Date   
Re: B92A no sweep

 

Hi Brent,
To get an intermittent to act up I reach for two things. I grab a can of
freeze spray, and a hair dryer. Use the hair dryer to warm up the entire
plugin. Do not use a Hot Air Gun - it gets too hot.

The freeze spray allows you to focus tighter on individual ICs or on small
areas of the PC board. More often than not the heat or the cold will trigger
an intermittent back to life.

Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, February 13, 2017 8:17 PM
Subject: [TekScopes] B92A no sweep

I forgot to mention that, initially last week the problem began with the
sweep working fine for the first 30 seconds and then quit. It might come
back for a few moments, even another 30 seconds on occasion before not
working at all: I assumed from a component warming up. This week however it
has not worked at all. I was able to use a thermal camera to look at heat on
the boards and found nothing unusual.Whatever it is, it isn't intermittent
any longer.
------------------------------------
Posted by: brentleew2003@...
------------------------------------

Re: B92A no sweep

 

On Tue, 14 Feb 2017 04:01:49 +0000 (UTC), you wrote:

Thanks David,I have re-seated everything I could find, I am using an extender I just built from John Griessen.
That is going to make things a lot easier.

Cam switches are all in good shape and properly functioning.
I didn't know if there were any known issues with the 7b92a.
There are no special issues that I know of.

From what I can read, they seem pretty reliable.
They are pretty complex though. The problems I have seen are shorted
tantalums and mechanical problems with the cam switches.

I know there is some mention of the sweep generator 155-049-02, but I am not sure how to diagnose it's proper function or if it's even suspect.

Thanks for the thoughtsBrent
On 14 Feb 2017 04:16:50 +0000, you wrote:

I forgot to mention that, initially last week the problem began with the sweep working fine for the first 30 seconds and then quit. It might come back for a few moments, even another 30 seconds on occasion before not working at all: I assumed from a component warming up. This week however it has not worked at all. I was able to use a thermal camera to look at heat on the boards and found nothing unusual.Whatever it is, it isn't intermittent any longer.
The problem before the unblanking was lost might simply have been the
sweep signal getting lost between the output of the sweep generator
and the horizontal amplifier. The alternatives are much more complex.

I had an idea which might apply to before the sweep vanished; if the
sweep was being displayed as a dot which gets wider as the sweep speed
is increased, then the unblanking is working and probably the sweep
integrator is working. The odd part is that the sweep reset was
apparently also working even though the sweep was never reaching that
point and to me that points to a problem with the end of sweep
comparator continuously indicating the end of the sweep.

The good news, if it can be considered that, is that the sweep
generators are all discrete. The bad news is that the loss of
unblanking (and loss of triggering?) indicates a larger problem.

Before getting too involved going through the circuits, I would make
measurements of the supply voltages on the boards. Maybe one of the
power supply decoupling networks gradually failed.

Re: OT Ripple Leader LTC-905

tronix_cal
 

Ripple, or phase error? - see section B on pg 3 in the users manual. I
had the same problem, and solved it by reversing the curve tracer plug
in the wall outlet.


On 02/13/2017 03:01 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on the
display curves as displayed on my 2465A scope. The electrolytics in
the box
have good ESR. Suggestions?

jerry





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

Re: X10 probe in series with X20 attenuator quest

Craig Sawyers <c.sawyers@...>
 

Re High-Voltage probes; be aware that the voltage rating is usually DC only and that there will be
a de-
rating curve for RF usage. Not sure you'll find one of those from a Chinese source.

Just as an example I'm just looking at a x100 probe from RS Components and their de-rating curve
shows a fall-off from 1200V Peak @ DC, flat to 1MHz then falling to 50% at 5MHz then to oblivion
at
100MHz. I guess for the 136KHz Amateur Band you'll be OK but for significantly higher frequencies
don't assume it will survive; you don't want that to breakdown with a KW of RF floating round!

Regards

Nigel G8AYM
That is absolutely true. As an example of the superb clarity with which Tek wrote manuals, this is
the P6009 100x probe manual, printed in 1964. Frequency derating curve, Xp/Rp as a function of
frequency, mechanical breakdown, schematics and parts lists. http://w140.com/tek_P6009.pdf

The cheapo Hantek 1x/10x probes don't have a downloadable manual
http://www.hantek.com/en/ProductDetail_15_73.html so no information on-line about derating etc.
However in fairness to them the CE mark you can see on the User's Guide conforms to the required
logo (which is very formally defined graphic https://ec.europa.eu/growth/single-market/ce-marking_en
), which is a positive point in their favour. And at least the P3100 100x probe manual has a
derating curve http://www.hantek.com/Manual/T3100_Probe_Manual.pdf . I'm grudgingly impressed for
Chinese probes.

