Date   

Re: 2465b possibly really stupid question (noob)

James Theonas
 

https://groups.io/g/TekScopes/album?id=12814. does not seem to open anything useful please check link.

On Monday, May 11, 2020, 6:39:17 PM GMT+3, Siggi <siggi@undo.com> wrote:

On Mon, May 11, 2020 at 10:55 AM James Theonas via groups.io <jamestheonas=
yahoo.com@groups.io> wrote:

  Got it in respect with the capacitor! any value related to that cap?
schematic is unclear about the value or type.
Thanks!

I don't know that I've ever seen a spec for AC coupling capacitor in these
scopes. You can perhaps look at the schematics for older scopes that had
more discrete input attenuators.
It needs to have a pretty high voltage rating, as it'll see whatever
voltages you couple to your scope input. You can also see what it looks
like in the second photo of this album:
https://groups.io/g/TekScopes/album?id=12814.


Re: 2465b possibly really stupid question (noob)

Siggi
 

On Mon, May 11, 2020 at 10:55 AM James Theonas via groups.io <jamestheonas=
yahoo.com@groups.io> wrote:

Got it in respect with the capacitor! any value related to that cap?
schematic is unclear about the value or type.
Thanks!

I don't know that I've ever seen a spec for AC coupling capacitor in these
scopes. You can perhaps look at the schematics for older scopes that had
more discrete input attenuators.
It needs to have a pretty high voltage rating, as it'll see whatever
voltages you couple to your scope input. You can also see what it looks
like in the second photo of this album:
https://groups.io/g/TekScopes/album?id=12814.


Re: 7854 Bad display board

Harvey White
 

Don't know if they did this for this processor, but often if a firmware test fails, there will be some sort of output somewhere identifying the test.  I don't absolutely mean the complicated ones, but some of the most basic tests.  It might just be that the processor loops on a particular address with a fail.  I've seen that, and equipment of this vintage had a lot of "startup" and "check the processor" tests that could behave like that.  IIRC, the DM5010 has a bunch.  Whether or not you can find the data and extract anything useful from it depends much on the depth of the manual.

If you have a signature analyzer, some of the same equipment (vintage wise) makes extensive use of that function.  It generally places the processor in a no-op loop and you get to see what all the addressing does.

Harvey

On 5/11/2020 10:47 AM, Paul wrote:
Hey Dan -

Last night I replaced all the ROMs & EPROMs with the patched -02 version and pulled the FPLA and I'm still getting all the lights. No change if I pull the jumper. My next course of action this evening:
1) check all the supply voltages
2) Check some of the test points on the top of the ROM & MPU with a LA to see if I can tell how far along it's getting.

If I pull one of the 4 ROMs (now EPROMs), I'll just get a single, dim 'A' illuminated, so it's at least getting somewhere before failing. When I get all lights on, there's no describable delay.
I've also got a card edge connector en route for P130 on the MPU so I can get eyes on all the address & data lines.

thanks -
Paul



Re: 2465b possibly really stupid question (noob)

James Theonas
 

Got it in respect with the capacitor! any value related to that cap? schematic is unclear about the value or type.
Thanks!

On Monday, May 11, 2020, 4:52:49 PM GMT+3, Siggi <siggi@undo.com> wrote:

On Mon, May 11, 2020 at 9:14 AM James Theonas via groups.io <jamestheonas=
yahoo.com@groups.io> wrote:

I as looking at schematic 4 which has the inputs and I don't see (noob?)
the part that makes the distinction between ac coupling and dc coupling...

It's the first relay on A11/A12 that either shorts across or puts the input
coupling cap in-line with the signal. See the capacitor that's the first
thing after the input? That's your AC coupling cap, and the first relay is
shown in the DC coupling position on the diagram.

As an aside, the 1M resistor that follows it is the "precharge" resistor
for the AC coupling cap. If you're coupling a potentially high voltage
signal to your scope, it's good practice to put it in GND coupling while
you hook it up (turn it on or whatever), then switch over to AC coupling.
This will pre-charge the coupling cap to ground through the 1M resistor and
the 50Ohm termination resistor.

I mention this because this is the reason that the first two relays in the
attenuator are both in line with the AC coupling cap - the 50Ohm coupling
relay doubles as a pre-charge switch for the cap. If either of those relays
have a bad or no connection, you effectively couple that 1M pre-charge
resistor in-line with your signal, after the AC coupling capacitor.


