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Tek 464 - Advice on soldering shielding mesh to Vertical Output IC case


Fabio Trevisan
 

Hello Guys,
A couple of weeks ago, with the help of this forum, I came to conclude that
my 464's vertical output amplifier IC was defective (U464... part#
155-0115-00.)
I just got a new one and I`m about to install it the following days.
I`m usually confident in regards to soldering and normally I don't give it
second thoughts... but this IC takes a relatively "heavy" shielding mesh to
be soldered to its case... and I`m a bit shaky.
Do you have some advice?
Will it help to screw the IC to a heatsink so, at least its base and I
suppose its die will take longer to heat? (I think I'll do it anyway, just
in case).
Thanks for any tip?
BRgrds,
Fabio


 

None of my IC-VOA-equipped 465's has a tab soldered to its housing! At least try without it first!
The bolt underneath the IC is screwed into the chassis and takes care of grounding AFAIK. The circuit at the other side of your tab (no idea where it leads) may need grounding. If necessary, try and find another way of grounding before soldering.

Raymond


Fabio Trevisan
 

Thanks Raymond,

It's not really a tab, I didn't use well the word shielding..., it's a
copper braid, that connects to the mumetal shielding of the CRT.

Q service has one vertical amplifier output board for sale that has a
picture of the board that shows it... You can see at the link below...
http://www.qservice.tv/vpasp/shopexd.asp?id=8914

I thought that this was the "normal" way, as I've seen more than one
picture of this board on the net, and the copper braid is always there.

Rgrds,

Fabio

2017-03-27 19:02 GMT-03:00 hewpatek@gmail.com [TekScopes] <
TekScopes@yahoogroups.com>:



None of my IC-VOA-equipped 465's has a tab soldered to its housing! At
least try without it first!
The bolt underneath the IC is screwed into the chassis and takes care of
grounding AFAIK. The circuit at the other side of your tab (no idea where
it leads) may need grounding. If necessary, try and find another way of
grounding before soldering.

Raymond

[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]


 

Hi Fabio,
A braid as on the picture is exactly what I thought you meant but I used the wrong word.
Just checked 3(!) 465's, no braid! Maybe someone on this forum knows more. The braid may have been there to decrease HF noise but it certainly won't harm running your 'scope without it, see the result and temporarily press the braid against the VOA's case for comparison.

Raymond


 

I have an early 464 manual that shows a braid on the VOA, just across the device. I have two 466 manuals, one earlier and one later that also show the 464's(!) VOA. Neither shows a strap/braid.

Raymond


Vladimir _
 

Hi Fabio,

I have two 466s, an early and a late model, and both have the grounding strap soldered to the output amp if I remember correctly. However, I doubt it really matters as the hybrid has a low-impedance path to ground through the bolt on the bottom anyway. I personally wouldn't risk damaging the replacement unless absolutely necessary.


Szabolcs Szigeti
 

Hi,

I don't think this should be of any problem. The die itself is attached to the bottom of the IC, not the to of the case where you'll solder it. If you are worried, put the IC on some cooling, such as a wet sponge.
To solder the case, first scrape or sand the top and using a lot of flux. Then melt some solder on the case and you can solder the braid. It may sound strange, but use high power (but temperature controlled) iron. This will let you solder it quickly without heating the whole IC.

Szabolcs


 

The driver hybrid on the 7000 series vertical output amplifiers have a
pressed connection to the top of the metal can package which goes to
ground. It is held in place with a plastic clip instead of being
soldered into place. I am inclined to think Tektronix added these
because they could not rely on the ground connection through the heat
sink interface.

As far as soldering, the top of the metal can package is relatively
far from the circuits mounted to the base of the package so soldering
is relatively easy and safe assuming that the solder wets the surface.


 

For jobs like this, I use my largest soldering iron tip for its high
heat capacity. Soldering then takes just a second or two; the large
surface area transfers a lot of heat rapidly and the large heat
capacity means the temperature drop is small so there is no need to
wait for reheating.

The rubber/emery abrasive wheel from a Dremel is perfect for cleaning
the surface before soldering if necessary without scratching the whole
top. I do not know if they are still available but the white erasers
used for ink (the ones that tear up the paper) work well also.

If soldering is still difficult, then a tiny bit of dilute HCl acid
will help a lot but I doubt this will be necessary. Kester actually
makes some acidic surface cleaners (Copper Nu 5520, Nickel Nu 5530)
which work great as fluxes but good luck finding them.

On 28 Mar 2017 06:42:34 +0000, you wrote:

Hi,

I don't think this should be of any problem. The die itself is attached to the bottom of the IC, not the to of the case where you'll solder it. If you are worried, put the IC on some cooling, such as a wet sponge.
To solder the case, first scrape or sand the top and using a lot of flux. Then melt some solder on the case and you can solder the braid. It may sound strange, but use high power (but temperature controlled) iron. This will let you solder it quickly without heating the whole IC.

Szabolcs