Hello,
I am trying to repair a non working Seeburg Bandshell,
it will not start scanning after a selection is made.
Manually starting the scan with the switch is working and the selected record(s) are played so that works fine.
Things I already did:
Replaced the black box with the Magic Box
Replaced the Grey box
Recapped the DCC
Replaced the transistors and the diodes on the scan board. (2N3906 and 1N4158)
Voltages on the test strip of the DCC:
- 25,49v (-27v)
- 13,23v (-13v)
+ 25,52v (+27v)
When a selection is made (like 111) a scan pulse is visible on the scope, coming from pin12 of the grey box and arriving at pin2 of the scanboard in the DCC.
Pin 6 of the scan board is correctly connected to the scan start coil. It measures 25volts AC. When the manual scan switch is used it drops to zero and the coil is activated.
Attached picture shows voltages on the scanboard when a selection is made
Yellow: scanpulse arriving on pin 2
Blue: collector of transistor Q3119
Purple: (elevated to not overlap blue) anode side of diode Q3131
Questions:
Are the curves / voltages of the pulses shown the screenshot of my scope correct?
What could be the issue of the Thyristor / Triac not getting the pulse to pull pin 6 to ground and thus activating the scan coil?
Help is very much appreciated!
By the way: the original grey box gives exactly the same patterns and voltages