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Bringing up a 555
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faustian.spirit
Hi all,
recently got my hands on a 555 System in unknown working condition (probably been stored 10+ years). Can anybody here give me good hints from experience on bringing this up without risking unnecessary damage? Especially, can the PSU (these things are [expletive deleted] heavy!) be bench-tested separately, or will there be unexpected effects (underload)? I am aware that I will probably need to take out and reform all the lytics.... What happens if I operate the unit with only one vertical, or only one horizontal, or one only each...? Don't want to switch on and fry everything in one session :) I can work on the verticals with the 545B (doing so at the moment... an extender cable would help with the Type D, it would.... I'd rather avoid turning the scope on its side... oh well...)... BTW, does anyone of the history buffs here know why a Type L has such a big honking filter cap on board? Oh, and BAMA does not have any 21A/22A schematics... oh well again... And finally... what ARE the differences between different serial numbers of the PSU? It is often claimed they are not interchangeable... why? Cheers, Andy |
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Hi Andy,
I will try to help you with some of your questions: Especially, can the PSU be bench-tested separately, or will therebe unexpected effects (underload)? You will have an unexpected effect - it won't work. The AC for the power supply, as well as its filament supply, comes from the 555. I am aware that I will probably need to take out and reform all the lytics....No reason to do this, these do not give a problem. one horizontal, or one only each...? Don't want to switch on and fryShould be no problem, one beam will be weird but no damage. Oh, and BAMA does not have any 21A/22A schematics... oh wellagain... These are in the 555 manual. Get the correct manual. Different serial number ranges used different AC wiring. Best to use the PSU that came with the scope originally. Same with the 551. Larry Christopher www.theoscilloscopestore.com Home of The Fridge! |
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faustian.spirit
--- In TekScopes@..., "Larry Christopher" <tektronix@...>
wrote: You mean, the heater transformer in the 555 case feeds back to... reading the PSU/Scope interface schematics already cost me a pack of paracetamol... guess I'll need another pack... and an A3 printer... I realize Tek also made some :) Wonder whether it makes the PSU behave if I tell it "there is this fine lass I know and like who wants a guitar amplifier..." :) Are they different except in quality from Radio/TV lytics (which I'd only kickstart into operation after 10 years rest with a pair of goggles)? The 555 Manual on BAMA is for the pre-7000 serials.... no -A timebases...one Luckily I have reason to think the person who gave it to me has the original manuals and just forgot to include them.... Different serial number ranges used different AC wiring. Best to use |
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Stan and Patricia Griffiths
Hi Andy,
Others may call me careless in my approach to firing up an old 555, but I would just plug it in and turn it on. It is pretty well fused and I would not expect any to blow anyway. You can not test the power supply disconnected from the scope and your reason is correct. It must have a proper load on it and, yes, you will need all plugins in place to put a proper load on the power supply. Both timebases and both verticals. On old Tek scopes, I never bother to reform the electrolytics. A shorted one is very rare and an open one will show up as too much ripple somewhere. I have never seen a shorted one do serious damage. Over the past 46 years, I have probably turned on more than 1000 of these old scopes. I have lost count but I have at least six or seven 555's in my collection . . . maybe more. I think when originally shipped from the factory, the serial number of the power supply will match the serial number of the mainframe. Sometimes in the field, mainframes and power supplies get swapped around, but I can't remember any serious incompatibility problems, even with mismatched serial numbers. Stan _____ From: TekScopes@... [mailto:TekScopes@...] On Behalf Of faustian.spirit Sent: Friday, December 29, 2006 12:16 PM To: TekScopes@... Subject: [TekScopes] Bringing up a 555 Hi all, recently got my hands on a 555 System in unknown working condition (probably been stored 10+ years). Can anybody here give me good hints from experience on bringing this up without risking unnecessary damage? Especially, can the PSU (these things are [expletive deleted] heavy!) be bench-tested separately, or will there be unexpected effects (underload)? I am aware that I will probably need to take out and reform all the lytics.... What happens if I operate the unit with only one vertical, or only one horizontal, or one only each...? Don't want to switch on and fry everything in one session :) I can work on the verticals with the 545B (doing so at the moment... an extender cable would help with the Type D, it would.... I'd rather avoid turning the scope on its side... oh well...)