Hi there!
Im trying to service an old Harman&Kardon tape deck (TD470) player, which after being put away for many years, is now lacking sound randomly (first time I tried it worked, called the owner and said it wasn't working for him, tried again myself and sound was gone)
This intermitent issue led to to go straight to the PS & Caps...I found at least one voltage missing (sorry now I can't remember which one), and one of the 3 fuses in the PS was open (this is strange as an intermitent failure wouldn't relate to a blown fuse).
First thing I suspected was the capacitors but they all seem in very good condition. Then I found the schematic and Im having trouble to understand some parts of it, specially the -24v section (lower part of the schematic), and the p.mute in which Im totally lost on what it does and where it takes power from....
Can you help me understand how these 2 sections work?
Also why do f1 and f2 carry alternating current directly to the electronics?. What's their function? That transformer output puts out 5v ac.
Im attaching the original schematic and also another one modified by me which is how I believe it should be, as there are non-clear crossings/connections that lead me to error
Thanks in advance!
Im trying to service an old Harman&Kardon tape deck (TD470) player, which after being put away for many years, is now lacking sound randomly (first time I tried it worked, called the owner and said it wasn't working for him, tried again myself and sound was gone)
This intermitent issue led to to go straight to the PS & Caps...I found at least one voltage missing (sorry now I can't remember which one), and one of the 3 fuses in the PS was open (this is strange as an intermitent failure wouldn't relate to a blown fuse).
First thing I suspected was the capacitors but they all seem in very good condition. Then I found the schematic and Im having trouble to understand some parts of it, specially the -24v section (lower part of the schematic), and the p.mute in which Im totally lost on what it does and where it takes power from....
Can you help me understand how these 2 sections work?
Also why do f1 and f2 carry alternating current directly to the electronics?. What's their function? That transformer output puts out 5v ac.
Im attaching the original schematic and also another one modified by me which is how I believe it should be, as there are non-clear crossings/connections that lead me to error
Thanks in advance!
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