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Re: Need Help Troubleshooting Tektronix PS280
daven9ooq
Hi, John, Wow you really want to make me work hard , but I understand your logic, Which is the proper procedures to troubleshoot any piece of equipment.?
This should help any one of us who are new or less experienced. To try to answer some of your questions Yes I did print out the schematic? and I even printed out datasheets for all the opamps, but no I did not enlarge it, I have a magnifying lamp ,I dont have any way to print anything larger than 8.5x11 . Yes I did check the transformer, that is to say I? measured ac voltage at the secondary for the 2 variable supplys,? to be honest I did not write it down on the schematic, and I dont recall what it was exactly, For the sake of thouralness I will go back and do this over, but if you read my earlier posts , what is the point of doing steps 1-5 if I measure + and - 15volts at both references?? This is a multi tap transformer with no less than 10 secondaries, all terminated with connectors , I'm using pieces of stiff wire or paperclips to get into the connectors and jumpers to my probes, and there are 7 full wave bridge rectifiers? I did look at the waveform of the two variable supplies ,they both looked good,? I did not check the ripple as I just finished a full recap! Back to the transformer, the first thing I do when opening up a piece of equipment is do a very thoural visual inspection of each component using all senses, sight sound and smell in doing this I did not find anything unusual , I noted everything look quite clean? there was very little dust which suggests light usage. The Serial #is TW50125 which I gather is an early ,late version , going by appearance and the photos on the TekWiki site? round push button and internal heatsink, I conclude a early late revision and one piece main board, as opposed to the schematic on Tekwiki that has a seperate fuse board. ?John I am prepared to proceed With Troubleshooting in this manner if your willing to see me through untill I get it working, If? I can streach it out at my own pace, and with the understanding that 1 I am handicapped ,working one handed? from a stroke and my short term memory took a hit with a burst anurism, so as to say I work slow and my short-term memory is falty. I haveCML Leukemia but after 8years of Gleevec a truly miracle drug, I'm happy to report my Leukemia has disappeared , undetectable , maybe just to small to detect or just hiding , but at least for the last 3 or 4years undetectable! I am able to walk and drive , pretty much independent. So doing exceptionally well considering what I been through, I owe it to my hobby in electronics and amateur radio and my Wife Esther a Filipina I meet and married after my first stroke due to an elergic reaction to Cartizem a family of blood pressure medication, just one pill one time nearly killed me! N9OOQ is my call sign. I usually dont? work on my hobby when Esther is off work, she will be off the next 8days due to my stepson immigrating to the U.S. From the Philippines, so we have a lot of activity planned for him , Mark is 35 ,Esther hasn't seen him in the Flesh for nearly 20 years, So I will be busy for about the next week or so, I will be reading the mail though, and may even get some brief time troubleshooting, I was trying to get done before Marks home comming! I have the Job of Chauffeuring everyone around and teaching Mark 35 to drive, so yeah I up for Challenges!Should make a good learning experience for most! Thanks John and everyone for your understanding and patients! Best Regards to all!73's?Daven9ooq |
Re: Tek 576 Curve Tracer HV Transformer winding
Hi, my 576:
Transformer core size 50mm 13mm 31mm Inductance 1khz 1mA 2-3 305uH 22R 7-8 918mH 85K Rubber potted /g/TekScopes/album?id=94656 I have the idea to use a pre made transformer and rewind it, reusing the HV coil. Something like this: But I think that¡¯s is a little bit smaller. Regards Miguel -----Mensaje original----- De: [email protected] [mailto:[email protected]] En nombre de Ed Breya via Groups.Io Enviado el: mi¨¦rcoles, 28 de agosto de 2019 3:40 Para: [email protected] Asunto: Re: [TekScopes] Tek 576 Curve Tracer HV Transformer winding Has anyone measured the low frequency (like 1 kHz) primary inductance of a normal, OK 576 HV transformer? I looked at the data sheets (at tekwiki) on the part, and none appear to show any inductance value. I've been pondering possible alternate solutions to the "bad epoxy" transformer problem. The first is a drop-in two-transformer (one to provide the HF power and +225V, the other to make the HV) scheme, to sub for only the original transformer. The other is a replacement for the HV supply section, basically an independent SMPS that can run from the +100V supply, like the original. My 576s are good, with the newer "black" transformers, but all the recent talk got me interested, and revisiting ideas I've been thinking about over the years. In case anything major should happen to the HV transformer or HV guts, I'd like to be ready to fix it, without resorting to rewinding the HV transformer. In either scenario, the plan is to use a "modern," off-shelf type small HF-HV transformer to provide the 4 kV. I'm picturing the little kind commonly used in Royer converters for LCD CCFL backlighting. I have many dozens of all sorts of these things. I'm sure that some types are just right for this particular setup, but would need a lot of experimenting to figure out. Anyway, if anyone has more info on the original transformer, please let me know. This is a low priority project, but I like to think about it. If I ever get around to actually making it, I'll put up the how-to info. Ed |
Re: Tektronix 585A Voltage Diagnoses Problem Success!
