Date   

Re: clean up grey foam residue

demianm_1
 

The foam is I believe polyurethane and I found this product https://www.sherwin-williams.com/homeowners/products/touch-n-foam-professional-polyurethane-foam-cleaner that seems to be specific to the task. There are probably others as well. There are videos of using it to clean off the gunk from guns.

Big question for me (any I'm sure others) is what to replace the foam with. The original stuff doesn't hold up real well. The "pick and pluck" stuff is really disappointing. Is there something better suited to making an insert with some life expectancy?


Re: Power Supply Issue in a 7934 ?

Jean-Paul
 

Liam, intuition points to a failing and dead tantalum cap on on of the LV power bus.

The néon on the HV section are trying to start up, but lack power on other circuits causes the flickering.

Just a theory

Jon


Re: A1 board removal? WAS Re: 'splitting' A2 and A3 PCBs when recapping Tek 2465

Dennis Fernandez
 

where is the link? I need to change an attenuator.

Dennis N4KPI


Re: clean up grey foam residue

greenboxmaven
 

Choke and carburetor cleaner from an auto supply does a good but messy job of removing the foam and it's residue. It turns it into "buggers" that can be scraped off with a plastic knife or scraper. Use a rag sprayed with the cleaner to get the final bit
remaining. Do this outdoors, the cleaner is flammable. Wear gloves and old clothing, the residue stains anything it touches.

    Bruce Gentry, KA2IVY







Bit the bullet today and scraped all the 'rotting' grey foam insert stuffout of the A6303 probe box. That stuff is really horrible.

So what's the best cleaning agent to wipe out the residue? Some of what's

left are small patches where it was glued in place but overall the case and
lid need to be thoroughly cleaned inside before I make up replacement foam
inserts.
DaveB, NZ





Re: Challenging 2465 PS repair

satbeginner
 

Hi all,

finally I found time to work on the LVPS repair...
I added a picture showing the two types of primary inverter I have in the album : https://groups.io/g/TekScopes/album?id=263466

The top one is the Inverter I'm working on, the bottom one I pulled from one of my working 2465's.
The bottom one has the extra little circuit to control the Siemens Fan, and also has the J303 that the top one doesn't have. (where the confusion about where to connect the 5V Load resistors came from)

The bad news: The bottom one I pulled from a perfectly working scope even has a slightly bigger ripple (~20V-pp) on the primary test-load than the PS I'm working on. (12V-pp)

The good news: I think I found the problem in the flowchart where it says the ripple should be appr. 1V-pp.......

If I measure across the 3uF capacitor shown in the test-load, the ripple I get is slightly less than 1V-pp , so I think it should be measured there, and NOT across the actual test-load, although the text says differently

So my intermediate conclusion is now: My repaired primary switcher is OK now, so on to the regulator board.

To be continued,

Leo


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

Sorry about the confusion Federico. I meant this for the values under consideration. 0x2A3 is near the midpoint of the range 0x22B-0x2FC and 3.27 V near the midpoint of 2.716-3.742 . So there is no doubt to which of the 5 possible ranges these values belong. If according Table 6.4 they do not correspond to the front panel time/div setting (and show a wrong time/div readout) the fault has to be sought now in the analog circuits.
Albert


clean up grey foam residue

Dave Brown
 

Bit the bullet today and scraped all the 'rotting' grey foam insert stuff
out of the A6303 probe box. That stuff is really horrible.
So what's the best cleaning agent to wipe out the residue? Some of what's
left are small patches where it was glued in place but overall the case and
lid need to be thoroughly cleaned inside before I make up replacement foam
inserts.
DaveB, NZ


Re: Wondering if there is probe ID rings out there in the Either.

 

Eric,

The P6108 does not have a readout pin ("ID ring"). The other two should, but the shrouds appear to be easily shattered and lost.

While the P6120/21/22 are supposedly "miniature modular" probes they use a completely different kind of ground lead, which is nearly impossible to find. You may be able to make your own with a female pin socket and some shrink wrap tubing, however. The witches hats should be the same as for other miniature modular probes, but I have had mixed luck with both original Tek witches hats, as well as new Chinese made ones on the P612x probes.

