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jonpaul@...

Hello Jon
Thank you for the reply.
As mentioned, I'm looking for a PS 501 power supply tested (supply and meter)
I'm not sure of value since depends on condition but comparing with similar plug ins, I would estimate between $ 85.00 and 100.00.
Let me know your quotation.

Thank you

Jose

Dave: Thanx for looking. If you ever come across a Vertical Switch circuit
board from a 7104, please contact me. I suspect there are few individual
boards just laying around. The board makes use of a custom Tektronix
thin-film hybrid U668 #155-0173-00 which is not 2nd-sourced.

Gary

--
Gary Robert Bosworth
grbosworth@...
Tel: 310-317-2247

Hi Gary,
I looked the PCB up in the 7104 manual and then checked my stash of boards, and I don't see anything that comes close.? I did have a full set from a 7104 that was taken out out by a forklift (upper left side hit), but I don't see any of the lower section items, so I may have sold the entire lower half at some point.? I do have a few other hulks, but they are "functional", so I don't want to part one out.
Sorry!? I was hoping...
-Dave

Ok now had time to evaluate the scope in more detail.

I note a poor blanking on the LHS at sweep speeds of 100ns/Div or faster; I see exactly the same on my other working 468..... is this to be expected?

The A trigger Slope control does nothing (it's fixed at -ve slope); I note the other 468 has an iffy switch action as well (sometimes works, sometimes doesn't). Is this simply a faulty/dirty switch or are there other known issues with the U240 Slope Select circuit? This scope must have had a frontal impact on control knobs in its lifetime since I've had to replace/repair some bits.

Other than that it seems in good shape; bandwidth is as expected and calibration seems reasonable, also the timebases seem to be working well. Storage works to the expected bandwidth and the DVM works.

Now, I have fitted a GPIB board because I had one from my mule parts but I don't have the 16-way cable to connect it to the A19 board. Neither do I have the switch and LED fitted on the Storage board (it exists on the other 468).

I have no use for GPIB, but for completeness should I bother to fit the GPIB board and cable or is it academic without those bits on the storage board as well?

Dave: I will try to verify the part number when I get home this evening.
As for now, the Tektronix Component Number is A16, and the Tektronix Part
Number is 670-4769-01. I need a fully populated Vertical Channel Switch
circuit board for the 7104 oscilloscope. Thank you for your assistance in
this matter.

Gary

--
Gary Robert Bosworth
grbosworth@...
Tel: 310-317-2247

On Mon, Apr 4, 2022 at 07:23 PM, Mark Vincent wrote:

diyguitarist,

The two gentlemen, Michael L. and Ed B., are absolutely right. Others will
have great advice as the post. I have the 453 and 4/A series I have restored.
I did restuff the main filters, replaced the 1mfd axial decoupling with film
and a couple of tantalums of higher capacitance to give higher filtering, used
Nichicon UHE 220mfd 25V as decoupling for the two 12V supplies and higher
capacitance for the 75V decoupling. I did replace carbons with 1% types and
raised the wattage of some resistors. The triggering was adjusted as well as
other circuits to get it right after resistor and condenser replacement. I did
read that raising the resistors in the high voltage area to 1W should be done.
I did this in mine. I did use 1% types as that is the tolerance I use. One
thing I do suggest is to oil set screws and shafts. Experience taught me this.
What you did to replace the trigger lamp with an LED is fine. I did this in
one of mine with a 4300 ohm resistor to the white LED because the lamp was
burned out. My LED is about 2,5mA operating and is bright enough. I got mine
cleaned up and cleaned the crt because I wanted mine to look as nice as
possible. If you want any further help, we are here. What I said I did is what
I did to mine. You do what you want with yours.

Mark

Since it's a unit from 1969 (serial #37389) I have considered committing re-cappicide. I really don't like the design of the whole can capacitor arrangement. It appears to me that you have to dismantle half the scope in order to replace those. That's not a road that I really want to go down if I can help it.

