Date   

Re: Fuse's or MOV's? 11A72 and 11A52 fuse question.

wkibler
 

This is the exact reason I enjoy repairing vintage Tea gear. There is much to learn that I am able to use in my career.


I recently (last year) used PTCs in a new design - another opportunity for
life long learning ;-)


Cheap manuals alert - eBay

Keith
 

Routine post here - alerting everyone that I see a seller on eBay offering lots of twelve OEM Tek manuals pretty cheap. The cost per manual works out to $3.32 per manual INCLUDING shipping. The seller has many lots posted...again 12 to a lot.

Here is a link to one typical lot. Check their store for the others. Not me, by the way.

https://www.ebay.com/itm/TEKTRONIX-Lot-of-12-Manuals-Lot-T4/202937299096?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D108fa6e7fc8b40c4b40600b4b1662525%26pid%3D100005%26rk%3D1%26rkt%3D12%26mehot%3Dpf%26sd%3D264538078644%26itm%3D202937299096%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv5PairwiseWeb%26brand%3DTektronix&;_trksid=p2047675.c100005.m1851

That’s all. Hope it helps someone.

Cheers,
CoolBlueGlow


Re: Troubleshooting and repairing a 7704A instrument

Albert Otten
 

Ernesto,

Not included is the 155-0078, the big hybrid at the output of the vertical amplifier. This one
may be still withheld as a trade secret?
? There is a lot of info about 155-0078-xx (M84) versions at Tekwiki and also a schematic.

What I find is that two transistors in the differential output drive, U4356
and U4366, get very hot, even after having squelched the 50 Mhz oscillation.
I question if this is normal? Time will tell.
The whole area around that output stage gets quite hot. After half an hour with the sweep free running at 1 ms/div I measured about 55-60 C with an IR thermometer and 60 C with a P6058 temperature probe right at the top of the Q4365 an Q4366. P6058 reading not corrected for measurement influence, so slightly >60 C in reality.

Albert


Re: Rail Probes?

K9FFK
 

Dan:

"TSP #76 - Keysight N7020A 2.0GHz Power Rail Probe Review, Teardown and Experiments"

<< https://www.youtube.com/watch?v=d_Ybe6xnMIg&;feature=youtu.be >>

Part of this presentation gets into the probe itself. Might be informative.

ymmv

Dick K9FFK

On 4/23/2020 2:03 PM, dnmeeks wrote:
Thanks, yeah I see the data sheet. I was hoping to know exactly how it's made. What's inside. The real scooby.


Re: Washing a 7K scope

josephlevy
 

Hi
Look at 'TekScope' magazine for July 1972
The 'research' done was partly in the US navy maintenance depo at Keyport Wa. (and I happened to be part of then....)

De Joe 4X1RV


Re: Washing a 7K scope

Bill
 

Never washed an oscilloscope but have have washed many PCBs used in our Bailey Net 90 Distributed Controls System in the Power Generation plants.  We shut down the cabinets and pulled the PCBs one at a time then washed them in Deionized water.  Dawn dish washing soap was the detergent we used with a soft brush to remove the grim.  After washing they were rinsed in more DI water then sprayed with aerosol Isopropyl alcohol.  The last thing done was blowing them off with aerosol air.   Did this many times over the years in the plants.  The PCBs were located in areas with lots of coal dust, chemical vapors, and flyash.  They were filthy but the cleaning process worked very well.  They were cleaned every 6 months.
Bill On Thursday, April 23, 2020, 9:44:36 PM CDT, Chuck Harris <cfharris@erols.com> wrote:

No high pressure washing!

What I would do is first blow the whole thing out
with 30 PSI compressed air.  So much of the grime will
just float away...

Then I would use a hand held squeeze pump sprayer with
a dish detergent (Dawn) and water mixture in it, about
the same concentration you would use to wash the dishes.
Set the nozzle to a shower sort of spray.  Douse areas
that are dirty, but lay off any enclosed switches or
transformers.

Then using a garden hose set for a mist, rinse while the
chassis is on an angle, so the water doesn't pool anywhere.

Prop it up on an angle, and blow it again with compressed
air, again, not towards closed switches...

A big cardboard box and an old milk shed heater makes a nice
convection oven.  Set the heater to low, and its thermostat
for something reasonable, and keep an eye on the temperature.

-Chuck Harris

Ed Breya via groups.io wrote:

I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?

Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.

If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.

I ran across this old scope washing article today,

http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.

Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?

