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JDR Instruments model 3500

H

HighPlainsDrifter$

307 WYYOMING
Mar 12, 2021
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Has anyone here had any experience with this make and model? It appears to work on both channels at least when connected to my signal generator, it arrived Thursday but I've been putting all new springs on my F-150 so the scope took a back seat till that was finished. I located a manual but it is only 28 pages and wont be here for a few days yet. Any insight would be greatly appreciated .... Thank You016.JPG
 

Maybe no one has heard of these ... It did blink a couple times, not sure why, I have no training in oscilloscope I was looking around inside and found a mystery. Not sure why any one would cut what appears to be a ground wires from the position pot on both channels leading to one of the boards ..... Advise?? ..... as with any used equipment buyer beware, but I rolled the dice.IMG_0563.JPG IMG_0573.JPG
 
JDR was a mail-order chip and parts seller back in the day. They expanded to selling computer boards in the late 80s and into the 90s. I know we bought memory chips from them 30 years ago.

The 'scope is one I have seen with more then one name brand on the front. Had one sold by MCM Electronics with their "Tenma" name on the front. Seems to me we had one years ago that said "Elenco" on it.

We got about ten years out of it. Seemed to be a decent-enough 25 MHz 'scope. Being powered up ten hours a day for that long eventually caught up with it. Buying a used replacement for it was clearly cheaper than taking the time to fix it, so it got sidelined.

I recommend using a times-ten probe. A straight probe puts all the capacitance of the shielded lead in parallel with the tip. Tends to load down any RF circuit when the probe tip touches it. The "X10" probe will usually have less than 10pf of capacitance to ground on the probe tip. That will still disrupt the tuning of some RF circuits, but not nearly as much.

I consider a decent 'scope to be the swiss-army knife for troubleshooting a circuit fault. Good score!

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Thank You for some thoughts on this scope, any thoughts on the 2 cut wires .... think a guy should reattach or leave it be? They start at the housings of the position pots, I am not sure what if any difference reconnecting them would have. Would a recap be a good idea, they all look good to the naked eye. One more thing ... this was sold to me as 35Mhz are you saying it is only 25Mhz ...... I would not have made the deal knowing that.
 
Brain fart. Pretty sure ours was 35 MHz, not 25. I'm gonna guess that the cut wires are the shield conductor. Sometimes that will get grounded at one end of a shielded wire only, but not at the other end. Connecting the ground from one section to the ground in another section can cause a problem called a ground loop. If that's the case here, leaving one end loose would have been done to fix that. This might be what's going on. Don't remember seeing this in our 'scope, but that doesn't prove a thing.

So long as the cut end doesn't brush up against something with juice on it, you're safe to try using it this way. It's possible they're supposed to be that way.

Possible.

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Thank you and yes I will try to use it as it is .... not that I know just how to use it correctly but if others can learn, so can I. Both ground wires were connected and then cut .... I suspect that someone has tried to treat a symptom and not solve the problem. Probably to make the sale ..... mission accomplished there. Forgive my cynicism but its hard to deal with today's sellers, sometimes it seems they will do anything to make the sale the old used car salesman thing. I can believe these were brand many different names, a CA. company but made in Korea according to the tag on the back. I had a hard time finding a manual under the JDR name possibly find more info under another name if I need to solve a problem. Thank You again I appreciate you insight.
 
The correct manual showed up this morning .... Very informative, heavy reading ... for me. While going thru the setup instruction I noticed that when moving one of the probes the trigger light was going on and off, I suspect a broken conductor in the coax. When I went to look for a pair of replacements I was bombarded with endless choices, can anyone here direct me to the good ones, our landfills are overloaded with china garbage now I don't want to add to the problem or buy the junk that every peddler and his dog have out there to lure a guy in.
Thanks
 

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