Re: Parallel resistance spreadsheet
As I have learned so many times the hard way, there are several apps on the web that do this automatically. ? One I found to be particularly helpful is this one that will calculate to any precision you desire down to 1% with any values you might find in your junk drawer and it tells you the deviation from your desired percentage and which of the values will give the closest match. ?
? Dennis ?
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From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Reed Dickinson Sent: Monday, March 11, 2013 12:58 PM To: TekScopes@... Subject: [TekScopes] Parallel resistance spreadsheet?
Nothing works, back to the drawing bored!
On 3/11/2013 12:54 PM, Reed Dickinson wrote: ? Well gang, maybe the third time will bear fruit.? I shortened the file name.? If this does not work then save the files PAR.* in a folder and open with your spreadsheet program.? I did not test it in Access but it works in Lotus.
Reed
On 3/11/2013 12:48 PM, Reed Dickinson wrote: ? I just tried to read the file PARALLEL.WK1 that came back form Tekscopes and it was corrupted.? I will re-attach another copy.? Lets see how this one works.
On 3/11/2013 12:28 PM, Reed Dickinson wrote: ? There was a thread a few weeks ago about a parallel resistance calculator. I created a spreadsheet that allows you to instantly select a pair of 5% resistors to yield just about any resistance value desired. I used the @VLOOKUP function in Lotus 123 and every value of 5% resistor from 10 Ohms up to 36MOhms is included. I will attach a copy to this note. Please reply if any improvements can be incorporated.
Reed Dickinson reed714@...
?
?
|
Parallel resistance spreadsheet
Well gang, sending in Lotus 123 apparently did not work so I will
try sending as an OpenOffice file.
Reed
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Show quoted text
There was a thread a few weeks ago about a parallel
resistance
calculator. I created a spreadsheet that allows you to instantly
select
a pair of 5% resistors to yield just about any resistance value
desired. I used the @VLOOKUP function in Lotus 123 and every value
of
5% resistor from 10 Ohms up to 36MOhms is included. I will attach
a
copy to this note. Please reply if any improvements can be
incorporated.
Reed Dickinson
reed714@...
|
Re: Parallel resistance spreadsheet
Thanks David.? I will re-send it using Open Office files.
On 3/11/2013 1:07 PM, David Holland
wrote:
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?
Worked for me.....
Very useful, IMO. ? ?Loads ok with OpenOffice,
Thanks!
David
On Mon, Mar 11, 2013 at 3:58 PM,
Reed Dickinson <reed714@...>
wrote:
Nothing works, back to the drawing bored!
On 3/11/2013 12:54 PM, Reed Dickinson wrote:
?
Well gang, maybe the third time will bear
fruit.? I shortened the file name.? If this
does not work then save the files PAR.* in a
folder and open with your spreadsheet
program.? I did not test it in Access but it
works in Lotus.
Reed
On 3/11/2013 12:48 PM, Reed Dickinson
wrote:
?
I just tried to read the file
PARALLEL.WK1 that came back form Tekscopes
and it was corrupted.? I will re-attach
another copy.? Lets see how this one
works.
On 3/11/2013 12:28 PM, Reed Dickinson
wrote:
?
There was a thread a few weeks ago
about a parallel resistance
calculator. I created a spreadsheet
that allows you to instantly select
a pair of 5% resistors to yield just
about any resistance value
desired. I used the @VLOOKUP function
in Lotus 123 and every value of
5% resistor from 10 Ohms up to 36MOhms
is included. I will attach a
copy to this note. Please reply if any
improvements can be incorporated.
Reed Dickinson
reed714@...
|
Re: Parallel resistance spreadsheet
Worked for me.....
Very useful, IMO. ? ?Loads ok with OpenOffice,
Thanks!
David
toggle quoted message
Show quoted text
On Mon, Mar 11, 2013 at 3:58 PM, Reed Dickinson <reed714@...> wrote:
Nothing works, back to the drawing bored!
