Date   

Re: 2445A slow

Steve
 

Thank you for the tip chuck! I sincerely appreciate all the help. If I can ask one last question or two. I know you upped a few caps to 330uf which while upping voltage is ok upping value generally speaking is not. I’m just curious for the reasoning in increasing the value. And ironically I have on hand Nichicon uvz 3.3uf 350v as I had to recap a pioneer reel to reel machine. I had purchased twenty and thought I’d never use another one of those caps. Boy was I wrong, glad I have them now.

--
Kind Regards,

steve


2465 Recap - Trace Returns, But Jumping Everywhere

Don N3DEB
 

I posted last year regarding a 2465 (with GPIB option) that died after swapping out a hybrid to diagnose another scope.The donor was working fine until the hybrid was returned and the scope turned on. Trace was gone, turning up the grid bias gave the typical rows of dots verifying a heartbeat. The symptom was very much like the other scope's Z-Axis hybrid failure, which threw me off initially.

Power supply voltages were within tolerance, some ripple was on the high side but did not seem to be enough to kill the trace. Wrong.

Just recapped the power supply boards using the parts list floating around group, trace back sharp and bright but with issues. I logged every step, measuring and keeping old caps. C1113 and C1116 were the obvious failures. A Hakko FR-301 desoldering tool drops the parts out quickly and clean - amazing.

My theory is that because this repair scope was seldom used, power cycling cause a coincidental power supply fail that boosted ripple. This killed the trace and probably killed U2435 on the A5 Control board.

Some of the most conclusive troubleshooting results:

1) Trace jumps above and below visible screen area with sweep starting right of left screen edge.
2) Position controls have very little or no affect on trace, on any channel. Ch3 & Ch4 are somewhat more stable than Ch1 & Ch2.
3) Shorting vertical output at Delay Line test point brings trace back to center, suggesting the issue is before Vertical Output Amp.
4) Calibrator signal viewed on test scope via Ch2 Out of repair scope is nearly perfect on a test scope, with just a little flicker in sync with the repair scope trace jumps.
5) +5v, -5v power to U2435 all good but most voltage checks on pins do not match the test 2465 scope.
6) Dly Ref 0 at A1J118 Pin 2 - STUCK at +1.17v, does not vary as it should by changing REF Delay Position pot.
7) DAC Current Reference TP503 +1.367v, TP504 -1.253v. Good.
8) A1C853, A1C854 lifted leg, both correct capacitance. Dissipation factor similar to new cap. (DE-5000 meter)
9) U800 pin 18 sweeps look reasonable with DMM, -1.25v to +1.25v.

Conclusion - replace U2435?

Thanks for the help,
Don


Re: Tektronix 2465, 2465A, or 2465B

@0culus
 

Thanks for explaining further. Honestly, I'll open it up at some point I'm sure because if it needs service, I will be doing it myself. I'm not terribly worried whether it's real or not. It seems to perform perfectly fine with everything I've thrown at it, and I've never run into any anomalies that suggest it isn't performing to 2465B specs. And, as I mentioned, it's really more of a back-up to my 7904A and 7104 now.

And, if I'm being really honest...if I get another 24xx series scope it would probably be a 2467 series rather than a 2465 series, if I could find one with a gently cared for mcp tube. The mcp crt is really a feat of engineering around physics, and makes working with the timebase turned way up a treat.

Sean

On Fri, Apr 3, 2020 at 04:36 PM, Chuck Harris wrote:


Confusion is my fault. I was running down
two different trains of thought at the same
time.

In letters to me, Alex bragged that he knew
how to adjust the frankenscopes so that the
bandwidth was even better than the real 2465B.

He claimed that this was because in removing
the bandwidth limiting network he removed all
limitations of the hybrid... even the 2465B
has a network that matches the spiral delay line,
that limits bandwidth a little... So he said.

However, when I calibrate scopes, I have to
meet more than just the bandwidth specification.
I have to also meet the transient response
specifications.

What good is a scope that has a wide 3dB point if
it distorts the amplitude at other frequencies?

A real 2465B will just barely meet the bandwidth
spec when the transient response is adjusted
to specification. A frankenscope will not get
even close. It reaches 150MHz to 300MHz at best.

