On my old Thorens HiFi deck the motor is driven by a dual op-amp w direct coupled bipolar amp output quadrature oscillator (Wien bridge followed by derivation stage). Input is 2x 12v AC and output on each wave is 6v into 27 Ohms.
It's broke.
I have the schematic, and can send it, but the parts are old eg op-amps are LM-3709C and trannies are 2N2218A/2N2914.
I think it's the semiconductors, because the unit kind of worked until I tweaked it!
Would someone be able to suggest drop in replacements for the Op-Amps and trannies (can replace resistors/caps if requ'd). These must be obtainable from Maplin or other on-line supplier preferably in the UK. I can get datasheets but don't have the knowledge to recalculate bias resistors etc. The other point is that the lamp is a spec which is no longer obtainable so the Wien gain adjusting pots may need to be replaced.
Thanks in antiicipation,
Quadrico
Bucks, UK
It's broke.
I have the schematic, and can send it, but the parts are old eg op-amps are LM-3709C and trannies are 2N2218A/2N2914.
I think it's the semiconductors, because the unit kind of worked until I tweaked it!
Would someone be able to suggest drop in replacements for the Op-Amps and trannies (can replace resistors/caps if requ'd). These must be obtainable from Maplin or other on-line supplier preferably in the UK. I can get datasheets but don't have the knowledge to recalculate bias resistors etc. The other point is that the lamp is a spec which is no longer obtainable so the Wien gain adjusting pots may need to be replaced.
Thanks in antiicipation,
Quadrico
Bucks, UK