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Old 29th March 2014, 05:36 AM   #21
tomchr is offline tomchr  United States
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Get a service manual so you aren't debugging blind. Artek Manuals have them for download (in exchange for not that much money). I have several of their manuals. They're top notch quality.

+1 for the light bulb tester.

~Tom
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Old 30th March 2014, 12:49 AM   #22
wjcoll is offline wjcoll  Australia
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Thanks Dan,

Will add that to my list of useful tips to employ when I get back to trying to sort out this mongrel.

Cheers,
Wayne
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Old 30th March 2014, 12:53 AM   #23
wjcoll is offline wjcoll  Australia
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Thanks as well Tom,

I've sourced a combined operation and service manual (thankfully) so I have all the schematics and fault diagnosis procedures. Only thing I'm missing is the skill level to be able to solve the problem quickly ;o).

With lots of good advice I've been getting I'm sure I'll figure it out eventually.

Cheers from OZ,
Wayne
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Old 15th May 2014, 04:51 PM   #24
Matt BH is offline Matt BH  United Kingdom
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Hi Wayne any joy with your scope?

Here is the 2236 manual for download, its the same just with a DMM frequency counter on top:

http://bama.edebris.com/manuals/tek/2236/

MY 2235 recently blew up for the second time. This time it is the transformer gone short. Hope yours is not this. Interestingly after disection it is the electrostatic screen on top of the primary that had shorted due to basically selotape being used as insulation.

If you put 41V between TP940 and TP950 positive to TP940 the scope should power up. if it does then its the preregulator that is gone. If you replace U930, Q9070, R926 drifts high and all electrolytics should be replaced as a matter of course as they are nearly 30 years old now.

Hope this helps
Cheers
Matt

Last edited by Matt BH; 15th May 2014 at 04:51 PM. Reason: didnt put the link in, doh.
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Old 15th May 2014, 10:24 PM   #25
wjcoll is offline wjcoll  Australia
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Hi Matt,

Thanks for the tip. I've replaced the rectifier array of diodes (no joy), replaced quite a number of the electrolytics (no joy), stumbled across one that had burst it's backside which I couldn't see until I removed it. I thought Ahah! (no joy).

This is becoming more than a bit frustrating. A tip I received from someone else was to make up a 60W bulb and connect in series in place of the fuse. This give an instant indication if the fault still exists and save sacrificing fuses.

I'll follow up on your suggestion. I've got a lab power supply that I can use to check.

Many thanks,
Wayne
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Old 16th May 2014, 08:17 AM   #26
Matt BH is offline Matt BH  United Kingdom
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Yes they are frustrating to work on. At least doing the 41-43V TP940/950 trick will allow you to isolate which part of the power supply the fault is in. I used two 30V supplies in series and set the current limit around 1A.

You can also lift all the links from the PS section to the rest of the scope. They are labelled on the board +8.6V, -8.6V etc. If the dead elctrolytic you found was on the output side of the supply its fairly likely it has taken out some of the 2A rectifier diodes.

Another common fault is the tripler, it doesnt usually go short but you could disconnect the wire from the top of the transformer to it. Make sure you insulate the wire with something though as there is around 2KV on it. At least with all the links and the tripler disconnected you can get the supply working without any possible faults in the rest of the scope thwarting your efforts.

Cheers
Matt
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Old 28th May 2014, 11:08 PM   #27
Matt BH is offline Matt BH  United Kingdom
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Any joy with it Wayne?

Cheers
Matt.
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Old 29th May 2014, 01:23 AM   #28
wjcoll is offline wjcoll  Australia
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Hi Matt,

No, but I haven't had the time to get back to it unfortunately. Work gets seriously in the way at this time of year and household repair jobs are piling up (so I've been discreetly reminded). I've got all the advice and parts I need, it's just a case now of knuckling down and dedicating some time to it.

Trouble with me is I'm easily distracted.

Won't give up though.

Cheers,
Wayne
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Old 29th May 2014, 11:36 AM   #29
Matt BH is offline Matt BH  United Kingdom
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OK Wayne cool, I have been given a list as long as my arm of stuff to get done.

Cheers
Matt.
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Old 26th June 2014, 01:30 AM   #30
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Hi,

You my find this document I've found on the net interesting.

Regards,

Antonio Falc„o
Brazil
Attached Files
File Type: pdf Troubleshooting_tips_on_2200_series_Power_Supply.pdf (141.9 KB, 17 views)
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