Date   

Re: TM500 Plug-in Extention

Stephen
 

Yes Colin,

I removed all the connections from the BNC at the back to all the backplane connectors.
Now everything is fine. Even the DC505A that was not counting anything while on the extender, is now working fine inside the mainframe. I should wire EVERYTHING, every pin on the extender. Even those not dedicated to the power supply of the plugins. I thought I could just get away with wring the first 13 pins, but no. Some plugins (DC5xx) in particular need the others too.
So apparently I had 2 issues, the rest of the pins, AND option 12... Now all is good.
Except my DC503 stopped counting altogether. But I’m posting on the appropriate thread about this.


Thinning the herd

Paul Amaranth
 

I have a number of scopes in various condition that I'd like
to get rid of. I don't want to ship these, so pickup only or
I can meet you part way if it's not too far. Everything is
located a bit out of Ann Arbor, Michigan.

4) 465 for parts or restoration $140 for all 4 - 3 of them
look pretty complete, one's missing some knobs. Condition
unknown. I got these on a pallet from a service company
with the idea of refurbishing them, but I'm not going to
get to that. I'm trying to trim the project queue to
something I could reasonable get through in 20 years.

2) 468 - one sort of works, looks like it needs filter caps,
and may have other issues. The other is a parts scope,
missing knobs, pieces, etc $40 for both.

2.5) 422 One works fine, I refurbished it a couple years ago,
One needs repair, one is a parts chassis without
power supply or cabinet. The 2 complete scopes have
the AC supply. $50 for the lot.

1) 5223 10MHz with digital storage, includes 5A18, 5A48
and 5B10N plugins. Condition - unknown.
$35

1) 5440 60MHz with 2) 5A48 and 1) 5B31 plugins
$35 Condition - unknown.

Buy a bunch and get a quantity discount :-) Offers considered.

Eventually I'll have a list of 5000 plugins; they're packed in
a box somewhere at the moment.

Send me a note OFF-LIST and I can send pics.

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: Tektronix 475

Simon
 

That is interesting as I had a feeling that the zener might be bad, but I haven’t checked it yet. On the to-do list.
Many thanks
Simon


Re: 475 With a bowed display. . . .Ideas?

Tom Gardner
 

On 13/08/20 15:17, Michael W. Lynch via groups.io wrote:
On Mon, Aug 10, 2020 at 11:58 AM, Tom Gardner wrote:

I went and picked up a CRT, and the bloke let me have a decent deal on a 485
that took a long time to startup first thing in the morning. Locating the
dubious startup electrolytic fixed the problem, but lead to the problem of
buying more duff scopes :(
Tom,

Laughing here at reading this. Almost exactly how I got into the same predicament here. Some people say you smoke crack one time and you are hooked and people like us fix one scope and we are hooked, we cannot stop buying old blue boxes with a whole bunch of little knobs and switches on the front.
I taught my daughter the concept of how you become a drunkard, i.e. one drink at a time.

I once asked people why I needed a fourth scope. There was only one justifiable answer: you must have four before you can have five :(


Re: 475 With a bowed display. . . .Ideas?

Michael W. Lynch
 

On Mon, Aug 10, 2020 at 03:01 PM, Chuck Harris wrote:


RATS!!!

-Chuck Harris
Chuck,

Yes, it SUCKS! When I heard that glass tinkle, my heart sank. If this was an old beater, it would not be so bad, but this is a very nice scope. I suppose that a good parts scope will turn up sooner or later. At least I am ready if that happens.

Appreciate all the advice that you provide.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Re: Tektronix 475

Chuck Harris <cfharris@...>
 

Ok, you are almost there.

There are two things at play at the same time with the intensity
grid function. The first is the DC restorer, which you have checked.
It translates the voltage output from the intensity control to a
voltage range at the control grid of the CRT.

The second thing is the grid bias control. It biases the grid so that
it is in the operating range of the CRT.

I forget, have you verified that the grid bias control has an effect?

Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.

-Chuck Harris





tenareze32@gmail.com wrote:

I tested all the transistors in the Z-axis amplifier and all were OK. The amplifier puts out a square wave which varies from 0 to 35 V with the intensity control, but the beam was still too bright at all intensity settings. I started to suspect the voltage multiplier circuit (C1372, CR1377, CR1379) as the input was at least 40 V p-p. The components tested OK with a multimeter, but I replaced the diodes in case they were breaking down at circuit voltages. No change, but all controls operate as described in the manual with the scope probe on the cold side of C1372. The circuit diagram in my copy of the manual does not correspond exactly to the circuit description as it shows a separate winding on the HT transformer for grid bias, which I cannot locate (transformer on other side of the board). However, a 40-50kHz signal is coming through the 390 kΩ resistor (R1326) from somewhere. I will just live with a bright trace for the moment and concentrate on the Y output amplifier, which looks as thought it can be removed and tested on the bench.
Simon