Ed




Re: Washing a 7K scope

Jim Ford
 

And don't forget to unplug it from the mains first!  8>()Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Chuck Harris <cfharris@erols.com> Date: 4/23/20 7:44 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Washing a 7K scope No high pressure washing!What I would do is first blow the whole thing outwith 30 PSI compressed air.  So much of the grime willjust float away...Then I would use a hand held squeeze pump sprayer witha dish detergent (Dawn) and water mixture in it, aboutthe same concentration you would use to wash the dishes.Set the nozzle to a shower sort of spray.  Douse areasthat are dirty, but lay off any enclosed switches ortransformers.Then using a garden hose set for a mist, rinse while thechassis is on an angle, so the water doesn't pool anywhere.Prop it up on an angle, and blow it again with compressedair, again, not towards closed switches...A big cardboard box and an old milk shed heater makes a niceconvection oven.  Set the heater to low, and its thermostatfor something reasonable, and keep an eye on the temperature.-Chuck HarrisEd Breya via groups.io wrote:> I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?> > Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.> > If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.> > I ran across this old scope washing article today, > > http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf>; > which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.> > Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?> > Ed> > > >


Re: Washing a 7K scope

Chuck Harris
 

No high pressure washing!

What I would do is first blow the whole thing out
with 30 PSI compressed air. So much of the grime will
just float away...

Then I would use a hand held squeeze pump sprayer with
a dish detergent (Dawn) and water mixture in it, about
the same concentration you would use to wash the dishes.
Set the nozzle to a shower sort of spray. Douse areas
that are dirty, but lay off any enclosed switches or
transformers.

Then using a garden hose set for a mist, rinse while the
chassis is on an angle, so the water doesn't pool anywhere.

Prop it up on an angle, and blow it again with compressed
air, again, not towards closed switches...

A big cardboard box and an old milk shed heater makes a nice
convection oven. Set the heater to low, and its thermostat
for something reasonable, and keep an eye on the temperature.

-Chuck Harris

Ed Breya via groups.io wrote:

I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?

Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.

If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.

I ran across this old scope washing article today,

http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.

Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?

Ed




Washing a 7K scope

Ed Breya
 

I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?

Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.

If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.

I ran across this old scope washing article today,

http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.

Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?

Ed


Re: 577 curve tracer 177 test fixture current per division troubleshoot

Chuck Harris
 

If the porch switch isn't activated the yellow light
will come on... regardless of the collector voltage setting.

Also, the collector voltage will be disabled.

Most of the porch covers were lost in the first week of
operation, as we are all engineers, and know better than
to stick our fingers in there, and the covers get in the
way of real work.

So, jamb a piece of wood, or plastic in the hole where
the porch safety prong actuates the switch and the yellow
light will go off.

-Chuck Harris

DW wrote:

Interesting, perhaps what I am experiencing isn't actually a defect.




Re: 577 curve tracer 177 test fixture current per division troubleshoot

DW
 

Interesting, perhaps what I am experiencing isn't actually a defect.


Re: Rail Probes?

John Gord
 

In addition to good connection methods (very short grounds, etc.), a valuable technique for these measurements is to loop the probe cable a few times through a large ferrite core (split cores are easiest). This minimizes the added high frequency noise from ground currents between the DUT and measuring scope. I learned this from a designer of multi-kilowatt power converters.
--John Gord

On Thu, Apr 23, 2020 at 02:43 PM, Ed Breya wrote:


I had never heard of these, but from the data I'd say their usefulness is
mostly in the form of convenience. The exact same kind of measurements have
been done before, by many, for decades - I've done it. You measure the DC and
low frequency content with a regular scope input, and the high frequency
content with an AC-coupled 50 ohm wide BW input. These "power rail" probes
just combine the measurements into one channel, and add DC offsetting - look
at the 7A13 for an earlier example.

They are intended for low impedance sources, like power supply outputs, to
look at interference, ripple, and noise. There is a generalized term for all
of this, called PARD. If you want to see really high frequency content, you
use 50 ohm wide BW gear - a scope for time domain, or an SA for frequency. The
important thing is to isolate the DCV of the supply by AC-coupling, and most
importantly, to protect the equipment from surges that occur during
connect/disconnect, power up/down, and PS or load faults, etc.

In the block diagram, it may be shown simply as AC-coupling, but in the
details you would find that the HF signal path is all RF, 50 ohm environment,
including the RF coupling cap, with sufficient voltage rating.(not just any
old cap), and various protection circuitry on the 50 ohm output side going to
the equipment.

