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Hi coulomb So the chips I ordered are not suitable, no problem as long as I know before I fit one. Shall I get 7612 for when we need them? I am very new to in depth electronics so you will have to be gentle with me! I am not understanding which resistance your asking me to check and also...

Just a thought How about we adjust the input voltage by changing the wiggly row of resistors

Yes this is the new board and input voltage is 4.00 and output is 3.75 the voltage supplies are bench supplies and probably not the best. But best I have got! the 15v supply is rated at 100 amps so a little out of its range on this job!!!!!!!!

Is there anything more that can be done this evening? Or do we wait until I replace the op amp

looking at the input voltage below, its not very clean?!

b and c above a and d above maybe a better one of - side below

hows that!

https://imgur.com/a/iKlMIPB

Thanks kenny cool pictures I will have to get the scope now, I dont use it very often so you will have to bear with me! do you have to pay to post pictures directly to the forum

sorry my fault, still had a supply connected but not powered

just going over old ground the resistance on my new board between vh and the pin on the op amp is 6k??? not 100k my old board is 100k but i replaced this resistor with one you suggested kenny? is this why my old board is now reading less?

Ac voltage test A and d 3.009v B and c 2.775v All ac and - to vl

50v ac Just another test I have done Is to apply 30v dc to pin 1 of cn4 as it’s as much as my supply will do! Tracing it through the wiggly row of resistors it drops about 5v on each until hv and it is then 315mv on the input The output on pin 3 is 301mv

Next tests Input 4.00v on vl vh with hybrid board still fitted to main board Input on pins 4 and 5 15.00v Voltage across vl too: B and c -0.457 Op amp output -4.01 Lv- -7.65 A and d 1.3mv Lv+ 7.09v

That was all over my head your last post! I have ordered a handful of op amps to test I will do the other test, I have emailed you a picture of a supply. EDIT I have ordered: Standard Items Ordered Reference: 163665140 ICL7611DCBAZ Renesas Electronics, Op Amp, 1.4MHz, 3 → 15 V, 8-Pin...

I have replaced the tl494 but none of the components around it My original board is showing a vast difference now between input and output nearly half a volt. This could be as some replacement components may not have been the correct value or that the board is degrading with so much heat...

Hi Which one in this selection there seems to be two of the same but different makes? https://uk.rs-online.com/mobile/search.html?searchTerm=ICL7612DCBAZ Obviously I only want 5! Or a small quantity. Thanks Edit…. ICL7611DCBAZ Intersil, Op Amp, 1.4MHz, 3 → 15 V, 8-Pin SOIC This is the...

The two filter caps are 1uf The three resistances you wanted checked are perfect Next tests Input 4.00v on vl vh with hybrid board still fitted to main board Voltage across vl too: B and c 0.65v fluctuating slightly Op amp output 1.112v Lv- 373mv A and d 0.003mv Lv+ 0.789v These...

I am just looking at the RS components website There are thousands of op amps! There are 2110 8 pin surface mount How do we round down any suitable, this is a little over my head but willing to learn….

Morning kenny, A very interesting bit of reading on your last two posts, I had to read it all twice to digest it. I had replaced the op amp on the original board with the one specified but it never worked even though it was new but has the over voltage degraded other components on the board...