I´m waiting to receive one 7B92 that I have bought cheap beacuse I need pulse diodes, and this time base has 6 fast TD diodes.

I don´t understand what you neen to know.
what does it mean free run hold off?

It seems that this time base don´t have a variable hold off control.

Hello Rick,

may you use the e-mail
massner@external.hft-leipzig.de
please.

Best regards,

Stephan

the voltages on the vert position pot wipers is as follows fully ccw=3.6v,halfway point =1.2v,fully cw =3.6v.

Here is a PDF of the datasheet for the Greyhill 71BDF30-02-2-AJN switch
that was recommended for the tester. The stop pins are shown on page 11. <
http://www.farnell.com/datasheets/20309.pdf> If your switch doesn't have
the adjustable stop pins then you may have a different model switch.

On Mon, Oct 25, 2021 at 5:38 AM Colin Herbert via groups.io <colingherbert=
blueyonder.co.uk@groups.io> wrote:

Ah, But that order was from Mouser, not DigiKey like mine. My switch was
just in a bubble-wrap bag in another plastic bag.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Shaun
M
Sent: 24 October 2021 19:37
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 tester switch - Attn. Jared Cabot.

Colin,

I purchased the parts for this project from Mouser in January of this
year. The Grayhill switch we are discussing arrived packed a plastic tube
and included the pins, stickers and paper instructions for configuring it.

Shaun M

Greetings Stephan,
A quick message to ask whether the TM506 is still available and, if so, whether I can put in my request 🙏

Thank you,

Rick.

The vintageTEK Museum has just released a new version of the 4051 Rampack, It is the same form factor as a rompack, and can store 2MB (equivalent to 7 DC300 tapes) of programs and data in rewritable flash memory. It comes preloaded with 140 demos, utilities and graphics files. It is on the vintagetek Ebay store.
--
Bob Haas

Dear all,

if anybody is interested in the following parts, please write me a PM, please.

Mainframe TM506 (working unit) including
Word Recognizer/Delay WR501 (without cables)
Digital Delay DD501 and
Logic Analyzer LA501 (P6450 included but without further accessories)

Probably, I'ld find the cable for the WR501 within the next days while
clearing our old lab - but I'm not sure.

We're encouraged about a donation for our kitty (thank-you box).

Best regards,

Stephan

All teh plugins are spoken for as are the 7603 and 7613

--
Oz (in DFW, Texas USA) N1OZ

I have a small device that uses a 9600 baud rs-232
connection for communication that's not working correctly.
I thought I could use my 308 to take a look at the
data stream and I can't seem to get the right setup for
it to recognize the data. All I get are "+++" marks.

I have it connected on the TTL side, not the external
+/- 12V side. The trigger LED does flicker, but no
data is displayed.

Any one ever use this to look at a serial data stream?
Any ideas on the setup? There are not a lot of parameters
to fiddle with here, but I haven't found the right combination
yet.

thanks
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows

7B92, S/N B052568, No Sweep, Help!

Thanks Miguel,

TP321, and R765, have ~60mv, ½ usec pulses. So pulses but probably not functional. I went back and checked carefully on all pins of U310 and found, in addition to those noted below, several volt 200 nsec pulses on 16 and 17. All are at the same frequency and in phase with the HO ramp.



Since it has been almost a year since my 7B92 arrived in my new-to-me 7904 I’ve decided that it is time to make it work. I’ve re-posted with a new title since it may have been confused with “..no repeating sweep”

The first question might be is it normal for the Hold-Off circuit to free run? I have not found a configuration where it does not free-run at a frequency determined by timing switches 7, 8, 9 and 10.

Test setup
‘92 installed in right-most slot of a 7603. No vertical plug-ins installed. (The 7603 has been tested with a 7B53A in the right-most slot and a 7A26 in the left-most slot.) The side covers have been removed from the ‘92. The side covers are removed from the 7603 giving good access to the main trigger board and the sweep board.
The external trigger is driven by the cal-out of a 7904 set to 1kHz and 0.4 volts. The termination is off. Trigger is set to Auto, DC coupling, External. The “Alt” and “Level” controls are pushed in. Sweep speed set to 20 uSec/division. The “Triggered” light is off when powered-up but come on and stays on if single-sweep is selected.

