AM503B & A6302 current amp&probe
Hi all,
I acquired a nice & functional set of these recently. The only "flaw" so fare is an error message of the current amp due to an empty battery.
I asked myself whether this battery holds critical data (calibration or such) or if the values retained are merely the results of the degaussing & normalizing action and as such are renewed whenever I press the button. To my surprise I could not find any manual of the 503B that includes circuit diagrams. I checked Artek Manuals, no luck either. I found a more complete service manual somewhere, but without the circuit diagrams!
Reading through what I got about the AM503B, there is mention of the A6302 probe having an offset adjustment for itself. Now I do have 2 other A6302's but they only work in AC. One has a hole for the adjustment screw, the others (including the one I got with the 503B) do no seem to have this adjustment. Again, search for service manuals WITH circuit diagrams was fruitless. All I got were rather detailed dismantling instructions...
Anyone has a link to some source or can provide schematics for these units? Is there something special about the AM503B or the A6302 so Tektronix decided not to provide complete service information?
Thanks & cheers
Martin
|
AA5001 Mid-Repair Readings
I recently picked up an AA5001 and FG5010, both appearing to be well cared-for. I am a bit excited since I have been hoping, for several years, to find a nice set-up like this and my patience finally paid off.
For background:
1. The FG5010 had a sticker on it, saying "output flaky". The output BNC was a bit loose, so I tightened it up. The output appears stable, and at least on the scope it looks just fine.
2. The AA5001 provided reasonable level readings at the 600mV and higher levels, but level measurements were very low and unstable at the lower ranges.
3. In auto-range level mode, it would not settle on a valid reading.
4. In THD mode, the readings were not stable, but were in the range of 70% to 105%, which is obviously not a valid reading.
The internals are very clean and nothing appears to be discolored. After reading some of the previous threads, I focused on the A14 board range switching circuitry. I removed and exercised each range switching relay, running 1000Hz and 10KHz signals through, while pulsing them and staring at the scope looking for any glitches. After they all passed this test, I reinstalled them.
At the 200mV level, and at the three lower levels, the balanced input signal is passed through a pair of small (3 watt) lamps. I am assuming that these lamps are used for overload protection. Being 120V bulbs, I assume that they behave like a resistor, unless a significant voltage is applied. What I found was one of the bulbs is open, so that explained the bad level readings at the four lowest ranges.
I have found replacement bulbs, which are expected to arrive in a couple of weeks. Of course, I am curious to know if the blown bulb may be the only problem. The one good bulb has a cold reading of a little over 500 ohms, so I have temporarily replaced both bulbs with 560 ohm resistors.
With the boards reassembled, splayed-out on the bench, outside the chassis, and with no framework or shielding, it does now provide stable level readings, including believable readings at the lower ranges. Even more promising, auto-ranging works, and the THD reading does settle at a much more reasonable reading. With the FG5010, it is reading 0.140% and with a second function generator, I am seeing 0.220%. While neither of these measurements are great, I am thinking that they might improve once the module is reassembled, and the shielding is back in place.
My question, for those who have experience with the AA5001, is whether I should expect to see improved readings once I replace the bulbs and get it reassembled. Unfortunately, I will need to wait another two weeks for the bulbs to arrive, when I will be able to put it all back together, then I will see the answer for myself. I guess I am excited, impatient, and looking for some reassurance that these THD measurements might be pretty normal, since it is unshielded.
Thanks,
Brian.
|
Re: Help with an ailing 7D14
William,
My first guess, just based on the obvious heat/time dependence, is that you have a bad solder joint in the chain from 20A/B, and I would try to do a close visual examination of all components in that chain. From the pictures on the TekWiki this counter doesn't seem too tightly packed, but it DOES seem to have a lot of socketed ICs. My experience with other instruments of similar age is that the socketed ICs are good suspects for bad connections. I would at least give them all a close inspection, if not remove, clean, and reseat every one of them (I'm not usually a proponent of shotgun techniques, but Tek had a specific problem with bad sockets at one point, and with oxide layers forming on IC pins even in the "good" sockets, so this is an exception).
