Electronics > Repair

Power supply issue on Tektronix AWG410

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Hello everyone..  First post here at EEVblog forums.  I'm looking forward to getting more involved in this community.

I recently picked up a very reasonably priced Tektronix AWG410 with what appears to be a power supply issue.  (It was sold as for parts/repair, so no surprises) Many of the key voltages on the power supply unit as described in the AWG410 service manual are not preset, so I can only assume that there is a relatively fundamental issue that needs to be tracked down in the power supply or related to it. I can hear a relay activate when the main switch on the rear panel is turned on, but the front-panel power button has no effect.

So far I haven't found anything obvious in the power supply. (Checking for physical evidence like blown caps, basic in-circuit diode/transistor checks, etc...) What I could really use is a schematic for this power supply, but I'm getting  impression after some Google searching that this might be hard to come by. I believe this PS was manufactured by Fuji Microelectronics, part number FH0410. The Tektronix part number is 630-A006-00. Does anyone have any idea if a schematic can be tracked down for this unit?  If not, is there any experience base with these power supplies that might suggest common failure mechanisms to look for?


I forgot to include in my original post a question about the front panel ON/STBY button. Presumably, I should include the possibility that there is a fault in the ON/STBY button or its support circuitry. There service manual doesn't appear to provide any advice for specifically troubleshooting this path to the power supply. I assume that the PS must supply a standby voltage for the ON/STBY button function.  Does anyone know how to check this out in more detail?

BTW -- I misspoke slightly in my original post.  There is one meaningful voltage present on J3 connecter from the PS to the "A10 Connector" board.  Pin 16 measures around +4.2V.  The service manual indicates that it should be +5V.  Could this be the standby supply?

I also noticed that the J3 connector includes a "Remote On" at pin 9.  Is this for the ON/STBY function?  If yes, is there way to bypass the ON/STBY circuit at this connector to see if the power supply output will ramp up independent of the standby control logic? I don't know if it needs a jumper to ground, a voltage signal, or something else. (Again... I could probably answer some of these questions for myself if I actually had a schematic.  -alas- )

I have a AW615 with a shorted main board. It also doesn't turn on like your unit. The only way I can turn it on is by removing the J1 J2 J4 connector and leaving the J3 connected. If this still not turn your unit on there is a problem with the power supply.

Is this your power supply? (Found these pics on Ebay). From the label on the picture I would say the 4.2V is not to be considered a normal situation.

Lets try answering the question if the issue is with the power supply or somewhere else. Unplug everything except mains and check if that standby voltage is normal now.
If you experiment connecting the remote-on pin to ground or elsewhere then make sure to limit the potential current using a resistor.

Do you have a means to power up the rest of the electronics using lab supplies? It seems you need 3 different voltages.

Careful poking in that thing, many electrons jumping around.

Swake -- Yes...  That looks like the correct power supply unit.

I agree that 4.2V doesn't sound normal. (And to be clear, I don't really know if that's the standby rail either... It was more of a question on my part since it was the only connector voltage which seemed to be present and meaningful.)

So... I've got the power supply completely removed.  The boards are separated from the aluminum PS chassis box also so I can have an easier time following tracing and probing. When I provide power to the PS, there doesn't appear to be any improvement.  Pin 16 on J3 still reads low at 4.2V.  I also don't see any other correct voltages show up on J1, J2, J3, or J4.  Regarding your question about lab supplies, I only have a three-output bench supply at the moment...  (One is fixed at 5V, the other two are adjustable)  This isn't sufficient to power the full AWG410...  I see 7 different voltages on the J1-J4connectors, based on a connector pinout in the service manual.  (+12V, +5V, -5V, +8V, -8V, -2V, +3.3V)

I'll attach a quick photo to this post for reference. (I can share more as needed) The top board disconnects from vertical board thanks to a set of three connectors that can be separated.

Here are some of my initial observations:

* The mains plug feeds the top board which I can separate. Roughly half of this board appears to handle fundamental rectification and heavily filtering of the mains power. When I power this board by itself I can measure 164.5V DC on the output end.
* The other half of this board include 4 transformers and support components which I'm guessing make up four separate switch mode supplies.
* The bottom board includes two more transformers and a lot of inductors and capacitors.  Perhaps two additional switch mode supplies?  (That's six total at this point...  It's possible that one or more of these transformers have multi-tap secondaries -- I haven't sorted that out yet.)
* The horizontal board appears to be mostly full of voltage comparators -- based on looking up the datasheets for numbers found on the ICs. There is a 12V regulator IC on this board which is working.  I can measure 12V on it's output and many of the comparator ICs appear to be getting this 12V supply also.
* This three-board arrangement is gets more difficult to probe when they are all connected together.  I can get to the backside traces, of course, but it's hard to locate the components on buried on the inside to sort out what I'm looking at. I can't tell yet if each switch mode supply has fundamental dependencies to a neighbor board via the connectors. I could try to test the top board by itself, for example, but I'm not certain if I would be missing key portions of the circuits when it's disconnected.
Alright...  where to start?   :-\


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