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Tektronix 2236 Seven-Segment Display 670-7423-00
Hello and need help for this part.
I¡¯m looking for the vfd display used in the counter timer of the 2236. Part number is 670-7423-01 for the small board and 150-1110-00 for just the display tube. The display tube also known as a Noritake Itron p/n FG94C1. |
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Tek 7904 random redout and noisy pot
dear all,
I dropped my 7904 from its cart last week. Up to the moment the identified losses are: 1- broken 7B85 time/div pot and cal/uncal knob and rod 2- Very noisy redout pot 3- Garbage number showing on the top rows of readout 4 - No information shown in redout bottom lines. Probably issues 2 to 4 were already there, since I had almost no time to play with this instrument since I bought it some weeks ago. I was thinkin to start with the easiest issue (2) which would require spraying a little of Deoxit Fader on the pot's wiper but, to my surprise, it seems impossible to get there see (/g/TekScopes/album?id=302608). So I would like to know if there are known practices of what to do in situations like this one. I have read somewhere that one possible solution is to drill a 1/8" hole on the case to allow sprying the cleaner than later closing the hole with some inert putty. Is this an "approved solution"? Also, I intend to reseat (with some Deoxit) all the IC's and connectors of the redout board. Any other recommendations concerning the random readout characters? Is there a known fault that would cause the entire bottom readout line (all four fields) to be missing? Thank you very much, Roger |
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Re: 067-0587-01 amplitude pot wire connections
Looking at that pot from the back, on mine the center pot has the left tab grounded, the center tab has a wire with white insulation and a violet stripe, and the right tab has a wire with red insulation and a wire with red insulation and a brown(?) stripe.
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HTH, Barry - N4BUQ ----- Original Message -----
From: "Rogerio O via groups.io" <rodd414@...> Hi to everybody. |
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067-0587-01 amplitude pot wire connections
Hi to everybody.
I bought a 067-0587-01 on Epay and, for the moment, I have two issues: 1- One red wire going to the amplitude Pot is "floating" as shown in photo (/g/TekScopes/album?id=302607). I tried to figure out where it should be going following the schematics but I couldn't find any pot terminal having two connections. Each terminal seems to be connected to ground (local terminal), +15V or -15V. Can anyone be kind enough to open its unit and tell me where this wire is going to? 2- One of the clear plastic press "button" from the REP RATE switch is broken and it flies like a rocket when it goes from "pressed" to "non pressed" . I was lucky enough to find two times but Murphy is always around... Is there a way to disassemble it to try to glue it in place? Any other suggestion? Thanks to all, Roger |
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Added photo album 067-0587-01
#photo-notice
Group Notification
Rogerio O <rodd414@...> added the photo album 067-0587-01 ( /g/TekScopes/album?id=302607 ) : one wire connection is broken
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Re: 7A13 overshoot
On Thu, May 22, 2025 at 06:38 AM, n4buq wrote:
Looking again: the offending relay was K490, which is the bandpass limiting relay; I misread the numbers on the board since I wasn't using a flashlight. From the description and schematic, K480 bandpass-limits the trigger, and I believe that was added in later revisions as you pointed out. I was pretty sure it was the lower rear relay (490), not the middle one (480), so thanks for making me take a second look! I'm only documenting this for the next poor slob who runs into it, which might well be me. thanks, Adam |
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Re: 7A13 overshoot
I had opened an older version of the schematic which doesn't have that relay. I see it now on the later versions. Apologies for the interruption.