-- Jeff Dutky
|
Re: tek 2215 trace position issues
i cant find q 736 on the pcb for the life of me.
|
A while ago, I was querying here about a 7D15 freq counter that was on the fritz. It was a questionable cap and a bad solder joint and the good news is that has been repaired. (There was also some cockpit error.) Anyway, I wanted to mend a 7D14 I have that is flaky and wonder if I can get some help on narrowing down the problem. Below are the facts. (And, note, several years ago, David, W7PF, appropriately lectured me on a crappy job I did documenting the set-up. I will attempt to do better this time.)
(1) Problem is that the 7D14 stops displaying the frequency (i.e., displays all zeroes) when the signal is sourced from a vertical amp. I have tested with a signal input from the unit's front panel BNC and it does seem to not fail.
(2) The problem seems heat related.
(3) The set up is as follows:
(a) Scope is 7704A.
(b) 7A26 in left vertical slot.
(c) 7B92A in horizontal slot A.
(d) 7D14 in in horizontal slot B.
(e) Vertical mode LEFT.
(f) Horizontal mode A.
(4) Other settings per 7D14 manual troubleshooting/calibration set up.
(5) Signal input to Channel 1 on 7A26 and adjusted to AC, set to display and trigger on channel 1.,
(6) 7D14 set 10 ms, Trigger Preset, 525 MHz, AC, TRIG SOURCE, and frequency is displayed correctly on CRT.
(7) After about 1-2 hours, the frequency display becomes erratic and then displays all zeroes.
(8) Removing the side panels on the scope and the plug-in and blowing it with cold air causes the frequency to be displayed properly.
(9) Leaving the plug-in exposed (no side panels) causes it to run indeterminately longer without failing. (That is, I have let it run several hours without failure.)
(10) Similarly, I have set it up to read a signal input from the CH A INPUT BNC in the 7D14 front panel and -- even when covered with the side panels -- it seems to run a long time and not fail. (Similarly, I have let it run several hours without failure.)
In looking at the manual and reading the schematic and notes, I am guessing that the vertical input from the 7A26 arrives on pins 20A (+TRIG IN TO T870) and 20B (-TRIG IN TO T870) and, accordingly, I have begun to snoop through schematic <1> CHANNEL A SIGNAL CONDITIONING but sense that I may be a little off. Therefore, I am passing this along and asking for any ideas you all might have.
Thanks in advance.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"
|
Re: Grease for the VOLTS/DIV and the SEC/DIV Controls on TDS Series 310, 320, 340, 350, 382, 420, 430
It sound Like MG Chemicals #847 is the way to go. The smallest size is the 25ml for $27, I will probably never use it again and do not want to invest in it. Any other ideas?.
|
The good news for this project is that the CRT's in the 57x curve tracers are quite slow by tech standards. The cross over from the 5110 is only a 10 Mhz scope and it is an exact match tube. For the horz sweep that is synced to the main frequency as that is what the collector sweep was. It is rectified so it is double mains if I remember correctly so the horz sweep tops out at 120 Hz or 100 Hz depending on location. So for LCD swapping it should be very doable. Also if we manage to spin something up that will work not only for a 57X. I know there is a lot of arcade guys out there that would LOVE a replace for vector CRT's that have died they are waiting on something as well.
Zen
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Harvey White Sent: Wednesday, November 3, 2021 9:50 PM To: [email protected]Subject: Re: [TekScopes] Curve Tracer CRTs Oh, that I did that many years ago from a project in (was it radio-electronics? electronics world? Not sure that it was popular electronics. That's easy, very easy. tap off the horizontal sync. trigger a monostable which makes a dot using the video channel. Then feed in a signal that varies the timing of the monostable. so a minus voltage triggers closer to the horizontal sync, a plus voltage delays it (or vice versa, if you want). You get a fixed 60 Hz sweep, the horizontal sweep frequency is irrelevant, and the trace is vertical. Harvey On 11/3/2021 9:26 PM, Jeff Dutky wrote: Roy Thistle wrote:
I believe I have seen a vector display with magnetic deflection... I believe it is possible. I've seen a YouTube video where someone makes an oscilloscope from a TV picture tube. It is crude, but it works.
