Date   

Tek Model 305 problem

wallace.gibbons
 

Greetings,
I have a 305 scope on the bench with a small problem. There's a small pulse
type waveform riding on top of any waveforms being displayed. It can be
seen with another scope by probing the vertical output amplifier outputs to
the CRT, and the vertical outputs from the main board.

If I disconnect the input to the vertical output amp board the trace is a
nice flat line. Good focus, very sharp line.

I assume from this that the errant signal is coupling into the vertical
channels on the main board. Probing the power supply outputs with another
scope has proved that only one supply was "noisy". I saw the pulse type
noise on the +150 volt power supply. I changed the two 10uf filter caps to
no avail. The +150 volts really isn't used in the signal chain but I
thought I'd eliminate it as a source.

The plus and minus 3 volt supplies look clean.

Has anyone seen this on a Model 305?

I know it's not a top of the line scope, not worth a whole lot, but it's a
friends and it's good enough for him to work on guitar amps and such.

Thanks,

Wally Gibbons
North Logan, Utah


Re: Focus on 475 scope

 

One issue I have seen on the 465 and 475 is the accumulation of black soot on many HV parts. I ran into exactly your problem more than once, and found that carefully cleaning all the soot with Q-tips and water or alcohol, and removing every bit of the (conductive) soot fixed my "insoluble" focus problem. it provides a sneak path for HV leakage, and disturbs the electron gun bias. the older the scope is, the more likely this problem becomes, you have to remove the aluminum HV protective cover to see it!

at the end of the day, keep in mind, this mesh style tube does not ever look really sharp in terms of focus.

this is really worth a try if nothing else seem to be wrong.
all the best,
walter
sphere research corp.


Re: Focus on 475 scope

donald collie
 

Looked at the photos - yes, that`s about as sharp as mine goes.
Cheers!...............................................................................................................................Don
C.

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On Mon, Jan 29, 2018 at 5:24 PM, Chuck Harris <cfharris@erols.com> wrote:

Usually, a pretty safe way is to force it to be out of focus
by turning the focus control fully one way, or the other.

-Chuck Harris

David Hess wrote:
My 7603 which spent considerable time in storage had its brightness
and sharpness improve after operating for days. if you do this, then
leave the beam intensity low but not off and for safety, only leave
the oscilloscope operating under supervision in case something goes
wrong.

On Fri, 26 Jan 2018 09:21:10 -0500, you wrote:

If your scope intensity double peaks, it could mean
that it is gassy, or it could mean that it has low
emission. Running the CRT will help get the gas
absorbed by the getter, so it may improve.

-Chuck Harris





Re: 7603 working .... then blank

Adrian
 

So there is a concurrent thread running on 7603 PSU failure (mine!!), which originated from the same symptoms:

All working, then a few seconds of 100Hz 'wiggling' then cold and dark, that thread might be worth a read?

PSU related so start there. Dead easy to check all the rails by removing the rear plastic cover (four screws) drop out the PSU LV Regulator PCB (four more screws) and all voltages both in and out, are easily accessible for probing on the assorted ribbon cables.

Take care 'unfolding' the board as the ribbons are stiff and in my case anyway, were snagged round stuff so it is easy to bend the SIL connector pins.  See  the SM schematic for details and yes, input voltages are on load, noticeably higher when things are not running!

Good luck,

Adrian

On 1/29/2018 10:09 AM, tinkera123 wrote:
Hi all,

Some background before questions:-

I picked up another 7603 Scope with 2 x 7A15A Vertical Plugins and a 7B53A Time Base ….. Beaverton B338,855 …. with Tek trolley, several basic probes, original Tektronix manuals and a few other bits and pieces …. very cheap as not many offered for sale in Australia that I know of.

So …. the common question is …. do I turn it on?? ……. or do a lot of testing first?? Usually, no …. all my old radios have been full of old electrolytics, wax, paper caps …. rat/mouse eaten …. used as a toilet etc.. But this Scope came to me as “Good operational condition” and I had photos of it working before I purchased and the guy was a retired telecommunications techo …

So yes, I gave it the once over …. power cord, correct voltage, Jumper in correct position, nice and clean, no burnt components, no burnt smells etc etc.. My intention was to turn it on …. side covers off … Safety goggles on … then check voltages at P1171 with Scope running.

I found the following issues:-

1. The display (no signal) was a bit fuzzy with some interference through it. This disappeared as the Scope warmed up.
2. The display completely disappeared for a second or two before re-appearing as normal. This decreased as the Scope warmed up.
3. Vertical Plug-in 2 Screen readout showed a “u” instead of a “V”. This slowly corrected to a “V”.

