 MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA |
to neonhomer
Re: Tektronix 485 - no power upPull them all off. The big HV lead goes to the tube anode, you can leave that in. |
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 neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
Haven't forgotten. Just don't feel like opening this thing back up right now. Will probably open back up after the kids go to bed in about 45 min or so. |
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| neonhomer |
Oooookay... Pulled the three connectors that go from the xfmr board to the crt. Nothing. Same thing.
Walked through some of the tests on 4-7. Nothing to note.
I think I have reached the limit of my equipment. I hate to have to send this to a shop, as I know it will be a few hundred $$$ to get it fixed. |
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 drjim
MVM
join:2000-06-13
Long Beach, CA |
drjim
MVM
2011-Mar-3 12:23 am
Try and find a local ham radio club. Most of the old guys there (like me!) probably have an oscilloscope, and might be willing to help you track down the problem. |
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to neonhomer
said by neonhomer:I think I have reached the limit of my equipment. I hate to have to send this to a shop, as I know it will be a few hundred $$$ to get it fixed. Yeah you can hunt a working unit if you are patient. I have a 2232 that I got for $100 *shipped*. |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
I found a working Hitachi V1100A on Craigslist for $100.....
drjim - I could always ship this thing to you and let you play with it... LOL.... |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA
1 edit |
to neonhomer
said by neonhomer:+15 : Maybe 1-2v
+5 : 0.2
-5 : -0.2
-15 : -0.2 to -2.4
+59.4 : 0 to 11
-5.5 : -0.5
+120 : 3 to 35
+9 : 0
Assuming you're going to get a scope, in the meantime you could do further checks, based on your quoted post. If there's a short somewhere preventing the protection circuit to allow inverter operation, where is it most likely to be? I think your post might answer this: something on the 9V rail is shorted. edit: noticed you haven't checked the -9v line. You might want to check the voltage there, and while you're at it, see how much resistance there is between +9 and -9 lines (with power off). |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
Resistance between -9 and +9 points on the board is about 127ohm.
Voltage reading at +9 is between 0.08 to 1.2v
Voltage reading at -9 is between 0.08 to -1.4v
These and all other readings are between GND points on the board and the individual test points. |
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| neonhomer |
Something else. When you disconnect P1960, the unit doesn't cycle. From what I read, P1960 feeds the transformer board.
I just have a bad feeling the transformer board is toast.
I removed the "U" comb and powered the unit up. A visible flash can be seen under the board. The "U" comb is the feed from the power supply board to the transformer board.
U3 feeds power to the 3KV circuit. U1 IS for the +59.4 circuit, U2 is for +120V, T4 & T2 are the +15 & -15, respectively.
I need to find someone within driving distance of Daytona Beach that I can take this thing to have it troubleshooted more than I can do.
Even if I buy a working scope, it's still going to bug me until this scope works. |
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 SmokChsrWho let the magic smoke out?
Premium Member
join:2006-03-17
Saint Augustine, FL |
SmokChsr
Premium Member
2011-Mar-3 9:42 pm
Darn Neo, I didn't realize you were so close.. If you can wait a couple days you can run it up to the shop and I'll take a look at it with you. I'm swamped right now, (building 2 radio studios, and just had a surprise translator show up today that I had to get on the air.) but give me a little breathing room then I can help. That is if you feel like driving up to St. Aug one evening. |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA |
to neonhomer
said by neonhomer:Something else. When you disconnect P1960, the unit doesn't cycle. From what I read, P1960 feeds the transformer board.
I just have a bad feeling the transformer board is toast.
I removed the "U" comb and powered the unit up. A visible flash can be seen under the board. The "U" comb is the feed from the power supply board to the transformer board.
Are you talking about the transformer board? And are you talking about a single flash of light? If so, it's worth taking out the board and examining it. U3 feeds power to the 3KV circuit. U1 IS for the +59.4 circuit, U2 is for +120V, T4 & T2 are the +15 & -15, respectively.
I need to find someone within driving distance of Daytona Beach that I can take this thing to have it troubleshooted more than I can do.
Even if I buy a working scope, it's still going to bug me until this scope works.
If you can find someone, that would be good for you. This pic shows what you're talking about. You were following "Troubleshooting the Power Supply" on pg 4-7. You're going in the right direction. |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
to SmokChsr
said by SmokChsr:That is if you feel like driving up to St. Aug one evening.
