Date   

Re: TM500 Tester Board Sets Delivered!

Dave Seiter
 

Larry,
Thank you once again for your effort!  
-Dave

On Friday, March 19, 2021, 12:20:01 PM PDT, Larry McDavid <lmcdavid@lmceng.com> wrote:

The final shipment of TM500 tester circuit board sets was delivered to
UK a few days ago. Tracking showed one delivery to Spain still pending
but upon inquiry it turns out that package was delivered more than two
weeks ago but Spain did not update the tracking data.

So, that completes the TekScopes and Tek500 group purchase of these
circuit boards. I have residual boards for all but the main circuit
board. Jared Cabot is working to set up an independent order record at
PCBWay so that interested individuals can order the main board; PCBWay
will have a minimum order of five boards and we don't yet know the price
for such a small quantity of those circuit boards. I'll report that when
I hear from Jared or he may announce it himself here.

Well, it has been an experience! I did not anticipate such a large
response when I innocently inquired here if anyone was interested in a
group purchase of boards! And, we have learned that international
shipment delays are unpredictable now.

I wish all the tester builders well and remind you that support
information will come from Jared Cabot. I am just a messenger!

--
Best wishes,

Larry McDavid W6FUB
Anaheim, California  (SE of Los Angeles, near Disneyland)


TM500 Tester Board Sets Delivered!

Larry McDavid
 

The final shipment of TM500 tester circuit board sets was delivered to UK a few days ago. Tracking showed one delivery to Spain still pending but upon inquiry it turns out that package was delivered more than two weeks ago but Spain did not update the tracking data.

So, that completes the TekScopes and Tek500 group purchase of these circuit boards. I have residual boards for all but the main circuit board. Jared Cabot is working to set up an independent order record at PCBWay so that interested individuals can order the main board; PCBWay will have a minimum order of five boards and we don't yet know the price for such a small quantity of those circuit boards. I'll report that when I hear from Jared or he may announce it himself here.

Well, it has been an experience! I did not anticipate such a large response when I innocently inquired here if anyone was interested in a group purchase of boards! And, we have learned that international shipment delays are unpredictable now.

I wish all the tester builders well and remind you that support information will come from Jared Cabot. I am just a messenger!

--
Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)


Re: 7D15 internal trigger not working

Mark Vincent
 

Steve,

Check the 151-0402-00 transistors. These are the same number as the 151-0367-00 3571TP. These are likely leaky. I had a triggering problem with mine and these transistors were bad from C to E. These check as a diode that way. I put in KSP10BU as replacements. You should see the leakage in-circuit. A VTVM or VOM on R X1 will have about mid-scale deflection on the leaky ones.

Check the ESR of C27, C40, C127 and C140. If high, replace them. Mine were high and were replaced with film types. See if any other of the 1mfd axial condensers are high in ESR and replace those that are high.

Mark


TDS 684 Scope

Thomas Dodge
 

Hi,
I have several Tektronix scopes. My newest one is a TDS 684A, and I have posted about it before. I found it in a surplus place, and I had been wanting to pick it up for a long time. When I brought it home, and powered it on, all the panel lights came on, but didn't do anything else. I powered it on and off a few times, and it started to work, ran the self test, and everything was cool. I kept it on for a while, and then turned it off. So it is a little tempermental. I am trying to find out if there is anyone in the San Gabriel valley area near Pasadena, who I can work with to fix this scope. It is in excellent condition, and is the best scope I have out the three scopes I have. If anyone can let me know if they know someone in this group, that would be great. Thanks.
Thomas Dodge


Re: Replacing a 7000 MF Rear Interface Connector: IS THIS EVEN POSSIBLE?

Clark Foley
 

After 45 year, I can still her that sound again. No. This is not a translation of Bizet’s Les pêcheurs de perles.
That distinctive crunch was an immediate indictment to all the someone has abused the poor mainframe. If you were lucky, it was a couple if pins accessible from the left or right side of the instrument. There were a couple people on the manufacturing line who were very good at reworking those connectors but you got a scolding first. One “bad dog” lecture taught me the lesson!
If you have a donor, use it. If you are daring (dashing won’t help this time), have infinite patience, a steady hand and some clever fixturing for alignment, you might get most of the pins restored. My experience from long ago was that there was always a pin that looked ok but should have been replaced.
Use the donor and use your spare time to listen to some Bizet.


Re: 7L5 dot frequency reset bug - any clues or a fix?