So, if you can live with the inconvenience of using a regular scope input or a
7A13 for DC and LF, and having to rig up a fairly simple AC-coupling and
protection circuit (the fanciness and complexity depend mostly on the required
BW) for HF, you can save the 4 grand or so.

Also note that the key to HF performance and CMRR is to carry the signals
directly in coax, with minimal impedance connections. You can get some ideas
looking at the optional accessories and how they attach to the DUT - that's
the part that really makes it work.

Ed




Re: 577 curve tracer 177 test fixture current per division troubleshoot

teamlarryohio
 

I just fired mine up on 25V with the front porch unplugged. No yellow
light.
-ls-


Re: Troubleshooting and repairing a 7704A instrument

 

I am pleased of having "discovered" the data sheets of most of the integrated circuits of the 7000s in tekwiki. Most of you have probably benefited from these data sheets already.

These are the schematics and some logic diagrams of the parts 155-0009, 155-0010, 155-0012, 155-0013, 155-0022, 155-0067. Not included is the 155-0078, the big hybrid at the output of the vertical amplifier. This one may be still withheld as a trade secret? I also see that these integrated circuits are still available, something reassuring if one ever needs one. Fortunately, the ones on my 7K seem to work well.

The advantage of these data sheets is that one can at last understand the logic of the circuit diagrams in the mainframe and plugins, for example the vertical channel in the 7A26, without having to guess from the "circuit description".

On another issue, I have found a solution for the 50 Mhz parasitic oscillation in the horizontal amplifier of my 7704A. The solution is to keep connected a X10 probe to one of the outputs stages, a 15 pF capacitance?,ha ha.
I don't have an electronic lab at home, but I do everything in my office. And I had to start populating it with components since I started to play again with electronics a few month ago. Now I have to wait for an order of small pF caps! In the meantime, the probe is connected there, and I don't mind it, having enough probes. I could even find space in the 7704 display unit to leave it there permanently... (I'm kidding)
I had dismounted the horizontal amplifier to change its two decoupling capacitors of the +- 15V to little ceramics. In doing so I discovered that one of these had a broken lead, so the scope had worked without it for undefined time. When I did the exchange and tried again, the problem of oscillations persisted, confirming my idea that these caps are there mainly for "good practice".

What I find is that two transistors in the differential output drive, U4356 and U4366, get very hot, even after having squelched the 50 Mhz oscillation. I question if this is normal? Time will tell.

Ernesto


Re: Rail Probes?

Jim Ford
 

PARD being an acronym for Periodic And Random Disturbance, for those who haven't seen the term before. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: "Ed Breya via groups.io" <edbreya=yahoo.com@groups.io> Date: 4/23/20 2:43 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Rail Probes? I had never heard of these, but from the data I'd say their usefulness is mostly in the form of convenience. The exact same kind of measurements have been done before, by many, for decades - I've done it. You measure the DC and low frequency content with a regular scope input, and the high frequency content with an AC-coupled 50 ohm wide BW input. These "power rail" probes just combine the measurements into one channel, and add DC offsetting - look at the 7A13 for an earlier example.They are intended for low impedance sources, like power supply outputs, to look at interference, ripple, and noise. There is a generalized term for all of this, called PARD. If you want to see really high frequency content, you use 50 ohm wide BW gear - a scope for time domain, or an SA for frequency. The important thing is to isolate the DCV of the supply by AC-coupling, and most importantly, to protect the equipment from surges that occur during connect/disconnect, power up/down, and PS or load faults, etc. In the block diagram, it may be shown simply as AC-coupling, but in the details you would find that the HF signal path is all RF, 50 ohm environment, including the RF coupling cap, with sufficient voltage rating.(not just any old cap), and various protection circuitry on the 50 ohm output side going to the equipment.So, if you can live with the inconvenience of using a regular scope input or a 7A13 for DC and LF, and having to rig up a fairly simple AC-coupling and protection circuit (the fanciness and complexity depend mostly on the required BW) for HF, you can save the 4 grand or so.Also note that the key to HF performance and CMRR is to carry the signals directly in coax, with minimal impedance connections. You can get some ideas looking at the optional accessories and how they attach to the DUT - that's the part that really makes it work.Ed


Re: 577 curve tracer 177 test fixture current per division troubleshoot

DW
 

I started to look at taking the switch out of the 177 fixture of the donor and so far this is appearing the be a nightmare of a task.

It looks like everything is built on top of other things, in order to get to the switch most of the fixture has to be completely disassembled. I wonder if anyone else has undertaken the task of working on a 177 test fixture?