U310 Voltages, taken with Fluke 115, Waveforms observed with 7409/7A26/7B53A combo:
Pin # name Voltage
1. +TD input 1.159
2. -TD input 0.232
3. + TD Auto 0.331
4. - TD Auto 4.890
5. -5V -4.980
6. Auto timing 0.022
7. Tgd Lamp 4.602
8. HO timing 2.239 + Hold-Off ramp, ~4V P-P, 40 uSec
9. 0.001
10. HO out 0.289 + 0.5 usec 6V pulses at HO frequency (25kHz)
11. SS ready 4.663
12. 0.013
13. 0.216
14. Reset timing 4.716
15. Reset start 0.762
16. 0.074 2V 200 nsec pulses
17. SWP disable 1.686 3 V 200 nsec bipolar pulses
18. Lockout input -0.006
19. Auto Mode 0.001
20. +5V 4.889
And:
TP 392 4.367V
TP 321 1.429V
C 1.61V + Hold-off pulses
E 0.115V + Hold-off pulses
CR740 (TD) ~1.5uSec, ~600mv pulses at Hold-Off ramp freqeuncy
Q754 base 0.747V
Q748 base 0.790V

I'm building a replacement U400 from discrete surface mount components. I'll let you know how it works out.

On Mon, Oct 25, 2021 at 12:02 AM, <nanovnauser@gmail.com> wrote:

Well i hooked up the eht to the crt and moved the whole lot to one side,heres
a few readings i took,on q387 base i get 8.8v,it should be 2.6!,r290 wiper
measures as follows,fully cw=3.44,fully ccw 3.4v,r190 is fully cw3.4,fully ccw
3.4v,dont know if this helps?

---
Base voltage at Q387 doesn't point to a failure by itself. We need voltages at other nodes to tell which component failed. This was the list in the earlier message:

Voltage at bases of Q350, Q360, Q376, Q386
Voltage at collectors of Q377, Q387
Voltage at the bases of Q370, Q380
Voltage at the collectors of Q370, Q380

R290 and R190 voltages look fine if you are measuring voltage at the wiper (center) terminal.

Ozan


Ozan

Do you have pulses at TP321?

If I change the sweep speed such that there are more cycles/division, the hook seems to stay in the same place but intersects the first cycle just a bit. Essentially, the hook doesn't seem to change much, if any, at different sweep speeds.

Thanks,
Barry - N4BUQ

7B92, S/N B052568, No Sweep, Help!

Since it has been almost a year since my 7B92 arrived in my new-to-me 7904 I’ve decided that it is time to make it work. I’ve re-posted with a new title since it may have been confused with “..no repeating sweep”

The first question might be is it normal for the Hold-Off circuit to free run? I have not found a configuration where it does not free-run at a frequency determined by timing switches 7, 8, 9 and 10.

Test setup
‘92 installed in right-most slot of a 7603. No vertical plug-ins installed. (The 7603 has been tested with a 7B53A in the right-most slot and a 7A26 in the left-most slot.) The side covers have been removed from the ‘92. The side covers are removed from the 7603 giving good access to the main trigger board and the sweep board.
The external trigger is driven by the cal-out of a 7904 set to 1kHz and 0.4 volts. The termination is off. Trigger is set to Auto, DC coupling, External. The “Alt” and “Level” controls are pushed in. Sweep speed set to 20 uSec/division. The “Triggered” light is off when powered-up but come on and stays on if single-sweep is selected.

