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Re: Tektronix 547 Lack of Sweep or Intensity Control
You took it to another level. I did mine as a simple layer wind with retrace. No impregnation but it has held up for years.
Dave Wise ________________________________ From: [email protected] <[email protected]> on behalf of TV7 via groups.io <sipcommaustralia@...> Sent: Sunday, April 20, 2025 3:44 PM To: [email protected] <[email protected]> Subject: Re: [TekScopes] Tektronix 547 Lack of Sweep or Intensity Control Hi Dave, I built a winding machine that was inspired by the old morris winders that have a cam to form a basket wind except mine was much finer tolerance than the old morris winders because of the 0.1mm wire used. These I potted in beeswax in a vacuum chamber before installing in the core again. They work perfectly and never had a failiure yet. I did have some videos on you tube but some people got irate when I refused to rewind their transformer, so removed the lot. |
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Re: How to clean the finger contacts on an SG503
graphic papers (for printing) will contain clay as it's made and in coating
after it is made, it most likely will have calcium carbonate to combat acid degradation over time of the wood fibers and for brightness, titanium dioxide is also used for opacity and brightness. All 3 of these "pigments" are abrasive clay the least, Ti02 the most. There are all kinds of graphic papers that may or may not contain these pigments, may or may not be precoated, top coated, and calanderd. I would not use any paper to make strips for cleaning leaf contacts once wet is likely to "shed" all kinds of stuff. Plain uncolored card stock is ideal with no pigments, heavy and stiff and not wilt when soaked with IPA, I use those tags with a string attached for IDing stuff, easy to cut thin strips, soak with IPA, slide under open leaf and then close to "lock" the strip as I pull it out to scrub the contact surface, firm but gentil On Sun, Apr 20, 2025 at 1:47?PM Roy Thistle via groups.io <roy.thistle= [email protected]> wrote: On Sat, Apr 19, 2025 at 11:10 AM, Dave Daniel wrote:Generally, paper vendors ... like for copiers, or laser printers... won't |
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Re: Tektronix 547 Lack of Sweep or Intensity Control
Hi Dave, I built a winding machine that was inspired by the old morris winders that have a cam to form a basket wind except mine was much finer tolerance than the old morris winders because of the 0.1mm wire used. These I potted in beeswax in a vacuum chamber before installing in the core again. They work perfectly and never had a failiure yet. I did have some videos on you tube but some people got irate when I refused to rewind their transformer, so removed the lot.
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TM5006 Power Supply broken¡
Hi Group Members!
Got a broken TM5006 Mainframe and found a few damaged parts showing a short on my Multimeter. Here the original part #, and now I¡¯m looking for x-Types for those parts. I¡¯d be nice if someone could give me a hint or confirm about the parts I found are fitting! 151-0632-00 some people use MJE13007, or some the MJE13009? 152-0655-00 A115AX39 ??? Can not find this type of rectifiers at all¡ 152-0400-00 1N4936 152-0686-00 MR821 Any help welcome! Best, Joe |
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Re: Tektronix 547 Lack of Sweep or Intensity Control
I've been following this thread with some interest. One thing that might be responsible for the uncontrollable high intensity is leakage to chassis in the HV divide that starts with the HV adjust pot R840and then R841 to R847. It also includes C841 and C852. I have had leakage there upset the HV regulation. Check the focus pot (carefully!!) . Also it's worth measuring the screen voltage on pin 8 of V800 which should be around +90 volts.
Morris |
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Re: Tektronix 547 Lack of Sweep or Intensity Control
Deon, I¡¯m interested in your T801 recipe. How did you rewind it? I¡¯d like to compare to my 453 rewind which I published here.
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Dave Wise On Apr 20, 2025, at 8:30 AM, Gordon Wood via groups.io <gordonwood70@...> wrote: |
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Re: How to clean the finger contacts on an SG503
On Sat, Apr 19, 2025 at 11:10 AM, Dave Daniel wrote:
Generally, paper vendors ... like for copiers, or laser printers... won't tell you what is in their paper, or what is on the surface of their paper. At least, they won't tell me. AFAIK... and at least... a lot of paper... has 'clay' as a binder... and, 'ink jet printer paper' may be 'coated' with some kinds of 'clay' Of course this 'clay' ... whether used as a binder, in the paper... or as an ink 'stabilizer' ... when coated on the surface of the paper... is a highly refined material. Yet... just by the vary nature of the minerals that clay is composed of... there is an abrasive content. Does that content, significantly abraid the gold on contacts. Who knows? -- Roy Thistle |
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Re: Tektronix 2247A problem. Keep or return?