On 3/11/2013 12:54 PM, Reed Dickinson
wrote:
?
Well gang, maybe the third time will bear fruit.? I
shortened the file name.? If this does not work then save
the files PAR.* in a folder and open with your spreadsheet
program.? I did not test it in Access but it works in
Lotus.
Reed
On 3/11/2013 12:48 PM, Reed
Dickinson wrote:
?
I just tried to read the file PARALLEL.WK1 that came
back form Tekscopes and it was corrupted.? I will
re-attach another copy.? Lets see how this one works.
On 3/11/2013 12:28 PM, Reed
Dickinson wrote:
?
There was a thread a few weeks ago about a
parallel resistance
calculator. I created a spreadsheet that allows
you to instantly select
a pair of 5% resistors to yield just about any
resistance value
desired. I used the @VLOOKUP function in Lotus 123
and every value of
5% resistor from 10 Ohms up to 36MOhms is
included. I will attach a
copy to this note. Please reply if any
improvements can be incorporated.
Reed Dickinson
reed714@...
|
Parallel resistance spreadsheet [2 Attachments]
Nothing works, back to the drawing bored!
On 3/11/2013 12:54 PM, Reed Dickinson
wrote:
toggle quoted message
Show quoted text
?
Well gang, maybe the third time will bear fruit.? I
shortened the file name.? If this does not work then save
the files PAR.* in a folder and open with your spreadsheet
program.? I did not test it in Access but it works in
Lotus.
Reed
On 3/11/2013 12:48 PM, Reed
Dickinson wrote:
?
I just tried to read the file PARALLEL.WK1 that came
back form Tekscopes and it was corrupted.? I will
re-attach another copy.? Lets see how this one works.
On 3/11/2013 12:28 PM, Reed
Dickinson wrote:
?
There was a thread a few weeks ago about a
parallel resistance
calculator. I created a spreadsheet that allows
you to instantly select
a pair of 5% resistors to yield just about any
resistance value
desired. I used the @VLOOKUP function in Lotus 123
and every value of
5% resistor from 10 Ohms up to 36MOhms is
included. I will attach a
copy to this note. Please reply if any
improvements can be incorporated.
Reed Dickinson
reed714@...
|
Parallel resistance spreadsheet [2 Attachments]
Well gang, maybe the third time will bear fruit.? I shortened the
file name.? If this does not work then save the files PAR.* in a
folder and open with your spreadsheet program.? I did not test it in
Access but it works in Lotus.
Reed
On 3/11/2013 12:48 PM, Reed Dickinson
wrote:
toggle quoted message
Show quoted text
?
I just tried to read the file PARALLEL.WK1 that came
back form Tekscopes and it was corrupted.? I will
re-attach another copy.? Lets see how this one works.
On 3/11/2013 12:28 PM, Reed
Dickinson wrote:
?
There was a thread a few weeks ago about a parallel
resistance
calculator. I created a spreadsheet that allows you to
instantly select
a pair of 5% resistors to yield just about any
resistance value
desired. I used the @VLOOKUP function in Lotus 123 and
every value of
5% resistor from 10 Ohms up to 36MOhms is included. I
will attach a
copy to this note. Please reply if any improvements
can be incorporated.
Reed Dickinson
reed714@...
|
Parallel resistance spreadsheet [1 Attachment]
I just tried to read the file PARALLEL.WK1 that came back form
Tekscopes and it was corrupted.? I will re-attach another copy.?
Lets see how this one works.
On 3/11/2013 12:28 PM, Reed Dickinson
wrote:
toggle quoted message
Show quoted text
?
There was a thread a few weeks ago about a parallel
resistance
calculator. I created a spreadsheet that allows you to
instantly select
a pair of 5% resistors to yield just about any resistance
value
desired. I used the @VLOOKUP function in Lotus 123 and
every value of
5% resistor from 10 Ohms up to 36MOhms is included. I will
attach a
copy to this note. Please reply if any improvements can be
incorporated.
