Just before I purchased mine I found a scope on Craigslist for 200.00. I think it was a Tektronix - about 20 or 50 Mhz - 4 inch screen - no color. He wouldn't budge on the price. I almost bought it but I shopped around and found this one for just a few dollars more - brand new. Better deal!

I heard that Hantek found that the mod was so easy and everyone was doing it that they just sell the 200 Mhz in a 70 Mhz case. Seems they had to modify the 200 down to 70 so they just quit modifying them. I think mine is a 200 Mhz but I don't know. 70 Mhz or 200 Mhz - it works fine for me.

I wasn't interested in connecting my scope to USB either. If I didn't have this problem I doubt if I would try it but I wonder if it would allow me to adjust the controls. Might give some insight on where the problem lies. I'm going to give it a try when I have time.

I've seen several videos and photos of the inside of this scope but haven't seen anything with the front removed. I hate to dig into it if the supplier or Hantek can repair it. With my luck I'll just make things worse.

Thanks

Bob

I got the socket changed today. Installed another U9 and still got the same results. Solid on , on the first try - then it booted. I let it set for a few minutes and tried again. This time it took 4 tries before it booted.

Quench, did you ever have a MPU that you just couldn't fix? I hate to give up but I think it's got us beat.

Do you think the U7 or U11 sockets are bad?

Thanks

Bob

Well at least something seems to be going right. The oscilloscope - I been in contact with the supplier. They said one year warranty. I told the Hantek says 3 year warranty. Basically they said I should contact Hantek. BS - I didn't buy it from Hantek. So I contacted Amazon. I ended up on the phone with them. They also said I should send it back to Hantek. I told them I bought it from Amazon - not Hantek. After a bunch of bitching and talking to the supervisor he said they will replace it - it should be here Saturday. We'll see.

Bob

Mark, by the way I tried to connect the scope to my laptop. I downloaded TTScope but I don't think I got the right drivers for the scope. Hantek is pretty vague on their drivers. Me and computer drivers never did get along.

Thanks

Bob

Advice from two of the most respected and talented people I know. I listen to everything you say. You two guys have taught me a lot. It’s little surprise that your routine is basically the same.

I don’t mind putting the work and time into this board (even though it’s just a spare). I don’t have much else to do anyway. The board didn’t look to be too corroded when I got it (see photo below) but I cleaned and polished everywhere it looked questionable. I remember seeing a board Andrew did years ago where he removed about 75 percent of the components and rebuilt the entire board. That impressed me.

The problem I’m having (as did the previous owner) is the solder pads keep falling off when I remove anything. Especially when there’s no trace connected. That requires soldering on the top or stitching. It seems that the glue used to adhere the pads to the board has dried out. I've noticed several missing pads from the previous owner.

Since the board won’t boot on the first try maybe is has to do with the ROMs. Next I’ll try swapping the ROMs. If that don’t do it I’ll attack the IC sockets.

Thank you all for the help.

Bob

IMG_3801 (resized).JPG

Thanks Mark, I have seen that thread before. barakandl started that thread years ago.

I’d be very cautious about using a strong acid on anything. Years ago I remodeled apartments for a local village. A maintenance worker a couple of buildings down was cleaning a clogged sink. He poured in some really strong acid drain cleaner and it blew up out of the drain. Burned his hand and arm pretty bad. The stuff he was using was for commercial use only - I'm sure it wasn't what Andrew is using.

I’m always careful using any kind of acid.

Bob

I guess my description isn't clear. It's not just the solder is missing but the entire pad. Nothing left to solder to.

08 (resized).jpg

I know that was part of the problem. See photo. It's difficult to heat both sides at once. When i did the Stern board I heated the pins on the back and most of the headers just came out. Most of the Bally headers didn't come out so easy and some of the pads stuck to the headers. Same desoldering tool - same temperature - different results.

I assure you my de-soldering skills and tools are average at best. But I try to be careful and use heat sparingly. Just when I work on a board with no loss of pads then I get a board like this Bally and start losing many pads I get concerned. I lost 4 or 5 header pads but the previous owner lost even more removing components. When I worked on the U9 I only lost if two half pads. And that took me two days. Cutting the components out and removing the legs still leaves solder inside the through hole. The only way to get it out is to suck it out or drill it out.
I doubt I’ll ever get the skill most of you have obtained but it’s not for lack of trying. I'm thinking it takes a special skill like playing a piano.

Thanks for the lessons.

Bob

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When I remove components I always clean the pads with very fine sandpaper - Solder attached or bare copper pads I give them a good cleaning.

When I said suck it out I meant using the desoldering tool. Adding more solder just seems counterproductive but I'm learning it usually helps.

Today was a much better day. I received my new oscilloscope - Way to go Amazon!. I didn't get much time to mess with it but it seems to work great. I only used it to set the probe and all the controls worked.

