I would start with any Transistor or FET that is located in the trigger generator or sweep generator circuits (this is an extensive list, refer to your specific instrument schematic). Start with the components closest to the Tunnel Diodes and work out. Keep in mind that you have a "B" trigger circuit which is almost identical and uses many of the same components. You can substitute the "B" components into the "A" circuit until you get a working "A" Trigger. Process of elimination. I have only repaired one Model 453, but I use that same technique in the 465/475 whenever possible. This assumes that your major components are installed using sockets, which makes the swapping of components pretty simple. Soldered in components are more trouble, especially tunnel diodes.
--
Michael Lynch
Dardanelle, AR
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Re: Repairing a 148-0034-00 Relay
Barry: The vintageTEK Museum has a stock of these relays and we can set up a special ebay sale for you.
--
Bob Haas
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Hi all,i hope its ok asking this here but here goes,i brought a hp 54503a scope with dead nvram and a dead psu,i swapped the psu,now it powers up but i get no trace,running self test brings up analog trigger fail,D/A converter fail and A/D converter fail,my question is will the new nvram chip result in a fix for these as ive not fitted it yet?,cheers in advance.
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any idea where to start checking then?,is there any common components can cause this?
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Re: Sick TG501 Main 1Mhz ref not running.
On Monday 29 November 2021 02:09:55 pm Harvey White wrote: Would a standard 14 pin oscillator package work?? 14 = vcc, 7 = gnd, 8 =
output, and no other pins are connected.? A 14 pin wirewrap socket with
pins removed (and an under socket jumper on the socket) would save
having to make a board.
I think that 1 Mhz is available.?? you could do something similar with a
half-dip size and a few more jumpers. I happen to have a whole pile of those, if anybody wants one. Feel free to contact me off-list... Harvey
On 11/29/2021 1:54 PM, Zentronics42@... wrote:
Dealing with the gate inputs is easer said then done. On this one they tied the inputs together at the board level under the IC socket. I am starting to think getting this running will be a redesign of the clock. If I shoot out 1Mhz at pin 8 at a TTL level that should get the unit up and running again. So I might be in to making an adaptor board. That can use the socket to get 5 Vdc and output the 1Mhz. would most likely add to the stability as well with modern parts.
Zen
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of SCMenasian
Sent: Monday, November 29, 2021 12:29 PM
To: [email protected]
Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running.
I reasoned that this was a really poor way of building an oscillator and that, since TTL really isn't a good analog part, circuit operation could be dependent upon the individual part's characteristics. When I build oscillators from logic parts, I usually use Schmitt trigger parts; Tektronix didn't. 74HC132, 74hct132 or 74ls132 might work like a chram. Not wanting to reengineer the Tektronix circuit (and parts of it using the other 2 sections of the part), I took the path of least resistance and dug around in my junk bin of little used ancient parts and came up with another 74L00. The part I used was old - possibly older than Tektronix's part. The circuit sprang to life and that was good enough for me.
Crystal oscillators can be tricky since individual crystal characteristics can vary widely. You might be able to get it to run by playing with the capacitances; however, you might not be able to calibrate the frequency. Try lifting one leg of C105. A 74HC00 might be interesting to try. You can always try an LS00 or an HCT00. Note that you can reduce capacitive loading a bit by lifting one input of each gate and conecting it to +5V. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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Re: 1502 TDR RECORD functions
Hello Reg,
The 1502 is the first time 2 of my hobbies have come together, electronics and woodwork.
I can get rolls of paper that fit our credit card machine and with a fine blade they can be cut down to the right size on the bandsaw. Not that I use a lot of paper.
You mention the the illumination....... Something I've looked at and it all seemed a bit tight, so it never got done. Keep us informed on how you go about it, then I might have a go. I have to say it's the only downside to my machine.
Good luck.
Monday, November 29, 2021, 11:43:40 PM, you wrote:
RBvgi> All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.
RBvgi> I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.
RBvgi> I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.
RBvgi> A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.
RBvgi> The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.
RBvgi> First up is LED graticule illumination.
RBvgi> Have Fun!
RBvgi> Reg
RBvgi>
--
Best regards,
John mailto:john@...
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Re: 1502 TDR RECORD functions
All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.
I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.
I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.
A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.
The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.
First up is LED graticule illumination.
