GW Instek GSP-930 Spectrum Analizer doesn't boot - Page 1
Forum section: electronics / repair

author: videobruce
author_rank: Frequent Contributor
timestamp: March 13, 2015, 09:01:00 pm
content: Any chance anyone has has evperiance with the SA?Long story short; It appears to power on, but the display stays dark. I believe it is not booting because for shutdown if you press the power button, it does not power down. If you hold that button it will do a fast power off (as intended). I ten assume the unit is not booting. It doesn't even get to the 1st splash screen.I have removed the memory button cell, but no difference. I also did a unassembly (which was an adventure), but no obvious signs of problems. The unit is fairly new, the plastic wrap on the screen is still present.Repair with shipping to China (no repair here just like Rigol) is $520 including shipping (which is $270) which isn't too bad except for the shipping.Any ideas??

author: Adal
author_rank: Contributor
timestamp: March 13, 2015, 11:36:35 pm
content: Hi Videobruce.Your SA are under production. So I think is better send to Instek to repair in order to maintain the machine "original"Or if you are brave, take out the covers and put here the pictures and measurementsBest regards.

author: videobruce
author_rank: Frequent Contributor
timestamp: March 14, 2015, 04:29:21 am
content: The 930 was discontinued last fall and replaced by the almost identical 9300 for around$2300 less.Difference mostly being firmware that includes numerous extra measurements and two additional front panel buttons (the only hardware change that I know of unless the main processor was changed to). The 9300 boots almost 2x faster than the 930 and a couple of the specs are slightly different, but nothing really substantial.No measurements were taken since there was nothing to 'measure'. Without a service manual, there is nothing to compare anyway.But I did take photos.

author: Fraser
author_rank: Super Contributor
timestamp: March 15, 2015, 03:01:11 pm
content: When you have no visual clues as to the cause of a boot failure, you are left with the task of carrying out basic checks to establish what is and is not happening inside the unit.1st checks should be the power supply. If you are lucky, the voltages will be marked on the PCB. If not, you should still get an idea whether the normally expected voltage for an embedded computer is present. Next would be a quick check for activity on the address and data buses at power on. If there is no bus activity you are dealing with an embedded computer that is either in Reset or has a critical error preventing even initial boot activity. I could go on but that is enough for nowAurora

author: videobruce
author_rank: Frequent Contributor
timestamp: March 15, 2015, 03:19:00 pm
content: I did test PS voltages and they look ok, but I didn't go any further. I'm just guessing it's a boot failure.

author: Fraser
author_rank: Super Contributor
timestamp: March 15, 2015, 03:38:40 pm
content: Yes but guessing will not advance the diagnostics as there are many causes of boot failureFor info, a service manual for embedded computers can be pretty simplistic as it just shows various 'blocks' connected together by data, address and signal paths. They rarely contain any OS detail. You might get lucky and find a diagnostics mode detailed but that needs the unit to boot first !Many modern service manuals for such equipment just contain basic tests like those already detailed, and then board replacement recommendations plus calibration procedures. If you want to get to the bottom of the problem you will need to do a lot of physical diagnostics to establish what is, and is not happening. All Reset lines, HALT pins and any error indicator pins need to be checked for state. A simple RAM failure can cause failure to boot. Corrupted firmware is an ugly possibility, rendering the unit bricked and non responsive.I worked on a thermal camera with similar symptoms and even reverse engineered the embedded computer to see what was where. After a lot of tests I proved that the board was working but was seeing a critical failure on another board. The fault was a simple Reset line buffer on the video processing board. A 50 pence 74ALS244 chip ! It took time and a lot of effort to reverse engineer the design so it is sometimes best to bite the bullet and go for OEM repair if simple tests reveal nothing obvious, like a clock generator or Power On reset management chip failure.Aurora

author: videobruce
author_rank: Frequent Contributor
timestamp: March 15, 2015, 04:24:23 pm
content: Unfortunately for me, your abilities are well above mine. I'm sending it back, it's just too bad it has to go overseas for this.I picked it up for around $650US w/shipping. For the additional $520US (if I don't go with the TG upgrade), you should be able to get it around $4300US new w/o the TG.

author: Fraser
author_rank: Super Contributor
timestamp: March 15, 2015, 04:39:38 pm
content: Well at least you will end up with a working unit with good calibration and likely some warranty on the repair work. Depending upon cost, a tracking generator is a very useful option to have. You will be able to test and profile filters, amplifiers, antennas (using an external directional coupler) etc. I certainly would not be without a tracking generator in my inventory.Best WishesFraser

author: videobruce
author_rank: Frequent Contributor
timestamp: March 15, 2015, 04:44:47 pm
content: That is what I'm debating on. There are a couple of other factors/issues that come into play which puts that up in the air.Yes, I'm a stern fan of TG's and I' really surprised they are only on less than 5% of the SA's I have seen advertised new and used. That is another $1300US.

author: Fraser
author_rank: Super Contributor
timestamp: March 15, 2015, 04:56:17 pm
content: Ouch ! That is a pretty steep additional cost.You can 'make do' with a simple wide band noise source for simple gain/loss profiling. I bought some built units from China for use as simple test sources.24V supply neededhttp://www.ebay.co.uk/itm/new-noise-source-Simple-spectrum-external-tracking-source-/121368515016?pt=LH_DefaultDomain_3&hash=item1c422091c812V supply needed and supplied(board contains a voltage boost converter)http://www.ebay.co.uk/itm/Noise-source-Tracking-Source-of-Simple-spectrum-analyzer-/251792079309?pt=LH_DefaultDomain_3&hash=item3a9ffa39cdThere are also relatively cheap options available if needing a unit to plot passband profiles etc:http://www.ebay.co.uk/itm/NWT500-Sweep-analyzer-Amplitude-frequency-characteristic-analyzer-/111504357099?tfrom=121368515016&tpos=top&ttype=price&talgo=undefinedAurora

author: videobruce
author_rank: Frequent Contributor
timestamp: June 13, 2015, 11:56:41 am
content: As a update, the SA was received back, good as new. I did consider keeping it, but I took a step back based on further experience with this and others and decided to sell it. The buyer was very pleased as he got a super deal (about 1/3 the cost for new, which it basically was).I did come acrossfourothers (same model) with theexactsame problem. When I tried to get detail on what was wrong and what was done, I couldn't. All I was told was "it needed a hardware and firmware upgrade". I was also told Taiwan would not disclose any more details. That came from Instek's US service manager. Obviously, it was a know problem, no doubt a defective component that they don't want to admit to. I will further speculate that it was one reason to discontinue that model, replacing it with a different number with a few changes and that huge price drop.At least here in the US, it's obvious that Rigol has the low cost test equipment market with good reason.