Hameg HM8143 broken, need a little help. - Page 1
Forum section: electronics / repair

author: shempe
author_rank: Contributor
timestamp: October 25, 2015, 02:05:02 pm
content: Hello,I bought a "working" Power Supply a few weeks ago. It was not....ok.I agreed with the seller on some return money because I think it is a good Power supply and worth a repair.So after I bought it, my money box is mostly empty in the moment, and R&S ask for a hand and a limb in repair.I decided I will try to repair it and if I can't fix -> R&S must do it.First all looks ok and working, it start´s without an Error, I can set the Parameters local and remote.But, when I enable the Output, Cannel 1 and 3 there is no regulation, Volts goes to some other Values and Amps are not there.So it looks something is broken.Because im lacking a Service Manual I can only guessing what is broken.So I Inspected the Circuit and found something suspicious, one chip looks like it was loosing his smoke.Can someone Identify this ic ?Here the Smoky oneHere the other one from Channel 1.A few pics from the Board´s because I know, someone like to see the whole thing.Thanks a lot for your time and help.Stefan

author: bktemp
author_rank: Super Contributor
timestamp: October 25, 2015, 02:20:09 pm
content: Looks like a TL431 shunt regulator.

author: mij59
author_rank: Frequent Contributor
timestamp: October 25, 2015, 02:38:13 pm
content: The TL431 is a good candidate, but its not the only problem, maybe the transistors close to the TL431.Seems to me you got two identical boards, assuming that one is working you can compare it with the faulty one.

author: shempe
author_rank: Contributor
timestamp: October 25, 2015, 03:08:37 pm
content: TL431B could be possible.Yes there are 2 identical Boards but the regulation on the output is on both not working,maybe because one channel is broken it affected also the other channel.I will compare the components with the "working ?" channel.Maybe it will give me a clue, what also wrong.

author: mij59
author_rank: Frequent Contributor
timestamp: October 25, 2015, 03:43:36 pm
content: Quote from: shempe on October 25, 2015, 03:08:37 pmBoth channels should be galvanic isolated, the only thing they have in common is the controller board for setting the voltage and current, maybe there is a problem with data transfer, e.g. by I2C or SPI.

author: shempe
author_rank: Contributor
timestamp: October 25, 2015, 04:14:26 pm
content: QuoteThank you for your suggestions.Yes, there are isolated, and normally I would expect, that one channel is running, it is not so, both behave the same.I must admit I2C and SPI is out of my skill set to debug.Without a Service manual I think it looks more and more for a case to fill my Piggybank.

author: Fraser
author_rank: Super Contributor
timestamp: October 25, 2015, 04:14:50 pm
content: Hameg will often provide the schematic for their equipment by return email. Have you asked Hameg customer services yet ? Service manuals are harder to obtain.Fraser

author: shempe
author_rank: Contributor
timestamp: October 25, 2015, 04:24:29 pm
content: QuoteNo I don't, I was thinking, that they don't provide Service Manuals for products that they are actual selling, only for older products.But I will give it a try maybe they provide the schematics.Thank you Fraser.

author: Fraser
author_rank: Super Contributor
timestamp: October 25, 2015, 05:28:39 pm
content: They used to provide the schematic at the rear of their manuals but stopped for reasons unknown. I have never had a problem obtaining the schematics, even for current equipment. Policies do change though and R&S may have different views on support for current models. I have obtained the schematics for their current frequency counter, signal generator and function generators though.Always ensure that in any communications relating to repair, that the OEM knows that you are a technical person with the competence and skills to safely open the case. OEM's can get nervous about liability etc.Good luck.Fraser

author: shempe
author_rank: Contributor
timestamp: October 25, 2015, 06:16:39 pm
content: QuoteSounds promising.I saw in an Interview with an R&S CEO, they support repair and they don't like to see that someone throw´s away there stuff.But, it was not so clear if repair means by there facilities or repair by the owner of the equipment.Btw. good point about competence I will have it in my mind.Thanks Fraser.

