Re: Tektronix 2465A... With error code Test 05 Fail 24
Well I have replaced the U500 and the scope is triggering just fine.
However; when I changes Volts/Div scale without changing the input signal the display jumps off center. If I recenter the display and measure the amplitude and frequency it is accurate. If I switch scales again I have to recenter the the display. This happens no matter which channel I am using.
I have tried to search the forum for possible answers but I am at a loss as to what this is... Is it a problem with the horizontal or the vertical calibration or the CRT or my eyes?
Any suggestions would be appreciated.
Its always something.
John w.
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Re: FOUND: broken Tektronix WM490f (to 140GHz) and/or WM490d (to 170GHz) mixer(s)
Fyi: The jlcpcb cnc factory on youtube...not a small operation.
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Re: Substitute parts for 12au6s on 575 curve tracer
You can use 6AU6 in place of 12AU6. They have identical characteristic, the only difference being the heater voltage, 12.6 V @ 150 mA for the 12AU6 vs 6.3 V @ 300 mA for the 6AU6.
You can compensate the difference by adding a resistor in series with the heater. Sure, it's an inefficient solution, but it works seamlessly.
Max
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Trouble Getting Screenshots From Tektronix TDS 754D
Hello, I have a TDS754D. Works fine but I¡¯m having trouble getting some simple screenshots out.
I used the hardcopy function, export as .bmp mono color and export to floppy. For some reasons it will sometimes work, sometimes the image is corrupted or just unreadable.
See here:
Any idea why this is happening?
I¡¯m reading the files using a USB floppy drive and a Windows 10 laptop if that helps.
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Re: Substitute parts for 12au6s on 575 curve tracer
There were actually serious attempts at replacing some tubes with JFET alternatives in very-high-volume applications like telephony (1960s-70s). I think the most well known is Teledyne's "FETRON," which was JFET circuits packaged up on a tube base for direct replacement in certain spots. I recall discussions over the years about these and home-made equivalents. Whatever you have in there is probably a similar approach, whether figured out by Tek or someone else. Don't toss it, but study up and figure out if it's legit, then maybe fix it up to work properly. If it doesn't work out, then as others have said, you can always go back to the original tube circuits. Good luck.
Ed
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Re: Substitute parts for 12au6s on 575 curve tracer
And other examples of replacing a 6AK8 tube ( triple diode/triode tube ), with a solid state replacement
in HF Rx receiver using HV MosFets.
;wap2
Clearly, the simple substitution with HV Fets in radio Rx circuits
will Not be the same as specific circuits in a precision Tek measurement instrument....
am simply providing "food for thought" ideas for intrepid experimenter; use at your own risk !!
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Re: Substitute parts for 12au6s on 575 curve tracer
Any possibility that a HV MosFet might be substituted ?
LND150 Mosfets have been substituted for a different tube ( the 12ax7 ; which is Not the 12au6 discussed herein for the Tek 575)
See:
And likely, one might have to modify the circuit or bias somewhat, depending on the particular tube circuit.
I have successfully directly replaced triodes and dual-triodes using HV Fets in some old WWII military surplus equipment ( such as all of the triodes in the Rx section in the URC-4 , etc. ) with good results and no frequency shift nor distortion. Crazy but it worked very well. Also had success doing such with the BC-1335 Rx section which has a large compliment of tubes.
With such a modern diverse selection of IRF type HV MosFets there could be some interesting experimental work to be tried...
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Re: Replacement Fan for 2465B/2467B
Common NIDEC or Mineba fan, usually the original can be recussitated if correct procedure is used.
Jon
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Re: SC503 -12V power supply
Hi Barry,
I think you fixed the root cause of why shorting across C-E of Q8051 didn't work. I was expecting to see the same voltage as if Q7042 was removed (+0.6V) but at this point the regulator should be able to control the voltage. Do you still see ~ -33V at the output?
Do you have the original transistors to try or was Q7042 the shorted one?
Q7042 (151-0103-00) cross references to 2n2219A, plain 2n2219 has a Vceo of 30V and lower fT than 2n2219A. This device will see Vce~ 33V in normal operation.
page 6-3 of:
Ozan
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On Mon, Dec 23, 2024 at 01:47 PM, Barry Breaux wrote:
Ozan,
I found a broken trace which I repaired.
I also swapped out a few transistors.
Today I am measuring -0.48 volts when I short across C-E of Q8051.
I understand that 2N2222A is a lower wattage equivalent to the 2N2219. I have
ordered additional 2N2219. The 2N2219 was/is shorted.
There is a .3VPP oscillation at the base of Q7042. a 50mv ripple on the +12V
and a .2V ripple on the -33.5V.
I am still plugging away at it.
Thank you!
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Re: Replacement Fan for 2465B/2467B
Is there a good solid replacement?