On Mon, Apr 4, 2022 at 05:05 PM, Ed Breya wrote:

After long storage times, old gear tends to get flaky due to mechanical and
chemical deterioration in the switches, pots, for instance. A lot of problems
can be cleared up by working over all of the controls through their ranges, a
good number of times - you'll be able to tell as you go if things improve, and
whether certain things need more exercise. Do this kind of thing before
opening anything up. Chances are that a lot of issues will clear up. The ones
that remain may be caused by the same things, but internally, so then look at
the internal controls (like pots), connectors, and device sockets.

Ed

Yeah I've went thru all of the controls & switches. None of them have a problem as far as I can tell. I did notice that if I put the Horizontal Display switch between DELAYED SWEEP (B) and EXT HORIZ that I get a dot without the line, but there is no horizontal deflection and it won't display a waveform. I've been trying to figure out what that may indicate but I'm still stumped.

On Mon, Apr 4, 2022 at 01:25 PM, Michael W. Lynch wrote:

Have you checked the LVPS power rails for excess ripple? You can have "good"
voltages and still have excess ripple. This will drive the circuitry to do
some crazy things.

--
Michael Lynch
Dardanelle, AR

Yeah, I have 10mV on the +12V & -12V supplies. I still need to check the 75V supply one more time, but as I recall it was nothing significant.

I am looking for part number 354-0269-00 "Ornamental Ring" as it is called in the Tektronix operator/parts manual. it is the filter frame that measures approximately 3.5"x2.5" with a diagonal measurement of 4.25". These are approximate measurements and I post them in case there are other like type frames from other Tektronix instruments. I am trying to restore this oscilloscope towards it original configuration. I would appreciate any information that leads me to obtaining one of these frames. Thank you.

Mea Culpa!

I'd forgotten, or never read the handbook; the time cursors are not line cursors, like the voltage cursors, but dots on the trace!!! They are there and everything is working.... I think! (I probably had 2465s on the brain.... two of those I fixed in recent weeks).

Well that's two out of three 468s working; shall I try to get the third one working????

Perhaps I'll leave that for a while; my wife keeps making comments like "oh, who are you and what are you doing in my house" when I escape from my radio room!

I might have one; do you know the p/n off hand?
-Dave

Hi folks,
For 7854 owners who have been suffering from the ROM Rot problem with their EPROMS - I've developed a drop-in replacement for the MCM68766 EPROM that you may find interesting. A short video appears here. If it's of interest to a sizeable number of people I can make it available on ePray. The board can be programmed on any MCM68766 programmer and replaces the original with no other mods required.

Best - Ram

diyguitarist,

The two gentlemen, Michael L. and Ed B., are absolutely right. Others will have great advice as the post. I have the 453 and 4/A series I have restored. I did restuff the main filters, replaced the 1mfd axial decoupling with film and a couple of tantalums of higher capacitance to give higher filtering, used Nichicon UHE 220mfd 25V as decoupling for the two 12V supplies and higher capacitance for the 75V decoupling. I did replace carbons with 1% types and raised the wattage of some resistors. The triggering was adjusted as well as other circuits to get it right after resistor and condenser replacement. I did read that raising the resistors in the high voltage area to 1W should be done. I did this in mine. I did use 1% types as that is the tolerance I use. One thing I do suggest is to oil set screws and shafts. Experience taught me this. What you did to replace the trigger lamp with an LED is fine. I did this in one of mine with a 4300 ohm resistor to the white LED because the lamp was burned out. My LED is about 2,5mA operating and is bright enough. I got mine cleaned up and cleaned the crt because I wanted mine to look as nice as possible. If you want any further help, we are here. What I said I did is what I did to mine. You do what you want with yours.

Mark

Unfortunately, that's just the user manual (I was the one who added most of the recent info on that page. So, so far, I haven't been able to find any apps at all.
I tried running an undelete on the HDD option I acquired too, but the data was too far gone to extract anything, so that was a dead-end too.

After long storage times, old gear tends to get flaky due to mechanical and chemical deterioration in the switches, pots, for instance. A lot of problems can be cleared up by working over all of the controls through their ranges, a good number of times - you'll be able to tell as you go if things improve, and whether certain things need more exercise. Do this kind of thing before opening anything up. Chances are that a lot of issues will clear up. The ones that remain may be caused by the same things, but internally, so then look at the internal controls (like pots), connectors, and device sockets.

