Hi all,

I joined this group after buying my second Tek Scope, a 2465, at a very good price because it has begun to deteriorate. So now I am cleaning up my 2465. I am hoping to get clear, clean traces and better utility than my 2235 I have been using. I will apreciate any and all advice, suggestions, etc. I get fom the other members here.

My first complaint is the vertical channels 1 and 2 have a sawtooth noise on the trace. Channels 3 and 4 are clean and clear. The sawtooth on Channels 1 and 2 looks to be about 25 kHZ with an amplitude that is greater when the trace is farther from the center. In fact, the traces are clear and clean if they are centered vertically with no input. Changing vertical position causes the sawtooth to appear and it grows as the trace is moved farther from center. Its magnitude diminishes as the scope warms up but never goes away.The sawtooth seems to ride on top of the calibration waveform as it is viewed on the trace (the calibration looks clean when viewed in Channels 3 and 4). So my opinion is the sawtooth is added to the measured signal and trace position somewhere in the vertical pre-amp(s). Also, measured ampltudes on channels 1 and 2 seem about 60% of actual but amplitudes on Channel(s) 3 and 4 seem about right (certainly within calibration range).

My second complaint is the alphanumeric readout text is more blurry than I remember from years ago. But it could just be that my eyes are more blurry, lol. But I remember the text being as crisp and clear as the traces when I was working. (But I cant be certain I was using a 2465, it could have been 2465A or 2465B). I only know if I can, I will sharpen the text.

My third complaint is the LED indicators for switch position seem a bit dim. But then again, it may be my eyes goign dim, lol.

Neither complaint 2 nor 3 are important, but complaint 1 is a show stopper I must repair.

My question of any kind and knowledgable soul is: "Do you think its worth repairing or do I have a bag of parts?" I think its well worth repairing but would apreciate knowledgable advice. Its a 2465, not 2465B, and it appears to have been refurbed/recaled in the late 90's (sticky labels on EEPROMS say 1996).

If its worth the repair I would recap the LVPS as others here have done, that seems simple enough and an obviously wise investment. In fact, this recap may correct the vertical sawtooth and perhaps the blurry text. But I dont think it will change the vertical gain/calibration to correct for the 40% error.

I really dont want to do major work on the Main board (A1) because that can be extensive. But I will if its simple enough and likely to work. These are great scopes and this one is cosmetically very good.

I WILL also add cooling of some kind to U800 if everything else turns out OK.

So what do you think? repair/refurb or part it out and look for something else?

----- Original Message -----

From: stan_katz

To: TekScopes@...

Sent: Sunday, February 24, 2013 8:21 PM

Subject: [TekScopes] Re: 475 Triggering Issue -- Will recent 468 Triggering Issue Thread Help Me?

?

SOLVED...while pin 3 of U520 had a good copy of the waveform being triggered on, the DC voltage on pin 3 was 1.6v. I found the U520 pin voltages posted by Tom Miller and noted that proper voltage for pin 3 should be .7v. In addition, the base of Q526 had almost 1 volt on it. Not right! I don't have a curve tracer but a simple DMM probing of the diff amp JFETS proved Q522 was blown. Ordered another matched pair and my 475 is back on the air. Now...with all my troubleshooting cal. tweaks behind me, this scope can really use a good calibration. Whew!

