Have you checked the control input levels at pin 4 and pin 14 and the
power supply pin voltages at pin 3 and pin 5?

What about the DC bias levels at all of the input and output pins?
They are marked on the schematic.

The cascode bias at the base of Q2101 and Q2102 should be checked as
well.

On Wed, 25 Jan 2012 22:42:52 -0000, "david_s5y" <david_s5@...>
wrote:

Hi,

This is getting weirder, but I am sure it means something to someone....

Store is active.

I set up to put a 3.5 V 1kHz signal into CH1, and turned the CH1 sensitivity down to 5mV. *Ch2 is set to ground*

Then Chn 1 displayed a clamped to a square wave version of the input.
movable by Chn 2' position to only show the half the signal (positive) peeks on the CRT.

Now setting Vert Mode to both gives me 2 versions of the clamped. Chan 2 is 2X the amplitude of chan 1.

Chn 1's Position does nothing. But cha 2's position moves both wave forms.

Setting it to Chn 2 gives me one waveform that is 2X.

As I decrease the Chan 1 Sensitivity the waveform begins to round to a sine wave.

Does this and the +5 V on pin 6 and 11 indicate a bad U2101?

Next Q does someone have a TEK 234-0408B-20, they would like to sell?

开云体育

On Thu, 26 Jan 2012 13:54:41 -1000, "David Sidrane" <david_s5@...>
wrote:

3 to gnd 1.38 - Where is this tied?

5 to gnd 6.8

Good. These are the IC power pins. They are connected through a
couple of diodes to ground and the 8.6 volt supply as shown on
schematic 11.

If you can dig up the Tek-Made book, the data sheet for the
155-0022-00 is on page 5-7 although I do not think you need it yet.

4 Ch 1 or Both 1.68

Good.

Ch 2 4.0

Bad. But the biasing problem below might be the cause.

14 Both Add 6.16

14 Both Alt/Chop 1.44

14 ch 1 Alt/Chop/add 1.44

14 ch 2 Alt/Chop/add 1.44

All good. The voltages read about 1.4 volts high because the IC
ground reference at pin 3 is raised by two series connected diodes
shown on schematic 11.

DC bias

15 1.8

16 1.04

1 1.16

2 1.94

Good.

7 4.31

8 3.51

9 3.17

10 3.93

Bad. These are way off. The external negative bias to -5 volts could
be missing and causing all of the problems.

Check R2101, R2102, R2109, R2105, and R2106. Look for an open
resistor or trace.

Q2101/2 Base 5.04

Good.

What about pins 12 and 13?

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of David
Sent: Thursday, January 26, 2012 10:59 AM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Tek 2230 - Storage does not work.

Have you checked the control input levels at pin 4 and pin 14 and the
power supply pin voltages at pin 3 and pin 5?

What about the DC bias levels at all of the input and output pins?
They are marked on the schematic.

The cascode bias at the base of Q2101 and Q2102 should be checked as
well.

On Wed, 25 Jan 2012 22:42:52 -0000, "david_s5y" <david_s5@...
<mailto:david_s5%40usa.net> >
wrote:

Hi,

This is getting weirder, but I am sure it means something to someone....

Store is active.

I set up to put a 3.5 V 1kHz signal into CH1, and turned the CH1

sensitivity down to 5mV. *Ch2 is set to ground*

Then Chn 1 displayed a clamped to a square wave version of the input.
movable by Chn 2' position to only show the half the signal (positive)

peeks on the CRT.

Now setting Vert Mode to both gives me 2 versions of the clamped. Chan 2 is

2X the amplitude of chan 1.

Chn 1's Position does nothing. But cha 2's position moves both wave forms.

Setting it to Chn 2 gives me one waveform that is 2X.

As I decrease the Chan 1 Sensitivity the waveform begins to round to a sine

wave.

Does this and the +5 V on pin 6 and 11 indicate a bad U2101?

Next Q does someone have a TEK 234-0408B-20, they would like to sell?

开云体育

On Thu, 26 Jan 2012 19:01:32 -1000, "David Sidrane" <david_s5@...>
wrote:

-5% is Good. The Resistors all measure good and are connected. Both the chan
1 and 2 emitter networks measure the same values.