On the manual it states to just simply remove the knob which is easy enough, and then the hex bolts which one side is not so hard to get at but other is way back in there. Finally desolder the leads from the switch however the front plate of the fixture is in the way for some of the leads.

I notice there is a plate over top of the fixture, it would be nice if I could just remove the front plate and remove the nuts for the switch. Wish I could just take out a few screws and out the board comes and then I can enjoy the working current division ranges along with my sanity


Re: Rail Probes?

Ed Breya
 

I had never heard of these, but from the data I'd say their usefulness is mostly in the form of convenience. The exact same kind of measurements have been done before, by many, for decades - I've done it. You measure the DC and low frequency content with a regular scope input, and the high frequency content with an AC-coupled 50 ohm wide BW input. These "power rail" probes just combine the measurements into one channel, and add DC offsetting - look at the 7A13 for an earlier example.

They are intended for low impedance sources, like power supply outputs, to look at interference, ripple, and noise. There is a generalized term for all of this, called PARD. If you want to see really high frequency content, you use 50 ohm wide BW gear - a scope for time domain, or an SA for frequency. The important thing is to isolate the DCV of the supply by AC-coupling, and most importantly, to protect the equipment from surges that occur during connect/disconnect, power up/down, and PS or load faults, etc.

In the block diagram, it may be shown simply as AC-coupling, but in the details you would find that the HF signal path is all RF, 50 ohm environment, including the RF coupling cap, with sufficient voltage rating.(not just any old cap), and various protection circuitry on the 50 ohm output side going to the equipment.

So, if you can live with the inconvenience of using a regular scope input or a 7A13 for DC and LF, and having to rig up a fairly simple AC-coupling and protection circuit (the fanciness and complexity depend mostly on the required BW) for HF, you can save the 4 grand or so.

Also note that the key to HF performance and CMRR is to carry the signals directly in coax, with minimal impedance connections. You can get some ideas looking at the optional accessories and how they attach to the DUT - that's the part that really makes it work.

Ed


Re: Vacuum forming 7K interface "covers"

Eric
 

I could be wrong but I believe the part number is shared across the entire 7K line. Handling with care is needed as depending on the age of the scope could be 50 + years of thermally cycled plastic.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of David C. Partridge
Sent: Thursday, April 23, 2020 4:11 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Vacuum forming 7K interface "covers"

Yes, same part on 7603 etc. 'scopes.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Michael W. Lynch via groups.io
Sent: 23 April 2020 19:42
To: TekScopes@groups.io
Subject: Re: [TekScopes] Vacuum forming 7K interface "covers"

If I had one of these as a sample, I would gladly attempt to design and 3D print one of suitable quality.

Would this be a part that would be found in the 76xx series Scopes? If so, is this easy to access without totally destroying the scope? I have two of these scopes, so I might obtain a sample from one of these scopes.

Looking at the document that Håkan posted, they do not appear that complex. I would need to see the actual part to determine if it was possible to produce a 3D print of the item.

Sincerely,

--
Michael Lynch
Dardanelle, Arkansas


Re: 577 curve tracer 177 test fixture current per division troubleshoot

Eric
 

I can run the measurement I have an (as far as I know) good 577 though my 177 is in need of a looking cap before I can use it.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of DW
Sent: Thursday, April 23, 2020 3:12 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 577 curve tracer 177 test fixture current per division troubleshoot

I would say to have someone independently run a test on their 577 is still desired, though if they are willing and at their own convenience.

I am in the process where I am thinking about transplanting the current per division switch from a donor 177 but their serial numbers are different

The donor 177 is B052747
The 177 that will get the replacement part is B020417

I have looked at both switches and they appear to look the same with the same connections and similar resistors with similar placements. Looking at the table above the values are only slightly different. I would then conclude that replacement should be fine.


Re: Vacuum forming 7K interface "covers"

 

Yes, same part on 7603 etc. 'scopes.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Michael W. Lynch via groups.io
Sent: 23 April 2020 19:42
To: TekScopes@groups.io
Subject: Re: [TekScopes] Vacuum forming 7K interface "covers"

If I had one of these as a sample, I would gladly attempt to design and 3D print one of suitable quality.

Would this be a part that would be found in the 76xx series Scopes? If so, is this easy to access without totally destroying the scope? I have two of these scopes, so I might obtain a sample from one of these scopes.

Looking at the document that Håkan posted, they do not appear that complex. I would need to see the actual part to determine if it was possible to produce a 3D print of the item.

Sincerely,

--
Michael Lynch
Dardanelle, Arkansas

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