Geloso Preamp

[guidoilieff]

Hi. A friend of mine gave me a Geloso 541 tape recorder to repair. This thing was used in the 60' to distort guitars because there was nothing else available for small bands/studios.


The problem with this thing is that when the motor is spinning it makes hum+noise+distortion in the signal and you can barely hear what you recorded on tape.



I replaced the motor ceramic capacitor with a 472 polyester and the noise is still there.


Do you have any "shoot from the hip" recommendations to try?

Here is the original user/repair manual (page 17) http://www.fracassi.net/iw2ntf/manuali/Bollettini%20Tecnici%20Geloso/Bo101.pdf

Thanks!

[anotherjim]

I list some of usual...

Check correct AC power voltage selection. Check (if 3 pin) AC cord safety ground continuity to chassis.

Head treatment. De-gauss the heads. Clean the heads. Adjust head azimuth.
I guess there may be some cheap/primitive machines with fixed head mounting that can't be adjusted, in which case ignore azimuth.
Azimuth really needs a pre-recorded test tape and heads mounted with some kind of sprung adjust screw. The screw head should have some sealing paint on it. Nail varnish commonly used for the paint.
Now the head adjust may have been badly messed with in the past and you are unlikely to find a proper test tape to set it up. So limit the job to adjusting the tilt of the playback heads for best tone from recorded tape.

Bias oscillator - T4? Should be about 19kHz at collector?

Check grounding -  look out for any wire lugs screwed to metal chassis parts and the power transformer frame. Clean & tight.

Electrolytic capacitors on power supplies - replace.