Theres someone near me that has two of these bad boys with the carts for 500$ each cart included. Thinking about picking up one of them next weekend. They also have a 7000 series scope and a couple of the rack mount versions. I dont NEED a new scope but I know ill want to get up to 1Ghz eventually. Thank you as always for your videos. They have been a great help for me with my Tek gear.
For the 576's make sure they have the black silicone high voltage transformer (late serial numbers) the brown epoxy potted ones have a high leakage current and are all faulty as far as I know. One other quick test is if the CRT is double peaking. Brighter -> dimmer - > brighter this is the result of cathode poisoning both would be terminal failures and make them parts units.
Hi - I finally got it fixed. thanks for all the hints. important on was the isopropyl alcohol to clean the invert button. I was going to start to take 1/2 the boards out to dismantle the invert switch... would have a been a hell of lot of work...but lubricated with Kontact WL and 61 to lubricate the switch. The issue was the 11Kuf 5 cap of the 5V rail - step generator was out. I don't have to be jealous of you no more with my 576 😁 Love you work !
Magnificent look at what it takes to make one of these function. I have 2, one was bought as a ‘parts car’ for the other. At this point, time has taken its toll. Repair is likely beyond the scope of where I personally want to go. 🙁
Great job. Had to recap mine about 10 years ago. Wish I would have known about those adapter boards. I re-stuffed the old cans. Never again ! Don't use it that much anymore since obtaining a tek 370. I still like to use the old 575. Still the most trouble free CT I have ever owned and it is almost as old as I am.
Thanks, I would love to get a 370 something but they are still a bit out of the budget. How is the 370 do I need to worry about surface mount capacitor plague?
@@ZenwizardStudios Greetings. I have never opened up the 370. It was a hamfest buy some years ago ($50 presumed dead). Much to my surprise it worked . This instrument will probably be outside my skills if/when it malfunctions (other than a power supply problem ) A lot of this later generation equipment is so complex. One of my frustrations is that Hp et-al have out sourced their power supplies and do not include documentation in their service manuals. I don't use the 370 that much. Use the 576 ,577 and 575 most often. Wish my basement was bigger !
I got one and have mostly the same issue described in your video. Thank you so much for you you video. This one here, though, the 75V rail is low. And adusting all the way up maxes at 65 Volt. I figured I need to recap all as well. I was hopping not to take apart just to get cap value. With situation at my place, thongs are gone get lost. I would live to get all caps first then take it apart and recap hopefully in 1 weekend. Would you help with cap's values and part number please?
Thank you so much for the heads up on the switches. Mine had the same issue (trace unstable and all over the place). sprayed it with somethng similar and work them for a bit. Now the tace shows. But cannot get it in a dot, specially in DC - & +. It keeps showing in a small zigzagish line. Happen to know where I should start to work on this
Is there any collector voltage present? if it is not going in to dot mode on DC what is your current per div set to? If it is in a VERY low range like 2nA per Div you might be fighting looping capacitance. If so this might be normal.
Hi - for the relays you mention at 7:54. any hints on how to repair/replace them? I got my 576 back together. the inverter button is indeed a nightmare. the trace moves randomly on the screen. when I wiggle the inverter button then the trace stabilizes a bit. turning the horizontal gain button - the one that switches the relays, also stabilizes the trace - looks like the relays contacts are dirty or used Thanks for any hints
I have not yet needed to repair or replace any of the relays yet. However the invert cal zero switch pack is a real soar spot. The switch is dirty and needs cleaning and servicing. The CRT dri9ve signals vert and horizontal go through that switch on the way to the tube. So before anything cleaning the switches.
Unfortunately, at this time I can not. The transformers were made by a member of the Tek scopes group and were a very limited quantity. They went pretty fast when they were available. But if another run is made it would be announced there before anywhere else.
I don't know if you remember after working on this 576 2 years ago... I have a crt trace that is not staying in focus. First it will come up soft and fuzzy and the sharpen and then lose focus again. All voltages are fine CRT 4000V voltage is fine. Wondering,
There are a few things that would cause this. Some are good some are terrible. The worst case scenario would be an internal tube issues where one of the element has broken off internal to the tube. The 576 tube is unique and therefore almost impossible to find as it was used in no other instrument. The better case scenario would be a voltage coming and going or a cold solder joint. Given that the focus comes in this leads me to believe with minimal information that the fault might be a flaky connect that is moving with thermal stress during warn up. It could also be a bad/noisy focus POT however this pot is in the HV path so care is needed. One quick way to check the tube, “Is the tube double peaking?” when the brightness control is swept from min to max does the tube brighten, then dim, then brighten again? If the CRT exhibits this behavior then additional trouble shooting is not needed as the CRT has aged out and is very high hour.
