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Author Topic: FS (US/CAN only) Two HP1740A 100Mhz Dual Trace, $300 for both  (Read 202 times)

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Offline Cliff Matthews

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Both worked when I got them last year (lit graticule and beam finder ok). I decided to open them and check what it would take to eliminate future problems due to older PSU caps, etc. That's when I found that one had an overheat on the transformer molex (possible dry filter cap?) and the other seems fine with all 6 supply rails consistent with service manual. Have not powered them up since and don't have the time to put into them. Buyer covers shipping.

I forgot to show power cords and PSU voltage selector cover-strip for unit with PSU prob (will include that too).























 

Offline Cliff Matthews

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Re: FS (US/CAN only) Two HP1740A 100Mhz Dual Trace, $300 for both
« Reply #1 on: June 20, 2017, 05:54:06 AM »
Here's the plastic cover I missed and some other close-ups on the PSU in question.









 

Offline Cliff Matthews

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Re: FS (US/CAN only) Two HP1740A 100Mhz Dual Trace, $300 for both
« Reply #2 on: June 21, 2017, 07:42:37 AM »
Ok.. So I Googled HP 1740A repair and found this  :palm: (EEVblog#804) where Dave found some bad solder joints. After watching him, PSU pcb removal was easy. At https://youtu.be/7ocancoZ02Q?t=2114 he saw dry joints.  I'm not sure what bridge he replaced (I'll look further..) but the one with the heated molex looks a bit more shabby.










« Last Edit: June 21, 2017, 07:51:55 AM by Cliff Matthews »
 

Offline Cliff Matthews

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Re: FS (US/CAN only) Two HP1740A 100Mhz Dual Trace, $300 for both
« Reply #3 on: June 22, 2017, 05:04:16 AM »
I guess some have noticed the broken bottom legs. This was not abuse, those things are as dry as a dead dingo's donger, so I have some round wooden doweling in the shop I will drill-out, but that's the limit of what I can do now (too busy).
As can be seen, regulator transistors test OK on the scope with the cap and bridge fix (those test OK too). I just can't bring myself to power it up (even without the power distribution pcb installed). I'm the type of guy who'd wait until each rail on the power pcb is 100% load/ripple tested.







 


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