Thanks - Tom, David, Max, Albert, et.al
Stan

--- In TekScopes@..., "raymonddompfrank" wrote:
>
> OK, glad to hear that!
>
> Raymond
>
> --- In TekScopes@..., "stan_katz" wrote:
> >
> > I purchased original NOS Tektronix p/n tunnel diodes listed in the 475 manual.
> >
> > --- In TekScopes@..., "raymonddompfrank" wrote:
> > >
> > > I haven't followed this thread but noticed that you purchased new TD's and as David says, your adjustments seem to be (quite far) off.
> > > Did you purchase the right TD's? They're not all the same!
> > > Peak currents vary from 1mA to more than 10mA. They need appropriate biase adjustments!
> > >
> > > Raymond
> > >
> > > --- In TekScopes@..., David wrote:
> > > >
> > > > If those low profile socket elements are the ones I am thinking of,
> > > > they are called Miniserts. I have had at least two incidents now
> > > > where a Minisert was open and reseating the lead at least temporarily
> > > > fixed the problem.
> > > >
> > > > There is a datasheet for them in the files area:
> > > >
> > > >
> > > >
> > > > Q532 (and Q526) are operating as emitter followers. The emitter
> > > > voltages for each are low impedance and should be about 0.6 volts
> > > > higher than their base voltages at all times. They are just used as
> > > > simple voltage buffers.
> > > >
> > > > Trigger B is completely independent from trigger A and is only used if
> > > > a sweep mode other than A internal is selected.
> > > >
> > > > From your description I suspect everything is working but that the A
> > > > trigger circuit needs to be calibrated:
> > > >
> > > > R534 is used to center the trigger point vertically on the CRT when
> > > > R530 is in the middle of its rotation.
> > > >
> > > > R673 adjusts the trigger view vertical positioning on the CRT.
> > > >
> > > > R547 adjusts the trigger level so that it does not change when the
> > > > slope is changed.
> > > >
> > > > R565 adjusts the tunnel diode threshold for maximum sensitivity.
> > > >
> > > > On Wed, 20 Feb 2013 02:17:18 -0000, "stan_katz"
> > > > wrote:
> > > >
> > > > >I know I've let this thread go cold, but I assure members it wasn't out of neglect. For one thing, I was advised to read the manual, and I have been doing so. In the meantime, I had been monitoring the trigger diodes by clipping scope probes on their anodes. I intended on recording waveforms with my digital camera. Alas, I found the camera was fried. Nevertheless, I decided to do some more examination of the Trigger A circuits. I took hold of one of the probes attached to a tunnel diode, intending to disengage it. The instrument was powered on. The probe came off the board, WITH THE TUNNEL DIODE STILL ATTACHED to the probe! The diode had no sign of being soldered in. I turned off the instrument, and pulled on the other tunnel diode, and it came out. No solder. Now it sunk in. Those phosphor/bronze stakes weren't hiding solder pads underneath, they were all sockets! I must have missed that in some FAQ or manual addendum. The only semiconductors soldered in my 475 are small signal
> > > > >diodes. Who knows if my probes were intermittently yanking out the anode ends of the TDs. I certainly wasn't going to waste members' time by trying to diagnose TD damage. I bit my lip, and purchased two NOS tunnel diodes for $OUCH.00. As least this message would start with good tunnel diodes.
> > > > >
> > > > >Following David's advise to do a modified 5-40 trigger A calibration from just Channel 1 input lead me nowhere. The scope wouldn't trigger on the 12mv p-p 350khz sine wave I was using to obtain a .32 division height on the CRT. Adjusting R565 had no effect. Lowering the attenuator and filling the screen with the signal also had no effect. I then returned the trigger level to full + ( clockwise ), attenuator down to 50mv, and with the waveform filling the screen, I got trigger lock. I did note, that during the modified 5-40 calibration attempt, there was no sign of the trigger signal with TRIG VIEW depressed. However, with the intentional misadjustments reported above, I could just see some light at the top of the screen in TRIG VIEW. Although I was advised not to start messing with anything but R565, I adjusted R534 in the "misadjusted" state using TRIG VIEW. The waveform came into view, and I could center it. With this set of adjustments, I could now trigger on the 12mv waveform
> > > > >with the attenuator turned up to .1v so that I could meet the .32 divisions performance called out in 5-40. I thought I was on to something regarding the trigger centering. I esr'ed all the electrolytics in the triggering section. All checked out. A separate check with a VOM didn't show shorted electrolytics. I thought there may be a fault with U520, and given both it, and U720 were both socketed, I swapped them. No change. I haven't been able to find any shorted bypass caps..yet. I replaced Q532, and two resistors that were more than 50% out of spec. No go. One thing that bothers me is that, on the schematic, the emitter of Q532, is pulled up through R535 to +8.2v. I only measure +5.0v. I can't find any errata that verifies my measurement. The 8.2v source is functioning as it is available everywhere else noted on partial A8 schematic with trigger circuit. Trigger level at pin 14 of U520 varies from 1.7v (full + level) to 200mv (full - level). Is this OK? TP526 has a copy of the 12mv
> > > > >waveform as expected. I'm fixated on the centering circuit, but can go no further. With HORIZ DISPLAY on A LOCK, there shouldn't be any interaction with TRIG B? Right? I suppose trimmer 534 could be bad, but checking that out requires flipping A8. Yeesh! I haven't messed with R673 yet, as my troubleshooting has been with AC coupling only. Should I go there?
> > > >
> > >
> >
>