The modern Chinese made clip-on ground leads work perfectly well with other miniature modular probes (like the P6075), so you can just order a set from eBay or Amazon.

-- Jeff Dutky


Re: Wondering if there is probe ID rings out there in the Either.

Eric
 

I have 3 TEK P6108 Probes that needs id rings and A Tek P6075 that needs a ring and a ground lead. I also Have a Tek 6121 that needs a ground lead and a witches hat.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Brian Cockburn
Sent: Friday, June 25, 2021 1:50 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Wondering if there is probe ID rings out there in the Either.

Eric, maybe the brand and model number of the probes would help us to help you.


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Hi Albert.
I've just been told that it should actually be 1023, not really relevant to the conversion though.

The values shown here are even nicely bear >the midpoint of the ranges.
Honestly I'm a bit confused, those EXT voltages are not in between the ARES2 limits, are they? Are we looking to the same table?


Re: Type CA module in a 545

David Kuhn
 

No, no, no, sorry, the 6AU6 tubes.

I fixed the problem. I cheated. I kept going back and forth between the
"good" and "Weak" module. The differences were so subtle. I do think I
have a few weak 6AU5 tubes, but I can not prove that to myself anymore.
Anyway, I cheated and turned the gain of the 545A chassis up (R1027) up a
bit. Now all modules can be calibrated for proper gain.

On Sat, Jun 26, 2021 at 3:42 PM Jeff Dutky <jeff.dutky@gmail.com> wrote:

Where are you seeing CA plug-ins for $10 (much less 99 cents) on eBay? All
I see are $39 + $9.99 shipping.

Not that I need another CA, but at those prices I might have a need for a
parts mule or three.

-- Jeff Dutky






Re: also looking for CMD80 docs....

nonIonizing EMF
 

Rescued another 7904 and a few 7000 series plugins. Made sure to grab a 5000 series plugin as well... even if only for the case and a DP501, TM501, 2 - PG506's and a SG504. I still need to test everything after cleaning and inspecting.

Most all the other Tektronix equipment had been picked other than a dozen or so 500 series plugins if anyone is interested in and a device I've never read about before, a Sony - Tektronix 308 Data Analyzer. I'm in SW Michigan if anyone wants me to grab what's left since sounds like being post 4 rounds of estate sales, the items are going to be scrapped. I couldn't believe the pricing I paid for what I got.

Also, scored another PMI 1038-NS20 with a manual and some H and V plugins for the D14 mainframe with four detectors. There are a few other D14 mainframes left and one is rack mount with the N10.

@nj902 et.al.: On the topic of the Anritsu MT8801B..., found one of those too that came home with me with options 01 and 02. Was wondering if anyone knows if option 07 can be firmware/software turned on or is there internal specific hardware required/modified too?

On Sat, Mar 14, 2009 at 11:57 AM, nj902 wrote:


Alternatively, if you what you really want is an affordable instrument that
works at 1.4 GHz, look no further than the Anritsu MT8801B and its cousins.

Unlike some of the available test sets like the HP89XX instruments that cover
from 1-1000 and then jump to 1.7 to cover the PCS freqs, the 8801 has
uninterrupted coverage to 3 GHz - just be sure to get the analog option and
the spectrum analyzer option. The spectrum analyzer is actually quite
excellent.


Re: Type CA module in a 545

 

Where are you seeing CA plug-ins for $10 (much less 99 cents) on eBay? All I see are $39 + $9.99 shipping.

Not that I need another CA, but at those prices I might have a need for a parts mule or three.

-- Jeff Dutky


Re: Type CA module in a 545

David Kuhn
 

Sorry, I accidentally hit enter and the message was sent before I was done.

The funny thing is it seems one tube being weak appears to drag the gain of
both channels down. Both channel one and channel two tubes sets are
basically in parallel except for the input grids. Any measured voltage
differences between a good gain module and lower gain module are very
subtle.