Then I changed ROMs in the Bally board. I connected it and it booted first try. I let it set and tried again (several times) and it booted first time everytime. Looks like the ROMs were bad. Later I'll connect the scope to be sure I have activity on all the pins. I don't know what ROMs I'm using because I got them from my parts box. But it's just a spare board anyway.

The only bad news is I broke one of the legs off one of the Stern ROMs - it stuck in the IC socket. Looks like I need to replace the U2 socket on the Stern board.

Since I have a new scope I plan on taking the old one apart to see if I can fix it.

More stuff to do.

Bob

Quench, Going back to post 20 - now my scope is working. Yellow probe on VR1 and blue on CR5. Scan is from the Bally.

Is this what we're looking for?

Bob

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Only about half of the leg broke off in the socket. I got it out but the socket pin is bent and probably won't make good contact.

Someone suggested a long time ago to insert the chip into a machine pin socket and solder the broken leg to the socket. Since I had half the leg still in place, that worked pretty good.

Please don't say that. I hate the thought of working on that Bally board. Unlike the Stern where I just removed the socket and didn't lose any pads. I just have to clean it up and remove the solder from the holes.

Which reminds me, how do you remove the left over solder from the thru-holes? Desoldering gun?

I suspect the grounding issue. The ground wires on the probes are very short. So I connect a jumper wire to the TP4 - then connect both probes to the jumper wire. That's the best solution I could come up with.

It wouldn't be easy to connect the probe to pin 40 without just holding it there. It would be easier to connect the probe to something and have my hands free. Would connecting to R139 do the same thing?

I'll play with it tomorrow.

Thanks

Bob

Maybe I should try the Bally ROMs in the Stern board and see if I get the same problem. I'll try that after I get the Stern board back together.

Bob

By the way - Amazon didn't ask for the old oscilloscope to be returned. Maybe after I get these MPUs sorted out I may dig into the old scope. That should be interesting. I'll keep you posted.

Quench, did you ever think about becoming a brain surgeon?

Most of the day was spent cleaning up the Stern board to install the new socket at U2. Once that was done I installed the ROMs and tested - OK. Then I put the old Bally ROMs in and tested. Same results as I was getting on the Bally - solid on for the first few times then it booted. I'm sure now those ROMs were the problem.

Then time for the fun stuff. I connected the yellow probe to R139 and blue to TP5. The first scan is the Bally - 4.00 ms and 5V per division. Second scan is Stern. I couldn't get the top of the blue trace in at 5V so I changed it to 10V per division.

I think this is what we were looking for. Looks like the 5V is steady before the R139 kicks in. My question is why does the 5V look so high? Looks like the yellow trace is topped out at 5V but the blue trace looks like 15 volts on the Bally and over 30 volts on the Stern. I would have thought both the yellow and the blue would top out at 5V.

This stuff is so interesting.

Thanks

Bob

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stern 02 (resized).jpg

I remember reading this part of PinWiki years ago –

” The purpose of the reset circuit is to ensure the +5 vdc is stable before allowing the system to start. At startup, the reset signal is held low via pull-down resistor R139 until the +12 vdc line rises above the zener diode VR1's value (8.2 or 9.1 volts depending on your board). At this time, the input voltage threshold for the +5 regulator on the solenoid driver board has been met with some headroom. Q1 starts conducting, turning on Q5, which provides the actual reset signal. All of this happens in approximately 50 milliseconds.”

Today (especially with the oscilloscope demonstration above) That’s beginning to make sense.

PinWiki says it happens in approximately 50 milliseconds. Looking at my scope it happens in 8 milliseconds. Am I not seeing something?

You guys have taught me a lot.

Thanks

Bob

My hat’s off to you guys that put that PinWiki together. That had to be a heck of a lot of work and it’s very educational and well done. I often go back and re-read some of the information that didn’t make sense years ago.

I remember seeing an oscilloscope for the first time (must have been in the 60’s). Small round green tube. I didn’t have a clue what I was looking at but was amazed that I was seeing electricity.

As far as the 50 milliseconds is concerned – looking back at the Bally scan – if the timing starts at the beginning of the trace then the timing is closer to 32 milliseconds. It’s 8 milliseconds from the time the 12 volts starts and the 5 volts stabilize.

I noticed the glitch too. There’s also a small glitch at the top of the Stern scan. I thought that was just caused from the on/off switch on the power supply bouncing.

Quench, I think your right that the probes aren’t set correct. I did check the probes themselves and they are both set on 1X. But there is a menu on the scope that also must be set. I’m pretty sure the menu for the yellow probe (channel 1) is set to 1X but not sure about the blue channel. I’ll have to check. Too many menus and settings. I might do that test again – it was fun and interesting.

