Date   

Re: Introduction of myself!

 

Were the memory boards changed as part of an upgrade to older models?
I don't know the answer to your question, i.e. I don't know if an upgrade was available from Tek.

For a full upgrade the rear panel (with the fan opening and keyboard socket) would have to be replaced as well, since the two backup power banana sockets would go and a switch installed to allow selecting either running on backup power (Li battery) or restarting with system test after power up. The difference is obvious between the original version and the new version rear panel.

I do know that it's quite easy to modify the computer main board to accomodate the new integrated ROM/RAM board: Only one power supply wire need be connected to an unused connector main board pin. The old boards will work in the new model but not vice versa without installing the (power) wire.

One of my 7854's is a late version separate ROM/RAM version with new GPIB software ("1.03") in non-Mostek ROMs. Apart from the apparently improved GPIB handling, replacing the deteriorating Mostek ROMs could be an advantage. So, the OP could be lucky on two levels: Old Mostek separate ROM/RAM, old non-Mostek separate ROM/RAM, new integrated Li-backup ROM/RAM board.

Raymond


Re: 7904 - Very Dim Trace

David DiGiacomo
 

On Mon, Feb 15, 2016 at 10:31 PM, David <@DWH> wrote:
agree that your proposed steps are the way to go. The z-axis DC
restorer is the most likely suspect so replace or rebuild the z-axis
board
Except the DC restorer is in the high voltage module, not on the Z-axis board...


2465B / 2467B Calibration

Michael
 

I am planning on upgrading the firmware of my 2465B CT (pre B05xxxx serial
number). before it gets calibrated. This is to pick up any software bug fixes
(usually, the main reason for firmware upgrades), possible algorithm
improvements and feature additions or improvements. That leads to two
questions.


First, I have the .bin files for the -10 firmware (160-5370-10 and
160-5371-10). However, I have been unable to find the -11 firmware (which
unlike the other firmware versions actually adds a minor feature or two). Does
anyone here have the -11 firmware .bin files? Or are they in one of the file
upload groups. I can't read the archives or the file uploads. If someone does
have the -11 firmware or it is in the file uploads, I would appreciate if it
would be emailed to me.


Second, in reading the service manual for gotchas related to a firmware
upgrade and calibration, I found that on page 5-16 of the service manual,
for the horizontal timing adjustment in table 5-3 it states

"Steps 32, 33, and 34 are for 2465B instruments with serial numbers B012946
and above, and 2467B instruments with serial numbers B010537 and above."

The Army's calibration procedure has the same constraints.

I went through the service manual with a fine tooth comb and found that
neither B012946 nor B010537 are related to any change or difference whatsoever.
For the 2465B, serial number B012946 is right in the middle of the -04 ROM
range. For the 2467B, serial number B010537 is right in the middle of the -05
ROM range.

That would argue that, at the very least, the -04 ROM contains whatever is
necessary for steps 32, 33 and 34. But it also argues that it is not ROM
related. But, there must be SOME difference, or it would just be an update to
the calibration procedure. It also argues that even if I upgrade the firmware
to -11, those steps still should not be performed. The only thing that I can
think of is a version change in one of the boards common to the 2465B and
2467B that does not affect the parts list and does not involve any other
changes. However, such an update is not documented anywhere in the service
manual.

Does anyone know exactly why those steps shouldn't be performed on earlier
serial numbers (mine, for example, is B010xxx and so precedes B012946)? Would
it actually be harmful to perform them?

Additionally, does anyone know of a reason - other than the need for
recalibration - NOT to upgrade the firmware from -04 to -11? And, if
that would cause a problem, what about to -10 or -7?


Mike


Re: Introduction of myself!

 

Were the memory boards changed as part of an upgrade to older models?
I thought the updated boards were only included in later 7854s.

On 15 Feb 2016 17:28:48 -0800, you wrote:

Will do as soon as it (the 7854) arrives in approx 10 days. I hope it's had the ROM upgrade!