So at this point, I am not sure what to do, if I really want two good CA
modules (which I really do not, I just like the challenge, or it's my OCD
that drives me to have both the same). They are about $10 each on ebay. One
vendor is selling them "tested" for 99cents each. To purchase four "good"
boxed ones for $10 each is $40+shipping. I'm not sure my OCD is worth
that. lol

It's weird that the module could be that sensitive in design to a slightly
weak tube. Maybe all my 6AU6s are weak and I just do not know the
difference? With the recessed Gain Adjustment, how much overhead gain is
typical for a Type CA module? I would think, best case, I would be
adjusting the gain down a bit instead of having it "just" calibrate with
that pot fully CW.

On Sat, Jun 26, 2021 at 2:43 PM Daveyk021 <daveyk021@gmail.com> wrote:

Well, it's down to the 6AU6 tubes. I got them confused now between the
good module and the bad module. I can make the bad module the same as the
good module by swapping the 6AU6 tubes. I now have the eight 6AU6 tubes
all confused and intermixed - lol.

I have an eico-625 tube tester that I just fixed. It really can not see
the subtle differences between all eight tubes. Some read "630", some read
"640". Not much difference; all read good.

On Thu, Jun 24, 2021 at 12:04 PM David Kuhn via groups.io <Daveyk021=
gmail.com@groups.io> wrote:

"You should check the voltage divider from pin 15 of the plugin connector.
That pin needs to sink 150 mA at 75 volts in all plugins. The 75 volts is
derived from the +100 in the mainframe dropped through a couple of 12.6
volt tube heaters. In many plugins including the CA it is connected to a
combination of tube heaters and divider resistors with taps to provide
bias
for various parts of the circuit. In the CA there are also interconnection
networks with the +100 and +225 pins. One of those voltages from the
divider network is +37.5 that supplies the suppressors of the output
amplifier tubes. If that voltage is not right it could affect the gain of
those stages. There are also +69 and +12.5 volt taps that are used for DC
balance adjustment and to set operating conditions for other parts of the
circuit."

Hello Morris,

I should be checking those voltages and dividers this afternoon. The
filament resistance did go back to about 70 ohms once I wiggled most of
the
tubes and pulled them and re-seated them. The sockets do not look
corroded, but the tube legs themselves are. Getting the
filament resistance down, did nothing for loss of gain in the CA module.

Dave



On Tue, Jun 22, 2021 at 12:42 AM Morris Odell <vilgotch1@gmail.com>
wrote:

You should check the voltage divider from pin 15 of the plugin
connector.
That pin needs to sink 150 mA at 75 volts in all plugins. The 75 volts
is
derived from the +100 in the mainframe dropped through a couple of 12.6
volt tube heaters. In many plugins including the CA it is connected to a
combination of tube heaters and divider resistors with taps to provide
bias
for various parts of the circuit. In the CA there are also
interconnection
networks with the +100 and +225 pins. One of those voltages from the
divider network is +37.5 that supplies the suppressors of the output
amplifier tubes. If that voltage is not right it could affect the gain
of
those stages. There are also +69 and +12.5 volt taps that are used for
DC
balance adjustment and to set operating conditions for other parts of
the
circuit.

Let us know what you find.

Cheers,

Morris










Re: Type CA module in a 545

David Kuhn
 

Well, it's down to the 6AU6 tubes. I got them confused now between the
good module and the bad module. I can make the bad module the same as the
good module by swapping the 6AU6 tubes. I now have the eight 6AU6 tubes
all confused and intermixed - lol.

I have an eico-625 tube tester that I just fixed. It really can not see
the subtle differences between all eight tubes. Some read "630", some read
"640". Not much difference; all read good.

On Thu, Jun 24, 2021 at 12:04 PM David Kuhn via groups.io <Daveyk021=
gmail.com@groups.io> wrote:

"You should check the voltage divider from pin 15 of the plugin connector.
That pin needs to sink 150 mA at 75 volts in all plugins. The 75 volts is
derived from the +100 in the mainframe dropped through a couple of 12.6
volt tube heaters. In many plugins including the CA it is connected to a
combination of tube heaters and divider resistors with taps to provide bias
for various parts of the circuit. In the CA there are also interconnection
networks with the +100 and +225 pins. One of those voltages from the
divider network is +37.5 that supplies the suppressors of the output
amplifier tubes. If that voltage is not right it could affect the gain of
those stages. There are also +69 and +12.5 volt taps that are used for DC
balance adjustment and to set operating conditions for other parts of the
circuit."

