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7B85 odd behavior

unclebanjoman
 

Hi all,

Just arrived a 7B85 delaying time-base in decent conditions. I never owned one.
Waiting for its companion 7B80 (I bought it on the flybay), I performed a rapid functionality check.

It works somewhat well with one exception: selecting the "B starts after delay" button I can see the intensified portion.
Turning the DELAY TIME knob, the intensified portion of the waveform does not move continuously but "jumps" from one cycle to the next. (or previous if turning CCW).
The readout shows a continuously delay time instead (as should be).
I'm using a 7B53 as delayed time-base in B slot. The delayed waveform is displayed correctly but, as I stated previously, its position does not vary continuously when turning the delay time knob of the 7B85.

Also "B triggerable after delay" doesn't works as expected. Turning the "Delta Time" knob simply causes the second intensified portion to jump from one cycle to another.

Am I doing something wrong?

Thanks,
Max

Albert Otten
 

Hi Max,

Seems to be an incompatibility of the 7B85/7B53A combination in a 7854. Behaves the same wrong way in my equipment. So wait for your 7B80 as delayed time base.

Albert

On Tue, Jun 18, 2019 at 03:58 PM, unclebanjoman wrote:


Hi all,

Just arrived a 7B85 delaying time-base in decent conditions. I never owned
one.
Waiting for its companion 7B80 (I bought it on the flybay), I performed a
rapid functionality check.

It works somewhat well with one exception: selecting the "B starts after
delay" button I can see the intensified portion.
Turning the DELAY TIME knob, the intensified portion of the waveform does not
move continuously but "jumps" from one cycle to the next. (or previous if
turning CCW).
The readout shows a continuously delay time instead (as should be).
I'm using a 7B53 as delayed time-base in B slot. The delayed waveform is
displayed correctly but, as I stated previously, its position does not vary
continuously when turning the delay time knob of the 7B85.

Also "B triggerable after delay" doesn't works as expected. Turning the "Delta
Time" knob simply causes the second intensified portion to jump from one cycle
to another.

Am I doing something wrong?

Thanks,
Max

unclebanjoman
 

Thank you Albert!
I will wait for the 7B80, then!

I'm curious: I don't understand how 7b53 can affect the 7b85 delay time control in such a manner ...

Max

johncharlesgord
 

Max,

The 7B53A is waiting for the next trigger event to start its sweep (and intensify the trace). It is apparently not set up to recognize the "start immediately after delay" condition, at least as operated in the 7854.

--John Gord

On Tue, Jun 18, 2019 at 09:05 AM, unclebanjoman wrote:


Thank you Albert!
I will wait for the 7B80, then!

I'm curious: I don't understand how 7b53 can affect the 7b85 delay time
control in such a manner ...

Max

Albert Otten
 

Yes, this is more or less described in the "Delayed Mode Control" paragraph at page 2-10 in my 7B53A/AN manual. I found no such description in the 7B85 manual, though in the B compartment a 7B85 behaves the same as a 7B80. BTW I checked things in a 7704A, not a 7854.

Albert

On Tue, Jun 18, 2019 at 07:35 PM, johncharlesgord wrote:


Max,

The 7B53A is waiting for the next trigger event to start its sweep (and
intensify the trace). It is apparently not set up to recognize the "start
immediately after delay" condition, at least as operated in the 7854.

--John Gord

On Tue, Jun 18, 2019 at 09:05 AM, unclebanjoman wrote:


Thank you Albert!
I will wait for the 7B80, then!

I'm curious: I don't understand how 7b53 can affect the 7b85 delay time
control in such a manner ...

Max

unclebanjoman
 

Hi John,

the intensified portion of the trace is pertinent to the 7B85 in the "A" slot. The time-base in "B" slot should show the delayed trace only (and in fact it works).
If I turn the Delay TIme knob on the 7B85 I expect to see the intensified portion moving horizontally without interruption, on the "A" display (the mainframe is in Horz CHOP mode). The "B" delayed display should move accordingly.

My 7B53, 7B92 (used alone) and my beloved 475, all behaves in a such manner.

Max

johncharlesgord
 

Max,

I agree, one would want it do work that way, and it does with the 7B80 as the delayed plugin. The intensification is keyed to the actual start of the B sweep, and if that sweep is delayed because the B sweep is waiting (incorrectly, but it wasn't really deisgned with this situation in mind) for a trigger, you get the jumps in intensified location. The intensification path is from the "Sweep Gate (B)" signal through U190 on the Mainframe Logic board (A14). If the B sweep delays until a trigger event, the intensified portion will also delay.

--John

On Tue, Jun 18, 2019 at 11:26 AM, unclebanjoman wrote:


Hi John,

the intensified portion of the trace is pertinent to the 7B85 in the "A" slot.
The time-base in "B" slot should show the delayed trace only (and in fact it
works).
If I turn the Delay TIme knob on the 7B85 I expect to see the intensified
portion moving horizontally without interruption, on the "A" display (the
mainframe is in Horz CHOP mode). The "B" delayed display should move
accordingly.

My 7B53, 7B92 (used alone) and my beloved 475, all behaves in a such manner.

Max

unclebanjoman
 

Well explained, John!
Now everything is much clearer to me! Thanks a lot!

Max

unclebanjoman
 

Thinking on John's explanation, I found a way to make 7b85 and 7b53A work correctly together.
Just tried, it works.

It's simple:
1) open the right cover panel of the 7854 and locate the switch S46 on the A15 Signal Output board
2) Set the switch in the "A Dly'd" position
3) Connect the +Gate Out out located on the 7854's rear panel to the MAIN TRIG IN of 7B53A front panel.
4) Set the 7B53A's MAIN TRIG SOURCE button to EXT/10 (or EXT if input signal is too low)
5) Set 7854 Horz. Mode to CHOP or ALT
6) Push 7B85's button "B starts after delay"
7) Adjust 7B53A trigger level if necessary.
8) Note that now the intensified portion on A sweep moves smoothly while turning the 7B85 Delay time knob. The B sweep generated by the 7B53A is displayed and moves accordingly.
8) Enjoy!

Max

Albert Otten
 

Clever solution Max.
BTW a 7B80 is somewhat more convenient for "B starts after delay" since then the B time base triggers automatically, regardless the Level etc. setting. I have sometimes used a +GATE output as input to a counter, with the scope as pre-amplifier of a weak signal under study (too weak and perhaps too complex for the counter).

Albert

On Wed, Jun 19, 2019 at 01:03 AM, unclebanjoman wrote:


Thinking on John's explanation, I found a way to make 7b85 and 7b53A work
correctly together.
Just tried, it works.

It's simple:
1) open the right cover panel of the 7854 and locate the switch S46 on the A15
Signal Output board
2) Set the switch in the "A Dly'd" position
3) Connect the +Gate Out out located on the 7854's rear panel to the MAIN TRIG
IN of 7B53A front panel.
4) Set the 7B53A's MAIN TRIG SOURCE button to EXT/10 (or EXT if input signal
is too low)
5) Set 7854 Horz. Mode to CHOP or ALT
6) Push 7B85's button "B starts after delay"
7) Adjust 7B53A trigger level if necessary.
8) Note that now the intensified portion on A sweep moves smoothly while
turning the 7B85 Delay time knob. The B sweep generated by the 7B53A is
displayed and moves accordingly.
8) Enjoy!

Max