Brian Roth
Well-known member
So it sounds like normal music, but through a 6 dB/octave high pass.....
I'll keep pondering.
Bri
I'll keep pondering.
Bri
More tape machine woes: crosstalk in sync only
- Thread starter EmilFrid
- Start date
Help Support GroupDIY Audio Forum:
@Brian Roth exactly like that! Thanks a lot, I'll do the same
Brian Roth
Well-known member
The manual I downloaded is frustrating.
I decided to begin with the tape heads and then follow the system wiring from there to the audio cards. Found the head block schematic but NOTHING from there to the audio cards....ie, the audio wiring harness.
Head block schemo shows just unshielded twisted pairs to connectors....very typical. Maybe Teac invented a wireless signal path....LOL!
Bri
I decided to begin with the tape heads and then follow the system wiring from there to the audio cards. Found the head block schematic but NOTHING from there to the audio cards....ie, the audio wiring harness.
Head block schemo shows just unshielded twisted pairs to connectors....very typical. Maybe Teac invented a wireless signal path....LOL!
Bri
Brian Roth
Well-known member
Have you measured resistance from the metal "body" of the heads to chassis ground?
I'm leery when measuring continuity around head wiring....I have my Han-D Mag at the ready to thoroughly demag the head components.
https://www.rbannis.com/Han-D-Mags.html
Bri
I'm leery when measuring continuity around head wiring....I have my Han-D Mag at the ready to thoroughly demag the head components.
https://www.rbannis.com/Han-D-Mags.html
Bri
Looking at the connector board schematic the heads connect there somewhere but I don’t see where on the board print layout diag - you’re right it’s weird. However if there was a broken ground track on this board either head connecting point or input socket ground you’d get leakage to adjacent cards via the LC across the input back to ground but you’d expect it to show on more than just the immediate neighbours - the level would maybe reduce as you progressed along the cards line ie. you’d expect more than just the directly adjacent cards to have leakage maybe with reduction due to each subsequent card damping the leakage?
juanito2008
Member
- Joined
- Feb 25, 2017
- Messages
- 11
I notice that the adjacent tracks have a huge level. More than +3VU
I'm not sure it shows you are in the specs or not as the magnetic field is huge during recording.
Can you do another test with only one adjacent track in record with a 0VU level.
And do a diagram crosstalk level vs frequency.
It will help to see if you are in the specs or not
As mentioned in previous posts this crosstalk issue arose only after installing a replacement record head and was not previously present, on refitting the originally removed head the problem remains.
I will do this, although I tried grounding the head body directly to circuit ground without success performance wise. But always good to have a look.
I don't really understand what this would show. I already know I'm way out of spec when it comes to crosstalk. Also none of the adjacent tracks are in record. It sounded like you thought both were?
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If each head channel cable is shielded to a common ground on the connector board and that ground was missing/broken you would get crosstalk on adjacent channels to the channel being recorded if the adjacent channels are in sync playback mode
@RoadrunnerOZ sounds good. I will check for shields. Will probably have time to do this tomorrow.
Got to be a common ground if this occurs on any channel
@RoadrunnerOZ yes, it happens on any channel that is right newt to a channel set to record. I fail to see how ut should be something other than a grounding issue, but I've had bigger surprises before, so best to investigate everything possible.
Good idea - look from the cables coming into the board as 0V lines at the print traces running to the record head cable shield grounds
@RoadrunnerOZ sounds good. I will do this. Looks like removing it fron the machine is somewhat of a PITA compared to dismantling the 85-16 but I will give it a try
First maybe unplug and replug all incoming and outgoing cables to the board the heads connect to unless you’ve already done that
@RoadrunnerOZ I've already done this, so I think I'll have to have a look at the board itself
To sum things up at the moment (mostly for my future self), it most likely has to do with the signal path from sync head to connector board (the board where head and amplifiers meet) and likely due to faulty ground connection. Any other possible culprits i should look for? I will definitely also look for cracks in the connector board.
Well there’s a common ground at the sync head connection at the board going back to wherever the ground is carried onto the board - there are two 0V connections on the connector board incoming from elsewhere from what I see, 1 for the top row of cards and one for the bottom row and one of these must supply the grounds to the sync head cable connector - so the break has to be on the board as each channel ground in the head cable is separate - they can’t all be faulty. It won’t be head casing ground as that would just induce hum in all channnels.