OK, glad to hear that!

Raymond

--- In TekScopes@..., "stan_katz" <stan_katz@> wrote:

I purchased original NOS Tektronix p/n tunnel diodes listed in the 475 manual.

--- In TekScopes@..., "raymonddompfrank" <r.domp.frank@> wrote:

I haven't followed this thread but noticed that you purchased new TD's and as David says, your adjustments seem to be (quite far) off.
Did you purchase the right TD's? They're not all the same!
Peak currents vary from 1mA to more than 10mA. They need appropriate biase adjustments!

Raymond

--- In TekScopes@..., David <davidwhess@> wrote:

If those low profile socket elements are the ones I am thinking of,
they are called Miniserts. I have had at least two incidents now
where a Minisert was open and reseating the lead at least temporarily
fixed the problem.

There is a datasheet for them in the files area:



Q532 (and Q526) are operating as emitter followers. The emitter
voltages for each are low impedance and should be about 0.6 volts
higher than their base voltages at all times. They are just used as
simple voltage buffers.

Trigger B is completely independent from trigger A and is only used if
a sweep mode other than A internal is selected.

From your description I suspect everything is working but that the A
trigger circuit needs to be calibrated:

R534 is used to center the trigger point vertically on the CRT when
R530 is in the middle of its rotation.

R673 adjusts the trigger view vertical positioning on the CRT.

R547 adjusts the trigger level so that it does not change when the
slope is changed.

R565 adjusts the tunnel diode threshold for maximum sensitivity.

On Wed, 20 Feb 2013 02:17:18 -0000, "stan_katz" <stan_katz@>
wrote:

I know I've let this thread go cold, but I assure members it wasn't out of neglect. For one thing, I was advised to read the manual, and I have been doing so. In the meantime, I had been monitoring the trigger diodes by clipping scope probes on their anodes. I intended on recording waveforms with my digital camera. Alas, I found the camera was fried. Nevertheless, I decided to do some more examination of the Trigger A circuits. I took hold of one of the probes attached to a tunnel diode, intending to disengage it. The instrument was powered on. The probe came off the board, WITH THE TUNNEL DIODE STILL ATTACHED to the probe! The diode had no sign of being soldered in. I turned off the instrument, and pulled on the other tunnel diode, and it came out. No solder. Now it sunk in. Those phosphor/bronze stakes weren't hiding solder pads underneath, they were all sockets! I must have missed that in some FAQ or manual addendum. The only semiconductors soldered in my 475 are small signal
diodes. Who knows if my probes were intermittently yanking out the anode ends of the TDs. I certainly wasn't going to waste members' time by trying to diagnose TD damage. I bit my lip, and purchased two NOS tunnel diodes for $OUCH.00. As least this message would start with good tunnel diodes.

