Date   

Re: 7854 Repair & Restoration

Brian Bloom
 

I would consider reflowing all of the solder joints around U50 whether
>a detailed inspection reveals a problem or not as long as the board
>removed.

I will go ahead and reflow all of them then. I'll use a lead that matches U50/U150 in diameter to test out the mini berg sockets quickly.





>>It's too bad that I didn't get in on the whole AM503 & probe market >>while they were going for $50 each...

>P6021 and P6022 AC current probes regularly sell for under $200 but
>they are somewhat fragile so finding a good one might be a problem.
>They require either the passive termination they originally came with,
>a Tektronix type 134 current probe amplifier, or a 7A14.

I spoke too soon!! I picked up an AM503/TM503 for $50!! I really just bought it because I wanted the TM503. The AM503 is a useful bonus! Now I need to find a deal on an A6302/A6312.......

I also scored my 7S14!!! No more unsuccessfully attempting to obtain a 7T11A!! I also got a 7A22 for a steal that's in better condition than any of the lot that just sold last week. Now 2 of my 485's are fixed....

((Sorry if it seems like I'm bragging... I'm just excited and feel the need to tell someone! None of my friends here even know what an opamp is.....)

This is a fantastic weekend! Now to sort out the 7854 (successfully......)


Re: Tek 2247A [SN B029000] Recap and diode part list ?

Michael
 

If the 2247A service manual is like the 2465B service manual, it does not
distinguish between aluminium and tantalum capacitors. Nor do they distinguish
between axial and radial or polar and bipolar. All of those distinctions have
to be determined by manual inspection of the boards. Unless, you can tell from
the Tektronix part number, which is usually not very informative.

When I recapped my 2465BCT, I made a complete list, but then once I had the
boards out I had to refine my list to take those considerations into account.
Unless someone else has a list they actually used, recapping can take a while
due to the need for multiple, serial orders.

The problem is that you usually don't want to take these boards out more than
necessary and for some of them it is had to inspect the parts without removing
the boards. For the 2465BCT, the processor board, the main power and the high
voltage boards can be inspected fairly easily. The power supply boards, option
boards, etc., not so much.


Mike

Based on service manual for 2247A, I can't  find Tantalum cap, am I missing something?


Re: 7854 RAM card upgrade only - any interest?

bogroca
 

Yes David, I you already provided them to me, but I have no means to fabricate them.


If ever there will be "somebody ;-) " able and willing, just put me down for 2 pairs (unbroken).


Regards,
Bogdan


Re: Tek 2247A [SN B029000] Recap and diode part list ?

Darren Ting
 

Hi Jerry,

Based on service manual for 2247A, I can't  find Tantalum cap, am I missing something?
Old thread mention my issues could be Q2209 and Q2210 C-E shorted, quick measures give me 100kohm and above for any test point on this two Qs.  so shorted C-E unlikely.

Measure on-board C2210 give  7.2uF rather  than  4.7uF.  Look very suspicious




From: "jerry massengale @jmassen418 [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Sunday, 13 March 2016, 22:10
Subject: Re: [TekScopes] Tek 2247A [SN B029000] Recap and diode part list ?

  Darren,

I look for caps that show signs of heat, either a swollen top or a darkened case. Surface mount aluminum caps get replaced always. Tantalum caps that are used at greater than 50% of their rating get replaced.

I would not replace any diode without cause.

Jerry Massengale

-----Original Message-----
From: TING HENG CHING darren_ting_hc@... [TekScopes] <TekScopes@...>
To: TekScopes <TekScopes@...>
Sent: Sun, Mar 13, 2016 8:38 am
Subject: [TekScopes] Tek 2247A [SN B029000] Recap and diode part list ?

Does anyone keep a list of parts for recap power supply board [A18] on 2247A ?

I toke out the power supply board [A18], but can not find any diode mark as ZM or ZS which known to have issue and recommended to replace as well.
All I can find is mark as Motorola instead, diode issue not applicable to B290000 and later?
My unit based on IC date code should be late in 1994.
It run fine but decided to recap before it fail, more than 20 years old caps sound really scary.
However, I found burn mark on my power board near area :- A18CR2228
A18R2255A18R2275A18R2254A18CR2227
Something went WRONG to my power supply board? FAN is running fine.

