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Re: Disintegrating Handle on my TM503
You might consider a length of garden hose or the equivalent for an inexpensive replacement.
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Harvey On 2/12/2025 3:51 PM, Benjamin Badrakh via groups.io wrote:
Hello people of TekScopes, |
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Re: Disintegrating Handle on my TM503
Hi Benjamin. I personally have not had any success restoring old tektronix handles. However there are a lot of companies who make equipment handles. Ones intended for audio equipment usually will work if you are not going for an authentic restoration. Just google. Audio equipment handles. Here is one I found easily.
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Re: Disintegrating Handle on my TM503
On 2/12/25 13:51, Benjamin Badrakh via groups.io wrote:
Has anyone here experienced and found a solution to this problem?Not with a tm503 yet, but most 5xx scopes. A method I like is wrap with leather and sew shut. I might have some spare tek blue handle material from other cases. Would need to be cut down probably... three layers of heat shrink would give a decent handle grip... |
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Disintegrating Handle on my TM503
Hello people of TekScopes,
I have a TM503 with a disintegrating handle. The blue outer sheath for the steel inner core has become brittle and ripped open. This just leaves the thin strip of rusty steel in its place, which is not exactly comfortable to hold and may give me tetanus. I often carry this unit around back and forth between school and home, so the handle is functionally important for me. I've tried various solutions such as cardboard and tape, but they always fail prematurely. Has anyone here experienced and found a solution to this problem? Thanks, Benjamin |
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Re: SC504 Trace Shadow
Ozan,
I took both of the hybrids out for inspection. I found an open trace on Pin1 and Pin2 of the hybrid that was installed on channel 2. I tried to repair the trace but ended up damaging several other traces. I don't think I can fix those. History here is that I had swapped Ch1 Hybrid and Ch2 Hybrid expecting the symptoms to switch, they didn't. I did this several days before I asked for help. I wonder if the scope would have worked with the open traces in the hybrid 1 slot as original. The part numbers on both hybrids are the same, but the open circuits look intentional. I also found a defect on one of the rubber band contacts, Contact #8. These switches are a bad design. I have another SC504 on order. Thanks for your help. This project is on hold for now! Barry |
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Re: Alternative calibration pulsers for the Tek 11801 family.
Reg, This grp, no phoots attached to the messages.
Like many other groups.io, please use this preoceedure to post photos Left hand column>> "photos" section: >>New Album>>name it>>drag or select all photos We have the older Leo Bodnar 40 pS pulser, no issues use with 500 M or 1 GHz analog scopes. Note that in 2025, his pulser formats, specs and cost have been updated. Suggest you ask Leo, at his fine website support: Cheers, Jon |
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Re: SC504 Trace Shadow
Hi Barry,
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If you look at hybrid schematic on TekWiki pin 1 is the mid point of a 845-ohm to ground and 1.21k to +5V. In your measurement Ch2 hybrid shows ~ 0.366-0.649V at pin 1. This means a current on the order of 4mA is pulled from pin 1 (assuming hybrid is good). Nothing around Q1455 should be able to pull this much current (resistors are too large to support 4mA) in normal operation except CR1457 in Trigger View, even then 0.366V looks low. If you exercise “Trig View” switch does anything change? In 1-2 or 1+2 modes do the voltages at collectors of Q1455 and Q1555 change? In this mode emitter currents are removed, transistors shouldn’t be able to pull pin1 lower. Most likely collector of Q1555 will go to 2V, this would enable Ch1 to be displayed. Likely you will find collector voltage of Q1455 still low. Assuming collector of Q1455 won’t go to 2V even in 1-2 or 1+2 modes, does lifting one leg of CR1457 change collector voltage of Q1455 to 1 to 2V range in 1-2 or 1+2 modes? Could there be a solder bridge or some kind of short on pin 1 node of Ch2 hybrid? If both Q1455 and CR1457 is removed and pin 1 is still not at 2V hybrid is suspect. As a side note 0.7V at pin1 should have disabled Ch2 as well. I don’t see why Ch2 is displayed with pin1 below 1.5V. Ozan On Tue, Feb 11, 2025 at 02:11 PM, Barry Breaux wrote:
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Alternative calibration pulsers for the Tek 11801 family.
I was going to attach screenshots from my 11801/SD-32 comparing one of Leo Bodnar's new LBE-1322 pulsers to the calibrator in the 11801.
