C420 should sit at about +13.5 V anyway.
Hi Ren¨¦,
I measured C420 voltage. To my surprise it was +9.0 V. So I was very wrong with that +13.5 V. The mistake is I thought that +9 V would be present at the inputs of U430.
I also did waveform measurements but though the display works fine there seems to be some fast 2 level oscillation present, both in the triangular parts and in the output of U470. Never mind, you can swim already in the pictures provided by Michael.
Albert
On Sat, May 8, 2021 at 10:46 PM, Albert Otten wrote:
Hi Ren¨¦,
It seems that Q440 never supplies a reference current to U460/2. C420 should
sit at about +13.5 V anyway. Between centre and CW your U400/1 will be steady
High since U470/7 is negative. For Q440 to conduct U400/2 must also be High. I
guess between centre and CW the state of Q400C&D is steady with pin 8 High.
That's because pulses at pin 13 are missing but pulses at pin 4 still arrive
at each "200" event of the counter. Then Q440-c should be at about +13 V
(somewhat increasing in the CW direction). Am I correct and does this (not)
happen?
(BTW: Earlier you mentioned + 6.5 for Q535-b while Q535-e is grounded. That
will be a mistake.)
Albert ,