Could someone advise related to burn mark? should I worry? look scary to me





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[Non-text portions of this message have been removed]


Re: OT 10Mhz references

Craig Sawyers <c.sawyers@...>
 

Yeah, I read that story when I googled "time-nuts". Cool stuff. It got me to wondering: If (as he
demonstrated) time dilates with distance from the gravity well of the earth, doesn't that make GPS
based reference standards inherently less accurate than earth based ones *on earth*?
GPS has to be corrected for both special and general relativity. Special because the satellites are
not geosynchronous, and are moving relative to a ground observer, and general because of the gravity
well. On the one hand this is deterministic, and on the other hand there needs to be constant
tweaking because tides and weather and so forth needs to be taken account of.

Without such correction, your position would drift by 10km per day and render GPS useless.

The Allen deviation of GPS time derived clocks has to be measured with respect to a ground reference
as you say, which itself has an Allen deviation less than that of GPS itself.


Re: Tek 2247A [SN B029000] Recap and diode part list ?

 

Darren,


I look for caps that show signs of heat, either a swollen top or a darkened case. Surface mount aluminum caps get replaced always. Tantalum caps that are used at greater than 50% of their rating get replaced.


I would not replace any diode without cause.


Jerry Massengale

-----Original Message-----
From: TING HENG CHING darren_ting_hc@... [TekScopes] <TekScopes@...>
To: TekScopes <TekScopes@...>
Sent: Sun, Mar 13, 2016 8:38 am
Subject: [TekScopes] Tek 2247A [SN B029000] Recap and diode part list ?








Does anyone keep a list of parts for recap power supply board [A18] on 2247A ?

I toke out the power supply board [A18], but can not find any diode mark as ZM or ZS which known to have issue and recommended to replace as well.
All I can find is mark as Motorola instead, diode issue not applicable to B290000 and later?
My unit based on IC date code should be late in 1994.
It run fine but decided to recap before it fail, more than 20 years old caps sound really scary.
However, I found burn mark on my power board near area :- A18CR2228
A18R2255A18R2275A18R2254A18CR2227
Something went WRONG to my power supply board? FAN is running fine.

Could someone advise related to burn mark? should I worry? look scary to me

[Non-text portions of this message have been removed]









[Non-text portions of this message have been removed]


Re: OT 10Mhz references

Torch Fireman
 

Dennis,-

Yeah, I read that story when I googled "time-nuts". Cool stuff. It got me to wondering: If (as he demonstrated) time dilates with distance from the gravity well of the earth, doesn't that make GPS based reference standards inherently less accurate than earth based ones *on earth*? I'm sure the smart folks worked out some sort of compensation for long-term effects. Perhaps the GPS birds are receiving corrections from a ground station (in which case, calibrating a ground-based oscillator to the bird would make it run faster than it should). Or perhaps the GPS oscillators are running at a slightly slower rate than earth-based ones, technically making them inaccurate at their actual orbit.

Personally, back in the real world of doctor's appointments and bus schedules, my house standard is a wrist-watch that sets itself from the radio signal from Boulder every night. But it was out by an hour this morning, since it was made before the powers that be changed the DST dates, making the automatic DST setting useless. So I had to manually correct the hour. When I set the clocks in my cars and house to DST this morning, I used the watch as a reference and now all my clocks are within 0.5 minutes of that signal, which should get me to work on time tomorrow morning. ;-)

On 12/03/2016 10:51 PM, 'Dennis Tillman' @Dennis_Tillman_W7pF [TekScopes] wrote:

he took his kids camping for
a weekend to Paradise which is 7,000 feet up on Mt. Rainier near us in
Seattle. Of course Tom does things a little differently than the rest of us.
He brought 3 HP Cesium Standards up with him on the trip. When he got back
down he compared the time dilation that occurred between the three Cesium
Standards up on the mountain for the weekend with the ones he kept in his
house which is almost at sea level. He then calculated the expected time
difference based on General Relativity.


Tek 2247A [SN B029000] Recap and diode part list ?

