Date   

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 <hifi@...>
 

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


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

Torch
 

The probes I have use an 11k resistor to ground a spring loaded pin on the probe. The pin contacts a ring which is located on the scope itself, not the probe. The pin is integral to the BNC connector of the probe, not something added on.

Although, I don't see why an adapter couldn't be used, if such a thing exists.

Failing that you could spoof the readout like so:

https://www.jmargolin.com/projects/TekReadout.htm


Re: Wanted: Series 2 or 3 Time Base Module

MaxFrister
 

Thanks for looking.

I'll go the ebay route as a last resort. My last several experiences with ebay have not been positive. Misleading descriptions and bad packing. As far as I can tell, the ebay "came from a working environment" is much like the realtors "cozy" or the advertisers "up to 100% off".

I've made some progress on the 564. I brought it up slowly and on a dim bulb. I've had good luck with the caps in old Tek scopes in the past and this one seems to be working. In contrast I'm working on a similar vintage Hickok scope where every single cap has failed.

I eventually got a fuzzy dot. A bit more work and a fuzzy straight line followed by a sharp straight line. CRT seems sharp and bright!

The two 3A3 modules are dual differential amps --- 2 different vintages and 2 different technologies. I have one working completely and one working on 1 channel. The main thing wrong was severe miss-calibration.

The main thing not working right now is the storage part of the crt. I'll check the high voltage supplies and then try to calibrate it and see if that helps.


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

Albert Otten
 

Hi Federico, I trusted that Table 6-4 would be the same for 2230 and 2232. But in my 2230 pdf the hex values are not shown (but perhaps in another table?), in the 2232 pdf Table 6-4a they are for the A sweep and 6-4b for the B sweep.
The conversion seems to be 0 V -> hex(0) and 5 V -> hex(1024), so you can take hex(204.8*analogV) when the voltage is between 0 V and 5 V.

Albert


Re: New (old) 2247a enquiry

Alex
 

On Thu, Jun 24, 2021 at 10:40 AM, Dave Wise wrote:


Would UF4005 be okay? (Fast-recovery version of 1N4005.)

Dave Wise
UF4005 or 1N4936 both should work fine. Any 1Amp 200-600PIV fast switching diode will work.


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

Albert Otten
 

On Fri, Jun 25, 2021 at 10:23 AM, Pitpat wrote:

I've gone trought those FP_VALUES. I had some difficulty translating them but
ive found some similarites with the DMM measurements that we got (the 0.2s
that does not change when rotated to 0.1s)
"Some similarity" is not enough. The best thing you can do is record for several time/div setting the analog voltages from the DMM together with the hex values from FP_VALUES. Table 6-4 shows for each possible analog range of values the corresponding range of hex values. That makes it easy to check that analog value and hex value are consistent. If there are any inconsistencies then something is wrong in the conversion to hex. (You probably won't verify all time/div settings because of repetition in the switch pattern.) When the analog and digital values are always consistent you don't have to worry anymore about ADCs, MUX or whatever. Moreover then, if you suspect comparators, you might not need DMM measurements any more. You can read the hex values and retrieve from Table 6-4 the corresponding time/div setting, even when the readout says 2s (at least I suppose so). Then you can compare the S701 switch settings between the selected time/div and hex time/div and get a clue which comparator is faulty.

Albert


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

Pitpat
 

I've posted the video, let me know you thoughts.

https://youtu.be/yT2GdiuU3k4


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

Pitpat
 

Hi Albert, I must have missed it when i've gone trought the manual searching for repair tips, thanks!
Now that is something you don't find in todays equipment, Tek. really cared about repairability!
I've gone trought those FP_VALUES. I had some difficulty translating them but ive found some similarites with the DMM measurements that we got (the 0.2s that does not change when rotated to 0.1s)
As the manual states all the values that change more than 5 digits will be highlighted i guess I should be looking for those...
I think i'll try to post a video of me going through all the sweep setting with the exerciser on the screen.

BTW meanwhile I bought a pdf for 2232 S/N B030000-up. The scheme of comparator connections is indeed different from yours.
I had the feeling it would be different, maybe Ed (or who for him) had an enlightment and changed it.
Considering the era they did a brilliant work! If I had to design all that comparators job with the today tech I'd probably just use a microprocessor and some pull-up resistors

Also I really wanted to thank you for all the dedication you are giving to me! I hope someday I can repay you for your kindness!
Federico


Re: 6DJ8 substitute idea - reverse engineering

emissionlabs
 

Hi,

we run a small tube factory in Prague. We build no 6DJ8, but here is what I know about it.

When you use a worn out 6DJ8 only at 2 mA, and high impedance load, the circuit may work fine, even when that tube fails completely in a 15mA circuit, and with more load on it. Reason for this is, when a triode gets weak, Gm goes down, and Rp goes up. Initially with the same rate. Unloaded Gain however is the product of Gm and Rp, and will hardly change, even at some wear out. Not talking about loaded gain. When such a tube is loaded, gain of the circuit will drop, because Rp has gone up. So for an unloaded circuit, Rp going up will help to keep the gain unchanged. But for a loaded circuit, Rp going up will do the opposite. This is why sometimes worn out tubes work well in a circuit with low bias current, and with small or no load, and why sometimes tubes which are different, can replace them.

6DJ8 is often used in mu stage, cascode circuit, because that improves gain and linearity. The tube which gives the gain, comes closer to the data sheet specified mu, and the current source tube is only a high impedance, and requirements to that tube are not much.

The drawback is the high cathode to heater DC voltage of the current source tube, stressing the limits of the tube. The closer you get to that limit, the more noise or leakage problems you get from it when the tube ages. Because not only dynamic parameters age, but also isolation gets less. It's a good idea when interchanging 6DJ8, 6922 and 6N23 amongst each other in a cascaded circuit, to check the actual cathode to heater voltage of the specific ciruit, vs the specifications of the tube you use as a replacement. Because that has quite some differences. And when you have the tube tester for it, measure the resistance of a cathode to heater, while the tube is at full plate dissipation. Leakage will go up drastically above 80% of maximum anode dissipation, and even a leaky cathode will measure fine at only 20% of anode dissipation. So not compare to the data sheet, but to the real tube you use. Since this resistor is "connected" to the cathode, that gives sputter or click noise, the closer you come to (or exceed!) the maximum isolation voltage.

6922 and 6DJ8 is not quite the same. Heater current is different, and with replacement types, that useually results in differences, not just with heater current. So when the isolation layer between heater and is made different, that will affect heater current and isolation voltages too. 6DJ8 has larger bias differences between the two triodes, and maximum heater to cathode voltage is another. It is curious how tubes which are quite different can sometimes substitute one another, but only when the circuit designer says so. Moreover 6DJ8 is a frame grid tube, with the many virtues belonging to it, and 6BQ7 is not.

Jac

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