Re: TM500 Plug-in Extention

Colin Herbert
 

I have got around to operating my PS 503A on a known-good TM504 Mainframe and it works fine. I also checked it on a known-good TM503 mainframe using my Dan Meeks extender; again fine. I was looking at the manual for the PS 503A and it makes your head spin. The 5 VDC supply is referred to ground, which is the white banana-socket next to the red 5 VDC socket. The two 0-20 VDC supplies are not referenced to ground, but to a common return, which is the black banana-socket on the front. These two supplies are floating from ground, but are related so that the can be added together using the green and red banana-sockets on the front panel and ignoring the black "common" socket. Checking for a voltage from the green or the red 0-20 VDC sockets to ground will show no voltage unless one of these sockets is deliberately connected to chassis ground. When I was looking at the PS 503A manual last night, I think I noticed that there were several chassis grounds - I suppose this is to ensure that the supplies are floating from true chassis ground, but it did make my head spin.

I think that you may be considering the Power-Supply TM500 plug-ins to be "normal" when this isn't really the case because of the floating supplies.

If the "Option" added to the mainframe was causing your problems, then it is a good idea to remove any wire interconnections. My TM 504 has option 1, which adds a 50-pin connector and 4 BNC sockets to the rear. None of these are wired to anything else, but originally, wiring kits were available to make connections. This option was designed for the ease of "building a system", as it is mentioned in the manual, with interconnecting modules and external items. If you have no need of such interconnections, then remove them. Some may be soldered on, but as originally imagined, the connections would have been square-pin push-on connectors so that soldering and un-soldering and any subsequent possible damage was minimised. Perhaps you could tell us what the "Option" included and what, if any, connections had been made.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 13 August 2020 08:17
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

On Wed, Aug 12, 2020 at 02:32 PM, teamlarryohio wrote:


...and the Common for the variable supplies is tied to 21A, 21B, 34A, and 34B
if the schematic is accurate.
You probably mean 24A/A

Hint: The 5V ground is tied to the chassis of the PS503A. See if that is useful.
Yes, this is exactly what I have.

However, on my extender, none of these are connected. Only every pin, but 6B, from 1 to 13 are.
And, according to another post, that seems to make this unit behave “normally”...
That doesn’t make any sense...
None of this makes any sense. How can things work as intended when on the extender, but not when directly inside the mainframe? This is mind boggling....


Re: Tektronix 2230

tekscopegroup@...
 

Not to get in the way of this, but you could also just check the individual voltage drop between the Drain and Source leads to their origin and find out if the connector is actually causing any drop. If it where me, and there is no evidence of problems with that connector I would keep it until at least the scope if back to normal operation, just in case.


Re: 475 With a bowed display. . . .Ideas?

Michael W. Lynch
 

On Mon, Aug 10, 2020 at 11:58 AM, Tom Gardner wrote:


I went and picked up a CRT, and the bloke let me have a decent deal on a 485
that took a long time to startup first thing in the morning. Locating the
dubious startup electrolytic fixed the problem, but lead to the problem of
buying more duff scopes :(
Tom,

Laughing here at reading this. Almost exactly how I got into the same predicament here. Some people say you smoke crack one time and you are hooked and people like us fix one scope and we are hooked, we cannot stop buying old blue boxes with a whole bunch of little knobs and switches on the front.
--
Michael Lynch
Dardanelle, AR


Re: DC503 Not Working

Stephen
 

After some long posts spanning over 2 threads, trying to figure out why the DC503, then the DC505A did not display anything else than just a randomly placed single “0” at any one time while plugged inside the mainframe, I finally founded out, without understanding why, that Option 12 messed everything up (see topic here, on the extender:

https://groups.io/g/TekScopes/topic/tm500_plug_in_extention/76102597?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,76102597

Also, the DC505A that was working when plugged into the extender did display all the digits, but was not counting at all, is now working perfectly inside the mainframe, after I disconnected option 12.
It turns out that even if no pins are need to power the modules, you have to connect them all in order for some plugins to properly work. I found that out the long way.

I’m sorry if it took 2 threads to finally figure this out.


Re: 475 With a bowed display. . . .Ideas?

Michael W. Lynch
 

On Mon, Aug 10, 2020 at 12:01 PM, <toby@telegraphics.com.au> wrote:


Aaarg, sorry, ignore my message about Sphere. It's sold.

There is one on ebay UK though:
https://www.ebay.ca/itm/154-0677-10-TEKTRONIX-CRT/264704023173

--Toby
Toby,

Yes, I found that one. Too rich for my blood. I will just lurk around until I find a parts scope. One of these will turn up sooner or later.