Darren Ting
 

Does anyone  keep a list of  parts for  recap power supply board [A18] on 2247A ?

I toke out the power supply  board [A18],  but can not find any diode mark as ZM or ZS which known to have issue and recommended to replace as well. 
All I can find is mark as Motorola instead,  diode issue not applicable to B290000 and later? 
My unit based on IC date code should be late in 1994.
It run fine but decided to recap before it fail, more than 20 years old  caps sound really scary.
However,  I found burn mark on my power board near area :- A18CR2228
A18R2255A18R2275A18R2254A18CR2227
Something went WRONG to my power supply board? FAN is running fine.

Could someone advise related to burn mark? should I worry? look scary to me

[Non-text portions of this message have been removed]


Re: 2465B Recap Project

Michael
 

John,

John, I recently completely recapped all boards on my 2465BCT, s/n B010xxx so
my parts list should work for you. I did not replace the tantalum capacitors,
but my list identifies them. I ordered all parts from Mouser. I included the
Mouser cost, sometimes I hit a volume breakpoint but usually not.

A1 Main

A1 C0102 290-0973-00 100uF 20% 25VDC UPW1V101MPD 100uF 35V 20% 105c 0.24
A1 C0107 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0114 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0121 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0130 290-0776-01 22uF 20% 10V UPW1E220MDD 22uF 25V 20% 105c 0.16
A1 C0152 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0185 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0218 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0221 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0307 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0325 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0335 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0512 290-0246-00 3.3uF 10% 15V Axial Tantalum
A1 C0536 290-0246-00 3.3uF 10% 15V Axial Tantalum
A1 C0723 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0731 290-0944-01 220uF 20% 10V UPW1C221MPD 220uF 16V 20% 105c 0.25
A1 C0732 290-0944-01 220uF 20% 10V UPW1C221MPD 220uF 16V 20% 105c 0.25
A1 C0733 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0738 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0740 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A1 C0957 290-0804-00 10uF +50-20% 25V UPW1V100MDD 10uF 35V 20% 105c 0.16
A1 C0977 290-0246-00 3.3uF 10% 15V Axial Tantalum


A2A1 Regulator

A2A1 C1016 282-1222-00 0.068uF 20% 250V X2 Film ECQ-U2A683KL 0.068uF 250V 10% 100c 0.47
A2A1 C1018 282-1222-00 0.068uF 20% 250V X2 Film ECQ-U2A683KL 0.068uF 250V 10% 100c 0.47

A2A1 C1220 290-0939-00 10uF +100-10% 100V UPW2A100MED 10uF 100V 20% 105c 0.23
A2A1 C1240 290-0939-00 10uF +100-10% 100V UPW2A100MED 10uF 100V 20% 105c 0.23
A2A1 C1260 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105c 0.24
A2A1 C1274 290-0778-00 1uF 20% 50V Bipolar UEP2A010MDD 1uF 100V 20% 105C 0.51
A2A1 C1280 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105c 0.24
A2A1 C1291 290-0778-00 1uF 20% 50V Bipolar UEP2A010MDD 1uF 100V 20% 105C 0.51
A2A1 C1292 290-0778-01 1uF +20% 50V Bipolar UEP2A010MDD 1uF 100V 20% 105C 0.51
A2A1 C1300 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105c 0.24
A2A1 C1330 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105c 0.24
A2A1 C1350 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105c 0.24
A2A1 C1400 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A2A1 C1402 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212

A2A1 R1010 301-0150-00 15 Ohm 5% 250V 0.5W Film PR01000101509JR500 15 350V 5% 1W 0.18
A2A1 R1019 301-0150-00 15 Ohm 5% 250V 0.5W Film PR01000101509JR500 15 350V 5% 1W 0.18
A2A1 R1018 301-0300-00 30 Ohm 5% 250V 0.5W Film PR01000103009JR500 30 350V 5% 1W 0.18
A2A1 R1011 315-0560-00 56 Ohm 5% 250V 0.25W Film PR01000105609JR500 56 350V 5% 1W 0.18
A2A1 R1012 315-0560-00 56 Ohm 5% 250V 0.25W Film PR01000105609JR500 56 350V 5% 1W 0.18
A2A1 R1016 301-0680-00 68 Ohm 5% 250V 0.5W Film PR01000106809JR500 68 350V 5% 1W 0.18
A2A1 R1013 315-0683-00 68k Ohm 5% 250V 0.25V Film PR01000104703JR500 68k 350V 5% 1W 0.18
A2A2 R1017 315-0474-00 470K Ohm 5% 250V 0.25W Film PR01000104703JR500 470k 350V 5% 1W 0.18