Following David's advise to do a modified 5-40 trigger A calibration from just Channel 1 input lead me nowhere. The scope wouldn't trigger on the 12mv p-p 350khz sine wave I was using to obtain a .32 division height on the CRT. Adjusting R565 had no effect. Lowering the attenuator and filling the screen with the signal also had no effect. I then returned the trigger level to full + ( clockwise ), attenuator down to 50mv, and with the waveform filling the screen, I got trigger lock. I did note, that during the modified 5-40 calibration attempt, there was no sign of the trigger signal with TRIG VIEW depressed. However, with the intentional misadjustments reported above, I could just see some light at the top of the screen in TRIG VIEW. Although I was advised not to start messing with anything but R565, I adjusted R534 in the "misadjusted" state using TRIG VIEW. The waveform came into view, and I could center it. With this set of adjustments, I could now trigger on the 12mv waveform
with the attenuator turned up to .1v so that I could meet the .32 divisions performance called out in 5-40. I thought I was on to something regarding the trigger centering. I esr'ed all the electrolytics in the triggering section. All checked out. A separate check with a VOM didn't show shorted electrolytics. I thought there may be a fault with U520, and given both it, and U720 were both socketed, I swapped them. No change. I haven't been able to find any shorted bypass caps..yet. I replaced Q532, and two resistors that were more than 50% out of spec. No go. One thing that bothers me is that, on the schematic, the emitter of Q532, is pulled up through R535 to +8.2v. I only measure +5.0v. I can't find any errata that verifies my measurement. The 8.2v source is functioning as it is available everywhere else noted on partial A8 schematic with trigger circuit. Trigger level at pin 14 of U520 varies from 1.7v (full + level) to 200mv (full - level). Is this OK? TP526 has a copy of the 12mv
waveform as expected. I'm fixated on the centering circuit, but can go no further. With HORIZ DISPLAY on A LOCK, there shouldn't be any interaction with TRIG B? Right? I suppose trimmer 534 could be bad, but checking that out requires flipping A8. Yeesh! I haven't messed with R673 yet, as my troubleshooting has been with AC coupling only. Should I go there?

?

I had a depressing experience last week. I bought my 2nd can of WD40 in forty years. (Yes I don't spray it on everything and that's why the can lasted 40 years.) First can was bought over the counter in about 1971. The second can had to be trucked rather than flown from the supplier in another city and it came with 20, count 'em, 20 pages of health and safety instructions.

EJP

Hi,
I'm out of town now but will be back by end of week. I keep getting kicked out as this is my 4th attempt to post. Ohms are high, in the k to m range.


--- In TekScopes@..., "Tom Miller" wrote:

Take a resistance measurement from L558 to ground and report it here.

The unregulated 32 volts should be fairly high without any (fuse blown) load. Under normal conditions, it should be about +51 volts.
With a blown fuse, I don't see how you would measure any voltage on the 95 volt test point.


Regards,
Tom

----- Original Message -----
From: Bob
To: TekScopes@...
Sent: Monday, January 14, 2013 10:49 PM
Subject: [TekScopes] Re: 465M blows internal .25A fuse



Hello,
I know this is an old post but I'm having the same problem ,only the power supply side of the blown fuse measures +58vdc. Is this higher voltage due to bad caps blowing the 1/4 amp fuse or is this voltage within a normal range for the unreg +32 volts?
Have a great day,
Bob

--- In TekScopes@..., "Bloy2004" wrote:
>
> I have a 465M scope and after a while the display went dead.
> Examining the internals revealed the 1/4A fuse was blown and
> continues to blow after replacement. I have a manual, but nothing
> is said about causes for this fuse blowing. Without the fuse in
> place, I get +55VDC from the power supply Cap side (+32VDC
> unregulated), and +.5VDC from the HV transformer side (pin 4 of part
> T550). Where there should be +95VDC, I get only 11.4 VDC.
> Questions:
> 1.What are the most likely causes for this fuse blowing, when all
> was working fine.
> 2.What are the poosible causes for the +95Vdc to be way low.
>
>
> Any responses welcome...
>

From: Chin Siang Lim
Subject: [TekScopes] Re: New here with a 2465 to clean up
To: TekScopes@...
Date: Sunday, February 24, 2013, 6:26 PM

?