It largely depends on how bad the vertical preamp
hybrids were that they failed the 2465B culling
tests. In many later scopes, the factory was
so good at making the parts, that they apparently
ran out of culled parts for the 2445B's, and used
real 2465B parts in the 2445B.

Alex sometimes swaps out the 2445B vertical preamp
hybrids for 2465 hybrids.

I have had several customers send me faux 2465B's
for calibration... And I have had the sad task
of informing them that I cannot calibrate their
scopes because they were not really 2465B's..they
were the victims of Alex's fraud.

I am not going to comment on the quality of Alex's
refurbish jobs.

Look inside. It is better that you know what you
really have. You might see a nice real 2465B, and
pass it up, when maybe you shouldn't.

-Chuck Harris


TDS2014 Not Booting

Factotum Industries
 

Hello everyone!

I was lucky to acquire the above scope from a flea market last year and has become a workhorse on my bench.

Sadly it has recently stop booting (only seems to boot 1 in 50 times and usually after a long rest - maybe when cool?)

The voltages from the PSU are within spec. I have display back light but no 1kHz (I get something odd like 104kHz).

This seems to point to the main board.

Anything I should focus on? Would love to get this unit up and working again (and let's face it - I can't afford a new one in this climate).

Thanks in advance,

Anton.

--


Re: Ringing on 2235 100 volt supply

barry.ballenger@...
 

John, I can get you the info tomorrow, I have several 2235s in the process
of being redone. I may even have a couple of the screws extra.

On Fri, Apr 3, 2020 at 9:07 PM John G <mnjgfl@...> wrote:

I finally got around to replacing the "Sweep Gain" adjustment pots
(Digi-Key # 3329H-102LF-ND) and recapping it. My problem is the screws
that secure the front of the attenuator board from the bottom. I can't seem
to find the right one's. Either too short to hold or too long and they bind
up the input coupling switch. Any one know what length they should be? The
service manual doesn't have a description.
Picture of location:

https://groups.io/g/TekScopes/photo/242594/0?p=Created,,,20,2,0,0

Thanks
John




Re: 2465 U950 Z AXIS IC Chip 155-0242-01 Fails After Re-installation

Don N3DEB
 

I recapped, with interesting results. I will start a new thread as this title is misleading with the sequence of my wording. I meant that the scope failed, after the swapping of the U950.

For those who want to follow the new thread is "2465 Recap - Trace Returns, But Jumping Everywhere"


Re: Ringing on 2235 100 volt supply

John G
 

I finally got around to replacing the "Sweep Gain" adjustment pots (Digi-Key # 3329H-102LF-ND) and recapping it. My problem is the screws that secure the front of the attenuator board from the bottom. I can't seem to find the right one's. Either too short to hold or too long and they bind up the input coupling switch. Any one know what length they should be? The service manual doesn't have a description.
Picture of location:

https://groups.io/g/TekScopes/photo/242594/0?p=Created,,,20,2,0,0

Thanks
John


Re: 2430A Fails Repet

Rich Frahm
 

Thanks Victor. That doesn't sound too bad. I think for now I'll use it a bit and see if the problems persist, and if so how annoying they are. If they get too annoying I'll see if I can clean them up.

Rich


Re: Capacitor testing

 

Apply a slow charge to the cap with a resistor to allow the electrodes to reform electrochemically. Charge to about 80% of rated voltage and hold it there for a few hours. Cap. performance should be ok then.
I've been playing with supercaps this year...so that's how to get proper performance and low leakage currents.
~Ancel


Re: Tektronix 2465, 2465A, or 2465B

 

Hi Harvey,

You have NO idea of what I'm talking, but I think you do some (I write in English, or at least I try to). You also have an interesting technical history.
I hope I can stop my electronics infection before I reach your collection of instruments, and can put all my electronic stuff away in a nice protected place to return to it in 10 years.

My challenge when calibrating a scope is to start with nearly nothing, just first principles. I can calibrate a time base starting with the AC 60 Hz, and calibrate the amplitude reading using the calibration of my DVM. No help from the National Bureau of Standards. And I have some function generators that let me adjust the frequency responses with square waves, impulses, like Chuck gave its importance. Frequency bandwidth can be what it wants to be.
Besides time and amplitude, what else needs calibration in a scope? The intensity is variable...