12 5.00
13 5.83

13 is good but 12 is off and being limited by the internal
back-to-back diodes on the ouput.

The base of Q2105 is -3.5 - which seems way off

Yep. It is being pulled low by constant current sink Q2104 and not
being balanced by Q2103 for some reason.

What should I see on 6 and 11 of U2101?

Didn't we post that earlier? It was like -2.5 volts or something on
the 2230 oscilloscopes we checked. I am hoping to find an external
cause for the problem and not a bad channel switch.

Time to check the parts around Q2102, Q2103, and Q2104. A shorted
Q2102 or Q2104 could cause the base of Q2105 to be low. Check the
voltage at the base and collector of Q2104. Check R2146.

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of David
Sent: Thursday, January 26, 2012 2:58 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Tek 2230 - Storage does not work.

On Thu, 26 Jan 2012 13:54:41 -1000, "David Sidrane" <david_s5@...
<mailto:david_s5%40usa.net> >
wrote:

3 to gnd 1.38 - Where is this tied?

5 to gnd 6.8

Good. These are the IC power pins. They are connected through a
couple of diodes to ground and the 8.6 volt supply as shown on
schematic 11.

If you can dig up the Tek-Made book, the data sheet for the
155-0022-00 is on page 5-7 although I do not think you need it yet.

4 Ch 1 or Both 1.68

Good.

Ch 2 4.0

Bad. But the biasing problem below might be the cause.

14 Both Add 6.16

14 Both Alt/Chop 1.44

14 ch 1 Alt/Chop/add 1.44

14 ch 2 Alt/Chop/add 1.44

All good. The voltages read about 1.4 volts high because the IC
ground reference at pin 3 is raised by two series connected diodes
shown on schematic 11.

DC bias

15 1.8

16 1.04

1 1.16

2 1.94

Good.

7 4.31

8 3.51

9 3.17

10 3.93

Bad. These are way off. The external negative bias to -5 volts could
be missing and causing all of the problems.

Check R2101, R2102, R2109, R2105, and R2106. Look for an open
resistor or trace.

Q2101/2 Base 5.04

Good.

What about pins 12 and 13?

From: TekScopes@... <mailto:TekScopes%40yahoogroups.com>

[mailto:TekScopes@... <mailto:TekScopes%40yahoogroups.com> ] On
Behalf

Of David
Sent: Thursday, January 26, 2012 10:59 AM
To: TekScopes@... <mailto:TekScopes%40yahoogroups.com>
Subject: Re: [TekScopes] Re: Tek 2230 - Storage does not work.

Have you checked the control input levels at pin 4 and pin 14 and the
power supply pin voltages at pin 3 and pin 5?

What about the DC bias levels at all of the input and output pins?
They are marked on the schematic.

The cascode bias at the base of Q2101 and Q2102 should be checked as
well.

On Wed, 25 Jan 2012 22:42:52 -0000, "david_s5y" <david_s5@...

<mailto:david_s5%40usa.net>

<mailto:david_s5%40usa.net> >
wrote:

Hi,

This is getting weirder, but I am sure it means something to someone....

Store is active.

I set up to put a 3.5 V 1kHz signal into CH1, and turned the CH1

sensitivity down to 5mV. *Ch2 is set to ground*

Then Chn 1 displayed a clamped to a square wave version of the input.
movable by Chn 2' position to only show the half the signal (positive)

peeks on the CRT.

Now setting Vert Mode to both gives me 2 versions of the clamped. Chan 2

is

2X the amplitude of chan 1.

Chn 1's Position does nothing. But cha 2's position moves both wave forms.

Setting it to Chn 2 gives me one waveform that is 2X.

As I decrease the Chan 1 Sensitivity the waveform begins to round to a

sine

wave.

Does this and the +5 V on pin 6 and 11 indicate a bad U2101?

Next Q does someone have a TEK 234-0408B-20, they would like to sell?

On Thu, 26 Jan 2012 13:54:41 -1000, "David Sidrane" <david_s5@...>
wrote:

DC bias

15 1.8
16 1.04

1 1.16
2 1.94

7 4.31
8 3.51

9 3.17
10 3.93

Here is something else to try. Swap P2111 and P2112 so that channel 1
and channel 2 are swapped and measure these voltages again.