Re: 7854 Bad display board

Paul
 

Hey Dan -

Last night I replaced all the ROMs & EPROMs with the patched -02 version and pulled the FPLA and I'm still getting all the lights. No change if I pull the jumper. My next course of action this evening:
1) check all the supply voltages
2) Check some of the test points on the top of the ROM & MPU with a LA to see if I can tell how far along it's getting.

If I pull one of the 4 ROMs (now EPROMs), I'll just get a single, dim 'A' illuminated, so it's at least getting somewhere before failing. When I get all lights on, there's no describable delay.
I've also got a card edge connector en route for P130 on the MPU so I can get eyes on all the address & data lines.

thanks -
Paul


Re: 2465b possibly really stupid question (noob)

Colin Herbert
 

I would agree about not using any abrasive material on contact surfaces for the most part. However, it is worth pointing out that Brasso _is_ an abrasive material. If you have a tin of Brasso that has stood undisturbed for a while, there is a clear(ish) liquid and a solid precipitate. The solid precipitate is a fine powder rather similar to "jeweller's rouge" and is a mild abrasive, much like many other metal polishes and various preparations to take scratches out of car finishes. Try taking a little Brasso on a clean cloth and rubbing a darkish painted surface with it. You will notice after a while that some of the paint has come off onto the rag, but you may not notice that much difference to the painted surface (other than removal of scratches).
Colin,

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of M Yachad
Sent: 11 May 2020 07:36
To: TekScopes@groups.io
Subject: Re: [TekScopes] 2465b possibly really stupid question (noob)

Cleaning those switches (and all types of copper or other contacts), is done perfectly with Brasso.

NEVER use any abrasive material on any contact surfaces on any equipment.


Re: 2465b possibly really stupid question (noob)

Siggi
 

On Mon, May 11, 2020 at 9:14 AM James Theonas via groups.io <jamestheonas=
yahoo.com@groups.io> wrote:

I as looking at schematic 4 which has the inputs and I don't see (noob?)
the part that makes the distinction between ac coupling and dc coupling...

It's the first relay on A11/A12 that either shorts across or puts the input
coupling cap in-line with the signal. See the capacitor that's the first
thing after the input? That's your AC coupling cap, and the first relay is
shown in the DC coupling position on the diagram.

As an aside, the 1M resistor that follows it is the "precharge" resistor
for the AC coupling cap. If you're coupling a potentially high voltage
signal to your scope, it's good practice to put it in GND coupling while
you hook it up (turn it on or whatever), then switch over to AC coupling.
This will pre-charge the coupling cap to ground through the 1M resistor and
the 50Ohm termination resistor.

I mention this because this is the reason that the first two relays in the
attenuator are both in line with the AC coupling cap - the 50Ohm coupling
relay doubles as a pre-charge switch for the cap. If either of those relays
have a bad or no connection, you effectively couple that 1M pre-charge
resistor in-line with your signal, after the AC coupling capacitor.


Re: 2465b possibly really stupid question (noob)

Tom Gardner
 

On 11/05/20 14:28, momemeca wrote:
I will get back to you with board locations tomorrow.

On 10 May 2020, at 20:36, vk1gvc@iinet.net.au wrote:

Dimitris, I'm a newcomer here having only joined two weeks ago but your message has inspired me to post my first msg.

I bought a 2465 at auction some years ago and it's been in storage for a long time now although it was working OK, apart from one problem, when last I had it running. Having renovated my radio shack recently to get more space (for a CRO) on the workbench I powered up the 2465 and all seem to go well - normal trace, text on screen where it should be, all OK I thought. I left it to warm up for a few minutes but then I heard an audible PFFT and saw some magic smoke escape from the RHS panel at the rear so I switched it off immediately and took it outside the house. I did notice, in the few seconds before I got to the power switch, that the trace and text on screen were unaffected leading me to think/hope that the fault is not too serious. I haven't had time to open it up yet to locate the offending component/s but I did some internet research on 2465 repairs and found a lot of advice on re-capping which I'm sure will be very valuable.

Returning to the unresolved problem I first notice years ago when I bought the 2465, as I best recall it was an intermittent on one of the Y input channels which resulted in an obvious distortion to the waveform: a test square wave 'went droopy' consistent with an input capacitor failure or maybe a dry joint. I'd like to turn it on right now and see how my unit's Y input problem compares with the one you report on your 2465B but that will have to wait until I can diagnose and repair, and that might be a long time with parts shipping taking so long these days.

But meanwhile I will be very interested to read any advice about your problem as it may well help me later too.

