Hi,
I've my just bought 3 Roland RE-201s on the bench for restoration.
2 of them are nearly finished, they self-oscillate too etc.
But the 3rd have [at least] a problem.
I've tracked down it to the missing 60Khz signal outside of the bias oscillator circuit [-> pin 54 of the psupply board],
so the erase head do nothing.
On the working 201s, the 60 Khz signal at pin 54 is around 45V as per specs, on this one is around 700mV.
On the oscillator side of L23 coil, both working and defective 201 have around 2V at respectively [correct] 60Khz and [wrong] 72Khz,
exactly the same waveform on both units.
So, I'm pushing myself to assume that all the other components of the bias-oscillator are more or less ok and that its the coil the culprit.
I've measured with an ohmeter the resistance [onboard] of the external wiring of the coil, and the perhaps defective one
gives 13 Ohm instead of 2.6 Ohm of the one in the healty 201.
Part number is listed as MC-126-2133B on schematics, and in the units they're marked as 14S2133B.
I've not found their datasheet so far.
Someone have clues?
Thanks!
P.S. here is the schematic:
http://www.omegav.ntnu.no/~karlto/space_echo/page9.png
I've my just bought 3 Roland RE-201s on the bench for restoration.
2 of them are nearly finished, they self-oscillate too etc.
But the 3rd have [at least] a problem.
I've tracked down it to the missing 60Khz signal outside of the bias oscillator circuit [-> pin 54 of the psupply board],
so the erase head do nothing.
On the working 201s, the 60 Khz signal at pin 54 is around 45V as per specs, on this one is around 700mV.
On the oscillator side of L23 coil, both working and defective 201 have around 2V at respectively [correct] 60Khz and [wrong] 72Khz,
exactly the same waveform on both units.
So, I'm pushing myself to assume that all the other components of the bias-oscillator are more or less ok and that its the coil the culprit.
I've measured with an ohmeter the resistance [onboard] of the external wiring of the coil, and the perhaps defective one
gives 13 Ohm instead of 2.6 Ohm of the one in the healty 201.
Part number is listed as MC-126-2133B on schematics, and in the units they're marked as 14S2133B.
I've not found their datasheet so far.
Someone have clues?
Thanks!
P.S. here is the schematic:
http://www.omegav.ntnu.no/~karlto/space_echo/page9.png