@@ZenwizardStudios Thanks for your reply, seems we have a lot of same equipment. I believe I found the problem. Bothe the Focus and Intensity pots are out of spec. Looking for replacement parts now. Trying Sphere up in Canada.
Great minds think alike then 😊, you also might want to try the vintage Tek museum. Or the Tek mailing list. There should be quite a few 576 parts units out there given the HV transformer and tube issues. Before putting too much work in to this 576 does it have the black HV transformer? If it has the brown epoxy HV transformer it is a guaranteed fault if not already in the near future.
I went with high hour long life 105 degree C Nichicon's I think the 576 has a linier supply so it is rather gentle on the capacitors it is not slamming them like a switch mode supply does. Also non of the caps in the rear of the unit are involved in the collector supply circuits. Those are just the power rails for the unit not the power for the device under test.
The 5V, +12.5, and 100V rails use 3 amp rated diodes. I was wondering what the ripple current rating was for the Nichicon’s you used on these rails. I also checked C188 15uF 100V +50-10% and C18 15uF 100V +50-10% electrolytics (located behind the step amplitude selector switch) and found one bad, replaced both. I found one of the collector supply electronlytics bad (or at least marginal) and replaced it. The collector supply caps are hard to get and difficult to replace even after accessing them. I am relieved that most of them tested ok. I also replaced the C300 Oil filled cap as it tested really bad.
Hello. Thanks for the great videos. I'm working on repair of a Tek 576 and have a intermittent and sticky INVERT button slide switch. I tried cleaning with the pro electronics cleaner but it is still sticky. I also tried spraying in Isopropyl alcohol with no luck. I now have the board with switch removed and planning to teardown the slide switch and an looking for a replacement grease. Any recommendations? I've heard Vaseline. Thanks
Metalbender22, I would not use Vaseline. I am not sure of its conductive or insulating property's. I will check that. In a switch or a contact you need a conductive lubricant with a good dielectric strength. conductive enough to be invisible to contact closure. Yet NOT conductive enough to short out the entire switch block. Shoot me an E-mail and I will have some more information.
@Zenwizard Studios I also found the internet reference on Vaseline as a poor electrical device. I ended up using Dielectric grease. On page 4-29 of the Tek 576 manual, I removed the Display Switching circuit board. I unplugged the two relays K520 and K620 from their socket and slid out the switch cores from all three pushbutton switches. I then just submerged the lower half in simple green in an ultrasonic cleaner for 4 min. The hardened grease was nicely removed from the inside contacts and the spring contacts. I post cleaned with CRC 05103 QD Electronic Cleaner. To repopulate the switch cores I took the long plastic rod with slots on either side and manually added each spring clip to the slots then partially slid into a reverse packing tape rolled tube until all contacts were contained to the core. It then greased and pushed the tube contents back into the still soldered down switch housing. The sticky side of the packing tape was outward making for a smooth inside of the size I needed to hold the clips. With this process I did not need to unsolder and resolder the pushbuttons making sure they were in alignment to each other. Recently, I saw a 576 at a Purdue University salvage sale for $175 along with a Tektronix 7403N scope for $10. I was inspired to pick up one of these machines by your videos. Thank you for your 576 video series which has been great in understanding this hardware. Kevin
FYI, You can do the calibration with resistors. The Alignment Fixture is nice, but not essential. The newer -01 Service manual provides an alternate process.
@@ZenwizardStudios How would you compare the two processes? I am not fortunate to have access to the Alignment fixture, so the -01 manual revelation was a welcome discovery. I just was able to round up a full set of "precision resistors", I will check out your 2nd video as well. Glad to know that you have a video on that alignment process. Thanks for the reply and the excellent content.
@Michael Lynch, Essentially the process is the same. All that is in the calibration fixture is switches and resisters/capacitors to rout the signals and loads. If I remember correct when I did mine getting some of the precision capacitors was an issue. They were EXPENSIVE for the parts that we speced. So it makes for a faster calibration but not necessarily a better one. Tek did not make a fixture for the 577 so that is done all with resisters. If I remember correctly there was 1 step where I used the calibration fixture cause the -01 was not clear what to do was for doing some of the step generator loads. This also might have been because I was lacking a good enough standard in the lab. I am also planning on adding some good precision LCR meters to the lab to help with this in the future. But those are up there in cost so it will be an in time thing. I think total there are 7 videos between the 576 and 577 units. I fell down the rabbit hole hard.