Regards,
Ernesto


Re: Tektronix 2465, 2465A, or 2465B

Harvey White
 

Hmmm, not that I have ANY idea of what you're talking about.

There's a 7704A, and a 7704A with a mod...(don't remember the number).  The mod extends the calibrated bandwidth to either 225 or 250 Mhz.

Having said that, I tend to use the 7904 scopes I have (the 7704A is a backup if everything turns to nasty brown squishy stuff...). The 500 Mhz bandwidth is frequently useful when I look for timing glitches in FPGA projects.  It all depends on what you're trying to debug.

The main advantage of the 7000 series is plugins, which extends the input range in many different directions, all of which depend on what you try to do.  Do you need one?  Not necessarily.  Do you *want* one?  Up to you.   <grin>

I started with a heathkit OM3, which maybe did 1 MHZ, then I got a Tek 512, and then a 513D, which served for a number of years.  I did build a heathkit scope on a breadpan (literally) with an external power supply and a surplus CRT.  (seriously).  It served for a number of years, but had absolutely no calibration.  Did that somewhere after I had the OM3.  The OM3, if you're careful with the Z axis modulation, can take a video signal from a TV tuner and IF chain, then modulate the CRT Z axis.  You'll need a 60 Hz video sweep generator (for NTSC).  All of that is long in the past, though.  I think I had to add the Z axis modulation, though.

From then the next scope was a Telequipment scope (which needed some work eventually), then a Kenwood 4 channel scope, then a 2430A, then I went into the 7704 series, then 7904, then finally found a 7104.  Somewhere in there I got a 7834 storage scope, a number of 468 scopes, and some SC504 scopes.  All depends on what you wanted to do with them.

What I find nice (engage smug mode) is that when I go to calibrate a scope, and it says "you need this......." I can reach up on the shelf and get the equipment.  It took a bit of work and dedication, though.  Do you need it all?  I don't have it "all", but there's always a workaround.

You make do with what you have, and what you can get.  No one right way.

Harvey

On 4/3/2020 7:13 PM, Ernesto wrote:
Hi @Oculus,

Darn! Now that I am finishing with my repairs of old stuff and itching to have time again for my retiree activities, I feel drawn into fixing my old 7704A with its fine plugins. It has been so long since I saw its traces and readouts, I will get emotional when I see these again. And you throw gas in the fire writing how nice the 7000 machines are! This year I have been infected with a virus, not covid-19 but the one that spreads the passion of electronic analysis and design. It all started with my sister suggesting that I listen again to my old 33 rpm records, so I dusted off the fine direct drive turntable, plugged it in, and it smoked! I HAVE to repair this, was my reaction, so... I may need an oscilloscope for that I should swear that the 7704 is the last project. But if I keep reading TekScopes I'm not so sure. Since I started with it two months ago I have now over 800 messages.

Ernesto



Re: 533 scope

 

Hi Tom,

You turned the scope on, and it didn't start a fire. Good.
The next thing you could do is play with the Time Base, with sweep in Auto and various sweep rates, and see if the two horizontal neons on top of the CRT blink.
Also, if you have a plugin, move the positions and see if the vertical neons change, or at least tell you where the vertical amp's output is at.
If you get these results, the scope may be alive, and just has its eyes closed.

Next step can be to measure the outputs of the regulated supplies. In the 533 all voltages are high enough to be dangerous, up to 500V, This should be more concern than the 10 KV for the CRT, which is well hidden.

Finally, if all looks fine but there is no trace, the time comes to look at the HV supply, with a formal or improvised HV probe.

I enjoy browsing the service manual of the 533, which seems to be a grandfather of my 547.

