Thanks for making this video - I have one of these scopes dating to the early 80's. My scope's horizontal sweep was affected - the trace all the way over on the left side of the screen. I watched your video, downloaded the schematics and took the top off the beast. Checked the PS voltages like you did and found them to be off. I'm thinking it must be bad electrolytic capacitors in such an old machine but it was pristine no signs of electrolytic issues. I took the PS board apart to look at it and couldn't see anything wrong. Then, admitting defeat, I reassembled the PS and battery charger boards, tightened the couple of standoffs and screws back up, and guess what, it works! Test point voltages all good again. Looking at this design, the chassis and the mechanical components such as screws and standoffs are actually an important part of the grounding throught the scope, so in my case, just removing and re-tightening a few of the PS board fasteners fixed my problem. Not unlike your issue in this video (missing screw on the main board). Thanks for the inspiration. These machines are old and antiquated, but they are beautiful pieces of engineering. Nice to not have to throw them away. I started the day intending to use this scope which hadn't used in years to troubleshoot another problem, so now I can go back to that one!
You have to make sure that all bolts are present and tight. Over the years the pcb will get contaminated creating all sorts of raised ground levels all over.
I am enjoying watching your videos and I have picked up several good tips for repairing and maintaining my old Xbox units (used as WMC extenders). Regarding eBay test equipment prices, I have a couple of points to offer: If a particular piece or family of test gear is being dumped by industry or education, prices drop rapidly and bargains can be had. A case in point now (Feb 2018) is HP logic analyzers. ATM the HP 16500 and 16700 families are bargains if you need one. Second, prices in general are all over the map from ridiculously high to reasonable to bargain; the key to getting a reasonable deal is patience. As an example I was able to obtain a two volume set of original manuals (otherwise unavailable anywhere) for a particular piece of equipment for less than one eBay vendor wanted for a single volume, including shipping. Thanks.
Watched with much interest. I had a go at fixing a defunct Tektronix multi voltage, dual trace scope some years ago. It did work when I first got it but then found problems with the PSU side. One of the power transistors had failed and the only thing I could get my hands on then was a T03 2N33055. The body of the transistor had to be modified to fit onto the scopes circuit board. Only 1 mounting nut/bolt could be used and the opposite side of the base had to be removed to get it to fit. I did get it to work however and it was good till unfortunately it got stolen along with other pieces of my equipment.
I bought this same oscope on ebay it was supposed to be working and appeared to be in the photos. I assume something was possibly jarred in shipping or something just went bad. I really like the compact size of the scope so would like to repair it. The problem is that in both channels, it will display a signal/trace but only in the three center grids of the scope. If you try to move the signal/trace up or down it mashes up the signal. I have found a tecktonix oscope repair manual and the 305 repair schematics online. The repair manual is pretty vague on problems in the vertical preamp/amp section. I did take it apart and looked for missing screws but found none. Thought you might have an idea where to start. I do have a multimeter for troubleshooting and the scope will show signals but with questionable voltage levels. By the way great video, I have watched it a couple of times to get some inspiration to fix the oscope.
Since you seem to have full horizontal deflection we can assume that your CRT voltages are good. Thus you need to check voltage supplies on the vertical amp section, and it sounds like you're already looking at that. If any of those voltages are too low the signal will saturate at that voltage level.
Nice problem shooting, this are often hard to find problems. Had it with a Tek 1S2 plugin. As soon as I reassembled the front connector it stopt working. Turned out to be a bad solderjoint. I would do an other test. Connect the chassis with a piece of wire. If that helps you are right. But if not there is some crack in a trace or bad join t that no makes contact because the screw pushing on the pcb Cute little scope,
There may very well be a bad trace interrupting or corrupting ground somewhere, and replacing the missing screw probably reintroduced ground continuity for that section of the board. But as long as it works I'm fine with this fix.
Thats such a beautiful scope!
Testing and Repair of Test Gear is why I'm Here !
Welcome
Very enjoyable... once again. And to think this video has been waiting 2 years for me 🤓 THANK YOU
Thanks for making this video - I have one of these scopes dating to the early 80's. My scope's horizontal sweep was affected - the trace all the way over on the left side of the screen. I watched your video, downloaded the schematics and took the top off the beast. Checked the PS voltages like you did and found them to be off. I'm thinking it must be bad electrolytic capacitors in such an old machine but it was pristine no signs of electrolytic issues. I took the PS board apart to look at it and couldn't see anything wrong. Then, admitting defeat, I reassembled the PS and battery charger boards, tightened the couple of standoffs and screws back up, and guess what, it works! Test point voltages all good again. Looking at this design, the chassis and the mechanical components such as screws and standoffs are actually an important part of the grounding throught the scope, so in my case, just removing and re-tightening a few of the PS board fasteners fixed my problem. Not unlike your issue in this video (missing screw on the main board). Thanks for the inspiration. These machines are old and antiquated, but they are beautiful pieces of engineering. Nice to not have to throw them away. I started the day intending to use this scope which hadn't used in years to troubleshoot another problem, so now I can go back to that one!
