It's worth trying. I always treat everyone as stupid. I start with myself. From your photo you have done the right things.
I often find I have made a stupid mistake. Our mutual friend Martina told me off gently for forgetting to ground the circuit I made for her. To be honest some time had gone by and I had to think. Then as I said to Martina " It's a prototype and as yet I didn't know where best to put the ground ". In fact it was ideal where it was easiest to fix it. It was a horrible moment thinking I had been really stupid.The circuit is very good. It is passive with relays as it makes building it foolproof. The original circuit is one of my mad ideas ( that works ) that even I don't understand. That's not a joke. I have no idea how I did it. Hours of experimenting and finding I could repeat the circuit.
I often find I have made a stupid mistake. Our mutual friend Martina told me off gently for forgetting to ground the circuit I made for her. To be honest some time had gone by and I had to think. Then as I said to Martina " It's a prototype and as yet I didn't know where best to put the ground ". In fact it was ideal where it was easiest to fix it. It was a horrible moment thinking I had been really stupid.The circuit is very good. It is passive with relays as it makes building it foolproof. The original circuit is one of my mad ideas ( that works ) that even I don't understand. That's not a joke. I have no idea how I did it. Hours of experimenting and finding I could repeat the circuit.
That was the Servo of the Primal Scream phonostage.
It played for half an hour and then it went off on both channels at the same time, precisely like a clock.
It has a differential servo and I forgot a ground connection.
I needed month to find the problem.
Actually Jonathan Carr had the idea to check the servo and there it was.
Still wondering why it worked in the first place.
It played for half an hour and then it went off on both channels at the same time, precisely like a clock.
It has a differential servo and I forgot a ground connection.
I needed month to find the problem.
Actually Jonathan Carr had the idea to check the servo and there it was.
Still wondering why it worked in the first place.
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Greetings from beyond the grave. The Bonsai post was a little disconcerting, but no, I'm still around. There was a post on another thread saying I was at Manchester University, which is equally wrong. I'm just retired. I never needed a MC preamp and so never bothered to build the circuit. I know Dimitri tried it, but with a servo, and possibly used the circuit in a commercial design, but anyway I don't see anything obviously wrong with this version. I would worry slightly about those complementary feedback pairs in the supplies, maybe try removing the 1000uF capacitors, or the idea to try with batteries may narrow down the problem.
[emoji1787][emoji1787][emoji1787] sweet mother Mary, he is resurrected!!!
Hi Mike ! I am happy to see you here. I will give my best to make it work. I build the PSU though without problems several times.
Hi Joachim, It isn't very clear to me from your diagram which op-amp you used, it looks like OP1641, which I can not find listed anywhere. Is it an OPA1641, which looks good, or an OPA641 which is not unity-gain stable and has an extreme gain-bandwidth and could be a problem. Apart from that I don't have any good ideas what to try changing.
Ok, thanks, the OPA1641 looks like a good choice. It could be worth trying a lower resistor from opamp inverting input to earth,maybe reduced from 47R to 22R to reduce loop gain and see if that improves anything, but I still don't see anything obviously wrong with the circuit.
Jesus. I am really sorry. I mistook you for someone else.
Apologies again.
Peace
Hi Bonsai, no problem, I guessed you had mixed me up with someone else. I'm approaching my 70th birthday soon, but still in good health so I hope to be around for another decade or two.
That’s great Mike ! 63 last December my side and also hoping I get another 2 decades of good health!
if you go to batteries -- new fully charged NiCd -- good luck finding them (readily available over here.)