Regards,
Ernesto


Re: 184 Time Mark Gen. - 2nS & 5nS not working

Tom Gardner
 

On 04/04/20 00:28, david via groups.io wrote:
I don't have an oscilloscope with enough bandwidth to check the 200Mhz or the 500Mhz output. My 465 is 100Mhz and it doesn't have a trigger setting fast enough to trigger on the 200Mhz. My digital scope is 50Mhz but trigger goes to 5nS so I can see the 200Mhz. I think the bandwidth is why I'm only seeing 88mV peak to peak @ 200Mhz., If the 500Mhz is supposed to be 300mV peak to peak would I still be able to see it?
David
My 350MHz Tek 485 displays and triggers on a 1GHz signal. Naturally the trace's amplitude is significantly reduced.

The triggering continues to work, provided trace amplitude is >0.2 divisions.


Re: 2445A slow

Chuck Harris
 

To avoid mistakes know a couple of things:

1) all capacitors have their "+" leads pointing in the
same direction.
2) only remove one *type* of capacitor at a time, and
replace it before you move on. There are marking errors
on some versions of the supply that can cause you to swap
two capacitors to one capacitor's peril.

-Chuck Harris

Steve wrote:


Thank you for your info on that, I looked but I didn’t see any leakage but I also know that doesn’t mean anything. I will go ahead and recap the LV supply if it’s an hour job, I can afford an hour. I will recap the LV supply according to Chuck’s message.


Re: Tektronix 2465, 2465A, or 2465B

Chuck Harris
 

Confusion is my fault. I was running down
two different trains of thought at the same
time.

In letters to me, Alex bragged that he knew
how to adjust the frankenscopes so that the
bandwidth was even better than the real 2465B.

He claimed that this was because in removing
the bandwidth limiting network he removed all
limitations of the hybrid... even the 2465B
has a network that matches the spiral delay line,
that limits bandwidth a little... So he said.

However, when I calibrate scopes, I have to
meet more than just the bandwidth specification.
I have to also meet the transient response
specifications.

What good is a scope that has a wide 3dB point if
it distorts the amplitude at other frequencies?

A real 2465B will just barely meet the bandwidth
spec when the transient response is adjusted
to specification. A frankenscope will not get
even close. It reaches 150MHz to 300MHz at best.

It largely depends on how bad the vertical preamp
hybrids were that they failed the 2465B culling
tests. In many later scopes, the factory was
so good at making the parts, that they apparently
ran out of culled parts for the 2445B's, and used
real 2465B parts in the 2445B.

Alex sometimes swaps out the 2445B vertical preamp
hybrids for 2465 hybrids.

I have had several customers send me faux 2465B's
for calibration... And I have had the sad task
of informing them that I cannot calibrate their
scopes because they were not really 2465B's..they
were the victims of Alex's fraud.

I am not going to comment on the quality of Alex's
refurbish jobs.

Look inside. It is better that you know what you
really have. You might see a nice real 2465B, and
pass it up, when maybe you shouldn't.

-Chuck Harris


sdturne@q.com wrote:

Chuck,

I'm confused. Below in the message quoted, you state that the adjustments can be twiddled to fake the frequency response, but above you stated: "If you test the bandwidth, you will find the 3 dB point is somewhere between 150MHz, and 300MHz." It can't be both.

I'll have to set up the measurement again, and see how it behaves as it's been a while. I do remember paying rather a lot for it, but at the time it seemed worth it to get one that wasn't a capacitor bomb waiting to happen. Nowadays I'm more confident with making my own repairs, so my decision probably would be different now!

Sean


Re: 2445A slow

Steve
 

Thank you for your info on that, I looked but I didn’t see any leakage but I also know that doesn’t mean anything. I will go ahead and recap the LV supply if it’s an hour job, I can afford an hour. I will recap the LV supply according to Chuck’s message.
--
Kind Regards,

steve


Re: 184 Time Mark Gen. - 2nS & 5nS not working

david
 

I don't have an oscilloscope with enough bandwidth to check the 200Mhz or the 500Mhz output. My 465 is 100Mhz and it doesn't have a trigger setting fast enough to trigger on the 200Mhz. My digital scope is 50Mhz but trigger goes to 5nS so I can see the 200Mhz. I think the bandwidth is why I'm only seeing 88mV peak to peak @ 200Mhz., If the 500Mhz is supposed to be 300mV peak to peak would I still be able to see it?
David


Re: 184 Time Mark Gen. - 2nS & 5nS not working

Tom Gardner
 

ISTR I improved my 500MHz oscillator's output by modifying the coupling in the L69/L70 transformer.