A3 Inverter

A3 C1020 285-1192-00 0.0022uF 20% 250V X2 Film ECQ-U2A222KL 0.0022uF 250V 10% 100C 0.51
A3 C1051 285-1192-00 0.0022uF 20% 250V X2 Film ECQ-U2A222KL 0.0022uF 250V 10% 100C 0.51
A3 C1052 285-1196-00 0.01uF 20% 250V X2 Film ECQ-U2A103KL 0.01uF 250V 10% 100C 0.49

A3 C1021 290-0971-00 290uF +50-10% 200V Axial TVX2D331MDD 330uF 200V 20% 85C 7.19
A3 C1022 290-0971-00 290uF +50-10% 200V Axial TVX2D331MDD 330uF 200V 20% 85C 7.19
A3 C1025 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105C 0.24
A3 C1034 290-0524-00 4.7uF 20% 10V Radial Tantalum
A3 C1066 290-0782-01 4.7uF 20% 35V UPW1H4R7MDD 4.7uF 50V 20% 105C 0.16
A3 C1072 290-0806-00 3.3uF +75-10% 350V UPW2V3R3MPD 3.3uF 350V 20% 105C 0.53
A3 C1101 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105C 0.24
A3 C1102 290-0942-00 100uF +100-10% 25V UPW1V101MPD 100uF 35V 20% 105C 0.24
A3 C1110 290-0800-00 250uF +100-10% 20V UPW1H331MPD 330uF 50V 20% 105C 0.51
A3 C1111 290-0800-00 250uF +100-10% 20V UPW1H331MPD 330uF 50V 20% 105C 0.51
A3 C1112 290-0782-01 4.7uF 20% 35V UPW1H4R7MDD 4.7uF 50V 20% 105C 0.16
A3 C1113 290-0798-00 180uF +100-10% 40V UPW1H331MPD 330uF 50V 20% 105C 0.51
A3 C1114 290-0800-00 250uF +100-10% 20V UPW1H331MPD 330uF 50V 20% 105C 0.51
A3 C1115 290-0800-00 250uF +100-10% 20V UPW1H331MPD 330uF 50V 20% 105C 0.51
A3 C1116 290-0798-00 180uF +100-10% 40V UPW1H331MPD 330uF 50V 20% 105C 0.51
A3 C1120 290-0939-00 10uF +100-10% 100V UPW2A100MED 10uF 100V 20% 105C 0.23
A3 C1130 290-0939-00 10uF +100-10% 100V UPW2A100MED 10uF 100V 20% 105C 0.23
A3 C1132 290-0880-00 10uF +50-10% 160V UPW2C100MPD 10uF 160V 20% 105C 0.39

Note: C1115 and C1132 are reversed in the service manual layout. Double check actual values when replacing.

Note: C1021 and C1022 are axial, but the originals have much longer leads than available now.
The leads on the replacements will need to be extended. I cut the leads from the original
and soldered them to the replacement leads. That is tricky to keep them from unsoldering.
Now, I might use a very fine wire thread and bind the leads together then solder over that
so the wire thread will hold it together if the solder gets too hot.

A5 (670-9052-02) Digital Control

A5 C2010 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A5 C2011 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A5 C2113 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A5 C2350 290-0527-00 15uF 20% 20V Radial Tantalum
A5 C2420 290-0943-02 47uF 20% 25V UHV1V470MDD 47uF 35V 20% 105c 0.212
A5 C2470 290-0527-00 15uF 20% 20V Radial Tantalum


Mike





Does anyone have a list of capacitors they have purchased to recap the A1,
A1A2, A3 and A5 boards or an early 2465B (Serial number around B015000)? I
would like to use the most appropriate caps.

