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Re: Thinking on CRT restorations for double peaking tubes.
I am passing this on from an ex-CRT engineer I know at the museum. - Dave
1. Increase the nominal 6.3V heater to 8V at least, possibly 10V if the cathode current is very weak 2. Keep heater and cathode very near the same potential 3. Apply AC voltage to the control grid, up to +6V Max. compared to cathode 4. Set the first anode at +100 to 150V to collect the electrons 5. Limit reactivation time to ~10 minutes; 20 minutes Max. Here¡¯s a 2015 note from Thomas Electronics where they recommend operation with cathode current for 24 hours: Normal CRT operation with cathode current is always good, especially in storage tubes where the flood gun electrons can form an ion pump. Mesh storage CRTs at Tektronix (in the 7613, 7623, etc.) had the best vacuum levels measured. Re: Potential leaks in glass-to-metal seals. Glyptal can be applied to the cracked glass, or before straightening badly bent pins. |
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Re: 2465 Calibration
If you have ever calibrated a 2465 or 2467 series Oscilloscopes, it is best to have the correct equipment because it takes a long time to calibrate one. It is a very manual, time-consuming operation to perform CAL 01 and CAL 02 Steps and they have to be performed all at once.
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Having the correct equipment available (for me anyway), makes it less frustrating and it flows "easier" with the right stuff. That equipment being: 1 Tektronix TM504 or TM506 - to house and power the Calibration Modules 1 Tektronix PG506 - Voltage Generator(200uV to 50V DC or Square Wave), High Amplitude and Fast-Rise Generator 1 Tektronix TG501 - Time Mark Generator (1ns to 5 Second) 1 Tektronix SG503 - 50 kHz Reference & 250kHz to 250MHz Constant Amplitude Generator and RG-223 Cable 1 Tektronix SG504 - 50kHz Reference & 245MHz to 1050MHz Constant Amplitude Generator and Leveling Head Tunnel Diode Pulser, Overload tester, etc. Misc. Cables, Attenuators etc. I would recommend you have the right equipment if you need to calibrate one or many. The Batteries and/or Battery Backed-up SRAM Modules in these are old and you lose calibration parameters when it dies, forcing you to go through the calibration procedure. Just my opinion, of course. Ross -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of jimbert4 via groups.io Sent: Wednesday, April 20, 2022 4:29 PM To: [email protected] Subject: Re: [TekScopes] 2465 Calibration Seems like everyone is overly concerned about the accuracy of the calibration equipment. How accurate can an oscilloscope like this measure periods and voltages? On the horizontal axis there are 50 divisions and you could measure times on it to about double that, so call it 100. That's only 1% accuracy. Most waveform generators, even inexpensive ones are spec'd at less than 20ppm (.002%) frequency accuracy and a few ppm stability. The vertical axis is even less at 40 divisions, so readings to about 80 or 1.25%. The oscilloscope may beat most waveform generators' voltage specs, I'm not sure. Here's a spec from a $200+, 80 MHz waveform generator: Amplitude resolution 1mVpp Amplitude stability ¡À 1% ¡À1 mVpp (@ 1 kHz,>10 mVpp) Amplitude flatness ¡À1%(0.1dB)<10MHz ; ¡À2%(0.2dB)<10MHz~50MHz ¡À10%(0.9dB)<50MHz~70MHz; ¡À20%(1.9dB)<70MHz~80MHz So the amplitude stability is of the same order as the vertical axis, at least at 1 kHz, and flatness gets way worse at the higher frequencies. (I'm not sure what flatness means. Does it refer to the voltage variation across a particular frequency range?) But how accurate do I need to measure a signals amplitude on an oscilloscope anyway? |
