Author Topic: Tek 2246MODA some buttons don't work (Read 26477 times)

RobII · « **on:** October 18, 2015, 05:17:09 am »

Hi All!! New poster so hope this is the right spot. I recently picked up a used Tek 2246 and it mostly works. I am having issues with some of the buttons not working. Specifically, Down buttons for Mode (A, B XY etc), trigger mode, coupling and source. Top menu button, display clear, AC coupling and Channel 3 select all seem to do nothing. The other channels (1,2 and 4) all seem to work ok.

I am new to owning a scope so I need a little direction. I have not yet removed the cover. Is this even worth an attempt to repair?

Thanks in advance!!

Rob

xwarp · « **Reply #1 on:** October 19, 2015, 08:59:26 am »

2246A? or 2246 with Mod A?

I have a 2246A and YES, worth the repair.

Have you downloaded the service manual for it?

http://exodus.poly.edu/~kurt/manuals/uploads/

Get both manuals.

The manual will tell you how to go into service mode and test the front panel buttons.

RobII · « **Reply #2 on:** October 19, 2015, 12:02:05 pm »

I do have both manuals. Problem with getting in to service mode. Manual says to press top and bottom menu buttons, top menu button is not working so can't access service menu. I am debating whether I should open the case.

tec5c · « **Reply #3 on:** October 19, 2015, 12:08:15 pm »

Open it up. It's possible (and likely if the unit has seen some rough days) that the contacts of the buttons have become misaligned/dirty/sticky etc.

Feel free to post some pictures once you've opened it up. Or if you're not confident in opening it up, just say so and we can give you some guidance.

As always, a picture tells a thousand words.

sync · « **Reply #4 on:** October 19, 2015, 12:09:26 pm »

I would carefully reseat the flex cables which go to the front panel first. Maybe it's just a bad contact. My trust in these connectors are limited. I have a 2246A. It's a nice scope.

RobII · « **Reply #5 on:** October 19, 2015, 12:20:34 pm »

Alrighty, I may just take the plunge and give it a go. I will post pics after work today.

Thanks a million!!!

RobII · « **Reply #6 on:** October 19, 2015, 05:25:40 pm »

Sorry xwarp, didn't see your question. It's a 2246MODA.

Quote from: xwarp on October 19, 2015, 08:59:26 am

2246A? or 2246 with Mod A?

I have a 2246A and YES, worth the repair.

Have you downloaded the service manual for it?

http://exodus.poly.edu/~kurt/manuals/uploads/

Get both manuals.

The manual will tell you how to go into service mode and test the front panel buttons.

xwarp · « **Reply #7 on:** October 19, 2015, 06:19:34 pm »

Ok. So 340 of the pdf I am looking at for the Mod A is the switch diagram/interface.

Please list ALL the specific buttons that don't work.

Just want to see if all those that don't work are in common.

Next step will be removing the outer cover and then looking at reseating all the connectors that attach to the front panel.

RobII · « **Reply #8 on:** October 19, 2015, 08:51:38 pm »

Will do. I'm getting out of work in another 10 minutes. I'll get all the buttons and post some pics as well.

Thank you so much!

Rob

Quote from: xwarp on October 19, 2015, 06:19:34 pm

Ok. So 340 of the pdf I am looking at for the Mod A is the switch diagram/interface.

Please list ALL the specific buttons that don't work.

Just want to see if all those that don't work are in common.

Next step will be removing the outer cover and then looking at reseating all the connectors that attach to the front panel.

RobII · « **Reply #9 on:** October 20, 2015, 01:15:30 am »

Here is the list of buttons that do not seem to do anything.

Clear Display
Top Menu button
Fourth Menu button
Volt meter Ch1/2
Channel 3 Mode
Scope BW / 20Mhz
AC Coup Channel 1 and 2
Mode down arrow A, Alt, B, XY
Channel 3 5v / .1v Div
Under the trigger section
Slope
Mode down arrow
Source down arrow
CPLG down arrow

I am attaching pics and circled the affected buttons.

Also the A and B intensity knobs don't seem to do anything either.

xwarp · « **Reply #10 on:** October 20, 2015, 02:14:25 am »

Under the Vertical section, can you select Ch 4?

and then for channel 4, the button that selects the voltage scaling of either 5 or .1 v per/div, does that work?

