Electronics > Repair
roland 808 drum machine u.s power conversion
cod65:
--- Quote from: CaptDon on January 06, 2025, 02:14:51 pm ---First off, the 240 volt unit only draws half as much line current as the 120 volt model. Basic first day Power/Ohms law knowledge that is why the fuses are different. Second, there is no doubt the Roland 808 DID NOT use an 'off-the-shelf' transformer. It is certainly a custom designed part. IF indeed they used resistors instead of fuses then they MUST be flameproof!!! Buy or build an external 120vac in 240vac out 'transformer in a box' for your friend. That Roland unit is around 50 watts (actually less) and one solution may be to find a 50va rated transformer with dual primaries (120 / 120). The secondary windings are typically 12 / 12. Ignore the secondaries, we won't use those. Wire the primaries in series observing the proper phase relationship. Feed 120 from one end and the center point and get 240 across the far ends of the two primary windings in series. This may be way beyond the safe area of your current skill set?
--- End quote ---
Thank you Capt Don for your time/ knowledge. Sorry I wasn't clear - as explained in other replies- I get why the primary fuse would double in value , but the secondaries made no sense to me- 20 volts either way, the load is the same. I got a good explanation above.
also should've mentioned earlier on that the original transformer is long gone and I included pic of current config with (2) 230vac providing the 10vac and 23-0-23 I wish to replace.
DimitriP:
--- Quote ---As I mention above this does not have the original transformer but 2 modern 230vac tformers currently
--- End quote ---
"RS-Pro" no less :)
RS PRO 6VA 2 Output Chassis Mounting Transformer, 9V ac, IEC 61558-2-6
https://docs.rs-online.com/cd7c/A700000008857656.pdf
RS PRO 6VA 2 Output Chassis Mounting Transformer, 20V ac, IEC 61558-2-6
https://docs.rs-online.com/9099/A700000008857672.pdf
one has two secondary 9V windings 3VA each, the other has two secondary windings 20V 3VA each ..
It's right there on the label...
and I forgot what the original question was ....
(fixed quoted message)
cod65:
--- Quote from: Swake on January 07, 2025, 08:40:10 am ---
From the schematic you posted there does not seem to be a 50 Hz or 60 Hz clock pickup, only DC voltages.
--- End quote ---
thank you Swake- can you elaborate on this last sentence a bit ?
Swake:
Someone mentioned that some audio devices from that era use the 50 or 60 Hz Hz clock to tune sounds.
This device does not seem to do this as there is no pick-up of that 50 Hz (or 60 Hz) signal.
Swake:
The 115V equivalent of the 9V 6VA transformer at RS is RS-stocknr.: 503-990, see datasheet attached
There is no equivalent for the 20 V version. There is a 24 V but that is probably a little too much (would have to check datasheets of the TA7179P, but anyhow you don't want to stress that one as it is old and probably unobtainium). The 15V is going to be too low.
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