Craig

Re: X10 probe in series with X20 attenuator quest

NigelP
 

Re High-Voltage probes; be aware that the voltage rating is usually DC only and that there will be a de-rating curve for RF usage. Not sure you'll find one of those from a Chinese source.

Just as an example I'm just looking at a x100 probe from RS Components and their de-rating curve shows a fall-off from 1200V Peak @ DC, flat to 1MHz then falling to 50% at 5MHz then to oblivion at 100MHz. I guess for the 136KHz Amateur Band you'll be OK but for significantly higher frequencies don't assume it will survive; you don't want that to breakdown with a KW of RF floating round!

Regards

Nigel G8AYM

Re: X10 probe in series with X20 attenuator question

NigelP
 

I can see there is already a thread going on here, but to simply answer your original confusion (and to add some more?); the bit that gives it away is the X sign...... so MULTIPLY each time you add an attenuator into the system (not add each time...... unless we're talking dB, but that's another bag of worms!).

Of course, it's not really multiply... it's actually DIVIDE (you are dividing the amplitude each time, not multiplying it!!!!????!!!!); we do like to confuse ourselves don't we :(. It's a multiplication of the attenuation each time, so the inverse of what it says!

Regards

Nigel

B92A no sweep

brentleew2003@...
 

I forgot to mention that, initially last week the problem began with the sweep working fine for the first 30 seconds and then quit. It might come back for a few moments, even another 30 seconds on occasion before not working at all: I assumed from a component warming up. This week however it has not worked at all. I was able to use a thermal camera to look at heat on the boards and found nothing unusual.Whatever it is, it isn't intermittent any longer.

Re: 7B92A No Sweep

Brent Watson <brentleew2003@...>
 

Thanks David,I have re-seated everything I could find, I am using an extender I just built from John Griessen.
Cam switches are all in good shape and properly functioning.
I didn't know if there were any known issues with the 7b92a.

From what I can read, they seem pretty reliable.

I know there is some mention of the sweep generator 155-049-02, but I am not sure how to diagnose it's proper function or if it's even suspect.

Thanks for the thoughtsBrent


From: "David @DWH [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Monday, February 13, 2017 6:09 PM
Subject: Re: [TekScopes] 7B92A No Sweep

  The dual timebases are difficult to work on so I would start by
reseating anything installed into a socket like the ICs and reseating
all of the connectors.

Are the cam switches turning to follow the time/div controls?

I would consider acquiring an extender so you can gain freer access to
the plug-in while it is operating.

On 12 Feb 2017 21:59:46 +0000, you wrote:

Greetings,
My 7B92A has lost it's sweep in all aspects. I have only a dot, centered, and positionable from center to the left side of the screen. The dot widens to the right with faster sweep speeds: 50ms and up. I do have a trigger lamp on with the Trigger Level 'centered' and "Line" sourced. After a hour or so I can lose the dot as welI. The Trg'd lamp remains without any trace. I have done initial checks and I'm not finding any obvious problems on the boards. I have done in circuit diode checks and found Diode CR433 on the A6 Interface (( Serial # B095740 and below) I have B095625) reads .239 V forward or reversed in diode check on my Fluke 87. Perhaps I can't get an accurate reading in circuit, but it was the only one reading the same low voltage both ways. Appreciate any thoughts,
Brent
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Re: OT Ripple Leader LTC-905

 

Do you have the manual for this unit? If not, you can download it from http://bama.edebris.com/manuals/leader/ltc905/ http://bama.edebris.com/manuals/leader/ltc905/. First thing I would do would be to verify the internal DC power supply voltages are correct and free of ripple (< 50mV P-P). If they have ripple, that could easily be the source of trouble.
Next thing would be to turn the AC plug around in the wall receptacle. AC leakage current through the power transformer could be causing the ripple. If reversing the power plug changes or eliminates the ripple, you might consider replacing the 2-wire AC power cord with a 3-wire cord with the mains safety ground connected to the curve tracer chassis.
Next, look at the Sweep Voltage power supply across R127. Make sure the scope ground is not connected to the unit at any other point than the scope probe ground clip The peaks of the sweep voltage waveform should be equal. If alternate peaks are different amplitude, suspect one or more of the rectifiers in the Sweep Voltage power supply.


Those suggestions should get you in the ballpark of the problem.


Dave M


---In TekScopes@..., <jmassen418@...> wrote :

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on the
display curves as displayed on my 2465A scope. The electrolytics in the box
have good ESR. Suggestions?

jerry

Tek 2215 Mod WV

Robert Simpson
 

Does anyone have any information about a 2215 mod WV? I just acquired a 2215 with mod WV and would like to know more about it. The mod puts some controls and inputs and outputs on the left side.
Thanks, Bob

Re: 7B92A No Sweep

 

The dual timebases are difficult to work on so I would start by
reseating anything installed into a socket like the ICs and reseating
all of the connectors.