Re: 7904 - Very Dim Trace

 

That almost happened to my Ebay acquired 7904. It was not packed well
and UPS dropped it on the front pushing the plug-ins further into the
mainframe and damaging the calibrator controls. I actually bought it
for the 7CT1N which was included but the 7904 has really grown on me.

On Mon, 15 Feb 2016 20:34:22 +0300, you wrote:

I have just discovered massive mechanical damage to the main interface board in
one of my eBay special 7904s, so there is a possibility of you need parts.

Nathan KK4REY


Re: 7904 - Very Dim Trace

 

I agree that your proposed steps are the way to go. The z-axis DC
restorer is the most likely suspect so replace or rebuild the z-axis
board and if that does not fix the problem, proceed with riskier steps
like high voltage measurements. I would rather rebuild the existing
board because a replacement board from a parts donor will be old but
in the worst case, you can rebuild both and have a spare to keep or
sell; there is merit in both approaches.

As I posted earlier, I suspect a replacement high voltage multiplier
can come from a 7704A, 7844, 7854, 7904, or 7904A parts donor; it will
be easy enough to check the part numbers in the service manuals. The
7704A and 7904 were very common and sold for many years, 14 and 10
years respectively, so I doubt finding a parts donor will be
difficult. My intention when I bought two questionable 2230s was that
I could combine them for one working oscilloscope but then I fixed
both so be warned that this hobby can get out of hand.

I linked an example of a high voltage multiplier replacement which can
be built although I would make a change. The 7704 high voltage
multiplier has 50 megohms of resistance in series with its output made
up of several (high voltage?) resistors in series and I would add that
if the original 7904 multiplier had it. Maybe someone knows or this
can be determined through inspection of a bad multiplier.

The floating measurement can be tricky. The 7904 schematic shows 1.1
megohms between the z-axis DC restorer and grid so a direct
measurement with a standard 10 megohm input multimeter at the CRT will
add considerable error although this can be calculated out. Measuring
across R1684 will return a better result. Make sure the test leads
are solidly connected before powering the oscilloscope. I would
solder little test points in for a reliable connection; you do not
want a test lead popping off.

I agree about not risking your Fluke multimeter; I feel the same way
about my Tektronix DMM916. If you get that far, it may be worth
picking up a less expensive meter.

When you power on the 7904 for tests after working on the z-axis
circuits, make it a habit to deliberately defocus the beam first to
prevent damage to the CRT phosphor in the event that the beam current
is excessive. Adjusting the position controls so that the beam is off
of the screen initially is also a good idea.

On 15 Feb 2016 09:29:35 -0800, you wrote:

David,

Once again, thanks for your experiments and report. For now, thanks to the PDA transfusion findings you reported, the HV multiplier is off the key suspect list. As you noted, it could well have been a long-standing issue, and the previous cal lab just tweaked the scope deflection to work with the reduced PDA voltage. If I get the scope back to where it was, I'll look into the 14 kV issue more. And I'll certainly be on the look out for a parts donor, though I expect they're getting scarce...

I ordered a Z-axis board, and expect it'll show up in a day or two. Seems easy to swap that in and see if it makes any difference as a next step. If I feel brave and lucky, I might try a floating Fluke measurement...

Jim


Re: Bringing up to snuff a Tek 465M

Bert Haskins
 

On 2/15/2016 10:32 PM, Doxemf doxemf@... [TekScopes] wrote:

Hank, Tom, the 465M has a clamshel cover and the motherboard is
fastened directly to the bottom half.
Bill,
KB3DKS

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

Thank you, Tom!

Hank, unfortunately no front cover, but even so, I don't see how the
plastic cabinet would slide off easily!
Slide!.. you rotate the four plastic buttons to release and then lift
the cover off.
I wipe a tiny bit of Dove into the button thread before putting the
cover back on.





Re: 7904 - Very Dim Trace

Jim McIntyre
 

I have just discovered massive mechanical damage to the main interface board in
one of my eBay special 7904s, so there is a possibility of you need parts.
Nathan KK4REY


Thanks Nathan – I’d be interested in the entire power supply assy, or just the HV multiplier…






>Well, the HV needs to be fixed, so might as well do that and see where things stand.