--
Michael Lynch
Dardanelle, AR


Re: Tektronix 2230

Saroj Pradhan
 

Hi satbeginner
Not yet
I will do it tomorrow and check if that improves the situation.
Thanks
Saroj

On Thu, Aug 13, 2020, 3:02 PM satbeginner <castellcorunas@gmail.com> wrote:

Hi Saroj,

With respect to the voltage drop after a while, did you already removed
the Molex connector from the FET?

Over the years, the FET, so also the Molex, worked at temperatures around
70 Celsius, so maybe the spring loaded contacts of the Molex are not so
spring loaded anymore.... ;-)

At 1.8A about one ohm is enough to drop 2V.

Curious as always,

Leo




Re: Tektronix 475

Simon
 

I tested all the transistors in the Z-axis amplifier and all were OK. The amplifier puts out a square wave which varies from 0 to 35 V with the intensity control, but the beam was still too bright at all intensity settings. I started to suspect the voltage multiplier circuit (C1372, CR1377, CR1379) as the input was at least 40 V p-p. The components tested OK with a multimeter, but I replaced the diodes in case they were breaking down at circuit voltages. No change, but all controls operate as described in the manual with the scope probe on the cold side of C1372. The circuit diagram in my copy of the manual does not correspond exactly to the circuit description as it shows a separate winding on the HT transformer for grid bias, which I cannot locate (transformer on other side of the board). However, a 40-50kHz signal is coming through the 390 kΩ resistor (R1326) from somewhere. I will just live with a bright trace for the moment and concentrate on the Y output amplifier, which looks as thought it can be removed and tested on the bench.
Simon


Just spotted this 7854 switchable ROM (normal/diagnostic) on eBay

 

https://www.ebay.co.uk/itm/254685390375

Is this produced by one our members?

David


Re: Looking for a better in circuit ESR meter

Precaud
 

I have been successfully using an HP 4815A for in-circuit ESR testing for more than 20 years.


Re: 2465 Project, story so far.

 

OK so here is the good news update, a massive thank you to Andy Warner who sent me a new pair of ROMS, both Roms had gone, but so had U2092, I managed to get a MC68B02 for only a few UK£'s to test, and it brought it back to life (shame about the SC67127P MIL Spec Processor) but it is alive again. With the limited test kit I have calibration seems quite good, the only oddity is that channel 1 voltage measurement is about 3mv out when I check an accurate 10V reference, ( Channel 2 using the same probe and settings is spot on) Frequency on both channels is as good as I will need. I will post a working photo, and again thank you Andy.


Re: Tektronix 2230

satbeginner
 

Hi Saroj,

With respect to the voltage drop after a while, did you already removed the Molex connector from the FET?

Over the years, the FET, so also the Molex, worked at temperatures around 70 Celsius, so maybe the spring loaded contacts of the Molex are not so spring loaded anymore.... ;-)

At 1.8A about one ohm is enough to drop 2V.

Curious as always,

Leo


Re: TM500 Plug-in Extention

Stephen
 

Ok.. Since the only difference between the extender and the connector inside the mainframe is “Option 12” connected to pins 27A’s and 28A’s, I removed all the 6 coax from the back of the connectors to the 6 BNC’s at the back of the unit.

Everything behaves as expected... Baffling to me...

Now I can turn my attention to the DC505A which is counting gibberish if at all, and to the DC503 that, all of a sudden, just stopped counting altogether. Then I’ll turn my attention to the SC502 that came with the TM506.

Thinking out loud: I guess this is what you have to go through when you buy a lot of things at the same time....
A lot of troubleshooting!!
A big thank you to ALL of you for bearing with me.


Re: TM500 Plug-in Extention

Stephen
 

Worth noting though, this mainframe has Option 12 installed. But there is nothing connected to the BNC’s at the back. And all 6 of them have their leads go respectively and independently to each one of the 6 ports 28A and ground to 27A.
But there’s nothing there, and they’re not shorted.


Re: TM500 Plug-in Extention

Stephen
 

On Wed, Aug 12, 2020 at 02:32 PM, teamlarryohio wrote:


...and the Common for the variable supplies is tied to 21A, 21B, 34A, and 34B
if the schematic is accurate.
You probably mean 24A/A

Hint: The 5V ground is tied to the chassis of the PS503A. See if that is useful.
Yes, this is exactly what I have.

However, on my extender, none of these are connected. Only every pin, but 6B, from 1 to 13 are.
And, according to another post, that seems to make this unit behave “normally”...
That doesn’t make any sense...
None of this makes any sense. How can things work as intended when on the extender, but not when directly inside the mainframe? This is mind boggling....

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