author: anotherlin
author_rank: Frequent Contributor
timestamp: October 27, 2015, 07:35:52 am
content: I can confirm that Hameg will send you for sure the pdf for all their discontinued products.As for current product, I've never tried.If it can help, I have the pdf of the service manual for the HM8142. This is the previous revision of this PSU.It should be very similar, specs are almost same, except that the 2 outputs are up to 2A instead of 1A.

author: tec5c
author_rank: Frequent Contributor
timestamp: October 27, 2015, 08:28:24 am
content: If you have a DMM then do a diode test across pins 1 and 7, if shorted then the IC is most likely at fault... out of circuit test to confirm if it reads short in circuit.

author: shempe
author_rank: Contributor
timestamp: October 27, 2015, 09:15:30 am
content: I wrote at the Hameg support yesterday, let´s see what will happen.QuoteYes sure I like to see it. Thank you.It looks like the HM8142 has a total different Layout but I think it is worth a look.QuoteWill try it after Work.Im sure this chip is blown, question is, what else is blown in the path and which parts are in the path.

author: anotherlin
author_rank: Frequent Contributor
timestamp: October 27, 2015, 10:13:40 am
content: https://drive.google.com/file/d/1-Is0VRF70_UMd_U3M2oTfy1NEZetlJU_/view?usp=sharing(updated google drive link to manual)At the end of the user manual is the full schematic along with a short one page very high level description of the operating principle.Text is in french, it basically states that this is a "classic" two-quadrant (can act as load) linear power supply, digitally controlled. But not that much.Use google translate, or I can help if you need it on specific point.

author: shempe
author_rank: Contributor
timestamp: October 27, 2015, 01:03:31 pm
content: Im looking at the components now on one channel of the board to make me a picture what parts we have.I managed so far:Part 11 Atmega64 with ISP1 CY62256N 256-Kbit ( 32 K × 8 ) Static RAM2 LTC1666 12-Bit 50Mps Dac´s1 LTC1298IS8 12 Bit A/DPart 21 ez745 ( 431i ) ???1 ez610 ????3 LTC2051HVIS8 Dual Opamps with Zero Drift1 LT1236CIS8-5 5V Precision ReferencePart31 LT1037IS8 Low Noise, High Speed Precision Operational Amplifiers3 OP275G Dual Bipolar/JFET, Audio Operational AmpSomeone recognize the Logo on this Chip or can identify it.QuoteThank you for the schematic anotherlin

author: Rick60
author_rank: Contributor
timestamp: October 27, 2015, 01:28:01 pm
content: That's almost certainly an LM258DT from st.com the ez610 must be a batch codehttp://www.st.com/web/en/resource/technical/document/datasheet/CD00000464.pdf

author: mij59
author_rank: Frequent Contributor
timestamp: October 27, 2015, 01:34:29 pm
content: On page M13 of the HM8142 manual is a block diagram of the power supply, there is only one set of opto-couplers for the second channel.The power supply for the micro is directly connected to the first channel.If the HM8143 is also configured this way, a fault in one of the power rails of the micro could result in data lost for both channels.

author: shempe
author_rank: Contributor
timestamp: October 27, 2015, 01:48:31 pm
content: QuoteYou made my Day. Thank you.ST it is...Right Part of the Board1 Atmega64 with ISP1 CY62256N 256-Kbit ( 32 K × 8 ) Static RAM2 LTC1666 12-Bit 50Mps Dac´s1 LTC1298IS8 12 Bit A/D2 SFH6186 OptocouplerCentral Part of the Board1 TL431I Programmable voltage reference1 LT1236CIS8-5 5V Precision Reference1 LM 258 Low-power dual operational amplifiers3 LTC2051HVIS8 Dual Opamps with Zero DriftLeft Part of the Board1 LT1037IS8 Low Noise, High Speed Precision Operational Amplifiers3 OP275G Dual Bipolar/JFET, Audio Operational Amp