It looks like it should. From the documentation T850 is the problem unit the -3 version started in serial number 24xxxx also it looks like you have up updated T300 as well that started in 326320. My unit is actually sloe in serial number 328108 had the good one. If you see black under the HV cover you are good if it is brown there will be issues.
Need your advice... i need to ship the unit to Europe, I will take it with me on the plane from PHX to Brussels.. but I need to reduce the weight from 80 pounds to under 70 pounds (packed) I was thinking of removing the block 1.6KV transformer - looks quite easy: 4 screws and a dozen cables to cut off - any thoughts? now I am wondering what I got myself into 😒
First off check the tube, If that does not work look for another unit the 576 tube is unique and incredibly difficult to find even in the USA in Europe they will be even more impossible. However I have good news as well as bad news. The good news is removing the collector supply will reduce the weight significantly. The bulk of the weight in this unit is the power transformer, the collector supply transformer, and housing on the frame. The collector supply CAN be removed with a few screws and a could of cables. The only snag here is the coupling for the collector supply control will need to be disconnected and realigned at the destination. The AC/DC/DC+- control if I recall correctly will not have to be removed as that is a plug. Take EXTREME care then packing the collector supply. The load resisters will be in there and they are a ceramic power resister that will not be easily replaceable. They should be fine but are sensitive to physical impacts being ceramic.
I do remember when I had to recap one of those supplies that a soldering iron and a wire cutter was NOT needed. However a hex key and screwdriver was. The good news is there were designed to be serviceable. Unlike the cap stack those are kind of awful to get to.
@@ZenwizardStudios The 576 has arrived... has the new HV supply. I will now remove the black transformer - i loosened the bolts a bit and looks like the transformer will drop out. hope this gets me under the 70 lbs, including the packaging, to fly it over with me :) i took not check the tube - but the lights on the read out module are very dim so I suspect a power supply issue will keep you updated
Hey there, great vid! I don't see it so I thought i'd ask, did you ever upload the calibration video? I've got a 576 that I'm about to bring back to life. I'm going to start searching for a calibration fixture but it seems like that's a tough find. Would love to get some sense of the process. FYI, my device has the good transformer and is in really good condition, no cracks in any of the buttons and the tube is really bright. It does have a trace that bounces all over the place but does, at times, settle down and hold a spot until I mess with it at all. Hopefully switches and not capacitors, lol. Thanks again for the first vid, it was very helpful. Andy
Hey Andy, I have bad news and some good news. The bad news is the cal fixture. They tend to be rare but when they do come up they tend to be $1000 + on the secondary market. Now the worst news. You need to check in the calibrator to make sure it is in spec befor you use it to cal a 576. For that you need a precise DMM. I think a Keithly 6500 will do it a Keithly 7510 Will most likely do it. And an Keysight 3458A should most deffinatly do it. Being 6.5 digit 7.5 digit and 8.5 digit respectively and priced accordingly. You must read some pretty low value resisters accurately. Which gets me in to the good news. All that is in the calibration fixture is some precision resisters (low tolerance) for loads and some precision capacitors again low tolerance. I have not done a video on it yet but if the trace is jumping around when you are moving the current/div switch The amplifier DC balance is off and needs to be adjusted. I have a 577 that I had to fight for HOURS to get the cal right. It ended up I needed to cal the 177 before I did the 577 the DC balance was messing with the amplifier alignment. Now for the good news: In the later service manual there is an alternate calibration procedure. This procedure specs out the load resisters and the load capacitors needed for the calibration. Tolerances are TIGHT ¼% tight. I found it was cheaper to buy a block of 10 or more 1% resisters and select from them the ones that were in the tolerance needed especially case you need some high wattage resisters. Up to 10 Watts if I remember correctly. So you need a way to measure low resistances with accuracy. So with the right loads you can do it without the cal fixture. Take care in the 576 there are some extreme voltages. But I am glad you found one with a good tube and transformer! Zen
@@ZenwizardStudios Yeah, the cal fixture pricing isn't a surprise, lol. I'd probably pick one up if I could figuring I'd play with it for a while and could always sell it again down the road but I'm going to want to cal this device before I find one I suspect. I did fine a company that says they rent one. I asked for a quote but haven't gotten it yet. I think the best DM I have in that regard is a Fluke 8846A, I don't remember the exact specs, I'll have to check. If not, I'll have to accelerate my search for an 8.5 digit. Do you have a link to the alternate cal procedure? I have two physical copies of the manual and the digital one floating around online but none of those has that in it. Yeah, I'm fairly comfortable with the voltage issues but I do have one question. Normally, I'm pretty careful about using a discharge device on the high voltage caps before I do anything in a device but with this one, they appear to be unaccessible without some disassembly. What is your experience with their discharge time and / or, how are you dealing with that? Thanks again for the video, and the help here. I really enjoy your videos and am looking forward to watching the rest of them as I have time. Andy
One more quick question. You mentioned using straight IPA to clean the switches. Do you not use Deoxit or something like it in general or is there something about this unit that caused you to not use it?