... BTW, does anyone of the history buffs here know why a Type L has such a big honking filter cap on board? Oh, and BAMA does not have any 21A/22A schematics... oh well again... And finally... what ARE the differences between different serial numbers of the PSU? It is often claimed they are not interchangeable... why? Cheers, Andy |
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faustian.spirit
--- In TekScopes@..., "Stan and Patricia Griffiths"
<w7ni@...> wrote: but I would just plug it in and turn it on. It is pretty well fused and Iwould not expect any to blow anyway.Probably will soon... Visual inspection shows nothing suspicious at least... I could put the L and CA in, but now I feel obliged to at least try to recalibrate or fix the D (was marked "broken" but seems to work except that the gain is too low and the CMRR is lousy... Most of the switch trouble vanished after applying some Tuner 600) ... whoever designed it had money in the plugin extender business I guess :) And something with the idea of operating a 500 series lying on its side strikes me as very odd... same with sawing a hole in the table... Are the connectors needed to make an extender cable as rare as those in the 551/555 PSU cable are said to be? I noted the pitch is different.... will need all plugins in place to put a proper load on the power supply. Bothshorted one is very rare and an open one will show up as too much ripplesomewhere. I have never seen a shorted one do serious damage.these old scopes. I have lost count but I have at least six or seven555's in my collection . . . maybe more. How many blew up? :) of the power supply will match the serial number of the mainframe.Sometimes in the field, mainframes and power supplies get swapped around, but I can'tserial numbers.On Behalf Of faustian.spirit |
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Hi Andy,
I have sent you the 21A/22A manual extract off list. I'm not sure what you mean by the big honking filter cap in the L. It certainly has quite comprehensive decoupling of the B+ to the low level amps which is pretty standard practice. I'm too lazy to get out my L to check, but that's almost certainly what it's for. That quite a high gain wideband amplifier and keeping such devices stable is not a trivial design task! Good luck with your scoposaurus, it's worth the effort Morris --- In TekScopes@..., "faustian.spirit" <faustian.spirit@...> wrote: hints from experience on bringing this up without risking unnecessarydamage? heavy!) be bench-tested separately, or will there be unexpected effectsone horizontal, or one only each...? Don't want to switch on and fryrather avoid turning the scope on its side... oh well...)... BTW, doesanyone of the history buffs here know why a Type L has such a big honkingagain...
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This is not for filtering. The L manual says:
"Low-frequency peaking for the X10 amplifier is provided mainly by C6002A and C6002B in the plate circuits of V5942 and V6042. With their associated resistors, these capacitors form a low-frequency boost network to compensate for the low-frequency attenuation introduced in the cathode circuits, the screen circuits, and the RC coupling network between the Second amplifier and the Second cathode follower. ... the amount of attenuation can be varied with the LOW FREQ. ADJ. control in the grid of V6132." This technique is discussed in detail in "Typical Oscilloscope Circuitry." Larry Christopher --- In TekScopes@..., "morriso2002" <vilgotch@...> wrote: It certainly has quite comprehensive decoupling of the B+ to the lowout my L to check, but that's almost certainly what it's for. Thatquite a high gain wideband amplifier and keeping such devices stable isnot a trivial design task! |
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Stan and Patricia Griffiths
Hi Andy,