Reed Dickinson
reed714@...
|
Parallel resistance spreadsheet
There was a thread a few weeks ago about a parallel resistance calculator. I created a spreadsheet that allows you to instantly select a pair of 5% resistors to yield just about any resistance value desired. I used the @VLOOKUP function in Lotus 123 and every value of 5% resistor from 10 Ohms up to 36MOhms is included. I will attach a copy to this note. Please reply if any improvements can be incorporated.
Reed Dickinson reed714@...
|
Re: New here with a 2465 to clean up
See my U800 heat sink:
Dave
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On Mar 10, 2013, at 11:05 AM, machineguy59 wrote: Second, I built a heat sink for U800 by modifying an old heat sonk from a computer video board. ?It was messsy to cut notches for adjacent parts but it was worth it. ?I have a heat sink that fits well and seems to work well. ?It screws to the same screws that hold the U800 but I was careful to no overtighten. ?I can post or mail pictures if anyone is interested.
Mac
|
Re: 7L13 'Center Frequency' display issue
Oops, wrong post reference, my last post, 89603 was in ref. to post 88852, not 7360. (Goodness knows where THAT came from.) ~Michael
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--- In TekScopes@..., "Michael" <af7u@...> wrote:
Hello everyone, This post is a follow up from post #7360, and my 7L13 with center frequency LED readout all zeros. I am a bit further along with my investigation. I now understand the operation 'somewhat' more. I have looked over the diagrams and taken some voltage readings, I also understand the basic DVM logic and readout operation which sends data to the LCD and the CRT. I have an article from a Jan, 1975 '73' magazine which talks about the Fairchild 3814 digital voltmeter. I must admit I am not too clear on the 'Analog' section of the meter. On board 'A2100', diagram 12, the input to pin 2 of U2110 comes from plug P2540 pin 4. Looking over the A2500 board shows that pin 4 goes to chassis ground. Why would pin 2 from U2110 go all the way back to A2500 to reach chassis ground.
Anyway, the A2000 board seems to be working, albeit the frequency of the clock oscillator is not 200kHz as the diagram shows, it is running at 153.7kHz, though amplitude is good at 5 volts, I would think that would affect calibration but not operation. Back on A2100, the tuning control voltage at R2104 is good, it swings from + - 9.6 volts. The output of U2110 swings + - 10.7 volts. The DCPL Supply rails 15, -15, and 5 volts are all good. The reference voltage at the cathode of VR2115 (Zener) is 3.1, not the 3.3 volts is shows. Voltage at TP 2100, (output of U2130) is 11.65, a bit higher than the listed 11.3 volts. The voltages around the N-channel FET (Q2120) is Drain = 3.37 volts, Source = -3.1 volts, and Gate = -3.5 volts, are those in the ball park?
Needless to say there is NO signals present, waveform, 1, 2, 3, and 4 are all missing. Lines 'E' and 'F' are both quiet, the voltages on 'E' are 7.08 volts, on 'F' the voltage is 5.12 volts which swings a bit higher when I adjust center frequency, up to 5.44 volts. Of course 'E' has no signal as would be expected without drive from U2145 there is nothing to trigger the multivibrator U2030 on board A2000 sending a signal back up line 'F'. I keep thinking of this in terms of a frequency counter, I keep thinking there should be a driving input signal. I try to keep in mind it's a voltmeter, and keep in mind the circuit description given in the manual. It describes a ramp signal coming from the output of U2110, I don't understand that statement. The 'Tune' voltage is just a DC voltage, plus to minus. The minus input of U2120 goes to chassis ground??? What 'RAMP' are they speaking about?
Lastly the manual's circuit description on page 5-10 talks about a positive going ramp from U2110, aren't these just DC levels, what 'Ramp' are they talking about?
Okay, I see there are a lot of questions here. I had better post this and hope for the best. It's a great 7L13, it works well, but without a 'Center' frequency display, it's pretty much just a toy. Also, I do appreciate the feedback~!~ I am not accustom to working on test equipment, my experience has been mostly all in Hi-Fi, but this has been very interesting.