Are the cam switches turning to follow the time/div controls?

I would consider acquiring an extender so you can gain freer access to
the plug-in while it is operating.

On 12 Feb 2017 21:59:46 +0000, you wrote:

Greetings,
My 7B92A has lost it's sweep in all aspects. I have only a dot, centered, and positionable from center to the left side of the screen. The dot widens to the right with faster sweep speeds: 50ms and up. I do have a trigger lamp on with the Trigger Level 'centered' and "Line" sourced. After a hour or so I can lose the dot as welI. The Trg'd lamp remains without any trace. I have done initial checks and I'm not finding any obvious problems on the boards. I have done in circuit diode checks and found Diode CR433 on the A6 Interface (( Serial # B095740 and below) I have B095625) reads .239 V forward or reversed in diode check on my Fluke 87. Perhaps I can't get an accurate reading in circuit, but it was the only one reading the same low voltage both ways. Appreciate any thoughts,
Brent

Re: Repaired a 7A13: thank you TekScopes people

 

The mainframe selection switch in the 7B92 and 7B92A affects the
holdoff timing but I do not know why it was needed. This part of the
7B80 is identical to the 7B50A which lacks this switch and the 7B50A
is specified to work in the slower mainframes so as far as I know, the
7B80 has no problems in a 7603.

The 7B50A also has the same fast trigger timing as the 7B80 so I do
not think that is a problem either in the slower mainframes.

On Mon, 13 Feb 2017 13:29:01 -0800, you wrote:

Hi Paolo,

I use them all the time in my 7603s. The plugin will work fine for most
measurements. This has something to do with how fast the timebase starts
after the trigger signal. Look through the 7B80 Service Manual for a switch
somewhere for which mainframe it is going into. The 7B80 manual will explain
it better than I can.

Dennis Tillman W7PF

Re: CRT noise (sound) and low +15V rail

Tomas Alori
 

Yes, I can make it slow down and even go the other way by changing the sweep speed. I'll look into the Z-Axis amp. I'll also try turning off the readout completely. Thanks!

Re: Repaired a 7A13: thank you TekScopes people

 

Hi Paolo,
I use them all the time in my 7603s. The plugin will work fine for most
measurements. This has something to do with how fast the timebase starts
after the trigger signal. Look through the 7B80 Service Manual for a switch
somewhere for which mainframe it is going into. The 7B80 manual will explain
it better than I can.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, February 13, 2017 8:30 AM
To: TekScopes@...
Subject: [TekScopes] Re: Repaired a 7A13: thank you TekScopes people

Thank you David for your advice. I replaced the twin capacitor of the
shorted one on the -15V supply line and the trace looks clean again. Before
it looked like something was not right, even if a different plugin than the
7A13 was chosen.

Now I am left with a 7B80 plugin that triggers but shows no trace. It is
full of "modern" electrolytics inside, so either a previous owner had
replaced them, or it was already designed that way. I do have a working
timebase, so it will probably rest few more years in a drawer with a visible
note of a possible area to look for the failure. I am left with a doubt: I
have a R7603 chassis, but 7B80 manual says it is for 7700, 7800, 7900
series. Could this be the cause of no trace showing up?!

Long live Tek instruments!
Paolo










------------------------------------
Posted by: ik1zyw@...
------------------------------------


------------------------------------

Yahoo Groups Links

OT Ripple Leader LTC-905

Jerry Massengale <jmassen418@...>
 

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on the
display curves as displayed on my 2465A scope. The electrolytics in the box
have good ESR. Suggestions?

jerry

2430A-2/2

Maxy Sac
 

Hello,


I’m back with new a issue.
First want to share what I did this time


I bought two 2430A on E-bay planning that if one had an issue, I could use the parts from the other to fix it.
The first one is older and, it has a separate battery on board for NV-RAM.
Second got DALAS NV-RAM.
The first had a couple issue and fixed, recap, calibrated, now it works fine.
Thanks you guys for the groups previous posts, it helped me a lot.


Second is in good condition inside and couple scratches outside.
Is there any sort of timer that tells me how long it has been running?


First change C706 and C816 (just in case because they were cracked)
With start, it showed a fail 4000, 6000, 7000, 8000, 9000.
The previous posts said that the most issued problem is that it is mostly
connected with NV-RAM chips, especially the 4722
and 4723 Low Battery on U350 and U664.
The original is DALAS DS1235ABW-120 (5 years on battery)
Found by Mouser DS1230AB-120 IND+
I de-soldered, then installed the IC socket, then I copied the chips, then I plugged it in.
Some of the previous fails disapeared, but some were still there.
After External calibration, the one that failed is 9000, even on tree time calibration.
9113 Slope for TRIGGER- A and 9300 REPET*
Ripple Voltages on regulator are in limits. Plan to recap later.
By Service manual, there were instructions for the fail 9000, so I followed ATG signal from U761 pin-2 to U370 by R368,
but signal does not show in manual for signal #99 on page 330.(MIL manual)
The normal mode is HIGH, in continues mode is series of TTL signal different length.
Sometimes if I exit continues mode , it shows pass on 9113. But after I restart it, it shows a fail on
9123 Slope TRIGGER-B and 9300 REPET*.
After another restart, it shows a fail to the previous 9113.
I checked on the first oscilloscope, ATG signal, and it was the same.
I tried to change U150 and U370 from first oscilloscope, there was the same output.