Have Fun!
Reg
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Re: OTish: ROM/RAM bank switching in the 2467 et al.
I did. It was a bit of tedious work to derive the equations from the gate programming. Afterwards I noticed the source where I got the JEDEC file had also posted the original equations from which the JEDEC file was generated (doh!).
Can't wait to see your GUI rendering of a 24xx front panel in MAME!
-mark
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On Mon, Nov 29, 2021 at 01:06 PM, Siggi wrote: ...
Ah, that's cool. Did you reverse the full definition of the PAL?
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Repairing a 148-0034-00 Relay
After getting my 7B50 to produce a sweep, I noticed that the x10 magnification function isn't working and traced that to a bad K780 relay (P/N 148-0034-00). I noticed the TekWiki page for the various relays has links for some repair techniques and, since my relay's coil checked open circuit, I decided to open it up.
Fortunately, the wires are intact and it appears that because those were wrapped around the pins and, possibly, micro-welded(?), enough resistance has built up over time between the wire and pins such that there's not a good contact anymore. I can get the relay to function if I apply 15VDC directly to the wires at the pins but that doesn't work if I just touch the pins where they protrude through the bottom of the relay.
I'm wondering if I can wrap a fine copper wire around the existing wire/pin, secure it as snugly as I can get it, and then, perhaps a very light soldering job might be enough to repair this.
Anyone else tried to repair these and, if so, any good advice as to how to proceed? That's some extremely fine wire and, apparently, very easily broken so I'm wanting to tread as lightly as possible.
Thanks,
Barry - N4BUQ
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Re: 1502 TDR RECORD functions
Do you have a good supply of paper for the chart recorder? If not, whether the chart recorder works is moot! Personally I think the X-Y output module is more useful: at least that can be fed to a digitising scope.
The service manual is worth reading. There are minor differences between the civilian and the military (Patriot battery) manuals, but nothing that I have found significant.
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On 29/11/21 22:14, Reginald Beardsley via groups.io wrote: My 1502 arrived today.
Unfortunately, I either have a fault in the RECORD function or completely misunderstand the manual.
The paper feeds if I push the switch up. However, I do not get an accurate trace and the CRT sweep stops until I power cycle it. If I push the switch down and hold it for a photo the sweep also stops. When I release the switch the paper feeds.
I did get a couple of sweeps in the form of a vertical line about 1 division high which tracked the shorted BNC connector waveform but nothing I would interpret as a "flood" of the CRT at the end of the sweep to make the graticule visible..
I fed the BNC signal to a 200 MHz DSO which revealed that the 1502 is producing alternating 4.8 and 11.1 microsecond pulses at ~25.5 kHz.
I'd planned to measure the rise time of the 1502 pulse on an 11801 but I can't see how I can do that if the pulse periods alternate.
Happily, it does appear to be able to resolve discontinuities in cable adapters and connectors in a manner comparable to and 11801 &SD-24.
Can anyone explain what is going on? I'm about to start reading the service manual.
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1502 TDR RECORD functions
My 1502 arrived today.
Unfortunately, I either have a fault in the RECORD function or completely misunderstand the manual.
The paper feeds if I push the switch up. However, I do not get an accurate trace and the CRT sweep stops until I power cycle it. If I push the switch down and hold it for a photo the sweep also stops. When I release the switch the paper feeds.
I did get a couple of sweeps in the form of a vertical line about 1 division high which tracked the shorted BNC connector waveform but nothing I would interpret as a "flood" of the CRT at the end of the sweep to make the graticule visible..
I fed the BNC signal to a 200 MHz DSO which revealed that the 1502 is producing alternating 4.8 and 11.1 microsecond pulses at ~25.5 kHz.
I'd planned to measure the rise time of the 1502 pulse on an 11801 but I can't see how I can do that if the pulse periods alternate.
Happily, it does appear to be able to resolve discontinuities in cable adapters and connectors in a manner comparable to and 11801 &SD-24.
Can anyone explain what is going on? I'm about to start reading the service manual.
Reg
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Re: JFETs - was Re: [TekScopes] 465B won't trigger
Here¡¯s an update on the 465B trigger circuit JFETs. First, I¡¯ll provide details for those interested. Others, just skip to the last couple of lines for the conclusion.