U310 Voltages, taken with Fluke 115, Waveforms observed with 7409/7A26/7B53A combo:
Pin # name Voltage
1. +TD input 1.159
2. -TD input 0.232
3. + TD Auto 0.331
4. - TD Auto 4.890
5. -5V -4.980
6. Auto timing 0.022
7. Tgd Lamp 4.602
8. HO timing 2.239 + Hold-Off ramp, ~4V P-P, 40 uSec
9. 0.001
10. HO out 0.289 + 0.5 usec 6V pulses at HO frequency (25kHz)
11. SS ready 4.663
12. 0.013
13. 0.216
14. Reset timing 4.716
15. Reset start 0.762
16. 0.074
17. SWP disable 1.686
18. Lockout input -0.006
19. Auto Mode 0.001
20. +5V 4.889
And:
TP 392 4.367V
TP 321 1.429V
C 1.61V + Hold-off pulses
E 0.115V + Hold-off pulses
CR740 (TD) ~1.5uSec, ~600mv pulses at Hold-Off ramp freqeuncy
Q754 base 0.747V
Q748 base 0.790V

It would be good to know whether the "hook" changes if you change the sweep speeds (both) and what the nature of the changes, if any , are.

Stephen Menasian

Jeff,

Swapping boards is a good way to determine problems. Swapping ICs would be next to see if any are bad.

Removing the trigger light is easy. It snaps in. Pry the black cap of the back. You can ohm out the lamp to see if it is open before removing the cap. If the lamp is bad, it is a 683.

The knobs on the time base have a narrow range of position when put back on. If the large knob is put on too far back, it will do what you are seeing. There will be too little back movement. Move the knob out a bit to see if that helps. Cleaning the switches will help. You may have to remove the board to get access to the set screws on the part that moves the switches if moving the knob does not help. Make sure not to allow the cams to turn if you remove the board! Be sure not to loose the pin that pushes the nylon bobbin that actuates the microswitch lever. The clear part that shows the time/div. adjusts the amount of movement. That also has a narrow range it can be secured to open and close the switch.

The Var. control can come out by loosening the set screws on the collar that is connected to the black part to the control. You do not need to remove the readout board to do this step.

You may have to have both shafts out to get them straight.

Mark

So I got a second 7B92, and this one mostly works (TIME/DIV shafts are bent, trigger lamp does not illuminate, something wrong with ALT horizontal mode when TIME/DIV knob is pushed in, and delayed sweep triggering is wonky), so I'm planning to swap boards between the two units to narrow down the location of the fault (or try to make one fully working unit, though I'd prefer to fix both).

My first questions is: is this a good plan, or am I likely to spread the failures around?

Second question is about the faults in the new unit:

1. The trigger indicator does not light. How difficult is it to replace that lamp? It doesn't look like I can remove the lamp from the back; do I need to pull the face plate (and all the knobs) off to replace the lamp, or am I missing something obvious?

2. The problem with ALT mode appears to be that the TIME/DIV knob does not return all the way when pushed in, and the slide switches behind the cam-switch housing are not closing in their back positions. Is there a way to adjust the position of the actuating flange on the outer shaft, or do I need to disassemble the knob and perform some kind of maintenance on that?

3. I have managed to straighten the TIME/DIV shaft by brute force, without removing the shaft from the unit, but it's still messed up. I had expected to be able to release the VAR/CAL shaft from behind the cam-switch housing just by loosening a set screw, but it turns out that, unlike the same shaft in the 7B53A, this one has a flange on the end that prevents it from being extracted through the outer shaft. Is there a way to remove the CAL/VAR shaft that doesn't involve complete disassembly of the cam-switch?

4. If worse comes to worse I suppose that I can swap the entire TIME/DIV cam-switch assembly between the two units. I know that I'm not supposed to remove the screws on the back of the cam-switch (the ones that also hold the readout board to the cam-switch body), but is it safe to remove the entire cam-switch body from the main interface board?

-- Jeff Dutky

I added a photo here:

https://groups.io/g/TekScopes/photo/252850/3326143

Thanks,
Barry - N4BUQ

That's correct. Only in mixed mode.

Thanks,
Barry - N4BUQ