Richard Steedman
 

Dan, did you ever get round to trying your proposed fix of increasing the C841/R841 time constant? I can confirm that the 7934 mainframe also has the issue. See two photos here of the >1s delay after power-on before TS1 pulses appear. I suspect the issue affects any mainframe using a readout system newer than the original analog ROM board (e.g. microprocessor for the 7854 and EPROM-based board for 79xx). I suppose these days one could also whip up a fix using a PIC to drive TS1 pulses into the serial clock input shortly after power-on and then get out the way to allow option circuitry to take over.


Re: Changing out GR874 connectors +Printact relays

Ed Breya
 

The 576 uses some Printact relays. Ed


Re: 485 super weak brightness control

Mark Vincent
 

Ondrej,

Note where the pots R863, R1226 and R1228 are and turn them back and forth. One or more may have a open due to not ever being moved and turning it restores contact. Check for B+ at places that got to a supply voltage, e.g. H3 and H4. Some other contacts short/go to to ground, e.g. G1 on <7>. See if those are going to ground. The relay mentioned earlier could have dirty contacts in it. Another part that can give problems are 151-0367-00 (selected from 3571TP). These usually are leaky from C to E. Later ones that have a blue face are alright. Black face ones are very likely leaky. I have replaced them in scopes and 7B time bases with KSB10U. The pinout is different for these, BEC. The leakage was a problem, for me, at the higher sweep speeds and was right after I replaced the transistors.

Mark


Re: Q122/222 Jfet J300 subs for 2215A scope ?

charlesterrebonne@...
 

We will have closure to this thread/story now:

I ordered 25 x J300 (NOS?) from BGMicro after previous poster pointed out they had some...hoping these were real/NOS...because no photos of markings on part...ok lets try...if these are real NOS a few J300s can be nice to have around...because this was now just a matter of getting an answer to this story...I have several more recent oscilloscopes...

Parts arrived this morning. Im not fake a semiconductors expert but I have bought & seen a lot (too many) fake semiconductors in last years. The J300s from BGMicro looked ok to me.

I Installed a random J300 jfet from the 25 in ordered (tested quickly with PIC based component tester... didnt test IDSS) in Q222 position (B Channel) of the 2215 Tektronix scope that I had tried so many other jFETs in there to sub a J300 Jfet (read thread for whole story)...and...Works!

Looks like : These scopes were built with J300s Jfets there. Thats what was in the orig working channel. Thats what works. This scope looks like it was a repair attempt of a defective channel with a J210 Jfet (tried several other # Jfets) that doesnt sub for a J300 in that circuit.

Thanks to all who commented and contributed and extra thanks to SCMenasian who pointed me to BGMicro for some J300s...with a coupon code...that worked


Re: Changing out GR874 connectors +Printact relays

Stephen
 

Interesting comment.
Which type of female Type N connector would you use on a type 106 where it’s mounted/soldered directly on the high-rise board?
I’m looking at all the best options available.


Re: SC502 looking for a replacement of dual 6-pin FET in input stage DON'T TRY THIS

Jim Adney
 

2N3958 Followup:

Looking at the 2N3958 datasheet, I see that the 2N3957 and 2N3956 are better matched versions of the same dual JFET. I find a few of them, at increased prices on ebay, but none in stock at Mouser. The 2N3958s are cheap enough that I'd start there and see if that was good enough.


Re: SC502 looking for a replacement of dual 6-pin FET in input stage DON'T TRY THIS

Jim Adney
 

I checked, and the 2N3958 is in stock at Mouser for ~$13 each. There are lots of offers on ebay between $3 and $10 each, almost all from Asia, and better offers if you care to buy 3 or 5 at a time. The ones I have bought from Asia have worked fine for me.

The 2N3958 is a monolithic dual n-channel JFET in the 6-pin metal TO-71 can. Datasheets are available online.

If space makes installation difficult, I suspect a suitable installation tool could be made from a short length of brass tubing from the telescoping assortments available from almost any hobby or hardware store. Deform the JFET end to make it a spring fit on the TO-71 body while bottoming out on the brim of the "hat.".


Re: Replacing a 7000 MF Rear Interface Connector: IS THIS EVEN POSSIBLE?

