Sansui SC-1110 Fast forward problem

[Dom123]

I just recently bought a set of equipment comprising a non working AU-517, TU-717 & SC-1110.
Repaired & recapped the AU-517 as per the restoration thread on Audiokarma & got the TU-717 working. These two are working really well. The AU-517 is sounding great.

Turning my attention to the SC-1110. I know it's a bit BOTL, but it looks really smart. After some lubrication, a new drive belt & a good clean, it kind of works. Reverse wind is OK, play is OK, although there is a slight tendency to slowly speed up & slowly decrease in repeated cycles, but the main issue is with the fast forward.

Pressing fast forward, it only works for 2 seconds or so before the solenoid kicks in and stops it.
This corresponds to the function "Lead-in". I just can't get it to fast forward normally. The solenoid for stop, kicks in straight away.

However, if the "Lead in" button is pressed and held in, the fast forward works at at decent speed.
I am struggling to fix it. I have checked every single resistor, transistor & cap on the G-1230 board (Lead-in and Shut-off circuit Board) and can't find anything wrong. I changed the electrolytics just for good mesure but to no avail.

Has anyone ever come across this issue before on an SC-1110 ?

 

[fastcooler]

Hello @Dom123 , I have same exact issue with my SC-3110 and I just posted a new thread.

https://audiokarma.org/forums/index.php?threads/sansui-sc-3110-fast-forward-problem.1032288/

Did you finally solved this issue?

Thanks

 

[penmarker]

Hi you two. have you found the solution for this? i had the same issue with a SC-1110 and i solved it last night and my issue was similar - FF works for 2 seconds then stops, pressing lead in allows FF to keep running.

small diagnosis before we know if its the same root cause. Remove one leg from resistor R603 on the G-1230 Lead-in and Shut-off Circuit Board and measure the voltage from left pin of the board connector (the one below brown cable) that connects to R603.




That pin is now floating and it should have zero voltage or anywhere below 1V. Pressing lead in switch will connect it to the 15V rail.
If there's voltage presents then that means there's a leakage from the 15V rail to R603 and in turn charges the capacitor that engages the solenoid.
The leakage is most likely this lead in switch. Testing continuity or resistance will show correct reading but it leaks at 15V.



Solution is simple. either Desolder the legs of the switch or connect the pin that goes to R603 to ground with 1k resistor. Use 1W.



I've disassembled the switch and cleaned thoroughly, cleaned the traces with alcohol, made sure no flux is bridging or any other cause of current leak but the only thing that keeps leaking was that switch. the 1k resistor safely drains the current leakage but it is high enough to allow the lead in circuit to work when pressed.

 

[Dom123]

Hello @Dom123 , I have same exact issue with my SC-3110 and I just posted a new thread.

https://audiokarma.org/forums/index.php?threads/sansui-sc-3110-fast-forward-problem.1032288/

Did you finally solved this issue?

Thanks

Sorry since sold it. Never did fix it. It's a shame the solution of pemmarker wasn't on the forum at that time !

 

[penmarker]

Sorry since sold it. Never did fix it. It's a shame the solution of pemmarker wasn't on the forum at that time !

Yeah it stumped me for a long while. Then I realised the voltages on the transistors were correct but collector was wrong. I took out the resistor from the circuit and the connector still had 15V, which was bizarre since the switch is not pressed. traced the traces multiple times to see if there are any sources for the voltage but none. Took out the switch and it behaved ok, voltage was no longer present at the resistor. soldered the switch back in and it happened again. the phenolic material for the top cover of the switch must've started to cause current leak between the pins.