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Barry - N4BUQ On May 22, 2025, at 05:52 , n4buq via groups.io <n4buq@...>I'm looking at the manual on Tekwiki for B200000 up, and K480 is at the very |
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Re: 7A13 overshoot
On May 22, 2025, at 05:52 , n4buq via groups.io <n4buq@...> wrote:I'm looking at the manual on Tekwiki for B200000 up, and K480 is at the very back center of the output amplifier board on the labeled component photo. I need to find it on the schematic and see if this makes sense. Glad you found/fixed it. Those relays are definitely a pain.I should have taken before-and-after photos of the trace, but I'll probably have another opportunity, the way these relays are. thanks, Adam |
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2784 Spectrum Analyzer
Hi,
my 2784 Spec lost all the data, because Li- Battery has not been changed last fifteen years. Now, when I power the Spectrum Analyzer the display shows me a 2782 . How can I fix this problem? I can only tune up to 33 Ghz instead of 40 Ghz. I didn't found anything in the manuals. Juergen |
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Re: 7A13 overshoot
Hi Adam,
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Was that, perhaps, K48 or K490? I don't see a K480 but I might be looking at a different version of the manual. Glad you found/fixed it. Those relays are definitely a pain. Barry - N4BUQ Well, after replacing C187 and C163 with no improvement, it turns out that I |
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Re: 7A13 overshoot
Well, after replacing C187 and C163 with no improvement, it turns out that I overlooked relay K480. Swapping with my known good relay immediately got rid of the giant hump at the front of the pulse, and the 7A13 rise time is ~3 ns after a crude HF compensation adjustment.
I drilled the bad relay with a Dremel, added some contact cleaner and alcohol, and exercised it for a while with a pulser and 14V incandescent lamp load. Now it works too, and I feel like a dope. thanks, Adam |
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Re: Tektronix 494P 1st LO and Frequency failure(s)
no if 1st if osc...I would do in this order the following..Check...
Power supplies, good, not close but right on the money. See john miles notes. Check there is any yig output , i.e.1st IF is on front panel.2 to 6GHz. Check the aux synth 200MHz is running and the output going to the harmonic mixer is good. There should be around 40MHz output from harmonic mixer with yig running and 200 MHz running. The cpu counts this 40MHz output to conrol the course loop yig control. You seem to hve 0 count. With manual, check the aux synth 200 MHz osc is running and you have a yig output into harmonic mixer. The cpu counts this 40MHz (after dividing by 100) and you seem to have a 0 count. |
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Re: Tektronix 494P 1st LO and Frequency failure(s)
(Un)fortunately enough, the frequency control section is one area that I've seldom/never had to work on, myself.
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Since you (Federico) have extender boards, I think I'd try applying a combination of R134a or similar coolant spray (not sure what 's available in the EU, though) and a heat gun or hair dryer. If you are able to identify the general area where the problem is occurring, a Q-tip soaked in R134a is a good next step. -- john, KE5FX -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Roy Thistle via groups.io Sent: Tuesday, May 20, 2025 9:57 AM To: [email protected] Subject: Re: [TekScopes] Tektronix 494P 1st LO and Frequency failure(s) Hi Federico If you search the forum messages for 'John Miles' you may find some relevant information. Ciao Federico, se cerchi "John Miles" nei messaggi di questo forum, magari trovi qualche informazione utile -- Roy Thistle |
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Re: Tektronix 494P 1st LO and Frequency failure(s)
While it may not matter for this application, the inductance of film resistors may be different depending on type, value and trimming method both from one resistor to another as well as to carbon composition.
________________________________ From: [email protected] <[email protected]> on behalf of Richard Knoppow via groups.io <dickburk@...> Sent: Tuesday, May 20, 2025 4:53:59 PM To: [email protected] <[email protected]> Subject: Re: [TekScopes] Tektronix 494P 1st LO and Frequency failure(s) FWIW Allen-Bradley carbon composition resistors are identical with Ohmite. For some reason AB marketed through Ohmite. Same with AB and Ohmite pots.They are about the best of the carbon comp resistors but despite this they do drift. Usually upward and usually higher values drift proportionally to value. It is not reversible. While heat may accelerate the drift the resistors reportedly drift on the shelf. Carbon and metal film resistors are far more stable, essentially neither drift with age or use. Carbon comp resistors have no real advantage over film resistors, there is no good reason to use them. BTW a little OT, IRC advertised heavily but I almost never see any in old gear. I don't remember their having a bad reputation and they don't seem to have been more expensive than AB/Ohmite, so a bit of a puzzle.Sent from my Galaxy -------- Original message --------From: "Ulf Kylenfall via <ulf_r_k@...> Date: 5/20/25 1:27 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Tektronix 494P 1st LO and Frequency failure(s) I have repaired a 494 as well as a 2756. Apart from what KE5FX writes in his document there are a few other things to look out for.On several PCB's there are High Ohm carbon mass resistors made by AllenBradley. Several MegaOhms.During my attempts to repair the analyzers, I have found these resistors to age/drift much above and outside their original some cases more than 50%. And these resistors can be found in places where frequencies are set.When trouble-shooting using the built in procedures I could get the instrumenst to work only to get unlock messages the nexttime one of the instruments was turned on. Eventually, I replaced all of them with 1% metal film resistors. After havingdone that the problems disappeared.Ulf KylenfallSM6GXV |
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Re: Tektronix 494P 1st LO and Frequency failure(s)
Carbon composition resistors have their place where where short duration, high energy pulses are involved.