Tom Norman
 

Hi Dennis-

I've made two flexible 7000 series extenders based on using salvaged back plane connectors and a couple of circuit boards I had made. On the donor board, I just removed the plastic retaining strips, and desoldered and removed each contact finger one by one. Once the connector was stripped bare of its contacts, I transplanted the connector body onto my extender board, and working one side at a time, loosely installed the contact fingers, installed the retaining strip to hold the contacts in place, and soldered. The retaining strips to my eye adequately ensured the contacts were seated and aligned in their grooves so that I could then solder them into place. I can't imagine a good result trying to remove the connector without disassembly without damage. As Ed indicated, piecemeal seems to be the safest and best, but I'd add to that the use of the retaining strip to hold the new contacts in place prior to soldering to ensure correct alignment. Hope that last bit isn't being "master of the obvious".

Tom


Changing out GR874 connectors +Printact relays

 

I see some comments about changing existing GR874's in Tek gear for BNCs with some loss of performance. I think a better and certainly easier mechanical change is to female type N connectors, which are very good performers, up to at least 12.4Ghz. Getting good N cables is easy, and eliminates the need for the pesky GR874 adaptors, plus provides a better high speed transition to the cable itself.

In our lab, virtually all high frequency connections are N connectors (generators, power meters, analyzers, loads, etc.), with SMA to go higher in frequency or smaller in physical size. Only scopes really remain with BNCs, but they are much lower in frequency than the microwave gear. Both APC-7 and GR874 were phased out internally some years ago, just too much inconvenience, and not enough benefit.

Also, totally un-related, I found a box of new gold Printact relays (they use the other half of the contact system as the pcb itself). These were used in some HP audio signal/level generators (with very mixed results), but I had never seen them in any Tek gear. Does anyone know if they where used there? They were in my Tek spares, so that's why I am curious.

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


Re: 7D15 internal trigger not working

Dan G
 

On Fri, Mar 19, 2021 at 09:48 AM, Steve Nossen wrote:

I don’t have an extender and the -5 volt power supply board in the
counter is over the trigger circuits, making observation of the circuit nearly
impossible.
The -5V power supply board can be removed from the main PCB, and
then re-installed perpendicular to it, to allow access to components
underneath. (There should be three spare sockets on the A8 board
mounted at 90 degrees to the main sockets for just this occasion.
Make certain that all three sockets engage their pins properly.)


dan


Re: Replacing a 7000 MF Rear Interface Connector: IS THIS EVEN POSSIBLE?

Chris Wilkson
 

I can't comment on the 7603 backplane...I don't have one handy. But I can recommend the Hakko FR-301 desoldering gun for delicate multipin component removal.
Early 70's coin op mainboards have very small solder pad annuli and *VERY* poor epoxy. It quite easy to lift traces/pads with traditional tools. But I've never lifted one with the Hakko.
Same situation....delicate boards with components that can't be replaced and must be reused.

If there's room to get the gun nozzle over the pin then it will definitely help you.


7D15 internal trigger not working

Steve Nossen
 

I recently brought my 7D15 out of storage and found that when plugged into the 7704A it took down the display. A second insertion in to the 7704A brought some smoke, quickly identifying the bad capacitor as C931, a 15 uF 16 volt device. I replaced with a 10uF, 25 volt device and the counter is back alive.

This was one of my favorite 7000 series plugins. When I started out I was doing Digital Signal Processing hardware using serial arithmetic and this counter was invaluable in counting clock pulses associated with each math operation using the delayed sweep gate as an event counter gate. A digital filter with 30 multiply accumulates has a sequence of 30 groups of 32 clocks. Try counting that manually on a 7904 screen. The 7D15 made that easy.

The remaining problem is a non working internal trigger. It does work if I overdrive the vertical input by about 3 screens and a 7B53A works fine in that slot so I believe the problem is in the internal trigger amplifier, Q203, Q213 and Q217 in the counter. It could also be the internal/external trigger switch. I don’t have an extender and the -5 volt power supply board in the counter is over the trigger circuits, making observation of the circuit nearly impossible. The trigger circuit is on the left side of the plug in so I can look at it in a vertical slot but can't feed a trigger signal to it while in a vertical slot.

My plan is to get a connector, Digikey 345-076-520-201-ND, remove the -5 volt supply board and power the counter externally, including the -5 volt supply. Then I can look at the voltages/waveforms in the circuit. Any thoughts on the debug process are appreciated. Has anyone had this problem and found a sore spot in the circuit? The 68 uF capacitor on the -5V supply tests OK. The -5 volt is -5V.