Andy, You do NOT need an 8.5 digit meter of more importance is ohms accuracy at very low ranges. Something the 6500 excels at. You will also want a set of kelvin sense leads If memory serves you need something like 1 Ohm at 10 Watts for one of the ranges. This is somewhat tricky to measure accurately given the low resistance value. I have a 6500 in the lab and that is currently my highest accuracy. I do not have an 8846 but I do have a 8840 in the fluke I can check the resisters against the 6500. The kelvin leads I ended up with were www.digikey.com/en/products/detail/pomona-electronics/6730/603918 I have no complaints so far. 4 wire measurement is needed at the lower resistance level the lead resistance will greatly influence a 1 Ohm resister especially when accuracy needed is ¼%. In terms of the power supply the real danger here is the collector supply just the test terminals can be lethal 1500 Vdc at 220 Watts. Depending on the setting that can be exposed at the front panel under normal operation, And this unit has 2 power supplies the main power supply and the collector supply these are isolated from each other and have different sets of storage caps. Also there is no way to disconnect the 1500 V collector supply internally. It is ac to variac (collector supply) right into the transformer in the bottom. Any time the unit is on treat that as live and take care. In terms of the IPA. The switches on this example were not that bad really just noisy. In this case IPA and some lubricant was all that was needed. My processes and procedures are always being improved and fine tuned. I currently do not have enough practical experience with de-oxit to way in one way or another. Though my service manual for my DC voltage standard calls for Shield it. To maintain some pretty sensitive switch contacts for a precision voltage divider. As with anything test for reactivity for anything you are using in a non-critical area. You do not want to dissolve the plastic on an unobtanium control. Thanks for the comment about the videos. I will keep making videos as long as people are finding the information useful and helpful. Zen
Hi Rollin and welcome, The boards are open hardware from Oshpark. Here is a link they are not the cheapest on the planet but high quality with gold plating. You will need to file down some sharp tags from manufacturing but a small files makes quick work. If i remember right they are in lots of 3. oshpark.com/shared_projects/hpUFRhHC Let me know if there is anything you would like to see worked on and I will see what I can make happen.
There is really only 2 sticking points with this that are a “terminal” failure with no parts available. One is the high voltage transformer (under the cover in the HV supply left side of unit.) The other is the tube its self. Unfortunately these are UNIQUE parts to the 576 and were used no where else in the tek line up of equipment. The transformer you want to have is the one with the black silicone potting insultation. The brown epoxy insulation there seems to be a thermal issue with leakage current. In mine when I did a burn in test of the power supply the unit oscillated. The -75 volt rail would collapse and the unit would go in to over current protect. There was some one who commissioned a transformer recently but the supply has dried up from that run. The tube is also unique and used no where else. There are 2 styles -00 -01 and -05. All are pretty much the same tube the -00 has a slightly different graticule. If the tube is bright and transformer is good your unit should be mostly trouble free. I have a very early example of this one that needed and extensive power supply rebuild. If there is sprauge caps on the rectifier board I advise changing them. Some of mine were 113 Ohms ESR which is AWFUL should be in the 0.XXX not 100.XXX rebuild the supply actually dropped the power consumption by 10 Watts so it was needed. Everything else seems to be durable and repairable.
Theres someone near me that has two of these bad boys with the carts for 500$ each cart included. Thinking about picking up one of them next weekend. They also have a 7000 series scope and a couple of the rack mount versions. I dont NEED a new scope but I know ill want to get up to 1Ghz eventually.
Thank you as always for your videos. They have been a great help for me with my Tek gear.
For the 576's make sure they have the black silicone high voltage transformer (late serial numbers) the brown epoxy potted ones have a high leakage current and are all faulty as far as I know. One other quick test is if the CRT is double peaking. Brighter -> dimmer - > brighter this is the result of cathode poisoning both would be terminal failures and make them parts units.
Hi - I finally got it fixed. thanks for all the hints. important on was the isopropyl alcohol to clean the invert button. I was going to start to take 1/2 the boards out to dismantle the invert switch... would have a been a hell of lot of work...but lubricated with Kontact WL and 61 to lubricate the switch.
The issue was the 11Kuf 5 cap of the 5V rail - step generator was out.