Great piece of temperature measurement by Patrick.

The grp can consider two ways to measure the temp with cover on:

1. Use a good thermister- EPCOS B57862S282A9 Miniature Bead Thermistor. Not so accurate but god enough since you can compare with surrounding Ics. Accuracy up to? 1 to 2degree C is achievable. ?US 50cents per piece, ?Ebay.?

2. Use the LM35DZ, To92. Pretty accurate. Us $1 per piece. Ebay. ?

Both can be sticked to the Ic/heatsink? and the wires can be outside the scope. ?

cslim

I have an HP 8660D which I like. It uses plug-ins and will generate signals up to 2.6 GHz with the right plug-ins (and the 11661B optional frequency extension option). I also have a couple of 8660Cs which I need to sell. These units are very heavy but work well. You can look at the specs for the C in a mid-80s HP catalog; the D showed up in the late 80s, IIRC.

DaveD

On 2/24/2013 7:22 AM, Jim wrote:

Two points .... first, you need to get a unit with Option 002* installed. This option gives operation from 512 MHz to 1024 MHz. Without it, the generator will INDICATE the higher frequencies, but will have zero output.

Second, the plastic gears inside the HP8640B are known to be fragile, and if they break, the repair is non-trivial. I understand there's a fellow who can provide brass gears, but I haven't looked into this yet, as neither of my HP8640Bs have failed. Yet.

Other than that, these generators are superb instruments.

73
Jim N6OTQ

* Major options are:
001 -- enhanced AM modulation
002 -- expanded frequency coverage
003 -- 25W reverse power input protection

--------------------------------------------------------------------------------
*From:* Rich Miller <av8torrich@...>
*To:* TekScopes@...
*Sent:* Sunday, February 24, 2013 7:58 AM
*Subject:* RE: [TekScopes] Which Tektronix Signal generator?

To get up to 1GHz, you cannot go wrong with a HP8640B for your
application. Of course, it's not on the light side, but does fit pretty
nicely on a modest work bench.
Rich
*From:*TekScopes@... [mailto:TekScopes@...] *On
Behalf Of *mirasad31415
*Sent:* Sunday, February 24, 2013 8:27 AM
*To:* TekScopes@...
*Subject:* [TekScopes] Which Tektronix Signal generator?
I am trying to narrow down my choice of a signal generator for my shack.

I would be glad to have your opinion on which Sig Gen to buy
I need something that covers from 0.01 MHz to 1000 MHz or preferably up
to 3000 MHz. If the sig gen goes up to 1000MHZ a second set to cover 1 to
3 Gig would have to be purchased later. At the moment I have several
oscillators to cover the 1 to 3 Gig range. Carrier noise better than
-80DBc at 10 kHz would be okay. Nothing too fancy but sweep capability,
AM and FM is needed.

I do not want to buy a very heavy post world war device although I admire
them and have a few RT sets from olden times. I have to have it courier
shipped to Pakistan and THAT costs.

Prefer Tek or HP, and something for which I can get the service manual
which is a must have.

I will be using it to play around with building transmitters and
receivers for my ham gear.

Azzythehillbilly

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

No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1430 / Virus Database: 2641/5628 - Release Date: 02/24/13

?

Two points .... first, you need to get a unit with Option 002* installed. ?This option gives operation from 512 MHz to 1024 MHz. ?Without it, the generator will INDICATE the higher frequencies, but will have zero output.

Second, the plastic gears inside the HP8640B are known to be fragile, and if they break, the repair is non-trivial. ?I understand there's a fellow who can provide brass gears, but I haven't looked into this yet, as neither of my HP8640Bs have failed. ?Yet.

Other than that, these generators are superb instruments.

73

Jim N6OTQ

* Major options are:

001 -- enhanced AM modulation

002 -- expanded frequency coverage

003 -- 25W reverse power input protection

---

From: Rich Miller
To: TekScopes@...
Sent: Sunday, February 24, 2013 7:58 AM
Subject: RE: [TekScopes] Which Tektronix Signal generator?