Thanks again VERY MUCH... ~Michael - AF7U
--- In TekScopes@..., "Michael" <af7u@> wrote:
I sure appreciate the input, I will give everything a go once I get it on my bench. Should be this weekend or first of next week. Thanks again, ~Michael
--- In TekScopes@..., "Christopher Hilton-Johnson" <chj@> wrote:
Also make sure that the 2 boards, A2100 DVM analog board and A2000, DVM logic & readout board are only connected/touching where they should. There needs to be a small space (say 1mm or less) between each - a piece of thin card between the two will suffice. If the boards touch the display can freeze, you can lose the units digit on the SA (although the 7Kxx readout still works). OP is spot on - also remove clean & reseat the A2000 board actives.
Beyond that you need to start looking at the A2100 board & follow the volts! The manual gives an excellent description of what should happen. On the basis that neither readout works, it is more likely the A2100, analog board you need to look at.
Chris HJ
My 7L13 display was cured by pulling and reseating the DIPs on the RO board. IC pins were visibly tarnished. Symptoms not as complete as yours, but AFAIR the display would intermittently 'freeze' while tuning continued.
--- In TekScopes@... <mailto:TekScopes%40yahoogroups.com> , "Michael" wrote:
Hi all, I have a 7L13 Spectrum Analyzer out in the field, it's not in front of me right now but I will pick it up later this week. I've seen the unit and the 'Center Frequency' LED read-out is stuck, and reads '0000', also the same value is being sent to the CRT display. The analyzer is sitting in a 7000 series mainframe and the mainframe works fine in every other way. In fact, the spectrum analyzer works fine, just the 'Center Frequency' display stays on zeros. The 'Tuning' works and adjusts correctly. It is used with a TR-502 and that combination also works, you just don't know where you are frequency wise. You can place a frequency counter on the AUX out of the TR-502 and manually scan the bandwidth and read the frequency on the counter. It appears everything is fine, just the readout is non-functional, or at least stuck on zeros. I thought it was curious the display in the 7000 is also reading zeros too. I will have it in front of me next week but I thought I would see if anyone had any thoughts before I open it up.
Thanks in advance, ~Michael - AF7U
o virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2238 / Virus Database: 2639/5618 - Release Date: 02/20/13
|
Re: New here with a 2465 to clean up
Can you please give the link?
Thanks, Dave
The spead sheet posted at Tekarc was very helpful and still relevant. ...Mac
|
Re: New here with a 2465 to clean up
Please post photos & drawings of your heat sink to the Photos area & Files area on the group's page on the Yahoo Groups web site.
Thanks, Dave
Second, I built a heat sink for U800 by modifying an old heat sonk from a computer video board. It was messsy to cut notches for adjacent parts but it was worth it. I have a heat sink that fits well and seems to work well. It screws to the same screws that hold the U800 but I was careful to no overtighten. I can post or mail pictures if anyone is interested.
|
Re: calibration help for my TDS544A
Yes, it is possible with an HP8640B,
but probably not with 8656B because of lower maximum amplitude. ?
I have done it with a 8640 before I got my SG503/504 (and made the
SG-504 leveling head from the kit described in many messages in
this forum).? The HP signal generator is not "leveled" with the
output cable included, so the signal delivered at the end of the
cable is less than the signal level at the meter by the amount of
cable loss.? At low frequency (6MHz "reference") the loss is
insignificant, but increases to about 1dB at hundreds of MHz.? So
you have to adjust amplitude each time you change a higher
frequency in the procedure.? I had a Booton RF millivoltmeter that
allowed me to get through the procedure, but this makes it even
more tedious.? You can save money by buying an SG-504 without the
head and then building the kit (if you can deal with tiny parts
like 0402).? Note that a "good" SG-504 will show no output signal
unless it is connected to a head.