You’re right the Stern board said Nugent – The Bally board said Evel Knievel. I don’t know what’s in the Bally now but they work. Both boards are spares so if I use them in a game the ROMs will probably need to be changed anyway.

Thanks

Bob

Another experiment. First I checked the probe menu - you were correct. The scope menu probe for channel 2 was set at 10X. I gotta be more careful about that. This scan shows more reasonable levels.

Forget my theory about the time starting 32 milliseconds earlier. I think that's just when the scope starts getting the sample. This scan shows much longer. I think the 8 - 10 milliseconds is the correct time.

Also my theory about the switch bouncing is probably wrong. This scan don't show that glitch. Don't know what caused that on the other test.

You are making me a better oscilloscope user. The first scan tonight looked very fuzzy. I adjusted my grounds and the next scan was much better. Who knows, I may learn to use this thing after all.

Next I'll dig into the old scope.

Thanks

Bob

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I tore into the old scope tonight. It's definitely not like any MPU I've ever worked on. I may be way out of my league - especially without a schematic. I looked it over for any damaged or broken traces or wires. All looks OK. But this is what I've found so far.

Six of the eight pots have a push-in switch. (see photos below) They are controlled through A and B. It seems that all the A's are common to all switches. The C and D connections are just the pot housing - they are all common and grounded.

It looks like all the G terminals are all connected but not the E's or F's. I haven't traced them down yet. How does a three terminal potentiometer work? (I understand two terminals but not three). I'm thinking E - F - and G are going to the potentiometer. I'm thinking if none of the pots are working the problem may be with the G terminal.

I haven't applied any power yet. I'm a little leary of turning it on with all it's guts laying on the bench. But I guess the next step would be to see if the G's get any power.

Maybe tomorrow I'll get my confidence up.

Bob

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IMG_3959a (resized).jpg

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I may have found a schematic

https://www.mikrocontroller.net/articles/Datei:Hantek_Tekway_DSO_MSO_hw1007.pdf

See page 8.

Now if I just knew what I was looking at.

Still discovering more - what I been calling a potentiometer is actually an encoder. They are driven by the decoder chips. (I think I'm calling them by the right names). If this is true then the E terminals are also tied together. The E 's and G 's all go to common terminals on the chip. All the F 's go to separate terminals.

PLEASE don't be a bad chip. I've never worked on surface mounted components.

I'll get into it more tomorrow. Now I gotta get some rest before my brain explodes.

If you have any comments, suggestions or advice please let me know.

Thanks

Bob

I don't think this scope has a "factory" reset. You can reset the setup to the previous setup. I've done that several times and it didn't make a difference. Because all the controls are not working I'm thinking it's a power or connection problem.

That's what I'm working on.

I've looked at that ribbon cable but just didn't know how to disconnect it. It looks fragile.

If I get time tonight I'll dig into it more - I think that schematic might be a big help.

Bob

Thanks Mark, I didn't know that for sure. When I hit default setup the menu says "cancel". That doesn't seem to change anything - maybe because I already have factory settings setup?

I'm just learning to use the "help" button - nice feature.

Bob

I had a little shop time tonight. First I disconnected the ribbon cable - thanks Quench. I would have never figured it out on my own. Having the board not connected makes it much easier to work on.

I traced more connections tonight and made notes as I went. Page 8 of the schematic seems to be spot on - once you figure out what's what on the schematic. To me it's very hard to understand. Also those SMD's are difficult to probe.

Also I need to learn how these encoders / decoders work. Looks like the two outside connectors of the potentiometers are connected to U2 but the center connector connects to another chip (U3). Why? How does that work? Strange.

I also traced the hot lead (?) back to the ribbon connector. So far all the connections are good.

I'm a little reluctant to add power and check traces - those SMD's are so small - It would be easy to touch 2 pins with the probe. Maybe I need a smaller probe.

Thank you

Bob

schematic 1 (resized).JPG

Why didn't I see that - I know when it says "2A" there should be a "2B". I guess I just didn't look very well. One of the things I wanted to know was the voltage for U2 and where is comes from. Looks like 3.3 VDC at pin 16 - and pin 16 on U4 which is for the switches - and they all seem to work. If I have continuity from pins 16 on U2, U3, and U4 I would think the voltage is present on all 3 chips.

Also it looks like 3.3 comes in on pins 4 and 5 on the ribbon cable.

I'll do more testing tonight.

Thanks

Bob

I just checked and I have continuity on pin 16 on all 4 chips - plus continuity back to ribbon cable pins 4 and 5. If the switches work (U4) then I assume I have power on all chips.

More investigating to do.

It's looking like everything on the board is checking out fine. I'm thinking the weak point is the ribbon cable. I guess I should concentrate on that.

Bob