More tape machine woes: crosstalk in sync only

[RoadrunnerOZ]

Ok cool

 

[EmilFrid]

Update: no cracks in the board, but I find no continuity between head shield and GND. Should I try tying some of them directly to circuit GND and see if the problem goes away? In that case I know where to look

Edit: never mind, with cards fitted there is continuity

 

[RoadrunnerOZ]

Update: no cracks in the board, but I find no continuity between head shield and GND. Should I try tying some of them directly to circuit GND and see if the problem goes away? In that case I know where to look

Edit: never mind, with cards fitted there is continuity

Record head ground on pin L of the record bias card is supposed to be tied to pins 6, 7, 8, F, H, J which are supposed to be connected to 0V - pin 19 of the power supply connection on the connector board - the 30V ground - one of the three 0V black cables connected to this board

 

[RoadrunnerOZ]

What about the Line In grounds?

 

[EmilFrid]

All grounds check out ok, and the board itself is fine. The mystery keeps on mystifying...

 

[RoadrunnerOZ]

All connections right back to the power supply at the power supply?

 

[EmilFrid]

Yessir! I followed every direction possible

 

[RoadrunnerOZ]

Maybe reflow all solder joins for incoming cabling, reinstall the board, reinstall all the cards and check for crosstalk - then if no change try removing card pairs (rec/bias and repro) one channel at a time and see if the problem persists and drops out with one pair out of circuit - bit tricky doing adjacents with a card pair missing but you get one adjacent at that location and you may find the problem is residing on a particular card or location with a card installed. If it does you can then eliminate if it’s the rec/bias or the repro card or if the location by swapping in cards from another channel.

 

[EmilFrid]

Thanks for the input. I will follow these steps and report back.

 

[EmilFrid]

Going to bed now so if I don't reply in this thread for 12 hours, I want you to know I haven't forsaken it.