This is the video I'm remembering, but there are several others that I turned up with a simple google search. This video has a nice bit of introductory discussion.
-- Jeff Dutky
|
Oh, that
I did that many years ago from a project in (was it radio-electronics?? electronics world?? Not sure that it was popular electronics.
That's easy, very easy.
tap off the horizontal sync.? trigger a monostable which makes a dot using the video channel.? Then feed in a signal that varies the timing of the monostable.? so a minus voltage triggers closer to the horizontal sync, a plus voltage delays it (or vice versa, if you want).
You get a fixed 60 Hz sweep, the horizontal sweep frequency is irrelevant, and the trace is vertical.
Harvey
toggle quoted message
Show quoted text
On 11/3/2021 9:26 PM, Jeff Dutky wrote: Roy Thistle wrote:
I believe I have seen a vector display with magnetic deflection... I believe it is possible. I've seen a YouTube video where someone makes an oscilloscope from a TV picture tube. It is crude, but it works.
This is the video I'm remembering, but there are several others that I turned up with a simple google search. This video has a nice bit of introductory discussion.
-- Jeff Dutky
|
On 2021-11-03 8:46 p.m., Harvey White wrote: Curious.? Unless you need a very different X rate, why rewind the yoke?
Harvey
I mean adapting yokes designed for raster, which have very different horizontal and vertical design frequencies. --Toby
|
Roy Thistle wrote:
I believe I have seen a vector display with magnetic deflection... I believe it is possible.
I've seen a YouTube video where someone makes an oscilloscope from a TV picture tube. It is crude, but it works. This is the video I'm remembering, but there are several others that I turned up with a simple google search. This video has a nice bit of introductory discussion. -- Jeff Dutky
|
Curious.? Unless you need a very different X rate, why rewind the yoke?
Harvey
toggle quoted message
Show quoted text
On 11/3/2021 8:42 PM, toby@... wrote: On 2021-11-03 7:51 p.m., Harvey White wrote:
That's not how you do it.? What you do is read the current through the deflection coil, compare it to your waveform, and then the difference drives the deflection amplifier.? One classic way yields a driving waveform at the TV horizontal frequency that is two pulses with a linear (more or less) rise between them (IIRC).
What you want is a linear /current/? for a linear sweep. I think that's what Roy meant with 'drive with current instead of voltage'.
Rewinding one half of the yoke is necessary anyway, from what I have gathered reading/watching these conversions.
--T
With electrostatic plates, what you see is what you get.
Harvey
On 11/3/2021 5:56 PM, Roy Thistle wrote:
On Wed, Nov? 3, 2021 at 12:27 PM, Jeff Dutky wrote:
magnetic deflection CRT which, if I recall my college physics correctly (no
guarantee at this late date) has lower deflection bandwidth
Hi Jeff:
Well... you'd be trying to drive an inductor (the deflection field coil, in the CRT yoke.)... and in this case Lenz is no friend to you.
I believe I have seen a vector display with magnetic deflection... I believe it is possible.
You could change the resistor, in the yoke, to fiddle with the time constant.., drive with current instead of voltage... wind/rewind a/the custom/deflection coil...or if you want a bandwidth of more than a few 10s of KHz... use use electrostatic deflection.
Cheers and all that too.
|
On 2021-11-03 7:51 p.m., Harvey White wrote: That's not how you do it.? What you do is read the current through the deflection coil, compare it to your waveform, and then the difference drives the deflection amplifier.? One classic way yields a driving waveform at the TV horizontal frequency that is two pulses with a linear (more or less) rise between them (IIRC).