Right Peter. – as soon as I stumble onto the parts, I’ll do it…




I had little time to tinker tonight, but did try swapping in a new 10 ohm heater resistor. No difference…


The Z-axis board I bought off eBay should be here in a day or two - I'll report back after the switch-a-roo.


Re: 7904 - Very Dim Trace

Jim McIntyre
 

I have just discovered massive mechanical damage to the main interface board in
one of my eBay special 7904s, so there is a possibility of you need parts.
Nathan KK4REY


Thanks Nathan – I’d be interested in the entire power supply assy, or just the HV multiplier…






>Well, the HV needs to be fixed, so might as well do that and see where things stand.


Right Peter. – as soon as I stumble onto the parts, I’ll do it…




I had little time to tinker tonight, but did try swapping in a new 10 ohm heater resistor. No difference… The replacement z-axis board will be here in a day or two. I'll report back here with results after the switch-a-roo...


Re: Bringing up to snuff a Tek 465M

Bill (Doc) Courtright
 

Hank, Tom, the 465M has a clamshel cover and the motherboard is fastened directly to the bottom half.
Bill,
KB3DKS

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

Thank you, Tom!

Hank, unfortunately no front cover, but even so, I don't see how the plastic cabinet would slide off easily!


Re: Bringing up to snuff a Tek 465M

eliya gwetta
 

Thank you, Tom!

Hank, unfortunately no front cover, but even so, I don't see how the plastic cabinet would slide off easily!


Re: Introduction of myself!

Brian Bloom
 

Will do as soon as it (the 7854) arrives in approx 10 days. I hope it's had the ROM upgrade!

Thanks in advance!

it appears to have some sort of CRT related issue - possibly unblanking circuitry.
>>
>Please, tell us more about your CRT related issue - in a separate thread.

>Raymond


Re: Introduction of myself!

 

it appears to have some sort of CRT related issue - possibly unblanking circuitry.
Please, tell us more about your CRT related issue - in a separate thread.

Raymond


Re: Tek 465 intensity problem

Tad
 

The 0777 CRT will run just fine in a 465...I've done it many times.
You'll have a nice scope when you're finished.

Tad


Re: Introduction of myself!

Brian Bloom
 

I feel much better about the purchase, now.. Thanks! I did get it for pretty cheap and it appears to have some sort of CRT related issue - possibly unblanking circuitry. If I take the seller for his word, the unit worked perfectly up until the point where he let it sit for "a couple" of years. It does still appear to be fairly clean ( not clean enough to have been detailed for sale, though!) so I'm not too awful worried. I do fortunately have quite a large stockpile of Tek specific parts on hand in case the need arises.

Relax, a 7854 with a sampling setup like a 7T11A and a 7S11 is a joy to use, if only because it's so easy to >average out jitter in many cases. Keep that 7854, even without sampling plugins!
>Please note that you need a 7T11A (*not* 7T11) with the 7854. Modification from a 7T11 to a 7T11A is not too >involved and described by forum member Dave Partridge.

>See <http://www.perdrix.co.uk/7T11Conversion/ http://www.perdrix.co.uk/7T11Conversion/>

I actually found that website last night off of duckduckgo and sent Dave an email to confirm he still had kits - which he does. Nice to see that I'm at least somewhat heading in the right direction for once..


Re: Bringing up to snuff a Tek 465M

 

Yes. Push in to see the trigger view. It is a momentary switch.

----- Original Message -----
From: eliyag@... [TekScopes]
To: TekScopes@...
Sent: Monday, February 15, 2016 3:47 PM
Subject: [TekScopes] Re: Bringing up to snuff a Tek 465M



My apologies for sending the same message twice. I didn't think it went the first time.

Tom, here's a video of the screen as I turn the intensity. The probe is inserted into the calibration "port":
https://youtu.be/0qielKd25RE https://youtu.be/0qielKd25RE

Ed, is hydrogen peroxide safe to use on plastic? Is it safe to use on the front panel of the 465M or will it ruin the lettering?