Ed

Have you checked the LVPS power rails for excess ripple? You can have "good" voltages and still have excess ripple. This will drive the circuitry to do some crazy things.

--
Michael Lynch
Dardanelle, AR

I have a Tek 453 that was given to me like 18 years ago. I used it to look at waveforms of guitar pedals I made and that sort of thing. It had sat unused for probably 10 years until I decided to recently start using it again. The "A Sweep Trig'd" indicator lamp was burned out and I replaced it with an LED instead. Was a very simple mod and it's been working great. The scope has been working OK for the most part, but it has a few problems that I have not been able to figure out. I'm hoping that someone here might know what might be the cause of these issues.

First one is the trace is unstable for about 4-5 minutes when turned on after not being on for a while. Hard to explain but it's kind of jumping around/vigorously spasming but staying in generally the same place (it's not jumping around all over the screen). With auto trigger on and no input, If I push the trace finder button, the bottom of the image is kinda going crazy. This goes away after it warms up for a few minutes and is quite stable. As far as I can tell the power supply is OK unless it's one of those big can caps under the B Sweep PCB. Is there another place in the circuitry that could cause that? When I first got the scope it was very stable when I turned it on.

Second one is that the right end of the sweep is a little unstable. In other words, the left end of the waveform is very stable but the right end is constantly shifting around a little, the end of the waveform is not stable and staying in one place. Doesn't matter if I'm using A or B Sweep modes.

Third one which is the most perplexing is that I have noise on the waveform that is like a cyclical fishbone pattern. This doesn't really show up until you use the Mag feature on the Horizontal Display switch and when in EXT HORIZ mode. That is where it is very annoying because you have this nice Lissajous waveform with a fuzzy halo behind it. With no input I get a dot with a line extending left and right from the dot about 1/8" each direction. I've been thru the entire Low Voltage Power Supply, Horizontal Amplifier, Vertical Amplifier, Vertical Switching, Tigger Pickoff, Trigger Preamp, B Trigger Generator, B Sweep Generator, A Trigger Generator and Z Axis Amplifier. I found a few transistors that were out of spec and replaced them with good ones off PCBs from a donor scope. I also checked the CRT Grid Bias, etc. Nothing I have done has rectified this. It sure does seem like noise coming from somewhere but I have no idea from where. Could it be the CRT itself? It seems to be working very well... it will get intensely bright, I can get a very sharp image, etc. This problem only shows up when in EXT HOR or MAG modes. What the heck could be causing this? Switching noise from a dodgy tunnel diode? Or a noisy transistor in the CRT HV Oscillator? I didn't find any voltages that were off in that circuit either.

Hey Jared,

The jitter analysis application looks to be linked on the TDS784 TekWiki
page: . I haven't tried it yet, I'd be
curious to know whether it works for you. I've never found any of the other
applications, but I'd be curious to see those also :).

Siggi

On Mon, Apr 4, 2022 at 12:36 PM Jared Cabot via groups.io <jaredcabot=
[email protected]> wrote:

Hi all,

I just got the HDD option installed and working in my TDS784C and am now
looking for any of the applications that were available.

Does anyone have any of the apps that they can send through to me?

TDSPWR1 - Power Analysis
TDSJIT1V2 - Jitter Analysis Measurements
TDSCEM1 - Communications Eye-Diagram Measurements
TDSCPM1 - Communications Pulse Measurements
TDSDMM1 - Disk Drive Measurement
TDSPRT1 - Enhanced Printing


Thanks!
Jared

Hi all,

I just got the HDD option installed and working in my TDS784C and am now looking for any of the applications that were available.

Does anyone have any of the apps that they can send through to me?

TDSPWR1 - Power Analysis
TDSJIT1V2 - Jitter Analysis Measurements
TDSCEM1 - Communications Eye-Diagram Measurements
TDSCPM1 - Communications Pulse Measurements
TDSDMM1 - Disk Drive Measurement
TDSPRT1 - Enhanced Printing


Thanks!
Jared