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.
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On 11/28/2021 1:24 PM, nanovnauser@... wrote: well i have ordered 4 of these,is there any mods need doing to the 453 to use these diodes,or will they work as is?,cheers Paul.
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Re: OTish: ROM/RAM bank switching in the 2467 et al.
Guys, this is a really interesting thread. I wish I had more time to lend a hand!
--Victor
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Re: JFETs - was Re: [TekScopes] 465B won't trigger
If it's Q522/524 and Q622/624 that you are referring to those parts compare to a 2N5245. The Vgs cutoff is a whimsical -1.0 V max. A 2N5454/2N4416 are not even remotely close to being that small. Since this is a trigger/switching circuit app the 2N5245 makes sense in a zero crossing detector.
I am just quoting what one rev of a 465B manual as I heard there are several? Comments?
Fabe
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On Monday, November 29, 2021, 09:37:40 a.m. NST, <toby@...> wrote: On 2021-11-29 1:21 a.m., HF via groups.io wrote: Hi Toby,
Thanks for your suggestions!
I had read of references to the 2N5454 and 2N4416 elsewhere in this forum.? Once I looked in the document Michael referenced, I found out where those came from.? The table describing the matching technique says it's from the 2N4416 "family" and a later page refers to the part itself as a 2N5454.? I was able to find specs on both of these devices, but I'm not sure that those are the specs that pertained to the era when Tek was building these instruments.? For example, the TO-92 package isn't mentioned, and the 2N5454 is described as 2 devices in one can, not individual devices.? But it's all I have, so I put these two at the top of my table for checking other JFETs for potential substitution.
I just looked up Linear Systems; I hadn't heard of them until I saw your post.? It looks like that company is geared towards providing devices for which mass-produced devices are inadequate.? I'm afraid I would be pestering them if I were to call them with a hobbyist need.? But I might still do that, once I study the circuit some more and think I understand it well enough to know why the devices need to have the characteristics on my list. Hi Halden It is weird that Linear Systems is so obscure on the web. I found them very helpful and accommodating with a small/hobbyist order, so I wouldn't hesitate. It looks like I'm experiencing mission creep.? At first I just wanted to get this 'scope working.? But now I see an opportunity to learn something about JFETs and JFET circuits. Same! There's a Teledyne book online that might help: "The Art of Electronics" also covers them in some depth. --Toby Cheers,
Halden
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Re: Sick TG501 Main 1Mhz ref not running.
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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Re: Sick TG501 Main 1Mhz ref not running.
A few years back, I had another Tek TM500 series plugin (I don't remember which one) which used a 74L00 as an oscillator. It also refused to oscillate, even though static measurements indicated the IC looked good. I fixed the problem by swapping the 74L00 with another from inventory. The problem vanished.
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JFETs - was Re: [TekScopes] 465B won't trigger
On 2021-11-29 1:21 a.m., HF via groups.io wrote: Hi Toby,
Thanks for your suggestions!
I had read of references to the 2N5454 and 2N4416 elsewhere in this forum. Once I looked in the document Michael referenced, I found out where those came from. The table describing the matching technique says it's from the 2N4416 "family" and a later page refers to the part itself as a 2N5454. I was able to find specs on both of these devices, but I'm not sure that those are the specs that pertained to the era when Tek was building these instruments. For example, the TO-92 package isn't mentioned, and the 2N5454 is described as 2 devices in one can, not individual devices. But it's all I have, so I put these two at the top of my table for checking other JFETs for potential substitution.
I just looked up Linear Systems; I hadn't heard of them until I saw your post. It looks like that company is geared towards providing devices for which mass-produced devices are inadequate. I'm afraid I would be pestering them if I were to call them with a hobbyist need. But I might still do that, once I study the circuit some more and think I understand it well enough to know why the devices need to have the characteristics on my list. Hi Halden It is weird that Linear Systems is so obscure on the web. I found them very helpful and accommodating with a small/hobbyist order, so I wouldn't hesitate. It looks like I'm experiencing mission creep. At first I just wanted to get this 'scope working. But now I see an opportunity to learn something about JFETs and JFET circuits. Same! There's a Teledyne book online that might help: "The Art of Electronics" also covers them in some depth. --Toby Cheers,
Halden
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Hi Toby,
Thanks for your suggestions!
I had read of references to the 2N5454 and 2N4416 elsewhere in this forum. Once I looked in the document Michael referenced, I found out where those came from. The table describing the matching technique says it's from the 2N4416 "family" and a later page refers to the part itself as a 2N5454. I was able to find specs on both of these devices, but I'm not sure that those are the specs that pertained to the era when Tek was building these instruments. For example, the TO-92 package isn't mentioned, and the 2N5454 is described as 2 devices in one can, not individual devices. But it's all I have, so I put these two at the top of my table for checking other JFETs for potential substitution.