Hello Morris,

I should be checking those voltages and dividers this afternoon. The
filament resistance did go back to about 70 ohms once I wiggled most of the
tubes and pulled them and re-seated them. The sockets do not look
corroded, but the tube legs themselves are. Getting the
filament resistance down, did nothing for loss of gain in the CA module.

Dave



On Tue, Jun 22, 2021 at 12:42 AM Morris Odell <vilgotch1@gmail.com> wrote:

You should check the voltage divider from pin 15 of the plugin connector.
That pin needs to sink 150 mA at 75 volts in all plugins. The 75 volts is
derived from the +100 in the mainframe dropped through a couple of 12.6
volt tube heaters. In many plugins including the CA it is connected to a
combination of tube heaters and divider resistors with taps to provide
bias
for various parts of the circuit. In the CA there are also
interconnection
networks with the +100 and +225 pins. One of those voltages from the
divider network is +37.5 that supplies the suppressors of the output
amplifier tubes. If that voltage is not right it could affect the gain of
those stages. There are also +69 and +12.5 volt taps that are used for
DC
balance adjustment and to set operating conditions for other parts of the
circuit.

Let us know what you find.

Cheers,

Morris










Power Supply Issue in a 7934 ?

Liam Perkins
 

I lately picked up a working 7934, SN B021338 that turned out to have
some "UPS mods" to the rear fan housing which necessitated its removal and
disassembly to revert the "body work" to stock format.

In the meantime, and with the side covers in place, I ran the scope
several times for 5-10 minutes to check some plug-ins prior to selling them.

Finishing the last of that and with the scope running I got distracted
by a phone call, someone then came to the door, etc and forgot I'd left it
running. About an hour later I remembered and by that time the scope had
shut itself off due, I hoped, to overheating even though I couldn't find
anything even remotely hot; even the main, rear heatsink was near enough
ambient as to make no difference.

This AM it is dead in the water with the only sign of life at a power
attempt being a couple of flickering neons on a rear-facing board behind
the socket on the CRT, under a clear plastic cover that says, "CAUTION 4KV
Under Cover".

Prior to all this I noticed that, no matter the plug-in or its settings
any trace seemed a bit noisy, leading me wonder about a power supply issue.

TIA for any assistance.

Liam


Re: Wanted: Series 2 or 3 Time Base Module

 

The vintageTEK Museum has a number 2- and 3-series plug-ins. I will be at the Museum today and I'll check.

--
Bob Haas


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

On Sat, Jun 26, 2021 at 01:38 PM, Pitpat wrote:


Like ARES2 EXT: hex=2A3, converted to be 3,29v and tested to be 3,27v
Perfect, no problem at all. Slight deviations are all in the game and negligible compared with the range widths. The values shown here are even nicely bear the midpoint of the ranges.
Albert


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

So, Albert, if I'm getting this right, with a py code like this i should get a quick way to convert those hex.

hex = ''
dec = int(hex, 16)
ARES = (dec*5)/1024
print ("ARES =",ARES,"V")

If so I confirmed the actual values that we got with the DMM correspond to the ones reported by the "excerciser" FP_VALUES with ARES2 always just a bit to low for all the non functioning settings (2s). Like ARES2 EXT: hex=2A3, converted to be 3,29v and tested to be 3,27v

Unfortunately I'll not be at home for the next two days so I'll have to work with the video and the measuremets I've already got.
Federico


Re: A1 board removal? WAS Re: 'splitting' A2 and A3 PCBs when recapping Tek 2465

Jon Nicoll
 

Well, that wasn't too bad - removing the A1 board that is.

Menahem, I have no idea what you meant about not removing the BNC connectors from the chassis (unless you meant the ones at the rear?)

Anyway, removing the front panel assembly was a lot easier than I expected; I hadn't realised it was just a push fit into the chassis aperture. And that gave me access to the six screws which hold the front BNSs to the main casting.

Replacing the A1 caps will be pretty easy I guess. I am a bit nervous about refitting but I am sure a little patience will go a long way.

Cheers, Jon N

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