Thanks, John



--
Best regards,
2465bct mailto:2465bct@...


Raindrops on a Scope

 


Re: 2465B Recap Project

 

Sorry, the link to my drop box didn't go through. I can send the file as an email attachment if you want.

From: "machine guy @Mac [TekScopes]" <TekScopes@...>
To: "TekScopes@..." <TekScopes@...>
Sent: Sunday, March 13, 2016 1:42 AM
Subject: Re: [TekScopes] 2465B Recap Project

  There is a spread sheet titled 2465LVPS_ReCap, A1 recap-parts.xls  in the files section of this group: https://xa.yimg.com/df/TekScopes/2465LVPS_ReCap%2C+A1+recap-parts.xls?token=1s2zGdUs8uLqaY4adDMIi0BtEwad098_T3-9EyEnrGLrzPcsRkKarWeWnA3qx20QZHXuNzi34UlPwxzMKCnOUhti8d28Xd9g0fkgDCyPhgpqWxf2yyt8XSjiKkK7wA88o-c4-PZS8A&type=download
I used this spread sheet and updated it to include caps for the A5 board and buy from Digikey.  Here is a link to my dropbox containing that update: 2465 CAPS

From: "John Dickens jake_117_dickens@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Saturday, March 12, 2016 11:58 PM
Subject: [TekScopes] 2465B Recap Project

 
Does anyone have a list of capacitors they have purchased to recap the A1, A1A2, A3 and A5 boards or an early 2465B (Serial number around B015000)? I would like to use the most appropriate caps.

Thanks, John #yiv0345349574 #yiv0345349574 -- #yiv0345349574ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv0345349574 #yiv0345349574ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv0345349574 #yiv0345349574ygrp-mkp #yiv0345349574hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv0345349574 #yiv0345349574ygrp-mkp #yiv0345349574ads {margin-bottom:10px;}#yiv0345349574 #yiv0345349574ygrp-mkp .yiv0345349574ad {padding:0 0;}#yiv0345349574 #yiv0345349574ygrp-mkp .yiv0345349574ad p {margin:0;}#yiv0345349574 #yiv0345349574ygrp-mkp .yiv0345349574ad a {color:#0000ff;text-decoration:none;}#yiv0345349574 #yiv0345349574ygrp-sponsor #yiv0345349574ygrp-lc {font-family:Arial;}#yiv0345349574 #yiv0345349574ygrp-sponsor #yiv0345349574ygrp-lc #yiv0345349574hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv0345349574 #yiv0345349574ygrp-sponsor #yiv0345349574ygrp-lc .yiv0345349574ad {margin-bottom:10px;padding:0 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[Non-text portions of this message have been removed]

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Re: 2465B Recap Project

 

There is a spread sheet titled 2465LVPS_ReCap, A1 recap-parts.xls  in the files section of this group: https://xa.yimg.com/df/TekScopes/2465LVPS_ReCap%2C+A1+recap-parts.xls?token=1s2zGdUs8uLqaY4adDMIi0BtEwad098_T3-9EyEnrGLrzPcsRkKarWeWnA3qx20QZHXuNzi34UlPwxzMKCnOUhti8d28Xd9g0fkgDCyPhgpqWxf2yyt8XSjiKkK7wA88o-c4-PZS8A&type=download
I used this spread sheet and updated it to include caps for the A5 board and buy from Digikey.  Here is a link to my dropbox containing that update: 2465 CAPS

From: "John Dickens jake_117_dickens@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Saturday, March 12, 2016 11:58 PM
Subject: [TekScopes] 2465B Recap Project

 
Does anyone have a list of capacitors they have purchased to recap the A1, A1A2, A3 and A5 boards or an early 2465B (Serial number around B015000)? I would like to use the most appropriate caps.