Reading the schematic from the ¡°missing pages¡± document at BAMA and the theory of operation in the service manual helped me understand how this part of the circuit works. It¡¯s a voltage follower to provide a low-impedance signal to U7331 and protect it from high voltage signals. It seems that the main requirements for this part are low input capacitance to maintain the ability to detect and trigger upon VHF components of the signal, and the ability to provide Id in the 10-15mA range. Low noise might be helpful. Per the spec sheets and comparison to those of the 2N4416 and 2N5454 cited in the Tek documentation, I found that the J310s and J211s I had on hand might be suitable. To measure the Id characteristics near the operating point in the circuit, I built a similar circuit on a prototyping board with 100 ohm and 20 ohm resistors, plus a scrap of wire to change Vgs. I applied 6V via another 100 ohm resistor to measure Id. With each FET type, I adjusted the power supply voltage upwards and back a little bit to verify that I¡¯m to the right of the knee on the Id/Vds curve. I recorded Id for drain resistances of 0, 16.7, and 100 ohms. 16.7 (100 and 20 ohms in parallel) was the closest I could easily get to the 15 ohms that the Tek circuit uses for the resistor between G and S.
The original unmatched JFETs had Idss of 11.3 and 12.2 mA, a difference greater than the 0.5 mA matching spec in the Tek documentation. Id fell to 7.5 and 8.1 mA with a 100 ohm resistor between G and S.
The currents in all 3 columns for the J211 were closer to the originals than the J310 numbers. I chose matching J211s and installed them in the ¡®scope. The voltage at U7331¡¯s input is now -15 mV. Id in the JFETs is now 11.3 mA. Vgs is about -0.17 V. It triggers on my strong 40 MHz sine wave signal. I haven¡¯t tried more-challenging signals yet.
BTW, I noticed a discrepancy between a voltage in the circuit and its marking on the schematic. The +8V line was actually at 8.6V. I tracked down its source on the schematic. It¡¯s derived from a 6.2V zener on a 15.0V supply line. It appears that this is the intended voltage, as there is no provision to adjust it. And in this circuit, it doesn¡¯t matter anyway.
In conclusion, the J211 may be a suitable substitute for the 151-1042-00. The input capacitance is not clear on the datasheet, but with an intended application including VHF, it¡¯s probably quite low. At 10 for less than US$ 4 from Mouser or Digikey, it¡¯s pretty cheap to buy 10 and match them one¡¯s self.
I hope this helps the next person. Many thanks to the people on this forum who helped me explore options and think this through!
Halden VE7UTS
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Re: Sick TG501 Main 1Mhz ref not running.
Zen,
I converted all of my TG501s over to "Option 1" Units with the 5Mhz Oscillator. This might be a solution as well.
--
Michael Lynch
Dardanelle, AR
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Re: Sick TG501 Main 1Mhz ref not running.
It should I would like to keep the adjustment capability for future calibrations as this unit will need to travel 1/2 way around the world when it goes back to its owner. Unless the 1Mhz clocks are good enough at this point that they don¡¯t need adjustment?
That would be wildly convenient if it would work the socket uses standard TTL with 7 gnd, 14 VCC = 5.2Vdc. And in this case 8 is the output if the ring. As long as the frequency stability is there this might be a solution to the issue, And great to know going forward.
Zen
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Harvey White Sent: Monday, November 29, 2021 2:10 PM To: [email protected]Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running. Would a standard 14 pin oscillator package work? 14 = vcc, 7 = gnd, 8 = output, and no other pins are connected. A 14 pin wirewrap socket with pins removed (and an under socket jumper on the socket) would save having to make a board. I think that 1 Mhz is available. you could do something similar with a half-dip size and a few more jumpers. Harvey On 11/29/2021 1:54 PM, Zentronics42@... wrote: Dealing with the gate inputs is easer said then done. On this one they tied the inputs together at the board level under the IC socket. I am starting to think getting this running will be a redesign of the clock. If I shoot out 1Mhz at pin 8 at a TTL level that should get the unit up and running again. So I might be in to making an adaptor board. That can use the socket to get 5 Vdc and output the 1Mhz. would most likely add to the stability as well with modern parts.
Zen
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of
SCMenasian
Sent: Monday, November 29, 2021 12:29 PM
To: [email protected]
Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running.
