Topics

Tek 2430 (Non-A) with Strange Problem


Mike Harmon
 

A few days ago, I got a 2430 from my friend at the local electronics emporium. He said it came up, but smelled bad, so he shut it down. When I got it home, I pulled off the case, turned a fan on the CCDs and fired it up to check the voltage rail test points on the side board. Every one measured exactly where it was supposed to be. The Self-Test screen came up for several seconds and then the screen went immediately into a display of the A and B sweep lines. I was able to move them all around, and when I hooked the probe to the calibrator, I got a nice square wave.

Since I wasn't familiar with the 2430, I went to the other side of the shack to pull up the user guide on the computer. A few minutes later, I went back to the scope. The 3 GPIB status LEDs were still lit, but there was nothing on the screen at all. The fan was also throwing out a LOT of "scorched PCB" smell (hot phenolic). I shut the scope down and waited a couple of hours, then tried powering it up again. Absolutely nothing on the screen. The longer I had it powered up the stronger the scorched smell got, so I shut it down.

I spent half of last night removing the boards from the scope and carefully inspecting them for any signs of overheating. Nothing. No scorched spots on the boards, no visibly overheated components, no discoloration anywhere. This morning, I put everything back together and fired it back up with the fan on the CCDs. Every single voltage test point on the side board showed exactly on spec. By the time the scope was on long enough to make the measurements, it was really starting to stink again, so I shut it down.

At this point, I am stumped! I have the complete (original) 070-4917-00 (1-1/2") manual and I'm reasonably experienced at trouble shooting, but I'm sort of at an impasse. I would have thought that anything that caused that much of a stink ought to show some physical signs of overheating somewhere, but to this point, I haven't been able to find any.

Anyone out there who has experience with a 2430? Do these symptoms sound familiar to anyone? The NVRAM battery measures 3.07V, but I wouldn't think that a bad battery would cause the whole screen to go blank (?).

I know the smell was there before I fooled with the scope, because the guy at the store mentioned it, but the scope did work the first time I had it powered up (for a few minutes anyway).

Your sage advice and suggestions are most welcome!
73,
Mike Harmon, WB0LDJ
mharmon at att dot net


Harvey White
 

Depending on the smell (5$, 10$, 20$.....) it could be the RIFA capacitors on the power input.  Those are known to fail, and especially in 220 volt land.  (NOTE: I had some fail in a 120 volt application, likely same smell).  Nothing will indicate a failure *in* the scope, but you still have a potential problem.

Harvey

On 8/5/2020 6:46 PM, Mike Harmon wrote:
A few days ago, I got a 2430 from my friend at the local electronics emporium. He said it came up, but smelled bad, so he shut it down. When I got it home, I pulled off the case, turned a fan on the CCDs and fired it up to check the voltage rail test points on the side board. Every one measured exactly where it was supposed to be. The Self-Test screen came up for several seconds and then the screen went immediately into a display of the A and B sweep lines. I was able to move them all around, and when I hooked the probe to the calibrator, I got a nice square wave.

Since I wasn't familiar with the 2430, I went to the other side of the shack to pull up the user guide on the computer. A few minutes later, I went back to the scope. The 3 GPIB status LEDs were still lit, but there was nothing on the screen at all. The fan was also throwing out a LOT of "scorched PCB" smell (hot phenolic). I shut the scope down and waited a couple of hours, then tried powering it up again. Absolutely nothing on the screen. The longer I had it powered up the stronger the scorched smell got, so I shut it down.

I spent half of last night removing the boards from the scope and carefully inspecting them for any signs of overheating. Nothing. No scorched spots on the boards, no visibly overheated components, no discoloration anywhere. This morning, I put everything back together and fired it back up with the fan on the CCDs. Every single voltage test point on the side board showed exactly on spec. By the time the scope was on long enough to make the measurements, it was really starting to stink again, so I shut it down.

At this point, I am stumped! I have the complete (original) 070-4917-00 (1-1/2") manual and I'm reasonably experienced at trouble shooting, but I'm sort of at an impasse. I would have thought that anything that caused that much of a stink ought to show some physical signs of overheating somewhere, but to this point, I haven't been able to find any.