You asked about connectors for extender cables. There are three possible extenders you could be talking about: 1) vertical plugin, 2) timebase plugin, 3) power cable from mainframe to power supply. I am sure I have connectors that I can sell you to build extenders for either type of plugin for a couple of dollars per connector. Most of what I have have been salvaged but are still perfectly useable. In the Tektronix Service Center we had an extra long power supply cable that made it much easier to turn the 555 on its side for maintenance. Let me know if you need some connectors to make extenders. You also asked me how many old scopes "blew up" :-) on turn on. No explosions that I can recall, but some came quietly on but did not work completely. Stan _____ From: TekScopes@... [mailto:TekScopes@...] On Behalf Of faustian.spirit Sent: Friday, December 29, 2006 6:38 PM To: TekScopes@... Subject: [TekScopes] Re: Bringing up a 555 --- In TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com, "Stan and Patricia Griffiths" <w7ni@...> wrote: but I would just plug it in and turn it on. It is pretty well fused and Iwould not expect any to blow anyway.Probably will soon... Visual inspection shows nothing suspicious at least... I could put the L and CA in, but now I feel obliged to at least try to recalibrate or fix the D (was marked "broken" but seems to work except that the gain is too low and the CMRR is lousy... Most of the switch trouble vanished after applying some Tuner 600) ... whoever designed it had money in the plugin extender business I guess :) And something with the idea of operating a 500 series lying on its side strikes me as very odd... same with sawing a hole in the table... Are the connectors needed to make an extender cable as rare as those in the 551/555 PSU cable are said to be? I noted the pitch is different.... will need all plugins in place to put a proper load on the power supply. Bothshorted one is very rare and an open one will show up as too much ripplesomewhere. I have never seen a shorted one do serious damage.these old scopes. I have lost count but I have at least six or seven555's in my collection . . . maybe more.How many blew up? :) of the power supply will match the serial number of the mainframe.Sometimes in the field, mainframes and power supplies get swapped around, but I can'tserial numbers. |
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coresta
Hi Stan,
As i see this new thread, i always asked myself about the use of Kalotron in the PSU of the 555 ? What¡¯s the big iron potted case too ? I broke a pair of those PSUs many years ago and those are somewhere in the basement . I never saw the schematic . I have a 551 working that doesnt contain these parts . Ah, happy new year to all of you ! And long life to our old old tubed scopes ;-) Pierre _____ De : TekScopes@... [mailto:TekScopes@...] De la part de Stan and Patricia Griffiths Envoy¨¦ : dimanche 31 d¨¦cembre 2006 03:10 ? : 'faustian.spirit' Cc : TekScopes Objet : RE: [TekScopes] Re: Bringing up a 555 Hi Andy, You asked about connectors for extender cables. There are three possible extenders you could be talking about: 1) vertical plugin, 2) timebase plugin, 3) power cable from mainframe to power supply. I am sure I have connectors that I can sell you to build extenders for either type of plugin for a couple of dollars per connector. Most of what I have have been salvaged but are still perfectly useable. In the Tektronix Service Center we had an extra long power supply cable that made it much easier to turn the 555 on its side for maintenance. Let me know if you need some connectors to make extenders. You also asked me how many old scopes "blew up" :-) on turn on. No explosions that I can recall, but some came quietly on but did not work completely. Stan _____ From: TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com [mailto:TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com] On Behalf Of faustian.spirit Sent: Friday, December 29, 2006 6:38 PM To: TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com Subject: [TekScopes] Re: Bringing up a 555 --- In TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com, "Stan and Patricia Griffiths" <w7ni@...> wrote: but I would just plug it in and turn it on. It is pretty well fused and Iwould not expect any to blow anyway.Probably will soon... Visual inspection shows nothing suspicious at least... I could put the L and CA in, but now I feel obliged to at least try to recalibrate or fix the D (was marked "broken" but seems to work except that the gain is too low and the CMRR is lousy... Most of the switch trouble vanished after applying some Tuner 600) ... whoever designed it had money in the plugin extender business I guess :) And something with the idea of operating a 500 series lying on its side strikes me as very odd... same with sawing a hole in the table... Are the connectors needed to make an extender cable as rare as those in the 551/555 PSU cable are said to be? I noted the pitch is different.... will need all plugins in place to put a proper load on the power supply. Bothshorted one is very rare and an open one will show up as too much ripplesomewhere. I have never seen a shorted one do serious damage.these old scopes. I have lost count but I have at least six or seven555's in my collection . . . maybe more.How many blew up? :) of the power supply will match the serial number of the mainframe.Sometimes in the field, mainframes and power supplies get swapped around, but I can'tserial numbers. [Non-text portions of this message have been removed] |