I reasoned that this was a really poor way of building an oscillator and that, since TTL really isn't a good analog part, circuit operation could be dependent upon the individual part's characteristics. When I build oscillators from logic parts, I usually use Schmitt trigger parts; Tektronix didn't. 74HC132, 74hct132 or 74ls132 might work like a chram. Not wanting to reengineer the Tektronix circuit (and parts of it using the other 2 sections of the part), I took the path of least resistance and dug around in my junk bin of little used ancient parts and came up with another 74L00. The part I used was old - possibly older than Tektronix's part. The circuit sprang to life and that was good enough for me.
Crystal oscillators can be tricky since individual crystal characteristics can vary widely. You might be able to get it to run by playing with the capacitances; however, you might not be able to calibrate the frequency. Try lifting one leg of C105. A 74HC00 might be interesting to try. You can always try an LS00 or an HCT00. Note that you can reduce capacitive loading a bit by lifting one input of each gate and conecting it to +5V.
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Re: Sick TG501 Main 1Mhz ref not running.
Would a standard 14 pin oscillator package work?? 14 = vcc, 7 = gnd, 8 = output, and no other pins are connected.? A 14 pin wirewrap socket with pins removed (and an under socket jumper on the socket) would save having to make a board.
I think that 1 Mhz is available.?? you could do something similar with a half-dip size and a few more jumpers.
Harvey
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On 11/29/2021 1:54 PM, Zentronics42@... wrote: Dealing with the gate inputs is easer said then done. On this one they tied the inputs together at the board level under the IC socket. I am starting to think getting this running will be a redesign of the clock. If I shoot out 1Mhz at pin 8 at a TTL level that should get the unit up and running again. So I might be in to making an adaptor board. That can use the socket to get 5 Vdc and output the 1Mhz. would most likely add to the stability as well with modern parts.
Zen
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of SCMenasian
Sent: Monday, November 29, 2021 12:29 PM
To: [email protected]
Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running.
I reasoned that this was a really poor way of building an oscillator and that, since TTL really isn't a good analog part, circuit operation could be dependent upon the individual part's characteristics. When I build oscillators from logic parts, I usually use Schmitt trigger parts; Tektronix didn't. 74HC132, 74hct132 or 74ls132 might work like a chram. Not wanting to reengineer the Tektronix circuit (and parts of it using the other 2 sections of the part), I took the path of least resistance and dug around in my junk bin of little used ancient parts and came up with another 74L00. The part I used was old - possibly older than Tektronix's part. The circuit sprang to life and that was good enough for me.
Crystal oscillators can be tricky since individual crystal characteristics can vary widely. You might be able to get it to run by playing with the capacitances; however, you might not be able to calibrate the frequency. Try lifting one leg of C105. A 74HC00 might be interesting to try. You can always try an LS00 or an HCT00. Note that you can reduce capacitive loading a bit by lifting one input of each gate and conecting it to +5V.
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Re: Sick TG501 Main 1Mhz ref not running.
Dealing with the gate inputs is easer said then done. On this one they tied the inputs together at the board level under the IC socket. I am starting to think getting this running will be a redesign of the clock. If I shoot out 1Mhz at pin 8 at a TTL level that should get the unit up and running again. So I might be in to making an adaptor board. That can use the socket to get 5 Vdc and output the 1Mhz. would most likely add to the stability as well with modern parts.
Zen
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of SCMenasian Sent: Monday, November 29, 2021 12:29 PM To: [email protected]Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running. I reasoned that this was a really poor way of building an oscillator and that, since TTL really isn't a good analog part, circuit operation could be dependent upon the individual part's characteristics. When I build oscillators from logic parts, I usually use Schmitt trigger parts; Tektronix didn't. 74HC132, 74hct132 or 74ls132 might work like a chram. Not wanting to reengineer the Tektronix circuit (and parts of it using the other 2 sections of the part), I took the path of least resistance and dug around in my junk bin of little used ancient parts and came up with another 74L00. The part I used was old - possibly older than Tektronix's part. The circuit sprang to life and that was good enough for me. Crystal oscillators can be tricky since individual crystal characteristics can vary widely. You might be able to get it to run by playing with the capacitances; however, you might not be able to calibrate the frequency. Try lifting one leg of C105. A 74HC00 might be interesting to try. You can always try an LS00 or an HCT00. Note that you can reduce capacitive loading a bit by lifting one input of each gate and conecting it to +5V.