Yeah. I wouldn't mind. Especially if I can get this thing running. mdoc - Combs "S, T, U, V, & W" on the Power Supply board all go to the transformer board. On pg 4-7, it says to detect a short in the -2950V supply, to pull the "U" comb, bend out pin 3, and put it back in. I tried it w/ the entire U comb out, and the "flash" was about the same speed as the "click click click". |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA |
to SmokChsr
said by SmokChsr:Darn Neo, I didn't realize you were so close.. If you can wait a couple days you can run it up to the shop and I'll take a look at it with you. Happy troubleshooting!... my parents live in Wesley Chapel. |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
What a royal PITA! I managed to weasel the transformer board out of the unit. First thing I noticed is there is a burn mark between pins U3 & U4. U4 is ground.
It looks like U3 is hooked to one of the windings on T1960. One end goes to the 3kv P-P CRT circuit. This looks like it is connected to the 59.4v line, and then continues through a 39ohm and a 470 ohm resistor, then to a diode. This continues to the Balance Node on U1910. Off of this there is 7 resistors for numerous voltages, and a capacitor to ground.
Well, guess it's time to check out this transformer board, and then either leave it apart or put it back in if i don't find anything. |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA
1 edit |
Mdoc
Premium Member
2011-Mar-4 11:07 pm
Congratulations, you've found at least one short, or a burn mark. Question is why did U3 short to ground (U4)? Examine carefully. If there is no foreign matter there, it may be necessary to take measures to insulate U3 from U4 to prevent arcing. But this may not be all to find. You're correct in your circuit assessment. 59.4v is what is feeding the coil at T1960 to produce 3k volts from it. The 3kv then goes to the red arrow indicated above (diagram 13), and note that this area is still part of the transformer board. The area next to the CRT is also part of the transformer board. |
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Mdoc
2 edits |
to neonhomer
Also check out the caps and diodes for shorts at the x6 multiplier (red arrow above). It looks like it's on the transformer board, according to diagram 13. edit: yes, it's on the transformer board. I just noticed that U1600 is a self-contained unit, there isn't a way to test the diodes/caps individually. I'm not sure how you could test it other than with HV probe during operation. But first 3kv must be present. |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
Yeah, the X6 multiplier is a sealed unit.
I did check all the resistors on the board for shorts or opens. They all seemed fine.
I put it back together last night, and turned it on. Click click click click.... Well, I forgot about the scope being on while I was doing something else on my computer. After a few seconds, I noticed the unit was doing something weird.... "click click click .....click click click click" It would click a few times, pause for like half a click, and then keep doing it more.... every once in a while it would pause for a 1/2 second.
I spent a half hour digging on my "flyback" tool (long narrow flat head screwdriver, with a 12" jumper soldered to it halfway down the shaft) last night to disconnect the HV lead. All for not... there was no charge on it. |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA
1 edit |
Mdoc
Premium Member
2011-Mar-5 12:21 pm
said by neonhomer:I spent a half hour digging on my "flyback" tool (long narrow flat head screwdriver, with a 12" jumper soldered to it halfway down the shaft) last night to disconnect the HV lead. All for not... there was no charge on it.
Heh. No charge? I would think you should get something even though the protection circuit is not letting the inverter get fully turned on. You checked the resistors, did you check the diodes, too? Check those (not the multiplier, the discrete ones like CR1601 & CR1603). If so, then... well, let's back-track a bit. You did remove the U comb and the clicking never stopped, right? Time to move on. Try removing T2,T3,T4 (leave T1 and T5 in), check for clicks, and then re-install them and remove the S comb (including T1 link). Did the clicking stop at any time? If no go, then isolate A11 board by removing DD1, DD3, DD5, BB2, BB5 links. Any change in the clicking? If still no change, then we need to go somewhere else. |
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to neonhomer
said by neonhomer:What a royal PITA! I managed to weasel the transformer board out of the unit. First thing I noticed is there is a burn mark between pins U3 & U4. U4 is ground.
It looks like U3 is hooked to one of the windings on T1960. One end goes to the 3kv P-P CRT circuit. This looks like it is connected to the 59.4v line, and then continues through a 39ohm and a 470 ohm resistor, then to a diode. This continues to the Balance Node on U1910. Off of this there is 7 resistors for numerous voltages, and a capacitor to ground.
Well, guess it's time to check out this transformer board, and then either leave it apart or put it back in if i don't find anything.
you need to grind off the burned area until you get to clean pc board, that carbon tracking between u3 and u4 at 3KV is like a dead short to it!!. |
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SmokChsrWho let the magic smoke out?