Calibrator functioned as I expected. All knobs functioned as expected. I was starting to relax …..

4. Then the Scope completely shut down ….. no Display (it transitioned from a normal looking square wave to squiggling lines to blank over 1 to 2 secs) …. Power light out …. Not sure about the Fan.

Waited for 10 mins and tried again …. The Fan operated, nothing else …. Same next morning. I will never know if these issues were already 'known' or occurred during transporting.
Currently, I am going through the circuit diagrams to work out what the possible causes could be …. making sure I can identify all the Boards, connectors, Tek terminology etc..

Questions:-
1. I would appreciate some expert opinions as to the probable cause(s)??
2. Am I correct I assuming that the voltages at P1171 are under operating conditions??

Cheers,
Ian


Re: 7603 working .... then blank

cmjones01
 

On Mon, Jan 29, 2018 at 02:09 am, tinkera123 wrote:
4. Then the Scope completely shut down ….. no Display (it transitioned from
a normal looking square wave to squiggling lines to blank over 1 to 2 secs)
…. Power light out …. Not sure about the Fan.
This is likely to be a failed tantalum bead capacitor, quite possibly in one of the plugins. To find it, take the plugins out one by one and try switching the scope on. If it comes out, you've found out which plugin has the problem. If it doesn't work even with all the plugins removed, the fault is in the mainframe.

To find the culprit in plugins, I just go round with my meter on continuity test range checking across all the likely-looking components. One failed short-circuit will typically make all the others on that power supply rail appear short-circuit too, so unless you have a ToneOhm or other means of isolating faults, desolder or cut one leg of any capacitor that appears shorted and check again. When I think I've found the problem, I try out the plugin with the offending capacitor removed. It may not meet its performance specs but it'll certainly tell you whether it's basically working or not.

Chris


Re: Help with CG5001AP/CG551AP calibration generators

 

Mod JB just adds GPIB to the 506

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of walter shawlee
Sent: 29 January 2018 01:05
To: TekScopes@groups.io
Subject: [TekScopes] Help with CG5001AP/CG551AP calibration generators

Tekwiki says that a TM506 modded JB is required to run it, but I have no idea what that mod does


7603 working .... then blank

tinkera123
 

Hi all,

Some background before questions:-

I picked up another 7603 Scope with 2 x 7A15A Vertical Plugins and a 7B53A Time Base ….. Beaverton B338,855 …. with Tek trolley, several basic probes, original Tektronix manuals and a few other bits and pieces …. very cheap as not many offered for sale in Australia that I know of.

So …. the common question is …. do I turn it on?? ……. or do a lot of testing first?? Usually, no …. all my old radios have been full of old electrolytics, wax, paper caps …. rat/mouse eaten …. used as a toilet etc.. But this Scope came to me as “Good operational condition” and I had photos of it working before I purchased and the guy was a retired telecommunications techo …

So yes, I gave it the once over …. power cord, correct voltage, Jumper in correct position, nice and clean, no burnt components, no burnt smells etc etc.. My intention was to turn it on …. side covers off … Safety goggles on … then check voltages at P1171 with Scope running.

I found the following issues:-

1. The display (no signal) was a bit fuzzy with some interference through it. This disappeared as the Scope warmed up.
2. The display completely disappeared for a second or two before re-appearing as normal. This decreased as the Scope warmed up.
3. Vertical Plug-in 2 Screen readout showed a “u” instead of a “V”. This slowly corrected to a “V”.

Calibrator functioned as I expected. All knobs functioned as expected. I was starting to relax …..

4. Then the Scope completely shut down ….. no Display (it transitioned from a normal looking square wave to squiggling lines to blank over 1 to 2 secs) …. Power light out …. Not sure about the Fan.

Waited for 10 mins and tried again …. The Fan operated, nothing else …. Same next morning. I will never know if these issues were already 'known' or occurred during transporting.
Currently, I am going through the circuit diagrams to work out what the possible causes could be …. making sure I can identify all the Boards, connectors, Tek terminology etc..

Questions:-
1. I would appreciate some expert opinions as to the probable cause(s)??
2. Am I correct I assuming that the voltages at P1171 are under operating conditions??