I just looked up Linear Systems; I hadn't heard of them until I saw your post. It looks like that company is geared towards providing devices for which mass-produced devices are inadequate. I'm afraid I would be pestering them if I were to call them with a hobbyist need. But I might still do that, once I study the circuit some more and think I understand it well enough to know why the devices need to have the characteristics on my list.
It looks like I'm experiencing mission creep. At first I just wanted to get this 'scope working. But now I see an opportunity to learn something about JFETs and JFET circuits.
Cheers,
Halden
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"Dans Small Parts" has 2h4416's for a couple o' bux per each ...j310's for
a bunch cheaper ...good stuff, good service, NFI!
Jim
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On Sun, Nov 28, 2021 at 5:50 PM Jeff Dutky <jeff.dutky@...> wrote: Halden,
There are a couple of listings for "Tektronix 151-1042" on eBay. You could
also try Sphere Research (www.sphere.bc.ca), though they don't list any
on their web site, they may be able to dig some out somewhere.
That same part number is used all over the place in other Tek instruments,
including other 400-series scopes (465, 475/A, 485), 2200-series scopes
(2213/A, 2215/A, 2235, 2236), 2300-series scopes (2335, 2336, 2337), 7k
plug-ins (7B53A, 7B80, 7B85, 7B87, 7B90, 7B92), T900-series scopes (T912,
T921, T922, T932/A, T935/A), as well as some TM500 plug-ins (DC504/A,
DC505/A, DD501, FG501A, FG502, FG504, PG507, PG508, SC502, SC503, SC504).
The easiest to find as parts mules are probably the 7B53A time base and
2213/2215/2235 scopes, followed by the T900-series scopes.
Finding matched pairs is preferable to buying substitutes and having to
try to match them yourself, unless you have a curve tracer. Even then, you
will need to buy a couple dozen of the replacements to have a hope of
finding a matched pair (from what I see 2N5454 and 2N4416 are about $6-$10
each, so that's a substantial outlay). The parts on eBay are asking
$15/pair, which is lot less than you'll pay for a parts mule or a set of
unmatched subs.
-- Jeff Dutky
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Re: Sick TG501 Main 1Mhz ref not running.
Zen,
what about continuity where it shouldn't be connected?
-- Jeff Dutky
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Re: Sick TG501 Main 1Mhz ref not running.
Jeff,
I totally agree with you that this is a trivial oscillator. One of the reasons It has been driving me nuts not being able to get it to start. Getting it to start. There is continuity to all the places that there should be and the components check for value and the caps check ok for leakage. Leakage of the capacitors was checked with a Keithley 2450. I even went so far as to swap in a known good crystal. U100 was confirmed bad but the new one still test good on the breadboard. Pin 6 not quite high 3.6 V which would be a problem for and IC as that is below switching range.
It is driving me nuts I can't find where the 1.5V is going.
Zen
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Jeff Dutky Sent: Sunday, November 28, 2021 11:10 PM To: [email protected]Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running. Zen, Pardon me if this is a stupid question, but have you checked continuity around U100? I only ask because this is an apparently trivial oscillator, and the only reason I can think of for it not to work is that something is not connected correctly. Also, are you sure that the crystal is good? ¡ª Jeff Dutky
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465B NORM triggering question
Thanks to help on this forum, I just got my 465B going. I soon noticed something peculiar. With no signal on CH1 or CH2 and both CH1 and CH2 buttons pressed, both channels appear on the CRT with NORM trigger source and AUTO trigger mode, as expected. When I put a signal into CH1 or CH2, then the display disappears entirely (it can still appear in BEAM FIND mode). If I move the TRIG LEVEL control to an extreme such that the 'scope can no longer trigger on the applied signal, then the display reappears! Triggering on CH1, CH2, and LINE source work as expected. Triggering with only CH1 or CH2 selected (not both) works as expected.
It's not too hard to just flip the switch to CH1 or CH2, but it just seems odd that when there's a triggerable signal in NORM source and AUTO mode, nothing appears on the CRT.
Could this be caused by running unmatched JFETs in the trigger circuit, as discussed in the "465B no trigger" thread?
Halden
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Re: 492 spectrum analyzer sweep linearity
On Sun, Nov 28, 2021 at 11:16 PM, vk2bea wrote:
Yes, that was it. A bad diode (CR4051) in the 'shaper' network.
HUZZAH!
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Hi Michael and Jeff
Thanks for your comments and information!
At this point, I'm probably running an unmatched pair, one having been taken from circuit A and one from circuit B. Triggering works fine (exception in another post) for the calibration bar and a strong 40 MHz signal. I don't know if it's working perfectly because I haven't given it a challenging triggering situation. Do either of you know what tends to happen when one JFET operates on one side of the knee and the other on the other side of the knee?
I don't have a transistor curve tracer, but I could probably rig up something to hold Ids at 10.5 mA and see what happens when I apply a signal to the gate.