Dan
On 3/7/2013 10:00 AM, bddicch wrote:
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?
hi night walker is it not possible to do with HP 8656B
signal generator...and not with the sg503 +sg504 that is
much to expensive indead.. the comp. part i knew..
|
How to clean old scopes is explained in the archives in great detail
To Cliff and others, ? Cleaning out old scopes is a topic that has been answered in great detail several times over. I scanned and published the original TekScopes article on how Tek does it. It is in the archives. Please take the time to search our archives before resurrecting this topic yet again. ? Dennis ? From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Cliff White Sent: Sunday, March 10, 2013 1:43 PM
I've heard that Tek would wash out all the scopes they got back for repair to remove dust/smoke, etc from the inside of the unit. Is this still doable with 60+ year old components? I'm kinda hesitant to have at it with the water hose, but I don't really see how it would hurt either... Ideas?
|
Re: New here with a 2465 to clean up
Hi,
Great report.
Jerry Massengale
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-----Original Message-----
From: machineguy59
To: TekScopes
Sent: Sun, Mar 10, 2013 1:05 pm
Subject: [TekScopes] Re: New here with a 2465 to clean up
?
You guys are super. Thanks you again for the warm welcome and helpful advice. I finally got some time to apply some of it and want to give you a status update.
First, I dismantled the front control panel and cleaned everything. There was a minor amount of residue from an old spill (I feared it would be worse) but overall the inside is remarkably clean. I did find that someone had previously glued some knob covers to their inserts and they broke during tear down. I plan to order replacements but I CAN glue them back if necessary.
Second, I built a heat sink for U800 by modifying an old heat sonk from a computer video board. It was messsy to cut notches for adjacent parts but it was worth it. I have a heat sink that fits well and seems to work well. It screws to the same screws that hold the U800 but I was careful to no overtighten. I can post or mail pictures if anyone is interested.
Third, Patrick, your advice to measure voltages on J119 (the test point for regulated low voltage on the mainboard) is spot on. The -8 volt supply is only at -6.4 volts (a 20% error). Also, several voltages have ripple that is far out of spec (I didnt record actual values but will before repairs are started). My review of the schematics shows that -8 supply only feeds the two vertical pre-amps (U100 and U200) and the op amp that sets paramters for VAR gain and DC ballance (U160). My conclusion is that you were right, the -8 volt supply is failing (probably the output filter cap) and this drooping voltage causes the vertical pre-amp gains to be off and variable. Alternatively, one of the preamps or the op amp is overloading the supply but this seems unlikely since other preamp functions are working.
Fourth, I ordered new caps for the entire LVPS (both boards). The spead sheet posted at Tekarc was very helpful and still relevant. All parts are still available at Mouser. I verified this list with the service manual for the 2465 and found I need two additional caps (C1112, and C1050). I also chose to order replacements for the ceramic caps but will probably not change them out since ceramics seem to have a long life expectancy. I apprecaiate any advice on this decision.
Fifth, I found that the case fan is not running. The shaft turns freely and feels to run smoothly but the fan does not turn. If I give it a spin by hand it just stops with no apparent self motivation. So I have a fan to repair. Its one of the "original" designs with a separate transistorized drive board. These were very quiet fans so I will try to restore this one.
So work continues in my spare time. I expect a complete restoration will be possible. I will post updates of my progress along the way. But I wanted to post this thank you for the excellent help I have received from this group. I would not take on this project without your advice.
Mac
--- In TekScopes@..., "Patrick Wong" wrote:
>
> Hi Mac,
>
> I recommend that you add qservice.tv as a favorite in your browser because you can get lots of useful information about Tektronix scopes there.
>
> For example, you will see that the part number for the 2465 low voltage power supply has a slightly different suffix compared to the LVPS for the 2465A and 2465B. Therefore I would not assume that a parts list compiled for a 2465B will work 100% for your unit. It might be 95% correct, or might be further off.
