Well... I bought the 1503. How could I resist? The original CL ad listed a price of $150; two days later it was $90. I texted the seller before he changed his mind and two hours later I was sitting in a Starbucks parking lot, trying to explain to a very puzzled man why anyone would buy and fix old test equipment
for fun.
I loaded the 1503 into the truck, went home, shoveled open a spot on the bench and set it up to have a look:
![](http://u.cubeupload.com/worsthorse/tdr1.jpg)
The case is cracked in a couple of places and one of the dials is trashed, otherwise looks good. Open up the 1503 manual on the ipad and off with the case and shields...
![](http://u.cubeupload.com/worsthorse/tdr2.jpg)
![](http://u.cubeupload.com/worsthorse/tdr4.jpg)
![](http://u.cubeupload.com/worsthorse/tdr3.jpg)
No obvious problems, burnt components, bad traces, or poor repair work. I go through it board by board, looking for physical problems, checking to see that the transistors and ICs are all seated, etc. Check the power rails to be sure they aren't shorted to ground or each other. It all looks good, so I decide to see if it powers through the battery connector.
I set up the power supply to current limit, plug it in and see this:
![](http://u.cubeupload.com/worsthorse/tdr5.jpg)
Woo, a trace!
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/xgrin.gif.pagespeed.ic.QVVz6XIT20.png)
The power supply is showing 24VDC and about 150mA current draw. Shut it down again, and turn to the initial setup procedure in the manual. Set that up, turn the 1503 back on, see the trace, and set the impulse width to wide, as instructed. As I do, I watch the trace disappear and the power supply drop to 5VDC, with a 500mA current draw.
Power off, then on long enough to check the power supply board in the 1503. Yup, something on the 25VDC rail has gone funny and the rail is pinned to 5VDC.
Do I dive in? It is in pretty good shape. Maybe the problem is easy. Then I see the stack of TM500 plug-ins that I need to finish. Sooooo... back in the case and onto the repair stack with a note so I don't forget why it is there.
So I will put the manual on my evening reading list and, hopefully, get back to it in a couple or three weeks. I am pretty happy though because it isn't trashed and whatever is going on, I can probably fix.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif.pagespeed.ce._JElyJQqdB.gif)