Rigol DG1062Z repair - Page 1
Forum section: electronics / repair

author: RikV
author_rank: Regular Contributor
timestamp: July 04, 2025, 09:40:10 pm
content: I got this SG for a good price. The pictures showed all frontal BNC connectors severely damaged but seller sold it as "working till taken out of service. Of course, it wasn't at all.Fixing those connectors was a simple matter of soldering. Fixed in no time.Probably the instrument had been dropped: the TFT screen was barely ligible and full of vertical stripes! Ebay to the rescue: 11€ and 5 days of delivery delay. No problemChannel 2 worked like a charm, both in HighZ an 50 Ohm.Channel 1 on the other hand: "Output overload!" (or something like that). Output amplfier dead... Searching through EEVblog, i found that the type is THS3095DDAR. I also found a more recent type: THS3491. Drop-in replacemnt but 900MHz GBW instead of 600. Should work, I believed.First time I soldered an IC with EP. Worked first try on High-Z But runs immediately extremely hot to the touch when loaded with 50 Ohms.EP not well soldered? Second try with new chip to be sure. Definitely certain this time the EP is well connected (How could you verify this?). Same result Burning hot when loaded on 50Ohms, otherwise functioning.Makes me think: is HS3491 really a substitute to HS3095? Did I mis something in the datasheet? NO oscillations are visible on the SA, th Opamp behaves normally when not loaded... Anyone any idea before I once again replace the opamp??I want to add the datasheet from TexasI which are 3200KB each but the system thinks they are bigger than 8000K each??

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 05, 2025, 01:51:54 pm
content: Having fixed a couple of over voltaged fuction generators, I can only offer you some possible tests to figure out the problem:1. Measure the input signal to the THS3491 to make sure that the IC is not being overloaded.-more than likely there is more than one IC in the chain that was effected by an over voltage input condition as I wound up replacing most of the analog chips when that happened to me.2. Using a heat sensing thermometer, test the temp of the IC to see if it is within specs.-If it has gone over spec once, it probably needs to be replaced.3. Measure the 50 ohm output resistors for the correct resistance.4. Measure the input voltage to Vdd, and Vee.5. As I remember, there is a power down pin on those chips, make sure the voltages for the PD and pinout is correct.Those seem to be a good start and if none of them give you an answer, start thinking like a test engineer, and figure out the problem by testing everything.

author: RikV
author_rank: Regular Contributor
timestamp: July 05, 2025, 05:21:48 pm
content: No offence meant,but being a test engineer for over 50 years, I surely have checked all these points. The output stage works correctly when loaded down to 100 kOhm. Up to 1Vpp (on 50 Ohm) it works correctly. The opamp (gain = +10) only swithches in at voltage level above 1Vpp (opamp enabled at this point and a relay swithes the output in. No overdrive, no oscillations visible on the scope nor SA. As I do not have a schematic diagram of the output stage (however, there should be nothing special following the opamp?), I cannot be sure of the cause:1. The chip is not well soldered (again).2. The HS3491 IS different from the HS30953. A component following the output of the opamp is defective.Cause 3 is very unlikely since ther are no circuit modifications between HighZ and 50 Ohm output. HighZ works reliably up to 20Vpp.I hesitate to resolder the chip again fearing delamination of the PCB...Appreciate any insights in interpreting the datasheets explaining this behaviour..

author: RikV
author_rank: Regular Contributor
timestamp: July 05, 2025, 06:27:42 pm
content: Is there anyone who has a service manual or even a (partial) schematic/partslist of these devices?

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 05, 2025, 08:19:04 pm
content: Maybe this will help:No.088 - Rigol DG1022Z Arbitary Waveform Function Generator RepairSorry, I couldn't find any schematics in any of the manuals or tech service pdfs or on the web.Maybe the resistor networks for the gain were shorted out somehow?Maybe there is output voltage sensing for calibration which also got zapped?Following best practices for hotair rework should not cause the pcb to delaminate when taking off the IC and putting the new one on.I hope that helps.

author: teatime
author_rank: Contributor
timestamp: July 06, 2025, 02:41:19 am
content: Hello, I have repaired the DG1022 and DG4162,This chip is 3095,please see the attachment.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 06, 2025, 03:30:29 am
content: Quote from: RikV on July 04, 2025, 09:40:10 pmReread your original post.So the chip works, but it's running hot.You could either try the ths3095 and see if that one runs hot, or put a small heatsink on top of the ths3491 and call it a day.It might just be the amount of thermal routing away from the IC that is just not enough for the 3491.

author: I4E
author_rank: Regular Contributor
timestamp: July 17, 2025, 02:53:10 am
content: I might have a user manual but don't have service manualNo promises but if you think it would be useful I can lookSincerelyJoy TorresInstruments 4 Engineers Ltdhttps://www.instruments4engineers.com/Authorized Rigol, Siglent and Micsig Distributor

author: RikV
author_rank: Regular Contributor
timestamp: July 19, 2025, 09:34:52 pm
content: I took a chance on it. Let the thing run 10MHz 10Vpp with 50ohm load. It immediately runs hot (to the touch). Using my Fluke 287+thermocouple the thermal pad rises to 50°C (ambient that day 30°C!), body temp 55°C. Body temp 5°C above Thermal pad, proof that the EP is in contact with the PCB . I did not trust this situation, the more since I cannot measure the temp with closed case.So, I glued a small heatsink (6*6*5mm) on top of the 3491. After 10 minutes PCB temp is 45°C (ambient 25°C this time) and the heatsink 40-42°C. Almost 10°C improvemen! I have decided to let it be as is and not to replace the 3491. Time will tell if it survives.Conclusion: TSH3491 is not a good replacement for the TSH3095 in this application.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 24, 2025, 11:10:07 pm
content: Quote from: RikV on July 19, 2025, 09:34:52 pmYour results got me curious.Is the thermal pad the highest temperature that you can measure when probing on and around the chips?I was thinking that the THS3491 was at almost it's maximum temperature, but with your measurement of 50C, that's only 1/3 of it's max temperature.It's automatic shut down is at 165C and re-enables at 145C.What temperature does the 3491 get to if you increase it to 20Vpp?What was the temperature of the THS3095 on channel 2 when it was under the same load and frequency conditions?I'm curious because I've seen that opamp too, and thought I would use it in one of my Siglent AWG one day.