>
> When I worked on the LVPS for my 2465A and 2467 I found small differences between the capacitors. There were a few non-polarized electrolytics in the 2465A power supply. Both scopes were built in mid-1988. Therefore, even within the 2465A/2467 generation, you cannot count on the LV power supplies being identical with regards to capacitor content.
>
> I also recommend you replace the two AC X2 line filtering capacitors as you will probably see the yellow transparent plastic body has lots of cracking. This is a potential failure area especially in Europe where the AC line voltage is 220V or more.
>
> With regards to the CH1 and CH2 gain problem, I doubt the preamp hybrids are the problem. Assuming the 2465 has similar circuitry as 2465A in this area, I suggest you look at U160, a quad op-amp which controls the gain and DC balance for U100 and U200 (see schematic #4 which shows the vertical attenuators and preamp section.) U160 is powered by the +15V and -8V power supplies (see the power distribution diagram) so a problem with either of those two may help explain the gain problem you noticed.
>
> Meanwhile the CH3/CH4 hybrid is powered by the +5V and -5V supplies.
>
> Does your A5 board have a lithium battery soldered to one end? If so, that maintains calibration constants.
>
> Assuming the battery is original, I suggest you add a replacement battery to your parts ordering form. You will need to maintain voltage with a lab power supply while unsoldering and replacing the battery (using a non-grounded soldering iron.)
>
> Good luck,
>
> Patrick Wong AK6C
>
> --- In TekScopes@..., "machineguy59" wrote:
> >
> > ...That parts list is for a 2365B but it looks to me that it will also work for a 2465. Does anyone know if there are differences?
> >
> > Then, with the heat sink on U800 and the knowledge the glue is cleaned out, I will resume the quest to find why the gain is messed up on Ch 1 and Ch 2. This gain on Ch ! and Ch 2 is my only serious concer for the scope.
>
|
Re: New here with a 2465 to clean up
Most likely C1101 and C1102 on the low voltage power supply are bad
resulting in the unregulated -8 volts being out of spec. These two capacitors
are on the A3 board.
?
?
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Show quoted text
----- Original Message -----
Sent: Monday, March 11, 2013 1:24
AM
Subject: [TekScopes] Re: New here with a
2465 to clean up
?
Yes, I followed the service manual directions, loosened the nut on the
collet, held my breath and pulled twice at 90 degrees rotations. The second
pull let go and the fan came off clean. Guess I was living right today. I cna
take pics if it will help anyone. I would try to make impression molds if
someone wants to model this for a 3D printer.
I also got a chance to
measure voltages and rough measures of ripple on J119, the test point for the
main board. All values are almost in spec except for pin 11 the -8 volt supply
to the channel 1 and 2 inputs. There I found the voltage at -6.4 volts (as I
reported before) with a triangle waveform riding on top of over 150
millivolts. I am convinced this is the same waveform that corrupts the Ch1 and
Ch2 traces. Now I have to separate cause from effect (is the power corrupt
because its overloaded or is the regulator faulty). I also measured the
voltage supply at U160 and found this tringle wave on the DC power. Overall,
good progress for today.
I think my next step will be to tear down the
LVPS to repair the fan and inspect the -8 volt regulator while its apart. My
goal is to correct the power supply before replacing all the electrolytic and
film caps.
--- In TekScopes@..., "Tom
Miller" wrote: > > There are no brushes
in that motor. > > There is an end play adjustment on the rear
bearing but it requires removal of the pc board to get to. > Did the fan
just pull off the shaft? > > T > > ----- Original
Message ----- > From: machineguy59 > To: TekScopes@...
> Sent: Sunday, March 10, 2013 6:14 PM > Subject: [TekScopes] Re:
New here with a 2465 to clean up > > > > I will
post my experience repairing the fan when I have it completed. But for now,
the fan and squirrel cage appear to be intact. The collet is functional
although I have not taken the jaws out of the sleeve yet. I was careful
removing them and it all looks good to me. > > I suspect either
the motor windings (not likley I think), the motor "brushes" (more likely), or
the drive transistors (what I am hoping for). I will keep my fingers crossed.
