EEVblog #512 - Rigol DP832 Bad Design Investigation

[Dino KL0S]

I went ahead when updating my bench suite with Rigol gear and got the DP832A which has the multi-color channel display. Even at full brightness the third channel which is colored some kind of magenta is very difficult to see.  I've asked the Rigol guys several times to consider adding an option to the 832A firmware that allows you to select the same green color as you get with the DP832 be applied to the three channels on the A model as that color is easier to see. In retrospect I often think buying the 832 with the resolution upgrade would actually have been better! Seems like a simple option to create but things work slowly.

I do have to say that they do listen and make changes albeit slowly. For example, my DSA1030A-TG did not have the VSWR software included in the firmware much to my chagrin after purchase forcing me to make and record manual measurements with the directional coupler.  Rigol's latest spectrum analyzer firmware added that capability!

[neslekkim]

what if you change contrast and brightness a bit?
I also was considering the 832 and getting the options separately, but it would be more expensive than the 832a (unless I hacked it ofcourse)

But one thing they didn't fix after all this years.. the fan.. very very noisy even when the unit is idle...

[Dino KL0S]

I've tried all the different combinations of brightness and contrast and the purple channel simply isn't very readable, at least to me. Maybe it's a hardware thing.

[Stupid Beard]

But one thing they didn't fix after all this years.. the fan.. very very noisy even when the unit is idle...

The fan drives me nuts. I haven't replaced it because I didn't want to void my warranty, but I'm starting to change my mind on that.

[tkarlmann]

I am hoping to purchase a DP832 in the next couple of months.  Dave's reply stated that Rigol's "fix" for this problem was to increase the size of the heat sink on that crusty 5v regulator.  Ok.  My Question:  Has anyone measured the Input Voltage to that 5v regulator AFTER Rigol's "fix"?  When Dave stated that the input voltage on the unit he tested was 12v DC, I thought that sounded high for a 5v output @ 700mA.  I would think 8-9v DC would be sufficient for the 5v regulator (need to check the data sheet for input/output required differential).  ANY reduction in that "12v" input would, of course. dramatically reduce the power dissipation in that 5v regulator.  Does anyone have a "Fixed" DP832 they could check the level of the input voltage to that 5v Regulator?  My suspicion is that Rigol may have lowered that voltage. 

[Sparky]

I am hoping to purchase a DP832 in the next couple of months.  Dave's reply stated that Rigol's "fix" for this problem was to increase the size of the heat sink on that crusty 5v regulator.  Ok.  My Question:  Has anyone measured the Input Voltage to that 5v regulator AFTER Rigol's "fix"?  When Dave stated that the input voltage on the unit he tested was 12v DC, I thought that sounded high for a 5v output @ 700mA.  I would think 8-9v DC would be sufficient for the 5v regulator (need to check the data sheet for input/output required differential).  ANY reduction in that "12v" input would, of course. dramatically reduce the power dissipation in that 5v regulator.  Does anyone have a "Fixed" DP832 they could check the level of the input voltage to that 5v Regulator?  My suspicion is that Rigol may have lowered that voltage.

Rigol implemented a hardware fix for this long ago...before Nov 2013!  If you're buying a new unit and not second-hand I don't think you need to worry about this issue.  Read the whole thread if you want to know exactly what went down and various fixes proposed by individuals, or start around page 30 of this thread to see pictures of updated PCBs...  Rigol probably have even more recent hardware revision by now...

Sparky

[mij59]

Wondering if there's a thermal issue with the secondary triac switch at 3A output current.

At 3A output current the triac  RMS current will be something like 5A, giving a power dissipation of 5 to 6W.
Seems to me the triac is mounted on the same kind of heat sink as the  LM317.

[Kleinstein]

For the loss of the triac it is more the average current that is relevant, not so much RMS. So 3 A average current is more like 3.5 - 4.5 W loss.  Still this could be a problem, but the triacs might be more tolerant to high temperatures than the LM317.

[mij59]

For the loss of the triac it is more the average current that is relevant, not so much RMS. So 3 A average current is more like 3.5 - 4.5 W loss.  Still this could be a problem, but the triacs might be more tolerant to high temperatures than the LM317.

I tested triac switching a few weeks ago and concluded that the power loss is fairly high, take a look at the attachment AN10384.

[sdouble]

A newbie question here.
I have several DP832 at the lab.
Some of them work great.
I have some troubles with 2 units.
I use the 2 30V-channels. They do work constantly. +6V on 1 channel, 1.5 V on the other one. Far from the max current sucked. 200 mA on 1 channel, 100mA on the other one.
After some hours of use, they erratically switch off. They I can switch them on again. But that's pretty annoying.
Any idea about where that problem could come from ?
Cheers

[thm_w]

A newbie question here.
I have several DP832 at the lab.
Some of them work great.
I have some troubles with 2 units.
I use the 2 30V-channels. They do work constantly. +6V on 1 channel, 1.5 V on the other one. Far from the max current sucked. 200 mA on 1 channel, 100mA on the other one.
After some hours of use, they erratically switch off. They I can switch them on again. But that's pretty annoying.
Any idea about where that problem could come from ?
Cheers

Did you look inside to see if it has the old smaller heatsink or the newer bigger heatsink?
Is firmware recent?

Take them back if still under warranty.

[sdouble]

Yes, the firmware is recent. But I did not dismount the units yet. I should do that ASAP I guess.
unfortunately, I stored those units in the lab for more than 1 year before I used them for the 1st time.
In addition, I bought them from TEquipment ,meaning that I would have to send them back to the US... I am in France !
Shipping cost is just prohibitive.

[jficara]

Hi,

Does anyone know if there is there any way, without opening up the DP832, to see if you have a unit that has the larger heat sink fix?  A greater than serial # or something that indicates a version that has the fix.

I am still under warrantee and didn't want to risk voiding the warrantee by opening it up to check.

Best,

Joe

[mcinque]

You can see it thru the vent holes on the right side of the unit. Use a flashlight and if you have the "bigger" silver heatsink, you will easily see it.