Cheers,
Ian


Re: 7603 PSU failure - got a screw loose?

satbeginner
 

Hi,

in my PS503 they used one of these sockets too for the 5V TO-3 regulator.
Here some pics: https://groups.io/g/TekScopes/album?id=21086

Leo


Re: NVRAM 2465 /2467 replacement

ADas
 

Hi John,
Yes I saw a few people had toyed with the idea of somehow getting a readout of the NVRAM, thats how i got my idea. Tek Scopes is an amazing community with a wealth of expertise.
The copy process turned out to be pretty simple really, mainly for three reasons, firstly the firmware eprom is socketed on the a5 board, so easy to take out. Secondly since the new nvram can be used to load the copy program into it, additional chips are not required. Thirdly the 27c011 eprom used for firmware is pin compatible with the DS1225, so the nvram can be placed in the eprom socket. I only had to learn the 6802 instructions, reset vector start address etc. The whole program to copy is only around 50 bytes. If any one else is interested i will post it.
cheers
ADAS


Re: Focus on 475 scope

Chuck Harris <cfharris@...>
 

Usually, a pretty safe way is to force it to be out of focus
by turning the focus control fully one way, or the other.

-Chuck Harris

David Hess wrote:

My 7603 which spent considerable time in storage had its brightness
and sharpness improve after operating for days. if you do this, then
leave the beam intensity low but not off and for safety, only leave
the oscilloscope operating under supervision in case something goes
wrong.

On Fri, 26 Jan 2018 09:21:10 -0500, you wrote:

If your scope intensity double peaks, it could mean
that it is gassy, or it could mean that it has low
emission. Running the CRT will help get the gas
absorbed by the getter, so it may improve.

-Chuck Harris



Re: Focus on 475 scope

 

It may be just a difference between the 475 and 475A oscilloscopes.
Someone else may know.

The power supply rejection of the vertical amplifier chain is not
infinite so excessive power supply noise might end up being displayed.
This could be caused by worn out or bad decoupling capacitors.

As a test to determine if the problem is with the circuits or the CRT,
I would short the vertical deflection pins together to see how this
affects the trace thickness. DO NOT short the vertical CRT pins to
ground or any other points as this will likely destroy the vertical
CRT amplifier; only short them together.

I had considerable trouble with Microsoft's sharing service. If I
thought someone could make something worse than Google Drive or Yahoo
Groups, then I was wrong.

On Wed, 24 Jan 2018 06:49:08 -0800, you wrote:

Hi everyone, i have 2. scope 475. I had recap both and now full working. But the line on the second one isn't sharper than first one. I check high voltage. 2.72kv for the first and 2.6k for the second one. So fucus and asting are working but i cant adjust the line more than that. Someone know what will be the problem ?

Thank you :)

Look picture here
https://1drv.ms/f/s!AnKLPDy3pII_gkwm-YPX7azSL7Y2


Re: Focus on 475 scope

 

My 7603 which spent considerable time in storage had its brightness
and sharpness improve after operating for days. if you do this, then
leave the beam intensity low but not off and for safety, only leave
the oscilloscope operating under supervision in case something goes
wrong.

On Fri, 26 Jan 2018 09:21:10 -0500, you wrote:

If your scope intensity double peaks, it could mean
that it is gassy, or it could mean that it has low
emission. Running the CRT will help get the gas
absorbed by the getter, so it may improve.

-Chuck Harris


Re: Focus on 475 scope

 

And the expansion mesh also creates a ghost from secondary emission
which follows and then proceeds the beam spot across the CRT. The
ghosting has the effect of reducing display contrast.

On Thu, 25 Jan 2018 11:22:06 -0800, you wrote:

The mesh itself also makes the beam fuzzier - even it is perfect on the way in. Like looking through a screen door. Ed


Re: Another 455 bad HV multiplier ?

 

If you can disconnect the input to the high voltage multiplier which
is pin 10 of the transformer and pin 11 of the high voltage module,
then the oscilloscope should at least display a trace without the
anode voltage indicating that it is otherwise functional.


Re: Video of 7612 ADC tube

 

I always found it fascinating that the 468 introduced in 1981 uses an
8-bit 20 MHz TRW flash ADC while the 2230 which replaced it in 1986
uses an integrated 8-bit 20 MHz Sony flash (1) ADC. The 2230 added a
sample and hold before the ADC to get the full 100 MHz bandwidth.

(1) Or subranging? I do not have a good datasheet for the Sony
CX20052A.

On Thu, 25 Jan 2018 20:28:55 -0800, you wrote:

Hi Michael,

That is a fascinating video. It was really clever how Tek managed to make such fast digitizers when semiconductors could not. I remember clearly when TRW introduced a state of the art 6 bit 20MHz flash digitizer that cost $120. That was the best you could buy in the mid 1970s.

Dennis Tillman W7PF


Re: Help with CG5001AP/CG551AP calibration generators

 

You will also need extender cable(s) to go to the mother board just behind the front panel for some of the boards.

If you take the side and top covers off of a TM5003 and disassemble the top panels on the CG551, you can reach a lot of the test points at the top of the boards.