> > --- In TekScopes@..., "Tom
Miller" wrote: > > > > We will be
interested in how you resolve the fan problem. > > > > it
is a well known issue. Most likely the plastic fan collet has broken. >
> Hey, I wonder if this part (or something similar) could be made with the
3D printer? > > > > > > Tom > > >
> ----- Original Message ----- > > From: machineguy59 >
> To: TekScopes@...
> > Sent: Sunday, March 10, 2013 2:05 PM > > Subject:
[TekScopes] Re: New here with a 2465 to clean up > > > >
> > > > You guys are super. Thanks you again for the warm
welcome and helpful advice. I finally got some time to apply some of it and
want to give you a status update. > > > > First, I
dismantled the front control panel and cleaned everything. There was a minor
amount of residue from an old spill (I feared it would be worse) but overall
the inside is remarkably clean. I did find that someone had previously glued
some knob covers to their inserts and they broke during tear down. I plan to
order replacements but I CAN glue them back if necessary. > >
> > Second, I built a heat sink for U800 by modifying an old heat
sonk from a computer video board. It was messsy to cut notches for adjacent
parts but it was worth it. I have a heat sink that fits well and seems to work
well. It screws to the same screws that hold the U800 but I was careful to no
overtighten. I can post or mail pictures if anyone is interested. > >
> > Third, Patrick, your advice to measure voltages on J119 (the
test point for regulated low voltage on the mainboard) is spot on. The -8 volt
supply is only at -6.4 volts (a 20% error). Also, several voltages have ripple
that is far out of spec (I didnt record actual values but will before repairs
are started). My review of the schematics shows that -8 supply only feeds the
two vertical pre-amps (U100 and U200) and the op amp that sets paramters for
VAR gain and DC ballance (U160). My conclusion is that you were right, the -8
volt supply is failing (probably the output filter cap) and this drooping
voltage causes the vertical pre-amp gains to be off and variable.
Alternatively, one of the preamps or the op amp is overloading the supply but
this seems unlikely since other preamp functions are working. > >
> > Fourth, I ordered new caps for the entire LVPS (both boards).
The spead sheet posted at Tekarc was very helpful and still relevant. All
parts are still available at Mouser. I verified this list with the service
manual for the 2465 and found I need two additional caps (C1112, and C1050). I
also chose to order replacements for the ceramic caps but will probably not
change them out since ceramics seem to have a long life expectancy. I
apprecaiate any advice on this decision. > > > > Fifth, I
found that the case fan is not running. The shaft turns freely and feels to
run smoothly but the fan does not turn. If I give it a spin by hand it just
stops with no apparent self motivation. So I have a fan to repair. Its one of
the "original" designs with a separate transistorized drive board. These were
very quiet fans so I will try to restore this one. > > > >
So work continues in my spare time. I expect a complete restoration will be
possible. I will post updates of my progress along the way. But I wanted to
post this thank you for the excellent help I have received from this group. I
would not take on this project without your advice. > > > >
Mac > > > > > > --- In TekScopes@...,
"Patrick Wong" wrote: > > > > > > Hi
Mac, > > > > > > I recommend that you add qservice.tv
as a favorite in your browser because you can get lots of useful information
about Tektronix scopes there. > > > > > > For
example, you will see that the part number for the 2465 low voltage power
supply has a slightly different suffix compared to the LVPS for the 2465A and
2465B. Therefore I would not assume that a parts list compiled for a 2465B
will work 100% for your unit. It might be 95% correct, or might be further
off. > > > > > > When I worked on the LVPS for my
2465A and 2467 I found small differences between the capacitors. There were a
few non-polarized electrolytics in the 2465A power supply. Both scopes were
built in mid-1988. Therefore, even within the 2465A/2467 generation, you
cannot count on the LV power supplies being identical with regards to
capacitor content. > > > > > > I also recommend you
replace the two AC X2 line filtering capacitors as you will probably see the
yellow transparent plastic body has lots of cracking. This is a potential
failure area especially in Europe where the AC line voltage is 220V or
