Surf pi pro unusual behaviour

[nonkapo]

Good evening all,
Just went to the post to get my DSO(The hantek two channel will come later). So with this one i have single 1x probe. Is it safe to use it on the surf or i need 10x or more? I wait way too long for it to just burn it from first attempt:-). Gues around the Fet is the only dangerous place but anyway? Thanks in advance.

[qute1]

Cheer nonkapo i will give it a go.

[nonkapo]

Surf PI to Surf PI PRO mods

Here are all the files i have in regards to the Surf PI to PI Pro modifications.


Surf_PIMOD.txt

All credits for the above files go to Tepco , Quiazoschi, dbanner and Dennis. Esquse me if i miss someone.

Thanks

[qute1]

Yeah it would be cool to have the information all in one place please, i am sure others here would appreciate you efforts also as although the search engine can be good with practice i still find the interface a little hit and miss i.e. still cannot get it to display the relevant pages of a threads it just comes back with the whole thread and doesn't tell you what page your hit might be on.

[nonkapo]

Yeah, i dig the forum nicely as this topic was interesting to me. It is something everyone talk about but the info is spread all over the forum. I can post here, however if you need i can also send to you to save you from few days searching. The main problem is i have no osciloscope and simple replacing of the components may work or may not. One for sure need to adjust after. For example,somewhere i've seing 470nf replaced with 220 as on the schematic. Somewhere they are replaced with 330nf. Which one is suitable in my case i cant say only by experiments.

[qute1]

Do you have details of the surfpi to pro conversion? i have a couple of surfpi also that i am thinking of putting basic VCO on but may upgrade at the same time!

[nonkapo]

Mhm, thanks will try that and post a short movie to show you am I on the proper track. I have that feeling interference is way too big and response not exactly as it should be.

[qute1]

that should work tolerance on polyester caps would put it in that range any how.

[Andi68]

2x 470nF parlel =960nF- try it

[nonkapo]

I've done the surf PI to PI Pro conversion, but cause i have no 1uF for C7 avaiable i keep the old value of 470n cap. Is it critical (especially as the gain increases) or i can carry on like this, or may be two 470nF parralel aregood idea?
Thanks.

[Andi68]

Thx Carl and kt

[Carl-NC]

Glad you got it figured out.

What is the function of the SAT cap? Is he necessary?

It stabilizes the detector to slow variations in signal due to circuit drift. Without it, the whole circuit is DC-coupled, but there is so much overall gain that it will be extremely difficult to keep tuned correctly.

[qute1]

Sorted thanks again guys once i removed and replaced c7 and no joy i tried shorting across gain sens pot and there it was a second crap pot in this kit replaced with a nice quality one and she is running bootiful very good on airtest anyhow gets a thin gold ring at 7" solidly on low delay.
Again thanks to you all, KT315 and carl-nc especially, sometimes you just can't see the wood for the trees and it takes some experienced advice to know just where to chop.......

[kt315]

What is the function of the SAT cap?

Is he necessary?

it 'adds' a property of non-motion/static diagram to motion diagram.

[qute1]

Appears to be some sort of feedthrough cap connecting one amp of 5534 to the other i will update when i have had a chance to fondle it.