On Tue, Aug 27, 2019 at 11:59 PM, <randolphbeebe@...> wrote:
Hi Randy, Well, that was an easy repair after all! I started reading reading your measurements results before I saw this last message. This last message is in a new thread for some reason. My conclusion was indeed that the LV supply was still in regulation and the voltage across V609 was the culprit, way too high. The ratios 182/150 and 107.4/85 are almost the same. Though the grids of V624 differed more than I thought, the anode voltage (about 0 V) was clearly not near the end of the possible range. [You probably did not measure differentially between the grids, and even a 10 Mohm DMM input has some influence when you need the difference between large DC values.] BTW You also reported pin 4 of V634, which is the 6.3 V AC heater supply. I don't know what your DMM (-2.4 V ?) does with this, but just ignore it. I think you were mislead here by resistance measurements. The "+20 V" is also loaded by the K600 coil. It's clear that the "+20 V" is present, otherwise the time delay relay would not switch in. You might check the regulated +12.6 V DC output if you still don't trust it. I am much more reluctant to replace components! Albert |
Re: Plug for 7CT1N captive lead?
To close this:
(a) Thanks Dennis (b) the heatshrink plus some other support for the solder joint is absolutely essential for the soldered-pin-only solution, otherwise the joint is just to weak and will break within days, as I confidently expect this one to by the time Dennis' lead arrives. EJP |
577 Main board capacitor replacement advise
I plan to replace some electrolytic and tantalum capacitors on the main board of the 577.
I notice there are 2 electrolytic capacitors C391 C393, 15uF 100V, would this film capacitor work () as a drop in replacement? I notice 2 tiny electrolytic capacitors, C218 C215, I didn't know they made these so small, I will replace them with these tantalum capacitors () And finally C268 and C265, these look like a tantalum capacitors but they are red on the tip, purple in the middle, and yellow on the bottom, based on my serial number 092694 D1 storage I believe these should be 0.47uF 35V, I will be replacing these with tantalum capacitors () Any comments or advise on these capacitor selections? |
Re: Tek 576 Curve Tracer HV Transformer winding
Has anyone measured the low frequency (like 1 kHz) primary inductance of a normal, OK 576 HV transformer? I looked at the data sheets (at tekwiki) on the part, and none appear to show any inductance value. I've been pondering possible alternate solutions to the "bad epoxy" transformer problem. The first is a drop-in two-transformer (one to provide the HF power and +225V, the other to make the HV) scheme, to sub for only the original transformer. The other is a replacement for the HV supply section, basically an independent SMPS that can run from the +100V supply, like the original.
My 576s are good, with the newer "black" transformers, but all the recent talk got me interested, and revisiting ideas I've been thinking about over the years. In case anything major should happen to the HV transformer or HV guts, I'd like to be ready to fix it, without resorting to rewinding the HV transformer. In either scenario, the plan is to use a "modern," off-shelf type small HF-HV transformer to provide the 4 kV. I'm picturing the little kind commonly used in Royer converters for LCD CCFL backlighting. I have many dozens of all sorts of these things. I'm sure that some types are just right for this particular setup, but would need a lot of experimenting to figure out. Anyway, if anyone has more info on the original transformer, please let me know. This is a low priority project, but I like to think about it. If I ever get around to actually making it, I'll put up the how-to info. Ed |
Re: Tektronix 585A Voltage Diagnoses Problem Success!
