TDS754D - solder advice, and some whining - Page 1
Forum section: electronics / repair

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 12, 2016, 04:45:29 pm
content: Hello Folks,its time to get back to my TDS754D - if just to clean up the lab, as the DPO takes one full work bench. Due to the presence of an error targeted specifically at U416, I removed the IC. Turned out to be somewhat simple: first, I cut one row of pins loose, and then I broke the IC out and cleaned the pads a bit.In the next step, I figured out to try my replacement parts...only to see that I had bought SOJ400 instead of SOJ300 (bummer). But with the package already open, I cant return them to Mouser either way., I am an Idiot. Need to figure out what to do with these SRAMs now, especially as they came with a large warning about moisture when exposed.But on to the main problem. All I have is an ERSA i-con nano. I soldered some normal SMD stuff before, but never one of these SOIC ICs which have the pins bent under the main IC body.Anyone, any ideas for me?All the bestTam

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 12, 2016, 04:47:46 pm
content: Hello,it looks like the Forum ate my second image showing the actual IC. So here it is.

author: Jwalling
author_rank: Unknown
timestamp: August 12, 2016, 05:39:50 pm
content: Quote from: TAMHAN on August 12, 2016, 04:45:29 pmHoly crap!I thought I was the only one to make the same mistake repairing TDS700 scopes. I still have a full tube of the SOJ400 chips collecting dust.Quote from: TAMHAN on August 12, 2016, 04:45:29 pmYou need a very fine point soldering iron, and very thin solder. I tin one pad then set the chip on it and solder it. After making sure that the alignment is good, then just solder the rest.Jay

author: eKretz
author_rank: Frequent Contributor
timestamp: August 13, 2016, 02:09:55 am
content: Same here with the soldering method - I find it extremely helpful to use some extra paste flux as well. It helps a lot with solder flow and keeping the joints neat and clean.

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 15, 2016, 08:09:02 pm
content: Hello,sorry to ask stupid - that flux thing, so far, never grew to me. But I was at the random electronics shoppe today to buy something else, and they sold me the attached. Sadly, no thin solder - the thinnest they had was 0.6mm.Is this recommended? Or would you suggest something else? I have a big Mouser order upcoming, so if someone wants to help me by giving an URL, I am even more thankful.

author: Jwalling
author_rank: Unknown
timestamp: August 15, 2016, 08:41:05 pm
content: I would think that .6mm would work fineJay

author: KE5FX
author_rank: Super Contributor
timestamp: August 15, 2016, 10:54:28 pm
content: If the chips are pin-compatible and it's simply a package mismatch, just bodge them in with (very short) jumper wires. Chances are it'll work fine unless the design was extremely marginal to begin with.

author: Jwalling
author_rank: Unknown
timestamp: August 15, 2016, 10:59:05 pm
content: Quote from: KE5FX on August 15, 2016, 10:54:28 pmYeah, then post the results here:https://www.eevblog.com/forum/repair/show-us-your-ugly-repair/Jay

author: timb
author_rank: Super Contributor
timestamp: August 15, 2016, 11:41:32 pm
content: So, are you upgrading to the 2M option by replacing the smaller SRAM chips with the bigger ones? I noticed on my 754C that the footprints have more pads than the installed memory chips use. So I assume it would be possible to replace them with the larger chips?

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 12:35:54 am
content: Quote from: timb on August 15, 2016, 11:41:32 pmHe's just replacing one defective chip. I'm sure that upgrading it to 2M is theoretically possible on "C" scopes, as you say the pads are there, but not so practical given its age and value. 64 chips, yikes!The "D" series of scopes above serial prefix B030XXX already have the correct SRAM parts for 2M. Over B040XXX, they went with synchronous burst-mode memory instead of SRAM. They can be upgraded to 2M easily as well.JayJay

author: timb
author_rank: Super Contributor
timestamp: August 16, 2016, 06:25:39 am
content: Quote from: Jwalling on August 16, 2016, 12:35:54 amAh, that makes sense. I was just curious if it was possible; you couldn't pay me enough to do 64 chips by hand. Maybe with a hot air gun, but personally I wouldn't risk it.