I don't have to be jealous of you no more with my 576 😁
Love you work !
Awesome glad to hear it is up and running again and survived the trip.
I just got a 576 and am in the process of rebuilding it. Where did you get the PCBs for the caps?
Here is the link the price is for 3 boards it is an open source oshpark project: oshpark.com/shared_projects/hpUFRhHC
Magnificent look at what it takes to make one of these function. I have 2, one was bought as a ‘parts car’ for the other. At this point, time has taken its toll. Repair is likely beyond the scope of where I personally want to go. 🙁
Great job. Had to recap mine about 10 years ago. Wish I would have known about those adapter boards. I re-stuffed the old cans. Never again ! Don't use it that much anymore since obtaining a tek 370. I still like to use the old 575. Still the most trouble free CT I have ever owned and it is almost as old as I am.
Thanks, I would love to get a 370 something but they are still a bit out of the budget. How is the 370 do I need to worry about surface mount capacitor plague?
@@ZenwizardStudios Greetings. I have never opened up the 370. It was a hamfest buy some years ago ($50 presumed dead). Much to my surprise it worked . This instrument will probably be outside my skills if/when it malfunctions (other than a power supply problem ) A lot of this later generation equipment is so complex. One of my frustrations is that Hp et-al have out sourced their power supplies and do not include documentation in their service manuals. I don't use the 370 that much. Use the 576 ,577 and 575 most often. Wish my basement was bigger !
I got one and have mostly the same issue described in your video. Thank you so much for you you video.
This one here, though, the 75V rail is low. And adusting all the way up maxes at 65 Volt.
I figured I need to recap all as well.
I was hopping not to take apart just to get cap value.
With situation at my place, thongs are gone get lost. I would live to get all caps first then take it apart and recap hopefully in 1 weekend.
Would you help with cap's values and part number please?
Thank you so much for the heads up on the switches. Mine had the same issue (trace unstable and all over the place).
sprayed it with somethng similar and work them for a bit.
Now the tace shows. But cannot get it in a dot, specially in DC - & +.
It keeps showing in a small zigzagish line.
Happen to know where I should start to work on this
Is there any collector voltage present? if it is not going in to dot mode on DC what is your current per div set to? If it is in a VERY low range like 2nA per Div you might be fighting looping capacitance. If so this might be normal.
Any idea where I can get a replacement knob for my 576?
Hi - for the relays you mention at 7:54. any hints on how to repair/replace them?
I got my 576 back together. the inverter button is indeed a nightmare. the trace moves randomly on the screen. when I wiggle the inverter button then the trace stabilizes a bit. turning the horizontal gain button - the one that switches the relays, also stabilizes the trace - looks like the relays contacts are dirty or used
Thanks for any hints
I have not yet needed to repair or replace any of the relays yet. However the invert cal zero switch pack is a real soar spot. The switch is dirty and needs cleaning and servicing. The CRT dri9ve signals vert and horizontal go through that switch on the way to the tube. So before anything cleaning the switches.
nice video. Would you please post the link to the remanufactured HV transformer info. Looking to source a spare for my backup unit.
Unfortunately, at this time I can not. The transformers were made by a member of the Tek scopes group and were a very limited quantity. They went pretty fast when they were available. But if another run is made it would be announced there before anywhere else.
is there anyway you could share the capacitors value and info, Pleaseee.
I don't know if you remember after working on this 576 2 years ago... I have a crt trace that is not staying in focus. First it will come up soft and fuzzy and the sharpen and then lose focus again. All voltages are fine CRT 4000V voltage is fine. Wondering,
There are a few things that would cause this. Some are good some are terrible. The worst case scenario would be an internal tube issues where one of the element has broken off internal to the tube. The 576 tube is unique and therefore almost impossible to find as it was used in no other instrument. The better case scenario would be a voltage coming and going or a cold solder joint. Given that the focus comes in this leads me to believe with minimal information that the fault might be a flaky connect that is moving with thermal stress during warn up. It could also be a bad/noisy focus POT however this pot is in the HV path so care is needed.
One quick way to check the tube, “Is the tube double peaking?” when the brightness control is swept from min to max does the tube brighten, then dim, then brighten again? If the CRT exhibits this behavior then additional trouble shooting is not needed as the CRT has aged out and is very high hour.
@@ZenwizardStudios Thanks for your reply, seems we have a lot of same equipment. I believe I found the problem. Bothe the Focus and Intensity pots are out of spec. Looking for replacement parts now. Trying Sphere up in Canada.