Albert,
I re-read your post about the V609 voltage reference tube and it occurred to me that I could not test the 5651 tube with my tube tester so I just put it back in. However, I had another one my stash and I just replaced it. Now all the voltages came inline perfectly. I now have a perfectly working 585A! Next I will attempt to calibrate it. Cheers, Randy |
Re: Tektronix 585A Voltage Diagnoses Problem edited
Albert,
I am not sure if this is related but I seem to get a short between Ground and the positive terminals of C790-791-792 ( All have been replaced now) of the regulated heater supply (Upper Left portion of the LV Power Supply Schematic). It appears to be isolated between the Emitter of Q797 and Diode 793 and Diode 792 somewhere. Is this normal? Thanks |
Re: Tektronix 585A Voltage Diagnoses Problem edited
Albert,
I checked the voltages and here is what I measured after a 10 minute warm up; Tube Pin Voltage V609 7 -107.4 V624 6 +1.5 7 -107.6 2 -104.0 V634 6 -38.0 7 and 2 -87.0 1 -87.1 4 -2.4 V627 9 +69.0 V637 same V647 same As you mentioned in you previous reply I found that pins 6 and 7 of V624 vary widely. I changed that 12AX7 with no change. Thanks Again, Randy |
Re: Need Help Troubleshooting Tektronix PS280
daven9ooq
Hi John, Yes Thanks this is the kind of help I need , Yes did check the secondaries voltage wise but not under load,? ?I'm rather busy lately and I have to confess I have not done the math to calculate the resistance I need for a 2amp load.?I dought I have the resistors in the wattage I need,? I do have a 2ohm 100 watt resistor handy. I have a bunch of others on order from china expect them in about a week.?
I'm expecting my stepson? ?to immigrate to the U.S. From the Philippines Thursday the 28th . so lots to prepare and hard to predict how much time I will have in the future.??Hopefully next week I will have more time? but working one handed due to strokes , so it will have to be spread out over days if not weeks! But yes this is the correct methods? for troubleshooting taking nothing for granted. ?Yes I did print out the schematic but did not page them togeather as I should have. I do see the +and - 15volts comming of the references on both sides , there are 4 fullwave bridge rectifiers I have checked both variable sides I recapped all filters , Im forced to kind of short cut? testing everything, due to time constraints and lack of a variable load. I do very much appreciate your methods though and will go back ,when time permits? and report the results so others can learn? from this , This is what this group is for.? Many Thanks John!Daven9ooq |
Re: Need Help Troubleshooting Tektronix PS280
daven9ooq
Thanks for the comment I Think we established the PS280 was not made by Tektronix although it carries their? name, and was out sourced toGoodwill industries.
I really could use some help troubleshooting this supply? I did a full recap on the 2 -0-30volt supplies, they do go down to 0 volts and in fact will go negative if you adjust it so, At present I am getting about 15 volts max. on the main side and little to nothing on the slave side, waiting for load resistors to come, maybe about a week more,? There is a Theroy of operation in the manual one Tekwiki although the manual is for a different? version, all versions seem to use the same circuitry , just different construction and appearance. I'm quite busy at the moment and in the near future, I really could use to get this off my bench quick but could use help with Ideas on what to check and how to proceed. Many thanks in advance! Daven9ooq. |
Modeling The Bipolar Transistor - Ian Getreu - third printing 1979
Phillip Potter
Hi all,
Well, I bought this book thinking I could study it to learn more about curve tracing (I have a 575), only to find that it is WAY ABOVE MY PAY GRADE! I would like to get this into the hands of someone who would appreciate it. Contact me off list if you are interested in it. Thanks. Phil_in_CA |
Re: 2247A PSU Troubleshooting
peter bunge
Stand on a rubber mat and keep one hand in your pocket. Know where the
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other hand is at all times. Avoid live testing if possible, clip the leads on before powering. Use a shorting stick. Tag switches if high power. Work with someone you trust. Common sense. On Tue, Aug 27, 2019 at 9:52 AM Chuck Harris <cfharris@...> wrote:
You imagine that you are protecting yourself, but your |
Re: 2247A PSU Troubleshooting
And, come to think of it, latex gloves probably generate electrostatic discharge.? Sensitive components like CMOS logic could be damaged.? I would avoid any kind of gloves while working on electronics.? Maybe ESD-safe finger cots, but I have never seen the need for those.Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Chuck Harris <cfharris@...