Anyone out there who has experience with a 2430? Do these symptoms sound familiar to anyone? The NVRAM battery measures 3.07V, but I wouldn't think that a bad battery would cause the whole screen to go blank (?).

I know the smell was there before I fooled with the scope, because the guy at the store mentioned it, but the scope did work the first time I had it powered up (for a few minutes anyway).

Your sage advice and suggestions are most welcome!
73,
Mike Harmon, WB0LDJ
mharmon at att dot net



Craig Cramb
 

I know the smell was there before I fooled with the scope, because the guy at the store mentioned it, but the scope did work the first time I had it powered up (for a few minutes anyway).

I would recommend that you replace all the electrolytic capacitors on the power supply before you power it up multiple tests and disassembly. I could do this service for you if interested as this is usually the first thing that I do when working on a 2430 series. It’s a fair amount of caps to be replaced but that is your best bet to get a scope reliable.
Pulling these units apart does take some patience.
Craig
Electronixtoolbox at gmail


Lawrence Glaister
 

I have had several pieces of gear start to "stink". The cause has been leaking electrolytic caps. These have been from small 100uf/25v to larger power supply caps. One has to look very carefully at the cap for any signs of bulging tops or around the base of the pcb mounted caps for any signs of leakage. The leakage will create havoc with the pcb traces and you may end up have to jumper around damaged PCB traces. The smell could best be described as a bad case of body odour. If you have friends in the lab, everyone will be looking around trying to figure out who forgot to shower a week ago!. Equipment with exhaust fans are very good at filling the room with odour. The problem with using the nose to locate the parts is that it seems after several sniffs to saturate and no longer work as a good detector. This problem affected a lot of equipment from around 2000 including computer motherboards.
Happy hunting!

Lawrence VE7IT
Automation Engineer

On 2020-08-05 4:58 p.m., Harvey White wrote:
Depending on the smell (5$, 10$, 20$.....) it could be the RIFA capacitors on the power input.  Those are known to fail, and especially in 220 volt land.  (NOTE: I had some fail in a 120 volt application, likely same smell).  Nothing will indicate a failure *in* the scope, but you still have a potential problem.
Harvey
On 8/5/2020 6:46 PM, Mike Harmon wrote:
A few days ago, I got a 2430 from my friend at the local electronics emporium.  He said it came up, but smelled bad, so he shut it down. When I got it home, I pulled off the case, turned a fan on the CCDs and fired it up to check the voltage rail test points on the side board.  Every one measured exactly where it was supposed to be.  The Self-Test screen came up for several seconds and then the screen went immediately into a display of the A and B sweep lines.  I was able to move them all around, and when I hooked the probe to the calibrator, I got a nice square wave.

Since I wasn't familiar with the 2430, I went to the other side of the shack to pull up the user guide on the computer.  A few minutes later, I went back to the scope.  The 3 GPIB status LEDs were still lit, but there was nothing on the screen at all.  The fan was also throwing out a LOT of "scorched PCB" smell (hot phenolic).  I shut the scope down and waited a couple of hours, then tried powering it up again. Absolutely nothing on the screen.  The longer I had it powered up the stronger the scorched smell got, so I shut it down.

I spent half of last night removing the boards from the scope and carefully inspecting them for any signs of overheating.  Nothing.  No scorched spots on the boards, no visibly overheated components, no discoloration anywhere.  This morning, I put everything back together and fired it back up with the fan on the CCDs.  Every single voltage test point on the side board showed exactly on spec.  By the time the scope was on long enough to make the measurements, it was really starting to stink again, so I shut it down.

At this point, I am stumped!  I have the complete (original) 070-4917-00 (1-1/2") manual and I'm reasonably experienced at trouble shooting, but I'm sort of at an impasse.  I would have thought that anything that caused that much of a stink ought to show some physical signs of overheating somewhere, but to this point, I haven't been able to find any.

Anyone out there who has experience with a 2430?  Do these symptoms sound familiar to anyone?  The NVRAM battery measures 3.07V, but I wouldn't think that a bad battery would cause the whole screen to go blank (?).

I know the smell was there before I fooled with the scope, because the guy at the store mentioned it, but the scope did work the first time I had it powered up (for a few minutes anyway).

Your sage advice and suggestions are most welcome!
73,
Mike Harmon, WB0LDJ
mharmon at att dot net