Isolated channels oscilloscope THS710A or what else? - Page 1
Forum section: electronics / testgear

author: hibone
author_rank: Regular Contributor
timestamp: June 24, 2015, 05:06:18 pm
content: Dear all,I have found a THS710A at about 400 € and I am wondering if it is a good deal.First and foremost, please don't misunderstand. I know it is a Tektronix, which should be all there is to say, but I am not in urgent need, at the moment, and also in my point of view there may be a few alternatives.For a few more buck I can buy the Hantek DSO1062S which can be hacked, I guess, to 150Mhz, it has an USB port, a bigger screen probably, the firmware source code (am I wrong?) and maybe something else I don't know yet, but I am afraid that the firmware interface may be crappy to use, and I am pretty sure that the hardware is quite cheap, thus I wonder if it may be a better option.Also, for the same amount, I should be able to get a couple of pinktek dp50, which have 50Mhz bandwidth, and four attenuation ranges (up to 6.5Kv), that I can apply to the Rigol DS2072A-S scope I already have (which is fully hacked, by the way). Thus in this case I will have a lower bandwidth, but a much higher voltage range.In addition, I already used a TEK TDS2024B and I didn't enjoyed the firmware much, ( in regard to this I love the Rigol Firmware much more), thus I am wondering if the THS710A may also be not so comfortable to work with, and thus if I should spend said money, or at least wait for a better opportunity (lower price for instance).Any alternative on the cheap side? An handheld 2 insulated channel scope by rigol for instance, hack-ready since we are at it?Thank for your time.Regards.

author: tautech
author_rank: Super Contributor
timestamp: June 24, 2015, 06:35:31 pm
content: Siglent SHS1000 serieshttp://siglentamerica.com/pd.aspx?tid=2&T=1

author: hibone
author_rank: Regular Contributor
timestamp: June 24, 2015, 09:18:58 pm
content: Thanks for the suggestion.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 24, 2015, 09:34:19 pm
content: I have been using the Tektronix THS720A and THS720P scopes for a long time, when I needed a lightweight and battery powered scope.They are extremely reliable and easy to use.Only problem is that you can not get the original NiCad batteries anymore or they are just far too expensive.Solution: Install normal rechargable batteries, but it requires and little modification inside the scope.

author: TheSteve
author_rank: Unknown
timestamp: June 24, 2015, 10:33:02 pm
content: The THS710A is a great unit as long as it is still working good. I just sold a THS720 and bought a Rigol DS1054Z and had money left over. While I love the Tek name and quite liked the THS720 the features of the DS1054Z made it worth the change. Of course the THS720 was handheld/portable, the DS1054Z is not so it wouldn't suit your requirements.I also have a THS730A at work and we made a replacement battery for it, only took 30 minutes or so.It is a piece of pipe that just fits AA batteries. I used a nickle tab at the top end to make the positive contact and then ran power down two sides of the tube using copper tape to a ring made of silvered braid which makes the positive contact to the scope. The diameter of the pipe was enlarged using 2 or 3 layers of clear heatshrink tubing so it fits perfectly in the scope. It works great and nicely holds 4 Eneloop AA nimh cells.Something to consider if you get the THS710A and need to run it on batteries, it also doesn't require any changes or mods to the scope itself.

author: hibone
author_rank: Regular Contributor
timestamp: June 24, 2015, 10:45:28 pm
content: That's good to read.I've read about the diy battery replacement and I really enjoyed the idea. I will take care of that if I manage to buy the THS710A. I still wonder if 400 € may be not a good deal on a 25 years old scope.Also, there is a thing that is not all that clear to me, since the manual seems to avoid the topic.The manual states that the voltage difference between the "commons" of the BNC shall not be greater than 30Vp when using low voltage probes. It doesn't provide information about the maximum allowed voltage difference when using high voltage probes.Looking at the scope board, shown in a tear down in this forum, I couldn't see the wiring between the board and the BNCs common, so I am not sure about this matter. I suppose that the wirings are there nonetheless thus, unless there is some magic of sort at work, the maximum voltage across the two common is 30 Vp even wihen high voltage probes are used on both BNC. Am I wrong?Thank you.

author: hibone
author_rank: Regular Contributor
timestamp: June 26, 2015, 06:37:14 am
content: Any other suggestion?I mean, is the THS710 always better than a couple of differential probes?

author: Marco
author_rank: Super Contributor
timestamp: June 26, 2015, 07:25:28 am
content: Quote from: hibone on June 24, 2015, 10:45:28 pmAFAICS those are safety limits because of the exposed shields of normal BNC connectors ... if there is significantly more voltage between them with normal BNC then at least one of them is dangerous to touch."30 V RMS , 42.4 V pk , using noninsulated connectors or accessories"AFAICS with insulated connectors only the Voltage to Earth limit (600V RMS) of each channel individually has to be taken into account which then also becomes the common to common rating.

author: hibone
author_rank: Regular Contributor
timestamp: June 26, 2015, 11:33:54 am
content: That's what I wanted to believe, but it felt strange that they didn't clearly state that.Nonetheless as far as I remember, the standard P113B probe does not have a naked bnc connector, but indeed, it is not rated, and also the ground in the tip is exposed.Anyway, thank you for clarifying.Regards.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 27, 2015, 11:47:51 am
content: Quote from: TheSteve on June 24, 2015, 10:33:02 pmGreat idea and easy to implement.I will make one of these myself.Thanks for sharing.This way you can even use the original TEK desktop charger, I would presume.

author: BravoV
author_rank: Super Contributor
timestamp: June 27, 2015, 12:57:10 pm
content: Quote from: HighVoltage on June 27, 2015, 11:47:51 amThe original Tek desktop charger is a slow charger, only suitable for NiCD based cells, and probably not the best for NiMH based cells.For my THS710A, I modded AA to C adapters and made it so I can detach each cell independently, and charge the NiMH cell using proper NiMH charger like Maha MH-C9000.Currently I don't have it with me, but below photo should give you the clue how to build the battery replacement using modern AA NiMH cells, and yet have the flexibilities to replace cells and charge them separately.Hope this helps.

author: hibone
author_rank: Regular Contributor
timestamp: January 04, 2016, 01:58:38 am
content: I finally got my paws on a THS720P Oscope.The battery started to show a little bit of "rust" at the end near the cap (the greenish acidic stuff), but it seems it still can hold a little bit of its charge (charged by putting the scope under charge).Regarding the battery I am thinking about replacing the original one by fitting 16 AAA eneloop into a 2.6 mm PVC pipe.I think I can assume that the battery pack will be charged without any issue, but I would like to hear your opinion.Thank you.