Regards,

Graham Carter
Canberra, Australia



Re: 2465b possibly really stupid question (noob)

momemeca
 

G'day Graham,
A fellow Aussie here, replying to your post.
A quick message to let you know that I can help with your 2465 picking up that bad habit :-)
Given your explanation, it is most likely that one of the dreaded RIFA X1/X2 safety capacitors blew it's cool!
It's a fairly straightforward fix albeit a fiddly one. There are four or five of those beasties and, even if only one is found to be faulty, I would strongly suggest that you replace ALL of them as they are way past their operational lives.
I will get back to you with board locations tomorrow.
I am based near Melbourne.

Cheers,
Rick

On 10 May 2020, at 20:36, vk1gvc@iinet.net.au wrote:

Dimitris, I'm a newcomer here having only joined two weeks ago but your message has inspired me to post my first msg.

I bought a 2465 at auction some years ago and it's been in storage for a long time now although it was working OK, apart from one problem, when last I had it running. Having renovated my radio shack recently to get more space (for a CRO) on the workbench I powered up the 2465 and all seem to go well - normal trace, text on screen where it should be, all OK I thought. I left it to warm up for a few minutes but then I heard an audible PFFT and saw some magic smoke escape from the RHS panel at the rear so I switched it off immediately and took it outside the house. I did notice, in the few seconds before I got to the power switch, that the trace and text on screen were unaffected leading me to think/hope that the fault is not too serious. I haven't had time to open it up yet to locate the offending component/s but I did some internet research on 2465 repairs and found a lot of advice on re-capping which I'm sure will be very valuable.

Returning to the unresolved problem I first notice years ago when I bought the 2465, as I best recall it was an intermittent on one of the Y input channels which resulted in an obvious distortion to the waveform: a test square wave 'went droopy' consistent with an input capacitor failure or maybe a dry joint. I'd like to turn it on right now and see how my unit's Y input problem compares with the one you report on your 2465B but that will have to wait until I can diagnose and repair, and that might be a long time with parts shipping taking so long these days.

But meanwhile I will be very interested to read any advice about your problem as it may well help me later too.

Regards,

Graham Carter
Canberra, Australia



Re: 2465b possibly really stupid question (noob)

James Theonas
 

https://scontent.fskg1-2.fna.fbcdn.net/v/t1.0-9/97187201_10219673347937322_395171359560302592_o.jpg?_nc_cat=100&;_nc_sid=8024bb&_nc_eui2=AeFcV3iGeHAhlLW-i8_1fpTH-QaHFKCSjs_5BocUoJKOz6liUk6sEdjHyw8Y2lW9H3s&_nc_ohc=unOHMM_kRmIAX_xAfDu&_nc_ht=scontent.fskg1-2.fna&oh=718d54f0d014edc3f18ef80b81a57fd2&oe=5EE07E72

https://scontent.fskg1-1.fna.fbcdn.net/v/t1.0-9/97047356_10219673348977348_5408303968235290624_o.jpg?_nc_cat=111&;_nc_sid=8024bb&_nc_eui2=AeHEL1n3nOxq8JP8MzLSO7NsL69c5TkCrwgvr1zlOQKvCOhZV6laJdWXN6dhc9sOjoI&_nc_ohc=RWClrmXDO40AX8rNyRb&_nc_ht=scontent.fskg1-1.fna&oh=5a6a45d522effcbe5af4dffae2c89faf&oe=5EDE2E7E


Re: 2465b possibly really stupid question (noob)

James Theonas
 

I as looking at schematic 4 which has the inputs and I don't see (noob?) the part that makes the distinction between ac coupling and dc coupling... I see the signal go from the relays and the dividers (10) and also the 50 or 1M ohm input but after it goes to the u100 chip pin A. Also noticed the TL074 going to pin 18 and pin 2. Don't know if they have anything to do with the ac coupling. I have worked the coupling switch up and down incase it would have an effect even if temporarily but no change. Note that except the curving of the top and bottom left edge of the square wave, the measured voltage seems to be correct...

Thanks again for your help...


Re: 2465b possibly really stupid question (noob)

Richard Knoppow
 

Brasso IS quite abrasive, has Kaolin and crystalline silica in it.

See: <https://mbyc.net/MSDS/Brasso-Polish-MSDS.pdf>;

   There are a number of contact cleaners n the market, such as Caig Deoxit which are non abrassive and are quite effective.

On 5/10/2020 11:36 PM, M Yachad wrote:
Cleaning those switches (and all types of copper or other contacts), is done perfectly with Brasso.

NEVER use any abrasive material on any contact surfaces on any equipment.
--
Richard Knoppow
dickburk@ix.netcom.com
WB6KBL


Re: 2465b possibly really stupid question (noob)

James Theonas
 

Thanks guys! I will check it out!

