WTB Tektronix THS710A Inverter Board - Page 1
Forum section: electronics / general

author: Flump
author_rank: Frequent Contributor
timestamp: August 08, 2015, 11:04:55 am
content: I have a chance to buy a Tektronix THS710A but the Inverter Board is missingare these availible ?

author: Monittosan
author_rank: Regular Contributor
timestamp: August 09, 2015, 10:32:37 am
content: Drive some SMD white LED's and enjoy increased battery life and a brighter display?

author: Flump
author_rank: Frequent Contributor
timestamp: August 09, 2015, 03:19:49 pm
content: I have no idea if that would workI found one cheap for sale but he says the inverter board is missing,I doubt it's as simple as adding a few led's ?

author: PlainName
author_rank: Super Contributor
timestamp: August 09, 2015, 04:14:53 pm
content: Abrokeninverter board wouldn't be unusual, but 'missing'? Implies someone has been in there doing who knows what.

author: Flump
author_rank: Frequent Contributor
timestamp: August 09, 2015, 04:21:52 pm
content: Yes that makes me wonder what else has been messed with inside itHere is the advert, I cant link to it as you have to be registered on a UK ham radio forum to see it"As t title says I have a bagged Tektronix THS710A 60Mz Scope. Comes with the serial PC Cable but no probe, no idea where that's gone.All the manuals and PC Software.Now the issue, it hasn't got an inverter board. No idea whey it's been removed but it is a slot in part and popping the front off you can see where it would go.No idea why it's been removed but this may suit someone for parts/spares/repair. Came in a box of bits I bought, I've lost the box of other bits in a house move, blaming the XYL!!! Board may have been in there.Looking for £50 posted. (got to be worth that for the bits). Get the board and you get a very cheap 60Mz scope."

author: Fraser
author_rank: Super Contributor
timestamp: August 09, 2015, 04:40:11 pm
content: That's a very good price for a parts donor but I would only buy it if I could easily afford to waste the £50. On a positive note, if the unit turns out to be beyond a rebuild, it is worth at least £50 as parts on eBay.I have not looked at the schematics but I suspect the inverter board is actually the board that generates all the required voltages for the scope. I.e. Not just the backlight. Without the board you have no supply rails. Could a replacement be made ? It would be worth taking a look at the schematics that helpfully became available to the public recently.I would even be tempted to buy the unit if you do not want it. If so, please will you consider PM in me the contact details.Best WishesAurora

author: TheAmmoniacal
author_rank: Unknown
timestamp: August 09, 2015, 04:40:59 pm
content: I'll give you £50 for it! Send it to me!

author: Isad
author_rank: Frequent Contributor
timestamp: August 09, 2015, 06:56:29 pm
content: Just found this as it looks the inverter board seems like Monittosan saidits the cfl driver.Your lucky zucca did this teardown.https://www.eevblog.com/forum/testgear/tek-ths720a-portable-scope-teardowndiscussion/

author: BravoV
author_rank: Super Contributor
timestamp: August 09, 2015, 07:14:07 pm
content: Quote from: Isad on August 09, 2015, 06:56:29 pmOr even better one, the schematic and BOM ->Tektronix THS700 tekscope Component-Level Information Package and schematicAs a THS-710A owner, I can feel your pain, wishing you good luck !

author: Fraser
author_rank: Super Contributor
timestamp: August 10, 2015, 01:57:40 am
content: Thanks to Flump's kind help. I am now the owner of the faulty THS710AOnce I have it I shall report on its condition and whether it is viable to return it to working order. Watch this space.Aurora

author: Zucca
author_rank: Unknown
timestamp: August 10, 2015, 07:16:15 am
content: Quote from: Aurora on August 10, 2015, 01:57:40 amThat´s a good news! Congrats!

author: Isad
author_rank: Frequent Contributor
timestamp: August 10, 2015, 10:05:28 am
content: Quote from: Aurora on August 10, 2015, 01:57:40 amCongrats!I hope its as easy as it looks.