On the one with the 95-98 errors, it might be one of the PIA chips on the CPU board, On the one with the 51, 56, 81, 83 errors, it may be an power supply (internal) issue. You will need to follow the flow charts. They are very good.

Regards,
Tom

----- Original Message -----
From: "walter shawlee" <walter2@sphere.bc.ca>
To: <TekScopes@groups.io>
Sent: Sunday, January 28, 2018 8:04 PM
Subject: [TekScopes] Help with CG5001AP/CG551AP calibration generators


I have three of these, two of the CG551AP style, and one CG5001AP. amazingly, I alos have some of the cables and heads. My problem is that one of each type simply wakes up with errors, and only one CG551AP works.

I have checked the batteries on them, all read 3.7V, and all three visible fuses are good.
The CG5001AP shows this on power up:
ERROR 95 TEST (hitting continue gives:)
ERROR97 TEST
ERROR98 TEST
ERROR96 TEST
it stalls at this point.

the CG551AP shows this on power up:
ERROR 51 TEST (hitting continue gives:)
ERROR 56 TEST
ERROR 81 TEST
ERROR 83 TEST
then goes to 1v/D x1 div and actually generates output

I have no idea how to even start on these, as I do not have a service manual, and have no idea what the codes stand for, plus I don't own THREE extenders to bring it out for service or adjustment. so, any insight is deeply appreciated. does anybody know HOW to even get them apart for service? I see no obvious way to do that, and it's three wide.

My third CG551AP unit works, so that is a bit cheery. the Tekwiki says that a TM506 modded JB is required to run it, but I have no idea what that mod does, and do not see it anywhere in the docs. I am currently running it in a TM5006, and it seems happy, but clarity is appreciated, as supposedly a mod is required there to run it as well, UB.

I am happy to divest the two nonworking units to a new home (where supposedly 3 extenders also live), but I would love to know the meaning of the error codes if possible, and find Volume 1 of the manual.

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.


Re: Help with CG5001AP/CG551AP calibration generators

Artekmedia <manuals@...>
 

Walter
Error notes below


I have checked the batteries on them, all read 3.7V, and all three visible fuses are good.
The CG5001AP shows this on power up:
ERROR 95 TEST (hitting continue gives:)
ERROR97 TEST
ERROR98 TEST
ERROR96 TEST
it stalls at this point.
Errors 95, 96, 97, and 98 are all TS1 and VS1 Data Register errors, failing anyone of these will not allow the unit to proceed further


the CG551AP shows this on power up:
ERROR 51 TEST (hitting continue gives:)
Low SAC 50 ohms error
ERROR 56 TEST
Current Mode Error -DC Current mode and chopper
ERROR 81 TEST
Low Edge Generator problem -DC/50 ohms

ERROR 83 TEST
positive Edge Generator -DC/50 ohms



I am happy to divest the two nonworking units to a new home (where supposedly 3 extenders also live), but I would love to know the meaning of the error codes if possible, and find Volume 1 of the manual.
As noted we have the manuals, but need to know serial numbers . Would love to have one of these but alas I do not have aTM5006 to house the unit, And shipping to the USA likely to be prohibitive

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.




--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com


Re: Help with CG5001AP/CG551AP calibration generators

Artekmedia <manuals@...>
 

Walter

We have the manuals for everything but the MOD JB

There are two different versions of the manuals, so I will need the serial numbers of your units in order to help you with the error codes
-DC
�manuals@artekmanuals.com

On 1/28/2018 8:04 PM, walter shawlee wrote:
I have three of these, two of the CG551AP style, and one CG5001AP. amazingly, I alos have some of the cables and heads. My problem is that one of each type simply wakes up with errors, and only one CG551AP works.

I have checked the batteries on them, all read 3.7V, and all three visible fuses are good.
The CG5001AP shows this on power up:
ERROR 95 TEST (hitting continue gives:)
ERROR97 TEST
ERROR98 TEST
ERROR96 TEST
it stalls at this point.

the CG551AP shows this on power up:
ERROR 51 TEST (hitting continue gives:)
ERROR 56 TEST
ERROR 81 TEST
ERROR 83 TEST
then goes to 1v/D x1 div and actually generates output

I have no idea how to even start on these, as I do not have a service manual, and have no idea what the codes stand for, plus I don't own THREE extenders to bring it out for service or adjustment. so, any insight is deeply appreciated. does anybody know HOW to even get them apart for service? I see no obvious way to do that, and it's three wide.