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Richard Aston
Andy,
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Stan's right. I found a 555 on a dump, full of leaves and dirt. I stripped it down, cleaned all the waterproof bits in the bath, dried it with an airline followed by 3 hours at 60C. When I eventually got it all back together and switched it on, guess what? That's right - worked straight away. It's worth the effort; these are lovely bits of engineering. Richard. Stan and Patricia Griffiths wrote: Hi Andy, |
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The 555 power supply uses that big heavy saturable reactor to
regulate the heater voltages. It relies on a little tube that varies its conductivity according to the temperature of its filament and varies the control current in the reactor, which in turn regulates the heater supply transformers primary voltage. And you are correct, the 551 did not have this arrangement. Bonne Noel. Larry Christopher --- In TekScopes@..., "coresta" <coresta@...> wrote: Kalotron in the PSU of the 555 ? What's the big iron potted case too ?in the basement . I never saw the schematic . |
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Stan and Patricia Griffiths
Hello Pierre,
If I remember right, the big iron potted case contains a device is called a "saturable reactor" (or something like that) and is used to regulate the AC voltage applied to the vertical amplifier tubes. I think this was an attempt to minimize the effects of cathode interface which looks like a spike on the leading edge of a fast-rise square wave. Actually, it is a DECREASE in low frequency gain of the vertical amplifiers. In a scope without regulated filament voltage, cathode interface is always worse at low line voltages which means lower filament voltage and therefore, lower filament temperature. If you observe a fast-rise square wave while you lower the line voltage on a scope with bad cathode interface, the leading edge spike seems to grow over about one minute of time. If you look very carefully, it is actually the trailing edge, or flat portion of the square wave, that is DECREASING in amplitude over time as the filaments cool down. You can verify this by simply plugging in the scope calibrator and watching the gain of the vertical change as the calibrator signal appears to decrease in amplitude. No spike seems to grow on the leading edge because there are no high frequency components in the scope calibrator signal. There is actually a filament voltage adjustment in the 555 power supply and the list of equipment needed to calibrate a 555 includes an iron vane AC voltmeter to accurately set the AC filament voltage. I think the 517 is the only other scope Tek made that has adjustable filament voltage . . . but I could be wrong about this since it has been years since I looked at my 517's. Stan _____ From: TekScopes@... [mailto:TekScopes@...] On Behalf Of coresta Sent: Saturday, December 30, 2006 11:53 PM To: tekscopes@... Subject: RE: [TekScopes] Re: Bringing up a 555 Hi Stan, As i see this new thread, i always asked myself about the use of Kalotron in the PSU of the 555 ? What's the big iron potted case too ? I broke a pair of those PSUs many years ago and those are somewhere in the basement . I never saw the schematic . I have a 551 working that doesnt contain these parts . Ah, happy new year to all of you ! And long life to our old old tubed scopes ;-) Pierre |
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arthurok
you believe the crest factor is so high that a modern true rms multimeter wouldnt do the job?
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an iron vane voltmeter is true rms responding. a chinese engineer told me the best true tms voltmeter for non super accurate measurements is a scope read by a trained eye. the best rms converter i know of is a thermal converter "thermocouple vacuum junction" ----- Original Message -----
From: Stan and Patricia Griffiths To: 'coresta' Cc: TekScopes Sent: Sunday, December 31, 2006 8:28 PM Subject: RE: [TekScopes] Re: Bringing up a 555 Hello Pierre, If I remember right, the big iron potted case contains a device is called a "saturable reactor" (or something like that) and is used to regulate the AC voltage applied to the vertical amplifier tubes. I think this was an attempt to minimize the effects of cathode interface which looks like a spike on the leading edge of a fast-rise square wave. Actually, it is a DECREASE in low frequency gain of the vertical amplifiers. In a scope without regulated filament voltage, cathode interface is always worse at low line voltages which means lower filament voltage and therefore, lower filament temperature. If