Seems I'm not allowed to do that. Don't know why or care. I'll simply state the result. My 11801 calibrator output has a 15 ps rise time averaged over >4096 measurements. I measured 19 ps for my LBE-1322. The calibrator signal proves that the head is faster than the DUT. If you have an 11801 family instrument which either has a failed or the slow revised model calibrator, this is a superb instrument. You want it! Have Fun! Reg |
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Re: SC504 Trace Shadow
Just to make sure it is Ch2 and not the trigger path showing up on screen for some reason, if you change trigger source to Ch1/Ch2 does anything change?
****When I change the trigger from CH1 to CH2 it does change. If in CH2 the Sine Wave becomes synchronized as it should. If I switch the trigger to CH1 it shows the CH2 Sine Wave but it is NOT synchronized. ****Nothing changes when switching between CH1 and CH2. Are collector voltages of Q1455 and Q1555 same as before after delay line fix? ****Here is what they are now... ****CH 1 Selected Q1455 E=-0.680 B=-0.047 C=0.649 Q1555 E=-0.680 B=0.000 C=1.160 ****CH 2 Selected Q1455 E=-0.681 B= 0.277 C=0.366 Q1555 E=-0.681 B=0.000 C=1.047 I assume pin 3 voltage of the hybrids will be different now, any change to pins 3,4,5,16,17 on CH2 hybrid after delay line fix? ****CH 1 Selected Pin 3=+2.718 Pin 4=+2.754 Pin 5=+1.722 Pin16=-0.844 Pin17=-0.841 ****CH 2 Selected Pin 3=+2.721 Pin 4=+2.721 Pin 5=+1.722 Pin16=-0.846 Pin17=-0.838 It is possible Ch1 is visible but it is off the screen and bouncing off the CRT wall giving you ghost image. ****I don't think so. I have a square wave on CH1 and a Sine wave on Channel 2. Does moving Ch1 Y offset knob change anything? ****There is a slight jitter in the trace when CH1 position is 100% fully clockwise. The jitter goes away at 99% fully clockwise. What are the voltages of pin 16 and pin 17 (gives an idea about channel DC level) on Ch1 hybrid? Pins 3,4,5 are shared with Hybrid 2 so they will be the same as Hybrid 2 voltages. ****CH1 Hybrid with CH 1 Selected Pin16=-0.871 Pin17=-0.805 ****CH1 Hybrid with CH 2 Selected Pin16=-0.871 Pin17=-0.805 Checked and doubled checked. Seems like the voltages varies a bit during each test cycle. Thanks for looking at this. I am learning a lot, but a ways to go Barry |
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Re: SC504 Trace Shadow
Just to make sure it is Ch2 and not the trigger path showing up on screen for some reason, if you change trigger source to Ch1/Ch2 does anything change?
****Nothing changes when switching between CH1 and CH2. Are collector voltages of Q1455 and Q1555 same as before after delay line fix? ****Here is what they are now... ****CH 1 Selected Q1455 E=-0.680 B=-0.047 C=0.649 Q1555 E=-0.680 B=0.000 C=1.160 ****CH 2 Selected Q1455 E=-0.681 B= 0.277 C=0.366 Q1555 E=-0.681 B=0.000 C=1.047 I assume pin 3 voltage of the hybrids will be different now, any change to pins 3,4,5,16,17 on CH2 hybrid after delay line fix? ****CH 1 Selected Pin 3=+2.718 Pin 4=+2.754 Pin 5=+1.722 Pin16=-0.844 Pin17=-0.841 ****CH 2 Selected Pin 3=+2.721 Pin 4=+2.721 Pin 5=+1.722 Pin16=-0.846 Pin17=-0.838 It is possible Ch1 is visible but it is off the screen and bouncing off the CRT wall giving you ghost image. ****I don't think so. I have a square wave on CH1 and a Sine wave on Channel 2. Does moving Ch1 Y offset knob change anything? ****There is a slight jitter in the trace when CH1 position is 100% fully clockwise. The jitter goes away at 99% fully clockwise. What are the voltages of pin 16 and pin 17 (gives an idea about channel DC level) on Ch1 hybrid? Pins 3,4,5 are shared with Hybrid 2 so they will be the same as Hybrid 2 voltages. ****CH1 Hybrid with CH 1 Selected Pin16=-0.871 Pin17=-0.805 ****CH1 Hybrid with CH 2 Selected Pin16=-0.871 Pin17=-0.805 Checked and doubled checked. Seems like the voltages varies a bit during each test cycle. Thanks for looking at this. I am learning a lot, but a ways to go Barry |
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Re: SC504 Trace Shadow
Hi Barry,