My third CG551AP unit works, so that is a bit cheery. the Tekwiki says that a TM506 modded JB is required to run it, but I have no idea what that mod does, and do not see it anywhere in the docs. I am currently running it in a TM5006, and it seems happy, but clarity is appreciated, as supposedly a mod is required there to run it as well, UB.

I am happy to divest the two nonworking units to a new home (where supposedly 3 extenders also live), but I would love to know the meaning of the error codes if possible, and find Volume 1 of the manual.

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.



--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com


Re: 7603 PSU failure - got a screw loose?

 

Motorola wrote a fabulous application note discussing flange mount
power devices:

https://www.onsemi.com/pub/Collateral/AN1040-D.PDF
https://groups.io/g/TekScopes/files/AN1040-D.PDF

And since there may have been changes in how the 7603 was constructed,
for instance mine came with the change notice fan which does not match
the fans in the other 76xx models, here is a photograph showing the
mounting details on mine:

https://groups.io/g/TekScopes/photo/21071/0?p=Name,,,100,1,0,0

I inspected mine for cracks in the solder joints but never found any.
I resoldered them anyway. I have never had mine apart far enough to
know but those look like they could be TO-3 sockets like Adrian says.
I thought they were spacers with the TO-3 pins soldered directly into
the printed circuit board but then the pins would have to be awfully
long.

The Motorola application note warns about using split ring lock
washers but it is probably acceptable in this case if you do *not*
compress the washer completely. Motorola recommends conical
compression or Belleville washers but I usually stack several wave
washers together because they are easier to acquire. My own
experience is that split ring lock washers tend to take a set and
become just broken washers over time. I am sure there are good ones
available made from the right material but how would you know?

If the compression washer is crushed flat, then expansion in one
direction increases the force a lot possibly crushing the printed
circuit board which I have witnessed before after a temperature cycle.

As far as the collector connection through the mounting screws, I have
occasionally seen a star lug under one of the screw heads or even a
wire soldered to the TO-3 case.

On Fri, 26 Jan 2018 10:25:08 -0800, you wrote:

I forget the details, but there is a chronic problem with the
connections on those six TO-3's on the back panel of scopes such as the
7603.

It seems like it was a thermal expansion issue of some kind where the
connections got fatigued and broke.

The world figured out how to fix this problem multiple ways but it has
been years since I fixed a few 7603's and old age has taken its toll.
If the new message archive search works, it should all be in the archive
under 7603, or maybe a Google search will turn up something from a
different source.

tom jobe...

On 1/26/2018 10:07 AM, Adrian wrote:

...

Quick as a flash I pull Q931 and remark "goodness me that was quite hot" (or words to that effect) so suspect all may not be well with the T03 output device and go to pull it having (just!) noticed it is actually in a socket.

Both screws that mount the device needed no discernible increase in torque to release them, so while not rattling they were definitely not tight either and are of course the collector connection. The transistor tested fine (diodes where they should be at least), replaced, torqued up and the thing has run fine with the 7D01 for some hours. Several of the screws on the other T03s were in a similar state.

I've only had the 'scope for a few months and there is no evidence of recent re-work inside so is this something that just happens over the years? If so some preventative tightening of screws may be in order.

Now back to figuring how to trigger this thing.........

Adrian


Help with CG5001AP/CG551AP calibration generators

 

I have three of these, two of the CG551AP style, and one CG5001AP. amazingly, I alos have some of the cables and heads. My problem is that one of each type simply wakes up with errors, and only one CG551AP works.

I have checked the batteries on them, all read 3.7V, and all three visible fuses are good.
The CG5001AP shows this on power up:
ERROR 95 TEST (hitting continue gives:)
ERROR97 TEST
ERROR98 TEST
ERROR96 TEST
it stalls at this point.

the CG551AP shows this on power up:
ERROR 51 TEST (hitting continue gives:)
ERROR 56 TEST
ERROR 81 TEST
ERROR 83 TEST
then goes to 1v/D x1 div and actually generates output

I have no idea how to even start on these, as I do not have a service manual, and have no idea what the codes stand for, plus I don't own THREE extenders to bring it out for service or adjustment. so, any insight is deeply appreciated. does anybody know HOW to even get them apart for service? I see no obvious way to do that, and it's three wide.

My third CG551AP unit works, so that is a bit cheery. the Tekwiki says that a TM506 modded JB is required to run it, but I have no idea what that mod does, and do not see it anywhere in the docs. I am currently running it in a TM5006, and it seems happy, but clarity is appreciated, as supposedly a mod is required there to run it as well, UB.

I am happy to divest the two nonworking units to a new home (where supposedly 3 extenders also live), but I would love to know the meaning of the error codes if possible, and find Volume 1 of the manual.

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.

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