you observe a fast-rise square wave while you lower the line voltage on a scope with bad cathode interface, the leading edge spike seems to grow over about one minute of time. If you look very carefully, it is actually the trailing edge, or flat portion of the square wave, that is DECREASING in amplitude over time as the filaments cool down. You can verify this by simply plugging in the scope calibrator and watching the gain of the vertical change as the calibrator signal appears to decrease in amplitude. No spike seems to grow on the leading edge because there are no high frequency components in the scope calibrator signal. There is actually a filament voltage adjustment in the 555 power supply and the list of equipment needed to calibrate a 555 includes an iron vane AC voltmeter to accurately set the AC filament voltage. I think the 517 is the only other scope Tek made that has adjustable filament voltage . . . but I could be wrong about this since it has been years since I looked at my 517's. Stan _____ From: TekScopes@... [mailto:TekScopes@...] On Behalf Of coresta Sent: Saturday, December 30, 2006 11:53 PM To: tekscopes@... Subject: RE: [TekScopes] Re: Bringing up a 555 Hi Stan, As i see this new thread, i always asked myself about the use of Kalotron in the PSU of the 555 ? What's the big iron potted case too ? I broke a pair of those PSUs many years ago and those are somewhere in the basement . I never saw the schematic . I have a 551 working that doesnt contain these parts . Ah, happy new year to all of you ! And long life to our old old tubed scopes ;-) Pierre |
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Stan and Patricia Griffiths
Hi Arthur,
It isn't really what I believe that counts here. I was just repeating what Tektronix has written in the service manual for 555 required equipment. I think they specify an Iron vane movement because the saturable reactor distorts the waveform as it regulates the filament voltage. We had iron vane meters (0-10 VAC) specifically to make this adjustment in each Tektronix Service Center and they have been assigned the Tektronix Part Number 067-0514-00 so some engineer at Tek must have thought it was important. That was many years ago and maybe modern true reading rms voltmeters are up to the job today. Stan _____ From: arthurok [mailto:arthurok@...] Sent: Sunday, December 31, 2006 6:36 PM To: 'coresta'; Stan and Patricia Griffiths Cc: TekScopes Subject: Re: [TekScopes] Re: Bringing up a 555 you believe the crest factor is so high that a modern true rms multimeter wouldnt do the job? an iron vane voltmeter is true rms responding. a chinese engineer told me the best true tms voltmeter for non super accurate measurements is a scope read by a trained eye. the best rms converter i know of is a thermal converter "thermocouple vacuum junction" ----- Original Message ----- From: Stan and Patricia <mailto:w7ni@...> Griffiths To: 'coresta' <mailto:coresta@...> Cc: TekScopes <mailto:TekScopes@...> Sent: Sunday, December 31, 2006 8:28 PM Subject: RE: [TekScopes] Re: Bringing up a 555 Hello Pierre, If I remember right, the big iron potted case contains a device is called a "saturable reactor" (or something like that) and is used to regulate the AC voltage applied to the vertical amplifier tubes. I think this was an attempt to minimize the effects of cathode interface which looks like a spike on the leading edge of a fast-rise square wave. Actually, it is a DECREASE in low frequency gain of the vertical amplifiers. In a scope without regulated filament voltage, cathode interface is always worse at low line voltages which means lower filament voltage and therefore, lower filament temperature. If you observe a fast-rise square wave while you lower the line voltage on a scope with bad cathode interface, the leading edge spike seems to grow over about one minute of time. If you look very carefully, it is actually the trailing edge, or flat portion of the square wave, that is DECREASING in amplitude over time as the filaments cool down. You can verify this by simply plugging in the scope calibrator and watching the gain of the vertical change as the calibrator signal appears to decrease in amplitude. No spike seems to grow on the leading edge because there are no high frequency components in the scope calibrator signal. There is actually a filament voltage adjustment in the 555 power supply and the list of equipment needed to calibrate a 555 includes an iron vane AC voltmeter to accurately set the AC filament voltage. I think the 517 is the only other scope Tek made that has adjustable filament voltage . . . but I could be wrong about this since it has been years since I looked at my 517's. Stan _,_._,___ |
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arthurok
iron vane meters are still being manufactured for panel meter applications.