You have to make sure that all bolts are present and tight. Over the years the pcb will get contaminated creating all sorts of raised ground levels all over.
Good eye, good hand. Good job!
I love the Classic Repairs..
Ohh yea, man made faults are always the hardest to find. Nice job, keep em coming..
What a crazy fix. Nicely found.
I am enjoying watching your videos and I have picked up several good tips for repairing and maintaining my old Xbox units (used as WMC extenders). Regarding eBay test equipment prices, I have a couple of points to offer: If a particular piece or family of test gear is being dumped by industry or education, prices drop rapidly and bargains can be had. A case in point now (Feb 2018) is HP logic analyzers. ATM the HP 16500 and 16700 families are bargains if you need one. Second, prices in general are all over the map from ridiculously high to reasonable to bargain; the key to getting a reasonable deal is patience. As an example I was able to obtain a two volume set of original manuals (otherwise unavailable anywhere) for a particular piece of equipment for less than one eBay vendor wanted for a single volume, including shipping. Thanks.
Watched with much interest. I had a go at fixing a defunct Tektronix multi voltage, dual trace scope some years ago. It did work when I first got it but then found problems with the PSU side. One of the power transistors had failed and the only thing I could get my hands on then was a T03 2N33055. The body of the transistor had to be modified to fit onto the scopes circuit board. Only 1 mounting nut/bolt could be used and the opposite side of the base had to be removed to get it to fit. I did get it to work however and it was good till unfortunately it got stolen along with other pieces of my equipment.
She's a beauty!
First visit to your channel and really enjoyed it. About to hit the subscribe button so keep em coming.
Great video. Thanks!!!
Nice catch.
Nice neat scope. I want one.
I bought this same oscope on ebay it was supposed to be working and appeared to be in the photos. I assume something was possibly jarred in shipping or something just went bad. I really like the compact size of the scope so would like to repair it. The problem is that in both channels, it will display a signal/trace but only in the three center grids of the scope. If you try to move the signal/trace up or down it mashes up the signal. I have found a tecktonix oscope repair manual and the 305 repair schematics online. The repair manual is pretty vague on problems in the vertical preamp/amp section. I did take it apart and looked for missing screws but found none. Thought you might have an idea where to start. I do have a multimeter for troubleshooting and the scope will show signals but with questionable voltage levels. By the way great video, I have watched it a couple of times to get some inspiration to fix the oscope.
Since you seem to have full horizontal deflection we can assume that your CRT voltages are good. Thus you need to check voltage supplies on the vertical amp section, and it sounds like you're already looking at that. If any of those voltages are too low the signal will saturate at that voltage level.
@@artifactelectronics Thank you for your help I found that pin P280 was disconnected on the vertical amplifier. The scope is now working correctly.
OMG, OMG, WHAT A FIND!
Enjoyed !!! GLX/73's
First rule of troubleshooting is to check your main voltages.
Nice problem shooting, this are often hard to find problems. Had it with a Tek 1S2 plugin. As soon as I reassembled the front connector it stopt working. Turned out to be a bad solderjoint.
I would do an other test. Connect the chassis with a piece of wire. If that helps you are right. But if not there is some crack in a trace or bad join t that no makes contact because the screw pushing on the pcb
Cute little scope,
There may very well be a bad trace interrupting or corrupting ground somewhere, and replacing the missing screw probably reintroduced ground continuity for that section of the board. But as long as it works I'm fine with this fix.
Interesting post, thanks
How much is it worth
In case you can not find that hinge cover, consider (having it made by) 3D-printing.
I've considered that, just haven't been able to bribe my friends yet.
hi.ijust want to know if i could send some pictures with a fault hm408 signal,and if yes, let me know how. thancks a lot
Nice toy but its only a 5MHZ scope
Works well for audio though
hope you then gave the seller an additional cheque , at least a little extra..
I don't understand why the seller is entitled to more money. He didn't take the chance and spend the time fixing it. Please explain this idea to me.
So I wonder how much that screw cost the seller??
:-)
That's crazy..
Now I have scope envy. Though I have no use for them, I am browsing the offers on eBay. Thanks a lot - not!!!
Here's what you do: Get an analog scope and a scope clock (~$30). It will display an animated analog clock face on your scope - geek heaven!