Premium Member
join:2006-03-17
Saint Augustine, FL |
to neonhomer
If it's flashing HV to ground, Either were getting too much HV or (more likely) something (like a bug) compromised the resistance in that area and caused some carbon tracks.
That calls for a good cleaning and visual inspection and perhaps some HV putty (anyone remember that stuff) or some Krylon Electronic clear after all the carbon tracks are cleaned up. |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
Thing is, it only did that when the U comb was removed.
I didn't notice any continuity between those two pins.
Regardless, I guess I will pull the xfmr board back out and try to clean that area of the board up. I dunno what I can get in there with, maybe a Dremel and a wire wheel on low speed, or a small screwdriver to scrape away the carbon... |
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SmokChsrWho let the magic smoke out?
Premium Member
join:2006-03-17
Saint Augustine, FL |
SmokChsr
Premium Member
2011-Mar-7 12:14 am
said by neonhomer:I didn't notice any continuity between those two pins.
Not uncommon, think of it this way, the few hundred or so millivolts that your ohm meter uses, don't always find the same current paths that a 3,000 volt power supply will. |
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to neonhomer
said by neonhomer:Thing is, it only did that when the U comb was removed.
I didn't notice any continuity between those two pins.
Regardless, I guess I will pull the xfmr board back out and try to clean that area of the board up. I dunno what I can get in there with, maybe a Dremel and a wire wheel on low speed, or a small screwdriver to scrape away the carbon...
the manual says to pull the u comb, bend pin 3 up, then PUT THE U COMB BACK IN. there's a difference from leaving it OUT!. you ARE getting HV!. but the multiplier may be shorted, disconnect that, and see if the clicking stops. |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA
1 edit |
to neonhomer
said by neonhomer:Thing is, it only did that when the U comb was removed.
Ah, so it was because the U comb was removed that you saw the flash. OK. In the last schematic pic I posted, there's a blue dashed arrow. It's pointing at the resistor that connects to the x6 multiplier. Remove it and test for no clicks. (With the U comb in) |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
Okay.. will do and post results later.... |
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| neonhomer |
neonhomer
Premium Member
2011-Mar-13 12:54 pm
Just a brief update - Still haven't done anything else with the scope. Just haven't felt like dragging it out. |
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| neonhomer |
neonhomer
Premium Member
2011-Mar-13 10:15 pm
Okay.... R1602.... problem is this resistor is on the transformer board. So I have to pull the xfmr board, remove this resistor, and then put the board back and then power up the unit.
Is there a way to do this w/o pulling the xfmr board? |
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drjim
MVM
join:2000-06-13
Long Beach, CA |
drjim
MVM
2011-Mar-13 11:14 pm
How long are the leads on it? You could always clip one lead, lift it, and then solder back to the stub in the board. |
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neonhomerDearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL |
neonhomer
Premium Member
2011-Mar-13 11:23 pm
No. The resistor is located on the xfmr board, and it is under a cover. So it looks like pulling the xfmr board is the only way. Ugh...
I kinda wish I could have this thing to someone and have them fix it. Unfortunately, I don't have that kind of money... |
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MdocEhh... munch munch... what's up, Doc?
Premium Member
join:2007-03-27
Sterling, VA
3 edits |
to neonhomer
said by neonhomer:Okay.... R1602.... problem is this resistor is on the transformer board. So I have to pull the xfmr board, remove this resistor, and then put the board back and then power up the unit.
Is there a way to do this w/o pulling the xfmr board?
Yes, you can do another way, but this will isolate what I don't want isolated: the circuitry for the CRT. You can just remove pin 3 of U comb and put the comb back in, and then test for no clicks. After this, re-insert pin 3. Remove P1960 (diagram 15). The result should hopefully be that no clicks are heard. If still clicking, the problem is localized to before the P1960. We'll get to that if we get to this bridge. Re-insert P1960 and do either one of these 2 approaches: 1) Remove everything in the circle (right side of pic above) from the A13 power board and test for no clicks. If no clicks, then re-attach each power line until you hear clicking. When that happens, you've narrowed down the culprit considerably, and that's where you should look much closely for problems. Or 2) Remove power lines singly and test as you go. The approach is similar to above, but inverted. What you're looking for is a condition where there are no clicks. That's a condition where that part of the circuitry can be ruled out. I hope the removal of P1960 demonstrates my thinking: that this stops the clicking. If it does not stop, either I'm barking up the wrong tree or my approach is wrong. |
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