Thanks, John #yiv0345349574 #yiv0345349574 -- #yiv0345349574ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv0345349574 #yiv0345349574ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv0345349574 #yiv0345349574ygrp-mkp #yiv0345349574hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv0345349574 #yiv0345349574ygrp-mkp #yiv0345349574ads {margin-bottom:10px;}#yiv0345349574 #yiv0345349574ygrp-mkp .yiv0345349574ad {padding:0 0;}#yiv0345349574 #yiv0345349574ygrp-mkp .yiv0345349574ad p {margin:0;}#yiv0345349574 #yiv0345349574ygrp-mkp .yiv0345349574ad a {color:#0000ff;text-decoration:none;}#yiv0345349574 #yiv0345349574ygrp-sponsor #yiv0345349574ygrp-lc {font-family:Arial;}#yiv0345349574 #yiv0345349574ygrp-sponsor #yiv0345349574ygrp-lc #yiv0345349574hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv0345349574 #yiv0345349574ygrp-sponsor #yiv0345349574ygrp-lc .yiv0345349574ad {margin-bottom:10px;padding:0 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2465B Recap Project

John Dickens <jake_117_dickens@...>
 

Does anyone have a list of capacitors they have purchased to recap the A1, A1A2, A3 and A5 boards or an early 2465B (Serial number around B015000)? I would like to use the most appropriate caps.

Thanks, John


Re: 7854 RAM card upgrade only - any interest?

 

The design is straightforward but my measurements are a puzzle.

K0 through K7 can only be driven from two sources. The MPU drives
them during keyboard scanning with U310 shown on schematic 27. When
KBID is high, the outputs of U310 are disabled and K0 through K7 are
pulled high with 4.7k pullup resistors. KBID also drives the open
collector drivers in the keyboard ID circuit shown on schematic 19 and
the memory backup state circuit shown on schematic 36 and those pull
K0 and K7 down.

The problem I saw is that somehow the memory backup state circuit can
be pulling K7 down while simultaneously K7 gets actively pulled up and
the only thing which can do that is U310 but U310 is disabled by KBID
which also enables the circuit which pulls K7 down. That makes no
sense unless there is some other circuit or there is a fault or my
measurement was bad.

I am going through the specifications of the various parts to see if
there is a way to explain my measurements. Then I am going to add a
reset switch to the MPU card so that I do not have to power the
oscilloscope off and on to make the measurement and I am going to try
a different DSO; chop mode on a 2230 DSO operates in an unusual way
and maybe it produced a misleading result.

I do have a theory which may represent a design mistake on the part of
Tektronix. U210 drives the enable for U310 directly and KBID through
a 510 ohm resistor as shown on schematic 27. The built in keyboard
however decouples KBID to ground with 0.1 microfarad capacitor A3C430
as shown on schematic 18. That capacitor and the 510 ohm resistor
produce a time constant of 51 microseconds so at the end of the KBID
measurement period, U310 turns on and drives K7 immediately but the
KBID circuits are delayed in turning off. My measurements did not
quite show this but I was not looking specifically for it.

The parts list shows that A3C430 was not present initially but added
very early on and never removed or adjusted.

KBID also serves another purpose. It not only identifies which
external keyboard is connected but whether any external keyboard is
connected.

On 12 Mar 2016 19:03:02 -0800, you wrote:

Curiouser and curiouser. K0 - K7 are used bidirectionally on diagram 18, outputting from the keyboard scanner counter and inputting to the MPU data bus. K7 gates the switch matrix drive in both keyboards, addressed by K4-K6. and K3 selects the first or second half of the switch matrix output addressed by K0-K2 to -KDOWN. The internal keyboard does not have a second half in its matrix. K0 is driven back from KBID in the external keyboard through the keyboard select jumper we have been looking at. KBID is not used in the front panel keyboard, nor does it have a select jumper like the external one.
The front panel keyboard does decouple KBID to ground with a 0.1
microfarad capacitor which may be causing what I am observing.

Anyway, the K bus is capable of bidirectional operation. That's where the signal you are seeing comes from.
The MPU side can drive the K bus high or low but except for the 4.7k
pullup resistors, nothing else can drive the K bus high which is what
I observed.

The -KDOWN lines from both keyboards are dotted together. I just went through the two keyboard matrices. The MPU cannot tell if a keypress came from the front panel keyboard or the equivalent key on the external one. The occupy identical spots in the address matrix.

My head is spinning a bit going back and forth between diagrams 18, 19, 27 and 36.

Cliff
I printed out schematic 36 which also allows me to mark it up.