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Re: 2465 Calibration
Seems like everyone is overly concerned about the accuracy of the calibration equipment. How accurate can an oscilloscope like this measure periods and voltages? On the horizontal axis there are 50 divisions and you could measure times on it to about double that, so call it 100. That's only 1% accuracy. Most waveform generators, even inexpensive ones are spec'd at less than 20ppm (.002%) frequency accuracy and a few ppm stability. The vertical axis is even less at 40 divisions, so readings to about 80 or 1.25%. The oscilloscope may beat most waveform generators' voltage specs, I'm not sure. Here's a spec from a $200+, 80 MHz waveform generator:
Amplitude resolution 1mVpp Amplitude stability ¡À 1% ¡À1 mVpp (@ 1 kHz,>10 mVpp) Amplitude flatness ¡À1%(0.1dB)<10MHz ; ¡À2%(0.2dB)<10MHz~50MHz ¡À10%(0.9dB)<50MHz~70MHz; ¡À20%(1.9dB)<70MHz~80MHz So the amplitude stability is of the same order as the vertical axis, at least at 1 kHz, and flatness gets way worse at the higher frequencies. (I'm not sure what flatness means. Does it refer to the voltage variation across a particular frequency range?) But how accurate do I need to measure a signals amplitude on an oscilloscope anyway? |
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FS: Four NOS Tektronix tubes in boxes
Tektronix tubes
Four tubes: 154-0016-00, ¡°Tube 7M 6AL5¡± 154-0022-00, ¡°Tube 7M 6AU6¡± 154-0187-00, ¡°Tube 9M ECC88/ 6DJ8¡± 154-0278-00, ¡°Tube 9M 6BL8/ECF80¡± In boxes, as-is, untested. I have ended up with a rather varied collection of tubes, something that I really don't do anything with and within that collection I found the four tubes listed. Boxes are in pretty good shape as you can see from the picture (which it turns out I cannot attach.) Seems like a waste for them not to go to someone that can use them. There are some others of the same types (but not specifically in Tektronix boxes) that I¡¯m glad to include. Make offer plus shipping and insurance. USPS money order. Paypal by arrangement. Located in Everett, WA. 73, Grant KB7WSD |
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Re: 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase
As it turns out, all the 6 AF118¡¯s are bad. 2 are completely dead, and the 4 others show a diode across EC.
KSA992 are not available in my area, and I don¡¯t feel like ordering them online. BC556B are available though. Is there anything wrong with using the AF118 I ordered? They were original to my unit after all. Thanks Dave, but ordering 2N4890 from Boca would be quite expensive from Europe. Not a good option. I tried replacing all 6 of them with 2n2907A. After doing so, not only the problem I have did I not disappear, but another one popped up. Sparkles spots are randomly appearing on the trace. They were not present before. Not a good sign. To summarize, the original issue was no ALT whatsoever, and no Delayed Time base. When in regular ALT position, only A is displayed. I can easily go pickup some BC556B¡¯s tomorrow. |
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Re: 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase
Thanks for doing the research, Dave! I had not seen a datasheet with a 2.3pF value, but seeing that the ICmax spec is 50mA, I'm pretty sure you're right. The 3906 typically has around that value of Cob, but the breakdown voltage requirements rule out its use.
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--Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 4/20/2022 13:46, Dave Wise wrote:
Thanks for making me work harder, Tom. |
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Re: 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase
Thanks for making me work harder, Tom.