One more question: Under "vert mode" there's the button for "20Mhz bw" and "trig view". How many position does this switch have? On mine, it seems like two position. One is when I pull it out to cut the bandwidth. Then I can push it back and I assume that this restores the full bandwidth. Then I can push it further in but it won't latch. In other words, it's more like a momentary switch at that position. Is this normal?

Thanks again!


Re: PG502 power lamp off

dnmeeks
 

IF Q650 was floating around, with signs that it should have been screwed
down, it likely would overheat and fail. But usually when a bipolar fails it
shorts. Usually.

Since they are using 1 ohm as the over-current sense, looking at the uA723
data sheet, that give about 0.6A at current limit. If the normal current is
200mA or so, that would cause about 6.5V * 0.2A = 1.3 watts of power
dissipation. That's not horrible, but if not attached it will get very hot,
maybe hot enough to fail.

All moot of course, if you already know it's failed.

I would drop in any generic NPN with the same footprint (is that thing a
TO220?) and suitable V and I ratings. Like 30V or better, 5A or better,
something like that. If it's in a TO220 there are plenty to pick from.

And yes, if the tab hole is ground, you need the full insulation treatment
on that guy.

Can you tell if there was thermal grease on it at one time?



And the 15V supply is based on the 5V supply, so it's probably intended to
adjust that "SET +15V" trimmer even though you're really adjusting the 5V
rail. Where 5V goes, the 15V rail will follow.



Good luck, keep us updated.



Dan


Re: 7904 - Very Dim Trace

 

I think we had a discussion here about an older Tektronix oscilloscope
(465?) where failure of the high voltage multiplier *only* affected
the brightness and to a lessor extent the focus; the deflection hardly
changed.

On Mon, 15 Feb 2016 22:40:05 +0100, you wrote:

Hi all,

so maybe I was wrong in my statements made earlier. The deflection
factor observed on dual accel CRTs does vary with the HV, you can see
this when some arcing in the HV multiplier occurs.

BUT: I never went this far with a Tek made CRT, but with CRTs from Valvo
and Philips (later PDC) and Elrog as used in Hameg Scopes. Also Colour
TVs have this kind of larger picture if the HV is less than usual.
Maybe this is where I got mislead....

Regards, Jochen DH6FAZ


Re: Introduction of myself!

 

On 15 Feb 2016 13:47:41 -0800, you wrote:

On another note, I just smacked myself for buying a 7584 when I need
sampling plugins - not another scope!!.
Relax, a 7854 with a sampling setup like a 7T11A and a 7S11 is a joy to use, if only because it's so easy to average out jitter in many cases. Keep that 7854, even without sampling plugins!

Please note that you need a 7T11A (*not* 7T11) with the 7854. Modification from a 7T11 to a 7T11A is not too involved and described by forum member Dave Partridge.

See <http://www.perdrix.co.uk/7T11Conversion/>

Raymond
Tektronix also released a modification for the 7T11 so it could work
in the 7854 although I have not compared it to Dave's solution. Hakanh
was kind enough to make it available:

http://www.hakanh.com/dl/kits.htm
http://www.hakanh.com/dl/docs/hardtofind/7T11_mod7854.pdf

I find the 7T11A to be more useful in a variable persistence storage
oscilloscope like the 7834 however it depends on your application and
I agree that the 7854 and 7T11A are a very powerful combination.


Re: Introduction of myself!

 

On another note, I just smacked myself for buying a 7584 when I need
sampling plugins - not another scope!!.
Relax, a 7854 with a sampling setup like a 7T11A and a 7S11 is a joy to use, if only because it's so easy to average out jitter in many cases. Keep that 7854, even without sampling plugins!

Please note that you need a 7T11A (*not* 7T11) with the 7854. Modification from a 7T11 to a 7T11A is not too involved and described by forum member Dave Partridge.

See <http://www.perdrix.co.uk/7T11Conversion/>

Raymond