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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
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6th Mar 2022, 1:09 pm | #21 |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: Magnecord Bias Oscillator voltage
Thank you... I did order another set of 12BH7 as I dont have these. I did try and swapped with a 12au7 with no better results, but maybe the 12au7 is not suitable here.. the preamp section at the "recorder" socket is giving a superb signal quality. The problem seems to be somewhere at the transport and the bias circuit. I will update here when the new 12bh7 is here. I really hope thats the problem and not something more serious.
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6th Mar 2022, 1:56 pm | #22 |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: Magnecord Bias Oscillator voltage
..hmm one more thing made me thinking. The wiring coming from the playback head. I have an XLR however, I only see two connections inside that male XLR coming from the playback head. Pin2 is the signal ( a copper wire) and pin1 is the shield. pin3 has nothing.
The XLR socket p106 on the wiring diagram attached seems to be different. I dont know to be honest how to read those circles at the pin 2...i think something might be wrong here... |
6th Mar 2022, 2:39 pm | #23 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Magnecord Bias Oscillator voltage
The dotted circles represent the cables screen (the outer shield braid)
Lawrence. |
6th Mar 2022, 2:48 pm | #24 |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: Magnecord Bias Oscillator voltage
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6th Mar 2022, 3:03 pm | #25 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Magnecord Bias Oscillator voltage
Quote:
I can't find any reference to a PT75A on the internet except for what's in this thread. Lawrence. |
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6th Mar 2022, 3:17 pm | #26 |
Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: Magnecord Bias Oscillator voltage
Thanks Lawrence, appreciate that you did try and looked this up. Yes, it seems to be a rare ish model, or not so common. So basically from the playback head there is an xlr coming out with two pins. What I had is pin 1 and pin 2 connected to the playback head. (no shield). This XLR cable is not original, someone changed this. Maybe I am completely wrong but the pin1 is wrong..this should may be pin3 instead...as pin 1 "normally" the shield...maybe someone did this wrong, I don't know... i am just trying possibilities here.
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