Hybrid chips at SL611S

[kilmister]

Hi fellows.

I have few very noisy hybrid chips in SL611S channels. The chips are marked in the schem as T1, T3,T13 and T15. The chip it self has marking: 85501 C 0684 Does anyone know anything about them, schemos perhaps? It might be again time to DIY some spares...

Behaviour is a little starange, if I take chip out and re-insert it everything is good but after a while noise comes back. I measured around 4,5VDC from pin 8 at one chip which leads me to think chip is fried up to medium plus...

-Paavo

[pascal.verdet]

Hi,
It's preamp... No more information about them,
Please see on attached file.

Cheers,
Pascal

[waltzingbear]

if my memory is correct, its a balanced input module on a thin film substrate that is trimmed at manufacture for good CMMR, basically a 3 opamp instrumentation topology. Today it would be a BB INA134 or equivalent.

Alan

[kilmister]

Thanks for input.
It's something like I've thought. Asked from Keith a spare ones 20£ each... With that money should be possible to get a modern replacement. Looks like these parts will break at somepoint anyway.

Any is this blue coating removable someway?

-Paavo

[waltzingbear]

who cares? If you want to put in a new chip (not a bad idea), just follow the suggested circuit in the documentation with the one you choose and put it on a little board with pins in the right place. figure out how to use the existing gain pot and away you go. You could probably also eliminate the output coupling cap as they have very low dc offset. Keep the input caps as you never know what is going to be thrown at it.

Alan

[kilmister]

Exactly. Can't find any good reason why I shoudn't make console a bit better

When I compared 201 card to my G series schematic there wasn't caps C100 and 101 and it was allaround a bit different.
Anyone able post schematic from E manual pls?

-Paavo

[pascal.verdet]

Hi,

Your chip are 85502 & 85501 SSL Balanced Hybrid Chip

You can find these chips to http://store.solidstatelogic.com/catalog/50

Cheers
Pascal

[marcmozart]

These look familiar - same ones as on my 025 centre section card. (see below!)

Hi,

Your chip are 85502 & 85501 SSL Balanced Hybrid Chip

You can find these chips to http://store.solidstatelogic.com/catalog/50

Cheers
Pascal

[kilmister]

Your chip are 85502 & 85501 SSL Balanced Hybrid Chip

You can find these chips to http://store.solidstatelogic.com/catalog/50

Great, thanks!

-Paavo

[walrus]

Exactly. Can't find any good reason why I shoudn't make console a bit better

When I compared 201 card to my G series schematic there wasn't caps C100 and 101 and it was allaround a bit different.
Anyone able post schematic from E manual pls?

-Paavo

It's not a great original I have, but here it is.....

[kilmister]

Thank you Kevin!

[pascal.verdet]

Hi,

Mode detailled schema about 501 & 502
Cheers,
Pascal

[kilmister]

Cool, thanks!

[PMcC]

The hybrids are thick film circuits with resistors screen printed, and fired, directly on to the surface of the ceramic substrate. Look closely at those black rectangular areas and you should see thin cuts known as laser trimming a process carried out at point of manufacture that precisely adjusts the value of the resistors, great where matching is required, like in balanced input stages.

I would buy the replacements from SSL or where ever, that way you'll not run the risk of degraded common mode performance.

Pat