With too much ripple, I can see the reset circuit tripping especially if the power drops below the reset threshold.? I think there's likely a "needs to be good for this amount of time" function involved.
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In the 468 scope, the extra ground lead was used as a jumper.? I think you can never be quite sure. Harvey On 4/20/2025 10:32 AM, Jay Czaja via groups.io wrote:
I think I see what's going on with the scope. On the 'measurement processor' circuitry (A16 processor PCB) , there's a power-on reset circuit that monitors the 5V rail and sends a reset to a few of the microprocessors if the voltage isn't up to snuff. I see the SYS_RESET being held low when the problem occurs and doesnt recover until the unit has been turned off for a while. There's an appreciable amount of ripple on the 5V supply which I think might be causing this. I have a good feeling that a re-cap is going to make things better. |
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Re: 453 scope, MOD 703K and MOD 703H
Ray,
Check the tunnel diode circuit to see if it is working right. There are internal adjustments that may need to be adjusted. This circuit is sensitive to get adjusted. In mine, I replaced a number of resistors in the piece to 1% because that is what I have have in stock and they are very low drift. R497 should be 1/2W. Resistors R473 and R674 should be 1W and R544, R412 and R483 should be 2W. The originals are 1/4 and 1/2W carbons. Likely they are out of tolerance. They were in mine and bodies were dark. Some other resistors in the scope should also be increased in wattage. Check C485 to check its condition. V443 could be weak/leaky. Check the other Nuvistors as well. R343 and R353 are problematic. If vertical is not right for known signal and v/div, these resistors are high in value. Mine were several times the value. Using a 510 and 560 ohm 1W 1% in parallel will give the correct resistance. Mark |
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Re: Tektronix 2247A problem. Keep or return?
Getting the PSU out of a 2247A was a dream compared to removing the front panel PCB from a 2232! I had to replace the 'Trigger A' potentiometer on my 2232 because the shaft had cracked. Getting the front panel out took quite a bit of effort. The only part that was tough on my 2247A was that the screws attaching the fan to the chassis must have been longer than what they typically used. They were long enough that it was impossible to remove the PSU without loosening the bottom fan screws. Thankful I found an L shaped T10 wrench laying around that was small enough to get in between the CRT and lower fan screws.
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On Sun, Apr 20, 2025 at 11:33 AM, Mark Vincent wrote:
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Re: Tektronix 2247A problem. Keep or return?
Jay,
Recapping is best. Nichicon ULD, UCY, LGR and UHE are good choices. I suggest mounting them so that there is a gap between the bottom of the caps and the board to allow for air flow under them and to be able to solder on each side of the board. Replacing any other ones on boards would be best. Raising the capacitance from original values is fine. Oil the fan. The power supply is hard enough to remove in effort so doing a full job is best to keep from going back in to do work a second time. Mark |
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Re: Tektronix 547 Lack of Sweep or Intensity Control
Hi Mark & Deon:
Just an update on what I¡¯ve tried so far. My next step will be to borrow a friend¡¯s VTVM so that I can make some voltage measurements around the HV circuit (especially the Intensity circuit which still eludes me). That aside for now, here is what I have checked: *Crt circuit: Checked R803 and value is fine. No attempt to change it at this point. Checked values of C806 and C803 ¨C they are ok. Haven¡¯t tried testing or replacing C802 yet, but voltage looks clean and steady on it. Isolated D831 and checked with ohmmeter ¨C looks normal. Tried moving HV pot back and forth several times ¨C no improvement. Tested the 500mmfd caps on the transformer assembly that I removed and replaced with another and those measured well value-wise. Since changing out the transformer assembly didn¡¯t seem to change scope behaviour, I¡¯m thinking those caps were not the problem, although I could test the ones on the replacement assembly next. *A &B Sweep Generators: Seeing same thing on both, which is a little suspicious. Used the test setup incorporating the calibrator signal that Tek suggested at the front of each schematic. BTW, serial is 5474, so I¡¯m using the 100-6739 schematic for each timebase. Interestingly, on both, I am getting a semblance of sweep on the crt once again, but it¡¯s very jittery. Looking at the collector of Q65 (multivibrator ckt) there is signal but frequency is random. There is square wave at D85 in each timebase, but of course is also random in frequency. Ditto for V93A output at D98¡¯s cathode. I have not tried replacing C76 yet (4.7uF on my model), but since the bahaviour is the same on both timebases, it seems unlikely that they would both fail (although I¡¯m keeping an open mind). There seems to be something common between the two timebases that¡¯s screwing both up. Power supplies come to mind but they look fairly normal except for +350V ripple, which I should address next. Will keep digging. Your support is much appreciated! This is new territory for me. Gordon |
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Re: Tektronix 2247A problem. Keep or return?