What you want is a linear /current/? for a linear sweep. I think that's what Roy meant with 'drive with current instead of voltage'. Rewinding one half of the yoke is necessary anyway, from what I have gathered reading/watching these conversions. --T With electrostatic plates, what you see is what you get.
Harvey
On 11/3/2021 5:56 PM, Roy Thistle wrote:
On Wed, Nov? 3, 2021 at 12:27 PM, Jeff Dutky wrote:
magnetic deflection CRT which, if I recall my college physics correctly (no
guarantee at this late date) has lower deflection bandwidth
Hi Jeff:
Well... you'd be trying to drive an inductor (the deflection field coil, in the CRT yoke.)... and in this case Lenz is no friend to you.
I believe I have seen a vector display with magnetic deflection... I believe it is possible.
You could change the resistor, in the yoke, to fiddle with the time constant.., drive with current instead of voltage... wind/rewind a/the custom/deflection coil...or if you want a bandwidth of more than a few 10s of KHz... use use electrostatic deflection.
Cheers and all that too.
|
That's not how you do it.? What you do is read the current through the deflection coil, compare it to your waveform, and then the difference drives the deflection amplifier.? One classic way yields a driving waveform at the TV horizontal frequency that is two pulses with a linear (more or less) rise between them (IIRC).
What you want is a linear /current/? for a linear sweep.
With electrostatic plates, what you see is what you get.
Harvey
toggle quoted message
Show quoted text
On 11/3/2021 5:56 PM, Roy Thistle wrote: On Wed, Nov 3, 2021 at 12:27 PM, Jeff Dutky wrote:
magnetic deflection CRT which, if I recall my college physics correctly (no
guarantee at this late date) has lower deflection bandwidth
Hi Jeff:
Well... you'd be trying to drive an inductor (the deflection field coil, in the CRT yoke.)... and in this case Lenz is no friend to you.
I believe I have seen a vector display with magnetic deflection... I believe it is possible.
You could change the resistor, in the yoke, to fiddle with the time constant.., drive with current instead of voltage... wind/rewind a/the custom/deflection coil...or if you want a bandwidth of more than a few 10s of KHz... use use electrostatic deflection.
Cheers and all that too.
|
There was a board called the VectorVGA that converted XYZ inputs to an VGA display (15 pin D connector output). It had color RGB inputs also so it could be used to replace color vector games (Atari Tempest etc.) to VGA. I don't think it's made anymore though. Maybe with some good searching more info can be found on it. The arcade gaming people mostly use the term vector for XY so that's another good search term.
Bob
|
On 2021-11-03 5:56 p.m., Roy Thistle wrote: On Wed, Nov 3, 2021 at 12:27 PM, Jeff Dutky wrote:
magnetic deflection CRT which, if I recall my college physics correctly (no
guarantee at this late date) has lower deflection bandwidth
Hi Jeff:
Well... you'd be trying to drive an inductor (the deflection field coil, in the CRT yoke.)... and in this case Lenz is no friend to you.
I believe I have seen a vector display with magnetic deflection... I believe it is possible. Yes, they exist, and one mass production use was arcade games. People still modify magnetic tubes for X/Y work (for example the 9" mono displays from some computers) because they're relatively plentiful and just not as awkwardly LONG. :) --Toby You could change the resistor, in the yoke, to fiddle with the time constant.., drive with current instead of voltage... wind/rewind a/the custom/deflection coil...or if you want a bandwidth of more than a few 10s of KHz... use use electrostatic deflection.
Cheers and all that too.
|
The Early Television Museum in Hilliard Ohio is likely the last repository of equipment and knowledge to rebuild TV jugs. However, the main problem is obtaining new gun assemblys. There have been talks with suppliers in Russia and China, but so far, nothing has transpired. I think the rarest jug on the planet is a good 15GP22, used in the very first color TVs. The failure is air leaking in through imperfect welds and glass-metal seals. I have heard picture tubes are still being made in India, whether this is true or if they would consider making rebuilding guns and supplies is unknown. It all may be an extinct art soon.