Check your private messages.

RobII · « **Reply #11 on:** October 20, 2015, 02:22:27 am »

Yes, I can select channel 4 and the 5 /.1 div does come on.

pvt msg received.

Quote from: xwarp on October 20, 2015, 02:14:25 am

Under the Vertical section, can you select Ch 4?

and then for channel 4, the button that selects the voltage scaling of either 5 or .1 v per/div, does that work?

Check your private messages.

tec5c · « **Reply #12 on:** October 20, 2015, 02:35:57 am »

Well that's more faulty buttons than I first thought.

How do you feel about taking the cover off? There's a mesh O-ring like seal around the inside edge of the casing for these models of scopes used for grounding, nothing to worry about now though when you're putting it back together you need to ensure that everything is seated properly and that the mesh is making good contact.

Also, there's a Yahoo group for Tek scopes with an incredible variety of knowledge, perhaps it's worth a browse through there to see if anyone else has had a similar problem.

sync · « **Reply #13 on:** October 20, 2015, 12:21:32 pm »

All switches on the AS3 line of the switch matrix doesn't work. And it looks like that the LEDs on AS3 aren't working too. One trigger mode LED should glow. So the AS3 line is dead.

Have you reseated the front panel connector?
And visually inspect the cable, connector and PCB area for any damage.

tec5c · « **Reply #14 on:** October 20, 2015, 01:22:56 pm »

Well, there you go! That narrows it down by a substantial amount.

Check Q2503 along with all cable connections.

RobII · « **Reply #15 on:** October 21, 2015, 12:09:10 am »

I got the case cover off (NOT FUN!!). Got the potentiometer(sp?) board off. How the hell do I get the switch board assy off and the face plate? I did reseat the ribbon cable here

and tested before I tore into it. No change.

sync · « **Reply #16 on:** October 21, 2015, 12:49:22 am »

No need to disassemble the switch board at the moment. The fault could be a component shown in your photo. Can you check the marked transistor (see attachment)? It drives the AS3 line. You can check it with a multimeter in the diode test function (scope powered off). All 6 possible combinations. Compare it with one or two of the other transistors.

Do you have another scope available?

RobII · « **Reply #17 on:** October 21, 2015, 01:28:30 am »

Awesome. Ok, here's what I get when testing the transistor you pointed out. Forgive me, I'm not sure if these are NPN or PNP so bare with me on my "testing". Checked it with the negative on the middle pin and positive on what was my right side pin.

Got this for a reading with a short beep.

All of the other transistors I tested in the same fashion had this for a reading or slightly higher.

Are we on the right track?

Thanks for your help!!!

xwarp · « **Reply #18 on:** October 21, 2015, 01:37:06 am »

It's a 1 watt Darlington NPN transistor. MPS6725.

In the picture where you see the your leads on the transistor, it's pins from left to right are Emitter, Base, Collector.

RobII · « **Reply #19 on:** October 21, 2015, 01:43:45 am »

So I was testing the Emitter and Base pins. Is that one of the correct ways to test?

xwarp · « **Reply #20 on:** October 21, 2015, 01:50:06 am »

In the picture, the two pins you appear to be on are the base and collector.

If you are up to it, and very carefully, using the negative lead on a ground point, and the positive lead on the square pad you see, which is the Emitter pin, look at the DC voltages and see if that transistor has a different voltage.

RobII · « **Reply #21 on:** October 21, 2015, 01:53:17 am »

I'm assuming you mean power it on and check (i just want to make sure lol).

xwarp · « **Reply #22 on:** October 21, 2015, 02:02:14 am »

Yes, and STAY AWAY from the high voltage supply area.

tec5c · « **Reply #23 on:** October 21, 2015, 02:05:31 am »

Quote from: RobII on October 21, 2015, 01:53:17 am

I'm assuming you mean power it on and check (i just want to make sure lol).

Yeah, with power on.

RobII · « **Reply #24 on:** October 21, 2015, 02:08:43 am »

Ok, From my first pic (pins showing) moving from the bottom transistor to the top

1 = 1.37vdc
2 = .775vdc
3 = .960vdc
4 = .540vdc
5 = 1.60vdc
6 = 1.64vdc


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Author Topic: Tek 2246MODA some buttons don't work (Read 26477 times)

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