Yup, I pushed the L70 wire so the two halves of the transformer were closer together :)

I also kept in mind that the purpose is to provide timing accuracy, not amplitude accuracy. Sometimes life is too short.

Oh, I did buy a NOS nuvistor for around £10.

On 03/04/20 21:24, Dave Seiter wrote:
I've had three 184s over the years, and I've never had one in which the 2 and 5nS sections worked correctly.  I gave up trying to fix the last one.  Maybe if you get some good leads I'll give mine another go (since I have so much time on my hands anyway!)
-Dave
On Friday, April 3, 2020, 01:06:15 PM PDT, david via groups.io <davide_us=yahoo.com@groups.io> wrote:
Only issue I have left to fix is the 5nS sine output is only 88mVpp. should be minimum of 0.3Vpp, and the 2nS sine output is not working at all. Have 100Mhz  3.7Vpp at input to 2nS board, no output. Have 2Vpp 100Mhz at input to 5nS board, only 88mVpp @ 50 ohm 200Mhz at output. Can any one help? I am wondering if either of the tubes V60 or V70 on 2nS board could be bad. Is there any way to check?  Is it possible that the 5nS output is only 88mV because of the low input of only 2Vpp ? Could the forward voltage drop on the diodes of the doubler  be that much?


Re: A sick 7603 can it be restored?

bobh@joba.com
 

If you have a bad filter cap, with high ESR, one thing you can do to prove to yourself that you found the real issue is to parallel the questionable cap with a good one.   If the unreg supply and the other supplies come back you found the problem.  This was suggested to me when I was in your place and it worked.

Bob.

On 4/3/2020 6:35 AM, Eric wrote:
Well before I do anything else I have to address the capacitor issue. Got the scope hooked up to the -50V rail and there is 260mV pk-pk of ripple . It is a nice clean saw tooth generator at the moment. Glad I had it on the current limited supply. The reading was on the -50V test point on the regulator board. I guess I am tearing down the power supply. Spec for the Ripple is only 5mV pk-pk

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of bobh@...
Sent: Friday, April 3, 2020 9:04 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] A sick 7603 can it be restored?

The -50V supply depends on the +50 unregulated voltage. The 130 V supply also depends on a good +50 V. You might want to check the caps
C808 and C809 that's where I found a bad cap when troubleshooting mine.

bob.

On 4/2/2020 9:15 AM, Eric wrote:
That is very true. I am going to get it on the bench again tonight I have a sneaking suspicion I have a massive ripple problem given what I saw on the scope last night. I was able to confirm that the plugins will generate a trace on a working 7K frame so that is good. The -50 is the main reference supply for the frame.

What I saw last night was I was getting very now intensity pulses on the z output of the main board. But it looked like they were riding on about 40mV pk-pk of ripple so I am pretty sure that is not supposed to be there. Getting to the bulk caps in these is a nightmare but hey that is where the fun is.

Eric
-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Oz-in-DFW
Sent: Thursday, April 2, 2020 12:05 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] A sick 7603 can it be restored?

Its been forever since I worked on one. One dim memory I have of these is that all the supplies are interrelated. Anything dragging one down messes up all of the others. They were a pain to troubleshoot.










Re: Tektronix 2465, 2465A, or 2465B

 

Hi @Oculus,

Darn! Now that I am finishing with my repairs of old stuff and itching to have time again for my retiree activities, I feel drawn into fixing my old 7704A with its fine plugins. It has been so long since I saw its traces and readouts, I will get emotional when I see these again. And you throw gas in the fire writing how nice the 7000 machines are! This year I have been infected with a virus, not covid-19 but the one that spreads the passion of electronic analysis and design. It all started with my sister suggesting that I listen again to my old 33 rpm records, so I dusted off the fine direct drive turntable, plugged it in, and it smoked! I HAVE to repair this, was my reaction, so... I may need an oscilloscope for that I should swear that the 7704 is the last project. But if I keep reading TekScopes I'm not so sure. Since I started with it two months ago I have now over 800 messages.

Ernesto