author: Fraser
author_rank: Super Contributor
timestamp: August 10, 2015, 12:16:59 pm
content: I have ordered a universal ccfl inverter for 5" - 14" displays. It will be a quick test to see what is, and is not, working.on the scope. I bought it as a parts donor for my THS720 but it is worth seeing g if it can be repaired.Aurora

author: Fraser
author_rank: Super Contributor
timestamp: August 19, 2015, 04:25:38 pm
content: The THS710A, sans inverter, arrived today.It is in great condition and has obviously been well cared for in its working life. Even the carry case is is unmarked condition. The battery and the data cable were included, along with the user manuals for the scope and Wavestar software.A bonus was the inclusion of both Demo (V1.2) and licenced (V1.3) versions of the Wavestar software.I have received one potential replacement inverter and three other types are still en-route to me. The challenge is the inverter supply voltage. Most expect more than the THS710's 4.8V supply rail. I have found one 5V to 28V Universal Inverter that May operate OK at 4.8V. we shall see.http://www.ebay.co.uk/itm/New-AVT5-28V-Universa-CCFL-Inverter-For-LCD-LED-Screen-5V-28V-Range-/231069169933?hash=item35cccbb90dIf all else fails, a Boost converter will be employed to step up the voltage to the inverter. Another option will be to hunt down either an OEM Tektronix inverter or one from a piece of portable equipment that also uses a 5V inverter package.More when I have the other inverters and time to play with the unit.Aurora

author: Fraser
author_rank: Super Contributor
timestamp: August 19, 2015, 05:56:58 pm
content: OK I have a firm plan in place to replace the inverter.The original CCFL backlight inverter is not a sophisticated design. It is just an LT1172 boost converter producing 12V into a conventional 'dumb' CCFL inverter design for small LCD single tube systems.As the supply to the inverter comes from the approx 4.8V Ni-Cad supply rail there will be an unregulated drop in supply voltage during operation. A 5V minimum supply inverter may not tolerate this.I have ordered a boost converter to supply the inverter with its ideal 12V no matter what the Ni-Cad voltage is doing.The unit is small enough to fit easily in the scope and it has the advantage of an 'enable' input so replicates the original TEK design.http://www.ebay.co.uk/itm/5W-DC-5V-to-12V-with-ON-OFF-IO-Control-Switch-Step-up-Boost-Converter-Power-UK-/351101047047?hash=item51bf40d10712V CCFL inverters are common and I already have a very neat unit designed for 5" to 7" LCD panel CCFL tubes. Perfect for this application apart form its supply needs. I also have the other 12V CCFL inverters en-route to try if they are better suited to this application.I think this may be the best solution to the challenge but I will still test the universal 5V to 28V inverter when it arrives as that likely just uses a buck-boost converter anyway.Aurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 19, 2015, 08:08:53 pm
content: Maybe just try and repairt the inverter board or is it gonsky.

author: Fraser
author_rank: Super Contributor
timestamp: August 19, 2015, 10:27:56 pm
content: Yep, it is Gonsky.The seller advised that it was missing so this was expected.The requirements on the inverter are quite modest so another should work fine in the unit. I expect to need an inverter that produces ~800V with a maximum of 5mA for the CCFL tube, from a supply rail of 4.8v.Whilst I have found CCFL inverters that will run on 5V rails, I cannot source one in the UK, and they tens to be very simple types so have no on/off pin or dimmer capability. I have five inverters en route to me including one sourced from the UK. I expect to find what I need from at least one of them. The 5V to 12V Boost converter does seem the way to go as 12V appears to be the most common supply for these inverters.I thought I would find more very compact inverters that are commonly found in older mini LCD monitors of %" to 10" size. Sadly this was not the case. All of my older mini LCD monitors have very simple HV converters built onto the PCB which may explain the lack of discrete inverter PCB's for such.This is just a fun project for me. No mad rush or need but I would like to see what else, if anything is faulty on the scope.Aurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 20, 2015, 08:45:29 am
content: Oh i forgot that he said the board was mising.Yeah i have found those inverter board to generally they are used inbig industrial printers.Hope you get it working its a nice bit of equipment and for 50 pundsits really a bargain.I wanted to get this but sadly didnt have the money atthe time and u were faster dam it.