Great minds think alike then 😊, you also might want to try the vintage Tek museum. Or the Tek mailing list. There should be quite a few 576 parts units out there given the HV transformer and tube issues. Before putting too much work in to this 576 does it have the black HV transformer? If it has the brown epoxy HV transformer it is a guaranteed fault if not already in the near future.
@@ZenwizardStudios I have the black transformer.
I just noticed your HP 3488A recycle video I will have to watch after lunch. I have two of those units in storage.
lol
What ripple current spec did you use for the can type smoothing capacitors? I am thinking 3A+ should be fine.
I went with high hour long life 105 degree C Nichicon's I think the 576 has a linier supply so it is rather gentle on the capacitors it is not slamming them like a switch mode supply does. Also non of the caps in the rear of the unit are involved in the collector supply circuits. Those are just the power rails for the unit not the power for the device under test.
The 5V, +12.5, and 100V rails use 3 amp rated diodes. I was wondering what the ripple current rating was for the Nichicon’s you used on these rails. I also checked C188 15uF 100V +50-10% and C18 15uF 100V +50-10% electrolytics (located behind the step amplitude selector switch) and found one bad, replaced both. I found one of the collector supply electronlytics bad (or at least marginal) and replaced it. The collector supply caps are hard to get and difficult to replace even after accessing them. I am relieved that most of them tested ok. I also replaced the C300 Oil filled cap as it tested really bad.
Hello. Thanks for the great videos.
I'm working on repair of a Tek 576 and have a intermittent and sticky INVERT button slide switch. I tried cleaning with the pro electronics cleaner but it is still sticky. I also tried spraying in Isopropyl alcohol with no luck. I now have the board with switch removed and planning to teardown the slide switch and an looking for a replacement grease. Any recommendations? I've heard Vaseline. Thanks
Metalbender22, I would not use Vaseline. I am not sure of its conductive or insulating property's. I will check that. In a switch or a contact you need a conductive lubricant with a good dielectric strength. conductive enough to be invisible to contact closure. Yet NOT conductive enough to short out the entire switch block. Shoot me an E-mail and I will have some more information.
@Zenwizard Studios I also found the internet reference on Vaseline as a poor electrical device. I ended up using Dielectric grease. On page 4-29 of the Tek 576 manual, I removed the Display Switching circuit board. I unplugged the two relays K520 and K620 from their socket and slid out the switch cores from all three pushbutton switches. I then just submerged the lower half in simple green in an ultrasonic cleaner for 4 min. The hardened grease was nicely removed from the inside contacts and the spring contacts. I post cleaned with CRC 05103 QD Electronic Cleaner.
To repopulate the switch cores I took the long plastic rod with slots on either side and manually added each spring clip to the slots then partially slid into a reverse packing tape rolled tube until all contacts were contained to the core. It then greased and pushed the tube contents back into the still soldered down switch housing. The sticky side of the packing tape was outward making for a smooth inside of the size I needed to hold the clips. With this process I did not need to unsolder and resolder the pushbuttons making sure they were in alignment to each other.
Recently, I saw a 576 at a Purdue University salvage sale for $175 along with a Tektronix 7403N scope for $10. I was inspired to pick up one of these machines by your videos. Thank you for your 576 video series which has been great in understanding this hardware. Kevin
FYI, You can do the calibration with resistors. The Alignment Fixture is nice, but not essential. The newer -01 Service manual provides an alternate process.
Indeed, There is a second 576 video that the non fixture was requested. I did the resister calibration on the 2nd 576 restoration.
@@ZenwizardStudios How would you compare the two processes? I am not fortunate to have access to the Alignment fixture, so the -01 manual revelation was a welcome discovery. I just was able to round up a full set of "precision resistors", I will check out your 2nd video as well. Glad to know that you have a video on that alignment process. Thanks for the reply and the excellent content.
@Michael Lynch, Essentially the process is the same. All that is in the calibration fixture is switches and resisters/capacitors to rout the signals and loads. If I remember correct when I did mine getting some of the precision capacitors was an issue. They were EXPENSIVE for the parts that we speced. So it makes for a faster calibration but not necessarily a better one. Tek did not make a fixture for the 577 so that is done all with resisters. If I remember correctly there was 1 step where I used the calibration fixture cause the -01 was not clear what to do was for doing some of the step generator loads. This also might have been because I was lacking a good enough standard in the lab. I am also planning on adding some good precision LCR meters to the lab to help with this in the future. But those are up there in cost so it will be an in time thing. I think total there are 7 videos between the 576 and 577 units. I fell down the rabbit hole hard.
Great video!
What is the serial number? I have 576 on the way….would like to know what I got myself into….
The serial number of interest for the good HV transformer?
