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Re: Dark deposit on pins near leaking SMD electrolytic caps

Harvey White
 

Physically, one layer, copper on top.

inner layer (* see note)

outer layer, copper on bottom.

That inner layer can be single sided or two sided, depending.  I don't think that anything in the manufacturing process keeps it from being so.  I've actually made 3 layer boards, although they're quite awkward without plated through holes.

One side of that inner layer can be missing, so yes, a 3 layer board.  I guess it was cheaper to make for some reason, but that was then, long ago (in electron lives) then...

Harvey

On 2/9/2021 11:33 PM, Jim Ford wrote:
3-layer boards?  Never heard of them.  Maybe you mean 3 dielectric layers and 4 metal layers?  PCBs are built up from the inside out, starting with a core (fully cured dielectric sheet plated on both sides with copper foil) and adding more cores and/or prepregs (partially cured dielectric sheet plated on one side with copper) symmetrically on both sides until the stackup is done.  Hence there is always an even number of (metal) layers.  Always!

Jim Ford

------ Original Message ------
From: "greenboxmaven via groups.io" <ka2ivy=verizon.net@groups.io>
To: TekScopes@groups.io
Sent: 2/9/2021 6:02:16 PM
Subject: Re: [TekScopes] Dark deposit on pins near leaking SMD electrolytic caps

The Sonys have three layer boards, I didn't have any problems. However, I can imagine some very bad problems if the electrolyte got into a connection that connects with one of the inner layers. How would you deal with that?

     Bruce Gentry, KA2IVY


On 2/9/21 20:44, Raymond Domp Frank wrote:
On Wed, Feb 10, 2021 at 02:38 AM, greenboxmaven wrote:

I have restored some Sony video recorders that were loaded with the bad
condensers.
The affected Tek 'scopes use multilayer boards, making a slightly more intricate procedure advisable.

Raymond














Re: Tek 1A5 and 132 on eBay for 85 bucks

snapdiode
 

On Tue, Feb 9, 2021 at 05:31 PM, Gary Robert Bosworth wrote:

I often worry about bidding against the seller. It would be so easy for this to happen. No one could detect a ghost bidder who is in cahoots with the seller.

I think eBay has ways to flag that pretty quickly. It was a problem years ago.


Re: Dark deposit on pins near leaking SMD electrolytic caps

Jim Ford
 

3-layer boards? Never heard of them. Maybe you mean 3 dielectric layers and 4 metal layers? PCBs are built up from the inside out, starting with a core (fully cured dielectric sheet plated on both sides with copper foil) and adding more cores and/or prepregs (partially cured dielectric sheet plated on one side with copper) symmetrically on both sides until the stackup is done. Hence there is always an even number of (metal) layers. Always!

Jim Ford

------ Original Message ------
From: "greenboxmaven via groups.io" <ka2ivy=verizon.net@groups.io>
To: TekScopes@groups.io
Sent: 2/9/2021 6:02:16 PM
Subject: Re: [TekScopes] Dark deposit on pins near leaking SMD electrolytic caps

The Sonys have three layer boards, I didn't have any problems. However, I can imagine some very bad problems if the electrolyte got into a connection that connects with one of the inner layers. How would you deal with that?

Bruce Gentry, KA2IVY


On 2/9/21 20:44, Raymond Domp Frank wrote:
On Wed, Feb 10, 2021 at 02:38 AM, greenboxmaven wrote:

I have restored some Sony video recorders that were loaded with the bad
condensers.
The affected Tek 'scopes use multilayer boards, making a slightly more intricate procedure advisable.

Raymond










Re: Dark deposit on pins near leaking SMD electrolytic caps

Harvey White
 

I'm not the first to mention the problems of Formula 409 on plastic.  However, I should mention that Simple Green may have some of the same chemicals, which indicates that a thorough rinse is highly suggested.  The TDS 500 and 600 series have potentially nasty capacitors in them, so part of the re-capping process is to go through and do a scrub with simple green, rinse, dry thoroughly, (possibly use 91% alcohol to help remove the water), then re-cap as needed.

Harvey

On 2/9/2021 9:20 PM, Ozan wrote:
Hi Harvey,
Most people seem not to like 409 because of its effects on plastic.
I've heard several people suggest that simple green should be used for
cleaning off PC boards (and rinsed thoroughly afterwards!).  Another
Good info about 409. Although I don't keep it long on the PCB it is quite strong, time to switch to Simple Green.

Ozan







Re: Tek 1A5 and 132 on eBay for 85 bucks

John Williams
 

Yes I am probably not remembering this correctly. It has been a few years since I had a selling business on eBay. So I guess I really don’t know why it says that on some items. Unfortunately I still am a buyer. The Covid thing seems to have left me with more money to spend on eBay now that we are not able to travel, cruise, and do a lot of other things. Plus I am getting pretty sick of being housebound. I should be doing some of these projects I have lined up. Feet of clay.