Re: 485 super weak brightness control

Ondrej Pavelka
 

On Thu, 18 Mar 2021, 17:02 Ozan, <ozan_g@erdogan.us> wrote:


Now I have nice sharp trace and working intensity control!
Good progress.

Horizontal A sweep
The 5 2 and 1nS settings are not working at all.
485 uses B sweep generator for 5/2/1ns settings even in A sweep setting.
Since you are seeing functional 5/2/1ns in B sweep it is a problem of scope
not selecting B sweep in 5/2/1ns settings as it should. In those settings
do you see B sweep ramp (while you are in A sweep setting on the knob) at
collector of Q1236 of sheet <9>? What is the voltage at pin N1 sheet <12>
when you are in 5/2/1ns settings (0.6V expected) vs above 5ns setting
(-0.5V expected)?
This is flipping correctly between -06 and +05

I noticed when I move the picture all the way to the left in 521 mode there
is something on the screen but it's all crooked


I don't get any B sweep from 5s to 20ms then I get good B sweep for 10mS
to
0.2uS
0.1uS to 10nS is showing only first 4 divisions from the left
Probably next step of debug.

5 2 and 1 ns is working correctly.
See above. A sweep uses B sweep generator for 5/2/1ns.

Power supply fan.

Is quite picky, it sometimes runs and sometimes it does not.
Siggi's link is great. The other thing to check is if you give it a gentle
push if it starts rotating. The fan speed is temperature controlled, C1482
looks like it is placed there to give an initial kick. You may want to
replace C1482 to see if it makes any difference.

Ozan







Re: 485 super weak brightness control

Ondrej Pavelka
 

On Thu, 18 Mar 2021, 20:47 Ozan, <ozan_g@erdogan.us> wrote:


I think we are in a different time zone, I always get the messages as
soon
as a leave the workshop and go home.
I am close to San Francisco, California (more precisely in Silicon Valley
area).

I'm not sure if it's important observation but all the horizontal
calibration is miles out. When I have say both A and B set to 10uS A is
roughly 50% out and B is totally out by 300 or 400%
Just to make sure: Is variable setting of time/div in "cal" position? You
may want to exercise it few times to make sure switch is good.

I think you measured +50V and it was good. Timing uses +50V for its
current sources so it should be accurate and low ripple.
50 is beautiful with 2mV of ripple



These settings use different timing caps:
How much is A/B off in 0.1us to 1ns (I know only B side works 5/2/1ns)
and are all the speeds about same percentage off?
How much is A/B off in 0.2us to 10us and are all the speeds about same
percentage off?
How much is A/B off 20us to 1ms, and are all the speeds about same
percentage off?
How much is A/B off in 2ms and slower speeds, and are all the speeds about
same percentage off?

Are the sweeps linear, if you apply a sine wave does it cross horizontal
axis uniformly?
Nice and linear


Ozan










Re: 485 super weak brightness control

Ondrej Pavelka
 

Ok better observations

A sweep is actually spot on time wise

B sweep in the positions 10uS to 0.2uS is showing it 10x wrong

So 100nS is shown as 1uS

In positions 0.1uS to 10nS it displays correct timing but it doesn't
display it across whole screen. What is displayed is displayed correctly in
the right half of the screen but left half has super faint few pulses as if
they were compressed but they are barely visible

On Thu, 18 Mar 2021, 21:45 Ozan, <ozan_g@erdogan.us> wrote:


I'm in Prague, Czech Republic, Central Europe
Couple of years back I was planning to go to Prague during an Europe trip
but timing didn't work out. Hopefully soon when travel is safe again.

Since our timings are off here are more considerations while you are on
the scope:

Relays K879 and K1242 are on a socket and easy to pull if you are careful.
While putting back pins has to align so that they don't bend. Although I
expect timing to be much worse if they are bad, they are easy to test.
However, the main reason for removing is you can test the timing caps
easily once they are out. If you forget to mark the orientation (like I
did) pinout is 180-degree symmetric as far as I remember.

With the relays out you can test the timing capacitors C1405 and C1404 at
G3/G5 terminals (and equivalent on B side). Just turn the time/div knob to
close the proper switch. Also measure the resistance from each leg to
ground. Although figure shows a floating cap in reality they are caps with
three legs, the outer leg is a shield and connected to ground. On my 485
there was a short between one of the terminals and outer shield (ground).

You can also observe A sweep out at the BNC for linearity.
Ozan







4141 - 4160 of 184483