To get up to 1GHz, you cannot go wrong with a HP8640B for your application.? Of course, it's not on the light side, but does fit pretty nicely on a modest work bench.

?

Rich

?

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of mirasad31415
Sent: Sunday, February 24, 2013 8:27 AM
To: TekScopes@...
Subject: [TekScopes] Which Tektronix Signal generator?

?

?

I am trying to narrow down my choice of a signal generator for my shack.

I would be glad to have your opinion on which Sig Gen to buy
I need something that covers from 0.01 MHz to 1000 MHz or preferably up to 3000 MHz. If the sig gen goes up to 1000MHZ a second set to cover 1 to 3 Gig would have to be purchased later. At the moment I have several oscillators to cover the 1 to 3 Gig range. Carrier noise better than -80DBc at 10 kHz would be okay. Nothing too fancy but sweep capability, AM and FM is needed.

I do not want to buy a very heavy post world war device although I admire them and have a few RT sets from olden times. I have to have it courier shipped to Pakistan and THAT costs.

Prefer Tek or HP, and something for which I can get the service manual which is a must have.

I will be using it to play around with building transmitters and receivers for my ham gear.

Azzythehillbilly

I am trying to narrow down my choice of a signal generator for my shack.

I would be glad to have your opinion on which Sig Gen to buy
I need something that covers from 0.01 MHz to 1000 MHz or preferably up to 3000 MHz. If the sig gen goes up to 1000MHZ a second set to cover 1 to 3 Gig would have to be purchased later. At the moment I have several oscillators to cover the 1 to 3 Gig range. Carrier noise better than -80DBc at 10 kHz would be okay. Nothing too fancy but sweep capability, AM and FM is needed.

I do not want to buy a very heavy post world war device although I admire them and have a few RT sets from olden times. I have to have it courier shipped to Pakistan and THAT costs.

Prefer Tek or HP, and something for which I can get the service manual which is a must have.

I will be using it to play around with building transmitters and receivers for my ham gear.

Azzythehillbilly

Hi Steve,

Here is one possible solution:
<>

Basically a low-profile heat sink is needed that will not contact the cabinet bottom.

Patrick Wong AK6C

--- In TekScopes@..., Steve <steve65@> wrote:

I've seen reference to additional cooling for U800 in several postings.
Is there somewhere on the internet that suggests how to go about doing that?

On 01/14/2013 10:49 PM, Bob wrote:

Hello,
I know this is an old post but I'm having the same problem ,only the
power supply side of the blown fuse measures +58vdc. Is this higher
voltage due to bad caps blowing the 1/4 amp fuse or is this voltage
within a normal range for the unreg +32 volts?
Have a great day,
Bob

--- In TekScopes@... <mailto:TekScopes%40yahoogroups.com>,
"Bloy2004" wrote:

I have a 465M scope and after a while the display went dead.
Examining the internals revealed the 1/4A fuse was blown and
continues to blow after replacement. I have a manual, but nothing
is said about causes for this fuse blowing. Without the fuse in
place, I get +55VDC from the power supply Cap side (+32VDC
unregulated), and +.5VDC from the HV transformer side (pin 4 of part
T550). Where there should be +95VDC, I get only 11.4 VDC.
Questions:
1.What are the most likely causes for this fuse blowing, when all
was working fine.
2.What are the poosible causes for the +95Vdc to be way low.


Any responses welcome...

Sorry for the delay in answering this.
FWIW I've been involved with several 465Ms ( I own two ) and in every
case have had to
replace both CR582 and CR584 [ sheet 8 ].. 95 volt supply.
Ohmmeter checks don't mean much here as the leakage seems to happen at
higher voltages.
Aluminium caps have worked well for me.
The 'M"s are a decent piece of gear, the only other problem that I've
had was with the
intensity pot being noisy, tried cleaning but eventually just replaced it.