more. > > > > > > With regards to the CH1 and CH2
gain problem, I doubt the preamp hybrids are the problem. Assuming the 2465
has similar circuitry as 2465A in this area, I suggest you look at U160, a
quad op-amp which controls the gain and DC balance for U100 and U200 (see
schematic #4 which shows the vertical attenuators and preamp section.) U160 is
powered by the +15V and -8V power supplies (see the power distribution
diagram) so a problem with either of those two may help explain the gain
problem you noticed. > > > > > > Meanwhile the
CH3/CH4 hybrid is powered by the +5V and -5V supplies. > > >
> > > Does your A5 board have a lithium battery soldered to one
end? If so, that maintains calibration constants. > > > >
> > Assuming the battery is original, I suggest you add a replacement
battery to your parts ordering form. You will need to maintain voltage with a
lab power supply while unsoldering and replacing the battery (using a
non-grounded soldering iron.) > > > > > > Good
luck, > > > > > > Patrick Wong AK6C > > >
> > > --- In TekScopes@...,
"machineguy59" wrote: > > > > >
> > > ...That parts list is for a 2365B but it looks to me that it
will also work for a 2465. Does anyone know if there are differences? >
> > > > > > > Then, with the heat sink on U800 and
the knowledge the glue is cleaned out, I will resume the quest to find why the
gain is messed up on Ch 1 and Ch 2. This gain on Ch ! and Ch 2 is my only
serious concer for the scope. > > > >
> >
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On 03/10/2013 05:19 PM, anson_williams@... wrote: Also looking at old messages about the 475 I found this.
"There's also a bluish 1% resistor (with the scope upside-down as you look on the main board with the front panel facing you, it's along the left edge maybe 2 or 3 inches from the front) that overheats, turns brownish and changes value, goofing up the timebases. If there's a black resistor in that spot, the mod has already been made. Otherwise, it needs replaced with a higher-power resistor."
I have that resistor it's bluish green is is browning in the middle. Should I replace it with one of the same value but higher wattage? Not sure what he is saying but taht would make the most sense. I don't know its current wattage as I don't know the number but it looks to be at least a watt. Anson, Just curious. Do you have the operator/service manual for the 475? The parts listing in the manual should have a description of all the components and their ratings. The Tek Semiconductors Common Design Parts Catalog (Cross-Reference) manual is also good to have handy when you need to find what transistor, IC, diode or other semiconductor really is, and if needed, ratings so you can determine a suitable substitute. Mark
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==================== Some places I worked on before used a product called Arklone, ?but I believe that was a cancer risk ? and withdrawn after some years Gear? came out like new afterwards, though ====================
Not cancer risk - ozone depletion. Well I guess high UV exposure as a result of ozone depletion is a cancer risk.
Arklone was CFC113, of which 160,000 tons was used in 1988 alone mainly for electronics cleaning (I was rather surprised by that statistic!)
Phased out totally by 2010
Craig
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Cliff Said
Sun Mar?10,?2013 1:43?pm (PDT)
. Posted by:
I've heard that Tek would wash out all the scopes they got back for
repair to remove dust/smoke, etc from the inside of the unit. Is
this
still doable with 60+ year old components? I'm kinda hesitant to
have at
it with the water hose, but I don't really see how it would hurt
either... Ideas?
---------------------------------------------
Make sure your water supply has preferably? a zero salt content
first!
Our local water here isn't salt free by a long way
Ive tried quality car wash products in the past and had reasonable
results
brushing it in then? rinsing from a bucket on an old? and very dirty
TEk scope
Its likely Tek used a dryer cabinet on the scope after washing
With tubed gear water can stay inside the tube sockets for
a long time
Whatever way you go make sure the scope is dried out very well
before switching it on.
Some places I worked on before used a product called Arklone,
?but I believe that was a cancer risk ? and withdrawn after some
years
Gear? came out like new afterwards, though
John B
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