Re: Dark deposit on pins near leaking SMD electrolytic caps

Ozan
 

Hi Chris,


The classic recipe for battery leakage on PCBs is a toothbrush scrub (actually
short bristled hogs hair) in a white vinegar rinse. Follow that with a scrub
in a baking soda rinse to neutralize the acid.
Thanks for the recipe, in old times most cells were acidic so baking soda was first but for an alkaline electrolyte vinegar first makes sense. 409 is very basic (probably too much, Simple Green is suggested) so it might do the job of baking soda.

One mystery is why only some IC pins get this dark deposit, there are ICs nearby with no deposit and in some ICs only few pins would get this deposit. It is not always the closest to the cap.

Ozan


Re: Tek 1A5 and 132 on eBay for 85 bucks

snapdiode
 

Well I'm not a very experienced seller, but my few BIN listings show as "this listing has ended" and "sold" superposed on the photos when it sells, as well as a "see original listing" link.

I see no options to indicate anything after a sale for my items.


Re: Dark deposit on pins near leaking SMD electrolytic caps

Chris Wilkson
 

The classic recipe for battery leakage on PCBs is a toothbrush scrub (actually short bristled hogs hair) in a white vinegar rinse. Follow that with a scrub in a baking soda rinse to neutralize the acid. Followed by a "clean water" rinse: de-ionized water if you have it or can afford it, but distilled water is plenty good enough. There's no reason to use tap water...distilled is cheap enough. Last step is a compressed air dying and an oven bake at maybe 110-120C for a "long enough time".

With SMT devices a warm soak is probably better at each stage. To give the cleaning chemicals a chance to get in under the parts.

I was given a 7104 whose filter caps leaked and destroyed the power supply boards. I don't know the chemistry of the leaked electrolyte, but that was some *nasty* stuff! It ate the metal and the substrate of the PCBs. Of course it had been sitting undisturbed on a shelf for probably 20 years, eating away. Having nothing to lose I tried the battery cleanup process and it worked great. The vinegar fizzed up pretty nicely too.

About 7-8 years later I peeked inside again and there was no obvious sign of further damage.


Re: Tek 1A5 and 132 on eBay for 85 bucks

John Williams
 

This item was not on a bidding auction. It was buy it now. So it I a safe thing to do. When the item is purchased the seller has the option to indicate that he has no more of these available. Then the out of stock shows. Sold is only shown if it is a bidding auction.


Re: 465B strange ripple

Mike Merigliano
 

There may be a loose grounding screw. There is a document on cleaning the switches in 4xx scopes, and within it is this:

"One OTHER thing to check: (I'm not sure, at the moment, if this is only for the 465 model, or if it also applies to the 475:) JUST behind the metal attenuator/switch shield "boxes", there may be a screw that connects a metal piece of the box/shield to the circuit board. If that screw is loose (which I have seen on about a third of the 465 scopes I've worked on!), or if it doesn't make good contact, you may see very noticeable effects in the trace(s), such as fuzziness or distortion, and may see trace-distortion effects when adjusting the trigger-level control (possibly especially-so at the highest frequencies), and possibly other triggering problems."



Sorry, I don't remember where I found this, but imagine someone in the group would know, or even wrote it.


Re: Dark deposit on pins near leaking SMD electrolytic caps

Ozan
 

Hi Raymond,

A lot has been written about cleaning methods. AFAIR, thorough washing with an
acidic solution has been suggested and neutralizing afterward by thorough
neutral rinsing. I have used soaking for about an hour in 50% diluted
household vinegar, rinsing and brushing off solids, soaking in washing-up
Good idea with 50% diluted vinegar to neutralize the deposit. The deposit seems to be basic (opposite of acidic). I thought DeOxit would be acidic (pH is not disclosed in SDS) but it seems to be too mild to neutralize electrolyte deposit.

Ozan


Re: Dark deposit on pins near leaking SMD electrolytic caps

Ozan
 

Hi Harvey,
Most people seem not to like 409 because of its effects on plastic. 
I've heard several people suggest that simple green should be used for
cleaning off PC boards (and rinsed thoroughly afterwards!).  Another
Good info about 409. Although I don't keep it long on the PCB it is quite strong, time to switch to Simple Green.

Ozan


Re: Dark deposit on pins near leaking SMD electrolytic caps

 

On Wed, Feb 10, 2021 at 03:03 AM, greenboxmaven wrote:


However, I can imagine some very bad problems if the electrolyte got into a
connection that connects with one of the inner layers. How would you deal with
that?
Electrolyte does go into vias and damages them and inner layers. That's why your best hope is the thorough and time-consuming procedure that I described earlier. It has worked for me in most cases, at least in the 'scopes I mentioned earlier.

Raymond


Re: Dark deposit on pins near leaking SMD electrolytic caps

greenboxmaven
 

The Sonys have three layer boards, I didn't have any problems. However, I can imagine some very bad problems if the electrolyte got into a connection that connects with one of the inner layers. How would you deal with that?