> Date: 8/27/19 6:52 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 2247A PSU Troubleshooting You imagine that you are protecting yourself, but yourprotection efforts remind me of the comic routines wheresome hapless character gets dressed in a hazardous wastesuit, complete with a hockey mask, ski goggles, tongs, andoven mitts all to take a soiled diaper out to the trash.A linesman's glove so completely eliminates any dexterity,that safe manipulation of something as tiny as an anodelead is awkward at best... all to protect you from a zapthat is no more potent than a static zap to a doorknob inthe winter.Latex surgeon's gloves during electronic work, is a fool'sfolly beyond belief.? The glove, by virtue of its sealednature will capture your hands sweat, covering them witha highly conductive layer that is capable of reducing yourskin's protective resistance to a point where even 24V couldconduct enough current into your heart to be fatal.Further, DC rarely if ever can cause a heart to enter a fatalrhythm.? It will, at most, skip a beat, and continue on inits normal rhythm.Stop trying to improvise safety, you lack the experience tobe able to recognize safe and unsafe methods.? Instead, pleasestudy some legitimate sources, and learn about HV safety, asit pertains to TV and radio repair.? If you can't, please,please do your friends and family a favor, and take up stampcollecting, or golf.-Chuck Harrisnielsentelecom@... wrote:> Chuck,> > The only use of the linesman glove was to put the HT anode lead somewhere that would hold it from moving, and to keep it away from me. I never implied to wear them while working in electronics, they also have a leather shell glove to protect the linesman glove from damage.> > But I do use latex gloves when doing this work, I'm not relying on them to protect me, but rather to add a weak safety net, since I have them lying around, they improve grip, and add a decent layer of uncertified protection, but they tear easily.> > This reply is a little dated I know, haven't been following the thread for awhile.> > NielsenTelecom
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Re: 2247A PSU Troubleshooting
Chuck Harris
You imagine that you are protecting yourself, but your
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protection efforts remind me of the comic routines where some hapless character gets dressed in a hazardous waste suit, complete with a hockey mask, ski goggles, tongs, and oven mitts all to take a soiled diaper out to the trash. A linesman's glove so completely eliminates any dexterity, that safe manipulation of something as tiny as an anode lead is awkward at best... all to protect you from a zap that is no more potent than a static zap to a doorknob in the winter. Latex surgeon's gloves during electronic work, is a fool's folly beyond belief. The glove, by virtue of its sealed nature will capture your hands sweat, covering them with a highly conductive layer that is capable of reducing your skin's protective resistance to a point where even 24V could conduct enough current into your heart to be fatal. Further, DC rarely if ever can cause a heart to enter a fatal rhythm. It will, at most, skip a beat, and continue on in its normal rhythm. Stop trying to improvise safety, you lack the experience to be able to recognize safe and unsafe methods. Instead, please study some legitimate sources, and learn about HV safety, as it pertains to TV and radio repair. If you can't, please, please do your friends and family a favor, and take up stamp collecting, or golf. -Chuck Harris nielsentelecom@... wrote: Chuck, |
Concordosky curve tracer 576
-----Mensaje original----- De: [email protected] [mailto:[email protected]] En nombre de Miguel Work Enviado el: domingo, 25 de agosto de 2019 20:53 Para: [email protected] Asunto: Re: [TekScopes] Tek 576 Curve Tracer HV Transformer winding Hi Peter, Mine moves exactly one division too Vert Offset Horiz Pol Max Peak Series Resistor Left/Right 0.5mA 0 50v +NPN 1500v 3k (220W) off (no component) Turn the variable collector supply so the trace reaches to 10 div. What happens to the left end of the trace? Mine moves over 1 div. -----Mensaje original----- De: [email protected] [mailto:[email protected]] En nombre de peter bunge Enviado el: domingo, 25 de agosto de 2019 18:34 Para: [email protected] Asunto: Re: [TekScopes] Tek 576 Curve Tracer HV Transformer winding This may be of interest to the Tek Group so I am going on line again. I got my 576 working again. It was one of the push-on connectors on the top left board. I have had trouble with those long ago on a 465 scope. I just ran an insulated rod along them until the trace re-appeared. I will have to go around the entire curve tracer with a pair of plyers and pull off and push on each one. It solves many problems. I would appreciate you doing a couple of tests: Vert Offset Horiz Pol Max Peak Series Resistor Left/Right 0.5mA 0 50v +NPN 1500v 3k (220W) off (no component) Turn the variable collector supply so the trace reaches to 10 div. What happens to the left end of the trace? Mine moves over 1 div. Reset to the following with a 2N3565 (high gain NPN) 2uA 0 0.1v +NPN 10v 30 ohm Step Gen, 0.05 uA, Zero, Steps, Rep Norm, 3 steps turn the collector to full scale as shown (1 volt). The first trace is not really dim, it is the camera. Do you see a similar set of curves. I am most interested in the looping. [image: 2N3565.jpg] On Sat, Aug 24, 2019 at 3:11 PM Miguel Work <harrimansat@...> wrote:
I have two 576, if you told me which test you need to compare, I will |
Re: Tek 561 HV transformer
Roy Morgan
Hi,
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If your 561 HV transformer is acting badly, try heating it with a lamp reflector for a day or so to get the moisture out of it. A college instructor whose lab has a number of 561¡¯s did this each summer to get the scopes to run right again for the fall classes. Roy sends. On Aug 26, 2019, at 11:48 PM, atwood.1@... wrote: |
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