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2015, 10:24:28 am
content: The seller lowered the price to £25 before I got his contact details so it was an even better dealI am amazed that it did not sell for the original £50 asking price.Aurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 20, 2015, 12:38:36 pm
content: Quote from: Aurora on August 20, 2015, 10:24:28 amAw i should have askeddam it.Nice score i hope you get it wroking

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2015, 04:19:17 pm
content: Another inverter arrived today. Its smaller than I had expected.....excellent.This particular inverter can be powered with any voltage between 5V and 28V which makes it pretty versatile. Its output is around 1000V. The only chip used on it is the MP1010BEF CCFL driver. Datasheet attached.The inverter supports the enable/disable backlight, and dimmer functions. Only 4 connections. 0V/+Ve/Dim and Enable.I may, or may not need the boost converter with this inverter. We shall see.If you want a very neat little HV inverter, this puppy looks decent quality. £2.48 delivered to the UK.http://www.ebay.co.uk/itm/191612934638?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITAurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 20, 2015, 04:22:23 pm
content: I have had 1 of those they are pretty neat and are used quite offtenin onehung low but are pretty nice and dont burn out that easy especalyif you use it in a device that stays on 1 to 2h lol.

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2015, 04:39:12 pm
content: @Isad,It looks OK so hopefully it will last as well. I did buy a spare in case I trashed one during testing/modification.I have some other types en route and they include another 5V to 28V model that at first glance looks like this inverter. It differs in that it has two switching transistors external to the driver IC. I thought about cutting that PCB in half to reduce its length. I was going to cut it between the transistors and the transformer and reconnect the two tracks with flexible wire. i may not need that inverter now though.Aurora

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2015, 05:08:16 pm
content: A better datasheet on the MP1010B CCFL driver is attached.It looks a useful little chip. It has tube O/C and S/C protection capability and the tube current is set by a single resistor 'Rlfb' that sits in the tube secondary circuit on the 'cold' side. 140 Ohms provides a tube current of 6mA. Perfect for my needs in the THS710a.Aurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 20, 2015, 08:38:35 pm
content: Those chips are quite handy until you try pooking in there.I had a board that used those in a monitor i tryed turning theminto lights for my bench since i didnt want to buy light and wantedto have a nice project i ended up trashing the board cuz iand now i have ended up with a zvs controlling the transformer.Looking foward to see that scope working or if it even works lol.

author: Fraser
author_rank: Super Contributor
timestamp: August 20, 2015, 08:54:52 pm
content: @IsadMe too.It may have other faults and the inverter was taken from it to repair another unit. If so, it will become a spare parts donor for my THS720The display on my THS720 seems a little low in contrast so maybe it needs a new LCD panel ?I will post news here as soon as I know more on the 710's condition. I will also test the battery capacity as I need a good one for my 720.Aurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 20, 2015, 09:51:55 pm
content: Quote from: Aurora on August 20, 2015, 08:54:52 pmSeems like you get a win-win out of that pretty nice.

author: Fraser
author_rank: Super Contributor
timestamp: August 21, 2015, 02:08:10 pm
content: The mini boost converters have just arrived. Either will do the job but one has an enable/disable facility.With them being so neat, well made and cheap, there is little point in making your own these days.Aurora

author: Isad
author_rank: Frequent Contributor
timestamp: August 29, 2015, 09:35:42 pm
content: Hey AuroraWas jsut curios how is the repair going.

author: Fraser
author_rank: Super Contributor
timestamp: August 29, 2015, 09:45:40 pm
content: No more done on it as yet. I am undertaking a major tidy and thinning of all my electronics and test equipment. Sadly it is taking all of my spare time at the moment. It's a major taskI will report here as soon as I get a chance to play.Aurora