Bruce Gentry, KA2IVY

On 2/9/21 20:44, Raymond Domp Frank wrote:
On Wed, Feb 10, 2021 at 02:38 AM, greenboxmaven wrote:

I have restored some Sony video recorders that were loaded with the bad
condensers.
The affected Tek 'scopes use multilayer boards, making a slightly more intricate procedure advisable.

Raymond





Re: 549 transformer question

boid_twitty
 

I rewound an RM504 transformer 120-199 in about 2012
using E42/21/15 - 3C85 and shim gapping to suit.
It would have fit in the old can, but I stuck it
in a deep-drawn Al can from Zero Mfg ($) as I wasn't
attempting a counterfeit part.

Adding brackets to base allowed fit into previous
mounting pattern.

Core x-sectional area was larger, so I used 1/2turn
technology to tune the voltage relationships and
cut down on the HT heater ballast loss (2R vs 4R3).
Paper shim gap in all legs to get Lp.

Winding area was similar, but I managed to fit 27AWG
and 33AWG into the build, with good HT margins.
Interlayer insulation was multilayer kapton film.

Used a more recent VPI varnish and VPI potting
compound.

This functioned in the circuit, but the long story
was that it would overheat in the long term -
giving the same operating symptoms as some aged
parts. I introduced a small fan to avoid this.
My original actually had an open cct HT winding,
so this wasn't an issue I'd run up against previously
and had made no note of the original's operating
temperature. I'd just assumed tektronix fan-free was
golden.

It's possible that the original gauge wire and
turns count might have run cooler, though the gap
would have been much larger on this core shape.
Slow overheating is an indication of excess core
loss, which has a strong positive tempco.


Re: Dark deposit on pins near leaking SMD electrolytic caps

 

On Wed, Feb 10, 2021 at 02:38 AM, greenboxmaven wrote:


I have restored some Sony video recorders that were loaded with the bad
condensers.
The affected Tek 'scopes use multilayer boards, making a slightly more intricate procedure advisable.

Raymond


Re: 465B strange ripple

Stephen
 

On Tue, Feb 9, 2021 at 01:30 PM, Jean-Paul wrote:

It also sounds like you have a ground issue, perhaps faulty mains earth.
How to I check/fix that??

Thank you


Re: Dark deposit on pins near leaking SMD electrolytic caps

greenboxmaven
 

I have restored some Sony video recorders that were loaded with the bad condensers. I made notes about ratings and placement, removed them all, and scrubbed the boards with hot soapy water. After a good rinse and drying, I re-tinned the spots where the condensers go, and repeated the wash. After that, installed the new condensers. I had complete success.

Bruce Gentry, KA2IVY

On 2/9/21 19:13, Ozan wrote:
Hello,
Does anyone know the chemical composition of the dark deposits on IC pins that are close to leaking SMD caps? What is the best way to clean them? Litmus paper shows base (hard to tell because it gets stained by the deposit). I couldn't find a good solvent for it.

Here is a picture from a TDS520A
https://groups.io/g/TekScopes/photo/260554/0?p=Name,,,20,1,0,0

Interestingly sometimes one or two pins are covered but neighboring pins are OK (maybe voltage at the pin making a difference?). I have seen this in CPU card of 2467B, both acquisition and CPU cards of TDS520 and TDS520A.
Ozan





Re: 465B strange ripple

Stephen
 

On Tue, Feb 9, 2021 at 01:30 PM, Jean-Paul wrote:


Stephen bonjour

Set the sweep hor 5 or 10 mS/ div, set trigger LINE

you will see if the symptoms are at a 100 Hz mains frequency

Then check every power supply DC voltage and rippling vs manual specifications


Most likely due to dried powered supply electrolytic caps, needs recapping.

It also sounds like you have a ground issue, perhaps faulty mains earth.

Bon Chance

Jon

Hi Jon,

First of all, thank you.
Now, all the voltages are ok within specs as per the manual.

This is what I see on the 110V TP at 5mV/Div - 5ms/Div - SOURCE LINE:

https://groups.io/g/TekScopes/photo/260052/1?p=Created,,,50,2,0,0

This is what I see on the same 110V TP at 10mV/Div - 20µs/Div - SOURCE. AC:

https://groups.io/g/TekScopes/photo/260052/0?p=Created,,,50,2,0,0


Re: 3T77 tunnel diodes (again)

 

After adventures in (mis)using my homemade extender cable (different thread), I FINALLY got back to working on the plug-in. D22 (unobtainable 1N3129 20 ma TD) just would not trigger no matter what, just sat there around .025 volts and wouldn't get much higher despite adjusting its bias (R21) all the way up. At one point the other TD (D25) fell out of its clip. The factory solder joints hadn't penetrated through the vias far enough and the clip had worked its way loose. Resoldered that. D25 then showed .057v and by tweaking its pot, could be seen to snap from low to high state... I swapped D22 for D42, the trigger regeneratorand it started merrily free-running, stops when I reduce the Trig Sens as intended, and triggers on my 114 pulse generator :)

So now I need to figure out a mod to use some other TD in place of D42. Seems easier than modifying the two-TD trigger circuit.

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