I think I see what's going on with the scope. On the 'measurement processor' circuitry (A16 processor PCB) , there's a power-on reset circuit that monitors the 5V rail and sends a reset to a few of the microprocessors if the voltage isn't up to snuff. I see the SYS_RESET being held low when the problem occurs and doesnt recover until the unit has been turned off for a while. There's an appreciable amount of ripple on the 5V supply which I think might be causing this. I have a good feeling that a re-cap is going to make things better.
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I don't see any diodes on the PSU pcb with ZM or ZS marking and no RIFA caps.. It should be a fairly straightforward recap. Harvey, I pulled the PSU from my 2247A this morning and tested continuity from the extra lead on the 3 lead electrolytics and they don't appear to be connected to anything. Definitely not the neg lead of the caps and not ground. It seems like a mechanical choice in this case. On Sat, Apr 19, 2025 at 09:09 PM, Harvey White wrote:
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Re: MSO4104 Problems
I think the best hope for this scope is to see if there is a way to get it back to how it was before the firmware update. I have no idea if this is possible, but this scope was useable before the firmware update. It is a total mess since the FW update. Now that channel 1 is fixed, it might be possible to restore full operation on CH1, CH2 and CH4 but with limited operation on CH3. This may mean restoring old cal data and maybe the old firmware.
I get the impression that some custom hardware and software is required to do a fresh calibration and I don't have access to this. Tek won't cal it if there is a problem with CH3 and I'm fairly certain they won't want to repair it either. |
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453 scope, MOD 703K and MOD 703H
have a trio of Tek 453's. Two are MOD 703K and the other is MOD 703H.
I have had one of the 703K's on my bench for many years. Of late, it has developed trigger issues. I can only get a stable waveform if feed it a square wave. It will not trigger on a sine wave. The other 703K triggers fine, but has a few other issues, chief among them it is missing the center control knob for the sweep control. Not just the knob, but the center shaft. Not clear what is actually missing internally since that control is fairly well buried (as is everything else on these). The 703H has many other issues, stability wise, so it may become a donor for missing knobs/controls, feet etc. Thoughts on the trigger issue? |
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Re: Tektronix 2247A problem. Keep or return?
Generally, another ground with intentions of stability.? When replacing with a two lead capacitor, make sure that both grounds are shorted together.? Tek often used the two leads as a ground jumper.? Leaving that off gives lots of interesting errors.
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Harvey On 4/19/2025 7:45 PM, Jay Czaja via groups.io wrote:
I got to sit down with my 2247A this afternoon and have come to the conclusion that above all else, the power supply needs some attention. All of the LV supply rails, with the +7.5V rail being the only exception, are measuring slightly above or just at the max of allowed ripple. |
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Re: How to clean the finger contacts on an SG503
The cardstock that I use is Vellum Bristol. Neenah Exact Vellum Bristol, specifically, and I picked up a bundle of it at Sam¡¯s club a few years ago. Most office supply stores will probably have something similar and sufficient. I¡¯m not saying that I know that to be Tek spec, but I¡¯ve only seen recommendations FOR and not against using vellum bristol cardstock.
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