@@ZenwizardStudios yes. Mine is b327420. Will it have the good hv ?
It looks like it should. From the documentation T850 is the problem unit the -3 version started in serial number 24xxxx also it looks like you have up updated T300 as well that started in 326320. My unit is actually sloe in serial number 328108 had the good one. If you see black under the HV cover you are good if it is brown there will be issues.
@@ZenwizardStudios thanks I will have the unit in a few days.
Awesome, I hope it works out.
Need your advice... i need to ship the unit to Europe, I will take it with me on the plane from PHX to Brussels.. but I need to reduce the weight from 80 pounds to under 70 pounds (packed)
I was thinking of removing the block 1.6KV transformer - looks quite easy: 4 screws and a dozen cables to cut off - any thoughts?
now I am wondering what I got myself into 😒
First off check the tube, If that does not work look for another unit the 576 tube is unique and incredibly difficult to find even in the USA in Europe they will be even more impossible. However I have good news as well as bad news. The good news is removing the collector supply will reduce the weight significantly. The bulk of the weight in this unit is the power transformer, the collector supply transformer, and housing on the frame. The collector supply CAN be removed with a few screws and a could of cables. The only snag here is the coupling for the collector supply control will need to be disconnected and realigned at the destination. The AC/DC/DC+- control if I recall correctly will not have to be removed as that is a plug. Take EXTREME care then packing the collector supply. The load resisters will be in there and they are a ceramic power resister that will not be easily replaceable. They should be fine but are sensitive to physical impacts being ceramic.
@@ZenwizardStudios thanks for the great advice.
Will be in phz Monday . Unit will arrive Tuesday or Wednesday…. Let’s see what happens 😥
I do remember when I had to recap one of those supplies that a soldering iron and a wire cutter was NOT needed. However a hex key and screwdriver was. The good news is there were designed to be serviceable. Unlike the cap stack those are kind of awful to get to.
@@ZenwizardStudios The 576 has arrived...
has the new HV supply. I will now remove the black transformer - i loosened the bolts a bit and looks like the transformer will drop out. hope this gets me under the 70 lbs, including the packaging, to fly it over with me :)
i took not check the tube - but the lights on the read out module are very dim so I suspect a power supply issue
will keep you updated
Quite a job! Great work!!
Hey there, great vid! I don't see it so I thought i'd ask, did you ever upload the calibration video? I've got a 576 that I'm about to bring back to life. I'm going to start searching for a calibration fixture but it seems like that's a tough find. Would love to get some sense of the process.
FYI, my device has the good transformer and is in really good condition, no cracks in any of the buttons and the tube is really bright. It does have a trace that bounces all over the place but does, at times, settle down and hold a spot until I mess with it at all. Hopefully switches and not capacitors, lol.
Thanks again for the first vid, it was very helpful.
Andy
Hey Andy,
I have bad news and some good news. The bad news is the cal fixture. They tend to be rare but when they do come up they tend to be $1000 + on the secondary market. Now the worst news. You need to check in the calibrator to make sure it is in spec befor you use it to cal a 576. For that you need a precise DMM. I think a Keithly 6500 will do it a Keithly 7510 Will most likely do it. And an Keysight 3458A should most deffinatly do it. Being 6.5 digit 7.5 digit and 8.5 digit respectively and priced accordingly. You must read some pretty low value resisters accurately. Which gets me in to the good news. All that is in the calibration fixture is some precision resisters (low tolerance) for loads and some precision capacitors again low tolerance. I have not done a video on it yet but if the trace is jumping around when you are moving the current/div switch The amplifier DC balance is off and needs to be adjusted. I have a 577 that I had to fight for HOURS to get the cal right. It ended up I needed to cal the 177 before I did the 577 the DC balance was messing with the amplifier alignment.
Now for the good news: In the later service manual there is an alternate calibration procedure. This procedure specs out the load resisters and the load capacitors needed for the calibration. Tolerances are TIGHT ¼% tight. I found it was cheaper to buy a block of 10 or more 1% resisters and select from them the ones that were in the tolerance needed especially case you need some high wattage resisters. Up to 10 Watts if I remember correctly. So you need a way to measure low resistances with accuracy. So with the right loads you can do it without the cal fixture. Take care in the 576 there are some extreme voltages. But I am glad you found one with a good tube and transformer!
Zen
@@ZenwizardStudios Yeah, the cal fixture pricing isn't a surprise, lol. I'd probably pick one up if I could figuring I'd play with it for a while and could always sell it again down the road but I'm going to want to cal this device before I find one I suspect. I did fine a company that says they rent one. I asked for a quote but haven't gotten it yet.