Re: Tektronic 466 - Storage Modes inop

Jim McIntyre
 

Yes - It'd be nice to know what triggered this. Replacing these 4 parts has restored basic storage functionality. My best guess is there was a previous failed service attempt. There were some signs of this on the A10 Assy. Many of the adjustment pots are at one extreme, there is some flux residue around some of the jumper wires, and several of the TTL logic chips aren't original to the instrument.

There are still some issues, but variable presistence is now sort-of working, and the erase works. So I'm hoping it just needs adjustment now.


One valuable lesson I have learned is these TO-92 transistors do not have their base lead always bent the same way, so it's easy to get the E and C swapped if you're not paying attention...


Re: OT 10Mhz references

 

Hi Dwayne,

Tom Van Baak, one of the most famous of the group known as the "Time-Nuts"
has three Hydrogen Masers. He is in a league of his own. His website is at
http://www.leapsecond.com/

Somewhere on his web site is the story of when he took his kids camping for
a weekend to Paradise which is 7,000 feet up on Mt. Rainier near us in
Seattle. Of course Tom does things a little differently than the rest of us.
He brought 3 HP Cesium Standards up with him on the trip. When he got back
down he compared the time dilation that occurred between the three Cesium
Standards up on the mountain for the weekend with the ones he kept in his
house which is almost at sea level. He then calculated the expected time
difference based on General Relativity.

Tom is a little smarter than most of us. The Time-Nuts are a lot smarter
than I am.

But I know why Craig Sawyers and I have a Trimble Thunderbolt. Even if we
can't keep up with the Time-Nuts it doesn't mean we can't have a time
standard good to 12 digits. Sometimes it's just fun to watch something that
accurate.

Dennis Tillman W7PF.

-----Original Message-----
Sent: Friday, March 11, 2016 10:23 AM
Subject: Re: [TekScopes] Re: OT 10Mhz references

I am curious what you guys are doing that requires that sort of long-term
precision?
------------------------------------
Posted by: Dwayne Verhey <tekscopes@...>
-----------------------------------------

Original Message-----
Sent: Friday, March 11, 2016 10:45 AM
Subject: RE: [TekScopes] Re: OT 10Mhz references

I am curious what you guys are doing that requires that sort of long-term
precision?

Because it is there, and affordable. There are those who are a whole lot
worse in that regard. The ultimate reference is a hydrogen maser - and
there are guys out there who have one (have a look at time nuts website) at
many tens of thousands. Or if you want the ultimate in phase noise, a BVA
SC-cut ovenised crystal is almost unbeaten for this
http://www.oscilloquartz.com/files/1363164953-Br_%20OCXO%208607.pdf .
Oscilloquartz were alas acquired and discontinued their world beating
expertise in this difficult corner of technology.

Rakon have taken this up though
file:///F:/Downloads/USO%20HSO14%20Shortform-A1.pdf , but a BVA crystal
oscillator will set you back 10k somethings (dollars, euros, UKP). But
although the phase noise and Allen deviation are astoundingly good, the
frequency will drift in common with all crystal oscillators.

I'm happy though with my humble Trimble - a couple of hundred once you have
the active bullet antenna with a good view of the sky.
------------------------------------
Posted by: "Craig Sawyers" <c.sawyers@...>
------------------------------------


Re: OT 10Mhz references

 

Hi Ancel,
I second Craig's comments about the Trimble Thunderbolt GPSDO. That is what
I use. I put mine in a TM500 single wide plugin. It's hard to beat the
average signal you come up with from 6+ cesium standards.
Dennis Tillman W7PF

-----Original Message-----
Sent: Thursday, March 10, 2016 11:32 PM
Subject: RE: [TekScopes] OT 10Mhz references

On 10/03/2016 7:39 PM, mosaicmerc@... [TekScopes] wrote:

Hi all:
I'm hoping to ref. a Rigol DSA815, a Rigol DG1022A sig gen and an HP
8753D VNA....to a good 10Mhz ref.
I see a heap of them here:
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-
/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322
http://stores.ebay.com/Flyingbests-Equipment/High-reliability-OCXO-
/_i.html?_fsub=908870013&_sid=282770553&_trksid=p4634.c0.m322


IDK what voltage is optimal or which unit to chose (*sine/square,
single or double OXCO) and need some advice on this.
tx
Other ways of skinning the cat is a 10MHz Rb oscillator. Main ones are
Efratom and FEI. Lots from USA and China from decommissioned comms racks.
Also lots of options - sine, square, ones that have a synthesiser so you can
set the frequency over quite wide limits (but that increases the spurs quite
a lot) - lots of info on the web.

