cheap, or have the price too high so some poor fellow spends too much money.

This SC502 works perfectly fine with one issue, the trigger source select switches offset the trace? This only happens to channel 2. Channel 2 is centered when sourcing the trigger from CH2. But when I switch it to CH1, it offsets the trace by about 1.5 divisions. I don't find this much of a problem though as I can just re-position the trace. If you fiddle around with the switch a little bit you can get CH2 to center again, but it's a difficult to hit sweet spot.

I'm sure this is just some bad contacts, but no matter how much deoxit I spray into it, it doesn't help.

Well, that's the only issue! Everything else works fine. Mag registration was calibrated, and the scope seems to be in decent cal. Could use some more work, but I'm selling this anyways and don't want to re calibrate it as I would have to disassemble my TM504 unit.

This unit was modded by me to add a function so that a DC504 frequency counter can measure the frequency being inputed into the scope. This is done by soldering a wire and siphoning off the trigger input signal and connecting it to the DC504 internal input through the TM500 power unit. You will have to desolder the 51 ohm terminating resistor though in the DC504.

The SC502 also had a recent repair:

I fixed it my replacing Q350 and it works perfectly now (apart from the trig source trace offset).

I'm thinking $300?? But I really don't have that much of an idea... I'm a bit of a push over.

I have fallen into the tek scope addiction and now have 7 tektronix oscilloscopes. I need to thin a herd a bit... Then use the new money to buy 3 more tek scopes

If you are picking this unit up locally, you are free to test it all you want before finalizing the purchase. I have an FG501 and PG501 unit you can use to test it.

I am selling only the scope. No TM500 power unit nor any cables.

Located in Carmichael, California, USA.

<Raises hand>

I do. I am working on a 263 at the moment. The best source for discussion I have found is the EEVBlog forum.

Shaun M

To finish this thread the problem ended up being leakage from the CRT filament winding in the LV transformer.
Seems I didn't "hear" Alberts description of the problem until I got an email from Ferrous Steinka and the light went on.

I removed the CRT leads from the LV transformer and all the voltages from the HV transformer came on and stayed on.
I connected a spare transformer I had to the CRT leads and now have an excellent display on the CRT.

I was able to find a NOS 6.3V transformer with 3KV isolation? for $5? that should fit on the bottom of the scope cabinet.
And another TEK scope joins the "herd"

Thanks to everyone who shared their ideas on fixing the problem

ChuckA

--
See Early TV at:

www.myvintagetv.com

Mark,

Check the four zeners on the trigger board. I found mine to be open. I used BZX85B9V1. The low value tantalums were high ESR. They were replaced with film types. Mine did not trigger unless a signal was large enough before I replaced the parts. After the parts were replaced, it triggered as it should. It is possible the connections from the ICs to pads could also be dirty.

Mark

All my TM (usually) works very well. My ongoing projects are vintage Keithley. I have not found a Keithley forum. Do many here delve into the brown boxes?
Jeff

Hi,
Does anyone know if there is a way to get the PCB that Dennis Tillman used to provide for the Tek 575 Vacuum Tube Curve Tracer adapter referenced here - the one where you mod something like an Eico 667 tube tester? Were gerber files were ever shared? He provides the schematic in the document, but I don't have PCB design skills, so it would be nice to get an actual board, which he did a really nice job designing.



He mentioned he could provide it in the document. I had e-mailed him about a year and a half ago and didn't get a reply. I later read about his health issues from other posts in this group. Hope all is well with him.

Thanks!
Phil

I acquired a 7904A a week ago was working very well, but yesterday the B horizontal time base (7B92A) wouldn’t trigger at all, it works perfectly in the A slot. Any suggestion on where to start checking?

Thanks,
Mark - W7HPW

I bought a[nother] 7704A that is dirty but shows promise as it's a later S/N and has Option 9. It had blown fuses and I traced the main 4A fuse to a shorted bridge rectifier. After finding a temporary replacement, the power supply was working on an external load. I then connected it to the scope and, aside from the Z-Axis not working properly (big, bright, uncontrollable blob on the CRT), things appeared to at least be working. After about a minute of run time, one of the tants on the horizontal amplifier board went out in a blaze of glory. Nasty. I now know what you guys were talking about regarding the stink! At least it didn't explode and create even more of a mess.

Fun stuff...

Thanks,
Barry - N4BUQ

Thanks for the reply, Edward. The reference out is exactly -20 dBm at 100 MHz, so that's not it. At this point I doubt I'll pursue it much further, as I am using the ADALM Pluto/SATSAGEN combo to get some capability at 10 GHz. Thanks again for your comments!

Albert:

From my first post:

"But it appears the HV transformer T620 (pn# 120-199) is bad, all the voltages out of it gradually drop after running for a couple of minutes. The +500v supply voltage is solid, I changed the 6DQ6 oscillator and the 6BL8 control tube but no change. "


ChuckA

--
See Early TV at:

www.myvintagetv.com