author: shempe
author_rank: Contributor
timestamp: October 27, 2015, 01:53:05 pm
content: QuoteYes I saw it.It is possible. But when you look at the Picture 3 from Page 1 you see from every Channel a Cable going to the Display board.And near every Cable are the Optocoupler for the communication to the Display board.The Layout for the HM8143 is different to the HM8142These are 2 SFH6186 OptocouplerChannel 15V Channel 2

author: shempe
author_rank: Contributor
timestamp: October 28, 2015, 08:42:14 am
content: Day 3, still no answer from the Hameg Service.Not so Promising

author: mij59
author_rank: Frequent Contributor
timestamp: October 28, 2015, 09:42:00 am
content: The opto-couplers could be used for a low speed I2C or UART.Please post a photo of the display board.Got an Oscilloscope ?

author: anotherlin
author_rank: Frequent Contributor
timestamp: October 28, 2015, 12:59:16 pm
content: Quote from: shempe on October 28, 2015, 08:42:14 amIt's current production model whereas 8142 is beginning of 90s (20 years) model.It is understandable they don't want to provide schematic.

author: shempe
author_rank: Contributor
timestamp: October 28, 2015, 01:44:39 pm
content: QuoteFor a Photo from the Display Board, I need to disassemble the Front Plate need´s to be done.Yes I have a Oszzi.QuoteYes, I agree and I have no Problem to understand and accept that fact.I find it only a little rude, after writing such a nice Email, not to get an answer at all.Imho not a good business behavior.

author: shempe
author_rank: Contributor
timestamp: October 29, 2015, 10:45:36 am
content: Day 4 no response from Hameg.I had a little time yesterday evening, to look in the Communication from Channel 1 Board to the Front Panel.This is Channel 1 , Channel 3 looks the same.First Block is the Voltage Setting, second is the Ampere Setting and Signal for Output enable.You can change it with the Encoder on the Frontpanel and the Buttons for Volt and Amp for Channel 1 and 3If Output is enabled the measurements are send to the Front Panel and displayed.And I found a little more ...It is a more than the 431I broken on Chanel 3.Here more Pics for the interested one´s.0.22 Ohm 1% PBH-R220 Shunt Isabellenhütte Big Black one in the middleBD139 and Tip147 Identified..The 5 Volt ChannelBackside Channel 1Backside Channel 3

author: mij59
author_rank: Frequent Contributor
timestamp: October 29, 2015, 11:33:28 am
content: And I found a little more ...And more to come, check the power transistors on the heatsink and pcb of both channels.Both channels have failed in a similar way, maybe by connecting the outputs antiparallel.

author: shempe
author_rank: Contributor
timestamp: October 29, 2015, 12:04:40 pm
content: Im sure there will be more broken parts.Will look later into it.I don't know how they break this Power supply, normally it should be not so easy.It can sink and source, looks like good quality Parts with much reserve.But you see, it is broken

author: free_electron
author_rank: Super Contributor
timestamp: October 29, 2015, 02:03:55 pm
content: That ISABELLENHUTTE RESresistor is toast toolooks like someone probably rammed power into the output.. and fried half the electronics.

author: RolandK
author_rank: Regular Contributor
timestamp: September 24, 2022, 06:59:43 pm
content: Just repaired one of those. At mineThe TL431 was shorted. The 300 Ohm resistor above it was open.Two 10 Ohm base resistors for the two TIP 147 were about 1k5 and 10k.The BD139-16 which drives the two TIP147 via the 10 Ohm resistors was CE shortet, which leaded to the vaporization of their 10 Ohms base resistors.The BD140-16, which switches the 48V supply if you press the output button, was CE shorted.These transistors are 80V rated, so there must have been a nice overvoltage or inverse voltage at the output, i don't know, i got it broken.As it uses internal 48V and -8V for the regulators it is much easier to get under the -8V where the ouputs can't be switched of any more. I think it is sufficient to connect the 2 outputs in series (+ to -) instead of parallel (+ to +) to kill one of them. The outputs are missing any protection diodes.