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Recreating an old board for the 7854
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I have a 7854 on the bench that is in need of a calibration. It is known to be off. I have most of what I need to calibrate the scope except the 67-0912-00 Analog test card. This card is used in the calibration to balance the thermal variants in the amplifiers. I have had a look out for this card for a while now and it seems to be quite illusive. There is some documentation that I am using to try and recreate the analog test board. I am sure that I will have a few questions along the way as per usual I am byteing off more then I can process. At the moment I am trying to wrap my head around the U430 U530 P109 buss network. Also It looks like U430 is a 74LS314 which looks like a cmos RAM chip.
Also if any one know how critical is this card to the calibration or should I skip this step and not worry about it. Scope is working well but I would like to do all requisite inspections for leaking caps and get the calibration touched up. Zen |
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There is an early prototype of that fixture. It allows the analog scope to function without any other digital cards. The prototype is a subset of 067-0912-00. It is pictured on Kurt R¡¯s tekwiki page for the 067-0912-00 fixture. It allows selecting Vert and Horiz display modes. It reduces the 7854 to a 7804N. Contact Dennis Tillman. I gave him a board a couple of years ago. He made an offer to this group to have a few made but nobody was interested at that time.
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Missed it by that much.
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Sent from my iThing, so please forgive typos and brevity. On Jul 20, 2021, at 12:13 PM, Clark Foley <clarkfoley@...> wrote: |
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On Tue, Jul 20, 2021 at 09:12 PM, Clark Foley wrote:
Since we're at it: It's not 8 latches: There are 8 D-type flip-flops in a '374. Latches pass the input with one control level (the output follows the input, no clock involved) and latch their input value with the control at the other level, much like an analog sample and hold. Compare 7475 (quad latch). The '374 uses a clock to transfer the data at the D-inputs to the complementary outputs. Raymond |
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Thanks for all the help.
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I have about 80% finished with the schematic. I need to find a replacement for the 2N5769 The documentation says this was a "Switching Transistor" but it does not say the switching frequency. But that is the next hurdle that needs to be cleared. I will post the schematic and the board layout when it is finished to make sure I did not make any errors. Also need to get the pin outs for P190. At the moment P190 looks like it is the board edge connector. All advise is welcome and thanks in advance. -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Raymond Domp Frank Sent: Tuesday, July 20, 2021 3:28 PM To: [email protected] Subject: Re: [TekScopes] Recreating an old board for the 7854 On Tue, Jul 20, 2021 at 09:12 PM, Clark Foley wrote: Since we're at it: It's not 8 latches: There are 8 D-type flip-flops in a '374. Latches pass the input with one control level (the output follows the input, no clock involved) and latch their input value with the control at the other level, much like an analog sample and hold. Compare 7475 (quad latch). The '374 uses a clock to transfer the data at the D-inputs to the complementary outputs. Raymond |
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You guys aren't as Smart as you think you are!? ? ? ? ? ? Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Tom Lee <tomlee@...> Date: 7/20/21 12:17 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Recreating an old board for the 7854 Missed it by that much.Sent from my iThing, so please forgive typos and brevity.> On Jul 20, 2021, at 12:13 PM, Clark Foley <clarkfoley@...> wrote:> > ?Would you believe octal latches? Sorry about that, Chief.> > > > >
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Well, actress Barbara Feldon is still alive? evidently.? ?She's 88, though, so not nearly as hot as she was in Get Smart.? ? ? ?Jim?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Clark Foley <clarkfoley@...> Date: 7/20/21 12:49 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Recreating an old board for the 7854 Where is Agent 99 when you need her!
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A web search shows Frequency as 500 MHz as guaranteed minimum.
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Glenn On 7/20/2021 3:49 PM, Zentronics42@... wrote:
Thanks for all the help. --
----------------------------------------------------------------------- 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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That was the number I was unable to find. I had a feeling these needed to be fast as they are in the trigger circuit and the 7854 is a 400 Mhz frame. Test triggering to 500 Mhz is what I was expecting maybe even higher. Good news is as this is a from scratch board design package does not matter as I will be ordering parts. So for this spot I need lowish Vce and fast.
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Ill keep working on the boards. When the design is checked and tested If there is any interest in these let me know. Not sure how many out there want to tackle a full cal of a 7854. Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Glenn Little Sent: Tuesday, July 20, 2021 4:05 PM To: [email protected] Subject: Re: [TekScopes] Recreating an old board for the 7854 A web search shows Frequency as 500 MHz as guaranteed minimum. Glenn On 7/20/2021 3:49 PM, Zentronics42@... wrote: Thanks for all the help.-- ----------------------------------------------------------------------- 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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Looks like a suitable new chip would be this
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Vce - 25Vdc Hfe 120-240 Frequency - 800 Mhz -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Glenn Little Sent: Tuesday, July 20, 2021 4:05 PM To: [email protected] Subject: Re: [TekScopes] Recreating an old board for the 7854 A web search shows Frequency as 500 MHz as guaranteed minimum. Glenn On 7/20/2021 3:49 PM, Zentronics42@... wrote: Thanks for all the help.-- ----------------------------------------------------------------------- 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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Time for the Cone of Silence before we get the OT warning!
Now back to the 7854. I use the board to run my analog backup 7854 parts. It has no Max, I mean smarts, in it. I kludged in 7k readout board and now I have a fully functional 7804. Some of the boards are early prototype boards and some from different production runs. Think of Johnny Cash¡¯s ¡°One Piece At A Time.¡± No fins on it though! |
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Any chance there is high rez photos of a production analog test board? I have only seen the scan in the manual and I have some questions about layout and locations. Like of the BNC connector. I can get measurements off the Digital board cause they share dimensions. But there is a pin connector and a BNC connector I have some questions about where they go and why they are there.
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Zen -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Clark Foley Sent: Tuesday, July 20, 2021 4:23 PM To: [email protected] Subject: Re: [TekScopes] Recreating an old board for the 7854 Time for the Cone of Silence before we get the OT warning! Now back to the 7854. I use the board to run my analog backup 7854 parts. It has no Max, I mean smarts, in it. I kludged in 7k readout board and now I have a fully functional 7804. Some of the boards are early prototype boards and some from different production runs. Think of Johnny Cash¡¯s ¡°One Piece At A Time.¡± No fins on it though! |
Raymond Domp Frank
GeorgeP
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