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Nice find with delay line. Just to make sure it is Ch2 and not the trigger path showing up on screen for some reason, if you change trigger source to Ch1/Ch2 does anything change? Are collector voltages of Q1455 and Q1555 same as before after delay line fix? I assume pin 3 voltage of the hybrids will be different now, any change to pins 3,4,5,16,17 on CH2 hybrid after delay line fix? It is possible Ch1 is visible but it is off the screen and bouncing off the CRT wall giving you ghost image. Does moving Ch1 Y offset knob change anything? What are the voltages of pin 16 and pin 17 (gives an idea about channel DC level) on Ch1 hybrid? Pins 3,4,5 are shared with Hybrid 2 so they will be the same as Hybrid 2 voltages. Ozan On Mon, Feb 10, 2025 at 10:56 AM, Barry Breaux wrote:
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Re: SC504 Trace Shadow
Ozan,
Select CH1 OR CH2 and trace shows CH2. I currently have a square wave going to CH1 AND A sine wave going to CH2. Regardless of the switch position CH2 is displayed. (Except when CH1-CH2 is selected. The trace reflection is there all the time to some extent. Decreases with intensity. Thanks! Barry |
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Re: SC504 Channel Control issues
Greetings!
I made a little progress. One of the delay lines was open. Perhaps that was my interment problem. I fixed that and got CH2 displaying. The problem is (as before I lost both traces) that CH2 is displayed when CH2 is selected(correct) AND when CH1 is selected(incorrect). Barry |
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Re: SC504 Channel Control issues
My comments are inline.
Ozan On Sun, Feb 9, 2025 at 03:20 PM, Barry Breaux wrote: ..... If I short out the delayMost likely the delay line is made of a lossy coax (there is an explanation in Tektronix technical series) and it has some resistance from end to end. Shorting at the F&I board side or at the attenuator presents a different resistance to the next amp. This reading shows an issue, according to schematic should be either 1V or 2V but this could be because of pin 5 below. 3, -0.03, -0.03It looks these are also wrong. My guess is common mode (pin 5) has an issue, more about it later. 16, -0.57, -0.57Is the Y position knob at one of the extremes? This can also be the result of pin5 so for now it is OK. We expect 16 and 17 to be similar and independent of channel switch in normal operation. They will deviate with position knob or input signal. However, no need to think about them for now. 19, 4.99, 4.99This is good. I took all these measuements today, but I suspect warmup was not sufficient.The voltages are quite a bit off, warm up is not an issue. Pin5 at 0V doesn't sound right, it may also be yanking pin3 and also setting pin4 ~0V. Most likely Q1462+Q1460 is pulling too much current. There could be several possibilities: - Is J1350/P1350 connected properly? They dump current to emitters of Q1462 and Q1460. Without this current Q1462/Q1460 will pull extra current from pin 5 - It is unlikely extra current is because of bad Q1462/Q1460 I recommend: - Look at voltages at base and emitters of Q1462 and Q1460 - Look at B/E/C voltages of Q3237 and Q3236. They are sourcing current to emitters of Q1462 and Q1460. Without them extra current is pulled from pin5 of the hybrid. Ozan |
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Re: SC504 Channel Control issues
The condition of t; his SC504 has changed. I am currently unable to see a trace from either Ch1 or Ch2. From the beginning I have been seeing an intermittent problem of not seeing either channel. If I short out the delay line from the F&I board the traces come to the center of the display. Therefore the problem is before the delay line. What I don't understand is why shorting out the delay line from the Main board doesn't produce a trace.
OZAN, pin 1 isn't ~1V OR ~2V. CR1457 Anode: CH1=-0.645, CH2=-0.360 Q155 CH1 Select E=-0.676V B=-0.000V C=+0.708V Q155 CH1 Select E=-0.679V B=-0.000V C=+0.688V OZAN, these are the pins you questioned. Pin, Ch1 Select, Ch2 Select 1, -0.65, -0.35 3, -0.03, -0.03 4, 1.37, 1.37 5, -0.01, -0.01 16, -0.57, -0.57 17, -0.05, -0.05 19, 4.99, 4.99 I took all these measuements today, but I suspect warmup was not sufficient. Barry |
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