Some spec sheets say 13pF but others say 2.3pF. I believe the latter. Cob was more important than fT in Q184/Q373 because it is switching, with a wide output swing subject to Miller effect. fT is more important for Q554/Q564. Tek replaced those - but not Q173/Q184/Q373 - with 2N4890. Cob is of medium importance on Q554/Q564 ¨C the base has low-impedance drive so Miller effect is not happening. 2N4890 fT is 100MHz, BVceo is 40V and Cob is 15pF. If you believe the schematic annotations in the 547 manual, Q554 can see 65V C-E. Since the base is not floating around, BVcbo (60V) is more important than BVceo, but 2N3906 BVcbo is only 40V and you run the risk of breakdown. Q424 is in Delay Pickoff with a tunnel diode on its base; Miller is important and I¡¯m surprised 2N4890 worked well. It seems to me that 2N3906 would be fine here, or KSA992. When all is said and done, if I ever replace Q554/Q564 in my own 547, I will try KSA992 or BC556 before 2N3906, unless I selected the latter for breakdown. For what it¡¯s worth, 2N4890 is in stock at Boca Semiconductor, $2 each plus $5 shipping. Dave Wise From: [email protected] <[email protected]> On Behalf Of Tom Lee via groups.io Sent: Wednesday, April 20, 2022 12:16 PM To: [email protected] Subject: Re: [TekScopes] 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase Hi Dave, I'm a bit confused about your comment re: slow 2N2907. That part has over twice the ft and half the output capacitance of the original transistor. A 2N3906 would do even better (still lower capacitance, somewhat higher ft). There might be other reasons to disfavor these parts, but I don't think relative slowness is one of them. --Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 <> On 4/20/2022 12:00, Dave Wise wrote: From the 547 mod summary: At S/N 14710, Q424, Q554, Q564 were changed from 151-0063-00 to 151-0322-00 (2N4890) ¡°to improve availability¡±. Heat sinks removed because no longer needed. |
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Re: 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase
Hi Dave,
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I'm a bit confused about your comment re: slow 2N2907. That part has over twice the ft and half the output capacitance of the original transistor. A 2N3906 would do even better (still lower capacitance, somewhat higher ft). There might be other reasons to disfavor these parts, but I don't think relative slowness is one of them. --Cheers Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 4/20/2022 12:00, Dave Wise wrote:
From the 547 mod summary: At S/N 14710, Q424, Q554, Q564 were changed from 151-0063-00 to 151-0322-00 (2N4890) ¡°to improve availability¡±. Heat sinks removed because no longer needed. |
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Re: 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase
From the 547 mod summary: At S/N 14710, Q424, Q554, Q564 were changed from 151-0063-00 to 151-0322-00 (2N4890) ¡°to improve availability¡±. Heat sinks removed because no longer needed.
They did not change the bias. Based on my investigation of substitutes for Q173, Q373, and Q184, I¡¯d recommend KSA992 or BC556 instead of the comparatively slow 2N2907. Watch the pinout, it¡¯s different. HTH, Dave Wise From: [email protected] <[email protected]> On Behalf Of Stephen via groups.io Sent: Wednesday, April 20, 2022 9:23 AM To: [email protected] Subject: Re: [TekScopes] 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase Hi all, Forgive for reviving this older post, but It¡¯s the closest and first I found regarding the 2N2207¡¯s in a 547. I found that the issue I have with my timebase is probably because both Q554 and Q564 are bad, as well as Q424. They are actually not 2N2207¡¯s, but all 3 are marked ? AF118 4ms ?. I ordered a dozen AF118 from my local shop, but they¡¯ll only arrive sometime next week. Meanwhile, I have a few 2N2907A¡¯s. Could those do the trick in these positions? Any resistor change to expect? I¡¯d like to see if these could work. Thanks in advance. |
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Re: Trade: 7B70 Pull Tab for a 7B53?
Rats. No sooner than I sent that than I realized that I meant 7B53A, not 7B53 (which, from what I understand, doesn't exist).
