I'm apparently the not so proud owner of yet another broken
oscilloscope. This time it's a Tek 2205 with a sick power supply
section.

The eBay guide says that the 2205 is not a very wonderful scope:
http://reviews.ebay.com/Buying-an-Oscilloscope-on-ebay_W0QQugidZ10000000001568756
"Stay away from the 2205, 2225 they were made in the orient,
and have serious quality issues as used scopes."
Oh well. At least it was free.

The outputs of all the various PS voltages are low (not zero). For
example, the 250v line measures about 15VDC. I've checked all the big
caps with an ESR tester and found nothing unusual or suspicious. When
I first inherited the scope, the green pilot light came on but nothing
else. By the time I got it open and started making measurements, the
green pilot light went away. I disconnected all the various power
supply connections (that conveniently run through 0 ohm jumpers) but
the power supply lines still have low output, even with no load. I
have a schematic and service manual.

However, I'm also lazy, have better things to break, and really don't
know why I'm bothering to fix a 20MHz scope. Are there any common or
chronic problems with the 2205 power supply section to check before I
dive into the mess, rip it apart, and probably electrocute myself in
the process?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann schrieb:

I'm apparently the not so proud owner of yet another broken
oscilloscope. This time it's a Tek 2205 with a sick power supply
section.

The eBay guide says that the 2205 is not a very wonderful scope:
http://reviews.ebay.com/Buying-an-Oscilloscope-on-ebay_W0QQugidZ10000000001568756
"Stay away from the 2205, 2225 they were made in the orient,
and have serious quality issues as used scopes."
Oh well. At least it was free.

The outputs of all the various PS voltages are low (not zero). For
example, the 250v line measures about 15VDC. I've checked all the big
caps with an ESR tester and found nothing unusual or suspicious. When
I first inherited the scope, the green pilot light came on but nothing
else. By the time I got it open and started making measurements, the
green pilot light went away. I disconnected all the various power
supply connections (that conveniently run through 0 ohm jumpers) but
the power supply lines still have low output, even with no load. I
have a schematic and service manual.

However, I'm also lazy, have better things to break, and really don't
know why I'm bothering to fix a 20MHz scope. Are there any common or
chronic problems with the 2205 power supply section to check before I
dive into the mess, rip it apart, and probably electrocute myself in
the process?



AFAIR the 2205 has a toroid transformer to set up a low DC of approx.
40 Volts and provides mains isolation. Folowed by a switchmode that
converts the DC into all aother voltages needed in the 2205.

I's d recommend you look for a service manual, and follow the
schematic.In my repairs the following: In the switchmode the usual
suspects: caps, transistors, secondary HV multiplier. I don't know if
bama has one for download, but it is worth a try.

hth,
Andreas