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Film resistors just open up. Carbon composition resistors increase in value with age, probably due to the way they are made. Carbon granules, in a binder material are encase in a material like Bakelite. One crack where the lead exits the case and moisture enters, swelling the binder and the resistance goes up. Glenn On 5/20/2025 5:53 PM, Richard Knoppow via groups.io wrote:
FWIW Allen-Bradley carbon composition resistors are identical with Ohmite.? For some reason AB marketed through Ohmite. Same with AB and Ohmite pots.They are about the best of the carbon comp resistors but despite this they do drift.? Usually upward and usually higher values drift proportionally to value.? It is not reversible.? While heat may accelerate the drift the resistors reportedly drift on the shelf.??Carbon and metal film resistors are far more stable, essentially neither drift with age or use.? ?Carbon comp resistors have no real advantage over film resistors, there is no good reason to use them.? ?BTW a little OT,? IRC advertised heavily but I almost never see any in old gear.? I don't remember their having a bad reputation and they don't seem to have been more expensive than AB/Ohmite, so a bit of a puzzle.Sent from my Galaxy --
----------------------------------------------------------------------- Glenn Little ARRL Technical Specialist QCWA LM 28417 Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license" |
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Re: Tektronix 494P 1st LO and Frequency failure(s)
FWIW Allen-Bradley carbon composition resistors are identical with Ohmite.? For some reason AB marketed through Ohmite. Same with AB and Ohmite pots.They are about the best of the carbon comp resistors but despite this they do drift.? Usually upward and usually higher values drift proportionally to value.? It is not reversible.? While heat may accelerate the drift the resistors reportedly drift on the shelf.??Carbon and metal film resistors are far more stable, essentially neither drift with age or use.? ?Carbon comp resistors have no real advantage over film resistors, there is no good reason to use them.? ?BTW a little OT,? IRC advertised heavily but I almost never see any in old gear.? I don't remember their having a bad reputation and they don't seem to have been more expensive than AB/Ohmite, so a bit of a puzzle.Sent from my Galaxy
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-------- Original message --------From: "Ulf Kylenfall via groups.io" <ulf_r_k@...> Date: 5/20/25 1:27 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Tektronix 494P 1st LO and Frequency failure(s) I have repaired a 494 as well as a 2756. Apart from what KE5FX writes in his document there are a few other things to look out for.On several PCB's there are High Ohm carbon mass resistors made by AllenBradley. Several MegaOhms.During my attempts to repair the analyzers, I have found these resistors to age/drift much above and outside their original specification.In some cases more than 50%. And these resistors can be found in places where frequencies are set.When trouble-shooting using the built in procedures I could get the instrumenst to work only to get unlock messages the nexttime one of the instruments was turned on.? Eventually, I replaced all of them with 1% metal film resistors. After havingdone that the problems disappeared.Ulf KylenfallSM6GXV
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Re: Tektronix 494P 1st LO and Frequency failure(s)
I have repaired a 494 as well as a 2756. Apart from what KE5FX writes in his document there are a few other things to look out for.
On several PCB's there are High Ohm carbon mass resistors made by AllenBradley. Several MegaOhms. During my attempts to repair the analyzers, I have found these resistors to age/drift much above and outside their original specification. In some cases more than 50%. And these resistors can be found in places where frequencies are set. When trouble-shooting using the built in procedures I could get the instrumenst to work only to get unlock messages the next time one of the instruments was turned on. Eventually, I replaced all of them with 1% metal film resistors. After having done that the problems disappeared. Ulf Kylenfall SM6GXV |
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