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Re: OTish: ROM/RAM bank switching in the 2467 et al.
On Sun, Nov 28, 2021 at 4:40 PM Mark Litwack <mlitwack@...> wrote: I think writing an emulator would be a monumental task considering all the
hardware registers that can affect the execution path. I think it would be
easier to hook up a logic analyzer and work on the real thing. All the
state inputs for the analyzer are exposed and can be probed directly (like
the ROM and PAGE signals). I've done this on several occasions for the
2465 and the 2445A to try to learn how some of the code works.
I guess it depends on what sort of tools you're used to working with. I'm a "recovering software engineer", so my handiest hammer will probably always be software. I've looked at MAME, which is primarily used to emulate arcade games, but it has all the infrastructure already made for building an emulator, so to build an emulator for the 2400 scopes would be mostly about writing up the register emulation. It doesn't look too daunting from afar :). Introducing two more bits to encompass all the available memory, I agree,
is probably the easiest way. I don't know anything about ghidra, but maybe
it has a configurable MMU that could map the overlayed addresses using the
two extra bits? When working with the logic analyzer, I created two additional high-order address bits called R and P, for ROM and PAGE. It really helps to add some
sanity while examining the disassembled execution trace.
Yeah, that I can see already. I think you've already figured this out, but here is a little bit of a
dive into the PAL decode which might be useful:
Ah, that's cool. Did you reverse the full definition of the PAL?
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Re: Sick TG501 Main 1Mhz ref not running.
I reasoned that this was a really poor way of building an oscillator and that, since TTL really isn't a good
analog part, circuit operation could be dependent upon the individual part's characteristics. When I build oscillators from logic parts, I usually use Schmitt trigger parts; Tektronix didn't. 74HC132, 74hct132 or 74ls132 might work like a chram. Not wanting to reengineer the Tektronix circuit (and parts of it using the other 2 sections of the part), I took the path of least resistance and dug around in my junk bin of little used ancient parts and came up with another 74L00. The part I used was old - possibly older than Tektronix's part. The circuit sprang to life and that was good enough for me.
Crystal oscillators can be tricky since individual crystal characteristics can vary widely. You might be able to get it to run by playing with the capacitances; however, you might not be able to calibrate the frequency. Try lifting one leg of C105. A 74HC00 might be interesting to try. You can always try an LS00 or an HCT00. Note that you can reduce capacitive loading a bit by lifting one input of each gate and conecting it to +5V.
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Re: Sick TG501 Main 1Mhz ref not running.
An early engineering assignment back in the early 90's was the implementation/migration of a process monitor ring oscillator on a 486 variant (486SL). The product was migrating to the next process node.
HSpice simulation of the ring oscillator showed a significantly smaller output swing - too small. The issue was the new process node was "too fast" and while the oscillator worked, the reduced delay through the chain resulted in the output not having time to transition much. The solution was to add more inverters to the chain. There are other ways to slow the ring down - add more capacitance, use slower transistors (longer L), ...
That your pin 6 is "stuck" at 3.6v makes me wonder if the replacement U100 is "too fast" and the output doesn't have time to transition.
Dave
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On Monday, November 29, 2021, 07:23:23 AM PST, Dave Peterson via groups.io <davidpinsf@...> wrote:
I keep wondering about the replacement 74L00 too - is it too fast? Are you replacing it with new, and is the newer construction different in performance than original?
What happens if you add capacitance to pin 3 (4 & 5) of U100? A breadboard would have more capacitance than the board, wouldn't it?
Dave
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On Mon, Nov 29, 2021 at 10:43 AM, Mike Merigliano wrote:
Not sure about mods, but I would really make sure that the problem is with the
tunnel diodes in the unit you have. It seems strange that all four of them
would have failed. There are other parts of the circuit are worth checking,
and the Tektronix repair documents are very helpful.
Mike, I agree 100%. One tunnel diode, maybe, but four at thee same time? That would be a very rare occurrence. I have had several trigger failures on the 465 series and they have all been related to the circuitry around the tunnel diodes. . -- Michael Lynch Dardanelle, AR
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Michael W. Lynch
Bob Haas
Dave Peterson