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"simpson electric and other manufactures" they are genuine true rms responding. a simpson 260 multimeter is not true rms responding . most non harmonicaly neutralized constant voltage transformers have distorted outputwaveforms too the note that the output waveform is non sinusoidal is very important sir. i have a tek thm420 scope meter and its very usefull for looking at waveforms to see what they are really like and for checking power supply ripple. mine was an exchange through tek. the one i purchased through ebay was never modified by tek . "safety recall" it replaces a tek 214 scope i had. i like a scope that can measure frequency and voltage accurately on screen. my 7d15 stays in my 7904 next to a 7b92a for most measurements i make. ----- Original Message -----
From: Stan and Patricia Griffiths To: 'arthurok' Cc: TekScopes Sent: Tuesday, January 02, 2007 1:37 AM Subject: RE: [TekScopes] Re: Bringing up a 555 Hi Arthur, It isn't really what I believe that counts here. I was just repeating what Tektronix has written in the service manual for 555 required equipment. I think they specify an Iron vane movement because the saturable reactor distorts the waveform as it regulates the filament voltage. We had iron vane meters (0-10 VAC) specifically to make this adjustment in each Tektronix Service Center and they have been assigned the Tektronix Part Number 067-0514-00 so some engineer at Tek must have thought it was important. That was many years ago and maybe modern true reading rms voltmeters are up to the job today. Stan _____ From: arthurok [mailto:arthurok@...] Sent: Sunday, December 31, 2006 6:36 PM To: 'coresta'; Stan and Patricia Griffiths Cc: TekScopes Subject: Re: [TekScopes] Re: Bringing up a 555 you believe the crest factor is so high that a modern true rms multimeter wouldnt do the job? an iron vane voltmeter is true rms responding. a chinese engineer told me the best true tms voltmeter for non super accurate measurements is a scope read by a trained eye. the best rms converter i know of is a thermal converter "thermocouple vacuum junction" ----- Original Message ----- From: Stan and Patricia <mailto:w7ni@...> Griffiths To: 'coresta' <mailto:coresta@...> Cc: TekScopes <mailto:TekScopes@...> Sent: Sunday, December 31, 2006 8:28 PM Subject: RE: [TekScopes] Re: Bringing up a 555 Hello Pierre, If I remember right, the big iron potted case contains a device is called a "saturable reactor" (or something like that) and is used to regulate the AC voltage applied to the vertical amplifier tubes. I think this was an attempt to minimize the effects of cathode interface which looks like a spike on the leading edge of a fast-rise square wave. Actually, it is a DECREASE in low frequency gain of the vertical amplifiers. In a scope without regulated filament voltage, cathode interface is always worse at low line voltages which means lower filament voltage and therefore, lower filament temperature. If you observe a fast-rise square wave while you lower the line voltage on a scope with bad cathode interface, the leading edge spike seems to grow over about one minute of time. If you look very carefully, it is actually the trailing edge, or flat portion of the square wave, that is DECREASING in amplitude over time as the filaments cool down. You can verify this by simply plugging in the scope calibrator and watching the gain of the vertical change as the calibrator signal appears to decrease in amplitude. No spike seems to grow on the leading edge because there are no high frequency components in the scope calibrator signal. There is actually a filament voltage adjustment in the 555 power supply and the list of equipment needed to calibrate a 555 includes an iron vane AC voltmeter to accurately set the AC filament voltage. I think the 517 is the only other scope Tek made that has adjustable filament voltage . . . but I could be wrong about this since it has been years since I looked at my 517's. Stan _,_._,___ |
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Stefan Trethan
On Tue, 02 Jan 2007 10:13:41 +0100, arthurok <arthurok@...> wrote:
iron vane meters are still being manufactured for panel meter applications. I think their frequency response is somewhat limited (kHz), and of course they are nonlinear and lack sensitivity at the beginning of the travel, but otherwise they are great. I keep several for measuring odd shaped stuff. Compare different meters on odd shaped signals when you get the chance, you'll be surprised how little truth some cheap "true RMS" meters really show. I'm not saying low quality meters are useless, but one must always be aware when the tool is used outside it's capabilities. Anyone using tek multimeters? ST |
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Hi Stan do you have these connectors for sale?
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Thanks --- In TekScopes@..., "Stan and Patricia Griffiths" <w7ni@...> wrote:
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