Now I need your help, thanks.

Re: Repaired a 7A13: thank you TekScopes people

 

A 7B80 will work fine in a 7603. It will even display more of the
leading edge because it triggers much more quickly.

When used in a slower mainframe like the 7603, the maximum accurate
sweep rate is limited by the mainframe's horizontal performance. For
the 7603, that is 50ns/div and 5ns/div with 10x magnification; I do
not remember any problems in the 7603 at the fastest unmagnified 7B80
sweep of 10ns/div; magnified sweeps of 2ns/div and 1ns/div were
inaccurate at the beginning of the sweep.

The 7B92A timebase has a jumper for fast and slow mainframes which
affects the minimum holdoff time but I do not think that is an issue
with the 7B80 because the 7B50A which is practically identical and has
the same holdoff timing also lacks the jumper and it is specified to
work in the 7603. I think this was a special design issue with the
7B92A which is older.

On 13 Feb 2017 16:30:05 +0000, you wrote:

Thank you David for your advice. I replaced the twin capacitor of the shorted one on the -15V supply line and the trace looks clean again. Before it looked like something was not right, even if a different plugin than the 7A13 was chosen.

Now I am left with a 7B80 plugin that triggers but shows no trace. It is full of "modern" electrolytics inside, so either a previous owner had replaced them, or it was already designed that way. I do have a working timebase, so it will probably rest few more years in a drawer with a visible note of a possible area to look for the failure. I am left with a doubt: I have a R7603 chassis, but 7B80 manual says it is for 7700, 7800, 7900 series. Could this be the cause of no trace showing up?!

Long live Tek instruments!
Paolo

Re: Repaired a 7A13: thank you TekScopes people

ik1zyw@...
 

Thank you David for your advice. I replaced the twin capacitor of the shorted one on the -15V supply line and the trace looks clean again. Before it looked like something was not right, even if a different plugin than the 7A13 was chosen.

Now I am left with a 7B80 plugin that triggers but shows no trace. It is full of "modern" electrolytics inside, so either a previous owner had replaced them, or it was already designed that way. I do have a working timebase, so it will probably rest few more years in a drawer with a visible note of a possible area to look for the failure. I am left with a doubt: I have a R7603 chassis, but 7B80 manual says it is for 7700, 7800, 7900 series. Could this be the cause of no trace showing up?!

Long live Tek instruments!
Paolo

Re: Tek 2465 timebase issue - FIXED

Mark
 

Well,

Having broken a component during removal I can state that the problem was
EITHER C72 0.47uF (as suggested by Craig - thanks) or R724 (the replacement
for which I have had to make using 2 resistors).

Both have been replaced and the sweep times on all settings are close to the
money - I need to re-calibrate now :-(

So I think it's time to do the PSU cap replacement and fix the rattling fan,
but it looks like I'm back in business with this 'scope.

Thanks to all who offered suggestions.

Mark

-----Original Message-----
From: Mark, G0MGX [mailto:@G0MGX]
Sent: 11 February 2017 17:25
To: TekScopes@...
Subject: RE: [TekScopes] Tek 2465 timebase issue

Yes, it should have been a "B" - eyesight not what it used to be!

Can we age this from the serial number?

Mark

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 11 February 2017 16:10
To: TekScopes@...
Subject: Re: [TekScopes] Tek 2465 timebase issue

I suspect that is really B025365 (not 8025365)

Anyway the later USA versions did change "officially" to 1.78B/5.36K at
serial B028680


Dave

manuals@...


On 2/11/2017 10:56 AM, 'Mark, G0MGX' @G0MGX [TekScopes] wrote:

8025365

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 11 February 2017 15:56
To: TekScopes@...
Subject: Re: [TekScopes] Tek 2465 timebase issue

R736/R737 were changed to 1.78K/5.36K in the 2465A (or possibly in
later models of the 2465)

What is the serial number of your 2465?

Dave

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Re: X10 probe in series with X20 attenuator question

Albert Otten
 

(continued) Note that my calculations were for the DC attenuation. The input capacitance of the attenuator is not specified and could very well mismatch the capacitance expected by the probe. It's also not specified which 'scope input capacitance is expected by the attenuator. The effect on total attenuation at higher frequencies AC can be quite large.
Albert