Or (what I use) is a GPS standard - a Trimble Thunderbolt from eBay. That
locks to the Caesium standards in orbit, so is bang on frequency to 1 part
in 10 to the lots of zeroes, and about 20fs noise. You need a bullet
antenna too - I've got mine on a short pole attached to the end gable of the
house. Supported by Tboltmon (s/ware from Trimble, or Lady Heather (again
lots on web).

But both those options are relatively expensive as compared with an ovenised
clock module.

With that in mind, the Trimble 10MHz OCXO is the core of the Thunderbolt -
and that is on your list.
That has ultralow phase noise, measured here http://www.ke5fx.com/tbolt.htm

But it depends on how accurate you want your 10MHz, and what phase
noise/Allen deviation you want.
And how deep your pocket. And how anal you are (I'm pretty anal).
------------------------------------
Posted by: "Craig Sawyers" <c.sawyers@...>
------------------------------------


Re: 7854 RAM card upgrade only - any interest?

Cliff Carrie
 

Curiouser and curiouser. K0 - K7 are used bidirectionally on diagram 18, outputting from the keyboard scanner counter and inputting to the MPU data bus. K7 gates the switch matrix drive in both keyboards, addressed by K4-K6. and K3 selects the first or second half of the switch matrix output addressed by K0-K2 to -KDOWN. The internal keyboard does not have a second half in its matrix. K0 is driven back from KBID in the external keyboard through the keyboard select jumper we have been looking at. KBID is not used in the front panel keyboard, nor does it have a select jumper like the external one.

Anyway, the K bus is capable of bidirectional operation. That's where the signal you are seeing comes from.

The -KDOWN lines from both keyboards are dotted together. I just went through the two keyboard matrices. The MPU cannot tell if a keypress came from the front panel keyboard or the equivalent key on the external one. The occupy identical spots in the address matrix.


My head is spinning a bit going back and forth between diagrams 18, 19, 27 and 36.


Cliff


Re: 7854 RAM card upgrade only - any interest?

 

On 11 Mar 2016 20:45:12 -0800, you wrote:

The dongle makes economic sense if there is no keyboard (and no plans to add one). One D connector and a standard backshell - not costly at all, and no internal mods (except for plugging in the new memory card).

Good test from the keyboard connector. Was that on a B100000 scope or an earlier one? Should I repeat it on mine (B063xxx; old RAM & separate ROM cards)?
The test was on my B100000+ 7854 which has the first version of the
combined memory board and that is how I was able to provide a scan and
photo of the board.

I ran some tests. KBID goes high for 50 microseconds and the
transistor inverter with a 47k base resistor has no trouble driving
K7. I noticed something odd however.

K7 sometimes gets driven high by some other source during the last
half of the 50 microsecond pulse from KBID. This should not be
possible because KBID also disables octal buffer U310 (schematic 27)
which is the only source that can drive K7. The stock configuration
with U15F driving K7 produces the same results and it even oscillates
when the conflict occurs.

I am going to make some more measurements and try to track down what
is happening. I might consider it normal except that the schematics
do not show how this is possible.


Re: 465 foot 3d model

Malcolm Hunter
 

On 12 March 2016 at 20:39, John Clark johnclark05@... [TekScopes] <
TekScopes@...> wrote:

I do have a few 314/335 feet now but I'm clueless when it comes to the 3D
modeling software. I'm good at a lot of things but 3D drawing has never
been one of them. I installed Sketchup a while back for another project I
wanted someone to print for me but finally gave up after it kicked my
behind. Makes me feel like an idiot, too, since everything I read about it
says it's so easy to use.

​If you could take photos from all angles and provide exact dimensions​, I
could have a go at it.

Malcolm


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