?? Bruce Gentry, KA2IVY
toggle quoted message
Show quoted text
On 11/3/21 17:17, Roy Thistle wrote: On Wed, Nov 3, 2021 at 05:46 AM, Jean-Paul wrote:
Perhaps old CRTs can be restored somehow?
There was someone here who was restoring television CRTs.
When the electron-gun assemblies became unavailable, he stopped doing it. (It's one thing taking the neck of and re-coating the phosphor: It's something else, entirely re-building/building the gun cathode.)
Much of the technology (the 'fixins' and the 'makings') is unavailable, and forgotten.
I fear, restoring these old CRTs would be fearsomely expensive.
If you have to have a CRT and want a project (perhaps equal in work magnitude to the LCD solution?)... perhaps bodging in a more modern? magnetically deflected CRT? is possible. I believe, these type of CRTs are still available.
Cheers, and all that.
|
On Wed, Nov 3, 2021 at 12:27 PM, Jeff Dutky wrote:
magnetic deflection CRT which, if I recall my college physics correctly (no
guarantee at this late date) has lower deflection bandwidth
Hi Jeff: Well... you'd be trying to drive an inductor (the deflection field coil, in the CRT yoke.)... and in this case Lenz is no friend to you. I believe I have seen a vector display with magnetic deflection... I believe it is possible. You could change the resistor, in the yoke, to fiddle with the time constant.., drive with current instead of voltage... wind/rewind a/the custom/deflection coil...or if you want a bandwidth of more than a few 10s of KHz... use use electrostatic deflection. Cheers and all that too. -- Roy Thistle
|
Re: Looking for fasteners in EU
On Wed, Nov 3, 2021 at 04:14 AM, cheater cheater wrote: how does he pull the stock out of the chuck while the lathe
is running? He does that around the two and a half minute mark. There are two different kinds of tighten/release mechanisms on collet lathes. The more common kind requires you to stop the lathe and then turn a handwheel on the left end of the hollow drawbar by hand. The more production style has a lever that sticks forward, toward the operator, from the left side of the headstock. That lever pushes or pulls on a bearing to a rotating collar with a detent that does the tightening/releasing. I used to have access to a very nice Clausing lathe with that sort of quick release (not sure if that's the correct name) but I would often stop the lathe, pull the release lever to the right, and pull the part out of the collet without waiting for the chuck to stop spinning. It never occurred to me that I could move a part without bothering to stop the lathe, but in hindsight it's now clear. While reaching in to grab a moving part is generally forboten, with a small smooth part, free in a collet, there's no real danger. I suspect Joe has that kind of lathe and that's exactly what he did.
|
On Wed, Nov 3, 2021 at 05:46 AM, Jean-Paul wrote:
Perhaps old CRTs can be restored somehow?
There was someone here who was restoring television CRTs. When the electron-gun assemblies became unavailable, he stopped doing it. (It's one thing taking the neck of and re-coating the phosphor: It's something else, entirely re-building/building the gun cathode.) Much of the technology (the 'fixins' and the 'makings') is unavailable, and forgotten. I fear, restoring these old CRTs would be fearsomely expensive. If you have to have a CRT and want a project (perhaps equal in work magnitude to the LCD solution?)... perhaps bodging in a more modern? magnetically deflected CRT? is possible. I believe, these type of CRTs are still available. Cheers, and all that. -- Roy Thistle
|
Re: 577 D2 Display Issues
The shimmering I described was called "double traces" and a fix was described here: /g/TekScopes/topic/77914568#175831by Jack2015, where adjusting the value of R318 eliminates it. I've tried it, and it does make a noticable improvement, but for me not as good as he had and showed on youtube. That's just a comparator threshold, so I don't understand how changing the step threshold could help.
|
Martin
Brian Nordlund, AC7QE
k6whp
Bob Rosenbloom