I think the best DM I have in that regard is a Fluke 8846A, I don't remember the exact specs, I'll have to check. If not, I'll have to accelerate my search for an 8.5 digit. Do you have a link to the alternate cal procedure? I have two physical copies of the manual and the digital one floating around online but none of those has that in it.
Yeah, I'm fairly comfortable with the voltage issues but I do have one question. Normally, I'm pretty careful about using a discharge device on the high voltage caps before I do anything in a device but with this one, they appear to be unaccessible without some disassembly. What is your experience with their discharge time and / or, how are you dealing with that?
Thanks again for the video, and the help here. I really enjoy your videos and am looking forward to watching the rest of them as I have time.
Andy
One more quick question. You mentioned using straight IPA to clean the switches. Do you not use Deoxit or something like it in general or is there something about this unit that caused you to not use it?
Disregard the cal procedure question. I found it on Artek and bought it.
Andy,
You do NOT need an 8.5 digit meter of more importance is ohms accuracy at very low ranges. Something the 6500 excels at. You will also want a set of kelvin sense leads If memory serves you need something like 1 Ohm at 10 Watts for one of the ranges. This is somewhat tricky to measure accurately given the low resistance value. I have a 6500 in the lab and that is currently my highest accuracy. I do not have an 8846 but I do have a 8840 in the fluke I can check the resisters against the 6500. The kelvin leads I ended up with were www.digikey.com/en/products/detail/pomona-electronics/6730/603918 I have no complaints so far. 4 wire measurement is needed at the lower resistance level the lead resistance will greatly influence a 1 Ohm resister especially when accuracy needed is ¼%. In terms of the power supply the real danger here is the collector supply just the test terminals can be lethal 1500 Vdc at 220 Watts. Depending on the setting that can be exposed at the front panel under normal operation, And this unit has 2 power supplies the main power supply and the collector supply these are isolated from each other and have different sets of storage caps. Also there is no way to disconnect the 1500 V collector supply internally. It is ac to variac (collector supply) right into the transformer in the bottom. Any time the unit is on treat that as live and take care.
In terms of the IPA. The switches on this example were not that bad really just noisy. In this case IPA and some lubricant was all that was needed. My processes and procedures are always being improved and fine tuned. I currently do not have enough practical experience with de-oxit to way in one way or another. Though my service manual for my DC voltage standard calls for Shield it. To maintain some pretty sensitive switch contacts for a precision voltage divider. As with anything test for reactivity for anything you are using in a non-critical area. You do not want to dissolve the plastic on an unobtanium control.
Thanks for the comment about the videos. I will keep making videos as long as people are finding the information useful and helpful.
Zen
Colossal project,where did you get the capacitors adapter boards?
Hi Rollin and welcome, The boards are open hardware from Oshpark. Here is a link they are not the cheapest on the planet but high quality with gold plating. You will need to file down some sharp tags from manufacturing but a small files makes quick work. If i remember right they are in lots of 3.
oshpark.com/shared_projects/hpUFRhHC
Let me know if there is anything you would like to see worked on and I will see what I can make happen.
I have one of these. I’m trying to decide what to do with it. Can you point me to the serial number = trouble information?
There is really only 2 sticking points with this that are a “terminal” failure with no parts available. One is the high voltage transformer (under the cover in the HV supply left side of unit.) The other is the tube its self. Unfortunately these are UNIQUE parts to the 576 and were used no where else in the tek line up of equipment. The transformer you want to have is the one with the black silicone potting insultation. The brown epoxy insulation there seems to be a thermal issue with leakage current. In mine when I did a burn in test of the power supply the unit oscillated. The -75 volt rail would collapse and the unit would go in to over current protect. There was some one who commissioned a transformer recently but the supply has dried up from that run. The tube is also unique and used no where else. There are 2 styles -00 -01 and -05. All are pretty much the same tube the -00 has a slightly different graticule. If the tube is bright and transformer is good your unit should be mostly trouble free. I have a very early example of this one that needed and extensive power supply rebuild. If there is sprauge caps on the rectifier board I advise changing them. Some of mine were 113 Ohms ESR which is AWFUL should be in the 0.XXX not 100.XXX rebuild the supply actually dropped the power consumption by 10 Watts so it was needed. Everything else seems to be durable and repairable.
Hi. Stupid queation but, how do you take the covers off? 😂 really how? Please
Which covers side? or the covers on the test module on the front porch as Tek called it?
@ZenwizardStudios thanks for the reply. The 2 side covers. Lol, I figured it out. Under the warranty stickers. Hahahaha
Any idea where I can get a replacement knob for my 576?