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 09:53:51 am
content: Quote from: timb on August 16, 2016, 06:25:39 amYou could pay me enough, I'm unemployed! If the price were right, I'd do it. I would hate every moment, what a tedious job that would be - 2048 solder joints to be made.Jay

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 16, 2016, 01:25:50 pm
content: Didnt have time to reorder the new IC yet, so I cant report any news on the repair front. Plus, I opened up the 34401A I thought to have just ohms current source problems - nada, the entire DC Voltage area seems fooked, while the current source I spent hours repairing was fine and dandy all along.But, in the mean time. AFAIK, there are two versions of the TEK754Dplanar in da haus: I cannot say anything about earlier versions (" ", A, B and C).The one, which has BGA memory controllers and FOUR memory ICs is the 2M model and IMHO can not be upgraded. The one I have, picture attached, afaik is the 8M capable model. Why? Well. The same layout is also at the bottom of the acquisition board, which I had out recently but was too lazy to make a photo of its back. So we have 16 of these memory ICs per channel, which gives a whopping 8M sample space if I am not totally confused (which can be). If I recall correctly, upgrading involves the sending of some PITBULL GPIB command...

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 01:54:59 pm
content: Quote from: TAMHAN on August 16, 2016, 01:25:50 pmI think you're a bit confused. The 2M option was the maximum amount of memory ever offered in a TDS700C or TDS700D. This gives to 8MB of memory on one channel, or 2MB of memory on all four channels. See my post above. There is no option 8Mhttps://www.eevblog.com/forum/repair/tds754d-solder-advice-and-some-whining/msg1005193/#msg1005193

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 16, 2016, 04:21:13 pm
content: Hello,yes, that indeed was a misunderstanding. I meant with 2M, that a total of 2 Megapoints can be stored. And with 8M, that 8 Megapoints can be stored total.Sorry for causing confusion here.Tam

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 05:49:29 pm
content: Quote from: TAMHAN on August 16, 2016, 04:21:13 pmYou're still not getting it, or I'm misunderstanding you. There is no option 8Mperiod. Option 2M is 8 megabytes of ACQ memory total. With option 2M you can store 8 million points on one channel only.2M: Extends standard acquisition length from 50,000 points per channel to 2 million samples on three or four channels, 4 million samples on two channels, and 8 million samples on one channel.Jay

author: TheSteve
author_rank: Unknown
timestamp: August 16, 2016, 06:21:53 pm
content: Quote from: timb on August 16, 2016, 06:25:39 amI'd totally do it - crank the tunes and get to work. I would look at it as a challenge. I wouldn't want to do it day after day of course.Years ago we took a bunch of 4MB simms and made them into 8MB for fun - same sort of deal, hundreds/thousands of PLCC solder connections(ram was way expensive then!).

author: nctnico
author_rank: Super Contributor
timestamp: August 16, 2016, 06:50:03 pm
content: Quote from: TAMHAN on August 12, 2016, 04:45:29 pmPut solder blobs on the pads, add flux, put IC on top and then use hot air to reflow.

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 06:53:19 pm
content: Quote from: TheSteve on August 16, 2016, 06:21:53 pmFor free?It would be a challenge, and I know I could do it, but no way for free!Would require at least three beers to steady my hands.I would do it for $500 labor + parts. Any takers?Jay

author: TheSteve
author_rank: Unknown
timestamp: August 16, 2016, 07:49:07 pm
content: Quote from: Jwalling on August 16, 2016, 06:53:19 pmI'd do it if it was my scope and I'd do it for a friend. It isn't something I'd really care to do for someone I don't know.

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 08:12:49 pm
content: Quote from: TheSteve on August 16, 2016, 07:49:07 pmHowdy Friend!

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 16, 2016, 08:14:53 pm
content: Hello,sorry for asking dumb again: do you think the hot air process is preferrable to simply using the Ersa? I never worked with hotair so far...Re the options: Tek says this:50 K (Opt. 1 M: 500 K, Opt. 2 M: 8 M)I miswrote it. I meant: if you have a planar, which looks like the one I pictured, you can enable 2M and get 8MPT for one channel. If your planar looks different, you can usually only enable Option 1M, giving 500K.

author: Jwalling
author_rank: Unknown
timestamp: August 16, 2016, 08:20:17 pm
content: Quote from: TAMHAN on August 16, 2016, 08:14:53 pmIf the D model is B040XXX or higher, it has the burst mode memory and option 2M can be enabled.Jay

author: siggi
author_rank: Regular Contributor
timestamp: August 16, 2016, 10:17:11 pm
content: Quote from: Jwalling on August 16, 2016, 08:12:49 pm

author: TheSteve
author_rank: Unknown
timestamp: August 16, 2016, 10:24:23 pm
content: Quote from: Jwalling on August 16, 2016, 08:12:49 pmThese are the same friends that helped me move when I bought a house and came over for a day to help dig a big hole and then mix/pour concrete for a new antenna tower base.