Hi guys,

I have recently bought a Tektronix 2246 oscilloscope from Ebay and after about a few weeks of joy the things become a bit temperamental. Basically it will occasionally fail to power up and it seems to be getting worse with time.

When it does power up it works perfectly.

When it fails to completely power up you can hear the relays turning on and off approximately every second. The indicator lights on the scope also flicker.
It does not get to the stage where the fan turns on and the CRT begins displaying.

I have the operators manual but there is no mention of this and I cant see a troubleshooting or disassembly section etc.

I really don't want to have to send this back. This should be fixable! Only problem is I think a scope would help find the problem and this is my only one... Catch 22!

Does anyone have any ideas or helpful advice?

Thanks,

 

Sounds like either the power supply or something on the high voltage side loading the power supply and shutting it down. Here's a link to a 2245 manual which may be close enough for you. I think the only difference between the two is the built in voltmeter and auto measurement functions:
http://www.ko4bb.com/cgi-bin/manuals...tronix_-_2245A

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There are also two wonderful Tektronix_oscilloscope-related yahoo groups called TekScopes and TekScopes2. Take a look there.

 

Thanks Kchristie for the link to the Service manual, its a big one! Where to begin!

And thanks felis for the heads up about the user group, I'm now pending approval to get access!

 

Hi,
My Tek 2246A too gave up, the Channel 1 and 2 are both at its voltage limits and are not working, channel 3 and 4 do work.
I think that the Vertical preamps somehow got damaged.
Searching google i came here and tried that service manual link for the 2245a, but it doesnt work anymore.
It would be great if someone who downloaded it could send it to me or upload it somewhere else.
my email: theundefined AT gmx . net

Thanks in advance
Peter

 

Hi,
I found the link somewhere else in the net
http://tonga.globat.com/~ko4bb.com/c...tronix_-_2245A
Thanks

 

Peter02,

If you need more assistance then sign up for the Yahoo user group TekScopes as suggested above. I have yet to get round to fixing my particular problem, but the group certainly looks like a good source.

Good luck fixing your scope!

Cheers,

Mendoza

 

Hi,
Thanks for the advice, have signed up for that group and am now waiting for approval from the group owner. I have isolated the failure to the vertical preamp board, and very likely to one little ic there which is printed with "TI848B 271AC" have not found any info about it so far, the Service Manual treats the whole Board as U112 and does not say what is on it. Maybe someone in the Yahoo group knows more.
Greetings
Peter

 

Mendoza:

Did you find a solution for the problem with your 2246? Mine did exactly the same thing and I've been through the power supply but can't find the problem yet. I did sign up for the Yahoo group and am waiting to be approved.

 

I purchased a 2246A that was still within its calibration cycle and demonstrated to be fully functional. When I received it (after it was shipped across several states) and turned it on nothing happened except for a relay actuating. When I relayed my disappointment to the seller he suggested that I re-seat all of the ribbon cable connectors. I was very skeptical when I opened the unit and found them all apparently seated. I did however jiggle each of them and ensured that they were fully seated. I buttoned it up and reapplied power; it came up immediately, fully functional, and has worked flawlessly ever since.

 

9 of 10 Tektronix oscilloscopes of a couple dozens I have repaired suffered from horrible power supply unreliable design and cheap parts in them.

Strongly suggest you look for open electrolytic capacitors in the switching power supply.
Come back with findings.
Miguel

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