I sent an enquiry to Sphere and haven't heard back yet. I'm skeptical of buying semiconductors on ebay, but maybe I should just give it a try and ask to return them if they don't work.
Cheers
Halden
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Re: 492 spectrum analyzer sweep linearity
Yes, that was it. A bad diode (CR4051) in the 'shaper' network.
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Re: Sick TG501 Main 1Mhz ref not running.
Zen,
Pardon me if this is a stupid question, but have you checked continuity around U100? I only ask because this is an apparently trivial oscillator, and the only reason I can think of for it not to work is that something is not connected correctly.
Also, are you sure that the crystal is good?
¡ª Jeff Dutky
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Re: Help with an ailing 7D14
Well, thanks for the incentive in finding (finally) my 7D14, which I *thought* I had one of.
Turns out it was somewhat buried and someone had put a 7A12 tab on it rather than the correct one.? Nope, not me, came to me that way.? I was looking for the pull tab numbers to ID the plugin.
Not sure if the relays in this are plugin or not, they seem somewhat firmly attached, and I don't want to mess with it at the moment.? I did manage to read the relay numbers, though.? The diagram says SPST, single coil.? The number is 1X15B470A.? You might, just for a check, see if that's the right relay.
Mine doesn't count, but since I had a working 7D15, I let it sit for a while.? It is of unknown parentage other than it was probably known to be not working.
Looking at the form factor of the relays, I'm relatively sure I don't have any equivalents.? Haven't tried this in a while, but I may just poke through it a bit with it on an extender and see what I can find out.
Harvey
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On 11/28/2021 9:58 PM, k6whp wrote: Harvey, et al,
After going through considerable testing and reviewing a lot of marvelous advice and help from the group, I have come to an interim solution and am putting this problem to bed -- perhaps to research on a rainy day.
The problem was the overheating relays but I could not find the reason for the overheating except that possibly ALL the relays were defective. (Which I doubt.) If there was some deep-seated problem other than that, I'll look at it later. Meantime other projects awaited.
From the previous posts on this you will note that I discovered that cooling the plug-in board allowed it to operate hours on end without faulting on the display. So, succinctly, I was able to locate a source of 12 VDC (from the other existing fan board) and bolted in a three inch muffin fan I had lying around. The burn-in testing with all covers and running in a "normal" environment failed to fail, if you will. It ran for eight hours. In fact, I ran BOTH of the frequency counter plug-ins I had -- the 7D14 and 7D15 -- in the same unit and was counting input signals to beat the band.
The link below is to my blog which contains pictures for any who would find that beneficial
Thank you all for your time, patience, and considerable help!
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Re: 492 spectrum analyzer sweep linearity
I should have realized the implication of ... "when I measure the voltage at pin 6 with the trace at the right graticule it is close to the inverse of the voltage at the left most graticule".
This means that the push pull HV amplifier is working correctly and that the problem is either U2060 or the "shaper network". Presumably this 'shaper' is a way to introduce a nonlinearity to compensate for the tube but it is symmetrical and so should be mirrored around 0V.
I'll run a Spice simulation to see if I can better understand how it is supposed to work.
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Re: Help with an ailing 7D14
Harvey, et al,
After going through considerable testing and reviewing a lot of marvelous advice and help from the group, I have come to an interim solution and am putting this problem to bed -- perhaps to research on a rainy day.
The problem was the overheating relays but I could not find the reason for the overheating except that possibly ALL the relays were defective. (Which I doubt.) If there was some deep-seated problem other than that, I'll look at it later. Meantime other projects awaited.
From the previous posts on this you will note that I discovered that cooling the plug-in board allowed it to operate hours on end without faulting on the display. So, succinctly, I was able to locate a source of 12 VDC (from the other existing fan board) and bolted in a three inch muffin fan I had lying around.
The burn-in testing with all covers and running in a "normal" environment failed to fail, if you will. It ran for eight hours. In fact, I ran BOTH of the frequency counter plug-ins I had -- the 7D14 and 7D15 -- in the same unit and was counting input signals to beat the band.
The link below is to my blog which contains pictures for any who would find that beneficial
Thank you all for your time, patience, and considerable help!
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"
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Re: tek 2215 B delay time division knob removal
sorted,i didnt see the slot in the outer where it unscrews,used a pair of circlip pliers on it,came undone easy.
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Halden,
I have used a substitute FET in my 465B, but cannot recall the exact part number at this moment. I am fortunate enough to have a 576 curve tracer. So I could test and match a pair of modern parts to the originals. The critical ¡°matched¡± specification for the standard 2N4416 family of parts is defined in the TEKTRONIX SemiConductor Common Design Parts Catalog pg 7-7.
--
Michael Lynch
Dardanelle, AR
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Fabe
Dave Peterson
vk2bea
k6whp
Mlynch001