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "n4buq" <n4buq@...> I have what appears to be a NOS pull tab for a 7B70 (just the plastic part) that |
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Re: 321A 2N2207 transistor replacement: Ge-Si replacement sensitivity in the timebase
Hi all,
Forgive for reviving this older post, but It¡¯s the closest and first I found regarding the 2N2207¡¯s in a 547. I found that the issue I have with my timebase is probably because both Q554 and Q564 are bad, as well as Q424. They are actually not 2N2207¡¯s, but all 3 are marked ??AF118 4ms??. I ordered a dozen AF118 from my local shop, but they¡¯ll only arrive sometime next week. Meanwhile, I have a few 2N2907A¡¯s. Could those do the trick in these positions? Any resistor change to expect? I¡¯d like to see if these could work. Thanks in advance. |
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Re: DM501A Input Leakage Source
Roman,
I agree with what Tom Lee mentioned. I can¡¯t remember any meter in the lab (over a dozen) including brand new units from various manufacturers that doesn¡¯t show some minor offset with the input folating. Remember what type of input impedance you are dealing with that is floating without anything connected. Have you performed calibration of these units? If you will notice in the manual Tek instructs you to connect a short between the input high and low jacks and then adjust the internal zero control for a reading of 0000 on the display. So from this it is somewhat alluded to that Tek knows that there will be a possible inherent offset reading if you don¡¯t short the input. If you decide to pursue this issue I am sure that it will become entirely academic in nature. You may find some stray leakage paths but most of it will be attributable to artifacts in the analog front end. The 501As in the lab show the same offsets that vary somewhat between Besides, if you are concerned with levels to femtoamps and picovolts with this item you might be using the wrong meter. There are far better unit out here that exceed a 4-1/2 digit multimeter. I find the Fluke 8588A 8-1/2 digit meter suitable for applications such as this. Greg |
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Re: not a tek but philips
On Tue, Apr 19, 2022 at 12:10 PM, Heinz-Peter Deutsch wrote:
ElectroTanya is free. It's been up for a long time (relative to the age of the Internet.) The indexing is not always that good. (Sometimes searches turn up mis-labeled manuals, or parts of manuals. I know some of these kinds of sites look suspiciously 'busy'... with lots of 'clicky' things. And, I'm not saying one should click on 'clicky' things... but, everything on the Web is not risk free. Someday the Internet will be so safe that only the government, and Elon, will be able to make money from it. -- Roy Thistle |
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Re: SG503 - low output frequency on 100-250MHz range?
Metal film resisters do have an inductive property to them and act strange at higher frequencies. And are helical cut so from a construction standpoint would be a resister with inductive properties or a small inductor with resistive properties. Carbon film as drifty as it is, Is still highly desired at high frequencies. 200+Mhz I personally would consider mid to high frequency range of things.
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Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jared Cabot via groups.io Sent: Wednesday, April 20, 2022 10:23 AM To: [email protected] Subject: Re: [TekScopes] SG503 - low output frequency on 100-250MHz range? Today I removed the variable capacitor, disassembled it, cleaned it (including ultrasonic cleaner with isopropyl alcohol to remove all the old flux etc) then reassembled with new grease and a tiny bit of deoxit on the sliding contacts. Testing it out, it feels really smooth now :) BUT, my 100-250MHz range is still outputting 87.2-230MHz, it now stays leveled until 230MHz, but after that it unlevels every time (I can adjust LR40 to get me up to 233MHz maximum). I just thought actually, I replaced some drifted carbon composite resistors around the place with metal film. Could they be having an effect if they are slightly inductive or capacitive? |
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Re: Thinking of Jumping into a Spectrum Analyzer
A couple other options to possibly consider:
The Tektronix AM700. A real, dedicated audio test system. Anything with XLR connectors says "audio" and lets you interface balanced or un-balanced hi-Z or lo-Z devices. It has a user interface that's a combination of touch and front panel controls. Working ones sell for real money but there's a dead fixer-upper on the auction site. Full manuals with schematics are available. Probably a capacitor issue. I have one and had to completely re-cap it. A Tektronix VM700T with option 40 audio. With the demise of NTSC, these go for cheap. It's a heavy unit but could be a lot of function for a few bucks. "The VM700T Option 40 Audio Measurement Set expands the power of the VM700T Video Measurement Set to include comprehensive audio measurement capabilities. This option incorporates both automated and manual audio measurements, audio spectral analysis, multitone analysis and stereo audio monitoring..." |
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Re: SG503 - low output frequency on 100-250MHz range?
Today I removed the variable capacitor, disassembled it, cleaned it (including ultrasonic cleaner with isopropyl alcohol to remove all the old flux etc) then reassembled with new grease and a tiny bit of deoxit on the sliding contacts.
Testing it out, it feels really smooth now :) BUT, my 100-250MHz range is still outputting 87.2-230MHz, it now stays leveled until 230MHz, but after that it unlevels every time (I can adjust LR40 to get me up to 233MHz maximum). I just thought actually, I replaced some drifted carbon composite resistors around the place with metal film. Could they be having an effect if they are slightly inductive or capacitive? |
DaveH52
Jared Cabot
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