Thanks,
Monte
I have bought many of these for 2465/67B scopes over the years with good results.
eBay listing:
Nidec Beta V FAN TA300DC 12V 0.16 Amp A33315-16 SlimLine 80x80x20mm Light JK-33
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Replacement Fan for 2465B/2467B
I've read through a lot of posts regarding the replacement fans. Is there anything outside of the parts description from the service manual that I need to take into account? Both my 'scopes need the fans replaced. Tried cleaning and re-oil; no difference.
Looking for something that is quite yet moves the volume.
Is there a good solid replacement?
Thanks,
Monte
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
I switched to x1 and the MAG light tuned off. Only UNCAL is still on, even though I have already cleaned the pot. Switched the triggering back and forth between AC and DC. Set the Source switch to "INT". v/div is set to .2v/div and ms/div is set to 1ms/div. Trace is still invisible :(
Could you send the parts list via DM? Thank you, Mark!
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On Mon, Dec 23, 2024 at 12:39 PM, Mark Vincent wrote:
Jeffrey,
The uncal lights and x5 lights are still on. The uncal lights should turn off
when you go to the detent position which you will feel. As others have said,
the switch could be dirty making the light come on even though it is in teh
detent position. Set triggering to a-c or d-c. Set the source switch, lower
right corner, to int. Set the v/div switch to .2 or .5V/div and 1ms/div for
horiz.. That should get the trace on the screen.
Having two A versions as well as the 453/A and 454, I know there are a number
of resistors that are underrated in wattage that caused problems in mine. The
454A has ones that are lower power rated than is being dissipated, especially
in the horizontal section. You could very well have resistors that are well
out of tolerance or open. Clean the pins and sockets of the transistors. That
will cause problems like you are seeing. If you want a list of parts I changed
in mine, I will send it.
Mark
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Re: SC503 -12V power supply
Ozan,
I found a broken trace which I repaired.
I also swapped out a few transistors.
Today I am measuring -0.48 volts when I short across C-E of Q8051.
I understand that 2N2222A is a lower wattage equivalent to the 2N2219. I have ordered additional 2N2219. The 2N2219 was/is shorted.
There is a .3VPP oscillation at the base of Q7042. a 50mv ripple on the +12V and a .2V ripple on the -33.5V.
I am still plugging away at it.
Thank you!
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
Yes I just downloaded it. Will spend some time reading it.
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
CH 2 is the same. Vertical Position knobs work in Beam Finder mode.
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
Thank you Ben for the detailed info - I really appreciate it! Here are my measurements for the reference points you listed:
Junction between C369 and L369: 12.04V
L343 (any side is fine for just sinple voltage measurements): -11.98V
Junction between VR339 and R339: -6.44V
Junction between R311 and R312: 0.897V
Base of Q424: 8.94V
Base of Q324: 9.7V
Base of Q474 and Q347: 11.86V and 10.68V (I assume it's Q374? Can't seem to find Q347)
Emitter of Q414 and Q314: 0.174V and 0.192V
I hope this helps to some extent. Also like I mentioned in another reply, the pot for the A & B VAR knob has been cleaned and it seems to work fine but the UNCAL light stays on no matter how I adjust the knob.
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Re: Repair Tektronix TDS 520
Thanks for the reply. Today I unsoldered about 20 chips that were near the capacitors to see if there were any interruptions in the conductor tracks. I didn't find any interruption.
How do you think I could continue?
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
- Adjusted Ch1 var and the "uncal" light is off, as I mentioned in post #207706
- The var for A & B time base is in detent, as you can see clearly in my video. That said, I cleaned the pot and it measured smoothly from around 5K ohm to 0 while I turn the red "VAR" knob.
- It is now set to "internal".
Still nothing.
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
Jeffrey,
The uncal lights and x5 lights are still on. The uncal lights should turn off when you go to the detent position which you will feel. As others have said, the switch could be dirty making the light come on even though it is in teh detent position. Set triggering to a-c or d-c. Set the source switch, lower right corner, to int. Set the v/div switch to .2 or .5V/div and 1ms/div for horiz.. That should get the trace on the screen.
Having two A versions as well as the 453/A and 454, I know there are a number of resistors that are underrated in wattage that caused problems in mine. The 454A has ones that are lower power rated than is being dissipated, especially in the horizontal section. You could very well have resistors that are well out of tolerance or open. Clean the pins and sockets of the transistors. That will cause problems like you are seeing. If you want a list of parts I changed in mine, I will send it.
Mark
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Re: Tektronix 454A Oscilloscope No Trace but Beam Finder works fine?
Still trying to get a bit further without having to take measurements may yield more info.
If both channels show the same behavior: Since bad contacts are rather frequent with old equipment like this, wiggle the various transistors in the vertical amplifier; they¡¯re all socketed. Also slightly move back and forth vertical position adjustment pot. Don¡¯t know by heart if and where in this model. Preferably do this while power is off.
Should you do measurements at/near the vertical amplifier, be very careful not to short the outputs (or plates) to ground, which very likely would kill the output transistors.
Raymond
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Jean-Paul
Craig Cramb
Raymond Domp Frank