On Monday, May 11, 2020, 9:36:31 AM GMT+3, M Yachad <yachadm@gmail.com> wrote:

Cleaning those switches (and all types of copper or other contacts), is done perfectly with Brasso.

NEVER use any abrasive material on any contact surfaces on any equipment.


Re: 2465b possibly really stupid question (noob)

 

Cleaning those switches (and all types of copper or other contacts), is done perfectly with Brasso.

NEVER use any abrasive material on any contact surfaces on any equipment.


Re: 7854 Bad display board

Dan G
 

At this point, it would be good to narrow down just where the CPU
is getting stuck. The fact that you have all lights on means that the
CPU has started self-tests, but it never finishes.

So, let's see if you are now at least passing the RAM and ROM
self-tests: remove jumper P1306 (labeled IRTC in the upper right
corner of the MPU board), and power up the scope. If the CPU
has successfully passed the ROM self-test, then it will start the
RTC test next, and by removing P1306, we will force it to fail.

If you now get CHOP and B to light up after a few seconds,
then the RTC self-test has failed as expected, and it at least
confirms that your ROM checksum tests are passing, and that
the CPU can make it through the entire RTC self-test code
sequence.

Don't forget to replace the P1306 jumper after this.


dan


Re: TEK 5054 CPU Fan

Allen <allen@...>
 

You can change the file extension from .dd to .img on a Windows 10 machine and then mount it as a virtual drive or burn it to CD. Probably works on Windows 7 or 8, too. You can also mount a .dd file with Virtual Clone Drive (free).


Re: Tektronix 465M - only scale illumination

n4buq
 

Essentially, Chuck's post explained a bit about why the lack of HV was causing Q552 in mine to overheat. If your F558 is okay, then that may not be the problem in yours.

As for running it with the A5 board removed, I don't know. I'd have to study that quite a bit more.

If you have the AIR FORCE TO 33A1-13-496-1 (NAVELEX 0969-LP-170-0010) manual, while it's not a very extensive explanation of it, page 4-29, paragraph f discusses the +95 volt supply. Essentially it's a high frequency oscillator (approximately 40kHz) that provides the input voltage for T550. If all the rest of your voltages are good, then that's where I think I'd start looking; however, as I mentioned, that might require another oscilloscope to properly troubleshoot it but other folks here might have some suggestions as to how to do that without that.

BTW, I misquoted the voltage at C558 and your reading of 51.6V there agrees with the schematic so that's a good sign.

BTW, I don't claim to be an expert on this (or any other) oscilloscope. Reading that this is an issue with +95 reminded me that I'd been down that trail with mine so I chimed in. I wish I could be more help.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "paronaram" <baloyan@hotmail.com>
To: TekScopes@groups.io
Sent: Sunday, May 10, 2020 9:50:25 PM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

I can't find that post, let me ask you.
My all other voltages are OK, like I mentioned in my previous post I have
-5V, +5V, +32V and even +51.6V on C558
only missing voltage is +95V

All fuses are OK as well

What creates this +95V? In the circuit where we testing transistors, I see
+32V input via fuse, and I get 51.6V by the C588 cap

Can I power on this scope without A5 Vertical board?

Thank you




Re: Tektronix 465M - only scale illumination

paronaram
 

I can't find that post, let me ask you.
My all other voltages are OK, like I mentioned in my previous post I have -5V, +5V, +32V and even +51.6V on C558
only missing voltage is +95V

All fuses are OK as well

What creates this +95V? In the circuit where we testing transistors, I see +32V input via fuse, and I get 51.6V by the C588 cap

Can I power on this scope without A5 Vertical board?

Thank you


Re: Knob needed for TDS420A

Sam Reaves
 

Hi Stephen,

Thank you so much for responding

There are 3 knobs on the TDS420A that are the larger size (~=19mm) for Vertical Scale, Horizontal Time Base and the General Purpose knob. There are 3 smaller knobs (~=10mm) for Vertical Position, Horizontal Position and Trigger Level.

i noticed that the two knobs on the TDS540 for Vertical scale and Horizontal Scale are probably the size for the one I need but for some reason the Tek part number is different. Maybe it's just a color difference.

Please PM me so we can work this out.

Best regards,

Sam
W3OHM


Re: 7854 Bad display board

Paul
 

/facepalm/ I read 'ALT' as 'All.'
Okie, so back to the ROM board, it would seem!

I might just delete this post.
thanks Dan!

9661 - 9680 of 176487